Okay, so let us continue from where we left off yesterday just to briefly revise that linear momentum idea for the differential analysis. What we had done was we had started with the integral linear momentum equation and then used the Leibniz rule and the divergence theorem to convert everything on integral on the control volume basis from which we obtained this final momentum equation which is essentially nothing but as we remarked linear momentum principle on a per unit volume basis and this was of course the vector form which was specifically written out for x direction and similarly for the y and z directions. Then what we also looked at is how to obtain a so called non-conservative form of the momentum equation starting from our conservative form and there is a little bit of math manipulation all that we did was we subtracted u multiplied by the continuity equation from the conservative form and we obtained this so called non-conservative form which if you remember if you simply multiply both sides by delta v, delta v being the volume of a fluid particle then we can interpret this nicely as f equal to ma applied to a fluid particle which is the Newton's second law of motion. So the point that one wanted to convey here was that these so called conservation form or conservative form and the non-conservative form are essentially identical you can obtain one from the other. In this form when you write it though the way it is written on the board right now namely the non-conservative form you can interpret this as a Newton's second law applied for a fluid particle. Again the volume element has been cancelled from both sides here so that we end up interpreting this as Newton's second law on a per unit volume basis. Then we introduced the ideas of surface forces and the body forces and a special shape of a fluid particle has been identified with all these stress components as positive and we explained what the notation and the sign convention was. So let us just quickly see that again. The first subscript on a stress component gives you the direction of the normal to the surface over which the stress is acting. So essentially if the first subscript here is x which means that the direction of the surface normal is in the x direction and the second subscript gives the direction of the stress component itself. So that is the double subscript notation and then we also came up with a sign convention how we are going to call something positive, how we are going to call something negative. One thing I did not mention yesterday about this positive and negative and that is that with this convention if you go back and see tensile type forces if you can think about come about as positive and compressive forces come about as negative. So that way it is physically also intuitive and it fits into our picture of what is happening. This is exactly like what we have in solid mechanics many of you I am sure are familiar with the stress analysis part of solid mechanics it is exactly the same. So now let us move on. So I am rewriting this again basically starting from this non-conservative form multiplying both sides by the volume element. What I have done here is for the x direction and y direction nothing different and here since the shape of the particle was chosen to be this triangular we are appropriately multiplying or appropriately calculating the volume element which is simply one half of the delta x times delta y. So after having multiplied by delta v on both sides what we have is again f equal to m a type representation for the fluid particle. So now what is to be done? This is a bit of algebra and I wanted you to do it so I have outlined what needs to be done. If you see the right hand side here we have capital F suffix x and capital F suffix y which are essentially the net x and y forces on the fluid particle. So let us go back to this picture and all that we need to do from here is we sum the forces in the x direction likewise we sum the forces in the y direction. So here it is pretty obvious that we have this sigma xx which is acting in the minus x direction then we have this tau yx which is also acting in the minus x direction anything else? There is the body force gx which is assumed to be acting in the positive x direction fine anything else? So now we need to resolve these two guys that sigma nn and tau nt need to be resolved in a direction that is in the x as well as in the y and those also need to be appropriately included in our summation of the x forces and summation of y forces. So that you can easily do the resolution of these into two components in terms of this theta and the geometrical parameters like delta x, delta y and delta x. Remember again these are stress components so if you want to find out the force you have to multiply by an area element so for example sigma xx then will multiply by delta y multiplied by 1 which is per unit depth correct and so on. So that is a bit of algebra which I am simply writing here needs to be done so sum the forces on the particle. Now what is going to be done is what is written out there that is you actually write out the sum of all x forces and plug them in the right hand side here in the left hand side sorry right hand side here for the x and y forces. What when you do that you will realize that all these force the terms will have some multiplying factors delta x times delta y or delta x times delta y squared or something of that sort okay I do not remember exactly what it is but some volume element will be multiplying on everything. Now what we want to do is the objective of what was happening here is to come up with a statement by which we can specify the state of stress in a moving fluid at a point okay. So to that end we are doing this we have marked all the forces we are going to employ the Newton second law of motion as is known to us and then for the stress at a point we essentially take that fluid particle and shrink it to 0. Mathematically speaking what we are going to do is we will take the limit as these dimensions delta x delta y and hence delta s all value tending to 0. If you carry out algebra what you will see is that the left hand side here okay which contains a volume element on the right hand side there will be also a volume element in the summation of the forces and when you take the limit you will see that the left hand side and the body force term which is going to be present on the right hand side actually will go to the 0 limit faster than the surface forces. So what will be left at the end of the limiting process is you will have only an equation actually couple of equations relating the sigma nn which was a normal force on that slanted surface in terms of sigma xx, sigma yy, tau xy and tau yx. Similarly there will be another equation which will be left out which will relate tau nt which is the shear force or shear stress I should say on the slant surface again as a function of these four stress components. So this is something that is worth doing as a algebra exercise with that limiting process and not all books actually have this outline. It is nicely outlined here although I think if I remember correctly their element is in this fashion, the reverse triangle if you want but in principle there is nothing different in what we are doing. So if you want you can look at it but it is very easy to do. I have hopefully outlined what needs to be done. All that you need to do is sum the forces and take the limit as delta x delta y and hence delta s tend to 0 and you will see that the left hand side which is the body force sorry which is the inertial force as we say and the body force which is embedded in the right hand side will actually go to 0 faster in the limiting process than the surface forces and you will be left out with two expressions one relating sigma nn to all these four stress components and second relating tau nt to all these stress components for a given theta obviously that theta will still be there which is that inclination angle of the inclined surface. Fine this is the final expression that you will get in terms of some mathematical form. How do you want to interpret it? The interpretation is what is written here and that is we wanted the state of stress at a point in the moving fluid which is given by that sigma nn and tau nt on an arbitrary plane. See that theta can be whatever this is exactly the way you probably have seen the Pascal's law of derivation. I think many of you immediately commented yesterday when that triangular element was shown that this is the way that Pascal's law is proved. So what you do there is that inclined surface for the Pascal's law fluid element is also at some arbitrary angle and that is what you argue that angle can be changed whichever way we want and in the limiting process what you show is that pressure is essentially the same whichever direction you look at. So in that sense it is the same argument that the state of stress at a point will be specified in terms of that sigma nn and tau nt which is a pair of normal stress and a shear stress acting on an arbitrary plane. We are talking about 2D so let me write it 2D but one can quickly generalize to 3D once we know what is happening. So whatever is in the bracket is for 3D that is an extension. In 2D flow is completely specified in terms of 4 that is for 2D, 9 for 3D stress components acting on 2 for 2D, 3 for 3D mutually orthogonal planes passing through that point. So which are these 4 stress components acting on 2 mutually orthogonal planes passing through that point? It is basically these 4 sigma xx, sigma yy, tau xy and tau y. And why do we say that those 2 mutually orthogonal planes pass through that point is the limiting process that we are talking about so that the idea that this entire fluid element shrinks to a point will bring both these orthogonal planes essentially at the same point that is the idea. As far as I remember this kind of argument is normally put forth in the stress analysis course in solid mechanics. How many of you have seen it perhaps in solid mechanics? It is exactly the same. There is no difference between what is done here for fluids and what is done for solids. So in case you have not seen it perhaps you can open a solid mechanics book also just for making sure that this is how it is done. So in 2D then we need to have 4 stress components acting on 2 mutually orthogonal planes passing through that point to specify the state of stress completely at any point. In 3D we have 9 stress components on 3 mutually perpendicular planes that are passing through the point. And usually if you see then we for a 3D situation we will represent all these 9 stress components using what is called as a stress tensor representation which is usually in this matrix form and normally you will see that the normal stresses are along the diagonal and off diagonal elements are essentially your shear stresses. And if you see along one particular row any row I have outlined just one. What you notice is that for all these stress components the first subscript is the same. So it essentially implies that stress components in a given row are stress components acting on a given plane because the first subscript is telling you the direction of the normal to the given plane. If you look at any particular column likewise the second subscript is common and the second subscript tells us the direction of the stress component itself. So if you look at any particular column it simply gives the stress components in a given direction. So the idea to introduce this is just for completeness. Many times you will not find this sort of an argument in introductory fluid mechanics textbook. For example the two that I have brought here the Potter's book and the Fox and McDonald. They do not really go through this formally here. In the second chapter for example in Fox and McDonald they simply write that a state of stress in a 3D flow is specified in terms of 9 stress components acting on 3 mutually perpendicular planes passing through that point. But where is that coming from is what I wanted to sort of convey to you that you do this formal analysis on a triangular element like this and thereby you bring about that statement. So there they will simply write a tensor here that this is the 9 stress components that are required etc. Same thing for that book but Gupta and Gupta have outlined this very nicely in my opinion. So I think it is worthwhile going through that. After this is just algebra and that is why I really want you to do it once if you have not done it before. Fine. So this is something that was slightly aside in the sense that as I said I wanted to point out the idea behind this state of stress at a point in a moving fluid. So now let us go back to our momentum equation and come up with our standard shape of the fluid element which is the rectangular delta x delta y type. And now that we know that the state of stress at a point is given in terms of those 4 stress components. What I will say is that this so called center point if you want will be considered as the reference point where I will say that the state of stress is given by all these 4 components since we are doing a 2D analysis. The body force in x and y direction are again shown here. Now the body forces of course are for the volume element of delta x times delta y. So the volume here is delta x times delta y as you can see. What I have shown here is only 1, 2, 3, 4 components. So I think I have on purpose shown 2 normal components and 2 shear components. The idea is that if I wrote all then it will become very cluttered the picture and what you can easily do is you can complete this picture yourself. So for example this normal stress here on the right hand side and this shear stress on the top. Similarly this normal stress and this shear stress you can complete. So how are they obtained anyway? I have the state of stress at point O in terms of sigma x x sigma y y tau x y and tau y x. So I simply do a Taylor expansion from O to delta x over 2 to the right, from O to delta x over 2 to the left, from O to delta y over 2 to the top and O to delta y over 2 to the bottom. So then accordingly when I go from this point on the upper side through a distance of plus delta y over 2 I need to have a plus sign here. When I go from O to delta y over 2 on the bottom side negative I have appropriately a minus sign here. And these are all again first order Taylor expansions which essentially are found to be sufficient to describe our fluid flow situations quite reasonably. I hope that you can complete the remaining 4 which is pretty straight forward. Any question on this? Fine. Now what is the use of this? Before that there is one more relation which is very useful and that gives you the characteristic of these shear stresses. So with respect to this figure here if you take moments of all forces about this center point O, summation of all moment. Clearly what is going to happen all normal forces and the body force will not contribute to the moment because they are all passing through the point O. The only contributing factors will be from the shear stress component. And if you can see the shear stress here and the shear stress here will form a couple which will be in the anticlockwise direction. Similarly the shear stress on the top surface and the one on the bottom surface will form a clockwise couple. So you can think about a net anticlockwise couple which you can find very easily and that is if you do that algebra again you will see that the net counter clockwise couple about the point O will simply come in the form of this tau xy minus tau xyx times the volume element delta x delta y. So this is a bit of algebra which you can simply do by forming the moments of these shear stresses which is fine. But what is that equal to? The net moment is equal to just by Newton's second law of motion we have net force equal to m times the acceleration. We have this as the moment of inertia about z axis because we are doing a 2D element times an angular acceleration. So this is the equivalent form let us say for moments of the Newton's second law. It turns out from calculus that the moment of inertia for a rectangular element such as this is given by an expression like this. So I have not done anything here I have just picked a mathematics book a calculus book essentially and picked the expression for the moment of inertia for a rectangular element and if you plug this fellow in here and rearrange you will obtain an expression for the angular acceleration. Now the idea or the argument here is that if we keep shrinking that particle meaning that if we take the limit as delta x and delta y tend to 0 what is going to happen? The denominator will actually go to 0 which is meaningless unless from mathematical point of view if you have to have a finite limit for this limiting process what has to be done? Continuum should be satisfied. Continuum is indeed satisfied but the idea is that if I take if I look at this expression and take the limit as delta x and delta y tend to 0 meaning that we are shrinking the particle to a really small size. We are forced to come up with the conclusion that this alpha suffix z which is the angular acceleration of the particle about the z axis tends to go to infinity for no reason. There is no absolutely no reason to for us to expect or assume that just because the mathematical limiting process is suggesting that the alpha z which is the angular acceleration shoots up to infinity for no specific reason it is physically unacceptable situation. So the only way that physically unacceptable situation will occur is if alpha z is finite. So how do you obtain a finite limit when you have a denominator 0 from calculus side. So the numerator also needs to go to 0 in the limiting case so that we actually get a 0 over 0 situation which from the mathematical point of view usually has a finite limit. So it is a nice combination of a physical interpretation and the calculus idea which helps us out here and therefore what we have to conclude here that to keep alpha z finite the only possibility to expect here is to have the numerator also 0 so that in the limiting process 0 over 0 has some finite limit and therefore the biggest conclusion of this business is that tau x y turns out to be equal to tau y x which is actually very very important simplification. And this is believe me this is actually not coming just by that limiting process there is a physics involved in this as well and the physics is that we cannot for no reason expect that alpha z tending to infinity. There is no special mention of any situation which will make that alpha z the angular acceleration go to infinity to avoid that we must conclude that tau x y must be equal to tau y x and in general you can repeat this exercise in all planes I have done it in the x y plane you can draw the picture in the y z and the x z planes and come up with essentially the same argument no difference. So therefore to generalize it I will simply write that tau j i or tau y j equal to tau j i where i and j can independently take x and y so tau x y equal to tau y x similarly tau y z equal to tau z y and so on. So if you go back to our stress tensor then you see the off diagonal elements tau x y and tau y x tau x z and tau z x tau y z and tau z y so we just proved here that these occur in pairs that is these are equal so therefore how many independent entries then exist in this stress tensor 6. So we are not dealing with 9 independent entries but we are actually dealing with only 6. So this is a useful information to know. So this was again a little bit of aside from the main thing but nonetheless extremely useful result. Now the idea for this picture was that you show all sorts of stresses which are essentially the surface forces show the body forces some all those in the x and y directions and plug them in the Newton's second law of motion which was written out here. So this is precisely what I have done now that is why I am writing going back to the Newton's second law of motion for the fluid particle and immediately I am going to generalize because this is only an algebra. This is what we wanted to plug in the net x force on the particle for which here is the picture available. Stress components are given you have to multiply those by the appropriate area elements to obtain the forces some all forces in the x direction some all forces in the y direction and plug those in here and here. And immediately to generalize what you will see is that the left hand side from rho times substantial derivative of u to up to here there is nothing new here what is that that was already discussed and completed earlier which is our left hand side here or the left hand side here all now presently we are talking about is the forces which is the right hand side here here here and that is what this is. So the right hand side then which is essentially the net x force on the fluid particle net y force on the fluid particle and likewise the net z force in the fluid particle if you work out the algebra will come about as partial derivative with respect to x of sigma xx plus partial derivative with respect to y of tau yx plus partial derivative with respect to z of tau zx plus rho times that intensity which is per unit mass value of the body force in the x direction and so on. So this is something that usually is worked out I mean most of the books will have this discussion that that you will find sometimes some books do not talk about this moments business sometimes they do sometimes they do not I do not remember whether these people are talking about it or not. Nonetheless I hope that the argument was understood here and I think as far as I remember it is the same argument that solid mechanics use they also have the same relation for the shear stresses that they occur in pairs it is exactly the same manner in which they bring about there is no difference between the solid mechanics argument and the fluid mechanics discussion that we are having here okay. So now we have what we call differential momentum equations which are essentially nothing but again Newton's second law of motion written for a particle if you look at the left hand side written in terms of the substantial derivative and then the net force acting on the right hand side in whatever direction that we are looking at. Alternatively you can utilize the so called conservative form on the left hand side which was brought about through the use of essentially that Euler's approach Eulerian approach which we brought out by converting the integral form into differential form. So the substantial derivative and this middle term are essentially equivalent to each other which we have shown and the right hand side simply here tells me the net x force on the fluid particle but in this boxed set of equations everything here is on a per unit volume basis that is something that you must keep in mind okay. So when you simplify these two equations on the top what you will find out that the volume element actually drops out and what remains is what has been written out here and therefore the boxed equations are what are called as differential momentum equations sometimes they are called Cauchy's equations they are all on a per unit volume basis and this terminology of Cauchy's equations actually comes directly from solid mechanics. So if you see this set of equations is more or less the same for solid mechanics as well. The only difference between solid mechanics and fluid mechanics comes is when we want to now relate these stresses to rates of strain in our case they will utilize the so-called Hooke's law which will relate stresses to strains rather than rates of strain. In fact that is how I want to bring about the next part in this discussion but so far barring the algebra which I am assuming that you will sometime do is the idea reasonably clear as to how we are progressing. Some of these issues like the moments part and the state of stress at a point are I think very very important to have included in the discussion because unless those are clarified it does not make sense to really directly write the stress tensor in terms of these nine components. So students usually ask unless you discuss this first the state of stress that why is it that these nine in a 3D situation are going to completely specify my state of stress and it is very useful from that point of view to do this discussion and show that it is really indeed coming in this point. So now what is left to be done to bring about our final forms that we normally are used to seeing is as I said these stress components that you can see here need to be related to the rates of strain and we already know the expression that we are going to use assuming the Newtonian fluid what we are going to say is that the stress component is going to be linearly proportional to the rate of strain. However the very first lecture what we talked about was a simple one dimensional flow that parallel shear flow we looked at and we had seen that their tau then was written as u times d u d y that was a one dimensional situation. So now it is going to be generalized to a two or three dimensional situation and to do that we have to talk about a little bit more on what is called as the constitutive relations for Newtonian fluid which are nothing but the relations between stress components and the strain rates in a generalized form. So this is also called as the generalized Newton's law of viscosity whatever discussion we are going to do. Now here the formal let us say derivation or in some sense the development it is not really I would not say it is a derivation but the development of this relations is very, very tedious and this was done by Stokes apparently in 1845. Normally you will see that this is normally not there in any of the elementary books like what we are talking about here. Normally you will find this in a one level higher book for example that Kundu and Cohen which I wrote on the board yesterday has this discussion but it is from a completely mathematical point which unless you are very comfortable with knowing the Cartesian tensors and their relations and such it is very, very difficult to understand. So in my opinion if you are ready to sit through a very, very long and tedious discussion the best physical let us say work out process is in a book by S, it is a very old book some of you will know it, SWE on it is I think called the Foundations. It is a very old book, how many of you have heard it? Okay good. So it is really outlined completely there like the treatment is there but you have to resort to it, there is no other option but it is extremely unreadable in my opinion. Shames all I have seen it of course but not to a great extent, just please comment whether it is a completely worked out derivation as how it is in Yuan or I think James's book is called Mechanics of Fluids and of course as he is mentioning this is Muralir and Viswas you are right. The problem that I have with Muralir and Viswas is that there are too many errors in the book and in the sense that there are I think too many typographical errors. So it is very, very irritating if you are working out something and if you see that something else is coming in the book and you have no clue whether you are going wrong or whether the book has been incorrectly printed and that is the reason I did not want to point out this book to you because there are too many typos in the book. However if you have read it and if you think that it is fine you can always look at it. Fine. But I mean I have not really spent too much time with it so there is no problem in looking at it. But this one I absolutely know for sure that the entire algebra is worked out as one would want it and I think from this book itself Professor Prabhu had put together his heat transfer slides wherein he had explained this if I am remembering correctly. James's book unfortunately is not that easily available unless it is in the library. But it does not matter correct. The reason is because James is basically a solid mechanism. Yeah I have seen this one and it is the last edition that I saw was an international edition I think it was a 1988 international edition with very thick volume like this. I have edition I mean our library has an edition which is somewhere 90s which is not a very big book it suggests only this size. But I am actually in fact I have looked at brochures of this Magra Hill but it seems there are recent editions has come up sometime in 2008 or 2007. I do not remember exactly but I am not able to get the book in India. But it does not matter because this is this business has been there for ages so even if you look at an older edition it will be there. Fine. So these three you can look at definitely I have myself gone through this completely. So I am confident about that part. If someone is saying that a physical explanation is provided there perhaps you should look at it. And James is something that I have barely seen but I know that it exists there. That is correct. There are many other advanced texts which have this business but it is all completely mathematical and it is very difficult to make any sense of it as to what is going on unless your background in the tensor calculus is very good. So that is fine. I mean you can spend time on tensor calculus background and then go and read it but it becomes a little bit of work. So what I am going to do is rather superficial discussion in the sense that I am just going to point out to you what are the bases on which this development is done. And it is simply that there are three assumptions that have gone into it which is in really speaking there are only two assumptions which is the first one is stress is proportional to directly proportional to the rates of strain which is simply our standard Newton's law viscosity. Now it is in the generalized form that is all. The main assumption is that the fluid will be considered as isotropic which means that the fluid will have a direction independent behavior. Whichever direction you look at the stress strain relation remains the same that is the main assumption. And the third one is not really an assumption but it is a common sense statement that in absence of strain rate whatever stress expression that you have should automatically reduce to describe the static fluid situation correctly. So that is the common sense statement in that sense. And I will directly give you then the final results here which have come about through this. For the shear stresses we have already seen that the shear stresses occur in pairs. And for example the tau xy equal to tau yx is simply the dynamic viscosity times the strain rate total strain rate in the xy plane which we derived yesterday from the kinematics consideration. And likewise for the remaining two. So this I will say is still a fairly intuitive statement to understand that tau equal to mu times the strain rate is just that now we are talking about a two dimensional situation. So accordingly that strain rate earlier in that pure one dimensional shear flow we only had du dy if you remember. Now that there is that dv dx component also added because of the multi dimensionality of the flow and so on for the remaining two. So this is as far as the shear stress relations are concerned. For the normal stress there is a little more involved business. Basically what I want to point out is that the normal stress that is going to be acting. Let me go back to that picture here for example this one or this one or this one that will have two contributions in general. One is what we will call a pressure contribution and there is a viscous contribution to the normal stress as well. So the total normal stress for example sigma xx is written as minus p y minus again it is the compressive nature of pressure which is brought about through our sign convention that we talked about plus a sigma xx which is contributed from the viscous side. So this viscous side is something that needs to be talked about and here what I am doing for rather simple discussion is that I am just pointing out an analogy between a generalized Hooke's law in solid mechanics and I will simply say that we are going to replace from the Hooke's law statement the strains by strain rates for our fluid mechanics situation. So if you look at a generalized Hooke's law from any solid mechanics text the normal stress there let us say the sigma xx again for an elastic solid is written as two times the shear modulus multiplied by the strain in the x direction plus some other factor where that Poisson's ratio also comes in whole thing multiplied by a summation of all normal strains. So now if you want to use this analogy and say that we want to write directly then the viscous contribution in a fluid flow situation I will simply write by analogy that sigma xx then is two times mu times e dot xx where that first coefficient of viscosity or the dynamic viscosity comes in and if you look at this all business I am combining in some sort of a second coefficient of viscosity as it is popularly called and instead of the normal strains I will simply have the summation of all normal strain rates. So this is as let us say pedestrian way of putting it across as it gets without really getting into too much detail of the Stokes's development and if you recall from our kinematics discussion the summation of the three linear strain rates was essentially equal to the volumetric strain rate which was given by divergence of the velocity. So that this e dot xx plus e dot yy plus e dot dz is simply replaced as del dot v and that is what the expression for the normal stress is let us say here I have written it for the x direction for the viscous part. Similarly if I want to write it for y direction it will be simply this two mu times e dot will be yy here this all remains exactly the same because it is a total addition anyway same thing for zz sigma zz viscous will come out as two times mu times e dot zz same thing here okay. So now let us see what happens then we said that normal stress has a pressure contribution and the viscous contribution viscous contribution has been simply argued from the basis of an analogy with generalized Hooke's law in solid mechanics pressure as it is we know minus p. So we put together sigma xx minus p plus all this from here which is again simply written out in Cartesian form just for clarity in some sense. Similarly for yy and zz and this first set which I am calling as one and the second set which is called as two is what together called the constitutive relations in fluid mechanics all that they are doing is we are relating the stress components to the strain rates through viscosity and something else also has creptin now which is this second coefficient of viscosity. So now let us see what we can still do with this relations one and two as I said called the generalized Newton's law of viscosity or constitutive relations for Newtonian fluid. Now let us say we look at this again second set and if you add all these guys if you add all three relations what we have is sigma xx plus sigma yy plus sigma zz on the left hand side there will be minus p minus p minus p so sorry that will go to minus 3p and these two guys will nicely add together to get into all strain rates sum together multiplied by whole thing multiplied by 2 mu plus 3 lambda that is very straight forward algebraic addition nothing different. So customarily what is done in case of fluid mechanics is we define the summation of these three normal stresses as minus 3 times a so called mechanical pressure. So if you see the way the mechanical pressure is defined it is simply minus the average of the three normal stresses because if you take sigma xx plus sigma yy plus sigma zz divide the entire thing by 3 and put a minus sign to it you will get this p bar let us say which is what is called as a mechanical pressure. So fine let us go with it and see what happens if you replace this summation then by minus 3p and then simplify by dividing through that minus 3 then you will obtain a relation of this sort that is minus p bar which is the mechanical pressure equal to p which is right here minus 3 has been divided out minus if you divide the remaining part by 3 you can rearrange it in this fashion. So this is where some discussion perhaps can be done and here is where what I want to point out there is this so called p bar which is simply the by definition average of the three normal stresses whereas this here is our p which is what we normally call a thermodynamic pressure. So it turns out that there seems to be a difference when we come to a fluid that is flowing that there is a difference between the so called thermodynamic pressure and a so called mechanical pressure which is simply the average of the three normal stresses and the difference between these two is given in terms of whatever is you whatever you see on the right hand side here. My question is what is that you understand by thermodynamic pressure it is also called as static pressure in fluid mechanics terminology so what is your understanding of static pressure how would you interpret static or thermodynamic pressure this is an important concept so static pressure is recorded by a device which is static with respect to flow. Exactly, absolutely right. Where should you do static and steady state of the fluid? It is the same thing actually what he is talking about what he said is absolutely right that is the exact definition of static pressure so in case of a moving fluid the way one wants to interpret static fluid static pressure is let us say you take a probe and you start moving with the flow so that there is no relative motion between the probe and the fluid whatever the pressure that the probe will measure is what is called as the static pressure or essentially it is called as a thermodynamic pressure the reason why it is called thermodynamic pressure is because there is a systems approach in built in here we are essentially making the flow stationary with respect to your probe and as if you are dealing with a closed system at that point so that is what the idea of a thermodynamic pressure is which is absolutely right and so it turns out that the thermodynamic pressure which what we are used to knowing or the static pressure seems to be different in general from this so called mechanical pressure if we simply define it as the average of the three normal component. And as I said the average sorry the difference comes in the form of this two thirds mu plus alpha times these total addition of these strain rates. So here is the biggest modeling let us say input that came from Stokes and Stokes simply assumed that let this two thirds mu plus lambda be equal to 0. This is actually a postulate there is absolutely no theoretical basis for it as far as my understanding goes and that is why it is called as Stokes's postulate. Now let me quickly ask you before we get on with this what about if I have an incompressible flow do I need to bother with this postulate at all no why because automatically this is equal to 0 for an incompressible flow del dot v so in that case the mechanical pressure turns out to be equal to the thermodynamic pressure. However if we are now if we are dealing with a non incompressible flow or compressible flow so to say we actually formally should take into account the difference between the thermodynamic pressure and the mechanical pressure. However to make life simple in some sense Stokes simply postulated that let this two thirds mu plus lambda be equal to 0 and accordingly then we generalize that this p bar is simply equal to p in all situations with a auxiliary relation that lambda that second coefficient of viscosity equal to minus two thirds of mu. So this is what is normally called as the Stokes's postulate again there is absolutely no theoretical basis for it in some situations you cannot really neglect this contribution. Any idea what that could be that situation clearly we are talking about compressible flow because incompressible as we said that entire del dot v will become 0 and we are automatically getting p bar equal to p prime. But incompressible this how many of you are familiar with compressible flow I think some of you are saying that you do gas dynamics teaching etc. High Mach number is correct but additionally not just high Mach number that is not really a sufficient condition it is necessary condition for this to be included but there is a not just high Mach we need to have some special situations occurring what happens typically in high Mach number situation. In case you are dealing with a situation where there are shocks in the flow within the shock region see we treat the shock as usually a discontinuity but shock is really not a discontinuity the shock shock spread as it is called is usually over a distance of about 5 to 7 mean free parts. So if you want to really zoom into the shock you will see that the shock region is about 5 to 7 mean free parts. So within that shock region you actually cannot really neglect or you cannot employ this Stokes's postulate but however in general how many situations we actually deal with where you are getting into the shock and seeing what is happening. So on the whole what is done is that without really bothering too much we simply utilize the Stokes's postulate and it turns out that in most situations except like the one that we just talked about namely a shock structure type situation this works perfectly fine. So please again I will repeat my statement from yesterday that people blindly utilize these differential equations as some holy grail in some sense. I do not know those words or not but there is nothing holy about those. They are just about a model that someone has proposed and it seems to work more or less okay in most situations. So there is no reason to say that differential equations form the basis and you know that is something that is absolutely true and such and so on. There is nothing true in general anyway everything is a model and this model seems to be doing its job quite reasonably. So please keep that in mind and I think it is useful to point this out to students all the time because students will otherwise go out thinking that oh this is some absolute godsend thing that you know you just take it. It is not like that everything is a model. Is f equal to ma anything else? Newton's second law of motion which we have been using left right and center from childhood. Is there any theoretical basis for f equal to ma? Zero there is none. It is a phenomenological law based on observation and you should treat it that way that it simply seems to work and that is about it. So when someone says that Newton's second law is some again absolute truth nothing like that you know it is just a model that seems to be working and we simply keep using that model later and it seems to keep doing the job for us that is about it. So please keep this in mind that Stokes's postulate is just a modeling exercise and it seems to work reasonably well for most fluid situations where it does not work is if you have to actually deal with a shock structure type situation in a compressible flow and you cannot really utilize any of this in a shock structure situation. Any of this means what? Any of this continuum business that we are talking about doesn't work. If you want to actually study the shock structure in a gas where there is high Mach number flow and a shock is getting generated you actually have to give up on this continuum analysis and you have to do something else which is the molecular analysis if you are really keen on that. However in most engineering applications such detail is not required ever and so we can live with this. So that's what my take on this. Alright fine so having accepted then this model we simply substitute back in the Cauchy's equations which were right here. So now I have a relation for sigma xx tau yx tau zx etc from these sets 1 and 2.  I will simply say that substitute relations in 1 and 2 or substitute relations 1 and 2 in the Cauchy's equations and simply go ahead and do the algebra for the x direction then assuming a constant viscosity you can simplify that into something like this and immediately looking at this expression you can generalize using the vector form where whatever has been written out in the box is the so called Navier-Stokes equation or equations if you want for a viscous but with a constant viscosity compressive flow. So this algebra is again usually it's okay to do it once so that we absolutely are sure that this is how it comes about. I hope you understand what is to be done. Take this set and this set and plug it in these equations and go ahead and simplify and you should obtain something like this. Fine. So if you want to write it in the vector form then it shows up as what is shown in the box which is something that looks perhaps familiar except that since we are talking about a compressible business here this additional mu over 3 times the gradient of the divergence is an additional term that shows up because of the compressibility. So if you want to look at a simplified model then what is outlined here we will say that let us deal with a either a constant density or an incompressible flow. The only thing that you can essentially throw out is this del dot v equal to 0 because of incompressibility and then what is left out is something written out here and this is the most common form of the Navier-Stokes equation that mechanical engineers will end up using. If you are dealing with aerospace applications with truly high speed applications where compressibility is really, really present then you must go to the very first one. And that too there is very high chance that the viscosity may not be a constant. Viscosity for very high temperature gas applications becomes a function of temperature which means that this form either is not good which means that you actually have to go back and use this in the absolute basic form along with these relations here in their form so that some sort of a temperature dependence on viscosity etc can be incorporated right at the beginning and accordingly then you can work out the solution. But for our purpose the standard undergraduate class it is okay to simplify this with a constant viscosity at least to bring about the compressible form first and then for the incompressible or a constant density flow you simply say that this del dot v is going to be thrown out and what is left out is the most common form that you will see in mechanical engineering. So again this is nothing but a F equal to MA type situation as you can see if you multiply the left most part with volume element of the fluid delta v it becomes essentially m times acceleration. On the right hand side then what we have is absolute right hand side here all the forces the net forces acting on the net force acting on the fluid particle on a per unit volume basis again this equation is essentially on a per unit volume basis so you multiply that by the volume element and you will get the forces in their standard form fine any question on this since I am writing here this is a very small homework exercise for you if you want to do it. I wrote here constant density or incompressible are they the same or are they different if I say that a constant density flow or if I say an incompressible flow you say it is the same okay I will make a statement and you think about it and see if you agree with it or disagree with it and not now take your time whenever you want to do it. I will say that if I am dealing with a constant density flow it necessarily is an incompressible flow but if I am dealing with an incompressible flow it does not have to be a constant density flow this is my statement and you can note it down and think about it no it does not have to be even a natural convection situation I will make a general statement here that if it is a constant density flow it will necessarily be an incompressible flow whereas if I am dealing with an incompressible flow without resorting to any natural convection or anything it does not necessarily have to be a constant no no it has nothing to do with it. Is it about density variations yes it has to do with density variations absolutely but you make sure that you understand what I mean by this so my point is if I have a constant density flow I will necessarily have an incompressible flow which means that that del dot v here is going to be 0 okay on the other hand incompressibility condition itself from kinematics is del dot v equal to 0 so in either case I will be able to get rid of this del dot v and thereby simplify it to a situation like this. Let us not discuss this further but please those who want to really think about it note it down and let me know even by the time the wind works up from if you agree with me okay let us move on and look at another simplified form which is what we will call an inviscid flow so quite simply inviscid flow is where we will simply neglect the presence of viscosity and the only term that takes into account that is this mu times del squared v so if you get rid of that what is left out is what is popularly called as the Euler equation which is written out in the box here. Note here that the density need not be a constant in this equation it can be a compressible inviscid flow as well the way it is written okay now quick question see usually people will students will ask this is this just a absolute simplification in the sense that I want to somehow get rid of one term which is this mu times del squared v here and therefore I am saying that let the situation be inviscid meaning that mu itself we are putting equal to 0 and thereby getting rid of it is that how it is or is there any justification for treating a flow to be inviscid how do you yeah I think the flow can be inviscid in sense that it is not necessary mu is equal to 0 the velocity gains can be there especially when we are dealing with flows away from the boundary correct so that is precisely what he was pointing out here that if you are away from boundary you can normally neglect the action of viscosity but is it so in a particular situation more so second operator of velocity is 0 for irrotational flows oh no I am not talking about irrotational yet let us say that without getting into the irrotationality so far I agree with you though whatever you have pointed out for irrotational flow is absolutely right but without resorting to irrotationality someone already said from here and which is what I think the high Reynolds number so the necessary condition is that the flow has to be a higher Reynolds number situation in which case you can argue that the viscous effects can be neglected and then additionally you have to be away from walls fine so if that is the case then you can use this inviscid flow situation to a good extent and the equation that is written out here which is the governing equation for inviscid flow is what we will call the Euler equation irrotationality comes usually as a next step along with the inviscid nature of the flow you will normally see that irrotational and inviscid go hand in hand and it makes sense to me that is fine.


Today marks the five-year anniversary of the Drum History podcast. It has gone by fast and been one of the best experiences of my entire life. I mean, it has been so incredible to get to meet so many of you guys and do these shows pretty much every week. Here and now, I'll miss one, but truly it's just been an amazing experience.  But before I do that, I want to mention something that I want to do to commemorate the five-year anniversary. That would involve you guys. So what I would love to do, and I've had a few people do this over the years and send me clips. But what I want to do is have you guys listening to the show, send me a video. Doesn't matter how good the quality or the audio or anything like that, but send me a video of you playing the intro music to the podcast, which I'll play right now just so you can hear it. Okay, you guys have heard it a lot because of this. By the way, it's not me playing that. It was like, you know, from a stock music website, which I wish it was me playing it, but it sounds awesome. So anyway, what I want to do is you guys send me a version of you playing that. Like I said, quality doesn't matter. Audio doesn't matter. But it'd be cool if it sounded really good, if it looked really good, if you had a really creative way of doing it and a certain cool creative place, something a little bit different that'll go further. I mean, I'm going to include all of them. I think in this, what I'm about to talk about, I want to put these into a video where I don't know how long it'll be. We'll see, but I plan to include all of them. What you'll do is send me a video, you playing the intro, email it to me at the email address will be drummingwithbart1 at gmail.com. That's drummingwithbart, B-A-R-T-1 at gmail.com. That's like a different email I used to use. I just want to keep it clean and separate from my normal podcast email so I don't get things mixed up. So email me there, clip of you playing. I will then put together a huge montage and put it on YouTube, probably within the next, I'd say 30 days or so. But let's just give it a timeline. So today, when this is released, it's going to be October 24th, 2023. You will have until November 7th, 2023 to send me a clip. So November 7th, 2023. After that, I'm going to cut it off and I'm going to start editing it. But what I want to do is make a huge montage. And like I said, if you do something really, really cool, that's even better and I'll put it earlier in the video.  So anyway, do that. You have until November 7th, 2023. I'll put all these clips together of kind of the best drum history podcast intro performances and I'll put it up on YouTube and maybe my favorite two or three or four or five of them, I'll send you a sticker or something like that. But and if you're from like somewhere outside of the US, which you know, a lot of you are, tell me what country you're from. Put your name and all that stuff. So anyway, all that being said, send me your clips. It'll be awesome. So just a little bit about this process, like I said, it has been amazing to do this podcast. I've met so many great people who are truly friends. It is tons of work. I don't want to under represent how much work a podcast is that gets to a certain point where people really listen and you want to keep the quality up.  But then after that, it becomes really more of like, okay, you got to make this work and you got to keep it going, which having advertisers and making some money when you do it along the way to help supplement the time you put into it does make it possible. So if you hear advertising on the show, that's seriously what is allowing me to keep going five years in. But so really even on that note, the people who have advertised on the show, which I don't want to name names because there's been a ton of them, but it's been amazing and it's really cool to work with people and have them support me and then get to know them and then see them at drum shows and stuff. It's awesome. So just a really cool experience. If anyone out there is thinking about starting their own podcast or their own YouTube channel, I would say just do it. It is like I said, it's really, really fun and then it becomes a lot of work, but it still maintains being fun because you get to do all this stuff. But you know, there's Friday nights and Saturdays where you're still working on stuff and Sunday night where you're pulling your hair out trying to get it ready and get finished. But again, best experience of my life outside of kids and getting married and all that stuff, but really kind of my cool drum thing that I've done in my life. So I don't think I talk about it much on the podcast because sometimes people just have found me on YouTube, which the kind of numbers side of things have been really cool because it's grown a lot. So Instagram is now at since I started, I mean everything was at zero, but now Instagram is at 90,000 followers, 90.4 or something. Facebook's at about 17,000 followers. YouTube has been a big focus recently and that's at about 10,500 subscribers at the time of recording this. You get addicted to kind of growing the numbers and checking them and really making things go up like about 25,000 downloads of the audio only podcast are streamed per month on like Spotify and Apple, excluding YouTube and all that stuff. So it's just really cool to strike a chord with the community and have you guys like it. And the answering of emails and communication and stuff has truly as I've had small kids and different jobs and stuff, which has been a recent problem. I'll say I've kind of gotten bad about answering people's emails, which I feel terrible about, but I started a different job recently, which scheduling has gotten tough because I used to do them at like two in the afternoon whenever and it would work out, but that's just gotten different. So I guess kind of a thing to talk about now would be what's up next for the podcast. I have no intention of it ending anytime soon or even really changing the layout or format or anything. The gear episodes like the Lars episode and Neil Peart and John Denzmore and there's a bunch of them have always done really, really well. John Bonham is still the number one gear episode or any episode really on YouTube. So I'm going to do more of them very soon. There will be a Tony Williams, like mega episode with Paul Wells that will be coming out soon in the works beyond that are your normal history episodes, but I'm also going to do working on Alex Van Halen, which will be cool Travis Barker gear episode, which will be really neat, but these things all take time. Everything takes time and scheduling is hard. So just hang in there. Some weeks there may be an old episode released instead, but I actually think that's kind of cool because there's a lot of people five years in, I'll say one of the benefits of being around for so long is that like when you have 220 episodes plus, you know, whatever we're at now, I can go back and release like episode 17 and a lot of people haven't heard it. And if you have heard it, the cool thing about the show is that maybe that's something where you could use a refresher on whatever episode 16, 17, 18 and lower are because like I look back at these 70s and 80s and 90s in episode count. Now you I don't forget them, but I just need a little refresher on like, oh, that was an awesome episode or something like that. So if I'm kind of forgetting which was which then you guys may as well. So it's cool to have that ability where my wife is pregnant right now, I will say so our third and final kid will be arriving in January three boys and that'll be it. That'll be the last after that. That's no more, but so it's just nuts right now. But anyway, the podcast will continue. Everything will keep going. I'm hoping to hit 100,000 Instagram followers in the next, you know, a couple months. That'll be really cool. Subscribing on YouTube is huge. If you're if you're watching this, it's kind of a very common thing that I'm guilty of too. But if you're on YouTube, it would be awesome if you subscribed as well or wherever you listen, just follow and subscribe. That actually does really help. If you're a business that wants to reach drummers and my show is a good way to do it. So I'll plug that a little bit now. There's merch. That's also cool to support. You can get like here's a hat. You can get hats and stuff. T-shirts, which I wear my drum history shirt pretty much all the time, which is really cool. So anyway, all that being said, I just really appreciate you guys for supporting me for the last five years, which is pretty crazy. It's a long time, like I said, but it's gone by fast. And here's to another five or 10 years. There's no shortage of episodes. I have so many episode suggestions, which I love getting from you guys. And it's always cool. Sometimes I have to say like, that's a really good idea, but it, you know, how do you get an hour out of that? I've kind of learned to really like step up the like, I feel like once you hit a certain point and threshold you guys who are listening and watching expect a certain level of like quality, which I hope I deliver on and I've had a few or some people will say this wasn't great or they're all good, but there's been a few or say this is kind of a stretch and I get it. I think I understand what people are looking for more. So anyway, more of the high quality stuff on the way. So keep sending me your ideas. But okay, so as we wrap up remember, send me a clip of you playing the drum history podcast intro, the music you hear at the beginning. It's pretty short. It can be you don't need to worry about how great you sound playing. It's like the quality of your performance. The audio should be decent. I mean, you can use your cell phone or whatever and then the video as good as you can get.  That'd be awesome. Like if you play with an orchestra playing an awesome, you know, venue or something, whatever, it can be it can be anything, but it'd be cool to get some some kind of neat unique ones there. So email those, the video and the audio synced send it to me together. I don't really want to sync a bunch of video and audio to send like the finished thing. If you color it, whatever if it's cell phone, that's fine drumming with Bart one at gmail.com. That email will keep things separate and it will be all clean and I'll get everything. So that's it for this week. I have a cool one coming up next week. That's a little bit different that I think you guys like, but I just wanted to kind of do a state of the union episode for five years and and thank, you know, everyone who's been involved. We've lost a decent amount of people who I've interviewed over the years. There's a lot of people who are no longer with us. Barry James was recent. Dom Fomularo was recent. Jeremy Berman, that was a crazy one because he was on and it was kind of one of the last times people saw and heard him before he passed away. So it's it's pretty incredible, but I appreciate you guys listening and supporting this show. If you just found me or if you've listened to every single episode since day one, which I know a lot of you guys have. So thank you for listening. It means a lot to me and so honored to be, you know, something that you guys look forward to listening each week and watching on YouTube and, you know, share it with a friend and tell your drummer friends that they should check out drum history and it really helps the show. So thank you guys and I will see you next week.


What's up everybody? Jason here for jazzy's case breaks calm 2021 penny. Oh, sorry upper deck ultimate collection hockey just sold out This is a two box break Three man and seems each number five guys And again guys 10 totals buzzer because three man and teams and each album or one combo team ducks yields And you get one rookie patch autograph one relic or one rookie autograph one relic and an additional Autograph or premium reveal the card and one non-hit card, which is a base parallel introductions insert This is from a fresh inner so numbers one through four with the first inner five through eight will be the second inner There's a dice roller as a customer name. So we tripled up your names There's the teams with the combo team. So here we go Rolex during the three six times one two three four five six Six times Steve Birch down to Steve Birch six times one two three four five Six times Blues down to the Hurricanes Hi, so Steve you have the blues my tower the black Hawks Kevin with the Knights burning of the nuts Steve with the ducks yields combo Bernie with the flames and Canadians Kevin with the blue jackets We have Steve with the senators Mike tower with the capitals Steve with the sabers or sorry stars Bernie with the sabers Steve birch of the Panthers and Preds Joe with the lightning Kevin with the Bruins Brittany you have the Devils Joe and Risa with my King Steve birch last one will do wild Brittany you have the Islander Steve birch of the Maple Leafs Brittany with the Rangers Steve with the Red Wings Joe with the avalanche Mike tower with the Flyers Brittany with the Oilers and Sharks Steve with the Penguins Jets and Hurricanes So I'll leave the trade window open. Maybe anybody wants to make any trades Actually, I'll tell Brittany. She's actually here with Steve locks to see if she wants to make a trade. I know they love the wild Well, I don't know if you're listening Steve, but Brittany is actually here. She's wondering if you'd want to trade ranges for wild or potentially any other teams that she may have So Brittany Let's see. Let's go by alphabetical order. So you guys can see it better Brittany has these teams Sabres Flames Oilers Canadians Devils Islanders Rangers Sharks Nucks And then obviously Steve you have these teams plus the Minnesota Wild So if you're listening Steve, let me know I'll give it some time There's Brittany. So let me know Steve Our wild have Capriceau Rangers would have Le Farnier No, thanks. Okay. Well, we tried stick to what you got then we tried. All right. Well fresh case regardless ultimate collection hockey If Nick also hasn't put it up another one All right, here we go So we have total eight boxes I'm not gonna number them, but I'm just gonna X them Just so you guys know it's from the same case All right, let's generate two box numbers potentially one through eight All right, let's see box number four One two three four, so we'll go this bottom box and then eight Four five six seven eight we'll go the bottom box here So these ones will be for another ultimate for another time And then you got these two boxes here There we go. There's everybody dear Here Thicker pack just good sometimes Romano to start us off for the Montreux, Canadian is going to Brittany That's a 62 out of 449 Joseph Wohl Ultimate introductions that's gonna go to the Toronto Maple Leafs and Steve Birch Reed Duke rookie ascents Golden Knights Kevin with that one Skip that Nolan foot That's for the Devils and Brittany. I think I might have peaked a little bit This is who I think it is No Caprice off Wow signature masterpieces Congrats, Steve My first one. I haven't pulled them ever in any product. That's crazy Now have to have them like listen Stephen bring here from Minnesota. I love the wild like hurts me more because they're actually here But congrats, Steve. All right, here we go Alex for the mantra Canadians Looks like cards are already kind of a little dinkier in this corner Bow and Byram. That's for the Colorado Avalanche of Joe and Driesen We have Gillies sin For the Devils Brittany and last hit here is another one. That's Ty Smith Three-color patch to 99 a nice break for Britney still regardless with the Devils There we go guys. That was the break Very nice a Caprice off right there And again, if it hasn't been posted already, I'll post another two box break No, I'll post another one out guys. Jasper's case breaks calm


Hello, everyone. This is Lin Du, the founder and the CEO of Basic AI. Today, I'm introducing Xtreme One, the next generation open-source multi-model training data platform. A short introduction about Basic AI. I founded Basic AI seven years ago, aiming to speed up the evolution of the AI landscape and to build a more intelligent world together. Basic AI is globally inclusive. We can find us in Erwan, California, Seoul, Korea, and Chengdu, China. So during the past seven years, we have accumulated more than 10,000 different projects and are serving for hundreds of the clients all over the world. And also we presented the data-centric ML labs, especially Xtreme One, and the first open-source multi-model training data platform. And this product is built by the TechSuite team, which has very strong machine learning foundation and strong belief in open-source. And all the engineers graduated from top universities or worked in prestigious companies before. And also Xtreme One is a data-driven product. We have accumulated more than 100 terabytes data, and we have also abstracted the key pay points from the processing of those data. And our product is trusted by thousands of global partners, including Stanford University, Intel, Berkeley, etc. Xtreme One is built to accelerate the modeling process with advanced AI power tools. And also we come with entomologists, which were distilled from thousands of the projects. And also we offer a wide variety of data-curing features. So Xtreme One went open-source since September of the year 2022. And three months later, Xtreme One became a hosted project on the Linux Foundation AI and data. And so far, we are still the only project in the category of data annotation of the landscape by Linux Foundation AI and data. So why we build Xtreme One? UBS Global Research reports that now AI engineers are spending 70 to 90% of their time on training data. So from our past experience, we see that data has become the new bottleneck in AI model training process. Especially engineers are spending too much time on defining the data annotation schema to clean the data and to define the data pipeline. So we see there are lots of the repetition in data and the model fine-tune process. And now data is becoming more and more complex. From the previously single-frame image data to nowadays complex multi-modal training data, including the data from complicated sensors, LiDAR, radar, etc. And also engineers are facing data quality issues, garbage in, garbage out. So engineers are spending lots of time on improving the data quality. And also we are facing the data drift problem. So how to control this data flow to make sure our test data and training data are in coordinates? What is more, the data security problem? The companies, they are paying more attention on protection their data. And also the data labeling is very expensive as we all know. And all this labeling process lacks of the transparency. We have to face with the fragmented machine learning tools. So all these pinpoints we are addressing come to our solution. We call it the next generation training data platform. So speaking of the next generation, we are highlighting on the point that we would like to increase the efficiency of AI engineers. And for the past generation, most of this kind of training data platform, they focus on how to increase the efficiency of data labelers. The highlights of Extreme One. First, I would like to introduce Ontology Center. Ontology was the first introduced by Extreme One to abstract the definition of AI problems from the various model requirements. So actually Ontology is the abstract from the real-world problem to the data schema. And it can be reused and extended to build the knowledge base of AI algorithms, thus accelerating the model development. And from the Ontology Center, we can also do scenario search, recommendation, collaboration, and disambiguation. Also in Extreme One, we offer a full suite of annotation tools, including the most hard tool set to deal with a large language model, and also LIDAR basic and fusion tool sets, LIDAR segmentation tool sets, image and video tool sets, and task management, performance management, workflow management, and AI assisted annotation. Recently, the wide applications of large language model have skyrocketed and which also require a full tool set for reinforcement learning from human feedback. And in Extreme One, we come with the tool set, the full tool set for large language model, including the classification of the conversations from large language models, and also the rating, the dragging, etc. We also built 2D and 3D fusion annotation tools. That's why we call our platform as multi-model training data platform. In Extreme One's point cloud tool set, it is able to handle up to 150 million points count in continuous frame scenarios. And integrated auto segmentation models can also boost the efficiency by AI trainers. In Extreme One's annotation tools, we also support a full range of the model capabilities, and along with the parameter tuning capability. So the user may decide their own parameters during the model inference process. Here are some samples. In this slide-out fusion project, the user may customize their own parameters and the models. And one key, the results will be automatically calculated. And human laborers will only have to check the results and make minor changes of the result. Also, Extreme One provides very flexible workflow management for a team of all size with all quality requirements. The users may very flexibly set up the tasks and design the workflow and assign the corresponding tasks to different team members. The second most important part of Extreme One is its data curation feature. So actually, Extreme One is not a data labeling tool, but also it provides the full suite for data curation features. Like data visualization, versioning, organization, validation, consensus, augmentation, data drift analysis, and synthesis. For example, we support multi-model data visualization. And in this toolset, the user can easily check up all the results and to find the common cases to further address and to change. Extreme One also incorporated with Sata models. So actually, it is an AI-powered platform for maximizing the efficiency of data and the model productions. We use transfer learning to do the pre-train models. And we offer easy application for these Sata models. So actually, it's like we provide the environment for fast modeling and lifelong continual learning process. The last part is Extreme One's techniques. As an open source software, Extreme One also builds upon different open source solutions. So we compliance with the principles of cognitive architecture to ensure the scalability, elasticity, stability of the platform services. We have built an entire architecture, which is composed of an access layer, application service layer, base service layer, runtime abstraction layer, and infrastructure layer. Extreme One, the multi-model training data platform, faces challenges in managing and saving large-scale data in various formats, such as images, LiDAR point clouds, video and NLP data. To address these challenges, we rely on different technical solutions for structured and unstructured data storage. For structured data storage, we utilize TIDB, which offers a flexible and distributed data architecture that supports high availability. It is also compatible with MySQL and provides a rich ecosystem of tools for deployment, transfer, and synchronization. For unstructured data storage, we employ MinniO as a solution, which offers an efficient storage plan for labeling and accessing multi-sensory data. MinniO is compatible with the S3 API and provides features such as data loss protection, server-side encryption, and data persistency after writing. Extreme One also provides a unified scheduler for both multi-cloud and heterogeneous clusters, accommodating deployment in public and private clouds, to manage development, testing, and production processes. We use Kubernetes together with Ranger, which offers a user-friendly interface for quick application deployments and supports GPU sharing, where a media's Kubernetes device plug-in. In a sync computing process, we address challenges like data preparation, massive data sets rendering, compression, and chunking. To tackle these issues, we rely on Pulsar for cloud-native support, isolated computing and storage, and high performance with low latency. Extreme One originated from open source, and embraces the open source. So we would like to build a strong-native community with a culture of helping each other and make this product better and better, because we support a full lifecycle of data-centric MLOps. Incubated by Linux Foundation and data, Extreme One is experiencing fast growth. On the landscape of MLOps, Extreme One sits in the labeling category. We are looking forward for more collaborations with the open source community. Now we have set very clear roadmap for Extreme One. We will be enhancing the capabilities of Extreme One in more aspects, mainly in data versioning, visualization, and organization features. Just in last week, we had a new milestone, a thousand downloads from Docker download platform, and also we have 360 stars so far. We are still growing on a fast pace. Today, Extreme One has been used in multiple industries, including autonomous driving, smart retail, smart home, smart city, etc. We are looking forward to more applications of Extreme One. If you are interested, please visit Extreme One on GitHub. And welcome to join us and become part of our community. Thank you.


This research provides a detailed analysis of irrigation systems around the globe showing how different systems can affect the amount of water used and the amount of yield produced. The authors found that surface irrigation systems are the least efficient, using up to 60% of the water applied for no additional yield. Sprinkler and drip irrigation systems were found to be more efficient, using less than half of the water applied for the same yield. Additionally, the authors found that replacing surface irrigation systems with sprinklers or drips could increase crop yields without increasing water usage. This article was authored by J. J. Jermeyer, D. Curtin, J. Heink, and others.


20 jaar geleden was ik in Houten, het met een ouding van de 2003 State Electroën en ik heb een ouding van New York gehaald.      En die zei, welle, He said the White House believes that in defeating us that are the same, that they are quickly greener and that there is an opportunity for America to intervene in other Arab dictatorships, even in Iran. He said this will quickly remake the Middle East. The Middle East will be remade for market economies and democracies and peace with Israel. There will be an unimpeded flow of oil to Western governments. He said the example of the remaking, the rebuilding of Iraq will be impossible for any other Arab state to resist. In that spirit that invasion had taken place. The invasion was based on the same faithful focus that is directing a very good policy in Asia today, 20 years on. It's a focus on a word that Lawrence used, privacy. Or as Gary Evans puts it, this is about the DLP words, dominance, leadership, privacy. America's goal is to see that no power can channel, can challenge its privacy in the world. And that is the spirit that drove the invasion of Iraq after America's win over the Soviet Union in the Cold War. A concentration of opera nationalists and neo-conservatives formed the doctrine to guarantee that America could never be challenged. And any nation that sought the challenge would be reduced to rubber. The focus was on entrenching in the wake of its victory over the Soviet Union, American dominance, leadership, privacy. And that's the focus of US policy in Asia today to respond to the challenge that China represents to American dominance, leadership and privacy. And we are forward up against it. In 2017, I noticed the shift in what was being said by Prime Minister Turnwall and Foreign Minister Julie Bishop about China. There was a sudden shift in rhetoric and I became curious. Some Chinese, I remember raised with it once, was the then Chinese ambassador in fact and said, what's going on? Julie Bishop was just being saying, China will never be great until it becomes an opera singer. And speaking, Singapore Melton Turnwall said, we need a very good military build up in Asia. It was an unmistakable shift. And that was backed by all sorts of things appearing in the media. I recall John Gardner, who later became advisor on China policy to Melton Turnwall, saying that the Chinese students in Australia were embodying ethno-nationalism. Because I was working in this area at UTS at the time, I committed to a research project. There were 130,000 Chinese students now in our university. There were only four incidents where it couldn't be alleged students had pushed an argument in a classroom. I'm serious, there were four incidents in four reports in the media of incidents where a Chinese student pushed back against a map that showed Taiwan as an independent country. For example, but the headline is here. We're facing ethno-nationalism from Chinese students. It's a concrete example where I ran the China Bank. For five years, now seven years, we had China Bank. With no evidence to justify, for example, a headline on the telegraph, the Chinese ownership of solar panels in West of East South Wales gave them the power of one like our electricity system. Or a story in the Sydney Morning Hero broken as an exclusive that the Chinese had plans for a base in Vanuatu. It took Prime Minister Turnbull standing here in Commonwealth Summit next to the Prime Minister of Vanuatu to say, this is not the case, Vanuatu is a member of the long alive moon. We had a four horrors program among other things that will lead to the big serious Chinese history in the United States of Public Service, a quote in the case of a public servant who had sacred material ladies home in Canberra. Anyone watching that four horrors program in 2017 would have assumed serious assault, like Canberra, directed by Chinese security agencies. The public servant was taken to court, he's been issued with a $200 fine for having minor documents in his own something of Donald Trump and Joe Biden, himself responsible for in recent months, he was dreaming. But if you watched four horrors, you'd have believed in part of a major Chinese history in the United States Trust. We've produced a document in the NCS called China, Australia Talks China replete with examples of stories loaded into our media with the help of security agencies to create the sense of a Chinese threat, and sometimes across Chinese behavior, fitness, mistreatment of Uighurs, for example, on a Western China. But everything was subject to almost unlaperated exaggeration, lead upside down. One of her most experienced editors is someone called Max Such, the editor of National View, we edited the old National Files. He investigates this China panic in the media. He said there's an editor he witnessed many campaigns in the Australian media over the end. He had never witnessed any as professional as the China panic campaign unleashed in our media from 2017. Malcomton, influence legislation, it's on the course to burn on the books of five years. It hasn't produced a single example of Chinese horrors, but I could instance, the US study centre in Sydney, or ASPI, Australia's Purity Policy Institute, which receives funding from the State Department and American Army in those countries, as pure examples of foreign influence seek to be shaped by Australian foreign policy that deserve the media to be orchestrated by the media. And talk about another lobby, which is the best funded. Most generously start from foreign influence lobbying. You can imagine operating in Australia today to see if the Palestinian voice gets plotted out at every opportunity. Who was driving us? Why were some juniors being favoured with a special thing, be it the home of Shiket Muslim-Main at 6 in the morning tomorrow? And you can have an explanation about a raid on the home of the member of the NSW House. That was three years ago. Shiket Muslim-Main's political career was destroyed. Not a fine thing has been made against him. Anyone would have assumed that that story was packaged and massaged and presented exclusively to Nick McKenzie for 60 point error and 60 minutes that Shiket Muslim-Main had to lengthen himself to become an agent of Chinese influence, as if a whip in the NSW House was capable of anything that would be of interest to Chinese agents taking interest in Australia's geo-strategie position. Absurd. I can go on. We brought these things together. When I was at a UTS, we brought these things together in a publication. I think the clue to it lies in an article. Someone who is now the director of the Office of National Intelligence, Andrew Sheeran, had worked as a foreign policy adviser to Tony Abbott and briefly for Tony. He wrote in this giveaway that there are some people here in Washington who are working with American Think Tech at the time who think that Australia is still a very good ally, prepared to take the fight with a very good side-by-side in the Middle East. But Americans at the beginning and down in Australia is such a strong ally in Asia. I think that was a similarly important article. I believe that the biggest factor in this China package driving this consistent mass-article in Australian media were people in Australian security agencies who believed their counterparts in Washington were disappointed and fearful that we might not go all the way when they knew it was China and wanted this corrected. I believe with that very remotely for spirits of theorists that this is a large part of the journey this country has been on. The professor of industrial and international relations in the Chicago University John Meershine or an advocate of American national interest was a guy in the foreign policy who said when he was in Australia a few years ago the opportunity to be, I heard this from him directly, he said the same thing publicly. He said America will never allow its privacy to be challenged. We showed in World War I defeating the Kaiser Germany, we showed in World War II defeating two rivaling buyers. We've shown in defeating the Soviet Union that we will never allow our power of dominance to be challenged. The alternative, new friends, is that there is room for multiple sovereigns on this planet. And that is that we will be able to touch between British and Soviet Union, invading Afghanistan, supporting only North Vietnamese invasion of Cambodia, presiding over an arms drill gun that they taught between Red Earth Russia and America under Nixon, that they taught between China under Xi and America under Biden, to justify a war between these sovereigns. It can very easily become a nuclear exchange. Two sources for that. It's quite excellent sleep war to war. It spells out the subjects to which one side of the other could decide to demonstrate its seriousness with the nuclear strike that would seem the other side back down, fearing that if it responded with a nuclear exchange there'd be a mass exile from the other taking other city.  No one believes, no expert believes the risks of a nuclear exchange here can be dismissed as critical. We've got to research something with the spirit of South East Asia, the nations of South East Asia believe in themselves they can live in a world where power is a region where power is shared between China and the United States one balance in the other in a principle that has been known to underpin peace the borders of war in human history if Singapore believes that it can deal with a strong China as one of their former farmers has said very eloquently then who are we to dash up to Singapore and say you're wrong? The Singaporeans are anticipating a world in which power in the region is divided and in which they welcome the fact the Chinese power is offset by an American presence just over the horizon and vice versa Indonesia has demonstrated the same system the Philippines will fluctuate Philippines nationalism finds an expression of anti-Chinese postures at the present time that's what you can expect in a region of 10 nations each finding its own way and having different attitudes at different times but the region there is no nation in South East Asia itching to join a showdown over Taiwan and I conclude by undermining that the historic Australian position is in Taiwan non-triggered answers and that's what Alexander Downer gushed out in a burst of ill-applies to truth-telling in 2004 when the H. McDonald to put to him in China wouldn't the answers treaty apply in the event of a showdown in America and China in the Taiwan states? Alexander Downer said though and indeed he was thinking through a tradition in Australian diplomacy that goes back to Menzies prime minister in 1949 to 1966 on two occasions Menzies was inspired by Washington to take a stand on Taiwan one was Eisenhower president Eisenhower was saying we fear there might be a war the Chinese threat of oil violence Menzies liberal prime minister went to Washington and advised against it and said Australia would not be involved in it when President Kennedy invited Australia to lead a community of nations that included Taiwan Menzies liberal prime minister said that the American president nothing doing we won't lead a new community of nations in Asia we support Taiwan it was not going to be when I started to send to the department can you give me can you give me a briefing for my first visit to China what if I asked the Alexander Downer question I got a very concise briefing for the fact would Australia be committed in a dispute over the Taiwan streets the fact recommended that the deputy minister said that's a hypothetical question what if the leading assistant would definitely recommend that the robotic minister should say the answers treaty is an obligation to insult that was the official response from Australian diplomats to me in May 2012 going to China why can't we return to that position why can't we say that as an American ally we're not going to be committed to an entirely unnecessary war over sovereignty in Taiwan let's reinstate the diplomatic status quo the forward words that since 1972 enable the people of Taiwan to fulfill their own aspiration enable China to have recognised or acknowledged its position that Taiwan was the province of China both sides happen America several moment foreloaders the Shanghai Communicator after Right Kissinger we need that wisdom back again the war wouldn't be a horror for all of us, our country included thank you for that


Hi everyone, Joe from jaskyscasewrakes.com coming at you with 2021 Topps Archive Sincture Series Baseball. This is Active Player Edition, doing half a case, 10 boxes, and it's a random player break, number 15. We sold 19 spots, and each spot gets 7 players from this big list below. It's 133 names on here. Big thanks to these folks for getting into it, so let's multiply this by 7. So there's one already, there's two, there's three, four, five, six, and seventh and final time. So you can see Sean Aldinger's last spot mojo star, one, two, four, five, six, and seventh and final time. And I've got all the players right here from Aaron Hicks all the way down to Zach Wheeler. I think he's having a really nice season. Alright, let's roll it. Let's randomize names and teams three and a four, seven times, or names and players. One, two, three, four, five, six, and seventh and final time. After seven, we've got Daniel down to John. Here's the player list right there. You can see Daniel down to John. Three and a four, seven times, four of the player names. One, two, three, four, five, six, and seventh and final time. Three and a four, seven times, there's seven right there. The Labor Day all the way down to Fernando de Tis Junior. Alright, so I'm just going to show you the list as is, and then I'll alphabetize by your first names. So there's the first chunk of names right here, just so I could get all this on the recording. And if you're watching live, you can also, there is a DVR function. You should be able to pause the video just to keep track of your players if you want to, make sure you return live. Hit that live button, make sure you're back live. Otherwise, you'll be lagging behind. Alright, so let's sort alphabetically by your first name. So Chris, there are your players right there. Daniel Katz, big chunk of players. Eric, John, John's got a lot of players here. Kevin, Matt, Matthew, Paul, Sean, Sean O'Leary. There's no big chunk of players there. And last but not least, Tyler. Alright, let me flip away from the screen for just a second, and then we'll pause the video, maybe give you some time to trade. Here is the case right here. There it is. It's a 20 box case. We're doing half of it. Other half is in the store on jaskyscasebreaks.com. Alright, so we have 10 on the left and right sides. So we'll roll, we'll select a die, we'll roll a die, and then we'll see which side we're going to do. One, two, three for the left side, four, five, six for the right side. And it's one, so we're going to do the left side right here. Right side we will save for next time. And let's flip back over here. Okay, we're going to pause the video when we come back, we're going to see if there's any trades, and then we'll have the break, stick around, BRB. Alright, welcome back folks. No deals are done, so let's see what we're going to find in here. Alright, 2021 Archive Six series. Active player edition. One in case buyback autograph per box. Look for rare dual autograph cards. Randomizers, of course, if they're two different teams. Good luck. I don't think they're covered up, so let's open here. Not covered up. Good luck. We have David Dahl. One out of 99. You can see the stamp up there, the archives stamp right there in his autograph. And David will go to, that'll be for John, John M with David Dahl. And here we have a Jesus Lizardo. 12 out of 99. See, 17. 17? No, 12. 12 out of 19. Can't read. Jesus Lizardo, that'll be for Paul, Paul K. Next auto is Jorge Soler. 24 out of 40. Jorge Soler, where are you? You're going to go to Matt McLaughlin. There you go, Matt, on the board. Kettle Marte, 29 out of 36. Need him to stay healthy for my fancy baseball team. And he's healthy. That's pretty good. Kettle Marte, that's going to go to John, John M, again. Another box. Oh, it's going to go this way. It's Starling Marte. Kettle Marte, now Starling Marte. This one's 23 out of 84. You can see his autograph right there. Sort of hard to see. Let's Paul K. With the Starling Marte. Another five. The one in landscape mode. It's Mike Moustakis, one of one. See the one of one stamp right there. Nice. Moose. And that goes to Sean Aldinger with the Mike Moustakis. That's one of his last spot mojos. Right there. Strikes again. 70% of the time, last spot mojo hits 100% of the time. All aboard. The big hit express. Out of fives and under, of course. Get the world famous train whistle. We got here. We have a Colin Moran. 30 out of 33. Colin Moran is going to go to... It's going to go to Matthew P. Got a nice Keston hero. One out of 99. Am I increasing the percentage on last spot mojo? Well, last few weeks. Last spot mojo has been pretty strong. A few weeks ago, I would say it'd be 60% of the time. Last spot mojo hits 100% of the time. It's crept up to 65. Now 70. It's been on a good run. Next up is Trent Grisham. Nice rookie autograph. 28 out of 72. Oh, the Keston hero, by the way. Keston hero autograph, where are you? Sean O'Leary with Keston hero. And the Trent Grisham is going to head off to Sean O. Here you go, Sean. Saw him at the shop earlier today. Alright, final box. Good luck. It's going to be... 8 out of 90. David Bode. That's his facsimile autograph. He's got his real autograph in blue above that. David Bode. And it's not a dual autograph, folks. It's just one of them's real. Matthew P. with the David Bode. Thanks, everybody. That was a nice quick little break of 2021 at Topps Archive signature series. Active player edition. Thanks for watching. Thanks for breaking with us. I'm Joe. I'll see you next time for the next break. Bye-bye.