In the last few lectures, you have been exposed to cycle analysis and the associated aerothermodynamics of flow through the jet engines, various kinds of jet engines, which are used on aircraft or flying. These aerothermodynamics cycle analysis must have been exposed to you, all kinds of component analysis, engine analysis as a whole and this has been covered by Professor Pradip. In today's lecture, we will take a look at one of the components and that is compressors and try to look at it from thermodynamic point of view. One of the reasons is that compressor is a working machine. It actually absorbs work supplied by the turbine and then converts that work to pressurization of air. Now, that is one of the intention of the compressor inside the gas turbine engine. The other purpose is that the compressor as a working medium is also part of the jet engine, which incidentally is also a heat engine. So, all affairs connected to any kind of heat engine needs to be analyzed in the overall matrix of thermodynamics. So, any component which is there inside a jet engine must necessarily be subject to a scrutiny using fundamental thermodynamic laws and this is what to some extent has been done in great detail through the cycle analysis and today we will look at thermodynamics of compressors and in the next lecture, we will look at thermodynamics of turbines. So, let us take a look at thermodynamics of compressors. The compressor thermodynamics essentially comes from the fact that you have a flow, which is in our case essentially air, which is performing work and this work is available or made available by running the turbine and the depiction of this work, the expression of this work can be put down in form of thermodynamic expressions, which means the work that is transferred from turbine to compressor and the work that is done by the compressor in the form of compression or pressurization can be expressed in terms of thermodynamic parameters and this is what we intend to look at a little closely today through various methods of fundamental thermodynamic relations. Let us take a look at fundamental thermodynamics of compressors. One of the reasons I said that we would need to analyze the compressors and of course, later on turbines through thermodynamic means is because it is part of the heat engine and they need to be subject to the scrutiny under thermodynamic matrix and if we can show that they are amenable to fundamental thermodynamic rules and laws, then it is possible to provide a prediction mechanism of the amount of work they are doing, the amount of work that is transferred between turbine and compressor and the efficiency with which this work is being transferred or this work is being done. Now, this is the prediction that is required by the engine designer because he needs to know how each of these components is going to perform and then overall how the engine is going to perform. So, this prediction mechanism that thermodynamics can provide is an important aspect of the development and creation of the engine. So, this is one of the reasons why we need to have a good look at the thermodynamics of compressors and turbines. This also allows another important aspect of creation of the engine and that is it allows for optimization of the cycle design. You have done all the cycle analysis over the last few lectures. Much of these cycle analysis would be subjected to an engine design effort and during that process it is inevitable nowadays that an optimization would need to be arrived at. So, the final design is invariably an optimized cycle design which is the fundamental basis of the development of the engine. So, this optimization is another possibility that thermodynamic analysis throws up. Let us take a look at some of the fundamental issues. If we have a simple compressor in which you have let us say to begin with a closed system something which many people are familiar with. You have a closed system in which work is expected to be done either by let us say a movement of a piston or by expansion of gases. It could be negative expansion and the work done can be expressed in terms of the motion of the piston or the change of volume of the enclosed gas. Now, those expressions are written down there and it shows that for a closed system it is comparatively simple probably to write down the work that needs to be performed to do the process of compression. Now, when you have an open system the work done by an open system or an open compression is a little more involved. To begin with the flow is coming into a system which is let us say the square red system that we have and it is coming in with a pressure v 1 volume v 1 and it has a mass flow rate m dot 1 and it is exiting the system with pressure p 2 volume v 2 and a mass flow rate m dot 2. It is possible under many systems m dot 1 would be equal to m dot 2 but that is a separate issue. The work done by this kind of an open system in which it is flowing the fluid is flowing it is coming in and going out on a continuous basis.  Now, the third term is the work done for the compression process. The first term is the work done for the air entry and the second term is the work done for the air exiting the system. So, in an open system it enters the system with a certain amount of work it exists a system with a certain amount of work and during the process of its resident time within the system a certain amount of work is done and in our case for the purpose of compression which means in the process of the flow going from 1 to 2 it experiences compression or pressurization. So, this is a simple way of writing down how the work can be expressed for a compression process. If we show the thermodynamic process of compression in p v diagram something you have already done before in your cycle analysis. Let us take a quick look at the same thing may be with a different idea in our mind. The process from 1 to 2 in the p v diagram is typically a polytropic process a real process. The corresponding ideal process is 1 to 2 prime and that was often called adiabatic process. If it is a reversible adiabatic we would probably call it isentropic process. Now, these are the two processes with which we could start off and the difference between the two is delta H that is the work extra work that is needed to be done to accomplish the pressurization from pressure 1 to pressure 2 from line 1 to line 2 and this process of pressurization requires that much of extra work if the work done is not ideal that is adiabatic, but polytropic. Now, on the right hand side you would see a number of other possibilities in a p v diagram you could have a process which is isothermal in between we have the process which is adiabatic the so called ideal process and the third process which is a theoretical possibility is an isochoric process where the specific volume remains constant and the pressurization goes from 1 to 2 triple prime. So, 1 to 2 double prime is the isothermal process where the temperature remains constant and 1 to 2 triple prime is the isochoric process where the specific volume remains constant. Now, as you can see the index which is normally used for signifying the process in case of adiabatic process normally this index is gamma in case of other processes we often might like to call it some k in case of a general polytropic process non adiabatic process k is likely to be greater than gamma in case of isothermal process k would be equal to 1 and in case of a isochoric process the k would be infinity. So, these are the theoretical possibilities in which the polytropic process is a realistic process which does not conform to any of these adiabatic isothermal or isochoric theoretical possibilities, but a general polytropic process. If we say that p 1 v 1 and t 1 are the inlet or the initial conditions with which the mass flow of m dot 1 is coming in and p 2 v 2 and t 2 are the exit or final conditions with the mass flow of m dot 2 the work done by the system is given by integral 1 to 2 w that is the work done would be equal to minus of integral 1 to 2 of v d p which we can also write down as minus of integral 1 to 2 of d p by rho. Of course, is the density of the gas or air and v of course, is the specific volume of gas or air. Now, in a real compressor as I just mentioned a little while ago the flow is likely to be quasi static which means m dot 1 may not be equal to m dot 2 and there is a possibility that the flow may not be adiabatic that means it could have some loss of heat and some unused energy that is let out at the outlet that means certain amount of energy that was used for the intended purpose of compression is now available as exhaust energy and goes out with the outgoing flow. So, that is what is likely to happen in a real compressor which is we are generally calling a polytropic process. If you look at the PV diagram and on the side you have a system in which the flow is coming in with p 1 v 1 and let us say a velocity c 1 in which case it could be an actual velocity c a 1 coming straight into let us say a ducting system and then we say that this process now has a possible heat addition or rejection. Now, this heat addition is shown as delta q r and the heat rejection is shown as delta q q q subscript small q. So, the heat net heat added to the system is then given by delta q is equal to delta q r minus delta q subscript small q and this q r that is said to be added to the fluid that is flowing in inside the system may be assumed to have been added by the fluid friction. So, that is one of the possibilities and q subscript small q is the heat loss to the surrounding which often happens due to the normal heat transfer to the surroundings. And as a result of this we can write down from thermodynamics that delta q the net heat that is added to the system is c r into d t where c r is a specific of the particular fluid gas or air for this particular real situation. We know that specific heat for a constant process pressure is known as c p for constant volume it would be called c v. This is a process which is neither constant pressure nor constant volume some real process and we simply call it we are simply calling it c r for the time b. So, the process that we are seeing here is a little more realistic process subjected to a compression. Now, if we proceed along this we can say that the work done in any real process may be split up in work done for two ideal processes. One is the energy added to the fluid that is by delta q is equal to c p d t minus v d p and we showed the v d p in the earlier diagram. This is your v d p and this is of course delta p d v. So, if we add the those work done to c p d t which is the energy added to the fluid and energy taken away from the fluid can be put down in terms of c v d t plus p d v then for an isentropic process the work done can be written down simply as delta q is equal to c n d t where c n is the specific heat of the isentropic process. Let us say let us put it that way and then the net energy transaction in an isentropic process is typically 0 because it is an adiabatic process. So, delta q is actually the heat added or subtracted from the system is likely to be 0 in which case c p d t would be equal to v d p and c v d t is would be equal to minus p d v from the above equations. If we do that and then use the concept of isentropic index which you have used in your cycle analysis. This is normally defined as gamma is equal to c p by c v and now we can see that it can be written down in terms of v d p divided by minus p d v where c p is the specific heat at constant pressure process and c v is the specific heat at the constant volume for the air or gas. It depends on whether it is air or what kind of gas. So, the value of c p and c v would depend on the values of properties of the air or gas. They also depend on the conditions of the air or gas notably the temperature of the air or gas. If we do that the concept of specific heat ratio can now be extended and we can write down that the polytropic index for a real process can also be defined for a real process as k just like gamma and it is also a ratio of v d p by p d v. So, that ratio remains as the fundamental definition of the specific heat ratio and now we are saying it is a real process a polytropic process and we say we designated by k small k and this can now be written down from the earlier equations as c n minus c p where c n is the specific heat for a isentropic process c p is that for a constant pressure process and that is divided by c n minus c v and that would be equal to from the earlier equations one can derive gamma multiplied by 1 minus d q by c p d t and the whole thing divided by 1 minus gamma into d q by c p d t. So, that is in a nutshell the fundamental definition or concept of polytropic index similar to the isentropic index gamma which is used in cycle analysis especially in ideal cycle analysis. Thus we say that if delta q is equal to plus or minus delta q r plus delta q q and if that is greater than 0 that means the net heat that is going into the system is greater than 0 then the polytropic index k would be greater than gamma. If the delta q is 0 then it is an isentropic process and k would be equal to gamma if the process is isothermal then the value of k is 1 for the ideal gases and this is what we saw in one of the earlier p v diagram. So, this is what comes out from the definition of polytropic index as it is used for the gases ideal or real used in various cycle analysis of the engines. Now, if we look at the T s diagram or more appropriately referred to as temperature entropy diagram which can also be referred to as enthalpy entropy diagram in the sense the enthalpy entropy and the temperature entropy diagrams look exactly same except that in one case the y axis is enthalpy and the other case the y axis is temperature in both the cases the x axis is entropy. Now, if we put the various compression processes we were talking about earlier and we can see here that the isentropic process where k is equal to gamma go straight up from 1 to 2 prime and then we have the polytropic process where k is greater than gamma and that is from 1 to 2 that is a real process and then we have k equal to 1 which is the isothermal process that is 1 to 2 double prime over here and then k equal to infinity where change of specific volume that is 0 that is isochoric process and it goes from 1 to 2 triple prime. So, all the processes we had talked about earlier are now shown here on the T s diagram and those are the typical lines or the path through which the compression process would proceed from 1 to 2 to being the end of the compression process. Now, in case of a compressor that we are talking about in typical jet engines the working of compression is accomplished in a open volume and there is a continuous flow of high speed air or gas in case of compressor its air and we often adopt the so called isentropic process as a reference or a benchmark to categorize or find out the goodness or badness of a real compression process. This comparison between the ideal compression process or isentropic compression process and the real compression process is referred to as the isentropic efficiency of the process. So, isentropic efficiency of the process is essentially a comparison between real process and isentropic process and hence we need to know a priori what is the isentropic work done. Before we know what is the real work that needs to be done because that then we will know what the isentropic efficiency is and we will know how close we are to an ideal isentropic process and in a sense how close we are to the original joule Brayton cycle which is the fundamental matrix of jet engines. If we look at the thermodynamic depiction of a row by row process of a compression through rotor and stator. Now, we know the rotor does work and stator does not do any work really speaking. We will be talking about those things in great detail in the chapters to come. The thermodynamic path taken by the air through these compressors through rotor and stator can also be shown in terms of the T S diagram. The path through the rotor is actually the work done. So, in isentropic work is the vertical work along the vertical line and then the stator work is the horizontal line where no work is being done and the work is essentially isothermal. So, this is the isothermal work that we were talking about and this is the isentropic work that we were talking about earlier. So, along this k is equal to gamma along this k is actually equal to 1. So, it is a combination of these two that make up for the entire compression process through rotor and stator. So, that is how the work through the compression process actually proceed. It is k equal to gamma and then k equal to 1, then again k equal to gamma and then again k equal to 1. So, it is the step by step process by which the compression actually proceeds through the thermodynamically in the typical T S diagram if one does a rigorous analysis. What of course, happens is that the exit kinetic energy of the compressor is often of the same order as the inlet kinetic energy and as a result of which it is expected that the entire work that is supplied would be converted to pressure. As a result of which what is often done is through this steps an average line is drawn and that average line is what we see in our cycle diagram representing the entire compression process. Actually it proceeds along the line that we have shown if it is a real process it proceeds along the dotted lines and then it reaches at the end of compression. What we show in a cycle diagram is we simply connect the entry point and the exit point through an average curve and that is depicted as the compression process in a T S diagram. So, a rigorous depiction of the compression process would have to be progressed in a step by step manner. Let us take a look at how you show the efficiencies of the compression. The high efficiency of the compressor and turbine that we would like to achieve actually takes the cycle pretty close to the Joule-Breton ideal cycle. Closer we are to the ideal cycle, closer we can say that adoption of the Breton cycle as the basis of a jet engine is fundamentally viable proposition. Further we are away from the Breton cycle in actual engine operation. Adoption of the Breton cycle is then not acceptable or it remains a questionable matrix of analysis of jet engine. So, only way we can make sure that the jet engine is pretty close to a Breton cycle is by ensuring that the compressors and the turbines and other components of the jet engine do have very high efficiency operation and they are pretty close to the isentropic process and this efficiency that we are talking about is indeed the isentropic efficiency which I introduced just a few minutes back. This thermodynamic efficiency or what we call the isentropic efficiency can be shown in terms of the work that is being done ideally, the work that is being done really and the real and the ideal work can be put together in one relation and that relation captures the essence of the work that is going on through the compression process. So, let us take a look at this thermodynamic efficiency definition. Now, this definition to understand this definition a little let us take a look at the thermodynamic depiction of the compression process and this time I have put a H s diagram which is the enthalpy entropy diagram very similar to that T s diagram that we had looked at and what is shown here of course are the various work that has been done and as you can see here this is the work ideal work that is being done ideal adiabatic work in a stage and then you have the work split up in rotors and rotor and stator and then of course you have the real work done over here in H that is a real work done through the stage again that can be split up in rotor and stator that is H 1 and H 2 and then of course H subscript 0 is the total work done in terms of the stagnation parameters through the particular stage. So, all the various kinds of work that this particular compressor stage is doing is being shown here the blue line that is going from 0 0 to 0 1 and then to 0 2 is the total change parameter that is stagnation change parameter and hence can be called the stagnation work done from 0 0 to 0 1 and then from 0 1 to 0 2 which is of course the stator where no work is being done. So, the actual work done is from 0 0 to 0 1 the corresponding static work is from 0 to 1 and then from 1 to 2. So, these works are all shown here and they are written down over here the last 3 of the kinetic energies at the various stations shown as H C 0 and H C 2 and H C 1. So, these are the 3 kinetic energies that the flow carries through the compressor at stations of 0 1 and 2. Now, on the basis of this depiction of the work done through the compressor stage the definition of the efficiencies can now be looked at again. This is something very similar to what you must have already done in your cycle analysis. Let us take a look at it and understand how we can make use of this in our thermodynamic analysis of compressors. Now, what is shown here is the efficiency of compressor in terms of the work done. This is the ideal work done this is the real work done and work at station 0 this is a work at station 2 and the numerator is the ideal work and denominator is the real work done and the ratio of the two is the efficiency which we have called isentropic efficiency. The work done as you know can be written down in some in terms of C p into temperature differential. If we assume that the C p of real and ideal processes are same and that is an assumption for the time being the temperature differential or the ideal temperature differential and the real temperature differentials come into the picture and the C p gets cancelled out on what we have is the temperature ratios the ideal temperature ratio to the real temperature ratio across the compression process. The ideal temperature ratio can also be shown in terms of the pressure ratio across the compression process and now we can see that the compression ratio that we intend to achieve comes into the picture over here and if this is the compression ratio we intend to achieve this can be put here and would give us the ideal work that is necessary. The denominator of course is the real work that is actually being consumed and the ratio of the two of course is the overall isentropic efficiency of the compression process. Now this compression work can be shown in terms of two mean indices. Especially if they are finite processes as it is normally in a stage if we consider a stage which is a small change in pressure we may consider it a finite process and then the indices that we have talked about k can be shown in two different ways. The first one is often called thermodynamically the first mean index k 1 and that is something which we have defined before and that is integral 1 to 2 minus V d p divided by integral 1 to 2 P d v of the finite compression process. There is another definition and that is the second mean index often referred to as k 2 and that is defined as l n that is natural logarithm P 2 by P 1 divided by l n of V 2 by V 1 V 2 of course V of course is the specific volume and this can be written down in terms of what is known as the polytropic relation that is P 1 V 1 to the power k 2 is equal to P 2 V 2 to the power k 2 which means we can write for a compression process P v to the power k is equal to constant. So, that is another way of showing the polytropic process in case of isentropic process it would be P v to the power gamma equal to constant. In our analysis of jet engines without getting into very minute thermodynamic analysis it is often customary to assume that the average value of the index as shown above the two of them are equal to each other and hence k 2 is equal to k 1 is equal to k in all design computations of a typical jet engine. So, the two mean indices their definitions are slightly different from each other can be considered to be one and the same. So, if we can get a value of the index through one of the mechanisms we can use it in the other relation that is P v to the power k and carry on our analysis thermodynamic analysis of compression process. Now, this total head based compression process that we have talked about let us have a quick look at the H s diagram that we had a look at you see the blue line shows the compression process where the changes are occurring in stagnation parameters from 0 0 to 0 1 and from 0 1 to 0 2 which means there is a total temperature change from T 0 0 to T 0 1. Similarly, there is a total pressure change from P 0 to P 0 1 and then to P 0 2 and there is a enthalpy change from H 0 to H 0 1 and H 0 2 those are the stagnation properties stagnation temperatures stagnation pressure stagnation enthalpy. Now, those stagnation changes are what is shown here through this blue line. If we show a thermodynamic process in our cycle through the stagnation property chain then it stands to reason that we should be using a total head based specific heat which means instead of C R that we had written down earlier for a real process we should be writing C 0 R. Now, this C 0 R for a total head based specific heat definition can now be written down as C R to the power ln T 2 by T 1 divided by ln T 0 2 by T 0 1 such that delta S of course, is the entropy is equal to C R into ln T 3 by T 1 across the entire compression process and that would be equal to C 0 R into ln T 0 3 by T 0 1 T 0 3 being the exit condition T 0 1 being the entry condition. So, it is possible to actually come out with a specific heat based on total temperature based and total pressure based process in which specific heat is now being shown as C 0 R as opposed to C R as we have done before. Now, that brings us to the point that if we do that then the specific heat ratio that we have talked about k for a polytropic process also should be shown in terms of the total change of parameters and we can say it is depicted as k 0 for a real polytropic process. This k 0 can be written down in terms of k 0 by gamma minus 1 divided by k 0 and that would be equal to k by gamma minus 1 divided by k into ln T 2 by T 1 divided by ln T 0 2 by T 0 1. Now, these are all derivable definitions from the earlier thermodynamic definition that we have just introduced. What happens is if you do that if you introduce this specific heat ratio as a total parameter then if the entry and the exit mark numbers through the compression process are equal as we have said it sometimes could be equal then for all practical purposes k 0 is equal to k and we do not have to bother about k 0. However, if m 1 is greater than m 3 then k 0 is likely to be greater than k 1 and in many practical compressors quite often it may well be so. If for example, if k is equal to 1.5 and the value of k 0 will vary quite a lot above 1.5 if m 1 is greater than m 3 and this variation along with the mark number or velocity variation across the compressor then would have to be factored into the rigorous cycle analysis that needs to be done to get a more realistic appraisal of the work done and the efficiency of the compression process. Let us quantify the effect of these changes. If we have a change of k as we have seen k varies away from the ideal value which is 1.4 and if for example, we have a compression process where it is ideally 1.4 that is air we say that the compression has an efficiency of 1. Now, if the value of k is 1.5 the efficiency starts falling and if it goes all the way up to 1.8 the efficiency of the same compression process would fall all the way to 0.644 which is only 64.4 percent which is rather low efficiency. So, we can see that the compression efficiency would be dependent quite a lot on the value of k and the value of k of course depends on the real polytropic process that the compression is executing. If we look at k 0 and its effect on the compression efficiency we see that as the value of k 0 changes from k to 1 value to another and as the compression ratio changes the value of efficiency changes substantially. If we have a compression ratio which is very let us say 1 ideal that means no compression at all we say that the efficiency is 1 and when the value of k 0 changes it remains 1. But once the compression ratio increases from 1.2, 1.5 which are stage pressure ratios and then multistage pressure ratios of 2, 4, 6 and 10 for a value of k which is now let us say 1.5 the or k 0 for example, if the value is 1.5 the efficiencies would start falling and we can see that the efficiency falls all the way up to 94 percent. If the efficiency ratio that we are looking at if the value of k now changes to 1.8 the efficiency would start falling substantially and this efficiency ratio that we are looking at falls from 1 to 0.81. So, these are the various effects of the value of k and k 0 if we use k 0 for total based cycle analysis and we see that they have substantial effect on the efficiency computation that one may like to do for cycle analysis of jet engines. Now we take a look at what happens if we have a compression process with a certain amount of heat transfer what does happen is that when the process of heat transfer is going on the compression is affected. Now the blue line 1 to 2 adiabatic is indeed the ideal process or we may call isentropic process. On the other hand the red line 1 to 2 is the polytropic process where heat transfer across the process is still 0. So, it is a polytropic process where there is no heat transfer isentropic process of course, has no heat transfer anyway. And then we consider two processes one in which the heat transfer is greater than 0 another in which the heat transfer is less than 0. So, in one case the compression process or compressor is subjected to certain amount of heating and in the other case the compressor is subjected to certain amount of cooling. Now we can see that the area under the line 1 to 2 is indeed the extra work that is done to overcome the losses of a real process or polytropic process and that is the extra work that one has to do to overcome this path 1 to 2. For the time being we are considering this to be a linear path 1 to 2 we have seen before that this path could be curved for a long compression process. Let us consider a small compression process in which this path is let us say a linear path. And then we can say each of these can be considered as rectangles or triangles and as a result of this we have heat transfer now being introduced into the compression process in which extra work is necessary to overcome the work done in a polytropic process. As we can see now if you introduce heating you would actually need to do more work because the entropy rise or the loss in such a process would be even higher and you would actually need to do more work because the path from 1 to 2 prime now is longer to accomplish the same pressurization from P 1 to P 2. So, in all these processes the pressurization is same from P 1 to P 2 this path is longer which means you would need to do more work the temperature rise from T 1 to T 2 prime is higher. So, you would actually need to do more work. On the other hand if you have a cold compression process the area under that is smaller than the earlier polytropic process and as a result of which you have lesser work to be done for the compression process. And this means that if you have a certain amount of cooling introduced in the compression process you can actually get away with doing less of compression work. And this is the thermodynamic concept which has given rise to various kinds of a cooled compression process or in case of jet engines or various kinds of gas turbine engines. The concept of intercooling or even simple cooling has been used for many many years wherever there is a lot of the working condition is very hot as it is in places like India you often refer to cooling of the flow that is going into the compression. And this cooling as we can see now from pure thermodynamics introduces a simple thermodynamic basis which allows the compressor to do the same amount of compression with less work necessary to be supplied by the turbine. And this is what thermodynamics tells us that if you have some method by which you can accomplish a little bit of cooling actual work of compression can be done with less of work supply. There is a process here which is which shows that if you do a lot of cooling which can one call a super cooling you can get away with doing a lot less work to accomplish the same pressurization from 1 to 2 triple prime. So, the pressurization would indeed be achieved but it is possible that you would be arriving at a temperature of a lower value at the end of the compression process even lower than the ideal in which case for a jet engine purpose that may not be a very desirable situation because the flow from the compressor is going to combustion chamber and a super cooled flow going into the combustion chamber would require additional heating in the combustion chamber for the flow to be taken to high temperature. So, super cooling may not be a desirable phenomenon in a typical jet engine operation but a certain amount of cooling as we can see is certainly a desirable phenomenon for more efficient compression process. We can summarize all this by simply saying that the as we have said those diagrams are in terms of linear diagrams and hence the final enthalpy can be written down in terms of the triangle 274 which is shown here in terms of 2 and 7 and 4 and that is the triangle we are approximating it as a triangle and that is the final enthalpy. The initial enthalpy is the triangle 103 and that is shown here in terms of 0, 3 and 1 and that is the triangle with which the flow is entering the system. So, it enters the system through 1 goes out through the system from 2. So, this is your energy at the entry point and this is the energy at the exit point. So, these are the various phenomena that is going on in a typical compression process as shown in a little simplified thermodynamic diagram where the processes are considered to be linear. So, that some of those can be simply referred to as triangles or rectangles and as a result of which those some of those total enthalpy change can now be shown in terms of the area 25642 and that is 25642 and that is the area which is the total enthalpy change in terms of total parameter h 0. So, this is what we learn from simple thermodynamic analysis that you can use of thermodynamics as a matrix try to figure out what is going on in terms of compression process and then see whether you can get your compression process done a little more efficiently a little more effectively. So, that it serves the purpose of the jet engine and brings the jet engine closer to the ideal Brayton cycle which is the matrix on which the jet engine is functioning. So, this is what we have done in today's class the thermodynamics of compression process and we can see that the cooled thermodynamic compression can give us some benefits. In the next class what we will be doing is thermodynamics of turbines. Similar thermodynamic analysis we will then refer to in thermodynamic diagrams and see whether we can learn something from fundamental thermodynamic understanding and make the turbine do work in a more efficient manner to conform to our ideal cycles that we have studied over the last few lectures. So, in the next class we will look at turbines.


First, you swallow these two things in the morning, these two things can do a miracle to your life. It's a great cleanser and also it takes away cellular inflammation. If you reverse this, you will see your day will easily last for twenty hours a day very effortlessly. Very happy to start my day to enjoy this breakfast with you which looks very, very intriguing. Is this how you start your day? Yes, the most important thing when we eat food is that we must understand food is what builds our body on one level, on another level it is the main part of our fuel to run the day. When I say main part of the fuel, there are other aspects of water, air, sunlight. So the entire aspect of eating food is to balance it as to which is more in your life. If you eat certain types of food, seventy percent of your energy requirement is coming from the food that you eat, that means definitely you will sleep for six to eight hours a day. That means your downtime is one-third of your life. One-third of your life is gone without you knowing what happened. So if you change the patterns of eating and there are other aspects also, there is a yogic aspect to it. But if you change, if you eat like this, you will see the volume of food that you need will come down significantly. You don't have to restrain yourself just to this what is there. But after that if you eat also the volume of food that you eat will come down and your ability to get more energy from sunlight, air and water will increase. Right now for as I said for most people seventy percent is from the food. If you reverse this, that thirty to forty percent is from the food, rest is from the other three, then you will see your day will easily last for twenty hours a day very effortlessly and you will live more, that's what it means. Because everybody is thinking of living for more years. But is it not important that you live for more hours per day? Absolutely. But is this it or is there going to be… is this… is there more to your breakfast? Well, there will be usually another pomegranate fruit and if I'm going to be very physically active, let's say I'm going to play a round of golf because eighteen holes I walk, I don't ride carts and things like that. So then maybe I will add some carb to it, maybe an idli or a chapati or something else, either wheat, rice or millet, any of these things we add so that there is enough carb for the physical activity. But if I'm just going into more mental activity and physically I'm not moving around too much, I'm sitting, this is it and maybe I'll drink a glass of something. We have certain very liquidy millet porridge and stuff like that which you can drink like coffee. Okay. I mean it's liquid. Right. So… So I can see these interesting things laid out, if you can explain the significance of these and very interesting these yellow and green balls, what are these? One is a freshly ground neem ball, neem leaf ball, another is a turmeric ball. Like we grow around here itself which is absolutely organic in very rich lands and neem of course comes from the trees, these two things can do a miracle to your life. First you swallow these two things in the morning, wait for ten, fifteen minutes so that it spreads because these two will bring down the inflammatory levels in your stomach lining and also cleans up all the unnecessary bacteria that may be there in case of any parasite, all that it'll be taken care of and also it brings a… it'll bring a certain glow to you. Don't ask me why I'm not glowing. You are always. So I've not eaten anything, you're supposed to have this empty stomach? Yes. Empty stomach and some amount of water, not too much water so that it has enough water to spread. Now, right now what they kept is room temperature, but at home when you do it, you drink tepid water, not hot water. Just one, one of each, is it? You can take all the four. Yeah. Any warnings you want to give me, neem is usually very bitter. No, no, you swallow it like a pill. That's not neem anyway, that's turmeric. Going a bit slow, just swallow, not with water. With water you can swallow, like a tablet. Okay, now neem. Guys, I'm going to have this. It's bitter of Sadhguru. Then see, this is a way of acclimatizing yourself to life. Not bad.  That's a good trick. The water else, I can also see there are some dry fruits. Yeah, this is sprouted methi, which is very important to bring cellular cleansing in the body.  And this is soaked groundnuts, soaked for over six to eight hours. So this soaking is very important and this is very high quality protein because these are organically grown groundnuts. See the, what do you say, the hybrid or even modified things will be this big nuts, they are not the thing to eat. These are original the way they are, the way they should be. So this will take care of that, your protein also. And there are many other enzymes in it which are very, very vital. There was a time when for months I just lived on just groundnut and one banana for the entire day. It, it has all the nourishment you need. And this is of course almonds. This is a little, this is for my international travel because this is not a local thing here. Almond is not a local thing. They are growing, but not very popular. That's a, again a walnut, which is, you know, the benefits of the nuts. It matches with you, you know. Why does it match with me? Because it's nuts. This is sprouted green gram, which is a very high protein again and the green part of it is very important. And it's very important the almond is soaked and this is peeled because these kind of nuts have their own mechanism of self-defense. The moment you soak it in water, now the seed believes that it's going to be planted. We're going to disappoint him, but it believes that it's going to be planted and he's going to sprout and become a big tree and he's got his own dreams. So when you sprout, what he does is, there is a certain carcinogenic chemical within the nut, which comes to the surface just beneath the skin. So that insects will not eat him up, worms and insects will not attack at that time. So you soak it to give him a feeling that he's going to grow and then peel it off. Then you will see that carcinogenic is gone. Otherwise, when you eat an almond, you are eating that carcinogenic part without knowing that you're consuming it. That's insightful. I didn't know about this. And just to talk, I got to wait for 10 minutes before I have all of this, right? No, no, you can try. I can. I will, as we, as we speak, I'll probably begin with the almond. You're not eating the methi. That is bitter too. Oh, is it? And it's very good. Okay. I will try. It's a great cleanser and also it takes away cellular inflammation. Yeah. It's very important. Other any foods that one must avoid each day? What is that? Sabudana. Chicken. Thank you. Thank you very much. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you.


Welcome. This is screenshot updates project with Sheikot Africa. Today we're going to do a test drive of some screenshot updates is our proposal. Miracle and Soma don't seem to be available. So we're going to just go ahead. And the three of us are going to attempt some screenshot updates. So we have a record that they can reference in the recording of different techniques and different experiences doing doing screenshot updates. So first task is we're going to open up the sheet that's linked in the dock. This sheet shows entries that need needs screenshot updates so it says in this column, if there's an entry in column E no change needed we can skip that. But then if there's an entry here in column F with the pull request URL that's one that says hey we know it needs it. And now we need to just assign ourselves to it. So is there one that. Let's see. Here's here's an interesting one Bruno if you want to try something related to SSH keys that's probably an interesting spot in your area or is there another one that the two of you each would say hey I'm interested in that one. It could be blue ocean based to be installation based. And then it's Jenkins screenshot is a pretty common thing to need an update. So maybe you want to do do managing UI themes, what's your preferences. I'll go with it. Okay so Bruno is going to take SSH Kevin which let's see which one did I get that on the right line. I did okay. And then Kevin is there one that looks interesting to you. I can do the manage Jenkins screenshot. Okay so script approval and this one's a good one because sometimes I found cases where I needed a screenshot and I could do it in two places using the same exact picture. Good. So let's let's get started then alright and I think I want to take. I think I want to take pipeline running pipelines. Alright so now now what you do is is open up your page. I'm going to open my page. Now I need to find the screenshot. Okay, here it is my first screenshot. This one talks about restart from stage and those icons are already not no longer the correct icon so I'm going to create a I'm going to get a Jenkins weekly running. And I've got one already at weekly dot ci dot Jenkins that IO. And let's see if it has. I'm logging in with my Jenkins account, and it does not have any jobs to find okay so I need to use a different one so I'm going to instead switch to this other machine that I have that is running a weekly version. It's current, and it does have some jobs. So if either of the two of you need an account on this, this one I am happy to give you one. Otherwise you can just start your own Jenkins locally actually you'll probably yeah, either is fine you let me know. Now this is showing how to restart from the classic UI. So what I need is I need a job that runs in a pipeline, like the get client plug in multi branch. And here's one. Okay, and they want me to show restart from stage. I need to go all the way there inside the job and find the restart from stage. Nope, it's not there. Okay, so classic UI and click restart from stage. Okay. Okay, so now I've got to go find out why my job does not have a restart from stage. I think it's linked to your job is a feature that still exists in the current weekly Jenkins base. That's a good question so now it's maybe time to research to see maybe I'm missing a plug in. Maybe I'm missing something that doesn't doesn't even give me the facility so. Okay, so here Oh, it takes me right to this page. Okay, it's a day I need to have a declarative pipeline. Okay, I should have read that read the instructions more carefully. The problem that I had was the pipeline I was look I was viewing was not declarative so the easiest thing to do is create a new one. A new declarative pipeline, and that makes sense in that declarative pipelines evaluate the complete definition of the pipeline before they start it. Scripted pipelines evaluate the pipeline definition while executing, and that difference may make it impossible to do a restart from stage. So I'm going to create a new declarative pipeline. I'm going to create declarative pipeline for a restart from stage demonstration. Okay, so we need a pipeline script. Let's go with hello world for now and first we're going to do check out. I'm just going to have something that does a checkout step. Then I want to add another stage so that I have I need at least two stages in order to start from stage so maybe we're going to say something like Java doc is a stage. And what it does is maven Java doc colon Java doc. And now I have to say, label, not windows because I'm using an SH step. So let's try that build now. And what does blue ocean show us. So blue ocean shows to check out and then Java doc and Java doc failed. Interesting. That's a very interesting failure mode. Okay, maybe we need to declare where it's supposed to run. Let's see where it actually ran. That's a good machine. And so why would it say that. Okay, this is why we have restart from stage we're going to configure it and fix my mistake whatever it was. Okay, so it may be that I need to say, maven minus version, so that I know what maven version is trying to run. It says it's running Java 17 maven 3.6 so it's running an ancient maven version, and a thoroughly modern but not completely modern Java version so I need to give some more definition to this to get the correct versions of the tools that I need. Okay, so, configure. And now what if we said, see using pipeline syntax, it should be able to help me find the tools directives, actually I need declarative so I've got to have this one and it needs tools, and I need to add maven. I need to use maven latest, and I would like to add JDK, and I would like to use Java 11. So this is the syntax I need to use. And I put it right here. In case you can't tell screenshot updates is a big chunk of it is not just about taking the screenshot it's getting to the place where we can duplicate the condition. And the that makes it extra fun for our she code Africa participants because they then learn more about Jenkins and more about software development. As a result of their working on. Okay, this is much better notice it now says Apache Maven 3.8.4. This Java version now that's a little out of date it should be 11.0.15 but that's much, much better. And it's a success. And it is so now I should be able to find restart from stage. And there it is restart from stage. Well, I would like to restart from stage Java doc. But looks after the job finishes. Interesting that it's taking 12 seconds to change and change to use a new age. No. Okay, so. Alright so notice that the first stage is empty because it didn't do it. And if we look at three. Let's see let's look at stages here. And now if I look at pipeline steps. Yeah, okay this shows allocate a node start the stage install the tool as defined by declarative. And it skips the checkout stage and goes right to Java doc now that is assuming that that workspace is still available had this been an ephemeral workspace. That would have just failed because without a checkout step you can't generate Java doc. All right now back to the real task which was capture this image. Okay, so now there it is shows back to project status changes console output. This is the right page good. Okay. Okay, so now I can just do my screen capture. Yeah, exactly. Okay, where's my a little wider to get the icon back that will let me take the screenshot. Come on. There we go. Okay. screenshot. All right now we do a little bit of edit crop. This one back to project restart from stage okay I am impressed that there are not more changes than that. So here we see status changes. Status changes console output. Yeah, okay good so this is. Now, I'm ready to download that. And then I need to decode what image that actually is so I'm going to open that image in a new tab and it's called restart stages sidebar dot PNG. So I'm going to rename that file. It was dropped into my downloads directory as real start stages sidebar PNG. Okay, so I'm re I've got the correct file name and now I need to upload that to my place where I actually do the development work. And the reason here is I'm a Windows user, but documentation development on Windows is almost infeasible it's so painful. And in the future it will be easier but for right now it's just not and all of my, my worrying about it doesn't matter it's just easier to do it on Linux or Mac OS. Okay, so restart stages sidebar PNG has been uploaded. Okay, so check out a new branch. Let's make this text big enough to read. All right, so get check out minus B. See it was update restart from stage screenshot. Right. And that should be synced with the master branch, it is okay. Wrong command, I need. I need less files star and I need to find that file name it was that one restart stages sidebar. There it is okay so I'm going to move the temporarily uploaded loaded one to that location. Okay, and now I need to optimize the image and I've got an optimizer script that I use. It is right exactly it's also stored in the document and so it saved 10 k bytes of a file that was approaching 30 case so a one third savings that's worth it. So here we go. There is the image. Let's do a make run to then be able to what look at that image and see how it looks in context. So what I did was I generated the screenshot, put it into my into my source repository into my working directory, optimized it and added it so that now it's ready to be used. And now let's see how it looks. You can see how it looks right here so I look at my computer on port 4242 is where that is and this is. What was the page again it was run pipeline running pipelines documentation pipeline running pipelines there. Okay, so here is a very different screenshot. So except. Okay, I made a mistake. Notice where the highlight is the highlight is over the word status and it's yes status and it should have been. And was it that way originally. No, but I should hover over status for the better for the better experience so that means I've got to be a little smarter about gathering the screenshot. Okay, so let's do that. Let's do it for play a game. Interesting, except it's got status highlighted. What do you wonder what. Oh, that's what I should have done. Okay, so clearly, it would have been much better if I'd done it more wisely so let's let's do this we need to redo the screenshot. Okay, so redo the screenshot. No, not that one redo the screenshot. Okay, edit crop. Sorry that the two of you get to watch me make mistakes but hey, part of part of this is in fact making mistakes. Okay, and then. And now how far down the list did they go they stopped at pipeline steps. So, if I go up a couple here. Okay, that's better. Now we're back to upload the file. So rename this one temporarily. Okay, now back to do my upload. And now over here. Okay, now let's do that make again and see if it looks right. And then this make run, etc, all from get pod.io as well. It doesn't have to be done locally. There are ways to upload files to to get pod. So, so that could have been done as well I just for me it's easier to use the setup that I have right now. Okay, so now there it is okay restart from stage is now correctly shown as the, as the one to choose. And good here's another one that I didn't capture the next screenshot, just a minute. That is actually close enough to not need a change. Yep, it looks the same. It's pretty close right. Good. Okay, so I think. So now I think I'm ready to submit a poll request here. So first, I've got update. Restart from stage screenshot. Assure that the highlight is correct is correct. And good. Alright ghpr create. So it says where should I push it I want to push it to my, my copy. That title is good and I want to edit. Submit it. And so now what I'm going to do is go back to that sheet and put this poll request into the into the worksheet. So that, let's see where was mine here it was. Okay, or request is submitted done. Excuse my being the only one talking here so Kevin or Bruno anything you wanted to ask or any questions or things that you've encountered on your experience. I was looking at Marcus is it says that the managed Jenkins screenshot needs to be updated. The only thing is when I'm in Jenkins I'm not seeing that option and I'm not sure if I if it's because I don't have projects currently running or if it what might be holding it back in this case. Good so let's are you okay sharing your, your screen Kevin and we'll let's look at it together and let's get you there. Great. I'm going to stop my sharing. So when you open manage Jenkins it doesn't show a and an in process. Okay one you're running dark theme. Okay, that's that's interesting. Good. Okay. So, so you're using ci dot Jenkins that IO and it doesn't give you access to manage Jenkins. So that's, that's not a shock, because we don't want you to be able to manage this. This instance that is huge so right do you have, do you have a local instance. On the outside of my clone repository, or, like, okay, maybe I'm just a little bit disconnected on this instance, if anything. No, so, so are you running a Jenkins server in on your own computer locally, most people don't and so it's okay to say hey no I'm not. Okay good so what I'm going to do is I'm going to paste a URL where you can get access to one. Okay, that is a current weekly and then. Alright so if you'll go here so into the chat. Home dot mark weight net has one connect there. But I don't know that you'll have an account there so let me look just to be to see shipping users. Not yet so you can go ahead and stop sharing your screen, because I'm going to send you a single use URL for a password that you can use so k martins 27 is that correct. Okay, alright, generate a secure password lovely choice. Generate secure password. And you're welcome to change this password to whatever you'd like, but it makes it easier for me if I just generate these things. Let's see k martins. Okay user has been created. Okay, so now what I'm going to do is I'm going to generate a single use URL. And I'll paste that password into that single use URL, then I'll email you the, the URL you click it, and that's the password you use to. Let's see so I'm going to put that I think I'm just going to message it to you through a private channel. Here it comes. Alright so you should see it in slack. And you can click on that URL and it will open up the page, you get it can be clicked only once. Second clicks later clicks will no longer and then you can log in as k martins 27 with that password. Okay, great. Mark, would you mind doing the same thing for me, please? Yeah, thank you. I have Jenkins instance running on my Windows PC. The thing is, I can't do any modification like it's Docker container running. I didn't manage to run Jenkins, I directly under Windows without without Docker, you know, the, the key clon doesn't work for me, but it works when I'm on the linux. I have some sound problems with linux, I can't tell, there's a meeting with linux, I'm stuck for the time being. No problem, what username would you like Bruno? Podang, if you don't mind. Okay, that's great. Could you place that to me in chat so that I've got it? Yeah, for sure. Because then it's easy for me. And you could put it, let's see, so have you, you've posted it to a Slack message, or given that this is public, you can put it in the chat here in, in, oh, got it, I see it. Got it. Okay, good. All right, so, and yet another password. Just a moment. Okay. So, and now we're going to create a single use URL again, so single use. And Kevin, were you able to log in? Yes, I was able to log in, no problem, Mark, I'm actually in the stream where I wanted to be in the first place. Oh, good. Okay. All right. So, sorry Bruno I'm apparently not as fluent with doing this as I thought I should be encrypt the message copy the link. So, coming to you on a private channel is the link to the single use single use URL. Okay, if I learned how to copy. Okay. So that that single use URL and you should be able to log into that server. Cool. Let me try I got the password. And just so you're clear you both have administrator permission on that and if you were to destroy it accidentally, no problem. It is intentionally if it were destroyed, I can recover so don't worry. Don't don't be shy about doing both things it would be fun great if if you destroy it if you were to tell me mark I destroyed it. If that doesn't happen if I detect and spend destroyed. I'll replace it, etc. It's not a big deal. And we leave and log on. Thank you. So you're logged in. Okay, great. Yeah. All right. And Kevin were you you said you were able to get to the manage Jenkins screen. Yes. Yeah, I found the screen and the menu and the piece that was actually called out in the outdated screenshots spreadsheet. Oh good. Oh yeah so it's got in process script approval. Now now this one this one has a complication that it needs some annotation. Okay, because it needs that red box around it and the original screenshot is particularly ugly because the red box cuts off prematurely truncates text. So you may want to set your screen size to be more reasonable. This is a really old screenshot because it doesn't even show things in the multi column layout. Correct. Yeah, and I just noticed that too. And so I was actually curious, should I just share my screen mark while we're sure. Yes please do it cool. Okay. And my screen is visible. And it's far too wide for screenshots so you're going to have to make this this webpage much much narrower for columns I don't think I've ever seen four columns the most I ever got three so obviously you have very good eyes and a and a nice wide screen. I was gonna say I think my monitor is just a little bit bigger I don't think I have my eyes or any better. Okay. So yeah, so in this case, let's say I do just kind of take it away. True. Should I make it so just one column like this or for me for me I like it having to because if you look at the original screenshot the original screenshot shows multiple things on the page. And so for me, having at least two columns was nice, but two columns, not more than two columns is good because then it, it keeps people from being miss from misunderstanding that, oh, what's this text is too small to read in the screenshot. Right, right. Okay, cool. And I figured that with the page itself talking about manage Jenkins that would want to be highlighted like you had in your page. And this is the area that they specifically call out in the outdated note. So would it be the idea is just highlight it like this like we had previously and then grab this screenshot or should I actually go into it and then grab the screenshot. And the original screenshot, you would you were whoops the way you had it hovered right there that for me is the preferred and then I would crop the image to only include the security section, because because if you look at the original screenshot the original screenshot doesn't provide any context that you're in the manage Jenkins page. It only shows here is exactly this tiny little subset. For me, having the highlight there, the darker color may mean we don't have to annotate the screenshot at all now because the darker color gives an indication that nice darker background. So can you think we will be sorry, go ahead Bruno. Oh, sorry. Do you think you will be able to screenshot with the hash over, you know, there's a great background and gets rid of the pointer, the mouse sign on it. Okay, so right now I don't think that I'll be able to, but only because I'm screen sharing, and it might be a little different. Oh, typically on the map. I actually there's a keyboard shortcut that I can click on and it basically allows me to just drag over a section of screen and screenshot whatever I want, and it's it holds on to what's in play at the moment. So if I were to do it while I have this hover over it would actually hold on to the highlight when I go to screenshot. Perfect, so stop sharing your screen and take the screenshot that sounds great. So somebody who actually knows how to drive a Mac I don't know how to drive. That's one of the things I don't want to learn. That's fair. I think I think I do like to take the political statement there that's very good I like that that's great. Yeah, I'm afraid I've not had the patience yet to learn Mac so thank you for being willing to be our, our tip of the spear on this experience. Okay, can you so can you show us the screenshot how does it. Yeah, how does it look. So let me put up right here, and I'll just move it on to this side of screen so that it's visible. So this is actually the screenshot. So and that that has okay now bring up bring up if you can in the on that left hand, the old page so we can see for comparison because I think that. Yeah, see that that is, that is a much better screenshot and you didn't have to do the red box thing. Right, because it already highlights things for us in a box. So it's already self contained. Excellent. Yeah, this is great. Okay, so now the challenge is, how do you get that into the right place and how do you find it. So, right now, so I've, I'm in my text editor. And I have the script approval doc which is where the screenshot is coming from if I'm not mistaken. Okay. Yeah, script approval. So I'm here, and then I just need to change the existing screenshot with what my screenshot would be in this case. Right, yeah so you want to update the existing file, and I assume it's that managing slash manage dash. So could you back to the web page. Yeah. So to the original web page for the for the documentation the one that we started from. Yeah, right click over that. And open image in new tab, or oh yeah okay that's a good way to do it looking at source code. Yep, that's it so manage process script approval is the image we need. Okay, so now is this one here. Right. And then let me just rename my file real quickly so that's a little bit easier. So now I've got that all squared away it's got a normal name. Copy that. And so I would actually it should be in a folder of some sort correct mark just to have the directory there. Well yeah so what you want to do is you want to find the existing copy of manage in process script approval and replace it. So, so back to your editor where you were. Yeah. And now we want to find that image and managing manage in process. Okay, why don't I see it already in the list on the left hand side because that's a file explorer list on the left right. Yes. Oh, I know why. If you look up at the top. It's on the very top of the page online 12. It says, Oh, images to colon dot slash resources so go up one level to book slash resources. Okay. Yeah, book slash resources slash managing. And now there should be the picture for. There it is okay good you found it now that's the one we want to replace so copy over the top of that file with this new image. Okay. So, okay, then. So then I would want to add a new file into the managing folder. Yeah, and it's it's you want to you want to file of the, this is where it gets, I'm not sure how to do it from the, the Explorer view what you want to do is we want to take the, the new picture you created. Yeah, we want it to have the exact same name as that file because we want it to override it. Oh, okay, got it. Okay. And the reason for the override is because we don't want to change the, the a doc source file, and because the old screenshot is no longer useful let's, let's throw it away and replace it with a new one. Got it. Okay. So then, now are you in a, I'm not sure what kind of a tool you're in here is this a file explorer a finder kind of thing, or a, an ID kind of thing. Yeah, so this is Adam. Oh, it's Adam. Okay. Yes. So, so I'm sure there's a way in Adam to move files around. I just don't know how to do it. So, so. Yeah, and then as far as like, figuring that out right now goes and we don't have to necessarily do that. But what would be, would it be easier for me to do it through terminal mark and just I don't mind doing it from the command line we can do it and then go figure it out later. So, so from the command line get space LS dash files space. Yeah, so you need more more commands on the LS dash files. Yep. And for your for your own speed and sanity the upwards arrow usually will recall your last command space dash dash. An asterisk. And then the name of that file it was like something I script. Yeah in process and another asterisk so it says show me anything that's got that in its name. Okay. So let me actually put that in the, the right folder. Well but but you're in the you're in the parent of all of these things, right. So the screenshot however is saved to my desktop. And it's okay where it is right now we're trying to find the destination file. So there must be something wrong with the file name there in the in the find the destination process so what's its name again it was no it's really in process. Manage in process. Okay let me do some checking on my side because I expected that to be easily found so you did get LS files. dash dash asterisk in process. Close the asterisk. Yeah I definitely have a match so I am. No, no you don't want to take the space away that space was exactly correct. And this, and that one should show you a lot hit enter. No, okay. Oh, wait a sec ZSH. Interesting. What is ZSH doing to us here. Okay, so try putting a backslash ahead of the asterisk. I've never. So, so recall, yeah, that's a forward slash the other direction. And we want it right before the asterisk rather than right after. Okay. Interesting ZSH no matches. Okay, let's try a cheat type in bash BSH enter. And now PWD let's see where we are. Good okay so now do that same get LS files command. So get space LS dash files. Yeah, exactly. Space dash dash space asterisk in process. Close the asterisk enter. Okay, now that's better. I don't know why ZSH did not do that I can't explain what ZSH was doing with with that matching but it was doing something unexpected. Okay, so now we want to move from your home directory so MV tilde slash. Yeah, the tilde character on my keyboard is right above the key right above the tab character. There we go slash. I am. Is there a space or should it just be no space, no space. And now press the tab key. Is home phone in Mac OS. I mean, you know, Good question. Yeah. So, Kevin, back up all the way and let's do LS of tilde to see what it is what it thinks it is. See if we can find that file. Okay, LS space and then the tilde character. Okay. And I don't see the maybe desktop maybe. Oh, all right. Yeah, you said it was on the desktop didn't you. Yeah, yeah. Of course you did so LS tilde slash desktop. Okay. It's forward slash or a backlash. That was that's the correct slash forward slash. So capital D for desktop. And now if you hit tab, it should complete it. Yeah, now enter. Yep. screenshot. Okay, so in the screenshots folder there. The screenshots and then there is this. This file here. This is the file here. This is another. Oh, got it. Okay, good. So, so we need to, we need to do an MV. Space tilde slash desktop slash. In process and so slash I am P and then hit the tab key character. Yeah, because you will have. Oh, yes. Right. And then. Okay. And now if you can copy and paste from the. The first line of the get LS files output up above where it says content slash doc. No, no, you scroll too far. So. You see the LS files. It's about three lines below your current cursor. There's some more. Yep. Yeah. A few lines more. Whoa, right there. We want, we want the one right below where I see your cursor right now that one. Yes, paste that. And hit enter. Now if you do a get status. It should tell us there's a changed file. Yep. It does. Good. Okay. Now let's do the, let's see. Do you have the optimized thing set up locally for yourself? Probably not. I'm not sure what that is. I thought my head mark. Yeah. So let's given that we're almost out of time here. Let's do, let's do a get ad. Yes. Get ad space. That says add everything. So get ad space. Dot. Good. Okay.  And these will all become second nature. So, so this is saying I want to start a commit and I'm going to give you a second. Sorry, I was doing myself a V as in verbose. Oh, VVV. Yeah. My initiation. Mark. Yes. I guess the GH command will do it for us, but we didn't create a branch. Oh, you're right. We didn't. Okay. Stop what you're doing. Good point. Thank you very much, Brunel. So back to Adam. You can go back to Adam and empty out that buffer. So delete all the lines in it. Everything. that too. If you if quitting Adam is fine. So back to the terminal window. Okay, commit. Yeah. So Bruno's right. We need a branch. So check out minus B. Actually, and before we get a branch, let's be sure that your current copy is up to date. No sense in submitting a pull request to something that's out of date. So do you have GH install GH space repo space sync. You do very good. Okay. And we are currently on the master branch. Is there a get space branch? Okay, we're not. So get space check out space master. Okay, now do the get status and let's prove that we've only got one file changed. Good. All right. So now get check out minus B and space and then a branch name. So this is let's see what is it update manage Jenkins screenshot update dash manage. No spaces. Sorry. Get branch names can have spaces, but you won't like the experience. Right. Okay.  And back to Adam. Where is so you have to bring up your Adam editor somewhere. It's it appeared. Oh, there it is. Good. So very first line needs to be a brief description 50 characters less typically describing what we did. So on line one put in update the managed Jenkins screenshot. And now if you want to put more lines in, you could for this one, it's probably simple enough to just save that file. Okay. And now you can exit Adam. I think that will tell it to continue. There's probably a way not have not to have to quit Adam. They did it. Okay. So now you're going to do a GH space PR space create. And that's where you want to push it. So you can just push enter. And the title is great. So that's good by pressing enter. It says I accept the title it proposed as a default. And you don't need any other body. So just press enter to skip. And now it's saying shall I submit you say yes, I want to submit. Okay. Now copy that URL. Yep. Into the sheet that we were using to do tracking. Yep. Yeah, and just replace the text actually replace that text because now we've got the real poll request hit enter and we're done. Excellent. Thank you, Kevin. Very much. I appreciate all the help. Thank you, Bruno, for being in there. All right. I think we're set. We just run out of time. So any other questions before we call it done? Sure. If we have cleans and master branch before leaving. Good question. Yeah. Okay. Good. Good point. So and by clean, you mean run and get clean? Oh, something on those line just to get rid of the PNG that we put in the master branch we see is not supposed to be there. Oh, no, actually, it didn't end up there because we didn't commit it. So that's a good one, Kevin. Okay. Right. Because because we didn't commit it, we committed it on a branch. And because we committed it on a branch, it never arrived on the master branch. It will arrive on the master branch after we merge. Good question. Bye, sorry. All right. Anything else? Not as I think of. We could add in a step by having a local copy to see what it gives in the context, but it was not possible on Kevin's machine. And it's not possible on my Okay. Well, and that's that's a good one. We could have also done that with Gitpod or or another another step, right? Would have been, okay, let's do it with Gitpod instead of doing it from your local desktop, because if the local desktop isn't for whatever reason able to do the Docker commands or the whatever, Gitpod could let us do it. Good. All right. We've got things to do in future meetings. Yes, for sure. Except if you don't mind that I tried by myself, you know, the line that I assigned to my chef, maybe I should try it and just log if I'm running into problems. Absolutely. Or ask questions in the Slack channel if you encounter a problem. Exactly. Because then they can see the questions and realize, oh, okay, here's the questions being asked. I may have the same problem. Cool. We'll do that. But hopefully everything will run smoothly. Actually, if it doesn't run smoothly, all the better because problems you encounter are the same problems other people encounter. So we appreciate you being a volunteer. Okay. Fine. Thank you. All right. Thanks. Recording should be available within about 24 hours. I'll post it to the community forum. Thanks, both of you. Thank you.


Hello! Welcome to the session on Conversion of Contacts Free Grammar to Chomsky Normal Form. At the end of this session, students will be able to convert a Contacts Free Grammar to Chomsky Normal Form. We convert the given grammar into Chomsky Normal Form i.e. producing a x format. Now in this case, initially we start with the grammar g consisting of format g is equal to vtps that is non-terminal terminals production and start. Next, we are eliminating useless variables that cannot be become terminals, then eliminate useless variables that cannot be reached, then elimination of null production, elimination of unit production, then conversion of grammar to Chomsky Normal Form. Now in this given grammar, s producing a a c d, a producing a a b or null, c producing a c or a d producing a d a or b d b or null. In this first step, we will check whether any useless production is present. Here s is starting a a c d, a c is having value, c is having terminal value, d is having terminal value. So, here there is no useless production which is not having terminal value. Now next, we will check useless variable that cannot be reached. Now here s is having values, c is having values and d is also having values. So, s is reaching to every variable. So, there is no useless variable that cannot be reached. So, we will move to the next step. Here we will check null production and eliminate if any present. Here in this production, a and d are having null productions. So, here we can see that l is producing null, d is producing null. Now these are nullable variables, a and d are nullable variables. Now in this a variable after null replacement, we will check what are the changes will be there. In this case, this is the new grammar we are defining. Now here a a c d only single variable it was defining first. Now when we are putting null at that time a will be null. So, your value will be a c d. Next a will be null. So, your value will be again a c d is there. Then next we will check for d we are putting the value of d is null. So, we are getting a a c. Next when we are putting both a and a null value we are getting c d and when a and d both value we are putting null only c remains. So, that value is c. So, next a is there. Here there is no value for that. So, only a is there which is having null value. So, we are putting here a is null. So, it will get a b value. In this case a c is there as it is there is no use of capital A and capital D and in the d value we are putting here a and d. So, only d is there. So, when we are putting d as a null. So, we are getting a a and here b b. So, here we are producing new grammar by with using that elimination of null variables. Next we are having the elimination of unit production. Here we need to search unit production in the given grammar. As we have seen we can check the unit production here no here no. Here c c is the unit production in the start symbol s. So, the and that is the single unit production nowhere other places we are finding any unit production. Now by putting the value of c wherever the c is present we will get that new grammar. Now here c value is ac and a. So, we are putting here in the s instead of c keeping the value ac and a. So, here we are eliminating any unit production that is c. Next now once the format is clear now we can convert c and f format that is a defining or a producing ax. Now here restricting right side of the production to single terminal or string of two or more variables. Now steps in this we will add x a and x b instead of single terminal wherever it is present. Now wherever single terminal a is there we are not replacing, but wherever this a b a b these terminals are there we are putting x a value for a and x b value for b. Now accordingly we will see that new grammar is there. So, a acd here we found first single a with non-terminal. So, it is replaced by x c. Next in the a x a is replaced here b is replaced as x b. So, here again x a and x b here again x a this is a single terminal. So, next whatever a is replaced by x a then x a like this all b is x b x b x a x a and x b x b. So, this is the new grammar we are producing. Now one more step here it is whatever big or long productions are there we have to short that productions. Now I will take one example how to short that productions here a a cd a acd has to be converted into the short. So, directly I am keeping s producing a t 1, t 1 is what t 1 is equal to a t 2 and t 2 is cd like that a cd is converted into s producing a u 1 a ac is producing s a v 1 and like this would the next all the productions are shown over here and they all are shortened and thus we have converted the cfg into cnf. There is one question for you remove the null production from the following grammar here s is having this value and a is having this value. If you find any null production here then remove it after elimination of the null production we are getting the new value. So, here a is having null value. So, we are putting wherever the a values are there and we are keeping the null values. So, here first here we are putting null value. So, a b c here b ac then both a is as a null value. So, b c value is there. So, these are the new values if any duplicate then you can remove it and you can write that new value. Thank you.