This is perfect, boys. Perfect topic for me to talk about. I'm getting accused of steroids myself. I had gynecomastia surgery. And I have an in-depth knowledge of celebrity politics so I can make some great jokes. Does anyone else truly believe that Adesanya is rolling Costa in some elite billionaire's mansion right now probably pinned up against some marble statue that looks awfully like myself? And that's not really a joke. With how crazy these psychos in control are, I think it's more of a reality. They probably threw both of them on a private jet straight off to Epstein Island promptly after that fight.  Israel Adesanya and Palocasta are two fighters in the UFC Ultimate Fighting Championship. It was a very popular fight last Saturday and there was quite a bit of back-and-forth banter before that fight. Costa joked that Adesanya was a white belt at a press conference.  On top of that, after he knocked out Costa, Israel humped him like a dog.  So that's what I've been thinking about. Everyone else seems to be focused on Adesanya's tit. And I think it's much funnier that it's one tit as opposed to two for some reason. Now this is a side effect of steroid usage. What happens when you take testosterone or certain drugs that alter your testosterone is your body produces extra estrogen to match it, or at least I think, I'm not 100% sure. So unless you block that estrogen, you end up with female breast tissue. As growth of breast tissue is something that estrogen stimulates.  Considering Adesanya did not have this in his last fight, it's painfully obvious that he's been using steroids in between over the past few months. What's crazy to me is that professional athletes are still keeping steroids a secret and they've been doing so for dozens and dozens probably over a hundred years. They say that steroids weren't invented into like the early 1900s but I believe that's a lie and that all famous professional athletes throughout history were using steroids. Especially with sports where the athletes don't look like roided out bodybuilders, juicehead monkeys. You know, people want to believe they're natural but this isn't WWE. It's not fake. These fighters are beating each other half to death. And the UFC has had its fair share of fighters that are overly muscular. Costa himself is on that cell tech. He looks more muscular than a lot of natural bodybuilders. Hector Lombard is an obvious one. Aleister Overeem all past UFC fighters. USADA is the organization that tests these athletes for drugs. I don't know the specifics but usually there's a maximum number of times they can drug test you. So after that final drug test, you can blast whatever drugs you want. I think I remember hearing that MLB statistics were higher towards the end of the year after those mandatory drug tests. But that's just the drugs they can take that trigger the tests. You know, I'm assuming they can take plenty of stuff consistently under the radar. Genetics, hard work, diet, dedication, combined with that drug usage is what it takes to be successful. And a major advantage we've seen, John Jones being a good example, arguably the best UFC light heavyweight fighter of all time, is the fighter's ability to use high doses of very potent steroids. Certain drugs make you so much stronger and faster that if you can use them even for a few weeks before a fight and your opponent isn't, it's near impossible for them to win.   He literally threw his career out the window, at least in my opinion. Unless this was all some staged nonsense to get everyone to realize the truth of what these athletes are doing. If I was him, I would have just no showed that fight.  How embarrassing it would be to go into that UFC fight with a tit bigger than his girlfriend or boyfriend for that matter. Now, I had gynecomastia surgery last year and I didn't really need it because I didn't have much tissue behind there. It was just large areolas, probably because I was fed soy formula as a child, more estrogen. You guys can go look at my shirtless videos before and after the surgery even in the progress video I did. There isn't really that much of a difference. No noticeable breast tissue before or after the procedure. My chest just doesn't look that great genetically how I developed. I don't think I would have gotten the procedure done if I knew that stuff but I wouldn't have known if I didn't. The reason I'm bringing this up is because the recovery time from that surgery is usually only two, three, four weeks. I'm assuming Adesanya could have probably had some expert surgeon go through his armpit, remove the tissue and he could heal up reasonably in a week or two at least enough to fight. Then again, I don't know, maybe it literally happened in the past week or two before the fight. It could happen very rapidly. This is the main thing that discourages me from pursuing professional sports or bodybuilding. I would love to live in a world where it was an even natural playing field although it's safe to say that steroids actually make things more equal because if not for drugs the best genetics would win. By genetics we basically mean who developed better got more nutrition through their younger years. You're not going to become the best UFC fighter in the world by just taking steroids but the best fighters, the best athletes are certainly using them. It's simple. You follow the basic elements of any sport, training, diet, drug usage. You will succeed depending on how much you dedicate to that will determine how far you get. Also you have to be mindful of your height, body frame. Not everyone is going to play basketball or be a swimmer. Thank you guys for joining me today. Maybe if there are any adult video companies they can produce a replica like they can get some dude that looks like Adesanya and some like Brazilian dude that looks like Costa. That would be funny. That would be funny. It's not a bad idea to be honest. Probably make a lot of money. I guess they can give me a cut of a cut of the profits if they get the idea from me. So just drop a like on the video guys. Leave me a comment down below. Let me know what you guys would like to see over the next few days week or two and I'll see you guys for tomorrow's video.


With this third lecture, we continue our study of polymer solutions. So now, Flory said okay, there are two very interesting things there. One is, keep the polymer in a good solvent. If the polymers, monomer of the polymers don't like each other, then we have a effect, repulsion between them. However, it cannot go on swelling because when you increase, remember the distribution is e to the power minus r square, where the r square comes because all the many configurations. What is the configurational degree of freedom tells you? It tells you the entropy. Now, you can see e to the power minus r square has a maximum, you have r equal to 0. But this remember this is an average because many different though orientations, that's why r0 comes. However, it also tells you cannot stretch it too far. This is called elasticity of the polymer. So polymer loses lots of entropy if you stretch it. So there is these two forces acting opposite to each other. One is that repulsion energy which tries to push it out but elasticity of the polymer which wants to keep it at certain size. This is what we realized and it is a beautiful calculation. Okay, say internal concentration of the N by RT as we discussed already. Then I can consider repulsion energy with this equation that every repulsive is half k by 18 nu Pc square. So this nu T is the effective parameter and as I said this is essentially nothing but Van der Waal's theory that we are doing. And so see now here the important thing to know two terms nu T and let us know VT, not nu it is VT, which is a temperature dependent excluded volume parameter which is like very much like a parameter in Van der Waal's theory. That means it is a volume parameter but it essentially takes care of the interaction energy. Now and so see is the concentration in the number within a volume. So volume is R to the power D number is there. So this is repulsion energy. And Florie introduced this parameter 1 minus 2 XB to the power D and we will learn a lot about it later. But it is just to show that it can go either from plus to minus. And then integration of the volume element if I integrate with this volume element of this C to N to the power RT and then I get this quantity volume element then I will get the total repulsion energy is N square because there is coming with N here RT and then I take all the all the all the monomers then I get N square. So integration of volume element essentially meaning taking all this. So the important thing is that repulsion energy scales as N square by RT. Now if I take the elastic term which again is coming. Now it is nothing but what is in the exponent of Gaussian distribution. So R square by N square that's what I had in the Gaussian distribution. So since e to the power volumetric distribution gives me a value of a quantity X e to the power minus X by KBT. So I just rearrange terms I get the elastic terms trivially KBT R square by NB square. So I have the repulsive term of N number of monomers connected in a polymer in a chain is N square by RT KBT V and V is essentially Vendol's A and then it plays a very similar level of A and comes out in a very similar way that we have already done Mayer's theory. When you do that then we see we add the two free energy repulsion and repulsion and the elastic term which is an effective attraction which is kind of putting it closer together. When I add them I get these things sorry it's a little bit but we will give you the idea. I have screwed up equation by V by N square by RT that is where just two terms are added. Now the important thing is that I minimize it with respect to R and if I minimize R with respect to R then I get a beautiful result. This is because in a DVF DR equal to 0 then there is a R to the power T plus 1 it becomes and these terms come R. So D plus 1 and R but they are in opposite side one is numerator and denominator. So when I rearrange the terms then I get there is a negative comes from R square by RT and positive comes R square by RT. So they have worked out right. So you get then RT D plus 2 scales as the N cube and then you get the beautiful result. RF is for flow rate that N to the power nu the radius of flow rate in the nu is called flow rate parameter 3 by D plus 2. That means so when I get D equal to 3 it becomes 3 by 5. Very important result D equal to 3 I get 3 by 5. So suddenly you see in ideal polymer chain these N to N distance scales as N to the power half square root in half nu is half. However in when you take attraction and impulses all these things into account and in a good polymer solder then you get this huge difference. That means N to the power half because N to the power 3 by 5. But when you go to D equal to 4 another surprising interesting result D equal to 4 it is 3 by 6 go to half. So in 4th dimension that is very important or theoretically not much relevant in the real world but you get ideal chain behavior partly because when you have 4th dimension then the concentration of polymer there is so much more volume around each polymer than this repulsive interactions and all these things are not that important. That's why you get back the ideal polymer chain but 3 dimension and 2 dimension things are very different. Now it is we have discussed this before but I would like to emphasize it RF is N to the power nu for ideal chain nu is half but it is not so in A. So in the real chain it is very very different. Tharman N is a polymer solution we already did quite a bit because at the end of the day it is the same thing that we will be having this take care of these 2 forces one is the interaction with the solvent monomer solvent interaction that's one term which is I already said 40 parameter chi that will come here and will be a little bit more quantified here and then we will do the mixing of polymer in a solvent. So solvent has to come in. So in addition to the entropy that we talked about and polymer interaction that at all you will have one more entropy that entropy is a mixing entropy with the solvent than the polymer. So basically the entropy term here is essentially the arrangement of polymer chains that exist. So what one considers in Tharman N is a very famous theory that one considers that the gel lattice and the lattice in polymer because polymer is so big much bigger than solvent that one can consider as I told you as a random work. And that since the size of the monomer is not important one can as well take the advantage of the lattice. So now we have to calculate that how many ways or make a estimate how many ways I can put monomer the polymers, monomers of the polymer and the solvent molecules on a lattice and that will give an entropic term. And there is an enthalpy term because interactions between solvent molecules and solvent and polymer and polymer monomer monomer. So enthalpy we have three terms and we now we already considered that effective interaction of these kind of good solvent but the good solvent here is the same thing and what we are doing is very similar. But we are doing a little bit more justification of the polymer or polymer solvent interaction that is a little bit done better than quantify that. That is why otherwise nothing different from the what we did earlier or say minimization of free energy and everything will come. So when you do that we said how many ways I can put the polymer then you can see the first term and the second term on the right hand side. This is the free energy of mixing and free energy of mixing as the entropy term. That means how many ways I can place a polymer N of size N, polymer size N let's say Np, N is the total number of sites and then and calculate that is entropy of mixing because I am mixing solvent molecules and the polymer and I am laying down the polymer in the lattice. And how many ways I can do that essentially same as binary mixture entropy of mixing. When you do entropy of mixing in your thermodynamics in binary mixture what do you do?   It is a very similar thing here in polymer here however one has to take care of the fact that you have a polymer is a monomer. So the first term and by polymer constitute of many monomers the first term takes care of that fact. Second part is just the solvent part and phi is the volume fraction the size of the through phi enters the size of the of the polymer. Now the important thing the chi I said is the floating parameter chi that has exactly the same thing we have in binary mixtures and we did the binary mixtures or you are not even looking my book by many mixtures as you done in great detail.   So a good solvent chi is negative and the bad solvent chi is positive. So through this parameter we essentially what flow we did use the ideas of entropy of mixing and the entropy of mixing and the binary mixture theory the ideality non-ideality parameter that we know in the breakdown of Raoult's law. So the idea of this classical physical chemistry is combined with statistical mechanics or statistical concepts to develop this statistical thermodynamic theory of polymer solution in a very elegant and very simple way which has took the test of time. So this again the same thing this is side because I divide the total number of sides and then you get the entropy of the solvent as I said an entropy of the things I am not going to derivations you will find the derivations in many places including my book and also in give video. So now I want to calculate the entropy is the entropy of laying down the polymer into a lattice side polymer of volume fraction phi lattice of insides that's why the first n in the denominator comes. Now monomer-monomer interaction as we just discussed is the Van der Waalsen this KBT I put KB equal to 1 KBT by the pro-reparabiter chi for monomer-monomer phi square the monomer solvent because monomer and solvent it is phi into 1 minus phi because 1 minus phi is the solvent and solvent solvents 1 minus phi square. There are three terms what I do now I next add all these terms together and I keep okay I keep in the term which is linear so I find out in that sense there is the maximum contribution comes from the one that I need is the monomer solvent interaction is phi into 1 minus phi. So this becomes the important term the first term becomes important term for me in this understanding the thermodynamics of polymer because solvent solvent polymer interaction is chi phi into 1 minus phi. Chi gives the relative interaction and phi into 1 minus phi gives the probability that a monomer is interacting with the solvent molecule. Then I add this all these things together and then I again minimize and when I minimize the free energy then I get the theory theory of the polymer solution and that theory when I do with the value of chi it is essentially Van der Waals theory that then explains these good solvent and bad solvent collapse in terms of these things. So the chi in the good solvent chi is negative but when it crosses over to poor solvent then chi is positive. And this is exactly the thing that you get the free energy and then you find out what is the side and you find there is a crossover in the size from depending on the value of chi. Okay this is the essentially this free energy embodies the thermodynamics of polymer solution and proteagin theory. More details are worked out in my book. I am sorry we don't have but we will try to put a slide there on these things. The next slide is missing. This is the theory that you know we know experimentally when we are doing a transition we are doing a we find a transition. That means when I add many important things with the gel many of the applications of material. What do we do? We go on adding the concentration in these monomers and then we sometime add something to gel them together. But what happened when the monomer concentration goes beyond certain thing concentration or temperature is lowered. Then we find there is a dramatic transition a phase transition that takes place from salt to gel. And that is called the soldier transition is a very well known phenomena which is essentially very close to what we do in is very close to what we do in in mayas theory. So soldier transition in very similar to gas liquid transition and the reason of my including in this course and also in the book is that to show you how mayas theory is used. Mayas theory of 1937 and Florin did almost at the same time and Stockman did later in 1941 the same theory Stockman was a student of Joseph Mayer. So basic idea that instead of mayas clusters we have the real polymer clusters. And you remember the mayas theory two guys come close to each other and we have a maya function here we have the maya function is placed by something called functionality f and the polymers like nylon they never form they are trade like they never form a gel but they become very long and it is important that they don't form a gel for all our textiles. But in many other case like rubber we want them to form a gel that is when functionality has to be catered. So I briefly tell you now this method of soldier transition and there is a basic idea then is that I have a solution phase where viscosity is low and maneuvers are kind of dispersed and then this underway polymerization and they form a giant molecule and they precipitated out the reason it is important to understand it because the soldier transition if we can control we can control the property of the gel. And so this exactly it follows like mayas theory system in identical monomers and carrying identical functional groups. So monomers react with each other to form a polymer and the functionality is f chosen very similar to mayas f function also function with f. Now we have to say at the after that some stage of the polymerization we have mn gives the number of monomers of size n and then some of mn the last equation in the bottom is the total number of polymers. And nmn is the total number of monomers is exactly what we did in mayas theory the nmn is the number of n clusters of maya nmn is the total number of molecules or atoms the system name and the nmn is there also the capital m was the size of the polymer. Okay so the total number of ways now we do exactly what maya did so we can remember what we did the mayas partition function when here that is the number of ways I can form monomers timer. And so this is our essentially our partition omega is partition function q and in this whole transition we do not we interaction is already taken into account by forming monomers bond as I told you that is essentially maya function. So we all we need to find out how many ways I can form this and then that is that exactly maya theory omega n to the power omega n by n factorial omega n is what you call the n or maya cluster integrals so it is exactly maya partition function. And then we need to know what is the maya here remember in mayas theory we did omega n or bl in terms of the irreducible cluster integrals by time so that is now done in this case the omega n is evaluated and can be evaluated directly and that is I will give it here. The story goes in the following maya theory I told you the relation between cluster integrals the maya did the expression of the maya cluster integral q in terms of reducible cluster integral bl but the derivation of bl in terms of beta k was highly non trivial and that was done by his wife. And the maya gopard maya got the Nobel Prize later in nuclear shell theory who was didn't have a job because those days women it was very difficult for women to get a job so and she was she came from America and then was in Colombia for some time they moved to Chicago in Chicago she was not doing the job in the beginning. But it was the maya gopard maya who helped stock maya which is in stock mayas 1941 paper that is that is acknowledged that but she didn't want to become a co-author of the paper. So omega n neither was she co-author of the maya's paper. So those days the women many times did not get the due credit the dessert that is something which one of our famous scientist Dan Frank repeatedly brings out these days that many of the things in old days were done actually by women and that were not given much credit but whatever. So this is the expression in terms of the f and n and when you do that put this do that should be f n mistake f n minus one factorial so there are two factorial actually one factorial sign is missing. But when you do that now you have to do exactly like in maya still you know why now maximize the omega that's this thing you know in statistical mechanics same as many magicians of free energy. Maximization omega is same as maximization of entropy and that is same as many magicians of free energy and when you do that I get a beautiful relation which is in terms of the most probable distribution which is actually parallel to the one maya's case. Maya's ML maya's theory that has now that where there comes a fugacity in maya's theory here that quantity is by zeta and beauty of that I can now evaluate e and zeta and the a is the following expression what you have. If n one minus alpha square by alpha and alpha is the extent of reaction very common in chemistry that means how many the number of function. So if I don't bring that's why absent problem polymer cyclization comes on and as an hypothesis so then alpha is to you can easily convince yourself this is the fraction of because each each reaction consumes two functional books that's why you see the factor of f total number of function so extent of reaction to n minus m by f n that's the extent of reaction and when I do the minimization with Lagrangian multiplier then I get the f n one minus alpha square by alpha so one does exactly maya's theory one does the Lagrangian multiplier parallel all these things then now I got the even star now I can do some science what we measure in experiment like in viscosity is the weight average molecular weight that viscosity diverges so I now do first I define okay I know f n so I do what is the weight fraction of an n minus m what is the weight of gigantic cluster that is going to appear here what is the weight of n mark that is m n by n and then I put this m n expression here last equation and I use the a here and then I get I get made a small transformation of variable zeta the main expression here last equation and I use the a here and then I get made a small transformation of variable zeta to the power n there is a f to the power n comes that becomes x to the power n on the extreme right of my right hand side equation and fn minus n factor so that is wn okay so I go by I want to correct little bit this is f to the power n the n that is subscript here should be superscript is a power okay then I get this equation then now whatever is molecular weight this is the omega wn is a distribution so I know to get the normalized distribution I have to multiply by n and sum over wn over all n multiply by wn sum over all n when I do that this sum can be done and this is one of the another two the force and the beautiful result of statistical mechanics that I get this beautiful expression of weight average molecular weight which is observed by light scattering observed by viscosity and all other experiments now look at this beautiful equation there is something very nice about this equation and some unusual when alpha into f minus one equal to one I repeat when in the denominator on the right hand side extent of reaction increases such as that alpha into f minus one become one then the denominator diverges so when the extent of reaction becomes one over f minus one then f minus one alpha equal to one so that extent of reaction when polymonomers react to that extent increase as it is going on reacting reaches one over f minus one that value then it diverges and that is exactly what is shown here that that weight average molecular weight is undergoing a divergence so plot of a system of tri-functional unit where this becomes this extent it diverges and extent of reaction in tri-functional unit f is equal to three so three minus one is two so two into alpha when alpha become half then for a tri-functional unit this diverges this is where you find this divergence into the A things it is exactly like similar density theory now so summary of this so this is essentially same as appear in some of the liquid phase and this is one of the beautiful theory where Flory used it first then the stock mayor did it and as so we need to I just briefly summarize you polymer that we done we have done the end grain distribution and polymer size then we have done theory of polymer solution which has been remarkably successful and it can explain polymer swelling it can explain polymer collapse it can say this crossover from swelling to collapse at the theta temperature and Flory stock mayor theory of soldier transition essentially the application of a mayor's theory to polymerization and stock mayor was a student of mayor but also worked with Flory and he but Flory already did that soldier transition Flory did that but stock mayor used to make it more rational by using the mayor's theory and that is the very nice and they told you Flory was given Nobel Prize single Nobel Prize in 1974 people say Folkenstein should have shared it but but given the Flory's contributions to gigantic because he not only did the theory of polymer size distribution the theory of non-ideal polymer that is into the new new country by five the theory of polymer solution which is Flory against the soldier transition that is also Flory so that is what he was justified to give Flory the single Nobel Prize to summarize I want to tell you that this theory essentially almost like the one that we did in the course is essentially is a celebration of Flory called Flory who as I told you in the beginning was a remarkably human being who not only just did this wonderful work he did work in many other areas biology in many many places the Flory theory Flory is that's why he is also very important and respected name in biology and he is a humanitarian with a lot of workforce scientists in underdeveloped and condition countries and under difficult conditions so look up the Flory's theory of polymer look up the Jan's book of scaling concepts in polymer physics which is takes many of the Flory concepts to a much higher level and last I say the one of the reason probably Flory was given in 1974 Nobel Prize though many of his work were done before 1940s and 1950s reason was that in 1970s just after critical film and a theory was developed by Kenneth Wilson, Benjamin Michael Fisher and all these people and that is the time 1972 Dijan did a wonderful calculation of polymer excluded volume he mapped it into a magnetic problem and he could essentially do renovation calculation of the polymer problem Michael Fisher extended that and they discovered all the Flory equations all of them they discovered that yes it means square size scales as into require u and u is 3 by 5 for three dimension and half for three dimension then they discovered the Keta solvent polymer collapse so whole of Flory theory was developed and derived by using much sophisticated methods of polymer physics by Dijan Michael Fisher and some other people in France, in Germany and that probably can be realization that this what Flory need goes far beyond just the polymer it is a beautiful theory of statistical mechanics a contribution to statistical mechanics multiple comes to be contribution to statistical mechanics of interacting system okay I stop here today this is the last lecture on polymer and I strongly recommend you to read our book my book and the other two books also okay I hope you enjoyed and thank you for your attention bye


This video is brought to you in part by TrueTechTools, quality tools, essential support. What's up guys? So today we are going to move this old condenser unit here. The compressor's bad so we're going to put a brand new compressor in it. We're going to yank out the unit here and they're going to yank the inside units out. We're going to move it over to another warehouse. Get it moved and we'll get the compressor which it was out of refrigerant. So I'm hoping it was recovered already. If not we're going to put a pressure test on it either way. Seals from that back onto over here. Notice this on the discharge. I've never noticed that before. Looks like it's a restrictor baffle plate on the sockets for the I need it to perfect out of my client's set there. Okay inside there we have gaskets. All the gaskets we need. Other compressors changed to 1340k, 3R 22M, SK800, TSK800. So we've got a match and then voltage 208 460 volt. That's why we've got all this wiring here we've got to do. So we've got to wire it up for 480 volts. So it's going to be adjusted so that you've got the correct wiring which the other one you can see what they've done here. This is the pattern so we'll most likely have the same thing then we'll put our bolt lugs there and that's what that's how you know what voltage is for. Ended up being right around a 1 inch mark. This little kit here has actually been kind of nice. It's not very expensive. Got me all the way up to inch and a quarter. Got the oil safety out. You can see that thing's got a lot of crap in it. So hopefully that comes with the new copper seal. We're going to go ahead and clean that out with some brake cleaner. Obviously I'm not using my GoPro at this given moment but definitely use the box wrench on that or a socket. You don't want to the crescent wrench. We'll screw it up. Looks a lot better than it did. That's for sure. Spray it inside, back side. See the kind of oil we're putting too bad. That's why we had some operation on there. I'd say for one of my most favorite toys for five bucks or whatever it is from I don't know. I like this because it fits my drill. It's got the hex head and stuff instead of this regular drill. That one right there I get from Lowe's on average. Anyhow we got this completely cleaned up. We're going to go and put a touch of nylon on it. Can you get away without it? Sure but it's a brand new compressor. I want to try and make sure everything's done extra special that way. We don't have any problems. All right got that all jizzied up. Get that back in there. Everything's clean on my corners here. That seal I went ahead and put a little bit of in. So good to go there.  I don't know. It fits pretty doggone good. That's what's kind of nice.  But it's a nice set. It seems to fit. I mean everything's pretty. I mean you got a little bit of play there. Not granted I mean I'd be one full inch but either way I mean this little set gets pretty much most things you're gonna need. We've got seven and four. Boom boom boom. It's that same thing across the line 48460 which is what we're rolling with. Here's part to start winding. That's why they had that's a four deals there. That's when you energize one contactor then another contactor to kind of get the thing going. It's for big big units. You got your condenser fans. That's not good. What do we steal out of that? 480 to 240 and then coming down to as low as either 240 or 120 depending on how it's wired up. So here's the 480 volt section that's wired to there. So that's how they're controlling their contactors and stuff all that there. Now we've got that was unhooked. I'm hoping that's where it went most likely is. That went to a relay. You can just see that honey well looking relay or whatever brand you want to call it. There's that extra set of windings I still need about for partial start and it looks like they had a contactor at one time but it's not how they're doing it now. Then over here's all our first switches and clocks and miscellaneouses. There's our Centronic. That's that sensor we just switched over reset on. That's nice. The rubber's starting to take a dump. There we go. Got a delay here. It looks like it's been bypassed. It's always great. Hopefully they didn't jack a ruining too much stuff. Gonna get a brand new contactor in there anytime you change compressor. Three phase especially contactor brand new. This was started up back in 08. So it's just like a spring chicken. This stuff is expensive guys. If you just do residential and stuff you would think yeah I would just put a new one in there for 10 gram, 15 gram. No, no, no. That's usually why I'm fixing a lot of this stuff.  Plus they already own it. So why not just go ahead and do it? Use what you got. Why not? And besides getting paid to do the job just do it. Whatever. I want to kind of hold off on opening the compressor the very last minute. So we'll go ahead and fool around with the electrical. Somebody asked about these.  But they got a gel this time. I usually go with the foams. They usually last longer. The gel is sold up pretty good. So we got to the electrical section here. We got that there. That helps keep it from twisting left and right. Here is our aluminum ordeal there. You get all these in place. Those bolts are already tweaked down. And then these have like a lock washer already in there. And then we got our jumpers here. That jump. Winding to winding. Now these windings right here, these lugs, literally go into the compressor right through here. So that's why a lot of times we'll check in that area to see if you got any leaks. Because it can leak through there and you can replace the seals. Okay that is a 716. These are made to be ran in your drill. But I'm not going to run my drill on this. I don't want to take a chance of getting too over reambunctious here and screw on myself. So we're going to hand tighten that thing so that we can tell where our torque's at. And the smaller the wrench you use, the less likely you are snapping it off. One thing I see here, they got to connect back to the new one there. And you really want those marked. Somebody did do it somewhat. See it's got two marks. That one's got three marks. That one's got one mark. So the blue ones are marked. Make sure if you do use one of these screw drivers, which is the right screwdriver for knocking stuff out. But definitely the wrong screwdriver to do any electrical work. Because that shaft goes right through there and we'll shock the living snot out of you. Not that this camera does real good, but you can see we're jumping seven to four together. So by doing that you're basically making that one longer wire. So you're going down here seven to four and boom to there's one. To five comes a long boom. There's to two. And nine to six which then comes around to that terminal there. So here is our motor connector stuff. L1, L2, M1, M2, sensor 1, 2, and 3 and in common. Inside that manual basically got two power wires going to that motor protector. And you got two wires basically for the switching to break the contactor. So over here's the module coming into the service mate here. I've already hooked one side that I removed from there to my meter. I wanted to make sure that I knew which one was my module. So by taking my meter over here, I just wanted to verify and sure enough you can hear it beeping. So that's the one lead right there. That's your motor protector right there. We're going to go ahead and do that and then we'll figure out which ones are power wires. That's how we're going to fix this up so that we make sure we got it wired right. So many wires that are dangled here.  You get onto something that somebody else has been doing a lot of work on and you can tell this unit was junk. I mean it had a back compressor. So people steal parts out of it. This is the other one. Let's see which one that one is. Worst case scenario I'll get this thing wired back to there and I'll just pick two wires and make sure I get power to it. There it is. So that's the other one and that one was labeled number two. So we know for a fact that the control circuit is these two right here. I feel confident that that's correct and I don't have to worry about that being wrong and possibly damaging something. All I need to make this thing roll is two wires for the power module. The module's power and we'll see if we can figure out which of these wires we're doing that. You would think though that it would have been just open-close switch only because basically what that does is it reports back to here and you can see if it's tripped and then you can also put your meter leads in between there and you can actually measure to see if the switch is open or closed. Yeah this is just scary because you're just like man isn't this right. Control module goes to M1 M2 which is what we hooked up to which should be normally closed they're jumping it to the other mod so that's number T2. Look at that number three so that was correct. I just did not want to aimlessly go blind in here and just stick it wherever and hope it worked and then all of a sudden you know bad things have happened. It's really hard to get the smoke back inside of it after it comes out. Going here off 16 comes up over fuse one there's T1 T2. There's T1 T2. Let's see if we can get that probe to stick in there on one of those back probes there. Yeah let's speed terminal one. Boom got it sweet so we know we got that right. Makes me feel a lot better. Now for the other ones and this could all have been avoided if I would have paid a little better attention to it.  I had guys that needed to leave and go deal with some other storm damage stuff somewhere else and they were trying to get done get the crane out of here to get somewhere else and you know you're trying to hustle to get it and then that's when you make mistakes. That's why I don't get any huge hurry about stuff. I never have. I try not to. It just does not pay off to get in a huge hurry. Yeah I don't know if I like that. That was the way the other person had it. I don't know if I like it at all. It makes me a little bit leery. The thing I worry about is it might vibrate into the plate or something stupid and I have always liked these type of allen wrenches because they're easier to get into tight spots most of the time but there is sometimes where they don't work very good. Now we can tuck these other ones down. I was going to chop them off. I was really tempted to do it. It's like you know what they can pull new wire if they need it.  Clean the bottom of our discharge service valve there and that one there so they're all clean. Trying to get this compressor opened up as a very last thing. Put a little nylog on it here in a second. What we have here I completely forgot we yanked some pressure switches out so we got pressure switch. This is what one of them is. I got a blue one there that was wire nutted off beforehand so it's probably just pressure switch only. Transplanted this so we just swapped the gasket over and so we've just taken this all apart. No not at all. Now do I need to put any? Yeah we've got some white stuff there. I got some pipe dope. You may have to take the cap off of it. I don't remember I didn't cut it or what I didn't do. If it don't come yeah it does come out good. We got this in there we got that new seal top and bottom of the seal we got the nylog on it. I went ahead and oiled my bolts there because I wanted to you know just that way I got nice tight so anyhow without you know seizing up so we got this here. I popped this I went ahead and front seated that valve so we're actually isolated so we're not just setting up absorbing moisture so that's what I'm gonna do for now so I'm gonna go ahead and peel this off and then we'll go ahead and get that new one on and then we'll go ahead and finish wiring things up and then eventually we'll start getting this system under pressure and we'll do a leak check on it. All right so we got everything back together here we're going to purge nitrogen through the suction it's going to come out through the valves right out the front here and it's going to at least break any air we got in there and then we'll start working on the other side. So you can push through the valves no problem hopefully pushes most of the air out of the system because these valves the way they are when you're front seated cranked in you're open to the compressor so we can do a little bit more and then we'll pull off I don't need something stupid mount on there just to keep it in a positive okay at least it tells me what I'm leaking around my seals there they're about 25 so let's go ahead and see if we can get this cap on there before we lose all of it yeah we keep her in a good positive once again front seated open to the back side to the opposite to how residential crap is where you actually have access to the line set we don't have that on that so we're on that direction there wouldn't hurt to have a newer sight and glass indicator there we'll say something about it we'll see whether it happens or not we didn't have a lot in that one bottle this one here already just about 1500 yet we're only 100 pounds sprayed a little oil on that to see if uh see if we can get the cap on a little snugger yeah it's real encouraging when the oil's bubbling on top of it yeah no leaks here bud no but no leaks at all here no nothing to see here look at all better now no leaks now all better didn't feel like going back to shop and grabbing the big bottle but they said well probably needed that's what we should have but I was able to tighten that packing nut sprayed it with soap went ahead sprayed in my filter dryer some of the other fittings down there sprayed all my high side stuff over here a little fitting down there on the discharge sprayed my receivers up here looking for big stuff when I come back and they actually got everything hooked up I'll do a full-fledged pressure test they're gonna pressure test the evaporator separate from the system as well when they get those taken down that's where we're at on it I think we're about ready to wrap this thing up found one leak look at that right on the discharge that ain't good that's it not good you wouldn't think it worked but you give it long enough it'll show up don't really see anything on any of that we did get the contactor replaced got its 75 on there got the date on it everything's cranked in electricians have got that part done new conduit ran oh wow it's not even tight all right so it's a funny looking flanger because it looks like it kind of gets thin in the middle kind of goes out on the edge let's go and squirt that again and then thing is I don't want to lose my nitrogen otherwise I just throw a seal on it right now I'm pretty sure I had an extra circular seal that would fit just fine but I don't want to lose my nitrogen that got on it nice and solid stream a little there go a little on the packing area a little packing here make sure a little bit here on the front all right guys I didn't do an ending there that wrapped the day up spent most of the day there doing that so I hope you guys enjoyed the video I've got to go back and finish it up so I'm assuming that might be somewhere in the mid week has to be done by next Friday so anyhow I appreciate you guys taking the time to watch the video and until next time we'll catch you on the next one later


Hi, my name is Velkika and I'm an actress beside of California and today we're going to talk about full body slates, full body shots because sometimes they're going to ask you to start or end with a slate of your full body. And sometimes they'll ask for photos of your full body if it's for a commercial or they want to see what you look like, what your body type is like. And I have struggled a lot in the past with figuring out how to make my body look like my body in photos or videos because sometimes if you film from too high or too low, awkward angle, it does not look like your body. And finally in the last, I would say six months because I've had to do it so much, I have figured out where exactly the camera needs to go, how far from me the camera needs to go for me, my body type, my height. So I'm going to tell you what works for me. So first of all, when should you do a slate? Should you do it at the beginning at the end? Should you do it every time? Only do it if they are asking you to slate. So when my agency sends me a self-tape audition request and they say slate at the top of the audition, your name, agency, and where you're located, then I do it as if right before I'm going to film. So if I'm going to film a monologue like this or a scene like this, I will start with, hi, my name is Belhika, I'm with Marla del Tallinn, et cetera. I'll do it like this. If they ask me for a full body shot slate, of course that's when I do it vertically. And usually my agents will let me know in the email every time that it's okay if it's vertical, but only for the slate, only for the full body shot. Sometimes for commercials, they don't want you to say anything, they just want a few seconds of a shot vertical of your full body. So if in the self-tape audition request that they sent you, if they doesn't say anything about slate, then don't do it. If it just says slate yourself, then you can decide what that means for you. People have all kinds of opinions. Usually it will be your name at the very, very minimum. I usually default to my name and location based on where I am submitting to. But I also have a video all about slates, all about all kinds of different slates because in theater, we would always slate with our name and what we're performing. So you can see that video for more information on different kinds of slates. As far as a setup for your full body slate, please have something plain. I like this paper backdrop just because it looks nice, it looks professional. As my backdrop, I have a gray paper from Savage and I will link everything that I use. I always link everything that I use in my description. But my backdrop setup is about $80 and you can also use a blank wall if you want to, if you would like, or if that's what you prefer. This to me just looks really clean, it doesn't make it feel like you're in your room even when you are in your room. Ideally, I would use this in my living room because we have hardwood floors over there and there's carpet here so that I can put the paper out and it would look like a seamless. But there's carpet in here and if I step on it, it's crunchy. And if I put it out there, there's no carpet. So it's really echo even with the microphone that I use. But this is my setup right here. For your full body shot, you just want to keep the attention on you. So if you can make it nice and clean and flat behind you, then do that. If you're having somebody else film this for you while you stand over there, make sure you have them go and slate. So just have them stand there and say their name and you film them so you can tell them exactly what it should look like. You know, like, oh, make sure you don't get any of the corners. Like if I was filming here, I wouldn't want them to get this bar on the side or any of the white wall. I just want the gray in the back. And then I would tell them, I don't want too much above me. See how I just left a tiny bit above you. That's what I want. I want to be able to see my feet. Make sure it's not from too high to low. I don't want it to be distorted. If you're using a tripod, that will be the easiest thing. And if you're an actor, that is the best investment that you can do right now is get a tripod because it is such a mess to try and film without a tripod. And make sure that it's one that is at least as high as your chin because for full body shots, you are going to need something that's a little bit taller.  But depending on your height, you might be able to use similar distances as I do. I'm 5'10 and the phone is about six and a half feet away from me. It's on a tripod and the camera lens is about halfway up my neck. So if I was to walk straight at you, the lens would be right here. And it is slightly tilted to the bottom so that you can see my feet and there's only a little bit of space above my head. And then this is how I would slate myself as a full body slate. Hi, my name is Belgica Rodriguez. Can you pan in order to get a full body shot? Usually no because you want to see what your body, your entire body looks like. So if you pan up and down, you're not showing very much what you look like as a whole. You're just doing part by part, but some people accept that. Some people are okay with that. So if, again, if in the email it says that you can pan, then that's okay. Then they're giving you permission. In general, if they're telling you something specifically for that audition, then follow their instructions because that's how they want it. There's really no one perfect, amazing way that will be able to make everybody happy. So make sure you are following the directions that they are giving you. Because I have seen YouTube videos of actors in different countries where they do entirely different things. So just make sure to read the description of your audition at least three times. And you should be filming your audition like this horizontally, also known as landscape.  Because for me, I could not do a horizontal full body shot in my bedroom because there's not enough space. And if you're doing a full body slate, this is something that I've never heard good or bad things about. This is just something that I have done so that it doesn't look like a photo. But when you're slating full body vertically, you should be settled and not jumping around too much because I've noticed that about me that sometimes I say, hi, my name is Belgica Rodriguez and I maybe do like a little bounce, not consciously. But I, it just looks funny when I'm editing. So that's something I don't like. Now, when it's a commercial full body shot, sometimes my agents will ask me to put a few seconds of a full body shot vertically at the end. And so it doesn't look like a photo like that. Usually just a tiny, tiny bit. Let me know if you think that's weird or what, especially if you're an actor or a casting director or anything. I move ever so slightly. I'll show you guys an example. So it's not crazy.  So if you guys do that, let me know if anybody says yay or nay to you because that's something that I just, I did in my head. Thank you so much for watching at the end of every video. I feature another channel. This is today's feature. If you would like to be featured on my next video, make sure you're subscribed, like this video and leave me a comment.


Anybody want to try? Anyone at all? I'm going to ask one more time, and then I'm going to let the show start. Were you a math major, sir? Physics. Stand up, sir. Come on up on stage, sir. Come on up. You too, sir. Where did you go to school? Where did you go to school? We have a translation problem here. English is not his first language. Where did you go to school? Williams and Penn. What branch of physics? High energy. High energy physics. Brookhaven National Labs. I was also over at CERN for a few years. And CERN. So is this as a civilian contractor? Yeah. Did you ever have an idea? High energy physics money comes from the federal government, generally speaking. So in that sense, yeah, I was getting money from the federal government very indirectly and in those days in very small amounts. So did you ever work with the space alien ships at Area 51? Nope. Did you ever do any contracting for the DOE? Did you ever contract for the DOE? I was way too junior in those days to have any idea in detail where the money came from. So I'm not going to tell you. I don't know. In terms... That's right. So you work with high energy physics, yes? Yeah. Would you work with the optics side of the house? No. Which side of the house are you working on? We published a paper in 74 about the discovery of a particle that had a mass of 3.1 GeV. How many people here have any idea of what you say? Our paper called it J and the other paper called it Psy. What's that? Okay, for those of you who raise your hands, everybody in the audience, feds.  Yes, sir? Have you played? Nope. If it bleeds, it's biology. If it smells bad, it's chemistry. If it doesn't work, it's physics. Can you explain Schrodinger's cat theory? Nope. Have you ever worked with a tokamak?  No, that was a little bit after I left PPA. Okay, so three letter agency. No, no, Princeton Penn Accelerator. He's reaching. What classified paper you published? Since I've never published any of them, it hasn't been published yet. Is it because they wouldn't let you? I'm afraid he's not a fed, ladies and gentlemen. Sorry. And we'll go ahead, and just for you, sir, we're going to start the talks.


Hey everyone and welcome to the this class the LPS class today, we will be again continuing with the Linux networking lecture number 6, in the last lecture we just introduced the DFS today we will be going on with the DFS the distributed file system, in fact I am going to actually we will start the DFS discussion today, last time we just looked at some introduction but I am going to repeat that material again and before I begin I think like I mean we had a good lecture on the DNS system, we looked at the email last time I am not going to recap that today, if you have any doubts you can always take it up in the next session or so, so let us begin the discussion on the distributed file system, again as I mentioned in the last class we will talk about the distributed file system what it entails, why is it big deal, we will go into the architecture again we need to know like why it is a big deal again, what are the issues with the file system, what are the issues with the file system and also we will take up like two case studies one is on the Sun NFS system and then the other one is Andrew file system again let us see like I mean how far we can get to but these are the topics that I want to cover, so last time we discussed the file system again the file system basically it is it was done it was developed for a centralized computer system and the desktop computers and file system is an operational operating system facility providing a convenient programming interface to the disk storage, so we will see like what are the gradations of file system or we have to understand the memory architecture before we go into the file system and a distributed file system specifically it supports sharing of information in forms of files and hardware resources across the network, so that is the key thing and then once we have this system like Corba or Java in the web this entire thing basically like how much we are sharing and how the sharing happened has become like extremely complex, so before we go into the storage system let us look at just the memory architecture I think like I mean this is something that you are familiar with so we have say like I mean this box represents the of the CPU and then there is a cache memory which is part of the CPU which is very very localized and in fact you won't even know the existence unless you look at the computer itself or basically like what the chip has in the control panel or any other place basically typically these come in various sizes right now we have one gig two gig we all measure in in terms of gig actually then we also have the the main memory this is an example will be like the DDR3 is very famous nowadays you get in two gig 4 gig DDRs sometimes like even the caches like I mean it used to be like in case now probably like in megs and gigs are also available and the memory of course like main memory in a heavy duty server it can go all the way up to like one terabyte also then you have like hard disk which is essentially the storage where things get written and basically it resides the programs reside in the hard disk before they get executed a distributed storage is nothing but so if you look at this particular box the box around it is a system or a computer and then basically like a distributed system is centralized for storage and that is shared between multiple of multiple computers or there are multiple disks that can be accessed by a single computer all through a network so now I mean if you look at the hard disk and a distributed storage apparently they are all the similar stuff so what is the big deal in like using a distributed system so let us look at some of the challenges so when we talk about the distributed file systems there are many many challenges that that may need to overcome in order to make sure that we get we can reliably store and retrieve it one of the issues is the transparency so as you know the data is written in various chunks basically so what kind of data in a hard disk is transparent to the host systems is it all of them is it some portions are transparent to some of the systems and some portions are transparent to another system how is that divided and then when there is an overlap like what happens so these are some of the things that we need to worry about because there are many many systems accessing the same disk storage now so again that is one thing that we will talk about then the next issue will be the concurrency issue what happens is two servers or two clients access the same files concurrent who gets the preference and why so these are the kind of questions that we ask about concurrency then the other one is replication which is when the server the file in a server changes can all the time see the change immediately or do they have to wait how do how does that work so again that is another thing that we will talk about then the fourth challenge is the heterogeneity challenge again in this one is whether the file system support multiple OSS so I am coming I am connecting with Windows OS somebody else is connecting with Linux OS somebody else may be connecting with the iOS OS how does the system behave in that sense and does it support all the OSS or supports some of the operating system how does it work then the other challenge is the fault tolerance challenge which is when the file system crashes how does the client know about that or if the client crashes how does the file system react say like I mean you are writing to a file area and then that the client crashes now what happens do that that that that area gets recovered or is it just all corrupted how does how what what what happens then the other one is consistency consistency comes from the different clients then they access basically the is that the what each client looks at from each perspective are they all in consistent view so that is another thing basically that we will talk about and then the security is another concern how do you authenticate a client or a user to a file system and so that I mean he can only he can access we saw like some of the high level issues regarding security in when we studied about the Linux basically next OS where we talked about the read write access read write execute access how does that work so here we will be that that challenge has been multiplied pretty heavily so we will look at that and then finally efficiency how do we keep wastage of the space to the minimum so are these techniques that we can employ to do this what do we do so again as I mentioned the classical examples are this some manifest from the Android file system so we will be learning about all these things so before we go into that let us look at the the main memory architecture which is essentially we saw this in the previous slide so let us look at it from the main memory onwards so we are not looking at the caches and inside whatever is inside the chip so main memory it is not it is not a shared memory mostly like it is local to that particular machine or that particular CPU and the persistence it is not persistent so persistence is another property essentially for the the data whether then the process die whether the data still stays there or not so usually what happens is whatever the program that is running in a process writes out the data into the hard disk so that the main memory is completely cleared of any of the remnants of that that particular process so so so what that means is basically the main memory more persistent memory so we do not keep anything after the process gets executed then by nature main memory is also similarly is very local localized memory so we do not keep any distributed cache or replicas so that is also no then the consistency maintenance again it tries to maintain the consistency and the the example essentially but it says there is still a one copy consistency for that you cannot replicate that copy across multiple main memory systems here we will call it main memory systems example is that RAM or the DDR is another one so those kind of things now let us look at file system file system again like you do not allow the file system to share but it is persistent meaning the data gets written into that file system after the process gets executed again I am distinguishing between program and process that this is the distinction that we saw very early in the course which is essentially the process is a running instance of a program I hope you guys remember again the file system also does not allow distributed or cached replicas because inherently like in this file system we are talking about is a file system within the computer so it is mainly for that particular machine again consistency maintenance is a quickly like one copy consistent system now let us talk about the distributed file system this is this is where it gets interesting we allow sharing in a distributed file system the data is persistent as we know and then it also allows the distributed cache essentially so that you can create replicas of data all over the place and finally the consistency maintenance is we will have multiple copies which essentially go through that consistency so we call it like approximate consistency so we know that I mean consistency is how each of the client will view that particular files and here it is it is almost there essentially some of the new information may not be there in the file but pretty much like I mean the copies are updated on a periodic basis so now let us look at a web server web server also allows you to share the data it is the data is persistent allow the distributed cache and replicas but there is no consistency essentially like if something gets updated everything is not looking at the same thing so one data may be old the other data may be new unless you keep like refresh the data won't be updated the distributed shared memory is another one so here again allow the share sharing of the memory but the memory itself is not persistent the way that we allow the memory is also through the distributed cache and replicas and then finally the consistency maintenance is also there remote objects essentially this is something that the corba supports and again here sharing is done and then it is just a one copy consistent so if you look at it I mean so the highest one is probably the distributed file system and then there is also the peer-to-peer storage system which is also very similar but the others are kind of they are lower in the hierarchy as you can see the persistent object store and also the the remote objects from the corba so let us look at the the next picture this shows like a layered more modular module structure for the implementation of a non-distributed file system so here we have a directory module and then a file module then the access control module file access module a block module and the device module so let us let us just look at what each the function of each of them the directory modules is essentially like I mean that has all the file handles that are in that particular direction so this is the each of the file IDs the file handles are also known as a file ID so essentially the file names are related to the file ID with using the direction module the file module keeps all the the file IDs and correspondingly like body the file where is it located and all those details the access control module is the permission checker we already know that there are three types of permission the read write and execute so the access control module is the one that checks for these permissions and whether certain operations are allowed or not allowed the file access module that essentially is used to read and write file data or the attributes and the block module essentially like now accesses the file system or essentially the disk and that goes and allocates the blocks that are needed for this writing the file and then so basically like I mean the blocks are usually chunks of some number so that based on the file size or estimated file size it allocates some blocks for the particular file in the memory and then the device module is essentially like I mean now that is pretty much it is the module that accesses the disk does the I use and also like the buffing so whenever you are reading the file it takes the file ID essentially like I mean that particular disk and it gets the file for the through the buffers it takes the buffers again the file systems essentially like I mean so that provides the organization storage retrieval naming sharing and protection of all the files so a file contains the the data and the attributes so now let us look at how the file records are record structure or how a file record structure looks like so the key things that we want to write are the file length and then it was created a creation timestamp if it is read multiple times or when was the last time it read it is read that is a read time timestamp after creation when if it is written again then the writes timestamp and then there are some attribute timestamps and then the reference counts and then there are some additional ones which is the owner the file type and then the access control list so this is typically the record that is kept as part of the file and we can actually access various various form parameters to get to where what the value is so these are done through the operations essentially so let us look at some of the operations so here the operation is open open is the name and then the mode so it basically opens an existing file with a given name and then assigns the file ID to file destination create is another operation with the name and the mode and this one creates the file with the name in that that ID is assigned to the file ID file this so the the mode can be like read write or read write and then close the file destination or the file handle closes that particular file in any of the open files and then if it can close then it assigns the status as 0 and if it cannot close then the status becomes 1 so based on the return value we can decide whether the file not closed or not and then the count essentially like I mean this is actually like I mean the operation is the read operation read file this buffer n it essentially transfers n bytes from the file to the buffer and essentially like we can also like measure that in the count now the write again file destination buffer n will transfer the file actually like I mean the the n number of bytes are transferred from buffer into the file that so these operations essentially like I mean they deliver the bytes and they also advance the read write pointer so the pointer is essentially like I mean what is in the file so that you know like I mean where exactly that is and then L seek is given offset and the and another param called when using this parameter it goes and moves the pointer the read write pointer to that offset and then unlink essentially like removes the file name from the directory structure if it has no other names it is just deleted otherwise it is basically like it just removes that name alone the other names are kept and link name one name two again this adds a new name or name two to the file name one and then the other one is the stats command this actually gets all the file attributes we saw that here essentially this one the attribute count and then the attribute time step so in all the attributes are it is taken and then put it in the buffer so we already saw like I mean so the requirements itself like I mean we know that these are the challenges and that is what we need so let us look at the file service architecture this actually offers a clear separation of the main concerns in providing access to the files and it is obtained by structuring the file service in the three components so there is a flat file service a directory service and the client module service so again this the file service architecture is a way to organize the services that are associated with the files so that things are provided properly so now let us look at the modules in the file service architecture so imagine the server computer sitting somewhere far away and then they it is connected to the client using this link is essentially like some kind of the network and there may be like more clients sitting there which are accessing the same data and essentially like I mean so when the client tries to access the flat file service essentially like I mean it is just associated this and directly like I mean it collects the data and sends to the client and it is almost like I mean you can think of here the client computer is accessing just as a one-on-one with interacting with the file services so there is a directory service and a file service and basically like the flat file service collects that file information sends it to the flat so essentially in a flat file service all the the files are assigned a unique file identifier or UFID and so since the file themselves are uniquely named it is easy to actually obtain what the file is and essentially like I mean so one system that is accessing one of the files the other systems may not be able to access that same thing every every file has a unique identifier and the clients need to know that unique files identifier in order to access that file so the client there is a client module that exports the interfaces by the flat file and the directory services from the server side so the directory service itself it is provided it provides the mapping between the text names of the files and their UFID so the clients may obtain the UFID of a file by coding its text name to the directory services and these are all like one-to-one mapping so so that that is the uniqueness of the flat file service it is not very interesting and as you can see actually the UFID can be a long sequence of bits because if we need to map all the files in the file system with unique identifier it is kind of an obvious task anyway so the client module that is another piece of the services that we saw in this picture this runs on each computer and provides an integrated service or a flat file service because this service is pretty much constant or same across all the clients so the client service in fact in the unique side actually emulates the full service full set of unique file operations these are the operations that we saw like earlier like open close and all those things all of the services are provided by the client module it also holds the information about the network locations of the flat file and then the directory server processes so that it can actually go to those directory servers and access those files very easy it actually is better performance through implementation of a cache of recently used file block at a client so we can improve the performance of plan module by having a cache a local cache within that particular client in the system that we store the recently used file block again the issue will be how do we maintain the consistency and so we will talk about that so here some of the again commands that we can use the read field i, n and then that goes into data essentially so this is a dash and arrow data here essentially like I mean we read a sequence of one through length of file and the variable is i which is essentially like increment that and then basically like when and then essentially like when that particular items are stored in data the write field i data essentially it writes a sequence of data into a file starting at item i and extending the the file if necessary and create is another command that creates a new file with length 0 and delivers a ufid to the field variable and delete field just remove that file from the file store get attributes field and then store we can store it into another variable called attribute and then set attributes essentially like I mean that essentially like whichever attribute that you specify is set to that particular field which is essentially I mean sorry file ID which is the the unit ID that we have found out so again the access control so in the distributed implementation access write checks has to be performed at the server so it is not a client that provides the access control because the remote process control interface is unprotected point of access to these files essentially so until you reach the server basically like it is all unprotected and then basically looks for the access control itself is provided at the server side directory service interface essentially like in that we will look into it now so here there is a look up for particular directory with the name and that returns a file ID and if the name itself is not there in the in that particular directory then it throws an exception so that is the throws not form in the add name essentially like add the name and call the file into the particular directory and if there is a already that name exists then it throws an exception unname directory name is essentially like the name is in the directory then it is removed from the directory if it is not there in the directory then it throws an exception and then finally the get names directory pattern get the text names in the directory with a match of the regular expression pattern we will learn about regular expression in the future modules in one of the programming modules and then that is assigned to the essentially so now we go into the the next file service architecture which is hierarchical file system so right now we look at this a flat file which is very easy to implement very easy to access but at the same time you cannot do a lot of functionality there and also you need to carry along the unique file identifiers which just causes issues by growing your directories and growing the client modules now let us go into the next one which is the hierarchical file system this is essentially like I mean is the file system where the the directories are now arranged in a tree essentially so essentially like you need to go into like various directories in order to figure out what is going on and then also the file group is another concept there where it is a collection of file that can be located on any server or moved between the servers while maintaining the same names so we saw some of these examples in the originally like started Linux a similar construct is used in the in a unique file system it helps with distributing the load of file serving between the servers so essentially like I mean you can move the file system or the file group to be closer to where the clamp is asking for so you can move to one of the servers also the file groups have identifiers which are unique throughout the system so that is that is the way that it can be moved from one system to the other so here is one method to construct a globally unique ID so we just use some attribute of the machine on which it is created so basically like the IP address so we know that IP address is 32 bit or a four-acted binary we just add a date to it like so the IP address followed by date we call it as a unique identifier the date could be a date and time all the way to the second then the file gets created so now we go into the distributed file system so again the three hierarchies that we talked about are the three different types of file system that we talked about the flat files the hierarchical files and now we go into a distributed file system so here we will talk about two main file systems one is the NFS of the Sun NFS this is the this was developed by Sun macro system in 1985 it is the most popular and it is open file system and it is used pretty much universally today also the NFS protocol itself is standardized through this particular standard is known as the RFC 1830 so the main idea is the here is basically the server the file system itself is a stateless system so essentially like I mean the server itself is not required to remember anything so it does not have anything in the memory essentially the things like which clients are connected which files are open things like that so essentially like I mean just the file system itself is sitting in one place the signs basically are sends some requests essentially with all the information that are needed and then basically the server just fulfills the request and then this forgets the minute it fulfills the request and then moves on so the onus is on the clients to provide all the information that are needed for accessing a file or essentially need to provide that to get that service so the whole so the advantage of this kind of a system is that the server state does not even does not grow with more number of clients so there is no change to the server itself which you need to change the number of service and then the other key idea of NFS is then you perform an operation and if you are repeating the operation you get the same result there are no side effects so essentially like I mean if you say like a equal to b plus 1 and then essentially like every time you do the a basically like I mean it is always it you get only like a equal to b plus 1 or you do not get a equal to a plus 1 there now the state of a is different so that the next time you when you query it is a different answer the second system that we will study is the ASS of the Andrew file system this is developed by the Carnegie Mellon University as a part of the Andrew distributed computing environments in 1986 so you can see that actually they are fairly close the this research project was to create a campus wide file system and basically a public domain implementation is available on units it is called the Linux ASS so this was again also adopted as a basis for the DSS system DSS file system in the open software foundation and the distributed computing environment essentially so let us look at the NFS architecture the NFS architecture consists of again the client computer but as I mentioned the client has a lot of owners on providing the data so let us look at first the server computers server computer has nothing but a virtual file system which has the which holds the unique the unique file and then it has an NSS server which is another program that serves the various clients and then in the client computer again like I mean you have the same kind of things there is a virtual file system which has the unique file system and then whatever the extra ones here basically the blank ones are various devices slash depth and then there is also an NFS client the NFS client talks to the NFS server basically and provides the information as what the files that it retrieve it wants to retrieve or write the write the content into that file they all these programs actually like they all the same under the Linux software in external the communication between the the client and the server are using RPC what are what is known as the remote procedure files essentially so the client itself basically it is a it is a transparent access to the NFS file system so when you go through this NFS client to the NFS server since it is stateless basically like it has it like this is now connected together and there is no NFS server and then a plan and basically it is just you can transparently access whatever is inside the unique file system server side as well so the client's job is essentially like going to basically provide this file system and also the transfer and access to the NFS it also provides some virtual nodes essentially which is essentially like procedures for procedures on an individual file or it is an interface for procedures on an individual file and then basically it translates that the individual file procedures into the various NFS remote procedure calls so that way like I mean it can access the NFS server and retrieve that file so here essentially like the application program provides the unit system calls through the unit's kernel and essentially like I mean the operations so they all the virtual file system just keeps all the operations as a local operation so you won't feel that actually there are some remote files also so from the application side you are just calling a local program but the virtual file system identifies which is the local and which is the remote files and then the remote files are handled to the NFS client and then it provides this RTC into the NFS server to retrieve that file so the file identified we already introduce this concept of a file handle the file handle is the file identifier that I use in the the NFS itself so here a particular file handle denoted as FH could be the file system identifier the the node number and then the I node generation so so all the all of them are combined together to get to the file handle so the various commands are used here so in this one there is a read operation we again like very similar to the flat file access give the file handle or the file ID the offset and the count and then that retrieves the data and put it in the the data variable the write for writing basically we give again the file handle the offset the count and then the data and then basically like a minute is written into the file system and then basically like this an attribute that is written the create command essentially where we specify a directory file handle the name and then the attribute and this command returns a new file handle and also some attribute attribute on the file and then the remove actually is remove just return the status the remote or not again we give the just directly file handle and then the name by name the get attribute file handle gets the attribute related to that particular file then the set will set that then there is a lookup command essentially which returns the file handle and then the attribute rename command it is basically the original name or the from directory file handle and the name to the to directory and then to name link provides a link to the existing file then the read there essentially read the particular directory and then returns all the value into this variable entries same link is a symbolic link you are a soft link which ties a file to another and new name and then that returns the status the read link file handle essentially like that returns a string essentially so it gives this back is the expanded link path make there is it creates a new directory and for that it gives you the new file handle and then Rmder basically removes a directory and then stabbed file system file handle gives the file system status essentially so these are some of the commands that are used in the some NFS which is one of the very popular system. So now let us look at some of the other features of some NFS in fact we learned about this one one is the security or how do we make sure that there is an access control and authentication so as I mentioned earlier the NFS server itself is a stateless server which means that the user's identity access right all of them are controlled by the server only on the request and essentially the client is so the local file system they are checked only on the files access permission attribute so essentially like I mean this is beam we have to check every time whenever we access the file system so it does not remember like I mean a particular user is authenticated or not so every time you need to check again and again also the client request is accompanied by a user ID and the group ID these are inserted by the RPC so the remote procedure call we talked about this also like earlier like example there the virtual file system converts or basically like it forwards the remote access to the NFS client which converts the file handle into the particular remote principle which contains these additional data which is the user ID and the group ID and then then it sends it to the file system to gather that so the Kerberos is also it has been introduced it has been integrated with NFS and that provides stronger and much more comprehensive security so now let us look at the mount service mount service is used to mount a particular disk into the file system so if it is a new disk we use the mount function to do this to mount the remote files so the operation is mount remote host remote directory and the local directory so it basically like mounts that file system into the local directory in this example the server maintains the table of clients whichever ones mounted the file system each client maintains a table of mounted file systems holding the IP address the port number and then the file handle the remote file systems may be hard mounted mounted or soft mounted in a client computer very similar to the soft link or hard link so here another example where it shows the two remote mount files so in the server there is a directory called people which contains like big John and Bob in the client side there is a directory called user which has students which are remotely mounted on people and then there is also another directory of staff which is a remotely mounted on staff in actually in users in so too then there is also a concept of auto monitor the auto monitor was added to the unique implementation of NFS in order to mount a remote directory dynamically whenever an empty mount point is referenced by a client so this is kind of the client ask for a particular node which is empty by default then the auto monitor automatically mount the particular remote directory there so again the auto monitor has a table of mount points with the reference to one or more NFS servers listed against each so it sends first a probe message that each candidate server to see whether the particular mount point is still available then it uses the mount point to mount the file systems and then serve the apartment and usually the auto monitor keeps the mount table to be very small so this also provides a form of replication for read only files so let us look at the caching essentially recommend so caching can be of two forms one is a server side caching and then also the other one is the client side caching before we go into the server side caching let us look at the client side caching the caching always is it provides improved performance because certain blocks if you cache and basically goes out of the lock and the client request that every time the cache can provide very quick access to that particular block so that the system that is requesting that is not starving for data so for reads essentially like I mean for the always the the protocol from the client side is checks with the local cache before goes into the server because whenever we go into servers it can take longer time whereas the local cache will be easier so only if there is a cache miss it goes to the server but at the same time writes basically you can the most or the Sun and X itself provides the periodic writeback and not an immediate writeback to the server mainly the the reason is we do not want to contact server that often because that can slow down the communication network so the client caches two types of data the one is the data block itself and then the other one is the actual now let us look at the server caching basically so the server caching is very similar to the unit side caching in the local form so the various blocks from the disk they are held in the main memory buffer cache until the space is required for new pages the read ahead and delayed write optimizations are also possible so what this means is basically so if you know that actually you are reading from one particular file instead of getting the portions that are in the read operation you get more thinking that maybe like I mean you can read ahead of time so and then delayed write is essentially like I mean so you delay the write with either the various cache consistency protocols and so that we can further optimize overall caching can for the local files the writes are deferred to the next single so this is again the delayed write so 32nd interval is when like the sink even happened it the way that in the Sun NFS both very well with the local context the files are always active to the local cache but in a remote case the synchronization like it does not guarantee the necessary synchronization to the cache so the NFS version 3 servers offers two strategies for updating the disk one is the write to and then the other one is the delayed commit I think like you already know about this when we had studied the cache coherency protocol how to maintain coherency in a cache whereas the write to is essentially again writing it both in the cache as well as in the main file in this case essentially like I mean for the altered pages are written into the disk as soon as they are received at the server so then the other one is the delayed commit whereas the pages are held in a cache until a commit signal arrives and then basically at that point the file system itself is written with the new beta so we we looked at from this client caching so again the client caches the results from the read write get attribute look up and then the reader operations the synchronization is not guaranteed when two or more clients are sharing this so that is something that we pay the penalty for then the validity itself is checked through a timestamp based check essentially like it reduces the inconsistency but it does not eliminate it so it is used for the validity condition condition or cache increase at the plan so formula is like T which is the parent time minus TC the time when the cache entry was last validated must be less than T which is the person is guaranteed so we do not want excessive time pass between these two events to do anything kind of thing and then essentially the TM client is the time and the block was last updated at the server and then basically TM TM server is essentially like then so actually TM client is the time in the block was last updated at the client and then the same thing is when it was a server TC is the time and the cache entry was last validated so so basically like I mean we need to make sure about this is the validity condition that is satisfied for the cache entries so in the previous one the the T perf is it is the freshness guarantee that can be customized so you can decide what that value should be and then based on that we can construct the the rules so the T is set between like three seconds to 30 seconds also it remains difficult to write distributed applications that share files with the so one other question that may come up is how do we maintain the how do we update or how does client update the server so for files essentially like I mean we can do the write back from the client cache to the server and then we can decide that into the last 30 seconds also like there are commands called flush on close which is essentially it takes the the memory needs and writes and then push it into the file system automatically for the directory is essentially like we just continuously write to a server so as an example we can say okay the client X and Y they have a file name called a that is cached and then the file name a occupies the block 1 2 and 3 so now the clients X and Y both can open a and then X writes to the blocks one and two and then client Y actually like now it writes to the block and block one and 30 seconds later what happens the client Y reads blocked it and 40 seconds later the client Y reads block one so again like I mean this is one scenario like I mean there you can find out how system will behave so the performance itself is another parameter or another concern that we talked about so the right operations only like I mean responsible of 5% of the server cost in the typical units and moments the lookup accounts for 50% operation because step-by-step part name resolution is necessitated by the naming and then the model semantics so the recent measurements show a higher performance of the NFS and then the last measurement was taken in 1992 so in summary NFS is an excellent example of a very simple but a robust high performance distributed service or a distributed file system so the access transparency essentially like I mean for the same Unix call is or the Unix call itself is same for both local and remote files so that is one of the things we talked about in the transfer so let us look at those the transparency in detail so the location transparency the naming of the file systems is controlled by the client mounting operations but the transparency can be ensured by the appropriate system part duration so even though like I mean the client actually controls the month operations and how to name the files the transparency can be controlled if you actually configure the system with the appropriate information or uniqueness in the more points the mobility transfer transparency essentially means that when the system is changed from one to the other how do we ensure the transfer transparency this is not achieved at all and relocating the files is not possible and only the file systems are possible but that requires an update the client populations because clients are the ones deciding everything about the this particular file system memory loss and then the scalability transparency essentially like I mean for again this one we can subdivide the file systems and allocate and we can allocate separate servers for each of the file systems so that way like I mean we can scale the but it also depends the performance itself is determined by the load on the forward holding the most heavily used replications is another one so so for replication since we do a limited only we limit this file system to read only file systems basically the replication transfer system so for writable files the Sun network information service of the NIS one covering method and that is used to replicate essential systems the hardware software operating system heterogeneity again the NFS has been implemented for almost every known operating system and hardware platform and that is supported by a variety of high-end systems all tolerance it's limited but effective so service is suspended if the server fails victory from failures is aided by a simple state and efficiency basically it can be implemented for use in situations that generate a very heavy load so the next case study will be the Andrews file system before we go into that also want to talk about a little bit on the the Sun NSS file system so the key take away is that you want to take away our number one is it's a stateless server and then the operations themselves are what is known as the item potent operations what I mean is here yeah and then the other take away is also the the client so so yeah so the item put and server operation is essentially like I mean when you repeat an operation it does not have any side effects so it also helps with the ways other things basically like the fault tolerance the scale before common consistency they are all addressed in the NSS system and then one thing to note is when particular system crashes it tends to slow the other the server to the other plants the plants that are there so this is kind of one of the drawbacks of the pink of it and then the client also like needs to cache the data for scalable performance not just the server alone needs to catch in fact when server caches sometimes it is not me and since we put a cache in the client side the data consistency is extremely hard because now we don't know like in which copy is the latest form because there is some other copy that is still sitting in the processor so that's all I have for today you will continue from this point next week then we will bring the next pass thank you very much