So, what I would like to do is to continue the discussion of the first course on linear algebra to discuss the notion of inner product space, okay. So let me start with the notion of inner product space. See the notion of vector space generalizes the concept of addition of vectors, scalar multiplication that one is familiar with after doing a course on two dimensional or three dimensional geometry. The notion of inner product allows us to generalize the notion of dot product of vectors, say which we have studied for two dimensional, three dimensional vectors. This also allows us to talk about angle between vectors when vectors are orthogonal in a general vector space. The notion of inner product also allows us to talk about the notion of a norm of a vector. Norm of a vector is informally the distance function. So norm, once you have an inner product you define a norm and through the norm you can define the notion of distance between vectors, etc, okay. So first we will discuss the notion of inner products. So let me start with the definition of an inner product. It is convenient to start with complex vector spaces to introduce the notion of an inner product. So I have a complex vector space. So the first notion is inner product and inner product spaces, okay. So I have V as C n, okay the space of vectors with n coordinates each coordinate is a complex number C n over C that is a usual notation V is C n an inner product on V, an inner product on a vector space. An inner product on V is a function, is a function which we will denote using these two brackets dot, comma dot. This is a function from the cross product V cross V to C. So in general it is a complex number. The inner product is a function on the cross product. The inner product on V is a function on the cross product. It takes complex values, satisfies the following. It is a function which satisfies the following conditions. First condition, okay I will call it 1, 2, 3, etc. First condition is inner product of X, X, this must be non-negative for all X and V. The inner product of X with itself must be a non-negative real number. That is the first condition. And as part of the first condition we also have inner product of X, X equal to 0 if and only if X is equal to 0. This is part of the second condition, okay. V cross V is something like a set of all X, Y, X and Y coming from V. This function in particular must satisfy this condition. That is the first condition. Second condition is if you look at inner product of X plus Y, Z, this must be inner product of X, Z plus inner product of Y, Z. It is like additivity with respect to the first argument. This must be true for all X, Y, Z in V. Condition 3, you look at the inner product of lambda X, Y. Look at the image of lambda X, Y under this function. This is, this must be lambda of the image of X, Y. This is true for all lambda in C and for all X, Y in V. That is my third condition. Condition 4 is inner product Y, X. The image of Y, X is the complex conjugate of the image of X, Y. This must be true for all X, Y element of V. These are the four conditions that an inner product on a vector space must satisfy. And for convenience we are taking this vector space to be the complex vector space. Complex vector space C n, okay. There are some names associated with these conditions. The first one is called positive definiteness. First one is positive definiteness. Positive definiteness of the inner product. It is greater than or equal to 0 and it is equal to 0 if and only if X is 0. So first property is positive definiteness. Second and third is linearity with respect to the first variable. 2 and 3 together is linearity of the inner product with respect to the first, we can say argument or the first variable. Linearity with respect to the first argument. We can understand why it is linearity. You have these two notions. Additivity and addition of vectors, how does it behave with respect to that? With respect to the first argument, similarly scalar multiplication, okay. Fourth one is called conjugate symmetry. Property 4 is conjugate symmetry. Property 4 is conjugate symmetry. In general an inner product is not linear with respect to the second argument. I will give an example, okay. But before that let us look at examples of inner products. But even before that let me tell you that a vector space, this notation we will adopt, a vector space V together with an inner product is called an inner product space and the notation for an inner product space will be usually V, this inner product. When the inner product is clear from the context we will not use this. We will simply say V is an inner product space when the inner product is clear, okay. So let us look at examples of inner product spaces. See what I have done is to give an example to start with V SCN, okay. I have started with V SCN. This definition can be given over a general vector space V, okay. But let us look at the first few examples. This will be over C N, R N, etc. So first example, let us take V to be R N. See if you go back to this example, you will see that no property of C N has been used. What I want is a complex vector space, okay. What I want is really a complex vector space. So I can replace this as well by a complex vector space, okay. So I will simply say R V equal to C N or any complex vector space. The property of C N has not been used. What I need is just a complex vector space or any complex vector space which can also include real vector space. So I look at V as R N. So this is a real vector space R N over R. That is what this means. So what is a usual inner product? Usual inner product for 2 or 3 dimensional vectors we will extend it to R N, okay. So let us take X Y in R N and the notation as before will be X equal to X 1, X 2, etc X N and only for convenience we are writing it as a row vector. So X is this, Y is Y 1, Y 2, etc Y N. If these are the coordinates of the vectors X and Y then the inner product on R N, this is called the usual inner product. We will define this to be summation I equals 1 to N X I, Y I, summation I equals 1 to N X I, Y I coordinate Y's product or component Y's product. This is the definition. Then you can see that this satisfies the 4 conditions listed here. First condition is inner product of X with itself will be summation I equal to 1 to N X I square. Each X I is a real number. So this sum is non-negative and each term is non-negative. So the sum can be 0 if and only if each term is 0. Each term 0 means X I is 0 for all I. So first condition satisfied. Second condition satisfied. We have verified. Look at X plus Y Z. The inner product is linear with this inner product is linear with respect to the first argument. In fact with respect to the second argument also, okay but that is not what we want. 2 and 3 are satisfied trivially. You can check 2 and 3. 4 is satisfied without the bar because it is a real space, okay. So this is one example. It can be a real space and I have a real inner product space. So R N with the usual inner product is an inner product space. So let us look at C N and introduce an inner product. Second example, V is C N as before X and Y will be represented by the coordinates X 1, etc. X N, Y 1, etc Y N. This time the inner product is defined as summation I equals 1 to N X I Y I bar X I Y I bar. This is the definition for a complex for C N. Now you will see why you need the bar here. By the way each coordinate here is a complex number. Y I bar means it is a complex conjugate, okay. Why do you need this? See if you just take X I Y I it will not be an inner product, please you take this as an exercise, little exercise. It will not be an inner product. For instance what is inner product X comma X? Inner product X comma X is summation I equals 1 to N X I X I bar, okay. That is summation I equals 1 to N mod X I square. Now this is the reason why you need the complex conjugate here. Now this is a sum of non-negative real numbers. So this must be greater than or equal to 0 and if it is equal to 0 then each since each term is non-negative each term must be 0 if it is equal to 0. If the modulus of a complex number is 0 then the complex number itself must be 0. So each X I will be 0 and so X is 0, okay. That is the reason why you need the complex conjugate here. I think I will leave it for you to verify that it satisfies the other 3 conditions, okay. So this is the usual inner product on C n. This is the usual inner product on R n, okay. Okay maybe I will just write it down. This inner product the above inner product inner product is referred to as the usual inner product or the standard inner product on C n, usual inner product or the standard inner product on C n. We can do a little more general for the third example. We can do a little more general than what we have done for C n. We can take n positive real numbers. Let T 1, okay I will call it W 1, W 2, etc W n be positive real numbers. I have n positive real numbers for X Y in C n. I can define an inner product with respect to these numbers, with respect to these numbers. This is another inner product. So I will call it maybe inner product W, inner product with respect to W. W denotes the set of numbers W n, etc W n each of them being positive. So this inner product is just an extension of the above. It is summation i equals 1 to n. Use these positive real numbers. These are called weights. Use these positive real numbers and then define as before X i Y i bar. These are called weights. The rest is as before. You need them to be positive in order for the positive definiteness of the inner product to be satisfied. In order for condition 1 to be satisfied, you need them to be positive not non-negative. Even if one of them is 0, it will not be an inner product. So you can verify that this is an inner product. This reduces to example 2 when each of the W i's is 1, okay. So this is more general than this. Sometimes we may use this. Let us look at other examples. These are for R n C n. Let us look at C n cross n, the space of matrices. My fourth example will be the space of matrices. V is C n cross n. So C n cross n is the complex vector space of matrices of order n by n. Complex vector space means that the entries of the matrix are complex numbers. So what is the inner product? What is one possible inner product on V? So let us take AB in V. Let us recall the notion of the trace. The trace of the matrix A. Let us say it is denoted by T R A. Trace of A is defined as, see it is a square matrix is defined by, we have seen this definition earlier. Trace of A is summation i equals 1 to n A ii where the notation is A is A ij. If the entries of A are denoted by A ij then I look at the sum A 11 plus A 22 etcetera plus A n n that is the trace of the matrix. This is a linear function for A star. This is A bar transpose. A star will denote A bar transpose. By A bar I mean the complex conjugates of the entries of A and then I take the transpose that will be denoted by A star, okay. What is the inner product? Let us define inner product of two vectors in V. Two complex matrices to be trace of AB star. So can you derive the formula for the trace of AB star in terms of the entries of A and B? If you are given the entries of A and B what is the formula for the trace? Can you make a guess? First, that is what you expect to happen. My question is what is the guess for trace of AB star? The answer is summation i equals 1 to n A ii B ii bar. Let us see whether that is correct. Given two matrices let us first compute the arbitrary element of the product. Let us say I use C and D. C is C ij, D is D ij. Suppose I want to compute the r as the component of the product C D. See I will assume C and D are in V, okay. So matrix multiplication is possible both sides. C D, D C both multiplications are valid. Look at C D. For the product C D let me calculate say r s component. What is the r s component of C D? Summation, C r k D k s, k equals 1 to n, okay. This is the r s component, okay. What is the r s component of AB star now? Summation k equals 1 to n AB star. For A I have C that is A r k B star. See it is the k as the component of B star. S k component of B. B, S k of course it will go with the bar, okay. Now I want to put r equal to s, okay and then I want to sum it over s, isn't it? I must sum it over s. I have put r equal to s. I have not made the appropriate change. I will call this s. On one side I have r and the other side I have s, okay. So this is the formula for the s s component of AB star. This is the diagonal element of AB star. I must sum all the diagonal elements. So what is the formula then? So I will write that here. Trace of AB star is double summation. I have used r and s but I will come back to the usual i and j. i equals 1 to n, j equals 1 to k, sorry, j equals 1 to n, A ij B ij bar, okay. So this is the formula. Please check this after going home. So this is the formula for the trace of AB star and so this is the final formula in terms of the entries of A. So please verify that this is again an inner product on this complex vector space V, okay. Now all these are finite dimensional spaces. Let us look at one example from infinite dimensional spaces, okay. Let us look at one last example coming from infinite dimensional space. One last example of an inner product space. Let us consider V as C 0 1, the space of complex valued continuous functions on the closed interval 0 1, the vector space of all complex valued continuous functions on 0 1, okay. We know that it is a vector space and we also know that it is an infinite dimensional vector space. It does not have a finite basis. For two elements in V, let us define the inner product by, so what is the most natural just integral, these are continuous functions so integrals exist. So simply look at 0 to 1, f of t, since they are complex functions you have to imitate what you did for the discrete case gt bar dt for f and g from V. Then remember the first one is as it is second one goes with a bar that is why this is conjugate symmetric that is it is not linear with respect to the second variable but conjugate line with respect to the second variable, linear with respect to the first variable, linear with respect to the first argument. But it is the first property which is important to verify, first property is inner product f comma f, see that is integral 0 to 1 mod f square dt. It is a non-negative function and we know from Lebesgue integration if you want that it is a non-negative function and it is 0 if and only if the integrand is 0. It is a continuous function, if the integral is continuous non-negative function mod f t square dt continuous non-negative function if the integral is 0 then the integrand must be 0, okay. So it is you need to use techniques from integral calculus in some cases to verify that certain inner products are really inner products. So please verify the other condition this is an inner product space V together with this is an inner product space, okay. So that is a quick review of the definition of an inner product and an inner product space. I want to move on to the notion of a non-linear space, okay but I will be interested in first norms which are induced by inner products, okay so let us look at the following. I have an inner product space let V be an inner product space the norm let us take an arbitrary element in V the norm of X denoted by this is defined by norm X is the positive square root of the inner product of X with itself the norm of a vector in an inner product space. So we are looking at the norm the so called norm induced by an inner product, okay is it well defined we are taking the square root of a number if you look at the inner product space the first condition you know that this is a non-negative number so and I am also taking the positive square root of this, okay. So this is a non-negative real number to begin with the norm of a vector is a non-negative real number, okay. So let me list the properties that this satisfies first property I will just write down. So norm of X is greater than or equal to 0 for all X and V suppose norm X is 0, okay that happens if and only if norm X square is 0 if and only if inner product X with X is 0 which happens we know if and only if X is 0, okay so this norm has this property something similar to the property of an inner product positive definiteness. What are the other properties I will list them in the form of a result let V be an inner product space then the following properties hold. Property 1 is look at norm of alpha times X norm of alpha times X is mod alpha norm X mod alpha norm X this is true for all alpha in C and for X in V condition B look at the inner product of modulus of the inner product of X with Y this is less than or equal to norm X into norm Y this is true for all X Y in V this is called the Cauchy-Schwarz inequality which you may have encountered in some other context this is called Cauchy-Schwarz C H inequality, Cauchy-Schwarz inequality connecting the inner product and the norm it is an inequality. Property 3 is norm of X plus Y is less than or equal to norm X plus norm Y for all X Y in V this is property 3 this is called triangle inequality triangle inequality, okay let us prove this quickly see this is a defining equation for the norm the defining equation for the norm is this and in probably all the cases we will take norm X square as inner product of X with X and prove all these. So let us start with the first one consider norm alpha X the whole square by definition this is inner product of alpha X with itself for the first one alpha comes out for the second one it comes with a conjugate alpha alpha bar mod alpha square norm X square on the left I have square of norm alpha X I can take the positive square root because this is norm is non-negative modulus is non-negative again norm is non-negative I can take the square root to get norm alpha X to be mod alpha norm X that is the first property okay then Cauchy Schwarz inequality consider the following we have for all lambda in C for all lambda in C from the inner product we have 0 less than or equal to X minus lambda Y comma X minus lambda Y first property of the inner product apply to the vector X minus lambda Y for all X Y in B expand this using the norm. So this is equal to inner product X with X inner product X with minus lambda Y that will go with the conjugate minus lambda bar X comma Y this term minus lambda Y X the last one will go with the lambda lambda bar that is mod lambda square mod lambda square norm Y square okay I can rewrite the first one and call it norm X square that is what it is so this is non-negative let me call alpha as the number lambda bar X comma Y alpha is the number complex number lambda bar X comma Y then the second term is alpha bar I mean the second term is alpha the third term is alpha bar okay. So this right hand side let me go to the other board I think I will remove this now okay so what I have is 0 less than or equal to norm X square plus so let me take the term corresponding to Y mod lambda square norm Y square that is the last term and club the other two it is plus 2 times alpha plus alpha bar okay where alpha is lambda bar X Y alpha is a minus 2 times is that okay both go with the minus sign Y 2 there is no need for 2 yes but alpha plus alpha bar that is the real part 2 times the real part so this is equal to norm X square plus mod lambda square norm X square minus 2 time real part of alpha okay now this is true for all lambda I look at a particular value for lambda okay set lambda to be inner product X Y in this order divided by norm Y square okay if norm Y is not 0 that is if Y is not 0 let me rewrite if Y is not 0 Y equal to 0 okay so we need to consider okay we will come to that but that is very easy. So let us look at the case when Y is not 0 when Y is not 0 this number lambda is well defined for this lambda this inequality holds so what happens to this inequality let us just check that so let me call this 1 inequality 1 in this case becomes 0 less than or equal to norm X square plus mod lambda square this is modulus inner product X Y square by norm Y to the 4 and this goes together with norm Y square minus 2 times real part of alpha now what is alpha? Alpha is lambda bar X Y okay from the previous calculations alpha is lambda bar X Y what is lambda bar X Y in this case so let us make that calculation somewhere here what is alpha? Alpha is lambda bar X Y which is lambda bar is again modulus inner product X Y the whole square by norm Y square this is alpha which is a real number in fact a non negative real number so its real part is itself. So this term is minus 2 times so I will remove this minus 2 times modulus inner product X Y the whole square by norm Y square okay for this choice of lambda alpha is a real number non negative real number in fact so I get this inequality Y is not 0 so norm Y is positive I can multiply throughout by norm Y square of course this can be cancelled so this goes with 2 so I will have just these 2 so I am doing this here itself this simplification of cancelling norm Y square in the second term. Now I multiply throughout by norm Y square Y is not 0 norm Y positive inequality will remain so I get 0 less than or equal to I am multiplying throughout by norm Y square so norm X square norm Y square this term has a norm Y square in the denominator that vanishes plus this norm Y square will get cancelled with this I get a plus modulus inner product square minus 2 modulus inner product square that will go with a minus sign minus modulus inner product square. You push this to the left hand side you get and take the square roots which can be done because this is modulus square non negative this is non negative norm this is non negative so you get Cauchy Schwarz inequality okay so what is crucial is this choice of lambda let me prove the last one Cauchy I am sorry triangle inequality and then stop let us consider norm X plus Y the whole square this is by definition inner product of X plus Y with itself again expand this this is first term norm X square the last term norm Y square plus Y with X plus X with Y this is Z plus Z bar Z is a complex number 2 times real part of Z bar so this is norm X square plus norm Y square plus 2 times real part of X, Y but the real part of a complex number what is the relationship it is a real part of a complex number and the modulus Z equal to yeah alpha plus IB then mod Z square is alpha square plus beta square but alpha is less than or equal to modulus alpha is less than or equal to okay there is alpha and beta real numbers alpha less than or equal to okay all that I want to say is this is this clear real part of Z less than or equal to modulus of Z take the square root of this you get this so real part is less than or equal to modulus of that so this one will be less than or equal to maybe I can remove this okay so this real part is less than or equal to norm X square these two terms plus what did I write 2 times modulus of the complex number now apply Cauchy-Schwarz this is less than or equal to norm X square plus norm Y square plus mod X Y that is 2 times norm X norm Y but this is norm X plus norm Y the whole square what is inside the bracket is a non-negative number and this is a norm square so both are non-negative I can take the square root so norm X plus Y is less than or equal to norm X plus norm Y okay so that is the triangle inequality I remember that in Cauchy-Schwarz inequality I did not consider the case Y equal to 0 okay but it is trivially satisfied is not it if Y equal to 0 norm Y is 0 so this part is 0 and we know that X comma 0 is 0 we do not know that X comma 0 is 0 but you can prove that it is 0 so that is that is the exercise in any inner product space V the inner product of a vector with the 0 vector will be 0 inner product of X comma 0 is 0 that is not part of any of the conditions but you can prove it okay so in that case when Y is 0 this is satisfied trivially okay so let me stop here tomorrow we look at see we looked at the inner product that is rather we looked at the norm induced by the inner product we look at a general norm definition of a general norm just for completeness and look at the notion of orthogonal or the notion of orthogonality in a vector space and probably if time permits discuss the Gram-Schmidt authorization process okay so let me stop here.


This is the VOA Special English Health Report.  Others act sick to get work. For medical actors like Ted Bell, the stage is an examination room with a future doctor, nurse, or other healthcare professional.  He was describing the problem to a nursing student at the University of Maryland School of Nursing. Ted Bell was playing a school teacher. But in a way, he really does teach. He helps future doctors, nurses, and other healthcare professionals learn to work with patients.  He now works as what is known as a standardized patient. He stays busy working as one of about 700 standardized patients in the Baltimore, Washington area. Pay starts at $17 an hour. It can go as high as $35 an hour, depending on the project. Becoming a standardized patient does not require medical knowledge. The schools provide the training. Nor does it require acting experience. In fact, standardized patient Tom Wyatt is a professional actor. Yet he does not even think of his work with the students as acting. He says, I use some of the acting skills, but honestly, when it's going well, I'm not really acting. I am reacting. I'm listening to them and reacting naturally and honestly to what they're saying to me and what they're giving me. Standardized patients spend hours training for each of their performances. They have to remember the medical history of the person they are playing and be able to answer questions as if they were really sick. Tom Wyatt says remembering all the patients he has to play and their conditions can be difficult. Especially when I do, you know, sometimes nine or ten cases in a week at three different hospitals. So they're all completely different. After each session, the standardized patients talk to the students to discuss their performance. That is the performance of the student. For instance, he recently told one student nurse practitioner, the things that really stood out for me, your manner was extremely professional and you were in command at all times. You kind of took charge of the room. The students say they like working with medical actors and the actors enjoy it too. Ted Bell says the students find the experience very helpful and that makes him feel good. For VOA Special English, I'm Carolyn Presuding. Get more news and learn English at voaspecialenglish.com.


Item number SCP-915 Object Class Euclid Special Container Procedures All explorations of the interior of 915 must be documented, with a complete manifest of all personnel and equipment to be taken into 915. Declarations of intent to explore the interior or experiment with the computational abilities of SCP-915 must be declared one week in advance. No interior explorations can take place while the computational abilities of 915 are being tested. Also, no computation tests can be initiated while exploration or maintenance is taking place within 915. All interior explorations are to be limited to a period of one hour. Interior forage requires special dispensation from the lead researcher, Dr. Fowdry. All explorers are to be physically linked to a high-density nylon cord, which is anchored at a point outside 915. Standardized testing protocols of the specifications of 915 are to be applied to both 915 and a block of computers which are considered experimental controls. These control computers are specified as Model HP Slimline. These control computers are specified as Model HP Slimline S-3600F. Description SCP-915 is a mechanical computation device with a highly non-Euclidean internal configuration. It was the result of experimentation involving the effect of ██████ upon SCP-914. Despite appearing entirely mechanical, 915 completely replicates the capabilities of the input device, one HP Slimline S-3600F desktop computer. It appears that 915's exceptional topology makes these computational specifications possible. The current theory suggests that extensive alpocritic in space and time allows computations per second that would be associated with a mechanical device to be superseded. The exterior of 915 is a metal cube with sides of 1.3 meters in length. Plastic inserts can be found on all edges, presumably as a safety measure to prevent contact with sharp metal seams. One side of the metal cube is able to be removed, allowing access into the interior of 915. Opposite this access point is an articulated metal arm leading up to 915's display. This metal arm is composed of several pistons which have the effect of precisely changing the tapestry that is the primary element of 915's display. 915's display consists of a tapestry woven in an extremely dense fashion held inside a metal enclosure. Despite the density of the tapestry, it is still able to be manipulated by mechanical arms inside the enclosure to a high degree of precision. This precise manipulation is able to fundamentally alter the appearance of the tapestry in controlled ways. Note, due to its effects on RA915-A, continued research involving the knot theory at work in 915's display has been suspended. Dr. Faldry The interior of 915 is a massive gears and clockwork, as well as more esoteric mechanical components used in computation. A constant mechanical drone, as well as deeper sounds of grinding, can be heard within 915. These sounds all experience modulation and distortion, predicted to be the result of the non-standard topology 915 possesses. 915 maintains passageways through its interior, presumably to assist in the occasional maintenance of 915. When 915 requires maintenance, it will display a summary of the required repair, as well as displaying a map leading to the site within 915 where maintenance is required. The interior of 915 experiences constant shifts, making navigation very difficult. Further, maintaining radio contact is complicated by the topology of 915, often leading to delays of weakening of transmission only a few meters from the entrance. While some success has been accomplished using physical contact, such as high-density nylon cord, instances have been recorded where the cord has been severed, embedded in portions of 915's interior, or with portions seemingly curled back upon themselves with the ends somehow fused together. The interior is often unsettling to subjects and investigators. Many cases of disorientation, nausea, and fainting have been reported within 915. It is indeterminate how much of these symptoms are a result of the sensory corruption due to the non-euclidean nature of 915, and how much is the direct effect on humanity of exposure to locally non-flat spacetime. The internal configuration of 915 appears to be related to computations before and by the device, with more extensive computations requiring a larger degree of internal reorganization. The power source of 915 seems to be in falling air from the exterior environment. The source of this pressure gradient, and the ultimate disposition of the in-falling gas, is indeterminate at this time. See Appendix 915A Addenda 915A Team 915-J5 found the edge of the interior of 915. They described it as a great wall of blackness. They said it swallowed the light from their flashlights. But it seems more probable that there simply wasn't anything for the light to reflect off of. Further, the team describes an airy whistling as a wind from the interior of 915 blew out to the void. Is this a possible power source? Is the interior of 915 suspended in a large void, and it derives power from the pressure gradient between our atmosphere and its vacuum? Further investigation warranted, assuming we can find the edge again of course. Dr. Fowlery 915B Dr. Snorlison was recently lost within the interior of SCP-915 for over a month. Despite this, his body showed no signs of dehydration or malnutrition. However, other ancillary factors such as hair growth indicated he experienced several months of subjective time while within 915. Further investigation is warranted, however Dr. Snorlison is being reassigned and will not be available to experimenters for comment. 915C I've decided to release some of my assistant's research notes in light of recent events involving researcher number 915-C. Dr. Fowlery 915D In light of the investigation taken of the material related to research on this device, as well as further anomalous events originating in the interior of 915, research on 915 has been suspended at this time. It seems interactions with SCP-915 tend to fall into two categories. Most reject the non-Euclidean geometry that 915 displays, ending with a surface appreciation of these traits and mental equilibrium intact. However, a few cases have emerged of researchers and agents internalizing their experience with the 915 in a way detrimental to their mental health. Further, it appears intimate knowledge of the workings of 915 may allow one so affected to induce preternatural effects in one's environment. We have taken steps to determine who is most susceptible to this damaging insight. While no concrete results have emerged, current evidence suggests that mathematicians and artists concerned with appreciation and understanding of space and shape are the most likely to internalize the experience of 915, Dr. Fowlery. Excerpt of the Personal Log of Research Assistant No. 915-G SCP-Involved SCP-915 September 12, 2007 The purpose of this first excursion is, well, to fix 915. Two weeks ago, 915 reported a need to replace Gasket Epsilon Druga, and printed a map of a portion of its interior in addition to necessary instructions to repair 915. The first impression I got of the interior of 915 is the noise. Voices, even when the source is within two feet, seem deadened. Inflation is lost, as though the air was somehow thicker. However, the operation of 915 produces a wide menagerie of sounds. Additionally, each sound seems strangely altered. It reminds me of that clip I heard in college. Lucifer is something. Annotation, I'm recalling Alvin Lucifer's I Am Sitting in a Room. Even the deep sounds that I think might come from large hydraulic action have a distinct buzz. There is also a very high-pitched hum that fades in and out. Mercifully, it's never very loud. It does play havoc with understanding what some of the team says, though. This excursion is considered a success. We followed the map precisely, and the Gasket was repaired. September 28, 2007 Now Dr. Felgery has his entering SCP-915 to wonder around. Technically, we've been mapping and cataloging portions of the interior of 915. We've used spray paint laced with a form of radioisotope to do the tagging. Felgery hopes that perhaps we can start to identify patterns in the geometry of 915. It's so relentlessly mechanical, perhaps the non-Euclidean following reciprocating cycles as well. October 1, 2007 We lost a member of the team. No one could quite explain how it happened. The team leader thinks we noticed it only a few seconds after it happened, but how can he be sure? At 1345, when we set up the ideogram, he was there. At 1352, number D-4605 reported that someone was missing. Her account wasn't correct. It was soon established that the missing party was number D-3354. The team leader immediately checked the nylon cord for cuts. There were none, despite the fact that number D-3354's connection point was missing. This is very speculative, but it almost seems the cord would fold it back on itself in extra dimensional space so that the portion of the cord containing number D-3354's connection point was guess the best way to put it would be… butt it off. The team leader had us leave the interior of 9-1-5 once we established the nylon cord was intact. Surprisingly, it only took 10 minutes of travel time to reach the entrance. Also, the system we put in place seemed to be subverted by 9-1-5's internal geometry. Each member of the team is equipped with transponders that constantly broadcast an IF-OF tag, and constantly keep track of each team member's IFF. The transponders of the team didn't stop receiving number D-3354's tag until 403. October 1st, 2007 All experimentations probing the capabilities of SCP-915 have halted for the time being, so rotating teams can conduct a 24-hour search of the interior of 9-1-5. That's all we get. Though the capabilities of 9-1-5 replicate every respect of modest Hewlett-Packard personal computer, the overseers wish to continue the test if 9-1-5 was capable of being coaxed to more performance. November 6th, 2007 Well, we finally found samples of a radio isotope. It's key to the number D-3354's can. The weird thing, though, is that it's not the Foundation-approved ideogram. Perhaps it's an attempt to communication on the part of number D-3354? The disturbing part is how childish the scroll looks. It almost looks like whoever made this with finger painting. I'm at a loss to what it means. We put each person exposed to the interior of SCP-915 through extensive psychological testing, and there's been no evidence of any intelligence reduction. November 10th, 2007 The fingerprints are not those of number D-3354. They are not of any Foundation employee. What? November 15th, 2007 We found a child's tea set. Well, we found what looks like a teapot in cups. They were made of gears. They were the table too. It looked like it was made of pistons and hydraulic chambers within an exterior wire mesh. We found a clockwork doll nearby, about one foot in length. It looks like it's been damaged or thrown. The arm is detached and there are a few places of damaged clockworks around where it lay. That was tea in the teapot. It was worn. The conclusion is starting to seem undeniable that, somehow, the interior of 915 had been subverted by either a group or individual unabiliated with the Foundation.


Welcome to this video from FilmsByChris.com. That's Chris Backe. I am Chris. And today we're going to be playing around with SQLite files, SQLite 3 files. This isn't really, this is part 4 of a series. If you're really interested in SQLite 3 databases, those first two tutorials are the main ones you want to look at. The last one was on using them in scripts. Today we're just going to be looking at the files. We're going to talk about it. This isn't really a tutorial, but more of just talking about SQLite 3 files. Basically you have lots of options out there when it comes to databases. And one of the most popular out there is SQL, which is done created by Microsoft. And then there's MySQL and SQLite. And when should you use these? Well, personal opinion, SQL, never, because one is made by Microsoft and it's proprietary. When it comes to the other two, there are times where you want to use MySQL and times where SQLite is a better option. And where would those be? MySQL is great if you're creating a web server with a web interface and you're going to have databases on there. It's really good, you know, as your databases get large. SQLite is great if you have an application, maybe a small database, again I've mentioned on your phone, if you're running an Android phone, I have no clue about iPhones and how they store stuff, but depending on what applications you use, your contacts or text messages, all that stuff, it's probably stored in a database on your phone and there's a good chance it's an SQLite database. And that sort of thing, small databases for applications on your local machine where MySQL is better for server stuff and web stuff, but also size. I read somewhere that the creators of SQLite say it's going to be a huge database. You do not want to be using SQLite. Once it gets big, it gets just not fast enough where MySQL might be a little bit faster. Commands between all three of these programs are pretty much identical, so if you know one, the other is just whatever application you're using to write to them. But I wanted to show you something really quick. Let's say you know absolutely nothing about SQLite databases and you want to get information from them, maybe you're just pulling stuff off your phone and you don't want to go in and install SQLite, maybe you're on a very light system and don't have it installed or you haven't installed, but you don't know how to use it. Everything is pretty much stored as plain text in there. So again, if I list out here, I have three files, one is script we made in the last video and then there are two databases and if I list these out, you can see one is a shell script, ASCII text and the other two are SQLite three files. Well, if I was to cat out one of those files, for example, example two dot DB, you can see some of our information in there. It's kind of hard to read and some of them might be a little messed up, but you have our entries in there. So again, if I was to run an actual SQLite three command, you can see this is what our database looks like and you can see some of that information in there. Not all of it, some of it's messed up and missing. But there is a command that is probably on your Linux system already. It's fairly common and I've talked about in the past, it's called strings. Whoops. And strings is great when you're backward engineering stuff to try to pull apart binary files because what it does is it ignores all the binary information and just shows you plain ASCII strings. So I can point strings at our example two dot DB and it's going to, not perfectly, but much clearly print out our database. So let's say, like I said, you pulled your contacts or your text messages off your phone and you're looking for a certain text in there. You're trying to find the date that it happened or something. Well, if you were to, if you knew SQLite commands, you can obviously open the app and search through that way. But if you didn't or you haven't used them in a while, it's very easy. You can do strings and then you can grep for it. So in this case, I can say like smith and it'll grab everything that smith. But another option, let's see how this looks. If you were to grep for smith directly to that file, you're going to get an error here, I believe, that it's a binary file. Well, you can actually grep through binary files by saying dash A. So dash A is saying that this is a binary file, just grep through the ASCII characters of that. But you still have that same problem of just cutting it out where it kind of, it's all on one line, it's kind of messed up. We're using the strings somewhat. Format's a little bit better in the case of these databases. So again, I just wanted to point this out that even if you know absolutely nothing about these databases, if you're familiar with what the string command does, which I just told you it does, it just brings out strings from files, whether the file's binary or not, examples two, example two, again like that. And then you can just grep what you're looking for. I can find Jack in there, and there's Jack's and his phone numbers. Again, not perfectly formatted, all columns are kind of pushed together. But that is a quick and easy way to look at these files. So I just wanted to bring that up because for me it's useful. Now, another thing I want to bring up about SQLite, let's say you did create a web server and you wanted to use an SQLite file, you could. I have done that. You can use PHP as a programming language to access these. You have to be very careful, though, about this because if you put the SQLite file on your server in a web directory and it's readable, well, now anybody who knows the URL to that database, which they might not be able to know because you do it with server-sized stuff, you may not know it. But if somehow someone was able to find it, it somehow came up somewhere, they can pull down the whole database with the URL HTTP request, either with Wget, Curl, or just through a web browser. So you want to make sure that it's either set through your, like if you're using Apache, you can say that this file is not accessible from these, or even better yet, don't put it in your web directory, I'll have it in another place on the server that is not part of your web server. That's something, now, if it's something that it's all information that you want publicly available and you might want people to download the database, like it's just public information that you're putting out there, and maybe you have code to display it properly on your web page, but you want to give someone access to download, that's great, because you don't have to do anything other than give an href link to it, and people can download it, and there you go. But definitely a security issue there, where if you're using MySQL, it's set up as a server, it's password-protected, knows these databases aren't password-protected, where your MySQL isn't in your web directory, it's a separate server, and when you're actually doing a request to it, it's actually using a whole other port to read, and you've got to log in with the username and password to access that information. So there are some thoughts. These SQLite databases are great for applications, where security may not be a huge issue. If you are doing it with something in security, be sure, be very careful about how you use it. Definitely bigger databases, and if you're doing a web server, MySQL, in most cases, is going to be a better option. Anyway, I hope you enjoyed this. Again, it's just more talking about how these work, places to use them, how to use them. Check out those previous videos if you want to learn more about the language in general. Very, very basic. You can actually get more in depth, but 99% of what you're going to do are those commands I showed you in the previous, creating database, creating the tables, inserting information, querying the information, deleting rows, and updating the information. So if you want to update, and of course, also altering if you want to add a column. But that's going to be 99% of what you do with these databases. And that's it. I do thank you for watching. As always, filmsbychris.com, it's Chris Decay. There's a link in the description. That is my website. Go there to search through my videos. I thank you for watching, and I hope that you have a great day.


good morning from Portland. Today's the day. Officially that I sell the bus here. Do all that red tape and paperwork. Knock knock. Knock knock. Who's there? Anybody ready to buy a bus? Let's do it. All right first stop we got to get this bad boy done for emissions. Looks like I got to pay 15 bucks. No big deal. And I think the dog slobbered on there. All right so we're doing a little emissions test here. We got to floor it. Get away from her signal. Pass or fail? What do you guys think? Comment below. I think we pass the flying colors. Although we did have to do it twice. It fell out of the tail thing. The thing that happens with the diesel is that the oil gets stuck in the turbo and then it blows out the pipe.  All right pass the emissions test flying colors. Dan the adventure bus is in great shape. Thanks a badge. Yeah, we're just gonna stop in this. They have these bizarre things in Washington where it's not even the DMV. It's like some licensing office. So we're gonna inquire within about how to sell it. Great news. Super easy. Basically I just bring in a little receipt after five days. Give him all the other stuff. And that's it. That's so easy. So easy. Great news. Everything's done. He's got insurance. They're my same lady. And he's keeping the bus life license plate and doing a Washington registration.  So we got them all squared away with that. We've got a couple stickers. What's up pups? What's up peppers? Just a heads up. If anybody is thinking about doing a bus conversion check out your local state to register it. Because some of them can be in big huge pain in the butt. And some of them are super easy. Some of them have permanent license plates and all that kind of stuff. So look on schooly.net and look in the forums and then call your licensing people because you could get yourself into a pickle. So I'm just thankful the state of Washington was like super chill. This year is the last year of a mission. So they you know yeah it's one of those states. So anyways how you feeling about this? Amazing. I'm ready to move in. I'm already moved in. Yeah. So anyways what you got? You got a couple stickers there? Yeah. Ready to make it mine. There you go. All right. Yeah let's do it and then I'll sign the bus. Boom. It's official. Right on man. Thanks so much. Thank you. Yeah. So today's the day. Yep stay there pup. Get back on. Clearly listened well. I'm gonna go for a spin in Brian's new adventure bus. Still got to take Dan off and dump the toilet some other stuff. But yeah I'm gonna go for his first spin in the bus and yeah he's got any questions or anything. That's what I'm here for. All right here we go. We're taking the first spin in Danny adventure bus. There's not too many people have driven this thing besides me. I think only like four. Glad to be the new driver. Me too. Me too. To my bus. Well it's not my bus anymore. There goes Brian's bus. So if you want to follow Dan everywhere he goes. He's gonna have a name change. I don't know what the name change is gonna be the bus. So give him a follow on Instagram. You can see where the bus ends up with modifications he does to it. And I know I will be reunited at some point in the future.