Johnny dollar. Well, now, how do you Johnny? This is real potato worldwide mutual insurance Well, I rep house dear old Memphis, Tennessee I find us down on God's green earth Johnny always was always will be and how when did you join the Chamber of Commerce? Yeah, what's it say isn't it just about time for your big annual celebration? Oh, you're too late Johnny cotton carnival is all over and done with for this year now You should have called me sooner. Well now why Johnny these fine people here in Memphis They'll never give us any trouble. What are you calling about? Oh trouble Johnny. Why don't you just finish telling me? I did I did Johnny this little problem I'm calling about happens to be over in the nearby town of Somerville Well now make up your mind Rip. What's it? Which is it a little problem or big trouble? Well now I suppose that kind of depends on just how you look at it Johnny. Look at what? Murder? Yes, sir. Radio brings you Bob Reddick in the exciting adventures of the man with the action-pact expense account America's fabulous freelance insurance investigator yours truly Johnny Dollar Expense account submitted by special investigator Johnny Dollar to the worldwide mutual insurance company Memphis office Following is an account of expenses incurred during my investigation of the stock in trade matter I was able to make an immediate plane reservation so expense account item one is seventy two seventy five airfare to Memphis Tennessee and by shortly afternoon we started circling for a landing over the big industrial city there on the eastern bank of Ole Miss Soon as I cleared my baggage at the airport I spent item two six and a quarter for a taxi in the Ripley Tito's office on Union Street near 3rd Taxi Johnny. Now why didn't you all just rent yourself a car at the airport? Well sit down. Thanks. I'll have my secretary get one for you.  What time? Right away thank you honey. You mentioned something about a town called Somerville. Yeah about forty forty five miles sort of east of him. What happened over there? Like I told you on the telephone Johnny murder. And the deceased is a client of ours named a Volny Beauregard Exum. That's a mouthful. That's three mighty fine old family names Johnny. Figures. Yes sir. And now early this morning his housekeeper found him laying over his desk with his head bashed in. Has the police over there any theories anything to go on? No sir not a thing. No fingerprints on that heavy and iron that was used on him. No clues of any kind. Nothing. So that's why I think maybe you ought to go over there and take a look around. How big a town is Somerville? Less than a couple of thousand I guess. I see. Now that used to be the heart of some real important plantation country. That's where the Exum money came from Johnny from Cotton. But by the time he got down to Volny Beauregard he was still living in the old plantation nice but most of the property around all been sold off. In other words old Exum wasn't worth very much money. And I'm afraid that's true Johnny. But he somehow managed to keep up the payments on his insurance. How much? Well face value at 35,000. I don't rightly know just where he got his living income from. Of course after the war and some of these fine old southern families had to sell off the land they made some investments and things. You mean the Civil War rip? I said the war didn't I? Go on. Well anyhow I don't really know where he got his living money except maybe from his kinfolk. Well that brings up the question of beneficiary. Those very same kinfolk Johnny only once he got left. Who are they? Well no wife or young ones of his own so let's see here on his policy. Yeah just a niece and a couple of nephews Johnny. Now let's see there's Clarabel Ockway Exum. You have her address there. Let's see. Let me use this scratch pad I'll copy the policy. Yeah go right here. And like you see she lives right here in town. Works in a five and dime I understand. And there's a nephew also named a volunteer Beauregard Exum. Lives down Corpus Christi Texas you see. All right I got it. Then there's other nephew named a co-pepper Van Buren Oberthalp right Van Somerville. Works at a real estate office. Although it beats me how he makes a living at it. Yeah that's all Johnny just those three. Okay in other words they're the only ones who will benefit by Exum's death. Well that's right Johnny but surely you don't think one of them could have killed him. Why not. Fine old southern family like that. Did he have any enemies that you know about. Fine old man like Bonny Beauregard Exum. Did he have many friends. Well no no I guess he didn't really kind of just kept to himself living out his days there on the plantation house. All along with just his pride just living out his days. Now you mentioned a housekeeper. Yeah well Miss Dollar Cato just did some day work for him. And don't you go suspecting her Johnny why she couldn't hurt a fly. Well you are a lot of help. Now maybe I better not suspect anybody huh. That's right. Well no what I mean to say. A thirty five thousand three beneficiaries. Yes sir. Equal. Yes sir. So maybe eleven twelve thousand a piece it's not very much. Well now I understand they'll share the rest of the estate too. What do you think that plantation is worth.  Ten thousands all. No idea what kind of money old Exum had to live on where it came from. No bank accounts and nothing Johnny even paid cash premiums on his insurance. I guess he didn't like banks and such.  Now one more question to the killer ran sack the house. Well no not that I know of. So maybe you better take a look huh. Yeah I think I'd better. We being the CBS radio network to be able to bring you on this station each week day the songs of Bing Crosby and Rosemary Clooney. In addition to the sparkling Bing Crosby Rosemary Clooney show we're equally delighted to present at the same time each week day. The assorted talents of art link letter the house party man Gary Moore and Derwood Kirby and the rousing Arthur Godfrey time. There's no business like show business and nowhere else such a fine sampling of same than on this blockbuster CBS radio network entertainment fest. The nicest thing about it is should you miss any or all of these great stars on a Monday you can catch right up with them the next day or any weekday or so minded. Remember nowhere else can you enjoy each and every weekday the Bing Crosby Rosemary Clooney show the conversational gifts of Gary Moore and his perfect foil Derwood Kirby. The kids comedy and cut ups of art link letters house party and the air of Glee with gusto that's a specialty of Arthur Godfrey time. Before driving to Somerville to look over the scene of the crime I checked up on Mr. Exum's niece Clarabel. I found her in the stock room of the five and ten where she worked. She was a thin one looking girl of about 30 with long black stringy hair badly set in a knot. It bobbed about the back of her neck as she talked in a high nasal voice that fairly set my teeth on edge. Excuse me while I set this box of ribbons. Sure. And if you want the truth Mr. Dollar I am just as glad as I can be that old Uncle Volney died. He was murdered Miss Exum. Well he's gone. But all sorry about this poor Mrs. Cato how poor Clarabel. I am too. I see. I'll take your word for it. Now this Mrs. Cato if she had money why did she work as a housekeeper. Oh just that if you ever go out to see him. How did his money come from Clarabel. Funny now where did the money come from. Poor useless answers. Little old Clarabel simply didn't know anything that might be helpful to me and didn't care. Except that is whatever money might be coming to him. Maybe the Exum family was smart and prosperous once. But if she was any criteria and they done mighty poorly in the last couple of generations. I knew this. If she had anything to do with her uncle's death. She'd probably have left signs all over the place. So I drove on over to Somerville to the Exum home. Or rather what was left of it. A hundred years ago it might have been a mansion. Now it was just a wreck. Two of the eight big columns on the front had fallen. And simply left there to rot away in the sun and rain. Windows were broken and stuffed with newspapers to keep out the draft. They hadn't been a paint job in twenty years at least. But little was left was cracked and peeling. The yard was nothing but weeds and moss. And a thick matting of leaves had never been raked from under the big trees that were hung heavily with Spanish moss. At the door I was met by a sergeant Aiken of the local police. We're glad to see you Mr. Johnny. At Mr. Teeter from the insurance company phoned you'd be here. Come on in sir. Thank you Sergeant. I'd like to see just where and how Mr. Aiken was murdered. Yes sir. Right in here in the library. Only I guess the old man must have sold off all his books a long time ago. Now here sir. You see here he was kind of sprawled across the desk there. What's left of it. With that tin box by him pried open. Where is the body now. It's in town for the autopsy him being all alone when he was murdered. His housekeeper wasn't him. She's the one come in early this morning to do her work and found him laying here dead. I see. Go on. Well it's all pretty obvious Mr. Johnny.  What was in it. May I touch it. Well as well. We couldn't find a single fingerprint on it. Not even Mr. Aiken. No prints at all. No sir. No prints at all. Chief he knows about them things he went around with a kit for prints dust and everything.  Yeah must have been real careful. I see. Even this heavy and iron he used to kill him with. Chief even checked the door knobs everything else for prints. Any idea then how the killer might have got in. Chief and I have been through the place with a fine tooth comb Mr. Johnny. You asked me the old man must have let him in. When. Doc says he's killed sometime late last night. Late. Yes that's right. Well then what I've heard about Mr. Exum it had to be somebody that he knew pretty well. Yes sir. But trying to find anybody he knew that well this old recluse. Anybody he'd let in at night. Well. The chief had a couple of boys working on to it but I don't see how it's going to come up with anybody. Any idea what might have been in this old tin box. Well probably whatever money the old man had on hand. Where'd he get his money Sergeant. Now that's a good question Mr. Johnny. I know he never had any bank accounts but he would cash check now and then. If he had no account I can't. He never sold any real estate for the last twenty five years. Didn't have any sales except except this old place here. Now this box certainly couldn't hold enough to keep him going for. Wait a minute. What's this. Looks like a couple pieces of paper stuck there in the hands. There's a corner or something torn off. See if I can get it out without more tearing. And corners weren't tore off of any money. That's for sure. No. Now this looks like. Sort of parchment paper that's used for an insurance policy. Or maybe. Maybe that's where his money came from. What do you think I have Mr. Johnny. Two possibilities Sergeant. One the obvious one that he had a lot of money hidden away in some secret place around this house. Well now we we thought of that on the other hand if these torn off corners. Or torn to I believe that they mean what I. I listen as a nephew living right here in Somerville isn't there. Yes it is big enough to have wielded this heavy and iron so effectively. What's it certainly Clara Bell couldn't have done it. Mr. Johnny you're talking about his own.   Well that that nephew on his mother's side. That cold pepper Oglethorpe living here in town. I mean one supposed to be working at real estate but he ain't. Kind of he ain't doing anything all he ever got was from his from his uncle. Go on Sergeant.  Where is he. Of course I suppose. Most anybody kills for money. Where will I find him. And you know none of. None of them three had any use for old Nixon. And only only one of the boys could use this. It's heavy and sergeants and with cold pepper the only one of the boys near enough to do it you know. All right where is he. What. All I said was all come on sergeants no no sure Mr. Johnny. Cold pepper didn't do it well how do you know how can you be sure. Well it seems he had some trouble a couple of weeks ago pulled a pull the knife on a man. And then he is the type he may be the type. Mr. Johnny but. Ever since he's been locked up in jail. Still is. Oh yes. A frustrating case this one. There was nothing I could really put my finger on. The Somerville police were doing just as much as I was and were accomplishing just as much. Nothing. What about the other nephew. Who also bore the name of Valny Beauregard Exum. Rapid mention that he lived in. Corpus Christi. Down in Texas. Yes sir Mr. Johnny five six years I'd say. What does he do on that side. Well I don't know that sir how I know is he had a fight with his uncle Wines. Mr. Exum gave him money to get out of town so he did. He hasn't been back. I wonder when I phoned him there in Corpus this morning told him what happened. He said he was sorry that he couldn't get down here. He was pretty tired up but he he'd be glad to pay for a. Decent fuel. Sure he would. Because of these torn off corners of paper what I think they are. Yeah it looks to me like young Volny Exum is the only one that's any good of them three. Yes sir. I mean if he can afford a nice funeral for somebody. You bet he can. Now listen Sergeant maybe I'm all wrong in playing a hunch that one of his relatives killed the old man but it's all I've got to go on. I'll say this Mr. Johnny. A hunch is no kind of proof. I know I know and proof is what I need. But even without it I'm going down to Corpus Christi. I believe me I'll be the first to admit it. To admit that luck sheer luck is what helped me to solve this one. It came by way of a pile of letters just inside the mail slot by the front door. On top was an envelope with a familiar company name across the upper left hand corner interest state telephone company. Before the sergeant could stop me I tore it open. And sure enough a dividend check for two hundred and fifty dollars with interest state telephone paying fifty cents a share and I know because I own some of that stock myself. Here was a dividend on some five hundred shares of a forty thousand dollars worth. All right. Expense account item three after a mad drive back to Memphis fifty one fifty plain fair to Corpus Christi. It was late by then. So item four is twenty two dollars even and that includes a cab into the Robert Driscoll hotel cocktails and dinner and my room bill for the night. First thing in the morning and a brokerage office on Lawrence Street I was talking to my old friend Wayne Stocksworth. Well to answer them in order Johnny I'm fine thank you. And I do think ours is the biggest stockbroker's office here in town. And yes we do have a client by the unlikely name of all name Beauregard Exum. But it's a very small account. Is he a young fellow when. Oh I'd say. Somewhere in his 30s. He's been my customer about five years now. Does he own much in stocks. Wayne I have got to know does he buy or sell in lots of a hundred five hundred shares at a time maybe. Exum. Now look Johnny I mean you know how it is. I know how it is a client's business is confidential. Why don't you ask him. What he called a little while ago. Seems that he has some old securities that he wants to cash in. And he. Wait a minute comes now. Interestate telephone. Well that's right. The world you haven't. Right over here. All right now I'll sit over here at this other desk. Pay no attention to me. Johnny I don't understand. Morning Mr. Exum. Morning Mr. Stocks. Sit down won't you. Thank you sir. Now these are the two certificates. You want to cash in. Yes sir. I just signed these over to us. Sign right here if you will I believe there's a little ink in that pen. Right here sir. That's right. That's quite a bit to sell all at once. I know I know. I must say I didn't realize that you had this sort of. I want to cash for these Mr. Stocks here. All in cash. I got to make a business trip maybe gone some time. Well I don't know Mr. Exum. Let's see this would come to over 40,000. Now look here sir I'm an old customer. Yes I know that's true. So here you are just get me the cash and I'll be on my way. Don't bother Wayne. What Johnny. I said don't bother just call a policeman. Who are you sir. Call a cop Wayne. These signatures are forgeries. What are you talking about. You're trying to say that I ain't. That I'm not Balney, Beauregard, Exum. You tell them Stocks. This is Balney Beauregard Exum. Sure it is Wayne but these signatures are forgeries. You're crazy. They were stolen from his uncle up in Memphis also named Balney Beauregard Exum and they were stolen from him when this man murdered him. Murdered him. You. You think you can prove that. I can prove it Exum. Now listen here. With two little pieces of paper that you left behind in a tin box where your uncle kept these Stocks certificate. No I didn't leave any. Do you see how these corners tore off it perfectly on these certificates. I thought I took everything out. You mean after you killed him. Yes I know. Let me out of here. Stop him Johnny. Stick around. Exum. You want to call the police now Wayne. Yeah. What Exum didn't know of course was that Wayne would have been a lot of investigating before handing over all that money. Inspired of the way that he'd carried a small account of the firms set things up for the murder and robbery. Expense account total including the trip back to Memphis and then back to Hartford. We'll call it three hundred and twenty five even. Yours truly Johnny Dollar. What is our star to tell you about next week's story. Next week one of the cleverest rackets and jewelry that I ever saw over a million dollars worth. Join us won't you. Yours truly Johnny Dollar. Written by Jack Johnstone. Produced and directed by Bruno Zirato Jr. Musical supervision by Ethel Huber. Written our cast were Wendell Holmes as the police sergeant. Joan Loring as Clara Bell. Robert Dryden as Ripley Teeter. Mandel Kramer as Wayne Stockseth. And Ralph Dell as Volney Beauregard Exum. Be sure to join us next week same time same station for another exciting story of yours truly Johnny Dollar. Art Hanna speaking.


Peace be upon you all. I want to echo what was said before me and what will surely be said again after me and thank each and every one of you for taking out time to show your support to our community in these difficult times. Unfortunately, I think this is a reminder that no one, no community, no people, no religion have a monopoly on terrorism and violence. This is a human problem and we still are working on this so many millennia later. I wanted to share some reflections on the tragedy that took place. I can't help but think how our Prophet Muhammad, peace be upon him, would be troubled by this. In fact, I think this is very reminiscent of the very society to which he came. For those of you who don't know, he was born into a very tribal society where each group saw itself as an in-group and was threatened by an out-group. And the way in which each group saw ascendancy over the other were endless cycles of violence. The Prophet Muhammad, peace be upon him, being a lover of peace was very troubled by this. And he worked to fight against this blind tribalism because they were the tribe of so-and-so and the tribe of so-and-so by introducing a new phrase. It's the tribe of Adam, that we are all atomites, so to speak. So the human family should trump this. And I believe that this is a framework by which we can find healing, God willing. That when we remember that we all come from the same two parents, that there is no in-group and no out-group, we are all one group, God willing great things can happen. Unfortunately, those two parents have two famous children that we've heard quite a bit about, Cain and Abel. And so we see that this is a human problem when one is threatened by what they see as the ascendancy of the other, what the human being can do.  And so therein we have, through that lesson and the life of the Prophet Muhammad as Muslims, the answer to this problem, which is these cycles must be broken. And the Prophet Muhammad, peace be upon him, worked within his context the way his brethren of the Prophets from before, whether Jesus or Moses or Noah, worked to break these cycles through forgiveness. When he was given victory over the people who had fought him tirelessly for over 20 years, and he had the upper hand in terms of the power, he asked him what do you think I will do today? And they said you will do what victors do, which is to kill, to slaughter, to take vengeance. And he said no, today is a day of forgiveness. I say to you what Joseph said to his brothers, there is no blame upon you all after Joseph's brothers did this. And so I feel like this would have troubled the Prophet, peace be upon him, very deeply, that here we have the human family still not healing from these wounds. And so we have to promote what has been called by one of my teachers a social mercy movement. And these cycles have to be broken with forgiveness and compassion. Even those who fight us, we have to see them, we have to view them with compassion.  And maybe this is what pushed this man to that. He does this in the footsteps of the Prophet Muhammad, peace be upon him, and all of the prophets. So we have to see humanity and all. There is no in-group, there is no out-group. And I want to again think all of you for coming here today, our brothers and sisters in humanity, to come and show us the great side of humanity. These tragedies have a silver lining and we're looking at it right now. We come together, there is much beauty within us, there's much beauty in the world. And this reminds me of the great Pope of Martin Luther King in which he said, darkness will not drive out darkness, only light can do that. Hate will not drive out hate, only love can do that. May God fill our hearts with love, compassion and forgiveness. May he give the families of those affected and all of us because it is our family, the patience and the wisdom to learn from this and the courage to heal the darkness and the pain in this world. Thank you.


Govdjo. I'm Maria Pinale Mungeli, I'm affiliated with Politechnico di Milano, Department of Architecture, Built Environment and Construction Engineering. As requested, the first slide is a very short presentation of the, my research group, and which is made up of the person listed there, profesor, reserčer, asocijator, P.H.D. studenti. Sreče imamo našeljne koalaboracije, tudi v universtriju Udine in Vydivstar, in v Parisu, kaj sem tudi srečen, tudi srečen srečen srečen. Tukaj tukaj tukaj tukaj tukaj tukaj tukaj tukaj tukaj tukaj vseči je kvalitavno zelo, da je naša zelo, ter je zelo, da je stavila seboj, da je vzelo, da je vseči vseč i kultura, da je vseči vseči in vseči vseči. V nekaj roli smo povalili vsišenju zelo, da povali seboj zelo, da sem bilo povali sve, da se te bljenje povali, na odličenju. Našljena je zelo, da je točnja, začal je, da je zelo, da se odličenja je odličenja. Zelo je, da je zelo. Točnja je odličenja, da je zelo, da je zelo, da je odličenja ima vse skupne, vse skupne, da ne predlje, da ne predlje, da ima vse skupne, struktur. This change in the form shape of the structure will make the shape irregular at the location of the stiffness loss. The idea is to detect this irregularity by fitting the operational shape, the shape of the structure with a smooth function. We used a spline, a cubic spline function because it has a mathematical characteristic, which is called Gibbs Phenomenon, which makes the interpolation very bad, close to a curvature discontinuity, since the loss of stiffness and uses discontinuity of curvature, the interpolation with the spline function will become as much worse, as much higher is the stiffness loss. So we define the damage feature as the difference, sorry, out of point here. The damage feature is as the difference between the recorded, the deformed shape and its interpolation with the spline function. We can do this in terms of the total deformed shape, or we can do this in terms of operational deformed shapes, that is for each value of frequency if we work in the frequency domain. So here are some very nice operational shapes calculated for a numerical model, and for each of these we can calculate this error, and in order to have one value of the error for each location, we can sum up the errors for all the operational shapes in the frequency range of interest. So this is the basic idea of the method and the presentation of the damage feature. The problem is that, of course, this damage feature will exhibit variations even if there is no damage at all. This is due to some random sources, the usual random sources. So usually we may have three situations. Yesterday someone talked about that there are mainly three types of monitoring, short, periodical, and long-term monitoring. The main difference in the application of methods like this is that it is in the volume of data that are available. In a short monitoring we may have a test before in the original configuration and another test in the inspection phase. So we have a very limited amount of data, very limited amount of sample, and there is no way we can find the distribution of the damage feature nor in the original configuration, neither in the damaged configuration. If we have a periodical monitor, we may hope to find the distribution of the damage feature in the original configuration, but not in the damage, in the inspection phase, because in the inspection phase, for example, we have, when we need a prompt alert after a catastrophic event or even not catastrophic, an earthquake, for example, and we want to know if the structure is safe or not. We don't have the time, of course, to collect as many information as the one needed to find the distribution, probability distribution in the damaged configuration. So we have just a value, and in that case we have to define a threshold and say, OK, the structure is damaged if the threshold is exceeded, but what is this threshold? How can we fix this threshold? It would be nice to fix it basing on cost-benefit analysis, but for most civil structure is not quite easy to have a cost model to fix the threshold. In our application, we just fixed an accepted probability of false alarm, which is the area here. If the damage feature exceeds this threshold, this means that the probability that we give a false alarm is very low, and we fixed the value of the probability of false alarm that we accept. In which we have more data, of course, is the long-term monitoring. We may recover the distribution of the damage feature, both in the undamaged configuration. In this case, we can estimate both the probability of false alarm and the probability of missing alarm. That is the probability that we don't give an alarm and the structure is damaged. In that case, we can fix the threshold as a tradeoff between the two values of the probability. Very quickly, we applied this method on a lot of numerical models because, as was just said, there are not many data available on really damaged structures, but also on a really damaged structure. This is the bridge in Italy, the Donio Bridge, which was artificially damaged with progressively increasing severity by cutting the slab, as you can see here, cutting the slab at the beginning at half of this section then all these sections and so on. Here are the results of the application. Vibration tests were carried out in the original configuration and after each damaged state. Here you can see the results of the application of this method. The circle, the location is the one of the damage and the bars here are the values of the damage index, the damage parameter. That is the variation of the interpolation error. For the lower intensity of damage, we have some false alarms, but for the higher intensity of the damage, the localization is quite clear. In the last damaged scenarios, they induced damage also in another section, this section and also in another section close to the other one. Actually, the method finds the damage in a section at the middle between the two. Also, we tried to apply the method by considering as the original configuration the one with the damage is just one section and the method was able to find the damage at the other section. Considering that here we had very few data, we adjusted data, one set of data in the original configuration and one after each test, the damage scenario was a very good result. This is another application, but it was carried out on a numerical model of this bridge for which we simulated several damage scenarios. In this case, we considered two damaged sections and the method works. Here is another application where we assumed that there is a permanent monitoring, so we assumed that we can recover, we assumed because this is a real instrumented structure. The factor building, which was instrumented by USGS, is densely instrumented. It has four accelerometer per floor, a tish floor. Actually, it is possible to recover the distribution of the damage parameter in the original configuration, but the damage scenarios were all artificially modeled by a numerical model because this building was never damaged. Also in this case, here you can see the blue bar is the real location of damage and these curves represent the damage parameter. The method finds always the damaged location, even if there is noise in the recorded signal. In this case, we investigated the capability of the method not to detect, but to follow the severity of damage. We found that actually the damage parameter increased with the severity of damage. There is certainly a link between the two, but at the moment it is not possible from the value of the damage parameter to recover the values of the loss of stiffness. The wish list, yesterday someone proposed to propose a wish list and I immediately borrowed the idea because I like it very much. The first is actually not a wish but a dream, I think. Now, because what I think is really needed for all this method of damage detection and this was just said by Geert, are data. A lot of data recorded on real damage structures because otherwise we will continue to check our models on our methods on numerical models and usually they work very well. They always work very well. The difficult thing is to let them work with real structures. So the dream is to have a living lab structure. Of course, this is not a dream for this course but can be an idea for future networking. Yesterday Dr. Wenzel was saying, we are here, we can propose something like that. A structure. A structure that we can monitor with any sensor we like. We can ask producers of sensors if they want to install their sensors. I think they will be interested because they can check the performance of their instrument sonarial structure and will be really a treasure for researchers to check their model. I am almost finished. Then another wish would be a cost model to define the threshold because one of the problems to define to say, okay, the structural damage, one of the ingredient, the main ingredient is the threshold, which has to come out from a cost benefit analysis. And then the last thing, yesterday the value was defined as the difference between the life cycle benefits and what this requires that we can model the structural performance. And these for structure suggested to fatigue may be possible, difficult ma possible. But if I think to imaginary structure subjected to an earthquake, these are really, really difficult things to do. So I think this will be one of the main problems to assess the value of structural monitoring for this kind of structure. Thank you.


So, now let us take the simplest mode in the cavity which is the TM010 mode. So, it is the fundamental mode in a PILBOX cavity. So, these are for the TM mode these are the fields here BZ is equal to 0 and then EZ has this value and from EZ you can calculate the values of ERE theta, VR and D theta. So, for TM010 mode M is equal to 0, N is equal to 1 and P is equal to 0. So, we put here everywhere M is equal to 0, P is equal to 0. So, we see that this goes to 0, this also goes to 0, this goes to 0. So, we are left with only EZ and B theta. So, we just have the EZ field and the B theta field. So, you can write from here you can put in the values of M, N and P. So, you will get B theta as minus j omega rc by h01 c square E0 j0 prime of h01 rc by r. And using the relation of the Bessel function that j prime 0 is equal to minus j1. So, we can write this we can write this in terms of j1. So, we have just two fields EZ and B theta. Also notice that they are so, this factor j here this tells us that they are out of phase with each other. So, when E0 EZ is maximum at any location B theta is minimum and so on. So, this is how the fields look like in the cavity you have the EZ field here it is maximum at the center and it has to go to 0 at the boundary because of boundary conditions. And B theta field is they form field lines around the electric field lines. So, EZ is j0 of the form of j0. So, if you plot EZ with r you see that it is maximum at the center and going to 0 at r is equal to rc. Similarly, B theta has a form of j1. So, it is 0 at the center and it increases like this as the radius increases. So, only EZ for a TM0 1 0 mode in a pillbox cavity only EZ and B theta fields are present. So, both EZ and B theta they have variation with r only. So, since m is equal to 0 and B is equal to 0 there is no variation in theta and z direction. So, there is variation with r only and the resonant frequency. So, you can calculate the resonant frequency from this formula you can put in the values of m, n and p in the formula for the resonant frequency. So, you see that it is independent of the length of the cavity it depends only upon the radius of the cavity and it is inversely dependent upon the radius of the cavity. So, higher the radius smaller is the frequency and so on. So, this is how the fields will look like. So, as I said it is a standing wave. So, that means the pattern is constant along various directions, but there is time variation and the time variation is like this. So, this is EZ field and this is B theta field ok. And since the electric and magnetic fields are out of phase with each other. So, you see that the variation in time is like this ok. So, you have a bill box cavity let us say it is in the TM010 mode and so, the electric field is like this there is of course, a magnetic field in the theta direction also, but it is 0 at the axis. So, let us say this is the axis. Now, the field variation with time is like this and we have already studied that how using this type of field pattern we can accelerate charge particles ok. So, we saw that we need not use the whole positive cycle for acceleration because the whole even though the whole positive cycle will produce acceleration, but there is phase stability only in this part. That means in your if you have to choose your synchronous phase between minus pi by 2 and 0. From 0 to pi by 2 there is acceleration in this region, but there is no phase stability. So, you have to choose your synchronous phase in this region. Also, you do not use the entire region for acceleration because then some particles will see a field that is 0, some particles will see a field that is maximum and there will be a huge spread in the kinetic energy of the charge particles which you do not want. So, you use only a small portion of the cycle for acceleration. So, let us say this portion ok. So, now the field in this cavity is changing like this. So, you want the particles or the beam to see just this part of the electric field. So, as the field is increasing you inject your beam bunch at the times and the phase of the field at the center here is 5 years. So, then the bunch sees this field it gets accelerated and it comes out. So, this length of the cavity can be adjusted accordingly. In actual practice the cavity is shaped to have to concentrate the electric field in the region near the axis. So, it is shaped like this to reduce this gap because we have already studied that the transit time factor depends upon the gap and how high an energy gain you get depends upon the value of transit time factor. Smaller the gap higher is the transit time factor. So, normally this is shaped the cavity is shaped like this to increase the transit time factor. So, as the field is increasing if you inject the beam bunch into the gap at the time when the phase of the field is 5 years it will see the right field and get the energy gain. So, electric field in the pillbox cavity for a TM010 mode is in the z direction it is constant along the z direction. So, along the axis of the cavity there is no variation in the electric field along the length of the cavity and the electric field has a sinusoidal variation in time. So, we inject the beam into the cavity when the phase of the electric field is 5 years and in this way we can accelerate the beam. Now, we can also have a long cylindrical copper cavity in the TM010 mode. So, instead of having just a small pillbox cavity we have a huge big pillbox cavity ok and you know that the frequency of the mode does not depend upon the length of the cavity. So, you can have a long cavity like this and inside that you put in the drift tubes ok and you adjust the distance from the center of center of one gap to the center of other gap as equal to beta lambda. So, that means the particle will move from here to here in time. So, again the field inside here. So, there is an electric field in the z direction. So, the field is increasing with time and you inject the charge particle in the first gap here at the time when the phase is 5 years here. So, it sees the right field and it gets accelerated and then for the remaining part of the time from here to here that means time t it spends inside this drift tube and then it comes out here and sees the right field again ok it sees the right field again and then it gets accelerated again. Again it spends the time time capital t inside this comes out here sees the right field and gets accelerated. So, in this way you can have you can have several drift tubes like this and you know that field cannot penetrate inside the hollow conductor. So, inside this the bunch or the particle beam will be shielded from the electric field it will see the electric field only in these gaps and get accelerated. So, this is the Alvarez type of structure and this is known as the drift tube linac or the detail. So, this is what was proposed by Alvarez. So, he said take these drift tubes and put this in a high Q cavity and use the electric fields associated with the electromagnetic waves. So, the electromagnetic waves are now forming mode inside the cavity and in the TM010 mode there is electric field along the Z direction ok. So, you can use the electric fields associated with these electromagnetic waves inside this cavity and use it now for acceleration. So, this is a picture of a drift tube linac these are the drift tubes. So, there are several drift tubes here. So, this is the beam hole through which the beam goes there are gaps between the drift tubes. So, the drift tubes shield the beam bunch from the undesirable part of the RF electric field and the beam is the beam is like in the transverse direction it tends to spread it is like a ray of light. So, the beam tends to spread in the transverse direction. So, it needs to be focused. So, just like a ray of light is focused using lenses here we have quadruples which we will see in future lecture they are used for focusing the beam. So, there are inside these drift tubes there are quadruples which are used for focusing the beam in the transverse direction. So, let us see an animation of the drift tube linac. So, this is the drift tube linac this is the tank these are the drift tubes. So, this is the beam it gets accelerated in the gap here and these drift tubes they contain magnets which is used for focusing the beam in the transverse direction. Okay. So, these boundary conditions so, when we said that the tangential component of electric field is 0 or the normal component of magnetic field is 0 this is assuming a perfect conductor. However, in real life we do not have perfect conductors we have good conductors and in good conductors the field penetrates inside up to a distance equal to the skin depth. So, the field penetrates inside the conductor so, this is the conductor okay and it dies down exponentially. So, the distance the field penetrates up to a distance equal to the skin depth and this depends upon the conductivity of the material. So, that is why in order to have low skin depth a high conductivity material like copper is used for making these cavities. And because the fields penetrate up to a certain skin depth surface currents will flow through the cavity material and this gives RF surface resistance. So, RF surface resistance is simply run upon the conductivity multiplied by the skin depth. So, because of this surface resistance now and the currents flowing on the surface of the cavity there is a power dissipated in the cavity. So, whatever power you are feeding into the cavity or whatever electromagnetic so, these electromagnetic waves that you put inside they carry power which is used for setting up the field in the cavity. So, you have a cavity so, you put in some RF power that is the total power part of the power is dissipated in the structure okay it is dissipated because the fields are penetrating up to a distance equal to the skin depth and there is some RF surface resistance. So, this part of the power is dissipated in the structure the dissipated power can be calculated from this formula. So, here it is half rs rs is the RF surface resistance and then taking the surface integral of h square over all surfaces of the cavity okay. So, this is this is how you can calculate the power dissipation then some power whatever power you are feeding into the cavity a part of the power goes to the beam. So, beam power can be calculated as the beam current into the energy gain. So, whatever is the energy gain in the cavity multiplied by beam current. So, beam is like a flow of charge particles and moving charge constitutes a current so, this is known as beam current. So, whatever power you are feeding inside the cavity part of it is dissipated in the structure and part of it is stored in the cavity which is used for acceleration and that is given to the beam. So, total power that is given to the cavity is the sum of the dissipated power and the beam power. So, this is how you power an RF linux. So, let us see you have a cavity this could be any type of accelerating cavity it could be a pillbox cavity or it could be a drift tube linux or any other structure okay. So, first you decide to what energy ranges you want to accelerate with charge particle and then you design the cavity. So, you decide what frequency you want to operate it at and then you get a source at the same frequency. So, if the frequency let us say you want to operate this in Tn010 mode at some frequency f0. So, you get an RF power amplifier which could be a klystron a solid state power amplifier or any other power source. So, at the same frequency. So, in other words it will give you electromagnetic waves high power electromagnetic waves at this frequency. You use a waveguide you know that waveguides can be used for propagation of electromagnetic waves. So, the electromagnetic high power electromagnetic waves produced here are propagated through a waveguide into the cavity. Now, if this frequency f0 matches the frequency f0 in the cavity of the Tm010 mode which depends upon the dimensions of the cavity then the field is set up corresponding to the Tm010 mode. So, that means you have electric field in the z direction. So, this you can use for acceleration. Now, if the power is coming at any other frequency. So, remember the cavity will not accept any other frequency it will accept power at the frequency of the corresponding mode only. So, if it is coming at any other frequency it will be reflected back. So, the power if it is reflected back it can go back and damage the RF amplifier. So, for that a device called circulator is put here in between the circulator is a one way device. So, it will not allow the reflected power to go back into the klystone it will direct it in another direction towards an RF load. So, this power now gets dissipated in the load. So, now if you are able to now if you are able to send in power to this cavity at the right frequency this power is all it all enters into the cavity and it sets up the right mode. So, you will have electromagnetic fields you have an EZ component here you have a B theta component here and this it has a time variation like this. So, some of the power will get dissipated in the structure and part of the power is going to set up these fields. When the beam comes here it draws power from these fields and gets accelerated and it gets an energy gain let us say delta W. So, power going to the beam is given by the beam current into delta W. Now, let us discuss some figure of merits of the cavity. So, while designing the cavity we have to optimize certain figure of merits. So, one important figure of merit is quality factor. So, this we saw we were seeing right in the beginning. So, Alvarez had proposed in order to solve the problem of the withdrawal in act where the so, in the withdrawal in act if you remember the voltage applied to the drift tubes there was direct voltage time varying voltage that was applied to the drift tubes. So, when you try to accelerate it to high energies. So, in order to keep the cell length reasonable you increase lambda you decrease lambda or in other words you increase the frequency and the structure started radiating. So, it did not store energy in the fields in between the gaps instead it started radiating energy like an antenna. So, to take care of that problem Alvarez suggested that you take these drift tubes and you put it inside a high Q cavity. So, this is the parameter quality factor high Q cavity and you use the electric fields associated with the electromagnetic waves in the cavity. So, what is the quality factor? The quality factor is defined as the ratio of these stored energy at any frequency the ratio of the stored energy to the power dissipated in the cavity. So, the aim of the cavity design is to maximize the value of quality factor. So, if you maximize this that means you are minimizing the power dissipation and you are maximizing these stored energy in the cavity. The stored energy in the cavity is given by this expression it is half Q0 integral over the entire volume of the cavity of x square and power dissipation we have already seen it is half rs and in surface integral of x square over all surfaces of the cavity. So, Q0 by putting these two in the expression for Q0 you can find out the value of Q0. So, you see that the volume integral comes in the numerator and surface integral in the denominator. So, it is the quality factor is high for a geometry for which the volume to surface ratio is high. The quality factor is also defined as 2 pi times the number of RF cycles it takes to dissipate the energy stored in the cavity. So, this expression here can be written as Q0 is equal to omega u and power dissipation is simply du by dt. So, from here you can write u is equal to Q0 by omega du by dt. So, from here you can get this expression by taking the integral of this you can get this expression. So, it means that if you store the energy in the cavity the energy stored in the cavity how long it takes if you remove the RF source how long it takes for that energy to dissipate. So, now as we have seen the quality factor is defined by this expression. So, now here if you notice rs is the RF surface resistance this is the only quantity that depends upon the material. Other parameters are all geometry parameters they do not depend upon the material properties. So, we define a parameter g which is Q0 into rs. So, we multiply this quality factor by rs and we get a parameter which is now independent of the material properties. It now this depends only upon the geometry of the cavity. So, this is known as the geometry factor. The next figure of merit is the shunt impedance this is a figure of merit that is independent of the excitation level of the cavity. So, it measures the effectiveness of producing an axial voltage v0 for a given power dissipation. So, it is v0 square the voltage axial voltage in the cavity divided by the power dissipation. So, it determines how much acceleration one gets for a given power dissipation. Then you sometimes define the effective shunt impedance because we are more interested not in knowing just the voltage, but the energy gain in the cavity and energy gain depends upon voltage multiplied by the transit time factor. So, energy gain is determined not only by the voltage it is also determined by the transit time factor. So, the peak energy gain of the particle it occurs when phi is equal to 0. So, peak energy gain because here the field is maximum. So, let us take phi is equal to 0 and then we multiply rs with t square. So, you are multiplying here v0 t square. So, this is rs into t square this is the effective shunt impedance. Then for long structures we are interested in knowing the shunt impedance per unit length. So, you simply take the shunt impedance and you divided by. So, you have the shunt impedance and divided by the length. So, this will give you the effect the shunt impedance per unit length. So, this is equal to v0 square by the power dissipated n. So, this can be written as v0 square you can write this as e0 square l square p l. So, this is equal to v0 square p by n. So, the shunt impedance per unit length is often useful for long structures and similarly you can have effective shunt impedance per unit length. So, you can just multiply z with t square. So, this gives you the idea about the energy gain as well. So, one of the main objectives of cavity design is to choose the geometry such that you have to maximize the effective shunt impedance per length. So, and this is equivalent to maximizing the energy gain in a given length for a given power loss. Now, if you see the shunt impedance and quality factor in both of these power dissipation comes in the denominator. So, now we define a parameter r by q where we divide r with q. So, the power dissipation in the denominator in both the cases is cancelled out. So, again we get a quantity which is independent of the material of the cavity it again depends only on the geometry. So, this r by q measures the efficiency of acceleration per units stored energy at a given frequency and you can also use z t square by q either of these ratios are useful because they are functions of only the cavity geometry and independent of the surface properties which determine the power loss. So, let us say if you are making a if you have designed a cavity and you want to before fabricating the actual cavity you want to make it in a cheaper material a prototype in a cheaper material. So, you can measure you can make that cavity and you can measure. So, the quality factor the shunt impedance will not come out to be as it is for the actual cavity, but r by q depends only on the geometry. So, it will give you a good idea about your design. Then another factor that we consider in the design is the kilpatrick limit. Now at high fields room temperature cavities they suffer electric breakdown just like in DC in DC accelerators there was a breakdown. So, there the breakdown was at a very high voltage, but here also there is some breakdown. So, Kilpatrick analyzed the data on RF breakdown and he defined the conditions that result in breakdown free operations. The results were given by an empirical formula. This is a formula which is given by Boyd. So, it says that at any given frequency this is the value of the kilpatrick limit. So, if you plot this formula, so here this is at different frequencies this is the value of the kilpatrick field. So, in any cavity let us say we have a TM010 mode. So, you have an electric field here. Now let us say at any sharp corner here the local electric field could be quite high here the local surface electric field could be quite high here. So, for a given value of the accelerating field there could be a surface electric field at any location in the cavity which is higher than the breakdown limit. So, the design aim is to keep this value of the peak surface electric field less than the kilpatrick limit. So, kilpatrick said that if you for a given frequency you calculate this kilpatrick limit and you keep the value of the peak surface field below this limit then breakdown will not happen. So, this was given this formula has been given long back in the 50s now with improved vacuum improved surface conditions you can afford to be more brave. So, now the value of the surface field that is allowed is bravery factor some bravery factor multiplied by the kilpatrick limit. So, you could afford to go higher than the kilpatrick limit given by this formula. So, typically the values of B are in the range of 1 to 2. Okay now let us see for the TM010 mode let us just analyze it in little more detail. So, the electric field is given by this formula EZ and B theta is given by this formula the variation is shown here. So, the electric field is maximum where J0 is maximum. So, if you see J0 J0 is maximum at r is equal to 0. So, the electric field is maximum at r is equal to 0 it is maximum at the axis. The magnetic field is maximum where J1 is maximum. So, the value of J1 is maximum if you see the value of J1 is maximum somewhere here it is at 1.841 and this corresponds to a value of 0.5819 here. So, magnetic field is maximum wherever 2.405 r by rc is equal to 1.841. Okay so, magnetic field is maximum at the value of r equal to this at the cavity wall that means that r is equal to rc. So, we can put here r is equal to rc and calculate the value of the magnetic field we have B theta as E0 minus E0 by C J1 of 2.405 and value of J1 2.405 is 0.5191. So, you can calculate from here the maximum values of the electric field and magnetic field. So, electric field is maximum here magnetic field is maximum somewhere here not at the boundary and you can also calculate the value of the magnetic field at the boundary. The power dissipated in the Bilbox cavity is given by rs by 2 surface integral of h square. So, if you integrate over the entire surface. So, you have the you have the outer wall of the cavity as well as the end walls of the cavity. So, power on the outer wall is given by rs by 2 h square wall into the area. So, you can calculate it here power on each end wall can be again calculated and you can use these identities and calculate. So, the total power dissipated here is given by this expression. So, the stored energy in the cavity is given by half mu 0 integral of x square over the entire volume of the cavity. So, you can calculate this and this comes out to be here the power dissipated we just calculated comes out to be this and from this you can calculate the quality factor of the cavity. So, just summarizing whatever we have learned today, TEMNP and TMMNP modes are excited in a Bilbox cavity. So, both TE and TM modes can be excited. The variation of the fields in the theta and z direction have sinusoidal dependence in the r direction the fields have a Bessel function type of variation and we have also seen that TEMN0 mode does not exist in the Bilbox cavity because by boundary condition TEMN0 mode goes to 0 all all fields in this mode go to 0. So, this mode does not exist in the Bilbox cavity. In a good conductor the fields penetrate to the surface of the conductor equal to the skin depth. Due to surface resistance the power is dissipated in the cavity walls. So, whatever power you feed in the cavity part of it goes up goes in setting up the fields and is given to the beam as beam power and part of it is dissipated in the cavity as power dissipation. So, in TM0 and 0 mode in the Bilbox cavity we have only EZ field that is constant along the length of the cavity under B theta components. So, the field is time varying this EZ field can be used for acceleration. You can also put in drift tubes inside this cavity and this structure is called the drift tube linac as was proposed by Alvarez and this can be used for the acceleration of charge particles. The aim of the cavity design is to maximize the quality factor and the shunt impedance. So, this in this lecture we have tried to understand how using the electromagnetic waves the electric fields of the electromagnetic waves it is in a cavity it is possible to accelerate charge particles. So, you need not apply voltage directly to the drift tubes you can use the time varying fields of the electromagnetic waves in the cavity. In the next lecture we will see acceleration using traveling waves. So, you know that in a waveguide the waves are traveling waves and we will also study about periodic accelerating structures.


Well, it's finally hit the the heart of lettuce season and here I am harvesting freckle freckles lettuce which is a Leaf variety that we're growing for the first time this year and so far I'm really enjoying I like how it looks I like how it grows and this is growing on the back of our ground greenhouse This is the in-house greenhouse and this is some of the soil that we dug out to dig down to put the greenhouse in the ground and I could just harvest the whole heads, but I'm taking a little more time and I'm going along and just picking Leaves off of each one and This will extend the season a bit with these plus once they start to bolt. I'll let them bolt and then I'll get seeds for next year Now I'll probably have to choose either this type or the rouge de verre that is up on the other bed on the back of this Which one I want because I can't have both of them flowering at the same time and cross-pollinating Unless I want to experiment with crossbreeding, which I don't particularly it's not a lot of calories, but After eating all of our winter foods and our dry staples for months Having all this green is a real nice addition to the diet way back sign my property I have some beds that are totally overgrown with the nice thing about them is they have full sun And I'm a pretty shady yard in general. So this It's maybe a quarter of my really sunny areas. So this is where I can put corn and tomatoes and other things. So What I'm doing last year I built some beds up with some some nice soil, but Weeds got away from me and I just wasn't able to keep them down not to mention Plants and air are animals came in and got all my my starts. So this year I'm gonna have to fence it and Remult it That's ready to mulch it all you can see what happened. So this year. I'm trying to pull on smother with compost and wood chips and Straw and we'll see what this looks like as we go through the season Now that my corn has emerged in these mounds that I'm doing the test Remember, this is the bada crop where I'm planting just corn just beans and just squash And here I'm planting the corn beans and squash together so I can compare the yields with Otherwise similar growing conditions same amount of compost and space yada yada in this half This is my corn and now this is my beans and I planted three beans and two quarts of compost and over here I Am planting three beans into each of the each of the corn mounds and what I'm going to do Eventually is snip these corn plants. I'm gonna pick the three strongest out of five seeds planted and I'm planting three bean seeds and I'll pick the top two bean seeds So I'll fit them out and I'll have to do that here for the corn as well and the beans here So they get the same treatment other than they are planted together or apart And so here I am today planting up the beans next week. I will plant out the squash It's windy and it's hot But it's cool down from how hot it was so now I want to get some corn in and you've seen me plant corn in mounds over in the the back 40 and there I had 12 and 18 inch mounds with scoops and compost and their soil all around them and That's all been eroding because of rain and I'm pulling the top top soil in the mounds And so I'm not really enamored of that process even though it's a pretty traditional one So what I'm doing here is what I'd like to do which is plant through cardboard And so what I have is I've smothered this whole area, which you saw me start last week Covered it all in cardboard and then I put this mulch on top of it and this retains moisture. It retains soil fertility I'm not gonna lose any top soil. It actually builds soil and I'll have more soil next year some people like Charles Downing who I really admire on YouTube I I think is His videos are and gardening are really Inspiring and I like to watch them when I'm in need of a bit of energy, but I have good soil I have good fertility so instead of putting compost on top of poor soil I want to tap into that soil and so instead of putting compost on top and planting into that what I do Or what I am doing this year and what I've done in years past that seems to work Well is I clear the mulch off of a row And then I go down with the hammer Because I can't find my planting Implement and just pop a hole Making sure not to hit my fingers and I'm going every six inches This allows the roots of the corn to have Passage into there and then each one just gets a little handful of compost And this is really just to hold the corn kernel that I'm gonna put in I don't want to put the corn coil down the hole because it might not come up So I've got my handful of compost In each hole I grab my my corn. This is pop corn a friend of mine Chuck gave us pop corn and Instead of eating it. I'm planting it. Thanks Chuck So I just pop the corn in, tamp the compost down on top of it. It's about an inch down just with my finger An inch under the compost And then put the mulch back lightly on top so it can push through it and that's it And so I'll do one two three rows In these two beds here and that'll be plenty of pop corn as long as the deer don't get it or the raccoons or the buggers Now a couple of years ago I started building a hedgerow hedgerows are a little unusual in America, but essentially What it is is it is a hedge that serves as a fence and it gets its Horizontal members by cutting down trees and you can see For example right here Is a tree that I cut down you cut it down in a special way You only cut halfway through and so I cut halfway through and bend it over and that leaves the cadmium The outer layer the vascular layer of the of the tree intact And that way it's still alive. So here's the trunk that was growing up here and I bent it over now. It's got all of these guys growing off of it Right and so now what I'm going to do is bend these down And knock them Into weave them into the hedgerow they'll keep growing and it just becomes this really thick tangled mat of vegetation That shouldn't keep animals out. This was used to keep sheep and other things In in paddocks and fences in England and other places As a little like I said unusual here in America, but it's a nice low-tech sort of way to keep things Fence off so that's what I'm working on before we get dumped on we're about to have a storm So I gotta hurry So now this will grow up And I'll weave it all back in and over and over until I have a dense Hedge that Animals can't make it through Well, we've got 140 degrees on the exterior Of the compost pile and it's starting to rain. So I gotta hurry And get this back in the hutch We had 140 on the outside when I get to the inside here. I bet it'll be up to 160 You can see the steam coming off of it And it stinks because it's compost That's how it goes I'm trying to put the stuff that's not hot On the bottom and in the middle And just to cycle everything through so everything gets a chance to get real hot And composty Well, here I am out actually my strawberry area. So back here behind me.  So it crops up in my strawberry patch And looks like strawberries have to be really careful when I'm weeding. Oh, it drives me bonkers. Anyway, my plan here Is to make three rows That are going to be strawberries But right now they're going to be nothing and I'm going to put in Tomatoes because it's full sun.  I like these better than the cages Um, and I'll show you what I'm up to right now And then I'm going to hoe this into three rows cover that up plant my tomatoes and we'll be good to go So what I've done is I've driven in six posts And then I've run these bars Back and forth and now I'm putting these on top and what's going to happen Is I'm going to plant the tomatoes below this Tie this twine up here and the tomatoes will grow up the twine I find this to be easier to use than the tomato cages and we'll we'll see them grow on this through the season But uh, yeah, so here I am just lashing this all together So it can come be taken apart with a knife in the fall for the record. I really really dislike these Plastic smothering things But number one, I am out of cardboard Number two, I'm going to pull them up. I've been reusing these things. I never bought these these Just showed up.  It is just so pernicious I I'm not going to use chemicals on it number one At this point, where would I get them? And number two, I just can't bring myself to do it, but They're tempting. Oh, man. I I understand why people use them or did use them But it's I just can't do it. So this is what I'm left with and crossing my fingers. The worst part is It's an ornamental ground cover that somebody put in here Ah, good intentions, and I'm sure I'm doing stuff that the future owner of this house Maybe someday down the road would tear out. However, without fossil fuels available I think everyone's backyard is going to start looking more like mine I will say the nice part about growing tomatoes in this is that it keeps Uh, the soil microbes that often carry bacteria for tomatoes off of the tomato plants So when the water comes down as rain, it splashes on here It doesn't splash on bare earth and send microbes and bacteria And pathogens up onto the tomato. So hopefully they'll do really well here.  This thing was that high up to the top And now it's dropped already in half All right, I've been working this morning to grind up some corn I had leftover corn from my seed stock So this is dent corn. It's multicolored and I put it through This is the end of the first round stainless steel blades For birds The interesting thing about this cornmeal is it's whole corn. It's whole kernel meaning that the germ is in there and the oils and What would be taken out to make corn syrup and other things? Cornmeal that you get at the store has a lot of stuff removed just like white flour So when I grind up whole corn, it should make a different tasting product a fuller product I built this around because before if I ground fast it would just fly all over And so this piece of a plastic milk jug and I'm going to make a more permanent Edition here really keeps everything a lot more organized So essentially what these burrs do Is run the corn through these channels Where they get ground Between the channels when they catch at the end giving a nice Tight space for this to fit the the meal to fit through And if it doesn't fit through it, it gets caught and split kind of like hunt like a whole bunch of scissors that fit together And so these are sliding like that and catching the corn and slicing This is an old Schwinn world sport 10 speed It was picked up Lauren was going to fix it up and use it, but she's got a better bike anyway And so it was just kind of literally collecting dust Hang up I think I actually got rid of the wheels. So what I'm going to do with this Is turn it into basically a human power hub A universal human power hub where anybody Pedaling on this can run all kinds of different appliances The first one that I'm going to make it run is the grinder The plan is to mount it on something that will hold it at about this Orientation and then I'm going to get a hub for the back a replacement axle I'll put a new derailleur And chain on it so I can ship the gears And then that hub is going to come off on a belt pulley And a belt pulley is just a round disc with a v in it. You have them in car engines. You've got a well I've got one right here actually Happen to This is an old bench grinder But it's got a pulley with a belt on it and basically I'm going to replace this motor With this bike and then I can run all kinds of tools That I'm going to build Like I said the first one's going to be that grinder And so what I'm going to do is make it so you can grind Corn, wheat, oats, whatever With pedal power instead of arm power It took me about Probably 15 minutes to grind a cup of corn three times So with this I'm hoping I can cup not only cut down that time But make it more pleasant time also because this is not a natural motion whereas bicycling is extremely natural so Now I just need to find the parts take some measurements build the stand And get that together. So I think I'm going to have to take a trip into the nearest town To the bike shop you can get some scrap parts Some of my potatoes look really good and they've been weeded consistently And I can put down some leaf mulch to keep this weeds down But over here I've had a little more trouble As you can see The grass has been growing up and that's because there was a fence here and some infrastructure That's hard to weed around and so today I'm coming with my scythe And I just kind of want to demonstrate How effective a scythe is in reducing All of these weeds around plants that you don't want to cut down. So here we have potatoes Weeds and more potatoes and so What I can do Is walk And simply just catch All the weeds On this side Of the potatoes and with the tip I can kind of guide The scythe To push the potatoes out of the way catch the weeds and cut and then I go back On the other side And now this becomes mulch And will die And smother Some of what's left Now a friend of mine botan anderson who runs one scythe revolution who taught me how to scythe And also I bought this scythe off of him He had the really neat idea of spacing his potatoes out exactly the length Of one large movement of a scythe about six feet and that way he could just walk And scythe a field between his potatoes And drop the hay on top of the potatoes As mulch with one motion and it's really clever I'm not doing it here because I don't have the space, but it's a it's not a bad idea Well, there we are 160 Well, it's been a busy couple of weeks and not just for food growing Sometimes I need to take on freelance work In order to get down what I need to do and that's what happened this last week And that's why there wasn't an episode last week So what you're seeing in this episode was a lot of what happened last week And some of what happened this week and next week I'll catch up fully But yeah, I'm sorry that I didn't get the episode out on time. That's uh It's one of the things I really try and do but Work sometimes just gets in the way. So thanks for watching Foodmageddon Next week we'll be back with a lot more plants a lot more growing and a lot more weeds Because it's that time of year if I can't get on top of them now. I'm gonna be sunk But we're having a good time with the with the warm weather and being home, but Yeah, it's definitely going to be a change Coming in June as we won't be able to go to the grocery store as often And there's gonna be a lot less available as fossil fuels become more scarce So do resources so stay tuned for that Like and subscribe and all that jazz. Please share with your friends Check out our blog at lowtechinstitute.org and you can reach me at scott at lowtechinstitute.org Thanks for watching. Stay safe


Curely also asked, what should be done when things go wrong with smart contracts, i.e. where funds are lost due to coding errors and bugs? This is a really great question. In fact, it is the basis of a giant debate happening, primarily in Ethereum right now, which started with a DAO bug, the decentralized autonomous organization that had a massive bug leading to the loss of $155 million. In the end, the Ethereum community decided to revert that transaction, but in the process of doing that, split the Ethereum community into two, and now there is also Ethereum Classic, which is the part of Ethereum that refused to reverse that transaction. This is likely to keep happening. There is an ongoing debate as to what to do when funds are lost due to coding errors and bugs. On the one hand, people might think that this is a way to protect users, but unfortunately, who gets to make these decisions? When you vest power in someone to make these decisions as to when funds can be reversed, not only does that power become dangerous, but the people who have that power are now liable. What happens when a government asks them to reverse the transaction? They can't say, we can't do it, because they've already done it. These are very dangerous and difficult decisions. The opposing argument is that reversing things that were lost due to coding errors and bugs creates moral hazard. Moral hazard is a particular economic condition where people take more risks than they would otherwise take, because they know that they will get bailed out. We find moral hazard in areas such as insurance, banking, and stock trading. When people know that somebody else will assume the risk, or they think that somebody else will assume the risk, they take on more risk. As a result, that leads to more coding errors and bugs. If you knew that if a smart contract has a bug and you lose money, you would never get it back. Would you be more careful with auditing, selecting, and carefully putting small amounts before you put medium amounts, before you put huge amounts of money on top of a smart contract? Conversely, if you knew that if something went wrong, you'd simply get bailed out, would you be more reckless with the use of smart contracts? This is one of the things that is at the heart of this debate, and it's not resolved. There will be different blockchains that choose different policies as to how to solve this. Simon asks, regarding Ethereum, what if there is a bug in the initial program running on all of these different machines? Is there a way to correct the code in the contract, or is it forever flawed? Simon, you've picked up on something that is a fundamental design consideration when designing smart contracts. Smart contracts are recorded on a blockchain, and they represent a fundamentally different development process. Once you create a smart contract and encode it on a blockchain, its code cannot change. It is immutable. It will forever run that way. This creates quite a problem, because if you have a bug, that means it will be there forever. You cannot modify that contract after it is being created. There are a few ways to get around that. One way to get around that is to essentially create a process... where you can migrate from one contract to another, to another, to another, so that you essentially move all of the data, all of the tokens, all of the owners, all of the information stored within the contract, to a new version of that contract that you deploy on the blockchain, and then you kill the old one. However, this isn't so easy to do either, because if you can migrate all of the data, all of the ownership information, and all of that to a new contract, that means ultimately that the developers who deploy this contract... have to retain control over it, which means it's not very autonomous, and it's not very decentralized. Because you have centralized control, and the developers have to retain that control in order to be able to upgrade it, you have some potential issues there. That also means, of course, that there is a whole other class of bugs that can exist in the upgrade code. Specifically, if you look, for example, at the DAO, which is one of the most famous vulnerabilities in the Ethereum space, the DAO had a bug in the code that was meant to split the DAO, so that people could fork off, potentially upgrade and change the code. So, there's a potential that the code that checks who the owner is, and allows you to upgrade and migrate to a new contract, itself can have bugs, and that's a whole other category of bugs. So, this is one of the problems, not problems, it's one of the differences between developing software in a traditional centralized code-test release and version upgrade mechanism, a classic software development methodology. And the methodology you have to use with smart contracts on a blockchain, where you don't have an opportunity, always, to fix mistakes from the past, or where creating the opportunity to fix mistakes is in itself quite complicated. Camilo says, what is your opinion on smart contract developers as the new gatekeeper-middleman intermediaries? So, I'm going to just paraphrase that a tiny bit. So, the idea here is that in a system like Ethereum that supports smart contracts, but this would equally apply to Rootstock or Cardano, or any of the other smart contract platforms that have a virtual machine. While the consensus rules establish that a smart contract will be executed exactly as written, and you can protect those consensus rules through decentralization, that still allows smart contract developers to write smart contracts that are not decentralized. In fact, one of the questions we'll talk about in a bit addresses that specific issue and how it can be a vulnerability. So, the question was, doesn't that just make smart contract developers the new gatekeepers? Because they can write smart contracts that are not decentralized, they can write smart contracts that give them powers. They can write smart contracts that have a certain set of rules, and those rules are not subject to consensus, only the fact that they will be executed correctly. I think part of the issue here is the idea that just because a system has a set of rules, that doesn't mean that you can't write something, contracts, transactions, whatever, to re-concentrate power in a centralized way. The internet is a decentralized communications protocol, but it does allow the emergence of centralized companies on top of it, which is essentially a function of economics, not a function of the underlying protocol. So, you have a completely open peer-to-peer protocol, and on top of that, people build things like Facebook. Similarly, Bitcoin is a decentralized currency, but that doesn't stop someone from creating a centralized exchange, a custodial exchange, and saying, I'll hold all of your keys, don't worry. Or creating a centralized payment processor that says, I'll receive all the transactions, hold all of the Bitcoin, and give you fiat in return, or have a custodial wallet for users, or all of the other things that we've seen, all of these centralized forces, or more recently, build a centralized exchange-traded fund, which is a custodial Bitcoin fund on behalf of other people. Just because the underlying cryptocurrency is decentralized doesn't mean that people can't build centralized things on top of it. The trick is that people can build centralized and decentralized things, and then hopefully the market gets to choose which ones to use so that they get the things that they want. If what they want is convenience and wealth, they'll choose the centralized things that are going to be more efficient at delivering, at least for the short term, the convenience they want at the expense of privacy. If they understand the principles of decentralization, maybe they'll choose the decentralized application.  You can go on Bitcoin and use a custodial exchange to store all of your money. That's not a very good choice, but you can. The same applies to Ethereum smart contracts. Just because someone writes a smart contract doesn't make you use it. Just because someone has set the rules for their Ethereum-based social media network, or their Ethereum-based decentralized exchange, which isn't quite decentralized, or their Ethereum-based smart contract for loans, doesn't mean you have to use that one. If you use that one, you are making a market choice that says, I want to use the rules that they have created. On the very same Ethereum network, you can choose to use a smart contract that doesn't have backdoor ownership and controls for a centralized entity. You can choose to use a smart contract for social media, for loans, for decentralized exchanges. That is truly decentralized. The choice is yours. Are they gatekeepers? Gatekeepers have to have an advantage over other participants in the economy. Gatekeepers generally have a government license, a regulated monopoly, the ability to control the rules by which people play the game. In decentralized currencies, decentralized smart contracts, decentralized protocols, gatekeepers don't have special powers. They don't have the ability to force a monopoly, to get special access, to get special privileges, to get preferential treatment, to get rent-seeking behavior.  They don't have an advantage over anybody else running a smart contract. The developers of smart contracts are not the new gatekeepers in Middleman, because they don't have any special powers. They have to compete. Their smart contracts have to compete for your choices against all the other smart contracts. People make poor choices, but it is their choice to make. The developers don't have any preferential access to Ethereum. I don't think they are the new middlemen for Ethereum. On a decentralized platform, you can write both centralized and decentralized applications. It is up to the market to choose which ones they want to use. Anita has another question. This is about the Bancor hack and security issues with ERC-20 tokens in general. This is an Ethereum question. Can you please explain what happened during the Bancor hack some days ago? What are ERC tokens and how secure are they? Given the Bancor was not the first smart token issue that was hacked, are there many smart contract hacks to come? Is Ethereum simply put less secure than Bitcoin? To start that explanation, on July 9th, one of the big exchanges that is a decentralized exchange, or claims to be a decentralized exchange in the Ethereum space, called Bancor got hacked and lost somewhere around $23.5 million in a combination of stolen Ether, and the Bancor network token, or BNT, I believe it is called, which was their own token. The way the hack happened was that Bancor was running smart contracts that allowed users to operate a decentralized exchange where they controlled their own money, and were able to exchange it with other people through smart contracts, without an intermediary. However, these smart contracts had a privileged account that allowed Bancor to change things, to restrict transactions, or stop the flow of money, or take money from wallets, from what I understand. I may have this wrong, so bear with me. From what I understand, they had effectively a super user within their smart contract, that allowed them to intervene in the case of a problem. We have seen this kind of formulation before. As I mentioned in an answer to a previous question, smart contracts on a decentralized platform can be written in a centralized manner, or a decentralized manner, and you choose which one to do. The DAO, the DAO, was partially decentralized, but still had some curators. However, those curators didn't have enough power to stop the hack. When it did get hacked, there was no one who could undo that hack, and that is a double-edged sword. If you make it completely decentralized, but there is a problem, then no one can fix that problem. But if you make it a bit centralized, so that someone can fix the problem, sometimes that is the problem. In the case of Bancor, what they did was, I believe, they added a centralized wallet that could control some of the functions of the decentralized exchange, so that they could intervene in the case of a problem. However, when that centralized wallet got compromised, it was able to drain money from the decentralized exchange, something that wouldn't happen if it was truly decentralized or fully decentralized exchange. Bancor said that centralization and decentralization are a spectrum, and you can be decentralized even if you have some centralized functions, and that is absolutely true. However, in this case, the centralized functions were the weak part of the system, as they usually are. If you have a system which has some centralized functions, those are going to be the primary target of attackers. Obviously, they can exert greater control over the decentralized system. In the second part of the question, I need to ask, what are ERC tokens and how secure are they? Given that Bancor was not the first smart token issuer that was hacked, that is a great question. You may have heard this term called ERC, and specifically ERC-20. ERC doesn't mean tokens. ERC is an Ethereum request for comment, and it is a precursor to an EIP, which is an Ethereum Improvement Proposal. Very much like in Bitcoin, where you have Bitcoin Improvement Proposals, or BIPs, Ethereum has EIPs. EIPs and their precursor, which are ERCs, are basically just discussions on standards. Eventually, one of these discussions becomes a standard that is either de facto adopted by the community, or through enough votes becomes an official standard, if you like, of Ethereum. ERC-20 was one proposed standard for how to do a transferable token that can be named and have a specific amount of tokens as its initial supply, and can be issued by an issuer and have a token symbol and all of these things, and can be transferred from owner to owner. A lot of tokens were created with various smart contracts from the very beginning of Ethereum. However, each of the tokens used a slightly different way of doing things because they used its own smart contract. ERC-20 was the first attempt to standardize the interface to the token smart contract, so that if you were an exchange or wallet, you could support any token that followed the ERC interface standard. To do a transfer of a token, you would use the same function with the same parameters. If you wanted to check what the supply or how many decimal digits or what the token name or what the token symbol is, you would use the same functions. For a token to be ERC-20 compatible, it means that it supports the five or six functions and variables of the ERC-20 standard. It is very small, you can read it quite easily, and you can find it online. Once it supports those, that means that any wallet or exchange can interact with that token in a very standard way and use that token. Now, really important point, if something is an ERC-20 token, that is a minimalist description of its function, meaning that as an ERC-20 token, it has at least the five or so variables and functions of the ERC-20 specification and does support those. But it can have other functions in addition to that. A basic ERC token has only that, and that smart contract is actually secure. It has been very well tested. So far, we haven't seen too many significant problems. There are a few conditions under which you can accidentally transfer ERC tokens to a contract that doesn't expect to receive them and have them locked forever in that contract. There is a little problem with some of the ways you do transfers if you are not careful, but the ERC token standard itself at the minimalist level has not been hacked. If you take the ERC-20 token and then add a function that says, and here is the special super owner, and then you add another function that says, and the super owner can do a transfer even if they are not the authorized user of the token, then you have something that is still ERC-20 compatible, but has an element of centralization in it, and that may have a bug in the extra functions you added. Just because something is ERC-20 compatible doesn't mean it is secure. The minimalist specification is, but if you go adding things for every line you add, the number of bugs increases exponentially. How many more smart contracts hacks will happen? Ethereum is a system that evolves its maturity by putting code out there, creating a bounty effectively behind these smart contracts, and then having people find bugs and exploit it. It is a system that is designed to have a lot more iterations in its functionality than Bitcoin, move a lot faster, even if that means breaking some things in the process, and is much more experimental. As a result, it has a lot more security vulnerabilities than Bitcoin. Practically speaking, Ethereum is less secure than Bitcoin. That doesn't mean it is not secure. It just means that you need to be very careful about which contracts you use and which you don't. There are some smart contracts that, at this point, have significant maturity. But what does significant maturity mean in a currency that is three and a half years old? We have to have that in perspective. That would be equivalent to Bitcoin in 2012, and Bitcoin still had some rather significant bugs and weaknesses in 2012. Can Ethereum mature to be very secure, at least in terms of a subset of well-matured, well-used smart contracts that are very useful? I believe it can. Will it take longer than Bitcoin? Yeah, probably. On the whole, there are more things to be worried about in terms of security vulnerabilities in Ethereum, because it has a lot of flexibility. A lot of flexibility is a double-edged sword. It means that you can do very interesting and innovative things with smart contracts, but it also means there is a lot more opportunity for vulnerabilities, mistakes, and security flaws. That is an engineering trade-off. You decide, do I want more flexibility if it means less security and robustness in the short term, or do I want less flexibility and have much more security and robustness? Bitcoin answered that engineering trade-off one way. Ethereum is answering that engineering trade-off another way. We are going to see how it plays out.


Welcome to the wonderful world of vectors. In this video, I'm going to show you some vector basics. I'm going to teach you how you can take a written description of a vector and make a drawing of it and then the opposite. I'll show you how you can take a drawing of a vector and write out the name for that vector. That's called vector notation. The examples I'm going to look at today come out of the handout, Intro to Vectors, which you can find on our Moodle site. Let's get started. Here's a quick example. Let's say you wanted to draw a vector representing displacements of 40 meters left and 80 meters left. Your first vector is just an arrow pointing left that you label with 40 meters. But one thing we want to do with any vector diagram is to draw the vectors to the proper relative magnitude. This means that even though we don't actually draw a vector that is literally 40 meters and another one that's 80 meters long on our paper, we are going to make the diagram of the 80 meter long vector about twice as long as the 40 meter vector. This keeps a nice relative magnitude. Next we will look at vectors that are at an angle. We have two systems for writing out the notations of vectors at angles, the navigational system and the square bracket system. The navigational system works on a weird principle of the English language. Let's check out this awesome photo of teacher band as an example. Now let's say you knew that the drummer in teacher band is Mr. Stridehorst, but you don't actually know what he looks like. So I could tell you that Mr. Stridehorst is right of Mr. Langdale. Now let's think about how we said that. Stridehorst is right of Langdale. So to work out who Stridehorst is, you needed to start off at the end of the sentence and find Langdale first. Then you move to the right to find Stridehorst. This is exactly how the navigational system works. If you needed to draw a 3.0 at 30 degrees north of east vector, you could start off with a little Cartesian plane or an XY axis with the cardinal directions labeled and then you could find 30 degrees north of east by starting at the end of the sentence at east and then drawing out a 30 degree angle starting from east and going to the north in order to get the angle for your vector. This vector is now drawn out at 30 degrees north of east. Here's another example. Let's draw 60 degrees south of west and we won't even worry about the magnitude of the vector for this one. We'll just focus on the direction. We're going to start off on the west axis and then we're going to move south by 60 degrees and draw in our vector and label our angle. This is what 60 degrees south of west looks like. Now let's do the same skill but in reverse. Here's a diagram of a vector. Let's figure out his notation. I can see the angle is drawn in between the east and south axis. To be more specific, the angle is measured from the east moving towards the south. So we say that this is 50 degrees south of east. Note that our vector, 50 degrees south of east is not the same as the vector 50 degrees east of south. These are two totally different angles. However, 50 degrees south of east is equivalent to another angle measurement. We could have measured off the south axis by 40 degrees and gotten the exact same angle. In other words, we could also say that the notation of this vector is 40 degrees east of south. If you're a little confused by this, that is very normal. Every vector has an equivalent vector notation that's called the complementary. And you don't usually need to write out both notations. It's just good to be aware that there's two different ways of doing it when you're getting started. Let's look at a second example. Here we have a 60 degree angle between north and west. The 60 degrees is being measured from north and moves out to the west. So we say that this vector is 60 degrees west of north. Now I don't want to overwhelm you, but I should also mention that the complementary angle to this is 30 degrees north of west. Notice how complementary angles are pretty similar to each other. They always add up to 90 degrees and their notations, the letters are just reverses of one another. The second method of vector addition I'm just going to call the square bracket system. In this system, all angles are measured going counterclockwise from the positive x-axis. And we write the angles with square brackets around them like this. Let's draw out a vector using this notation. 3.0 centimeters, 55 degrees. Again, we're going to start by drawing out a Cartesian plane, but this time we won't put the directions of north, south, east and west on it. Instead, we'll label it at zero degrees here at the positive x-axis. Then 90 degrees, 180 degrees and 270 degrees going counterclockwise. Starting from zero degrees we'll rotate counterclockwise until we've reached approximately 55 degrees and draw our vector. It's actually pretty quick and easy to do angles between zero and 90 degrees with the square bracket system. Here's another example of the square bracket system. We'll draw 120 degrees. We'll begin with the same setup as before labeling the angles in the Cartesian plane. We'll start again at the positive x-axis and then move counterclockwise by 120 degrees. Notice this method works really nicely for angles that are greater than 90 degrees. Now that you have the basics, you can trial this video on adding vectors and breaking them into components.


Well, Daniel A. Gago, a chieftain of the Labour Party in the United States, has accused Nigerian politicians of causing other countries their aggression through with their self-centred and money-oriented governance style. I order Nigerians to replace politicians with their responsible ones and call for a drastic change in the country's governance. Nigerian politicians are the principality plague in this country. And we must fight them. We must fight them to reclaim our country that works for all of us and put people who are compassionate and caring about the people they govern or want to lead. How do you lead people when your first priority is to spend 165 million for yourself? We are with George President Bollard. I'm going to consider increasing workers minimum. We are also implementing measures to improve the standard of leaving for Nigerians while also suggesting economic and labour reform to change the current economic narrative. Why shouting off the rooftop, trying to propose, raise questions about economic reform, education reform, public health reform, welfare reform, labour union reform, labour reform, hourly rate for monthly rate, that hourly rate should be at least between 500 to 1,000 a year. And all our pushing or that, it just keeps falling on deaf ears. People don't understand that we need an hourly rate. Hence the minimum wage should be at least with 500 a year. Hourly rates. The minimum hourly rate should be at least 500 a year. And our minimums. I'm the only country speaking about pushing for that. I think the moment we put that minimum hourly rate to beginning to, the cost of leaving will force them and the standard of leaving will increase. People will be able to treat themselves when they fall sick, not die from malaria.