So, let us get started with may be one question, Amal Jyothi college Kerala any questions.  Now the room will emit some radiations and it will be absorbed by the man, now after that the, suppose instead of a man suppose there is an object there, now after absorption it will transmit some amount of radiation, now it will go it is going, so absorbed radiation it is going to be transmitted, it is going to be transmitted and it is going to be hitting on the same surface itself. So, in that concept do we want to take the transmitted amount of radiation. See the question is actually this is the question is if I put a body inside a furnace and there is an interaction of the body and the wall and do we have to take the transmissivity also into account. I think you will have to, we will be answering this question, we will be in fact solving a problem on this, so you will have to wait until I solve, the point is there is view factor which is taken into account, I have to take into account the irradiation and also the emission, so this is the point, but anyway you will be able to appreciate this when we get to the, when we complete the basics of radiation, so I am going to get started where we stopped, see where we said that the black body radiation is the radiation depends on the temperature of the material, wavelength of the emission, surface roughness and surface roughness, but not considering the wavelength, temperature and the surface roughness, if I define an ideal body that is the black body which absorbs what is a black body, it has to satisfy three conditions, it should absorb all the energy which is incident on it and it should emit maximum amount of energy, no one should be able to emit more than the black body and black body has no preference for direction, that is it is a diffuse emitter that is black body is this, this is not black body, this is black body, so it is a diffuse emitter under these conditions, so we can say that that is the black body and all real bodies are going to have a emissive power lower than that of the black body, so now we have Stefan Boltzmann law where in which we said that E b equal to sigma t to the power of 4, where sigma is 5.67 into 10 to the power of minus 8 watts per meter square Kelvin to the power of 4 and then this was contributed by Stefan and Boltzmann and Stefan never left the university, he was always in his own place, he never left the university, in fact he never went home also, but Boltzmann was a peripatitic traveler that is he used to travel all over the place and unfortunate the bad news is that Boltzmann died of suicide that is he committed suicide perhaps he thought that he did not get the recognition as much he deserved during his lifetime, so it is a bad news maybe Boltzmann would have been alive for few more years few more laws would have come out anyway, so there is we said that a cavity can be imagined as a perfect black body because it is a multiple reflections because of multiple reflections it is going to absorb everything and at the same time it is going to emit everything. Now the spectral emissive power of a black body is given by Planck's distribution as you can see that it is a function of lambda and T and rest are all constants, so and I know the black body is a diffuse emitter, so if I calculate emissive power instead of intensity of radiation pi I lambda, B lambda , T is I if I substitute the Planck's distribution I am going to end up with C1 upon lambda to the power of 5 exponential of C2 upon lambda T minus 1, so C1 and C2 are constants. So now if I plot this spectral emissive power I find that this is the spectral emissive power and this is the wavelength plotted for different temperatures, so what I can see here is that the emissive power increases and decreases and there is always a maxima at a particular wavelength and that maxima at any particular temperature can be computed by Wien's displacement law that is lambda maximum into T equal to 2897.8, so that is Wien's displacement law and also it states that any wavelength below 0.08 micrometer and near about 2000 to 3000 micrometer there is no contribution of any other waves other than these wavelengths contribution towards thermal energy that is the important point we need to recognize or realize or emphasize and one important point professor Arun emphasized is that area under this curve represents the total emissive power of any body at of a black body at that temperature at that temperature covering complete thermal radiation wavelengths. So is professor Wien and this is the Stefan Boltzmann law if I integrate this with respect to lambda covering all lambdas I am going to get sigma T to the power of 4 and that is how I end up getting sigma equal to 5.67 into 10 to the power of minus 8 Watt square meter squared Kelvin to the power of 4, so intensity of the black body is equal to EB by pi that is another way of looking at it. Now the question is that is where we stopped in the law just before signing off for lunch, so now the question is now I want to find an emissive power in a particular band of wavelength it is not from 0 to infinity let us say I want it from lambda 1 to lambda 2 that is 3 micrometer to 5 micrometer or 7 micrometer to 12 micrometer if I am interested in only band emission that is what is this band emission what is the band emission means I am interested in a particular band how do I get that band emission, so that is defined as a fraction fraction of the total emission of from a black body that is in a certain wavelength interval that is fraction so what is that fraction so that let us say I define it as 0 to lambda E lambda B D lambda upon 0 to infinity E lambda B D lambda what is this denominator what is this denominator total emissivity that is total emissivity complete spectrum it is covering the complete spectrum whose spectrum it is covering black bodies so it is black bodies of course even in the numerator it is black body only for a black body if I cover complete spectrum what is this E lambda comma B D lambda just now we have integrated this and found that that is nothing but sigma T to the power of 4 so the denominator turns out to be sigma T to the power of 4 but then what is the numerator that is between that is the emissive power in a particular wavelength what is that particular wavelength band 0 to lambda so this fraction between 0 to lambda and 0 to infinity is the fraction that fraction is called 0 F 0 to lambda you see capital F means fraction 0 to lambda means I am interested in the emissive power only between 0 to lambda compared to the emissive power of complete spectrum which spectrum thermal spectrum that is the spectrum over which the thermal radiation contribution is inherently there now I will do some algebra so what I am doing here is lambda T equal to m let me call this as lambda T equal to m so if I differentiate this I get D lambda into T this remember all this I am doing at a particular temperature temperature is fixed D lambda into T equal to D m so D lambda equal to D m upon T so when lambda equal to 0 m is 0 when lambda equal to lambda m is lambda T so if I substitute that E lambda comma B D lambda T what will happen D lambda becomes now D lambda T upon T so T is there in the denominator and you have now the limits have changed from 0 to lambda to 0 to lambda T so 0 to lambda T E lambda comma B D lambda of T upon sigma T to the power of 5 what is E lambda comma B lambda comma T that is pi I lambda comma B lambda comma what is pi what is this I intensity of radiation that is Planck's distribution that is C1 upon lambda to the power of 5 exponential of C2 upon lambda T minus 1 is that okay you see 1 by pi is there that pi as vanish okay so I get 0 to lambda T C1 D of lambda T upon sigma upon sigma where did the sigma come from where did the sigma come from yes it is there in see what am I doing I am substituting this in the above equation so if I substitute this in this equation what am I getting see E lambda comma B is C1 all this blah blah blah and in the denominator I have sigma T to the power of 5 but here lambda to the power of 5 is sitting so lambda and T I will combine and make it as lambda T to the power of 5 so what is this whole of this which is there in the integral it is a function of what lambda T so fraction fraction of the total emission from a black body we have shown that it can be represented as a function of lambda T why are we doing this because every time we do not want to calculate this fraction once we want to calculate this fraction for different lambda T and keep it and use that table again and again that is what we are going to do so again the same thing I am not done this font is big that is all F0 lambda is 0 lambda T C1 D lambda T upon sigma lambda T to the power of 4 exponential of C2 upon lambda T minus 1 F of lambda T if I have to understand what is this fraction this is the fraction this is the fraction of the emissive power compared to the total emissive power I am looking for is that ok and that fraction happens to be a function of lambda T that is F lambda T ok so now this has been integrated because I know C1 C2 if I choose a lambda T I should be able to get the I should be able to integrate this I can use either Simpson's one third rule or trapezoidal rule and integrate this you can also do this integration using excel sheet simple excel sheet ok so that is for 0 to lambda T now what if I have to find a fraction from lambda 1 to lambda 2 that is let me show that pictorially that means earlier I was trying to find this fraction what if if I want to find the fraction of emission between lambda 1 and lambda 2 that is the area under the curve which has been shown that is it is emissive power from 0 to lambda 2 minus of emissive power 0 to lambda 1 upon sigma T to the power of 4 same thing whatever we did for 0 to lambda I can do the same thing and show that fraction of lambda fraction of the total emission between lambda 1 to lambda 2 is equal to fraction between 0 to lambda 2 minus fraction of 0 to lambda 1 ok is that ok similarly if I have to find the intensity of radiation I lambda B lambda T upon sigma T to the power of 4 this is given by this so I can compute this ratio also by computing this ok so all these are plugged in here for a given lambda T I get the fraction f of 0 f of 0 comma lambda and this is the ratio that is this ratio I lambda B lambda comma T sigma T to the power of 5 otherwise every time I have to compute instead of computing that intensity of radiation has been given and this is given as a ratio this intensity whatever I get upon I lambda comma B at lambda maximum comma that is intensity of the radiation of the black body at a given temperature at maximum at a wavelength at which the emissive power is maximum so that is what is this ratio. Now let us just quickly solve a problem so that we understand this concept of band emission ok consider a large large isothermal enclosure that is maintained at a uniform temperature of 2000 Kelvin. Calculate the emissive power of the radiation that emerges from a small aperture on the enclosure surface if you see the figure this is the enclosure and this is the small object and the enclosure is sitting at 2000 Kelvin. Now what is the calculate the emissive power of the radiation that emerges from the small aperture on the enclosure surface how will I calculate this what is the emissive power there is a small object there is a small object ok so it has to undergo through multiple reflections so the it does not matter what is the emissive emissivity of the small object if the small object inside a large cavity can be considered as a black body. So if I do that so the emissive power is sigma T to the power of 4 sorry sorry what is that question as calculate the emissive power of the radiation that emerges from a small aperture on the enclosure surface who is emitting this the enclosure surface is emitting so enclosure surface is at what temperature 2000 whatever is emitting from the surface only has to get out through the aperture so the emitting thing what is the emitting thing that is sigma T to the power of 4 so that is what has been substituted and we are getting 900 kilo watts per meter square ok. So now what is the next part this is the easiest part what is the next part what is the wavelength lambda 1 below which 10 percent of the emission is concentrated that means what what is the fraction or what is the wavelength lambda 1 below which 10 percent of the emission is concentrated what is this 10 percent that means f 0 lambda 1 is 0.1 what what is the wavelength at which f of 0 lambda 1 is 0.1 that is the question is that ok ma'am is that ok fine. So you get f of 0 lambda 1 is 0.1 so now how do I get that lambda 1 how do I get lambda 1 f of 0 lambda I have to just go back I have to just go back and see this table what is this table showing what is this table showing lambda t and f 0 lambda for this problem for now these two columns are not important for this what is given f 0 lambda has been given to be 0.1 at what lambda t it is equal to 0.1 somewhere between 2000 and 2200 little below 2200 if I am right it is 2198 if I interpolate that if I am right no 2195 2198 is that maximum Wien's displacement sorry this problem I get lambda 1 t equal to 2195 micrometer kelvin. So how do I get this lambda 1 now what is temperature temperature is given to be 2000 kelvin so if I substitute lambda 1 t equal in lambda 1 t for t 2000 kelvin if I substitute I am going to get lambda 1 as 1.1 micrometer what was the question answered now the wavelength at which 10% of the emission this figure is wrong this complete thing is sorry this green colored thing should have displaced little bit here and this is lambda 1 so this has got distorted that is what I am trying to say is this fraction is found to be 0.1 and this is lambda 1 so that is what is been shown here that is what that is the figure so this is the emissive power now what is the next part what is the wavelength lambda 2 above which 10% of the emission is concentrated that means what that is what is the wavelength lambda 2 above which only 10% of the energy that is this is 10% of the total emissive power is concentrated that means what is F0 lambda 2 F0 lambda 2 should be 0.9 so now life is again F0 lambda 2 equal to 0.9 that is how did I get this area under the curve is 1 fraction area under the curve is 1 so 1 minus 0.1 gives me 0.9 gives me 0.9 that is what I have done here in this problem so F lambda 2 to infinity lambda 2 to infinity what is that infinity this is infinity lambda 2 to infinity is 1 minus F0 to lambda 2 that is 1 minus 0.1 you get 0.9 so okay so now lambda 2 I T I should be looking for in the table where at which lambda at what lambda 2 T this is fraction is 0.9 I know the font is very small I am sorry about that that is it is somewhere between 9000 and 9500 okay so you cannot see it 9000 and 9500 okay so lambda 2 T lambda 2 T lambda 2 T lambda 2 T lambda 2 I get 9382 micrometer kelvin if I interpolate so I get lambda 2 please add this one lambda 2 equal to 4.69 micrometer 4.69 micrometer is the wave length. Now what is the next question asked the question is not over determine the maximum spectral emissive power and the wave length at which this emission occurs is that right that is where does the maximum emission what is the what is the condition for which or what is the wave length at which the maximum emissive power occurs have we studied any law for this. Wien's displacement law that is lambda maximum if you see the Wien's displacement law we see that if you go to Wien's displacement law what is Wien's displacement law saying if you see this Planck's distribution it is saying that this peaks are curve fitted by an equation lambda max into T equal to 2897.8 micrometer for our problem I know the T what is T 2000 kelvin if I substitute T equal to 2000 I will get my lambda max so that is this lambda max that lambda max equal to 1.45 micrometer at 1.45 micrometer I can get the what is that the emissive power at which it is maximum see because we defined this fraction because that table is there we are able to solve this problem very easily otherwise you have to sit down and do the integration every time that is not easy so that is the reason this table helps us in easing out our problem very very fast. Now what is the next portion determine the maximum spectrum emissive power we found just the wavelength what is the spectrum emissive power how will you find that spectral emissive power how will you find that again from the table now you will realize you have I lambda comma B lambda T upon lambda comma B lambda max comma T now let me just see what exactly is going on here yeah yeah so that is in the third column I will get that and then I will multiply fine that is you see the third column what is the third column it is if you are not able to see let me write that that is I have the third column as I just help me out I lambda comma B yes I mean upon lambda lambda comma B upon sigma T to the power of sigma T to the power of 5 I lambda comma B sigma T to the power of 5 of course I lambda comma B is function of lambda and T this ratio is there so I know that black body is a diffuse emitter if I get the intensity of radiation I can get the emissive power so I know the temperature I know sigma all that I need to do is at lambda max T equal to whatever I had got that is the maximum wavelength at which that is at maximum when does the maximum spectral emissive power be there at lambda max T equal to 2198.5 for 2198.5 what is this ratio I am sure that at least should be there okay I can take 2200 thing that is it is 5.89 649 into 10 to the power of minus 5 let me see is that what is the maximum what I have taken yeah is that is that right no I have taken something else oh no 2898 I saw wrong 2898 means I should be seeing I should be seeing 2900 so that is something around 7.23 into 10 to the power of minus 5 so if I put that 7.23 into 10 to the power of minus 5 I think above values are something wrong please be careful with this table there is something wrong with this table in the top these three values are wrong and I guess these two values are also wrong 10 to the power of minuses are missing okay we will check that and correct it back so if I put that ratio that is 5. that is 0.722 into 10 to the power of minus 4 and sigma T to the power of 5 sigma is 5.67 into 10 to the power of minus 8 and T is 2000 to the power of 5 I get 1.31 into 10 to the power of 5 I am not interested in spectral intensity I am interested in emissive power so to get the emissive power because I know the black it is black body all that I need to do is multiply by 5 I will be getting that per meter square micrometer this is the emissive power at the maximum spectral emissive power at the wavelength at which it can be maximum fine so now what is the next part of the question what is the irradiation incident on the small object placed inside the enclosure that should also be equal to what sigma T to the power of 4 whatever is being emitted by the enclosure has to be absorbed by my black body because it is very small so irradiation of any small object inside the enclosure may be approximated as being equal to the emission of from a black body at the enclosure surface temperature so because of which I can compute that so this is same as what we had written here so that is how we have solved this problem that is band emission so this concept what we have elaborated in the last one half an hour is that we have introduced the concept of band emission that is what is the fraction of emissive power between two wavelengths that band emission concept we have elaborated and for one time these integrations these integrals are integrated and kept as in the form of a table and now I can using this table I can calculate the intensity of radiation and the fraction at any particular wavelength so that is the that is what we have learnt from this what is this band emission so there is another problem I am not going to solve this problem I would request you to solve it yourself because it is not so difficult problem now let me introduce for next one half an hour I am going to spend on some properties which have been postponing since morning that is we are going to introduce three properties or four properties emissivity absorptivity reflectivity transmissivity first is emissivity okay so if you see here I am giving definitions why I am flashing all these transparencies is because morning professor Arun said four things one is things can vary spectrally I can have things can vary direction on the basis of directionality and I can have total and I can also have hemispherical so based on these four four definitions we will define emissivity also as four different definitions so if I define emissivity similarly I would have defined for absorptivity transmissivity and reflectivity I am not going to define for absorptivity transmissivity and reflectivity whatever I am defining for emissivity is valid for all others but everything is there in the notes I would request you to see the notes but I am going to define you only the emissivity okay so what is black body is an ideal emitter no surface can emit more than a black body but all real surfaces are going to emit less than the black body so that how much it is less is characterized by emissivity emissivity is the radiation emitted by a real surface to the radiation emitted by a black body remember the pointer at the same temperature both numerator and denominator has to be written that is the radiation emitted by the surface at the same temperature radiation emitted by a real surface at a given temperature upon radiation emitted by a black body at the same temperature that is what we mean okay so that is emissivity okay now emissivity is going to vary as I said spectrally and this is spectral distribution if I have this is the black body and this is real surface okay the real surface cannot be above this it can only be below this that is why the emissive power of a real surface is going to be lower than that of black body this ratio if I have to calculate at every wavelength at every wavelength if I calculate the ratio that is what is called as spectral emissivity now emissive power can also change with the direction okay can also change with the direction so if I have to take the directionality in token black body is has no preference to the direction but real surface has preference to direction okay so if I have to take into account then I have to have directional dependency also in my emissivity definition so real surface will have directional distribution it need not be diffused unlike black body and real surfaces can have spectral distribution also of course black body also add even black body also is having spectral distribution so is the real surface okay there is nothing new there but directionality wise real surfaces and black surfaces are different okay now what is the definition what is this telling spectral directional emissivity first is let me write let me restate spectral directional emissivity all these definitions four definitions I am writing let me write these headings so that we do not lose track of what we are doing spectral directional emissivity spectral I want all of you to write along with me spectral directional emissivity that is epsilon lambda theta, 5 this is what we mean by spectral directional emissivity and all these definitions I am going to state that at a particular temperature at a given temperature okay so that is comma this subscript only says that it is varying with lambda it is varying with direction theta comma 5 at a given temperature now next definition what is that this is spectral directional emissivity next is total directional emissivity total directional emissivity okay so what does the total directional emissivity total means what it is spectrally averaged spectrally averaged so that is why I am seeing here only epsilon theta theta comma 5 comma t epsilon theta comma 5 comma t so it is usually called it is a function of that it is usually written as epsilon theta that is what you are written here epsilon theta it is a function of theta comma 5 now next one is spectral hemispherical emissivity spectral it is all English there is nothing very different or difficult spectral hemispherical emissivity that is epsilon lambda lambda comma t note here epsilon is not a function of theta and 5 because it is averaged over complete hemisphere so epsilon lambda lambda comma t here it is only a function of lambda and t the last definition is total hemispherical emissivity total hemispherical emissivity it should be a function of what this epsilon should be a function of what it is spectrally averaged that is why it is called total and it is in all directions it is averaged that is for complete hemisphere it is averaged that is why it is hemispherical so it is neither dependent on lambda nor dependent on theta comma 5 then it should be dependent on what only temperature so epsilon t okay so spectral directional total directional spectral hemispherical total hemispherical that is all you see directional is common hemispherical is common otherwise you have spectral total spectral total is that okay so now having understood this let us define each one on a fast note epsilon lambda comma theta lambda comma theta 5 comma t equal to i lambda comma e lambda comma theta comma theta comma 5 comma t upon i lambda comma b lambda comma what does this mean what does the numerator mean it means that this is the radiation intensity at a particular wavelength in the direction theta comma 5 at a given temperature upon black body will black body have theta comma 5 no because it is diffused but black body intensity is it dependent on wavelength yes it is dependent on wavelength and it is dependent on temperature temperature will not keep stating every time because both in the numerator and the denominator in all the definitions temperature is going to be same so temperature is not a variable at all for now so this is the intensity of radiation emitted at a particular wavelength in a particular direction at a given temperature upon intensity of radiation emitted by a black body at the same wavelength and temperature is that okay I am not writing this again I hope you all have notes and you are seeing this now total directional emissivity so epsilon theta theta comma 5 comma t equal to i e intensity of radiation emitted in the direction theta comma 5 t upon i b t why here lambda is missing because I have averaged for all wavelengths okay but this averaging I have done in only one direction that is theta comma 5 direction in only one direction I have done in the numerator in the denominator there is nothing like direction because in all directions it is same it is uniform so total directional emissivity is given by i e theta comma 5 comma t now what is spectral hemispherical emissivity now I am going to ask you a question spectral hemispherical emissivity I am not writing intensity I am writing emissive power why you notice please notice this spectral hemispherical emissivity I am not writing intensity I am writing emissive power why intensity is the only one which is having directionality but the emissive power it is it is integrated over all directions theta comma 5 that is what we realized when we defined intensity and emissive power so that is the reason why we have defined spectral hemispherical emissivity as e lambda lambda comma t upon e lambda comma b lambda t please note this please note this it does not occur to us that easily if you are not understood also go back and think you will understand go back to the definition of spectral intensity and spectral emissive power you will understand this this is a subtle thing because student is going to ask you how did I write this you need to know that now what is that I am going to do relation between spectral hemispherical emissivity and directional emissivity how do I do that let me start off with spectral hemispherical emissivity that is spectral hemispherical emissivity is epsilon lambda lambda t is given by e lambda lambda t what is e lambda lambda t given by is i lambda e lambda comma theta comma 5 comma t note this why am I writing always subscript e emitted if you are doing absorptivity you will have to take irradiation okay so so lambda comma e is lambda comma theta comma 5 comma t and then for directionality you have to take sin theta cos theta d theta d phi this is the where did I get this from this is the definition of emissive power okay okay so if I take that and integrate that and on the denominator in the denominator I have i lambda comma b lambda comma t sin theta cos theta d theta d phi but i lambda comma b is independent of direction I can pull this fellow out of the integration and integrate only sin theta cos theta d theta d phi that is what I am doing here so I am pulling this out I am pulling this i lambda comma b and pulling this out and getting this into the below the denominator I can take this i lambda comma b lambda comma t anywhere why because if I pull it in it only means that it is it is a constant and the integration we I am doing with respect to direction when I say constant not with respect to wavelength or with respect to temperature but in terms of it is uniform in all directions this integration is with respect to direction so I can push it in that integral so i lambda e lambda comma theta comma 5 comma t upon lambda comma b lambda comma t what is this ratio we had just defined that ratio is this so it is spectral directional emissivity so if I substitute that as spectral directional emissivity I have sin theta cos theta d theta d phi and if I do this integration which I am not going to do if I do that integration you are going to get epsilon lambda lambda comma t equal to 2 into 0 to pi by 2 epsilon lambda theta sin theta cos theta d theta here in this I have taken epsilon lambda comma theta as independent of pi as you with the angle I have taken it as independent of pi so that is why I am able to pull out that phi and say that as 2 phi if I integrate d phi I get 2 pi so that is what I have done you can ask me and say how did you do that you cannot do that yes I cannot do that that is an assumption I have made okay so I have no justification in making that assumption there is no justification in making that assumption I have just to make it look little better I would made that assumption if you are a purist your definition of connection between connection between spectral hemispherical emissivity and spectral directional emissivity ends here okay so now what is the last definition left out total hemispherical emissivity here also I am not using intensity I am using emissive power because it is hemispherical the moment you see hemispherical you are going to get into emissive power why you please sit down and think okay so epsilon equal to emissive power at a given temperature upon total hemispherical emissivity equal to emissive power at temperature T upon emissive power of the black body at temperature at the same temperature so what is this E of T just now we have derived this what is this this is nothing but what is this how did I write this this is E lambda T I can write that as epsilon lambda lambda T into E lambda comma B lambda T that is what I have done here now that is it so these are the four definitions which you need we have defined that is spectral directional emissivity total directional emissivity spectral hemispherical emissivity and total hemispherical emissivity these are the four definitions we have introduced so now having introduced them before I go to various band emissions and things like that similarly one can define what is called as okay I have not let me formally define before I go to the band emissivity is I will define what is called as absorptivity reflectivity and transmissivity it is quite straight forward I think every one of us are very comfortable with this if there is an irradiation G all of that cannot pass through that is some amount of it is transmitted that is tau G is transmitted rho G is reflected and alpha G is absorbed if I combine these three I should be getting G so G equal to G absorbed plus G reflected plus G transmitted which is in which G absorbed is equal to alpha G rho here G reflected equal to rho G G transmitted equal to tau G G G gets cancelled out everywhere I get alpha plus rho plus tau equal to 1 so what is alpha alpha is absorptivity what is rho rho is reflectivity what is tau tau is transmissivity compared to incident radiation how much is absorbed is absorptivity compared to incident radiation how much is reflected is reflectivity compared to incident radiation how much is transmitted through that body is transmissivity so for opaque surfaces generally for opaque surfaces transmissivity is 0 opaque means solid to take any solid plate transmissivity is 0 okay so I will have absorptivity plus reflectivity later on we will show that absorptivity is equal to reflectivity under restricted condition but that we will do little later on but that is why we first teach emissivity and then come to absorptivity transmissivity and reflectivity so I have absorptivity plus reflectivity equal to 1 for opaque surfaces now similar definitions the way we define spectral directional emissivity we can define spectral directional absorptivity spectral directional reflectivity spectral hemispherical absorptivity and reflectivity all definitions roll in the same manner so I do not have to go through all that I need to make differentiation is that for absorptivity I have to consider intensity that is absorbed for reflectivity I have to consider intensity that is reflected that is all the definition or instead of emissive power I need to take for absorption irradiation similarly for reflection also that is all the differences otherwise all definitions roll to the come to the same way or turn out to be looking similar complete derivation I would look I would request you to look into this in the sit down and re derive or rework what all derive all the definitions in the same way I did for emissivities four definitions okay I think if we do that I think if we do that now we can come to what is called as emissivity function like band emission emissivity is also not going to be spectacularly same everywhere we said that there is going to be spectral emissivity if you take emissivity usually this emissivity is measured by what is called as FTIR spectrometer Fourier transform infrared spectrometer so if you put this if you put your surface under FTIR spectrometer let us not get into how it works and things like that we will be digressing. So if we get into FTIR spectrometer if you put my surface under FTIR spectrometer I typically get an emissivity at a given temperature typically FTIR does at room temperature so if you do that you are going to get the emissivity something like this okay so that means what emissivity is a continuous function of lambda now I need to break this so this is the function what am I assuming now between 0 to lambda 1 I will make a reasonable assumption and say that that is constant and that constant is epsilon 1. Now between lambda 1 to lambda 2 instead of this sinusoidal wave looking thing I will convert and imagine that it is a square wave it is looking something like a square okay it is looking like a square and here the peak emissivity is epsilon 2 and then it is dropping to epsilon 3 at lambda equal to lambda 2 and subsequently it is constant whose emissivity epsilon 3 now the question is what is the average emissivity if this is the question if this is the total thing this is the emissivity function as lambda with spectrally that is how it is if it is varying what is the average emissivity how do I compute this average emissivity so that is what is given here how do I do this I will be taking the recourse of band emission how did I write this equation what is this equation what is this equation emissivity by definition is what let me just take the range 0 to lambda 1 emissivity is what emissive power of a real surface upon emissive power of a black body emissive power of a black body is E b but what is emissive power of a real surface emissivity into emissive power of the black body but emissivity epsilon 1 I can take out from this integral only within the range of 0 to lambda 1. So, epsilon 1 into E b lambda d lambda within the limit 0 to lambda 1 similarly epsilon 2 is epsilon 2 into E b lambda d lambda between the limits lambda 1 to lambda t upon E b plus epsilon 2 into E b lambda d lambda 2 to infinity upon E b. So, epsilon 1 what is this what is this by the way this fraction we have just defined that is the band emission fraction f of 0 to lambda 1 what is this fraction f of lambda 1 to lambda 2 what is this fraction lambda 2 to infinity what is this fraction f of lambda 2 to infinity. So, that fraction band emission idea is helping us even here to get the average emissivity. Let us quickly solve a problem what is the problem given is emissivity is given to be epsilon 1 equal to 0.3 from for lambda 0 to 3 micrometer let me see if there is any figure no epsilon 1 equal to 0.3 for lambda 0 to 3 micrometer and between 3 micrometer to 7 micrometer epsilon 2 is 0.8 and between 7 micrometer to infinity it is 0.1 why am I looking for the figure this is the figure epsilon 1 is 0.3 lambda 1 is lambda 1 is 3 micrometer and epsilon 2 is 0.8 lambda 2 is 7 micrometer and epsilon 3 is 0.1. So, that is what is this so all that I need to do is apply this if I do the application and I need to get the band emission what is that I need I need to know the temperature that is the temperature of my surface is 800 Kelvin. So, if I have to find that lambda t so there are only two wavelengths that is 3 into 800 is 2500 micrometer if you see that table I am not going to go to that table if you see that table you get F03 as 0.140256 and lambda 2 t is 5600 micrometer Kelvin and if you see that fraction let us go and see because my students here are seeing so that means everyone is tempted to see 5600 is 0.701046. So, if I that fraction if I substitute that here that is 0.701046 so what is my relation epsilon 1 F0 lambda 1 epsilon 1 is 0.3 F0 lambda 1 is 0.14 plus epsilon 2 is 0.8 what is F lambda 1 to lambda 2 what is this yes F lambda 0 to lambda 2 minus of F0 to lambda 1 that is what we did. So, 0.701046 minus 0.140256 plus 0.1 into this is what this is 1 minus that is whole area under the curve minus that fraction. So, 1 minus of 0.701046 you get a net emissivity of 0.521. Now if I have to find out what is the emissive power net emissive power from my body epsilon sigma t to the power of 4 what is my net epsilon epsilon is 0.521 if I put that this is the surface my surface is going to emit 12.1 kilo watts per meter square of radiation that is what we understand from emissivity I think there is another problem I am not going to solve this problem you please go through this problem yourself. So, because essentially it is dealing with directional distribution and spectral normal distribution and spectral emissivity. So, please go through this problem every step is there here please go through this problem you will be able to understand it yourself. I think I have loaded too much in 45 minutes. So, I will not I will I will not take up this emissivity variation with theta and things like that tomorrow morning we will start off the day with how do we get the emissivity how do how do we measure emissivity for example and how do we get the absorptivity and how does it vary why is emissivity dependent on surface temperature and absorptivity dependent only on the source temperature we will try to understand all of this tomorrow morning 9 o'clock.


2 years ago, we were separated by the ship. I'm still so confused. Oh my god! Dude, wait, what? Dog! Kuma is the goat! Like, they said that the original Kuma is dead. So is it just programming? So he spent his remaining... Oh, because the navy was catching on to him and how he was helping. Then if he lost all of himself, why would he defend the ship without his personality? We're going to mission. Dude... What a beast! There's another, like, little loose end to remember.


My name is Ann Wright. I'm a retired Army colonel. I'm a former U.S. diplomat. I resigned 20 years ago against the Bush war on Iraq. And as WikiLeaks, Julian Assange, gives the evidence for U.S. criminal actions in the war in Iraq and Afghanistan. And now we see that who is getting criminalized. It's the journalist that posted this. We're here in front of the State Department to hand in a letter to Secretary Blinken, because he was just in Australia. And when he met with the foreign minister, Penny Wong, she said that this case against Julian Assange, whose Australian citizen has gone on for way too long, the prime minister has said the same thing. A group of 48 members of the Australian officialdom have said the same thing. They all want the case dropped. They want the U.S. to stop trying to extradite Julian Assange to the United States, where he faces charges that could lead to 175 years in prison. We're very disturbed by comments that Secretary of State Blinken made in Australia that Julian Assange is wanted for very serious crimes. Those documents that he published show evidence of very serious crimes, as well as U.S. interference to prevent covering them up. When I think of very serious crimes, something like U.S. soldiers executing 10 handcuffs civilians and then calling in an airstrike to cover up the evidence is a serious crime. Secretary of State Blinken has made human rights and press freedom and democracy a huge part of the rhetoric he uses when doing diplomacy. But the rest of the world rightfully sees this as the persecution of a dissident by the world's so remaining superpower, and that whenever Blinken or Biden or others bring up press freedom, bring up human rights, bring up democracy, not only countries that we have correlations with, but our own allies respond with what about Julian Assange as they should. So we're here to say to Secretary Blinken immediately end the dangerous and inhumane persecution of Julian Assange, free Julian Assange now.


Everybody forced here ripping three boxes for Steven a Steven's got two boxes of 2022 Bowman baseball sapphire And then I think it's inside that box, but it is a 2022 fanatics mystery autographed full-size Authentic football helmet Good luck Steven and thanks again. We'll finish up with the helmet. So let's start with some sapphire. I hope so man The authentic's gotta be gotta be sick. Love the I've only held a couple of authentic's and they are Really like way nicer than the in the replicas All right 22 sapphire. Let's hit some big stuff before we get to that helmet though. I got Marco Luciano, Jordan Walker Brennan Davis and Eduardo Lopez First Bowman Eduardo Lopez Austin Martin first Bowman for the Brewers, Brennan, Yoruba, Shrae Sweeney And an Edgar Caro at Angels Denzer Guzman Spencer Torkelson, Luis Verdugo first Bowman and Shalen Palonco Yeah, we get it from a local printing place Got Luis Rodriguez first Bowman James Wood. I mean every sticker is it is a fancy tape to be to be fair Alan Serda first Bowman It's like the definition of a sticker. Jose Rodriguez first Bowman Shaco Vien first Bowman Dario Lorenzo and blaze Jordan Julio Rodriguez orange first Bowman Michael Escoto to 50 Nice one there Jason Dominguez, Miquel Triana first Bowman. Yeah, it's a lot cleaner than then than a duct tape Esteven Machado first Bowman South Freilich, Zahid Salinas first Bowman and Brelin Minier Curtis Mead first Bowman now Tyler Soderstrom a Green Matt McClain first Bowman auto boom 41 of 50 Steven Monster hit there. We will mag that for sure and a Bobby Whitt Jr. on the back Wow, all right. Got Johanjit Pernango first Bowman warming Bernabell Brett Beatty and Harry Ford There's a Marcello Meyer Khalil Watson They sapphire Khalil Watson CJ Abrams Victor Lizaraga and Austin Hendrick. Yosua Garcia first Bowman Face auto this time is going to be Denzer Guzman and Carlos Aguiar twins Got Cleveland Jose Pastrano as there's Yonatan Classe first Bowman And Sadane Raffaella first Bowman junior San Quentin Noelle V Marte Aqua Julio Rodriguez to 55 Very nice. Oh, man, that's pretty much a color match too. That's awesome. And a Luca Tresch Pico Armstrong Mires Mackay backstrom first Bowman Jay Allen Yorubi Allen Hellace Anthony Rodriguez Nico Cavadas and Justice Thompson on the first Bowmans Good boxes of sapphire here. You got Hernandez Alvin Guzman first Bowman Jeter Downs and a Jose Ramos very nice even all right show That helmet now So show here and looks kind of on the street. This is where I ripped off the label the shipping label It's sealed and then you have the little phonetics authentic and it says like hidden Authentic helmet like hidden so it doesn't say what it is. So Yeah, let's see There's the big fanatics box This just turn over here fanatics box All right Cool doesn't say anything on the box. Nice All right, here we go Let's see on big one for Steve, and then there's a box inside the box with a helmet inside of it It is a Bronco of the authentic student To him it is a Bronco that is nice John Elway authentic Broncos helmet Dude that is sick clean signature authentic Broncos helmet is John Elway nice one Steven Good stuff Love the authentic Dude that's awesome Congrats on that we'll get that back in the box Good stuff man. Those are gonna be so much fun to open the authentic And yeah, that'll do it. We'll get it right out to you Steven


Hey everyone, I am Rishi Raj, from the Susie web chat team. This video will talk about some of the interesting features of Susie web chat application. You can perform various chat queries which Susie will give intelligent answers for each of them. Let's begin. Now, asking to Susie, where am I? And Susie will send a map type response, then you can ask something like, what is hello in French and Susie will tell you that as well. We can also login to Susie, so we go to the login option, under the top right menu bar and login. You can also sign up to Susie if you don't have an account. Here we go we can see our previous chat history data being loaded. We can send voice inputs and get voice outputs from the chat app as well. Here is a query, what is the weather in New York, we can store feedback as well and this response is stored on our server. You can search messages in the chat as well. You can browse settings and change them accordingly. There are various chat app settings, language settings, custom server configurations, speech to text, text to speech settings etc. Moving on, we see the overview of Susie and its support to various devices, one can see the various team members who have built the app across various devices in our team page, visit the support page where we have mentioned the support available from the developers, where one can report any bugs or help by contributing. FossAsia welcomes all developers to contribute to Susie. The link to the guide of repository and the Gitter account is given below in the description. You can also check out Susie skills at skills.susie.ai and create new Susie skills for the same. Thank you.


Sa gandang xo zero's video. So today we are going to be featuring the choice fate koree again actually for the Bangga family. As you can see here, the update is going to drop tomorrow. It's going to be at September 9 after the maintenance and this is going to be up until September 16. So Thursday as well. So let's take a look at the Bangga family and see what they can offer you guys. Okay. So here we are with the Bangga family. Obviously the Bangga is classified also into their allegiance in terms of nation. You have to be, you know, you have to be worried if you don't, you know, if you don't or if you're not planning to build that nation. Obviously you're not, you know, you're not more or less going to get or summon for that Bangga but more or less most of you guys have already the Bangga family but for those who are beginners and who are new to the game the one that's not included in that banner tomorrow is going to be Topaki because he is actually a blue fate kores. Don't expect him to be there. I'll first discuss to my right going to my left. So first would be Adams. Adams is actually with Astorist Republic. He is one of the Top Black Fate Kores right now. If you're into Black Fate Kores and if you don't have him he is one of the best in terms of dark element. Single target damage is very insane in terms of damage. Next would be Morris. Morris actually right now has a very good place in Lenombe. So if you're building a Lenombe team Morris is actually very good in terms of buffs that he gives attack buffs in particular. So he has a lot of attack buffs passives and also I think his skill one who is S1. So next would be I think what do you call this the one that's usually is Overlook is actually Luke. Luke is more of a defensive guy provoke, heart strike as well not used that much in terms of content can be used actually in PvE or in PvP tag if you want to bring him but again if you want to get Luke you might as well get Tantaloo. So that is the argument here in terms of the Bangga family. So again if you're Astorist and if you're building an Astorist team yes you get Adams but if you're in Nombe you build the Nombe you get Morris as well because he's very good right now in PvP also in PvE for Luke I suggest you skip him Tantaloo is better than him actually in terms of what he brings he's actually a black fate core Tantaloo is a gold fate core which Tantaloo has a lot of skills Next would be Hekin as well Hekin is not used that much in terms of PvP but again he can you might try to use him if you don't if you favor him over the others he actually has ArcHeartStrike as well Focusfire and Lone Shark rework from him and also he has damage over time and I think the last one is going to be piercing damage to all enemies of 249% but again I would not recommend unless really like to get Hekin so again yes for Adams yes for Morris no for Luke and no for Hekin in terms of overall usage I think these other two are going to be better for you because they're gold fate cores especially if you don't have them yet I'll go first with Tantaloo Tantaloo has been a very good mainstay in terms of PvP especially of all the bangas I think he's the one that has been played in PvP that long he's still good even though that FC Schmidt has a counter for him but he's still good you can still bring him very good for Greenland peeps if you want to bring him good for your Greenland team and also for North One Frosty if you want to splash him there let's take a look at his skills um what do you call this why is he very good number one he's good because of heart strike and he has an AOE attack for his S2 that is why he can really bring heart strike to the highest level and he has damage immunity very very you know very annoying and a lot of headache to deal with he's one of the best defenders so far that I know in PvP even though he's been countered by Schmidt he's still good I tell you um if you don't want to bring him in PvP you can probably bring him in PvP tag or in Zeben Stunier but again if you're going to bring him in Greenland make sure that you have him on your team and the last would be um Jin so Jin recently also had his rework I'm actually using him for stories in fact I'm actually using both Adams and and Jin for stories so for Jin he has heart strike as well so all of the Banga family and in terms of it was actually given buffs to his skills so for his passive so secret stealth technique and actually the one that I'm interested in for Jin is his S1 and S2 because give silence and there's another here in relation to Jinai, Jinai is to be the team for charm to take effect branding mark and also he has bind which is actually crucial in today's PvP if you want to bring him he is actually a very good debuffer in terms of bind in terms of silence and he deals a lot of damage as well because obvious S2 is a burst spell 2 cost sorry but again he is going to use up your mana up to 10 when he uses his burst maximum of 10 of course and again this spell has silence and branding and binds mana as well so again you have a lot of choices here for the Banga family you can't go wrong with either Jin, Tantaloo, Horace and Adams just align them with the nation that you're using but I would suggest you skip Heken and look for this one unless you are really into their kit and you really want to build them then be my guest okay guys so again the Banga family one of the best I think themes that they have especially for heart strike and happy summons guys and till the next video hopefully guys before we end this video you might consider subscribing also click the bell icon and also putting a like to this video please stay safe take care this is the warden and I'm out of here


Hi guys, hope you are doing well wherever you are watching from. Good morning to you all depending on the time that you are watching this video. Thank you so much for coming back to this channel and thank you so much for supporting this channel. Today's video we are going to look at what you call visas in the UAE. Visas in Dubai. Remember recently we saw, it's actually I would call it a saga or we saw what was happening in the UAE. There were a lot of deportation, very many people were called up, kind of. Those that did not have valid visas, those that had expired residence permit, those that did not have the jobs. That is the trend that is happening or that's what happened exactly. So we want to go, we want to look at what you call what is the full update or what are the updates with the visa requirements in the UAE for Dubai. Something that you need to know, right now the new amendments starting with October. For you, for someone to offer you a job in the UAE in Dubai, Sherezia, in whatever Emirate he needs to give you what you call an offer later. That is the latest information that you should know. Remember a tourist visa is not a work visa or cannot get you a job in Dubai anymore. That is the latest updates we have. So meaning that someone to offer you a job in the UAE, he needs to give you what you call an offer later. And that offer later must be verified or must be authenticated later from the Ministry of Humanitization and Emeritization. That is the ministry that is responsible for the labor and its recruitment. So that labor, that offer later must be a verify an unauthenticated job offer. That is for the government but that is for what you call the latest developments that we have. Remember, however, something that you should know that you having what you call a visa visa or a work visa, having a visa visa or tourist visa does not give you a right to work anymore in the UAE. Any of the 7 Emirates that make up UAE, it does not give you a right to work in the UAE. So meaning that when you are got in that kind of scenario, you are reliable to all the penalties and the legal measures that will be taken against you. That is according to the latest information that is being given out by what you call the UAE government. Still something that you need to know, when we are talking about tourist visa or visa visa this may be depending on the duration you are going to stay in the country. Sometime it can be for 30 days, it can be for 90 days and it can be extended. Depending on the plan that you have, it can have what you call a single entry or it can have what you call a multiple entry depending on your plan as a person. But something that you need to understand, a tourist visa, a work tourist visa then what you call a visa visa does not give you a right to work in the UAE anymore.  Then let us try to see what are now the latest requirements that you have. Yes, you need to go to the UAE or you need to visit or to have a tourist visa or visa visa in the UAE. Remember before people would visit and find accommodation in any way you would have what you call a dummy ticket that is going to return you but is not a real ticket so you go but you don't have a return ticket. But right now the latest information that you should first of all you should have that ticket a two way and flow ticket. It should be confirmed because they will have to confirm from the airline itself that is paid up for you to have that visa visa. Then also you should also have what you call a hotel booking. A hotel booking for the duration that you are going to stay in Dubai and should be verified too. Not anymore of sleeping bed spaces. Not anymore of sleeping wherever you want to sleep. No. Remember we are looking at these countries undermining trying to analyze what is happening. What will happen? These are all global effects or aftermath that came after the pandemic and what the achievements or the targets these Gulf countries have in 2030. So you are finding that to some extent in the coming years we shall see these Gulf countries in the next euro. Why? Because they are trying to clear up everything that is happening. Then still also you need what you need to understand before you look for a visa visa to go into Dubai. You must have what you call a backstatement that has a six month saving on it. It should have a six month savings on it. Or if you do not have that six month backstatement you should have that cash that is amounting to 5,000 dirhams. To show that you can sustain or you can take care of yourself when you get to the latest requirement that you are supposed to have. Yes we may look at other requirements like the passports where you need to have the visa, you need to have all those other requirements. But these are what you call the now the genuine these are what you call the general added requirements that you must possess before you look for a visa visa. Remember I am telling you the latest updates the visa visa a tourist visa does not give you a right to work in the UAE not like it used to be before so meaning that all these situations are going to go in what you call a hard way for you to get a visa to get a job you need to get an offer later and that offer later you can also check the authenticated offer later on the government website when it's given. I'll give you all the links of the government website where you can check the offer later has been given to you by the company. That company must be genuine must be an existing company in Dubai because there is also a link where you can check for those companies that are genuine in Dubai. Hope I have tried to share something for you for a person to ask that question. Thank you so much. See you again in the next video. Smeks from the next creation.


I had a good sleep last night. I feel good this morning. I'm looking forward to seeing these roads. It's a long time since I've been in Southland rallying, so it's a beautiful day. So yeah, I just want to get to Wanaka tonight and then focus on the last day. Special Stage 39 Longwood is the first of six stages for the seventh day and for the leaders of the E-Pace Silver Fern, it will be their last. Oh, I'm gutted.  You know, a tough rally and a day and a half to go in the position we're in and yeah, it's hard to take, but we've had a good time, a brilliant time. It's been some awesome competition and yeah, I think we can still hold our head up high. It's Taperona's co-driver who has won more Silver Fern rallies than anyone else. Built Braunstuk's car in 06 and we won. Co-drove for Andrew Grundy in 08 and we won. Co-drove for Judi in 10 and we won. And last time we got fourth. And then, it's on the trailer. It's gutting. Absolutely gutting.


Hey everybody welcome back to the channel today I'm going to be talking about my time with alacrity now about a month ago I decided I was going to try out alacrity because it's one of those terminals that a lot of people seem to like now this is written in rust so it's kind of a meme to use it and I kind of resisted it for a while because I was such a big fan of termite and then I tried st for a while and st was fine except for the whole patching thing and you know I've just kind of been switching back and forth over the last five or six months between different terminals to see if there's anything that I like better than termite before alacrity I could honestly say that there was definitely not any terminal that I liked better it was simple it didn't have a whole bunch of bells and whistles and I could just you know get my work done or use my programs and apps or whatever and move on I didn't have to spend a lot of time configuring it is what is really what I'm talking about but then I've used alacrity now for a month and I can see a lot of good things about it so I'm going to talk about those good things and I'm also going to talk about a few things that have kind of bothered me about it or maybe not really bothered me about it but more have given me pause on switching to it completely let's go ahead and jump in so the first thing we should take a look at is alacrity itself now this is what I have alacrity looking like it has some transparency because of high com I've done nothing incredibly you know complex or whatever with the layout it has a very nice color scheme to match my new rice for dwm which is good but other than that it's just it's just a terminal it's not much to look at the pros and cons of alacrity that were explained to me over and over again in the comments of my st video where that alacrity is fast and that alacrity has features that are awesome now in my month of using it I will have to say and be honest I've not noticed a huge speed difference between this and termite now I'm going to say that and then I'm going to say this the stuff that I do in the terminal doesn't really stress any terminal out so the time differences for the things that I do in the terminal are negligible because none of them are power intensive none of them are going to say take up all of my gpu power which is supposedly the premier feature of something like alacrity because it can use gpu acceleration or whatever I don't think that I've ever really tapped into that power because my uses for the terminal are fairly simple I do some scripting I use like NC spot I use ranger those are all the things that I do none of them run particularly slow or particularly fast when compared to other terminals that I've used now if I ran something like time you know fetch something like that I could get the time and stuff like that for how long it took to run this I could do the time for you know whatever command that I wanted to do and yes actually having the computer show that time would go through and tell you that alacrity is faster even on the smaller commands than something like termite but it's all a perception thing because really I can't tell a difference between because between 9 milliseconds and 10 milliseconds I mean I really just can't I'm not that perceptive I guess so in terms of speed I really haven't noticed it being that fast now I could see if you do tap into that power of the gpu acceleration I could see that it would actually go through and be a benefit for you and I do apologize for the lawnmower in the background apparently it's spring we're just gonna have to put up with that kind of nonsense um where was I oh speed so like I said I don't I didn't notice a lot of speed but I could like I could see if you're doing things like compiling a lot of code if you're running you know a lot of intensive programming or things like that you'd probably see some of that you know gain that you wouldn't see in like something like termite or st or whatever the other thing that was told to me by the those commenters that I would like about alacrity is the features now let's look at the standard alacrity configuration file this is what that looks like it is 863 lines long now most of them are comments so take that for you know what you will most of those comments are actually kind of like the man page it tells you exactly what it's doing and you can delete all those things and I'll show you my configuration file here in a minute but there are definitely a lot of really cool options that alacrity has too many things really because like I said before my use of a terminal is very simple I don't need all the bells and whistles um for example if we go down here at the bottom to the bottom we can actually see that alacrity has a ton of key bindings it actually has a vim mode which I didn't actually get a chance to try out uh mostly because I didn't really want to go through and learn the key bindings and then just switch away from them because I don't want I didn't want to become reliant on them and then go to a terminal it didn't have those and then I'd you know miss alacrity but this is something that a lot a lot of terminals have in terms of customizability like I think kitty does I'm sure like st does but c is so hard to kind of get a hold of for at least for new users that's kind of hard to you know change those and it's features like these that I just did not get into because I didn't really need them so I think I'm a poor customer for alacrity in terms of feature set because I just don't need all the features that it offers and I don't take advantage of the speed so those two main features that it that supposedly hold it higher than the rest of the terminals out there I don't use so that's the lesson that I've learned over the last month is that I just don't take advantage of how powerful alacrity is now that being said I do like alacrity so there's a couple features that I did really like so for example let me show you my configuration file this is my configuration file and what did I say the alacrity configuration file was 863 lines long mine is 39 long 39 lines long that's really hard to say 39 lines long fuck tongue twisters all I've basically done is taken out all of the comments in the entire default configuration left the colors left the font all I've kept is setting one font because the font family that I use has everything that it needs so I don't actually need to go through and set a separate bold font and I hardly ever use bold fonts in my terminal anyways I don't need italics and none of that stuff so I just have one font set because I have the colors I have some offsets here to actually show this bottom bar which for some reason gets cut off when the font you don't have an offset I have some padding which does the same thing I set this environment thing here which allows some theming things to work properly in them and then I have the the scrolling history that's literally it now one of the things that I really liked about this so I can go through and change something here if I change the text size to 16 and then save this it should go through and actually change the size automatically that's really cool and it's going to be a feature that I miss if I switch away from alacrity because traditionally if you make a change in say like termite let's say if I open up termite here I open up termite and I fit into my .config termite and then this is my termite config and if I made a change to the font size if I made if I changed this to 16 if I wanted that to take effect I have to quit out of that I'd have to quit out of termite open up termite again and then it would have made the change and obviously I didn't make a big enough change to actually show that it was a change but the point is it wasn't live that I mean and really that's the way that most terminals do it you make a change you have to quit the terminal instance and then restart it that's the way it's worked for time in memorial it's just the way it does and the fact that alacrity has changed that and made it so that I can go through and change my configuration file at least the visual parts of it and then have it basically recompile live is really cool I mean I just can't tell you how much I will miss that if I do switch away from it the other thing that I really enjoy about alacrity is the error reporting so if I go through and made an error here I'm not going to make an error but if I've gone through and I've made a mistake like I I've missed an apostrophe or I've mistyped something whatever alacrity will actually go through and tell me what's what I did wrong it'll have an error at the bottom of the screen it will go through and tell you the line that it was on and why it's wrong that's not something you see in a terminal all that much usually when you make a mistake in a terminal configuration file it just defaults back to the default config and you're left wondering why it's doing that I mean obviously you know you've made an error but it's not going to tell you where it's not going to tell you why and those I mean that's a big deal especially if you mess around with the terminal configuration file a lot like it reminds me a lot of the error reporting in i3 when you make a error in i3 it also will bring up a detailed log of what you did wrong tell you where you did the thing wrong and what it was expecting now dwml also does the kind of the same thing it will show you in what file and stuff at compile time but it's not as user facing because you actually have to know to compile those things and know to look for them whereas with something like i3 and in this case alacrity it actually puts up a big red banner saying you have an error you have to fix it I mean that's awesome so those are the two things really that I like the best about alacrity as I said before I didn't really get into the two main selling points of alacrity as much as I probably should have and that's mainly because that's not my use case for a terminal so I guess the bottom line is or the final question is am I going to continue to use alacrity and as of this moment yes I am I have officially made the switch on all my computers to alacrity I still have termite installed it's still my security blanket I guess but I like the auto updating of alacrity so much that it's hard to switch away now I don't make changes to my terminal configuration file often but I love the fact that when I do it updates that live and that just that just that one feature just is amazing I mean it's just so good and like I said if I do someday decide to switch away to go try maybe kitty again or maybe I'd try you know whatever I mean I don't even know if I didn't I know that that's one feature that I would definitely definitely missed so that is it for this video thank you for watching make sure you follow us on twitter at the next cash you can also support us on patreon at patreon.com slash linuxcast with that in mind I'd like to take a moment to thank our current patrons Devon Marcus Meglin American camp thanks everybody for your support thank you for watching I'll see you next time