title: Disruptive innovation

text: In the practical world, the popularization of personal computers illustrates how knowledge contributes to the ongoing technology innovation. The original centralized concept (one computer, many persons) is a knowledge-defying idea of the prehistory of computing, and its inadequacies and failures have become clearly apparent. The era of personal computing brought powerful computers "on every desk" (one person, one computer). This short transitional period was necessary for getting used to the new computing environment, but was inadequate from the vantage point of producing knowledge. Adequate knowledge creation and management come mainly from networking and distributed computing (one person, many computers). Each person's computer must form an access point to the entire computing landscape or ecology through the Internet of other computers, databases, and mainframes, as well as production, distribution, and retailing facilities, and the like. For the first time, technology empowers individuals rather than external hierarchies. It transfers influence and power where it optimally belongs: at the loci of the useful knowledge. Even though hierarchies and bureaucracies do not innovate, free and empowered individuals do; knowledge, innovation, spontaneity, and self-reliance are becoming increasingly valued and promoted.


title: Disruptive innovation

text: Uber is not an example of disruption because it did not originate in a low-end or new market footholds. One of the conditions for the business to be considered disruptive according to Clayton M. Christensen is that the business should originate on a) low-end or b) new-market footholds. Instead, Uber was launched in San Francisco, a large urban city with an established taxi service and did not target low-end customers or created a new market (from the consumer perspective). In contrast, UberSELECT, an option that provides luxurious cars such as limousine at a discounted price, is an example of disruption innovation because it originates from low-end customers segment - customers who would not have entered the traditional luxurious market.


title: History of calendars

text: The history of calendars, that is, of people creating and using methods for keeping track of days and larger divisions of time, covers a practice with ancient roots.


title: History of calendars

text: Archeologists have reconstructed methods of timekeeping that go back to prehistoric times at least as old as the Neolithic. The natural units for timekeeping used by most historical societies are the day, the solar year and the lunation. Calendars are explicit schemes used for timekeeping. The first historically attested and formulized calendars date to the Bronze Age, dependent on the development of writing in the ancient Near East. The Sumerian calendar was the earliest, followed by the Egyptian, Assyrian and Elamite calendars.


title: History of calendars

text: The Vikram Samvat has been used by Hindus and Sikhs. One of several regional Hindu calendars in use on the Indian subcontinent, it is based on twelve synodic lunar months and 365 solar days.The lunar year begins with the new moon of the month of Chaitra.This day, known as Chaitra Sukhladi, is a restricted (optional) holiday in India.


title: History of calendars

text: A number of ancient and medieval inscriptions used the Vikram Samvat. Although it was reportedly named after the legendary king Vikramaditya, Samvatsara in short ‘Samvat ’is a Sanskrit term for ‘year’. Emperor Vikramaditya of Ujjain started Vikram Samvat in 57 BC and it is believed that this calendar follows his victory over the Saka in 56 B.C.


title: History of calendars

text: A larger number of calendar systems of the ancient Near East appear in the Iron Age archaeological record, based on the Assyrian and Babylonian calendars. This includes the calendar of the Persian Empire, which in turn gave rise to the Zoroastrian calendar as well as the Hebrew calendar.


title: History of calendars

text: Calendars in antiquity were usually lunisolar, depending on the introduction of intercalary months to align the solar and the lunar years. This was mostly based on observation, but there may have been early attempts to model the pattern of intercalation algorithmically, as evidenced in the fragmentary 2nd-century Coligny calendar. Nevertheless, the Roman calendar contained very ancient remnants of a pre-Etruscan 10-month solar year.


title: History of calendars

text: The Roman calendar was reformed by Julius Caesar in 45 BC. The Julian calendar was no longer dependent on the observation of the new moon but simply followed an algorithm of introducing a leap day every four years. This created a dissociation of the calendar month from the lunation.


title: History of calendars

text: In the 11th century in Persia, a calendar reform led by Khayyam was announced in 1079, when the length of the year was measured as 365.24219858156 days. Given that the length of the year is changing in the sixth decimal place over a person's lifetime, this is outstandingly accurate. For comparison the length of the year at the end of the 19th century was 365.242196 days, while today (1999) it is 365.242190 days.


title: History of calendars

text: The Gregorian calendar was introduced as a refinement of the Julian calendar in 1582, and is today in worldwide use as the ""de facto"" calendar for secular purposes.


title: History of calendars

text: The term "calendars" itself is taken from the "calends", the term for the first day of the month in the Roman calendar, related to the verb "to call out", referring to the calling or the announcement that the new moon was just seen. Latin meant "account book, register", as accounts were settled and debts were collected on the calends of each month.


title: History of calendars

text: The Latin term was adopted in Old French as and from there into Middle English as by the 13th century. The spelling "calendar" is from Early Modern English.


title: History of calendars

text: An alternative hypothesis connects "calendar" with "koledari" in Slavic, pre-Christian tradition, which was later incorporated into Christmas. "Kolo" means "circle, cycle" and "dar" means "a gift".


title: History of calendars

text: A number of prehistoric structures have been proposed as having had the purpose of timekeeping (typically keeping track of the course of the solar year). This includes many megalithic structures, and reconstructed arrangements going back far into the Neolithic period.


title: History of calendars

text: In Victoria, Australia, a Wurdi Youang stone arrangement could date back more than 11,000 years. This estimate is based on the inaccuracy of the calendar, which is consistent with how the Earth's supposed orbit is thought to have changed during that time. The site is found near the world's oldest known site of permanent aquaculture.


title: History of calendars

text: A ceramic artefact from Bulgaria, known as the Slatino furnace model, dated to roughly 5,000 BC, has been pronounced by local archaeologists and media to be the oldest known calendar representation, a claim not endorsed in mainstream views.


title: History of calendars

text: A mesolithic arrangement of twelve pits and an arc found in Warren Field, Aberdeenshire, Scotland, dated to roughly 8,000 BC, has been described as a lunar calendar and was dubbed the "world's oldest known calendar" in 2013.


title: History of calendars

text: The Vučedol culture archeological findings in Vinkovci in modern-day Croatia included a ceramic vessel dated to 2,600 BC bearing inscribed ideograms of celestial objects, that was interpreted as an astral calendar, the oldest one in Europe that shows the year starting at the dusk of the first day of spring.


title: History of calendars

text: The ancient Sumerian calendar, roughly dated to 2,100 BC, divided a year into 12 lunar months of 29 or 30 days. Each month began with the sighting of a new moon. Sumerian months had no uniform name throughout Sumer because of the religious diversity. This resulted in scribes and scholars referring to them as "the first month", "the fifth month", etc. To keep the lunar year of 354 days in step with the solar year of 365.242 days an extra month was added periodically, much like a Gregorian leap year. There were no weeks in the Sumerian calendar. Holy days and time off from work were usually celebrated on the first, seventh and fifteenth of each month. In addition to these holy days, there were also feast days which varied from city to city.


title: History of calendars

text: Although the earliest evidence of Iranian calendrical traditions is from the second millennium BC, predating the appearance of the Iranian prophet Zoroaster, the first fully preserved calendar is that of the Achaemenids. Throughout recorded history, Persians have been keen on the idea and importance of having a calendar. They were among the first cultures to use a solar calendar and have long favoured a solar over lunar and lunisolar approaches. The sun has always been a symbol in Iranian culture and is closely related to the folklore regarding Cyrus the Great.


title: History of calendars

text: Old Persian inscriptions and tablets indicate that early Iranians used a 360-day calendar based on the solar observation directly and modified for their beliefs. Days were not named. The months had two or three divisions depending on the phase of the moon. Twelve months of 30 days were named for festivals or activities of the pastoral year. A 13th month was added every six years to keep the calendar synchronized with the seasons.


title: History of calendars

text: The first calendars based on Zoroastrian cosmology appeared in the later Achaemenid period (650 to 330 BC). They evolved over the centuries, but month names changed little until now.


title: History of calendars

text: The unified Achaemenid Empire required a distinctive Iranian calendar, and one was devised in Egyptian tradition, with 12 months of 30 days, each dedicated to a yazata (Eyzad), and four divisions resembling the Semitic week. Four days per month were dedicated to Ahura Mazda and seven were named after the six Amesha Spentas. Thirteen days were named after Fire, Water, Sun, Moon, Tiri and Geush Urvan (the soul of all animals), Mithra, Sraosha (Soroush, yazata of prayer), Rashnu (the Judge), Fravashi, Bahram (yazata of victory), Raman (Ramesh meaning peace), and Vata, the divinity of the wind. Three were dedicated to the female divinities, Daena (yazata of religion and personified conscious), Ashi (yazata of fortune) and Arshtat (justice). The remaining four were dedicated to Asman (lord of sky or Heaven), Zam (earth), Manthra Spenta (the Bounteous Sacred Word) and Anaghra Raocha (the 'Endless Light' of paradise).


title: History of calendars

text: The Parthians (Arsacid dynasty) adopted the same calendar system with minor modifications, and dated their era from 248 BC, the date they succeeded the Seleucids. Their names for the months and days are Parthian equivalents of the Avestan ones used previously, differing slightly from the Middle Persian names used by the Sassanians. For example, in Achaemenid times the modern Persian month 'Day' was called "Dadvah" (Creator), in Parthian it was "Datush", and the Sassanians named it "Dadv/Dai" ("Dadar" in Pahlavi).


title: History of calendars

text: When in April of AD 224 the Parthian dynasty fell and was replaced by the Sasanid, the new king, Ardashir I, abolished the official Babylonian calendar and replaced it with the Zoroastrian. This involved a correction to the places of the "gahanbar", which had slipped back in the seasons since they were fixed. These were placed eight months later, as were the "epagemonai", the 'Gatha' or 'Gah' days after the ancient Zoroastrian hymns of the same name. Other countries, such as the Armenians and Choresmians, did not accept the change.


title: History of calendars

text: Toghril Beg, the founder of the Seljuq dynasty, had made Esfahan the capital of his domains and his grandson Malik-Shah was the ruler of that city from 1073. An invitation was sent to Khayyam from Malik-Shah and from his vizier Nizam al-Mulk asking Khayyam to go to Esfahan to set up an Observatory there. Other leading astronomers were also brought to the Observatory in Esfahan and for 18 years Khayyam led the scientists and produced work of outstanding quality. During this time Khayyam led work on compiling astronomical tables and he also contributed to calendar reform in 1079.


title: History of calendars

text: Khayyam measured the length of the year as 365.24219858156 days. Two comments on this result. Firstly it shows an incredible confidence to attempt to give the result to this degree of accuracy. We know now that the length of the year is changing in the sixth decimal place over a person's lifetime. Secondly it is outstandingly accurate. For comparison the length of the year at the end of the 19th century was 365.242196 days, while today it is 365.242190 days.


title: History of calendars

text: The Greeks, as early as the time of Homer, appear to have been familiar with the division of the year into the twelve lunar months but no intercalary month "Embolimos" or day is then mentioned. Independent of the division of a month into days, it was divided into periods according to the increase and decrease of the moon. Thus, the first day or new moon was called "Noumenia". The month in which the year began, as well as the names of the months, differed among the states, and in some parts even no names existed for the months, as they were distinguished only numerically, as the first, second, third, fourth month, etc.


title: History of calendars

text: The ancient Athenian calendar was a lunisolar calendar with 354-day years, consisting of twelve months of alternating length of 29 or 30 days. To keep the calendar in line with the solar year of 365.242189 days, an extra, intercalary month was added in the years: 3, 6, 8, 11, 14, 17, 19 of the 19-years Metonic cycle. See About the structure of the Attic Calendar The Athenian months were called Hekatombion, Metageitnion, Boedromion, Pyanepsion, Maimakterion, Poseidon, Gamelion, Anthesterion, Elaphebolion, Munychion, Thargelion, and Skirophorion. The intercalary month usually came after Poseidon, and was called second Poseidon. See also: Athenian Calendar. A reconstruction of the Attic Calendar is given by Academy of Episteme.


title: History of calendars

text: In addition to their regular, "festival" calendar, the Athenians maintained a second, political calendar . This "conciliar" calendar divided the year into "prytanies", one for each of the "phylai", the subdivisions of Athenian citizens. The number of phylai, and hence the number of prytanies, varied over time. Until 307 BC, there were 10 phylai. After that the number varies between 11 and 13 (usually 12). Even more confusing, while the conciliar and festival years were about the same length in the 4th century BC, such was not regularly the case earlier or later. Documents dated by prytany are frequently very difficult to assign to a particular equivalent in the Julian calendar.


title: History of calendars

text: The table of Greek Olympiads, following the four-year cycles between the Olympic Games from 1 July 776 BC, continued until the end of the 4th century AD. The Babylonian Era of Nabonassar, beginning on 26 February 747 BC, was used by the Greeks of Alexandria. It was later known in the Middle Ages from the works of Ptolemy.


title: History of calendars

text: The Greek calendars were greatly diversified by the Hellenistic period, with separate traditions in every Greek state. Of primary importance for the reconstruction of the regional Greek calendars is the calendar of Delphi, because of the numerous documents found there recording the manumission of slaves, many of which are dated both in the Delphian and in a regional calendar.


title: History of calendars

text: The Macedonian Era of the Seleucids, which began with the conquest of Babylon by Seleucus I Nicator in 312 BC. It became widely used in the Levant. The Jews knew it as the "era of contracts", and used it in Europe until the 15th century.


title: History of calendars

text: The Roman Republican calendar numbered years based on the sitting consuls. References to the year of consulship were used in both conversation and official records. Romans from the same family often had the same "praenomen", which sometimes makes it difficult to distinguish them, and there were two consuls at any one time, each of whom might sometimes hold the appointment more than once, meaning that it was (and is) necessary to be well educated in history to understand the references. The Romans had an eight-day week, with the market-day falling every eight days. It was called a "nundinum" or 'nine-day' in inclusive counting.


title: History of calendars

text: Most of the regional Hindu calendars are inherited from a system standardized in classical Hindu astronomy as adopted via Indo-Greek transmission in the final centuries BC, and reformed by Gupta era astronomers such as Aryabhata and Varāhamihira.


title: History of calendars

text: Before the Spring and Autumn period (before 770 BC), the Chinese calendars were solar calendars. In the so-called five-phase calendar, the year consists of 10 months and a transition, each month being 36 days long, and the transitions 5 or 6 days. During the Warring States period (~475–220 BC), the primitive lunisolar calendars were established under the Zhou Dynasty, known as the six ancient calendars (). The months of these calendars begin on the day with the new moon, with 12 or 13 months (lunations) in a year. The intercalary month is placed at the end of the year. In Qin China, the Qin calendar () was introduced. It follows the rules of Zhuanxu's calendar, but the months order follows the Xia's calendar.


title: History of calendars

text: Timekeeping was important to Vedic rituals, and "Jyotisha" was the Vedic-era field of tracking and predicting the movements of astronomical bodies in order to keep time, in order to fix the day and time of these rituals, which were developed around the end of 2nd millennium BC as mentioned in "Sathapatha Brahmana". This study was one of the six ancient "Vedangas", or ancillary science connected with the Vedas – the scriptures of Hinduism, which was quoted by 5th-century BC scholar Yaska. The ancient extant text on Jyotisha is the "Vedanga-Jyotisha", which exists in two editions, one linked to Rigveda and other to Yajurveda. The Rigveda version is variously attributed to sage Lagadha, and sometimes to sage Shuci. The Yajurveda version credits no particular sage, has survived into the modern era with a commentary of Somakara, and is the more studied version.


title: History of calendars

text: The Jyotisha text "Brahma-siddhanta", probably composed in the 5th century AD, discusses how to use the movement of planets, sun and moon to keep time and calendar. This text also lists trigonometry and mathematical formulae to support its theory of orbits, predict planetary positions and calculate relative mean positions of celestial nodes and apsides. The text is notable for presenting very large integers, such as 4.32 billion years as the lifetime of the current universe.


title: History of calendars

text: Water clock and sun dials are mentioned in many ancient Hindu texts such as the Arthashastra. The Jyotisha texts present mathematical formulae to predict the length of day time, sun rise and moon cycles.


title: History of calendars

text: The modern Hindu calendar, sometimes referred to as "Panchanga", is a collective term for the various lunisolar calendars traditionally used in Hinduism. They adopt a similar underlying concept for timekeeping, but differ in their relative emphasis on the moon cycle or the sun cycle, the names of months and when they consider the New Year to start. The ancient Hindu calendar is similar in conceptual design to the Jewish calendar, but different from the Gregorian calendar. Unlike the Gregorian calendar which adds additional days to the lunar month to adjust for the mismatch between twelve lunar cycles (354 lunar days) and nearly 365 solar days, the Hindu calendar maintains the integrity of the lunar month, but inserts an extra full month according to complex rules, every few years, to ensure that the festivals and crop related rituals fall in the appropriate season.


title: History of calendars

text: The Hindu calendars have been in use in the Indian subcontinent since ancient times, and remain in use by the Hindus in India and Nepal, particularly to set Hindu festival dates. Early Buddhist and Jain communities of India adopted the ancient Hindu calendar, later Vikrami calendar and then local Buddhist calendars. Buddhist and Jain festivals continue to be scheduled according to a lunar system in the luni-solar calendar.


title: History of calendars

text: The old Roman year had 304 days divided into 10 months, beginning with March. However the ancient historian Livy gave credit to the second early Roman king Numa Pompilius for devising a calendar of 12 months. The extra months "Ianuarius" and "Februarius" had been invented, supposedly by Numa Pompilius, as stop-gaps. Julius Caesar realized that the system had become inoperable, so he effected drastic changes in the year of his third consulship. The New Year in 709 AUC began on 1 January and ran over 365 days until 31 December. Further adjustments were made under Augustus, who introduced the concept of the "leap year" in 757 AUC (AD 4). The resultant Julian calendar remained in almost universal use in Europe until 1582, and in some countries until as late as the twentieth century.


title: History of calendars

text: Marcus Terentius Varro introduced the "Ab urbe condita" epoch, assuming a foundation of Rome in 753 BC. The system remained in use during the early Middle Ages until the widespread adoption of the Dionysian era in the Carolingian period.


title: History of calendars

text: In the Roman Empire, the AUC year could be used alongside the consular year, so that the consulship of Quintus Fufius Calenus and Publius Vatinius could be determined as 707 AUC (or 47 BC), the third consulship of Caius Julius Caesar, with Marcus Aemilius Lepidus, as 708 AUC (or 46 BC), and the fourth consulship of Gaius Julius Caesar as 709 AUC (or 45 BC).


title: History of calendars

text: The seven-day week has a tradition reaching back to the ancient Near East, but the introduction of the "planetary week" which remains in modern use dates to the Roman Empire period (see also names of the days of the week).


title: History of calendars

text: The oldest calendar of saints of the Church of Rome was compiled in the mid-4th century, under Pope Julius I or Pope Liberius. It contained both pagan and Christian festivals. The oldest extant manuscript of the early Christian calendar is the so-called Calendar of Filocalus, produced in AD 354. A more extensive martyrology was compiled by Jerome in the early 5th century. Jean Mabillon published a calendar of the church of Carthage made in ca. AD 483. The Anno Domini epoch is introduced in the 6th century. Extant calendars of the early medieval period are based on Jerome's system of numbering of the years of the Metonic cycle, later called the Golden Numbers. A Carolingian-era calendar published by Luc d'Achery is entitled "Incipit Ordo Solaris Anni cum Litteris a S. Hieronymo superpositis, ad explorandum Septimanae Diem, et Lunae Aetatem investigandam in unoquoque Die per xix Annos." ("here begins the order of the solar year with the letters placed by Saint Jerome, for the purpose of finding the day of the week and the age of the Moon for any day within [the cycle of] 19 years"). The Leiden Aratea, a Carolingian copy (dated 816) of an astronomical treatise of Germanicus, is an important source for the transmission of the ancient Christian calendar to the medieval period.


title: History of calendars

text: In the 8th century, the Anglo-Saxon historian Bede the Venerable used another Latin term, ""ante uero incarnationis dominicae tempus"" ("the time before the Lord's true incarnation", equivalent to the English "before Christ"), to identify years before the first year of this era. According to the Catholic Encyclopedia, even Popes continued to date documents according to regnal years, and usage of AD only gradually became common in Europe from the 11th to the 14th centuries. In 1422, Portugal became the last Western European country to adopt the "Anno Domini" system.


title: History of calendars

text: The Icelandic calendar was introduced in the 10th century. While the ancient Germanic calendars were based on lunar months, the new Icelandic calendar introduced a purely solar reckoning, with a year having a fixed number of weeks (52 weeks or 364 days). This necessitated the introduction of "leap weeks" instead of the Julian leap days.


title: History of calendars

text: In 1267, the medieval scientist Roger Bacon stated the times of full moons as a number of hours, minutes, seconds, thirds, and fourths ("horae", "minuta", "secunda", "tertia", and "quarta") after noon on specified calendar dates. Although a third for of a second remains in some languages, for example Arabic ثالثة, the modern second is further divided decimally.


title: History of calendars

text: Rival calendar eras to "Anno Domini" remained in use in Christian Europe. In Spain, the "Era of the Caesars" was dated from Octavian's conquest of Iberia in 39 BC. It was adopted by the Visigoths and remained in use in Catalonia until 1180, Castille until 1382 and Portugal until 1415.


title: History of calendars

text: For chronological purposes, the flaw of the Anno Domini system was that dates have to be reckoned backwards or forwards according as they are BC or AD. According to the "Catholic Encyclopedia", "in an ideally perfect system all events would be reckoned in one sequence. The difficulty was to find a starting point whence to reckon, for the beginnings of history in which this should naturally be placed are those of which chronologically we know least." For both Christians and Jews, the prime historical date was the Year of Creation, or "Annus Mundi". The Eastern Orthodox Church fixed the date of Creation at 5509 BC. This remained the basis of the ecclesiastical calendar in the Greek and Russian Orthodox world until modern times. The Coptic Church fixed on 5500 BC. Later, the Church of England, under Archbishop Ussher in 1650, would pick 4004 BC.


title: History of calendars

text: The Islamic calendar is based on the prohibition of intercalation ("nasi'") by Muhammad, in Islamic tradition dated to a sermon held on 9 Dhu al-Hijjah AH 10 (Julian date: 6 March 632). This resulted in an observationally based lunar calendar shifting relative to the seasons of the solar year.


title: History of calendars

text: During the Mughal rule, land taxes were collected from Bengali people according to the Islamic Hijri calendar. This calendar was a lunar calendar, and its new year did not coincide with the solar agricultural cycles. According to some sources, Mughal Emperor Akbar asked his royal astronomer Fathullah Shirazi to create a new calendar by combining the lunar Islamic calendar and solar Hindu calendar already in use, and this was known as "Fasholi shan" (harvest calendar). According to Amartya Sen, Akbar's official calendar "Tarikh-ilahi" with the zero year of 1556 AD was a blend of pre-existing Hindu and Islamic calendars. It was not used much in India outside of Akbar's Mughal court, and after his death the calendar he launched was abandoned. However, adds Sen, there are traces of the "Tarikh-ilahi" that survive in the Bengali calendar. Some historians attribute the Bengali calendar to the 7th-century Hindu king Shashanka.


title: History of calendars

text: The ancient Taichu calendar of China was refined in the medieval period. The Dàmíng Calendar (), created in the Liang dynasty by Zu Chongzhi, introduced the equinoxes. The use of a syzygy to determine the lunar month was first described in the Tang dynasty Wùyín Yuán Calendar ().


title: History of calendars

text: The Yuan dynasty (13th/14th century) Shòushí calendar () used spherical trigonometry to find the length of the tropical year. This calendar had a 365.2425-day year, identical to the Gregorian calendar.


title: History of calendars

text: A number of other epichoric calendars are tentatively reconstructed for the medieval period. Such reconstructions are mostly limited to a list of month names, as is the case with the pre-Christian Germanic calendar as well as with the Bulgar calendar, which was supposedly in use among the Bulgars in the 10th century, as reconstructed from the 15th-century "Nominalia of the Bulgarian khans".


title: History of calendars

text: Of all the ancient calendar systems, the Maya and other Mesoamerican systems are the most complex. The Mayan calendar had two years, the 260-day Sacred Round, or "tzolkin", and the 365-day Vague Year, or "haab".


title: History of calendars

text: The Sacred Round of 260 days is composed of two smaller cycles: the numbers 1 through 13, coupled with 20 different day names: Imix, Ik, Akbal, Kan, Chicchan, Cimi, Manik, Lamat, Muluc, Oc, Chuen, Eb, Ben, Ix, Men, Cib, Caban, Eiznab, Cauac, and Ahau. The Sacred Round was used to determine important activities related to the gods and humans: name individuals, predict the future, decide on auspicious dates for battles, marriages, and so on.


title: History of calendars

text: The two cycles of 13 and 20 intermesh and are repeated without interruption: the cycle would begin with 1 Imix, then 2 Ik, then 3 Akbal and so on until the number 13 was reached, at which point the number cycle was restarted so 13 Ben would be followed by 1 Ix, 2 Men and so on. This time Imix would be numbered 8. The cycle ended after 260 days, with the last day being 13 Ahau.


title: History of calendars

text: The Vague Year of 365 days is similar to the modern Gregorian calendar, consisting of 18 months of 20 days each, with an unlucky five-day period at the end. The Vague Year had to do primarily with the seasons and agriculture, and was based on the solar cycle. The 18 Maya months are known, in order, as: Pop, Uo, Zip, Zotz, Tzec, Xuc, Yaxkin, Mol, Chen, Yax, Zac, Ceh, Mac, Kankin, Maun, Pax, Kayab and Cumku. The unlucky five-day period was known as Uayeb, and was considered a time which could hold danger, death and bad luck.


title: History of calendars

text: The Vague Year began with the month of Pop. The Maya 20-day month always begins with the seating of the month, followed by days numbered 1 to 19, then the seating of the following month, and so on. This ties in with the Maya notion that each month influences the next. The Maya new year would start with 1 Pop, followed by 2 Pop, all the way through to 19 Pop, followed by the seating of the month of Uo, written as 0 Uo, then 1 Uo, 2 Uo and so on. These two cycles coincided every 52 years. The 52-year period of time was called a "bundle" and was similar to a modern-day century.


title: History of calendars

text: While the Gregorian calendar is now in worldwide use for secular purposes, various medieval or ancient calendars remain in regional use for religious or social purposes, including the Julian calendar, the Hebrew calendar, the Islamic calendar, various Hindu calendars, the Zoroastrian calendar, etc.


title: History of calendars

text: There are also various modern calendars that see limited use, either created for the use of new religious movements or reformed versions of older religious calendars, or calendars introduced by regionalist or nationalist movements.


title: Ironside (1967 TV series)

text: Ironside is an American television crime drama that aired on NBC over eight seasons from 1967 to 1975. The show starred Raymond Burr as Robert T. Ironside (usually addressed by the title "Chief Ironside"), a consultant for the San Francisco police department (formerly chief of detectives), who was paralyzed from the waist down after being shot while on vacation. The character debuted on March 28, 1967, in a TV movie entitled "Ironside". When the series was broadcast in the United Kingdom, from late 1967 onward, it was broadcast as "A Man Called Ironside". The show earned Burr six Emmy and two Golden Globe nominations.


title: Ironside (1967 TV series)

text: "Ironside" is a production of Burr's Harbour Productions Unlimited in association with Universal Television.


title: Ironside (1967 TV series)

text: The series revolves around former San Francisco Police Department (SFPD) Chief of Detectives Robert T. Ironside (Raymond Burr), a veteran of more than 20 years of police service, forced to retire from the department after a sniper's bullet to the spine paralyzed him from the waist down, resulting in his reliance on a wheelchair. In the pilot episode, a television movie, Ironside shows his strength of character and gets himself appointed a peculiar and unprecedented job; a "special department consultant", by his good friend, Police Commissioner Dennis Randall. He does this by calling a press conference and then tricking Commissioner Randall into meeting his terms. In the pilot, Ironside eventually solves the mystery of the ambush. He requests Ed Brown and Eve Whitfield be assigned to him as his own private law enforcement force.


title: Ironside (1967 TV series)

text: Supporting characters on "Ironside" included Det. Sgt. Edward "Ed" Brown (Don Galloway) and a young socialite-turned-plainclothes officer, Eve Whitfield (Barbara Anderson). In addition, delinquent-turned assistant Mark Sanger (Don Mitchell), who subsequently attends and graduates from law school (night classes were mentioned from early on), joins the San Francisco police force himself in the sixth season, then marries late in the run of the series. Commissioner Randall was played by Gene Lyons.


title: Ironside (1967 TV series)

text: After the program's fourth season, Anderson left for personal reasons, and her character was then replaced by another young policewoman, Fran Belding (Elizabeth Baur), who filled much the same role for four more years.


title: Ironside (1967 TV series)

text: Ironside uses a fourth-floor room (for living and office space) in the old San Francisco Hall of Justice building, which housed the city's police headquarters. He recruits Mark Sanger to be his personal assistant after Sanger is brought in as a suspect who wanted to kill Ironside. Ironside acquires a specially equipped, former fleet-modified 1940 -ton Ford police patrol wagon, with bulletproof glass and a specially modified high-performance supercharged and fuel-injected V-8 engine. This is replaced in the episode titled "Poole's Paradise" after the van is destroyed by Sergeant Brown as part of a way to trick a corrupt sheriff. At the end of the episode, the patrol wagon is replaced by a one-off fully custom modified 1969 1-ton Ford Econoline Window Van.


title: Ironside (1967 TV series)

text: The show became a success as Ironside depended on brains and initiative in solving cases. Although Ironside is portrayed as good-hearted and honest, he often maintains a somewhat gruff persona. The series enjoyed a seven-and-a-half-season run on NBC, drawing respectable, if not always high ratings. As the shortened eighth and final season began (only 16 of 19 episodes produced were aired by NBC), Universal released a syndicated rerun package of episodes from earlier seasons under the title "The Raymond Burr Show," reflecting the practice of that time to differentiate original network episodes from syndicated reruns whenever possible. After NBC's midseason cancellation, however, the syndicated episodes reverted to the "Ironside" title.


title: Ironside (1967 TV series)

text: The show was filmed in a mixture of locations, sometimes in San Francisco, but also with a large number of studio scenes (including scenes with conversations in a moving vehicle, where a traffic backdrop is used). The shows contained stock footage of San Francisco, with pan shots of Coit Tower or clips of traffic scenes.


title: Ironside (1967 TV series)

text: Ironside and his team used a rather large open space on the fourth floor of the Old Hall of Justice in San Francisco at 750 Kearny Street between Washington and Merchant Streets. The Old Hall had already been demolished while "Ironside "was still in production. It had been abandoned in 1961 and demolished in late 1967. The SFPD had begun using their new home by January 1962. In December 1967, demolition finally began. Wrecking balls and bulldozers took 5 months to raze the building.


title: Ironside (1967 TV series)

text: The opening theme music was composed by Quincy Jones, and was the first synthesizer-based television theme song. In 1971, Jones recorded a fuller four-minute band version for the album "Smackwater Jack". This recording was then edited and used for the opening credits of the fifth through eighth seasons (1971–1975). (The entire album track can be heard in the fifth-season episode "Unreasonable Facsimile" as Ironside and team track a suspect on the streets of San Francisco.) The iconic theme music has since been sampled in numerous recordings and soundtracks to recent television commercials and shows, including "All Caps" by the hip-hop duo Madvillain.


title: Ironside (1967 TV series)

text: In addition to the opening theme music, Quincy Jones composed the entire score for the first eight episodes. Oliver Nelson took over those duties up to the end of the winter to spring 1972 episodes. Nelson was then replaced by Marty Paich for nearly all of the episodes from the beginning of the fall of that year until the last episode that was produced, in late 1974. The song "Even When You Cry", with music composed by Jones and lyrics written by Alan and Marilyn Bergman, was performed by James Farentino in the episode "Something for Nothing", while Marcia Strassman had already sung it off-screen in the earlier episode "The Man Who Believed"; both installments were originally transmitted during season one.


title: Ironside (1967 TV series)

text: <nowiki>**</nowiki> The last three episodes of the series were not broadcast on NBC, but were later seen in syndication, as well as released on DVD.


title: Ironside (1967 TV series)

text: Burr and the main cast reunited for a made-for-TV movie in 1993, "The Return of Ironside", which aired on May 4, 1993, on NBC, not long before Burr's death. At the time, Burr was starring in a series of telefilms for NBC playing his most famous character, Perry Mason. In the years between the end of "Ironside" in 1975 and the first "Perry Mason" movie in 1985, Burr's appearance had undergone some changes. His hair was grayer, he had gained a significant amount of weight, and after years of playing clean-shaven characters, he grew a beard.


title: Ironside (1967 TV series)

text: Since nearly 20 years had passed since "Ironside" left the air, and as he had been playing Perry Mason on television for the previous eight years, Burr felt that he was more associated with Perry Mason. He believed that to play Ironside properly and not confuse viewers, he would need to undergo a small makeover to distinguish the Ironside character from the more identifiable Perry Mason. Burr thus had his hair colored (which was unnecessary, since Burr was already gray-haired when "Ironside" originally aired) and cut his beard down to a goatee. One thing Burr did not need to do, however, was pretend to be disabled. At the time the "Ironside" reunion went into production, Burr had been suffering from kidney cancer that had metastasized to his liver, and the disease left him unable to stand or walk without assistance. Thus, like Ironside, Burr used a wheelchair to get around.


title: Ironside (1967 TV series)

text: Unlike the original series, which took place in San Francisco, the reunion was set and filmed in Denver, Colorado, with the justification that the character Ed Brown had become the city's deputy chief of police. (Denver was also where most of Burr's "Perry Mason" TV movies were produced.) Galloway, Mitchell, Anderson, and Baur recreated their roles for the movie, though Anderson and Baur had not worked at the same time on the original series.


title: Ironside (1967 TV series)

text: At the start of its sixth season, "Ironside" did a two-part crossover episode with "", titled "Five Days in the Death of Sergeant Brown", where Ed is critically injured by a sniper and is treated by Dr. David Craig and his medical staff. Part 1 was broadcast on "Ironside" and part 2 on "The New Doctors". Part 2 is now shown in reruns as an episode of "Ironside". E. G. Marshall and David Hartman (stars of "The New Doctors") received starring credit in the opening credits of both episodes. Part 2 features a longer edited version of Quincy Jones' "Ironside" theme as heard on his 1971 album "Smackwater Jack".


title: Ironside (1967 TV series)

text: NBC's 1971 fall TV season opened with a two-hour crossover between "Ironside" and a new series, "Sarge", starring George Kennedy as a cop-turned-priest. Kennedy's San Diego–based Father Samuel Cavanaugh comes to San Francisco because of the death of a friend and fellow priest, and his investigation gets him embroiled with Ironside and his staff. The special consolidated the two shows' consecutive time slots and has been subsequently seen as a TV-movie, "The Priest Killer".


title: Ironside (1967 TV series)

text: Jessica Walter guest-starred in a spin-off episode for the series "Amy Prentiss", which aired as part of "The NBC Mystery Movie" during the 1974–1975 season. She played a relatively young investigator who becomes chief of detectives for the San Francisco Police Department. Helen Hunt, in an early role, played Prentiss' preteen daughter, Jill. Three two-hour episodes were aired.


title: Ironside (1967 TV series)

text: The 22nd episode of season 7, airing in March 1974, and entitled "Riddle at 24,000," was a pilot for "Dr. Domingo," a proposed spin-off series starring Desi Arnaz as a crime-solving physician in a small, California town. It was written by Lane Slate, perhaps best known as the screenwriter of "They Only Kill Their Masters", the James Garner movie about a small-town police chief.


title: Ironside (1967 TV series)

text: In 2013, a short-lived remake with the same name aired on NBC. Actor Blair Underwood took on the title role (with none of the other characters from the original series being used), while the action was relocated from San Francisco to New York City. This version of the character was more in the tough cop mold, often at odds with his superiors over his unrelenting, even violent approach to police work. The series was lambasted by critics and ignored by viewers, and was cancelled and pulled after the airing of just four episodes (of 9 produced).


title: Ironside (1967 TV series)

text: An episode of "Get Smart" that aired in March 1969 was titled "Leadside" and featured a wheelchair-using master criminal by that name (and his assistants). Leadside could not walk, but he was able to run. Another episode, called "Ironhand", had a KAOS operative with a hand encased in metal.


title: Ironside (1967 TV series)

text: On "The Benny Hill Show", Benny Hill played Ironside in a few sketches, most notably in a sketch called "Murder on the Oregon Express", which parodied several TV detective characters.


title: Ironside (1967 TV series)

text: Impressionist Billy Howard included Ironside as one of the detectives parodied in his novelty hit record "King of the Cops".


title: Ironside (1967 TV series)

text: The 1980 television movie "Murder Can Hurt You" spoofs numerous TV detectives from the 1970s and '80s, and includes Victor Buono playing the wheelchair-using detective Ironbottom.


title: Ironside (1967 TV series)

text: "American Dad" has an episode, "Wheels and Legman", that loosely parodies Ironside in which Roger and Steve have a fictional detective agency.


title: Ironside (1967 TV series)

text: In the "Gone Efficient" episode of "Harvey Birdman, Attorney at Law", a man in a wheelchair is shown pleading a case in front of Judge Mentok (who strongly resembles Raymond Burr) as a nod to both Ironside and Perry Mason.


title: Ironside (1967 TV series)

text: Shout! Factory has released the first four seasons of "Ironside" on DVD in Region 1. Seasons 3 and 4 were released as "Shout Factory Exclusives", available exclusively through Shout!'s online store.


title: Ironside (1967 TV series)

text: On May 9, 2017, Shout! Factory re-released season 3 as a general retail release. Season 4 was re-released on August 22, 2017.


title: Ironside (1967 TV series)

text: In Region 4, Madman Entertainment released all eight seasons on DVD. The eighth and final season, which included the 1993 TV reunion movie "The Return of Ironside", was released on October 19, 2011.


title: Ironside (1967 TV series)

text: Season 5 includes the two-part crossover TV movie episode "The Priest Killer", a crossover with the series "Sarge".


title: Fly ash

text: Fly ash, flue ash, coal ash, or pulverised fuel ash (in the UK) plurale tantum: coal combustion residuals (CCRs)is a coal combustion product that is composed of the particulates (fine particles of burned fuel) that are driven out of coal-fired boilers together with the flue gases. Ash that falls to the bottom of the boiler's combustion chamber (commonly called a firebox) is called bottom ash. In modern coal-fired power plants, fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys. Together with bottom ash removed from the bottom of the boiler, it is known as coal ash.


title: Fly ash

text: Depending upon the source and composition of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO) (both amorphous and crystalline), aluminium oxide (AlO) and calcium oxide (CaO), the main mineral compounds in coal-bearing rock strata.


title: Fly ash

text: The use of fly ash as a lightweight aggregate (LWA) offers a valuable opportunity to recycle one of the largest waste streams in the US. In addition, fly ash can offer many benefits, both economically and environmentally when utilized as a LWA.


title: Fly ash

text: The minor constituents of fly ash depend upon the specific coal bed composition but may include one or more of the following elements or compounds found in trace concentrations (up to hundreds ppm): gallium, arsenic, beryllium, boron, cadmium, chromium, hexavalent chromium, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and vanadium, along with very small concentrations of dioxins and PAH compounds. It also has unburnt carbon.


title: Fly ash

text: In the past, fly ash was generally released into the atmosphere, but air pollution control standards now require that it be captured prior to release by fitting pollution control equipment. In the United States, fly ash is generally stored at coal power plants or placed in landfills. About 43% is recycled, often used as a pozzolan to produce hydraulic cement or hydraulic plaster and a replacement or partial replacement for Portland cement in concrete production. Pozzolans ensure the setting of concrete and plaster and provide concrete with more protection from wet conditions and chemical attack.


title: Fly ash

text: In the case that fly (or bottom) ash is not produced from coal, for example when solid waste is incinerated in a waste-to-energy facility to produce electricity, the ash may contain higher levels of contaminants than coal ash. In that case the ash produced is often classified as hazardous waste.


title: Fly ash

text: Fly ash material solidifies while suspended in the exhaust gases and is collected by electrostatic precipitators or filter bags. Since the particles solidify rapidly while suspended in the exhaust gases, fly ash particles are generally spherical in shape and range in size from 0.5 µm to 300 µm. The major consequence of the rapid cooling is that few minerals have time to crystallize, and that mainly amorphous, quenched glass remains. Nevertheless, some refractory phases in the pulverized coal do not melt (entirely), and remain crystalline. In consequence, fly ash is a heterogeneous material.


title: Fly ash

text: SiO, AlO, FeO and occasionally CaO are the main chemical components present in fly ashes. The mineralogy of fly ashes is very diverse. The main phases encountered are a glass phase, together with quartz, mullite and the iron oxides hematite, magnetite and/or maghemite. Other phases often identified are cristobalite, anhydrite, free lime, periclase, calcite, sylvite, halite, portlandite, rutile and anatase. The Ca-bearing minerals anorthite, gehlenite, akermanite and various calcium silicates and calcium aluminates identical to those found in Portland cement can be identified in Ca-rich fly ashes.


title: Fly ash

text: The mercury content can reach , but is generally included in the range 0.01–1 ppm for bituminous coal.


title: Fly ash

text: The concentrations of other trace elements vary as well according to the kind of coal combusted to form it.


title: Fly ash

text: Two classes of fly ash are defined by American Society for Testing and Materials (ASTM) C618: Class F fly ash and Class C fly ash. The chief difference between these classes is the amount of calcium, silica, alumina, and iron content in the ash. The chemical properties of the fly ash are largely influenced by the chemical content of the coal burned (i.e., anthracite, bituminous, and lignite).


title: Fly ash

text: Not all fly ashes meet ASTM C618 requirements, although depending on the application, this may not be necessary. Fly ash used as a cement replacement must meet strict construction standards, but no standard environmental regulations have been established in the United States. Seventy-five percent of the fly ash must have a fineness of 45 µm or less, and have a carbon content, measured by the loss on ignition (LOI), of less than 4%. In the US, LOI must be under 6%. The particle size distribution of raw fly ash tends to fluctuate constantly, due to changing performance of the coal mills and the boiler performance. This makes it necessary that, if fly ash is used in an optimal way to replace cement in concrete production, it must be processed using beneficiation methods like mechanical air classification. But if fly ash is used as a filler to replace sand in concrete production, unbeneficiated fly ash with higher LOI can be also used. Especially important is the ongoing quality verification. This is mainly expressed by quality control seals like the Bureau of Indian Standards mark or the DCL mark of the Dubai Municipality.


title: Fly ash

text: The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. This fly ash is pozzolanic in nature, and contains less than 7% lime (CaO). Possessing pozzolanic properties, the glassy silica and alumina of Class F fly ash requires a cementing agent, such as Portland cement, quicklime, or hydrated lime—mixed with water to react and produce cementitious compounds. Alternatively, adding a chemical activator such as sodium silicate (water glass) to a Class F ash can form a geopolymer.


title: Fly ash

text: Fly ash produced from the burning of younger lignite or sub-bituminous coal, in addition to having pozzolanic properties, also has some self-cementing properties. In the presence of water, Class C fly ash hardens and gets stronger over time. Class C fly ash generally contains more than 20% lime (CaO). Unlike Class F, self-cementing Class C fly ash does not require an activator. Alkali and sulfate () contents are generally higher in Class C fly ashes.


title: Fly ash

text: At least one US manufacturer has announced a fly ash brick containing up to 50% Class C fly ash. Testing shows bricks meet or exceed the performance standards listed in ASTM C 216 for conventional clay brick. It is also within the allowable shrinkage limits for concrete brick in ASTM C 55, Standard Specification for Concrete Building Brick. It is estimated that the production method used in fly ash bricks will reduce the embodied energy of masonry construction by up to 90%. Bricks and pavers were expected to be available in commercial quantities before the end of 2009.


title: Fly ash

text: In the past, fly ash produced from coal combustion was simply entrained in flue gases and dispersed into the atmosphere. This created environmental and health concerns that prompted laws in heavily industrialized countries that have reduced fly ash emissions to less than 1% of ash produced. Worldwide, more than 65% of fly ash produced from coal power stations is disposed of in landfills and ash ponds.


title: Fly ash

text: Ash that is stored or deposited outdoors can eventually leach toxic compounds into underground water aquifers. For this reason, much of the current debate around fly ash disposal revolves around creating specially lined landfills that prevent the chemical compounds from being leached into the ground water and local ecosystems.


title: Fly ash

text: Since coal was the dominant energy source in the United States for many decades, power companies often located their coal plants near metropolitan areas. Compounding the environmental issues, the coal plants need significant amounts of water to operate their boilers, leading coal plants (and later their fly ash storage basins) to be located near metropolitan areas and near rivers and lakes which are often used as drinking supplies by nearby cities. Many of those fly ash basins were unlined and also at great risk of spilling and flooding from nearby rivers and lakes. For example, Duke Energy in North Carolina has been involved in several major lawsuits related to its coal ash storage and spills into the leakage of ash into the water basin.


title: Fly ash

text: The recycling of fly ash has become an increasing concern in recent years due to increasing landfill costs and current interest in sustainable development. , coal-fired power plants in the US reported producing of fly ash, of which were reused in various applications. Environmental benefits to recycling fly ash includes reducing the demand for virgin materials that would need quarrying and cheap substitution for materials such as Portland cement.


title: Fly ash

text: There is no US governmental registration or labelling of fly ash utilization in the different sectors of the economy – industry, infrastructures and agriculture. Fly ash utilization survey data, acknowledged as incomplete, are published annually by the American Coal Ash Association.


title: Fly ash

text: Other applications include cosmetics, toothpaste, kitchen counter tops, floor and ceiling tiles, bowling balls, flotation devices, stucco, utensils, tool handles, picture frames, auto bodies and boat hulls, cellular concrete, geopolymers, roofing tiles, roofing granules, decking, fireplace mantles, cinder block, PVC pipe, structural insulated panels, house siding and trim, running tracks, blasting grit, recycled plastic lumber, utility poles and crossarms, railway sleepers, highway noise barriers, marine pilings, doors, window frames, scaffolding, sign posts, crypts, columns, railroad ties, vinyl flooring, paving stones, shower stalls, garage doors, park benches, landscape timbers, planters, pallet blocks, molding, mail boxes, artificial reef, binding agent, paints and undercoatings, metal castings, and filler in wood and plastic products.


title: Fly ash

text: Owing to its pozzolanic properties, fly ash is used as a replacement for Portland cement in concrete. The use of fly ash as a pozzolanic ingredient was recognized as early as 1914, although the earliest noteworthy study of its use was in 1937. Roman structures such as aqueducts or the Pantheon in Rome used volcanic ash or pozzolana (which possesses similar properties to fly ash) as pozzolan in their concrete. As pozzolan greatly improves the strength and durability of concrete, the use of ash is a key factor in their preservation.


title: Fly ash

text: Use of fly ash as a partial replacement for Portland cement is particularly suitable but not limited to Class C fly ashes. Class "F" fly ashes can have volatile effects on the entrained air content of concrete, causing reduced resistance to freeze/thaw damage. Fly ash often replaces up to 30% by mass of Portland cement, but can be used in higher dosages in certain applications. In some cases, fly ash can add to the concrete's final strength and increase its chemical resistance and durability.


title: Fly ash

text: Fly ash can significantly improve the workability of concrete. Recently, techniques have been developed to replace partial cement with high-volume fly ash (50% cement replacement). For roller-compacted concrete (RCC)[used in dam construction], replacement values of 70% have been achieved with processed fly ash at the Ghatghar dam project in Maharashtra, India. Due to the spherical shape of fly ash particles, it can increase workability of cement while reducing water demand. Proponents of fly ash claim that replacing Portland cement with fly ash reduces the greenhouse gas "footprint" of concrete, as the production of one ton of Portland cement generates approximately one ton of CO, compared to no CO generated with fly ash. New fly ash production, i.e., the burning of coal, produces approximately 20 to 30 tons of CO per ton of fly ash. Since the worldwide production of Portland cement is expected to reach nearly 2 billion tons by 2010, replacement of any large portion of this cement by fly ash could significantly reduce carbon emissions associated with construction, as long as the comparison takes the production of fly ash as a given.


title: Fly ash

text: Fly ash properties are unusual among engineering materials. Unlike soils typically used for embankment construction, fly ash has a large uniformity coefficient and it consists of clay-sized particles. Engineering properties that affect the use of fly ash in embankments include grain size distribution, compaction characteristics, shear strength, compressibility, permeability, and frost susceptibility. Nearly all the types of fly ash used in embankments are Class F.


title: Fly ash

text: Soil stabilization is the permanent physical and chemical alteration of soils to enhance their physical properties. Stabilization can increase the shear strength of a soil and/or control the shrink-swell properties of a soil, thus improving the load-bearing capacity of a sub-grade to support pavements and foundations. Stabilization can be used to treat a wide range of sub-grade materials from expansive clays to granular materials. Stabilization can be achieved with a variety of chemical additives including lime, fly ash, and Portland cement. Proper design and testing is an important component of any stabilization project. This allows for the establishment of design criteria, and determination of the proper chemical additive and admixture rate that achieves the desired engineering properties. Stabilization process benefits can include: Higher resistance (R) values, Reduction in plasticity, Lower permeability, Reduction of pavement thickness, Elimination of excavation – material hauling/handling – and base importation, Aids compaction, Provides "all-weather" access onto and within projects sites. Another form of soil treatment closely related to soil stabilization is soil modification, sometimes referred to as "mud drying" or soil conditioning. Although some stabilization inherently occurs in soil modification, the distinction is that soil modification is merely a means to reduce the moisture content of a soil to expedite construction, whereas stabilization can substantially increase the shear strength of a material such that it can be incorporated into the project's structural design. The determining factors associated with soil modification vs soil stabilization may be the existing moisture content, the end use of the soil structure and ultimately the cost benefit provided. Equipment for the stabilization and modification processes include: chemical additive spreaders, soil mixers (reclaimers), portable pneumatic storage containers, water trucks, deep lift compactors, motor graders.


title: Fly ash

text: Fly ash is also used as a component in the production of flowable fill (also called controlled low strength material, or CLSM), which is used as self-leveling, self-compact backfill material in lieu of compacted earth or granular fill. The strength of flowable fill mixes can range from 50 to 1,200 lbf/in (0.3 to 8.3 MPa), depending on the design requirements of the project in question. Flowable fill includes mixtures of Portland cement and filler material, and can contain mineral admixtures. Fly ash can replace either the Portland cement or fine aggregate (in most cases, river sand) as a filler material. High fly ash content mixes contain nearly all fly ash, with a small percentage of Portland cement and enough water to make the mix flowable. Low fly ash content mixes contain a high percentage of filler material, and a low percentage of fly ash, Portland cement, and water. Class F fly ash is best suited for high fly ash content mixes, whereas Class C fly ash is almost always used in low fly ash content mixes.


title: Fly ash

text: Asphalt concrete is a composite material consisting of an asphalt binder and mineral aggregate commonly used to surface roads. Both Class F and Class C fly ash can typically be used as a mineral filler to fill the voids and provide contact points between larger aggregate particles in asphalt concrete mixes. This application is used in conjunction, or as a replacement for, other binders (such as Portland cement or hydrated lime). For use in asphalt pavement, the fly ash must meet mineral filler specifications outlined in ASTM D242. The hydrophobic nature of fly ash gives pavements better resistance to stripping. Fly ash has also been shown to increase the stiffness of the asphalt matrix, improving rutting resistance and increasing mix durability.


title: Fly ash

text: Coal and shale oil fly ashes have been used as a filler for thermoplastics that could be used for injection molding applications.


title: Fly ash

text: More recently, fly ash has been used as a component in geopolymers, where the reactivity of the fly ash glasses can be used to create a binder similar to a hydrated Portland cement in appearance, but with potentially superior properties, including reduced CO emissions, depending on the formulation.


title: Fly ash

text: Another application of using fly ash is in roller compacted concrete dams. Many dams in the US have been constructed with high fly ash contents. Fly ash lowers the heat of hydration allowing thicker placements to occur. Data for these can be found at the US Bureau of Reclamation. This has also been demonstrated in the Ghatghar Dam Project in India.


title: Fly ash

text: There are several techniques for manufacturing construction bricks from fly ash, producing a wide variety of products. One type of fly ash brick is manufactured by mixing fly ash with an equal amount of clay, then firing in a kiln at about This approach has the principal benefit of reducing the amount of clay required. Another type of fly ash brick is made by mixing soil, plaster of Paris, fly ash and water, and allowing the mixture to dry. Because no heat is required, this technique reduces air pollution. More modern manufacturing processes use a greater proportion of fly ash, and a high pressure manufacturing technique, which produces high strength bricks with environmental benefits.


title: Fly ash

text: In the United Kingdom, fly ash has been used for over fifty years to make concrete building blocks. They are widely used for the inner skin of cavity walls. They are naturally more thermally insulating than blocks made with other aggregates.


title: Fly ash

text: Ash bricks have been used in house construction in Windhoek, Namibia, since the 1970s. There is, however, a problem with the bricks in that they tend to fail or produce unsightly pop-outs. This happens when the bricks come into contact with moisture and a chemical reaction occurs causing the bricks to expand.


title: Fly ash

text: In India, fly ash bricks are used for construction. Leading manufacturers use an industrial standard known as "Pulverized fuel ash for lime-Pozzolana mixture" using over 75% post-industrial recycled waste, and a compression process. This produces a strong product with good insulation properties and environmental benefits.


title: Fly ash

text: Fly ash particles have proved their potential as good reinforcement with aluminum alloys and show the improvement of physical and mechanical properties. In particular, the compression strength, tensile strength, and hardness increase when the percentage of fly ash content is increased, whereas the density decreases. The presence of fly ash cenospheres in a pure Al matrix decreases its coefficient of thermal expansion (CTE).


title: Fly ash

text: It may be possible to use vacuum distillation in order to extract germanium and tungsten from fly ash and recycle them.


title: Fly ash

text: Fly ash, in view of its alkalinity and water absorption capacity, may be used in combination with other alkaline materials to transform sewage sludge into organic fertilizer or biofuel.


title: Fly ash

text: Fly ash, when treated with sodium hydroxide, appears to function well as a catalyst for converting polyethylene into substance similar to crude oil in a high-temperature process called pyrolysis and utilized in waste water treatment.


title: Fly ash

text: In addition, fly ash, mainly class C, may be used in the stabilization/solidification process of hazardous wastes and contaminated soils. For example, the Rhenipal process uses fly ash as an admixture to stabilize sewage sludge and other toxic sludges. This process has been used since 1996 to stabilize large amounts of chromium(VI) contaminated leather sludges in Alcanena, Portugal.


title: Fly ash

text: Coal contains trace levels of trace elements (such as arsenic, barium, beryllium, boron, cadmium, chromium, thallium, selenium, molybdenum and mercury), many of which are highly toxic to humans and other life. Therefore, fly ash obtained after combustion of this coal contains enhanced concentrations of these elements and the potential of the ash to cause groundwater pollution is significant. In the USA there are documented cases of groundwater pollution that followed ash disposal or utilization without the necessary protection having been put in place.


title: Fly ash

text: Constellation Energy disposed fly ash generated by its Brandon Shores Generating Station at a former sand and gravel mine in Gambrills, Maryland, during 1996 to 2007. The ash contaminated groundwater with heavy metals. The Maryland Department of the Environment issued a fine of $1 million to Constellation. Nearby residents filed a lawsuit against Constellation and in 2008 the company settled the case for $54 million.


title: Fly ash

text: In 2014, residents living near the Buck Steam Station in Dukeville, North Carolina, were told that "coal ash pits near their homes could be leaching dangerous materials into groundwater."


title: Fly ash

text: Illinois has many coal ash dumpsites with coal ash generated by coal-burning electric power plants. Of the state's 24 coal ash dumpsites with available data, 22 have released toxic pollutants including arsenic, cobalt, and lithium, into groundwater, rivers and lakes. The hazardous toxic chemicals dumped into the water in Illinois by these coal ash dumpsites include more than 300,000 pounds of aluminum, 600 pounds of arsenic, nearly 300,000 pounds of boron, over 200 pounds of cadmium, over 15,000 pounds of manganese, roughly 1,500 pounds of selenium, roughly 500,000 pounds of nitrogen, and nearly 40 million pounds of sulfate, according to a report by the Environmental Integrity Project, Earthjustice, the Prairie Rivers Network, and the Sierra Club.


title: Fly ash

text: In 2008, the Kingston Fossil Plant in Roane County spilled 1.1 billion gallons of coal ash into the Emory and Clinch Rivers and damaged nearby residential areas. It is the largest industrial spill in the U.S.


title: Fly ash

text: Groundwater surrounding every single one of the 16 coal-burning power plants in Texas has been polluted by coal ash, according to a study by the Environmental Integrity Project (EIP). Unsafe levels of arsenic, cobalt, lithium, and other contaminants were found in the groundwater near all the ash dump sites. At 12 of the 16 sites, the EIP analysis found levels of arsenic in the groundwater 10 times higher than the EPA Maximum Contaminant Level; arsenic has been found to cause several types of cancer. At 10 of the sites, lithium, which causes neurological disease, was found in the groundwater at concentrations more than 1,000 micrograms per liter, which is 25 times the maximum acceptable level. The report concludes that the fossil fuel industry in Texas has failed to comply with federal regulations on coal ash processing, and state regulators have failed to protect the groundwater.


title: Fly ash

text: The effect of fly ash on the environment can vary based on the thermal power plant where it is produced, as well as the proportion of fly ash to bottom ash in the waste product. This is due to the different chemical make-up of the coal based on the geology of the area the coal is found and the burning process of the coal in the power plant. When the coal is combusted, it creates an alkaline dust. This alkaline dust can have a pH ranging from 8 to as high as 12. Fly ash dust can be deposited on topsoil increasing the pH and affecting the plants and animals in the surrounding ecosystem. Trace elements, such as, iron, manganese, zinc, copper, lead, nickel, chromium, cobalt, arsenic, cadmium, and mercury, can be found at higher concentrations compared to bottom ash and the parent coal.


title: Fly ash

text: Fly ash can leach toxic constituents that can be anywhere from one hundred to one thousand times greater than the federal standard for drinking water. Fly ash can contaminate surface water through erosion, surface runoff, airborne particles landing on the water surface, contaminated ground water moving into surface waters, flooding drainage, or discharge from a coal ash pond. Fish can be contaminated a couple of different ways. When the water is contaminated by fly ash, the fish can absorb the toxins through their gills. The sediment in the water can also become contaminated. The contaminated sediment can contaminate the food sources for the fish, the fish can then become contaminated from consuming those food sources. This can then lead to contamination of organisms that consume these fish, such as, birds, bear, and even humans. Once exposed to fly ash contaminating the water, aquatic organisms have had increased levels of calcium, zinc, bromine, gold, cerium, chromium, selenium, cadmium, and mercury.


title: Fly ash

text: Soils contaminated by fly ash showed an increase in bulk density and water capacity, but a decrease in hydraulic conductivity and cohesiveness. The effect of fly ash on soils and microorganisms in the soils are influenced by the pH of the ash and trace metal concentrations in the ash. Microbial communities in contaminated soil have shown reductions in respiration and nitrification. These contaminated soils can be detrimental or beneficial to plant development. Fly ash typically has beneficial outcomes when it corrects nutrient deficiencies in the soil. Most detrimental effects were observed when boron phytotoxicity was observed. Plants absorb elements elevated by the fly ash from the soil. Arsenic, molybdenum, and selenium were the only elements found at potentially toxic levels for grazing animals. Terrestrial organisms exposed to fly ash only showed increased levels of selenium.


title: Fly ash

text: Where fly ash is stored in bulk, it is usually stored wet rather than dry to minimize fugitive dust. The resulting impoundments (ponds) are typically large and stable for long periods, but any breach of their dams or bunding is rapid and on a massive scale.


title: Fly ash

text: In December 2008, the collapse of an embankment at an impoundment for wet storage of fly ash at the Tennessee Valley Authority's Kingston Fossil Plant caused a major release of 5.4 million cubic yards of coal fly ash, damaging three homes and flowing into the Emory River. Cleanup costs may exceed $1.2 billion. This spill was followed a few weeks later by a smaller TVA-plant spill in Alabama, which contaminated Widows Creek and the Tennessee River.


title: Fly ash

text: In 2014, 39,000 tons of ash and 27 million gallons (100,000 cubic meters) of contaminated water spilled into the Dan River near Eden, NC from a closed North Carolina coal-fired power plant that is owned by Duke Energy. It is currently the third worst coal ash spill ever to happen in the United States.


title: Fly ash

text: The U.S. Environmental Protection Agency (EPA) published a Coal Combustion Residuals (CCR) regulation in 2015. The agency continued to classify coal ash as non-hazardous (thereby avoiding strict permitting requirements under of the Resource Conservation and Recovery Act (RCRA), but with new restrictions:


title: Fly ash

text: The regulation was designed to prevent pond failures and protect groundwater. Enhanced inspection, record keeping and monitoring is required. Procedures for closure are also included and include capping, liners, and dewatering. The CCR regulation has since been subject to litigation.


title: Fly ash

text: Fly ash contains trace concentrations of heavy metals and other substances that are known to be detrimental to health in sufficient quantities. Potentially toxic trace elements in coal include arsenic, beryllium, cadmium, barium, chromium, copper, lead, mercury, molybdenum, nickel, radium, selenium, thorium, uranium, vanadium, and zinc. Approximately 10% of the mass of coals burned in the United States consists of unburnable mineral material that becomes ash, so the concentration of most trace elements in coal ash is approximately 10 times the concentration in the original coal. A 1997 analysis by the United States Geological Survey (USGS) found that fly ash typically contained 10 to 30 ppm of uranium, comparable to the levels found in some granitic rocks, phosphate rock, and black shale.


title: Fly ash

text: In 1980 the U.S. Congress defined coal ash as a "special waste" that would not be regulated under the stringent hazardous waste permitting requirements of RCRA. In its amendments to RCRA, Congress directed EPA to study the special waste issue and make a determination as to whether stricter permit regulation was necessary. In 2000, EPA stated that coal fly ash did not need to be regulated as a hazardous waste. As a result, most power plants were not required to install geomembranes or leachate collection systems in ash ponds.


title: Fly ash

text: Studies by the USGS and others of radioactive elements in coal ash have concluded that fly ash compares with common soils or rocks and should not be the source of alarm. However, community and environmental organizations have documented numerous environmental contamination and damage concerns.


title: Fly ash

text: Crystalline silica and lime along with toxic chemicals represent exposure risks to human health and the environment. Fly ash contains crystalline silica which is known to cause lung disease, in particular silicosis, if inhaled. Crystalline silica is listed by the IARC and US National Toxicology Program as a known human carcinogen.


title: Fly ash

text: Lime (CaO) reacts with water (HO) to form calcium hydroxide [Ca(OH)], giving fly ash a pH somewhere between 10 and 12, a medium to strong base. This can also cause lung damage if present in sufficient quantities.


title: Fly ash

text: Material Safety Data Sheets recommend a number of safety precautions be taken when handling or working with fly ash. These include wearing protective goggles, respirators and disposable clothing and avoiding agitating the fly ash in order to minimize the amount which becomes airborne.


title: Fly ash

text: The National Academy of Sciences noted in 2007 that "the presence of high contaminant levels in many CCR (coal combustion residue) leachates may create human health and ecological concerns".


title: Fly ash

text: Following the 2008 Kingston Fossil Plant coal fly ash slurry spill, EPA began developing regulations that would apply to all ash ponds nationwide. EPA published the CCR rule in 2015. Some of the provisions in the 2015 CCR regulation were challenged in litigation, and the United States Court of Appeals for the District of Columbia Circuit remanded certain portions of the regulation to EPA for further rulemaking.


title: Fly ash

text: EPA published a proposed rule on August 14, 2019, that would use location-based criteria, rather than a numerical threshold (i.e. impoundment or landfill size) that would require an operator to demonstrate minimal environmental impact so that a site could remain in operation.


title: Fly ash

text: In response to the court remand, EPA published its "CCR Part A" final rule on August 28, 2020 requiring all unlined ash ponds to retrofit with liners or close by April 11, 2021. Some facilities may apply to obtain additional time—up to 2028—to find alternatives for managing ash wastes before closing their surface impoundments. EPA published its "CCR Part B" rule on November 12, 2020, which allows certain facilities to use an alternative liner, based on a demonstration that human health and the environment will not be affected. Further litigation on the CCR regulation is pending as of 2021.


title: Fly ash

text: In October 2020 EPA published a final effluent guidelines rule that reverses some provisions of its 2015 regulation, which had tightened requirements on toxic metals in wastewater discharged from ash ponds and other power plant wastestreams. The 2020 rule has also been challenged in litigation. In August 2021 EPA announced that it is conducting another rulemaking to address the 2020 rule and strengthen wastewater limitations. The agency plans to publish a proposed rule in fall 2022.


title: Fly ash

text: The Ministry of Environment, Forest and Climate Change of India first published a gazette notification in 1999 specifying use of fly ash and mandating a target date for all thermal power plants to comply by ensuring 100% utilisation. Subsequent amendments in 2003 and 2009 shifted the deadline for compliance to 2014. As reported by Central Electricity Authority, New Delhi, as of 2015, only 60% of fly ash produced was being utilised. This has resulted in the latest notification in 2015 which has set December 31, 2017, as the revised deadline to achieve 100% utilisation. Out of the approximately 55.7% fly ash utilised, bulk of it (42.3%) goes into cement production whereas only about 0.74% is used as an additive in concrete (See Table 5 [29]). Researchers in India are actively addressing this challenge by working on fly ash as an admixture for concrete and activated pozzolanic cement such as geopolymer [34] to help achieve the target of 100% utilisation. The biggest scope clearly lies in the area of increasing the quantity of fly ash being incorporated in concrete. India produced 280 Million Tonnes of Cement in 2016 . With housing sector consuming 67% of the cement, there is a huge scope for incorporating fly ash in both the increasing share of PPC and low to moderate strength concrete. There is a misconception that the Indian codes IS 456:2000 for Concrete and Reinforced Concrete and IS 3812.1:2013 for Fly Ash restrict the use of Fly Ash to less than 35%. Similar misconceptions exists in countries like USA but evidence to the contrary is the use of HVFA in many large projects where design mixes have been used under strict quality control. It is suggested that in order to make the most of the research results presented in the paper, Ultra High Volume Fly ash Concrete (UHVFA) concrete is urgently developed for widespread use in India using local fly ash. Urgent steps are also required to promote alkali activated pozzolan or geopolymer cement based concretes.


title: Fly ash

text: Due to the ignition of coal deposits by the Siberian Traps during the Permian–Triassic extinction event around 252 million years ago, large amounts of char very similar to modern fly ash were released into the oceans, which is preserved in the geologic record in marine deposits located in the Canadian High Arctic. It has been hypothesised that the fly ash could have resulted in toxic environmental conditions.


title: M8 Armored Gun System

text: The M8 Armored Gun System (AGS), sometimes known as the Buford, is an American light tank that was intended to replace the M551 Sheridan and TOW missile-armed Humvees in the 82nd Airborne Division and 2nd Armored Cavalry Regiment (2nd ACR) of the U.S. Army respectively.


title: M8 Armored Gun System

text: The M8 AGS began as a private venture of FMC Corporation, called the Close Combat Vehicle Light (CCVL), in 1983. The Army began the Armored Gun System program to develop a mobile gun platform that could be airdropped. By 1992, the AGS was one of the Army's top priority acquisition programs. The service selected FMC's CCVL over proposals from three other teams. The service sought to purchase 300 AGS systems to begin fielding in 1997.


title: M8 Armored Gun System

text: The Army canceled the M8 AGS program in 1996 over the objections of Congress and the Department of Defense, due to the service's budgetary constraints. The Sheridan was retired without a true successor. The AGS never saw service, though the 82nd Airborne sought to press a limited number into service in Iraq. The AGS was unsuccessfully marketed for export, and was reincarnated for several subsequent U.S. Army assault gun/light tank programs. United Defense LP proposed the AGS as the Mobile Gun System (MGS) variant of the Interim Armored Vehicle program in 2000, but lost out to the General Motors–General Dynamics' LAV III, which was type classified as the Stryker M1128 Mobile Gun System. BAE Systems offered the AGS system for the Army's Mobile Protected Firepower requirement, but lost to the General Dynamics Griffin in 2022.


title: M8 Armored Gun System

text: The Army recognized the poor performance of the M551 Sheridan light tank in Vietnam and, in 1977, began the process of retiring the vehicle. A small number were retained in active service by the 82nd Airborne Division and the National Guard. The Army designated the M3 Bradley cavalry fighting vehicle to partially fill the Sheridan's role.


title: M8 Armored Gun System

text: In the 1980s, the United States Army began looking for a more capable replacement for the Sheridan. During this time, a string of Army projects to update or replace the Sheridan were begun, but all ended without the Army committing to buy. Some of its efforts around this time could be described as hopelessly intermingled.


title: M8 Armored Gun System

text: In 1979, Army Chief of Staff General Edward C. Meyer initiated a transformation of the 9th Infantry Division that would see the light infantry division assume many of the characteristics of the heavy division through an infusion of high or emerging technology. The so-called "High Technology Light Division" would require the procurement of a Mobile Protected Gun, later called the Assault Gun System (AGS), and a Fast Attack Vehicle. The notional Mobile Protected Gun was to be armed with a kinetic gun, or possibly a missile, capable of defeating enemy armor. In any case, the service determined that it needed a more immediate solution for the AGS requirement. In 1985, the Army approved a U.S. Army Training and Doctrine Command (TRADOC) recommendation to field the TOW missile-armed Humvee in the interim. The TOW-armed Humvee proved to be an inadequate substitute for the AGS in the 9th Infantry Division as it could not fire on the move and was too lightly armored.


title: M8 Armored Gun System

text: In 1980, the U.S. Army Infantry School's Mobile Protected Gun project analyzed anti-armor weapons systems, concluding that the Army should equip its new light infantry divisions with TOW-armed Humvees and an unspecified 6×6 lightly armored vehicle armed with a 25 mm caliber gun. This led the Secretary of Defense to direct the Army to use the LAV-25 for this purpose. In 1981, the Army joined the Marine Corps's Mobile Protected Gun System program. The MPGS was canceled the following year. The basic chassis of the Sheridan was considered to be in good working order even if its problematic 152 mm caliber gun/launcher was not. Both the Marine Corps and Army explored re-gunning the Sheridan with a conventional gun. In 1983, the Naval Surface Weapons Center mounted a 105 mm cannon to a Sheridan. One Army plan also envisioned re-gunning a few dozen Sheridan with 105 mm or 120 mm cannons, but this project was canceled in 1985.


title: M8 Armored Gun System

text: After the cancelation of the MPGS program, the project morphed into the Armored/Assault Gun System. In 1983, the Army established the AGS program. In 1985, Army Vice Chief of Staff General Maxwell Thurman approved an amended Requirement Operational Capability (ROC) for the Armored Gun System. Thurman recommended that the Army purchase 500 AGS systems. The Army Chief of Staff did not advocate for funding the program in Congress, however, given its low priority. Senate appropriators declined the Army's request for AGS funds for FY1986. The program office was disestablished, and the ROC retracted. In May 1986, the AGS program was re-organized under the Armored Family of Vehicles Task Force (AFVTV). During one concept study for a proposed All Purpose Fire Support Platoon, the task force shortlisted four candidate vehicles for an Armored Support Platform. These were the FMC Corporation Close Combat Vehicle Light (CCVL), the Cadillac Gage Stingray, the General Motors LAV-105, and the Teledyne AGS. The task force recommended the latter.


title: M8 Armored Gun System

text: In 1987, the Army tested a version of the LAV-25, designated as the M1047. The Army determined that these were unsuitable for LAPES, and with only a 25 mm caliber cannon, could not match the firepower of the Sheridan. Congress did not favor the M1047, though a few were deployed with the 3/73rd Armor of the 82nd Airborne Division in the Gulf War.


title: M8 Armored Gun System

text: In August 1987, the Office of the Secretary of Defense approved the AGS program initiative for 600 vehicles. A joint Army–Marine Corps program was mooted. The ROC was approved for the second time in September. In December, the AGS program was dropped as the $800 million ($ in ) plan was considered unaffordable. Around the same time, the Army Chief of Staff issued a "promissory note" to replace the Sheridan by FY1995.


title: M8 Armored Gun System

text: In September 1989, the Armored Gun System Project Manager office was reestablished at the United States Army Tank-automotive and Armaments Command and a marketing survey was distributed to industry. The Army formalized the AGS program in April 1990 with the issue of a new ROC.


title: M8 Armored Gun System

text: In November 1990, the Defense Acquisition Board authorized the Army to proceed with development of the AGS. The Army believed that replacing the Sheridan with an off-the-shelf AGS would be less expensive and provide more capabilities than an upgraded Sheridan. In addition to being expected to replace the Sheridan in the 3/73rd Armor, it was to replace TOW missile-armed Humvees in the 2nd Armored Cavalry Regiment (2nd ACR).


title: M8 Armored Gun System

text: In 1991, the Senate and House Armed Services Committees joined in directing the Army to integrate the turret and Watervliet Arsenal EX35 gun of the LAV-105 with an AGS chassis. A joint program was balked at by both services, who believed the two platforms were mismatched. Subsequently, the Marine Corps demurred and requested no further funding for the LAV-105. In any event, the proposed chimera was nixed by the Senate Appropriations Committee later that year.


title: M8 Armored Gun System

text: The AGS program had gathered steam by this point due in part to the back-to-back successful employment of the Sheridan in two overseas operations. In December 1989, Sheridans of the 3/73 Armor were airdropped into Panama as part of Operation Just Cause. This was the first successful employment of light armor in combat. In August 1990, Sheridans were airdropped into Saudi Arabia as the spearhead of the buildup of Operation Desert Shield.


title: M8 Armored Gun System

text: The Army issued a draft request for proposals (RfP) in May 1991. The Army published the RfP in August incorporating changes as a result of feedback from industry and Congress, the latter of which had directed the Army to require the EX35 gun. Army Acquisition Executive Stephen K. Conver became concerned that the AGS program was becoming laden with unnecessary requirements that would increase costs and development time, as well as limit the number of interested contractors. In view of this, in October 1991, Conver's office conducted a review of the requirements. The Army updated its RfP later that year, with submissions due in December. Following the deferment of the RAH-66 Comanche and Block III tank, the AGS was among the Army's top priority programs. After having earlier tried to kill the tank, appropriators grew to appreciate the program's relatively low price tag.


title: M8 Armored Gun System

text: In June 1992, the Army selected the FMC proposal. FMC was awarded $27.7 million ($ in ) to begin phase 1 work, including the production of six test units. The bids for this phase ranged from a high of $189 million ($ in ) for GDLS–Teledyne and a low of $92 million ($ in ) for Hägglunds. The procurement program was valued at $800 million.


title: M8 Armored Gun System

text: FMC began developing the Close Combat Vehicle Light as a private venture in 1983. The vehicle was designed from the outset to meet the Army's as-yet unfunded Armored Gun System requirement. FMC built two mock-ups. The first was a front-engine model utilizing a diesel engine. The second was a rear-engine model with a diesel engine and featuring more armor. In 1984, FMC validated the feasibility of pairing the 105 mm gun with a light chassis by test firing a 105 mm gun mounted on an M548. The first prototype CCVL was completed in August 1985 and debuted at the meeting of the Association of the United States Army in October. The CCVL was demonstrated at Fort Bragg in 1987.


title: M8 Armored Gun System

text: The Army did not originally require that the AGS be air-droppable by the C-130, believing that the requirement would deter submissions. Nevertheless, FMC's proposal claimed that this desired capability was possible with its design. After winning the contract, FMC made several weight-saving changes to the design, particularly the pallets, in order to meet the C-130's weight limit.


title: M8 Armored Gun System

text: In a December 1993 report, the Defense Department Inspector General cautioned that the AGS would be too heavy for low-velocity airdrop. The report said the AGS did not meet the Army's requirements for air mobility, and recommended delaying low-rate initial production until the airdrop requirement could be met. The Army strongly refuted the IG's report. The IG's concerns were put to rest in October 1994, when the service successfully airdropped an AGS from a C-130 at an altitude of 1300 feet.


title: M8 Armored Gun System

text: Citing cuts in procurement funding, in 1993, the Army cut its planned AGS order from 300 to 233. In 1994, the Army settled on an acquisition target of 237 vehicles. Of these, 123 would go to the 2nd Armored Cavalry Regiment, 58 to the 82nd, and 56 to reserves and training bases. The last 169 AGS systems, to be produced from 1998 to 2002, were to be built without the weight-saving modifications of those destined for the 82nd, which was the only unit that required an airdroppable AGS system.


title: M8 Armored Gun System

text: Six prototypes were built under the designation XM8. The first of these was rolled out at the United Defense (created by a merger of FMC and BMY) facility in San Jose, California, in April 1994, and arrived at Fort Knox, Kentucky, in April 1995. The last of these was delivered in May. United Defense provided five XM8 AGS systems to the service's Operational Test Command, which put the vehicle through five months of testing at Fort Pickett, Virginia. Another prototype underwent survivability testing at Aberdeen Proving Ground, Maryland.


title: M8 Armored Gun System

text: In 1995, the Army explored cutting the 2nd ACR, which would reduce the Army's buy to 80 AGS for the 82nd Airborne. In May 1995, the National Guard expressed interest in procuring the AGS for the 38th Infantry Division, 35th Infantry Division and 34th Infantry Division in order to help bridge the looming capability gap should the 2nd ACR be eliminated. This proposal was rejected by the service. In October 1995, the Army type classified the XM8 as the M8 Armored Gun System. It approved an initial production run of 26 vehicles, with an option for 42 more scheduled to begin in FY1997. A full production decision would be reached in 1997. Fielding to the 3/73 Armor would begin in 1999. All three squadrons of the 2nd ACR were to be fielded subsequently.


title: M8 Armored Gun System

text: The end of the Cold War had precipitated a fall-off in U.S. military spending. The President's FY1996 budget request allotted the Department of Defense (DoD) the lowest procurement budget level since 1950. The AGS was one of several systems that did not fare well in an Army review of anti-armor weapons then under development. Responding to budget cuts anticipated in the period FY98–03, in 1996 the Army adopted a new policy: Instead of distributing small cuts throughout many projects, entire programs would be canceled. Army Chief of Staff Dennis Reimer canceled the AGS in January 1996.


title: M8 Armored Gun System

text: Many officials felt blindsided by the Army's decision to kill the AGS. The Army's decision to cancel the AGS lacked a formal announcement, but was soon leaked to the press. This displeased some lawmakers including Senate Armed Services Committee chairman Strom Thurmond, who privately expressed irritation to Defense Secretary William J. Perry about having learned of the cancelation through media reports.


title: M8 Armored Gun System

text: Ten Representatives signed a letter urging Perry to continue on with the program. The letter touted the program's "tremendous success" in meeting the program's objectives, and noted that the vehicle was "well within budget and on schedule." The House appropriations national security subcommittee requested that the DoD pause the cancelation of the AGS pending a Congressional review. The subcommittee said that the AGS had met its milestones and "would be a strong candidate for increased funding."


title: M8 Armored Gun System

text: The Army belatedly sought to win Congressional and DoD support for its decision to cancel the tank. Securing the blessings of the Office of the Secretary of Defense would ensure that the service would not have to forfeit unspent FY1996 funds from the AGS program. The DoD, at least at first, affirmed its support for the program and called it "premature" for any service branch to draw any conclusions about the outyear funding environment. However, in February the Joint Requirements Oversight Council (JROC) endorsed the Army's decision. Despite JROC's recommendation, Perry withheld his support for canceling the AGS until he could personally meet with key congressmen. Perry's office said it would review the Army's plans for the $1 billion originally earmarked for the AGS before making a decision.


title: M8 Armored Gun System

text: The Army issued a stop-work order to United Defense in February. In May 1996, the Army Vice Chief of Staff formally announced the cancelation of the AGS. The service estimated killing the program would save the Army $1 billion. The service sought to reallocate unspent FY1996 funds from the AGS program on military pay, construction and modernization programs.


title: M8 Armored Gun System

text: In order to help offset the loss of capability caused by the cancelation of the AGS, the Army increased its requested funding for M1A2 Abrams and M2A3 Bradley upgrades, and accelerated the development of the Javelin missile. The Army considered a variety of plans to "heavy up" the 2nd ACR. The service added heavy armor to the 2nd ACR and requested funding to purchase Apache helicopters. In the 82nd Airborne, the Army also planned to introduce the EFOGM missile and considered more widely fielding the Javelin missile. Funding for EFOGM was deleted in 1998. The Army also considered the Humvee-mounted MGM-166 LOSAT missile, another platform offering similar capabilities for the 82nd Airborne. However, this program was canceled in FY2005.


title: M8 Armored Gun System

text: The 3/73rd Armor was inactivated over the following two years. The last Sheridans in service were vismod Sheridans used for opposing force training. These too were retired in 2004. Maintaining the Sheridan was not thought to be practical. In place of the Sheridan in the 82nd Airborne, the Army stood up an Immediate Ready Company of Bradley Fighting Vehicles and M1A1 Abrams tanks from the 3rd Infantry Division which were to be attached to the 82nd.


title: M8 Armored Gun System

text: In 1998, the Senate Armed Services Committee proposed using the M8 AGS as a surrogate vehicle to evaluate "strike force experimentation activities" in the 2nd Cavalry Regiment.


title: M8 Armored Gun System

text: United Defense LP (UDLP) proposed the AGS, as well as a version of the Mobile Tactical Vehicle Light, for the Mobile Gun System variant of the Interim Armored Vehicle program in 2000. United Defense provided an AGS armored in level 1 and 2 for a platform performance demonstration from December 1999 to January 2000. By then, the AGS had reached an advanced level of technological maturity, and thus UDLP said it could field its design almost two years earlier than the General Motors' LAV III proposal. The AGS lost out to the General Motors proposal, which was type classified as the Stryker M1128 Mobile Gun System. UDLP protested the award, alleging that the Army disregarded its own timeline requirements, and that the requirements had been crafted with a wheeled vehicle in mind. The General Accounting Office denied UDLP's protest in April 2001.