Yeah, everyone welcome back. Thanks for those of you who stay with us after the pedals lecture. Those of you who are just joining us, this is a panel session following Dr. Hansman's talk about more electric and more automated aircraft and some of the innovation and exciting opportunities happening here. So this panel, Professor Hansman has been joined by several Purdue faculty members that don't reduce themselves, but we tried to pick a panel that has expertise in airports, air traffic management, aerodynamics and aircraft design, human automation interfaces, and all of them know things in multiple areas here to help round out the discussion. So what I get to do is introduce our moderator for today. The moderator is Brandon Sells. Brandon is a PhD candidate and a research assistant in the School of Aeronautics and Astronautics here at Purdue. Here is MS in Aeronautics and Astronautics from us here at Purdue and his BS in mechanical engineering with an aerospace concentration at North Carolina ANT. Recently Brandon has been developing and employing modeling approaches to investigate important operational limits that might hinder future use of urban and region air mobility and is also looking at ways to examine important characteristics of electric and highly automated aircraft with the region that they may operate in. So with that I'll turn it over to you, Brandon. Great, thank you. Welcome everyone. We definitely appreciate you sticking with us and right now I'm actually gonna introduce the panel and so you can hear from their great voices. I'm gonna start from the farthest and work my way inward. We're gonna start with Dr. Hubbard. Dr. Hubbard is an associate professor in the School of Aviation and Transportation Technology. She is a licensed engineer and has done research in transportation planning and operations including airport operations and safety. Please welcome her. Next we have Dr. Bear Caldwell. Dr. Bear Caldwell is a professor of industrial engineering and Aeronautics and Astronautics by courtesy at Purdue. His research team is the group performance environments research grouper laboratory. A grouper examines and improves how people get, share and use information while in settings including aviation, critical incidents, response, healthcare and space flight operations. Please welcome Dr. Culpe. Dr. Hansen, welcome again. For those that didn't make the lecture before you missed a great treat. But Dr. Hansen is the T. Wilson Professor of Aeronautics and Astronautics at MIT where he is the director of the MIT International Center for Air Transportation. He conducts research in the application of information technology and operational aerospace systems. He has over 6,000 hours of pilot and command, time in airplanes, helicopters and sail planes, including meteorological production and engineering flight, test experience. Please welcome him. Next we have Dr. Leefer Lee Sin and he is an assistant professor with the School of Aeronautics and Astronautics at Purdue. His research is focused on simulation based design optimization of aerospace systems such as aircraft using surrogate modeling methods. Please welcome Dr. Lee Sin. And finally we have Dr. Dimfin Sung, he is a professor of aeronautics and astronautics. Before joining Purdue, he was an associate scientist with University of California Santa Cruz at NASA Ames Research Center. Professor Sun's research interests include distributed control and optimization, cyber physical systems, unmanned aerial vehicle systems, air traffic control, air transportation and intelligent transportation systems. Please welcome Dr. Sun. Great. So the format for today, we're going to start with some questions, but definitely feel free to find the mic in the audience so that your questions can be heard. I'm going to start you guys off just in case you need a minute to find your questions. But panel, feel free to jump in at any time. So our first question today is, what are some examples of electric aircraft and automated aircraft that have recently made their way into use in operations? So I would start. So from electric aircraft, the only electric aircraft that I know that's actually certified, it's only certified in the in Europe is the Pipstroll training aircraft. So it's a two seat training aircraft. Everything else is in development. Okay. In terms of automation. Okay. Well, let me say that's on aircraft. If you want to go to UAVs, we, you know, there's a lot of UAVs that are out there. Okay, right. Understood. All right. If you want to go to aircraft and then highly automated aircraft, we, you know, if going all the way back to the Airbus A320, almost every commercial transport airplane now is a fly by wire airplane that is effectively automated, except for taxing out and taxing in. And by the way, we can do that. They just have something for the pilots to do. Of course. And even for like humans being able to accept that, that may be a concern. Correct. Well, this whole question is, what is, what is the willingness of the traveling public to get in a, in a vehicle when there's not a path there. So if you actually look at it from a safety standpoint, pilots probably, there's some evidence of pilots cause more trouble than they help. Okay. But the problem is we don't actually, so we have a lot of accidents that occurred due to pilot error. However, we don't get all the accidents that are saved because of pilot saves. So we don't really know the answer to that. But at some point, we're going to get to the point where we'll fully automate. It's going to probably come in through cargo first. But when will people be willing to get on there? And I think it's, it's a matter of trust. So there's the assumption that the pilot in the front is the first to the scene of the accident, right? So they're going to make a decision that is, has the highest probability of success. That's the social assumption. So, but I think we'll get there eventually, you know, slowly when it really matters. Right. Now, to add on to that, when you think about pilots integrating to the technology, is there a human factors question that comes into play? And I don't know, Professor Caldwell, if you want to take that question for you there? Well, I think the whole list of human factors questions that come into play all the way from where in the design stage do engineers recognize the range of human variability in understanding in processing the situation? I always get frustrated when I hear designers talking about taking the human out of the loop, because the last time I checked, all of the designers were humans as well. And so they're subject to many of the same biases in attentions, considerations that they are and even projections that they're afraid that the pilots are. So I think just that understanding that you are designing for people who may or may not see the world the way you do is one of the most crucial human factors issues there. And another one by analogy, I have a series of sports cars because I like that stuff. And it's really, really nice that in my newer car, it has ABS. And I really like ABS. It's wonderful. And the computer coordinated steering and torque control is wonderful. It's fantastic. I love the idea that maybe I can turn it off sometimes when I'm feeling salty, okay? What I really, really worry about very badly is the moment where the ABS says, I can't do this anymore. And what is that failure mode? They fail over to the human. Well, at that point, if the ABS says I can't handle it, and they tell me with a quarter second that I need to do something, I can't do that. That is an unreasonable and unstable human in the loop control problem. Does the rest of the panel want to comment? Or have any future examples on electric aircraft that they'd like to add? I can chime in for a little bit for like a human involved in the system. You have pilot and we also have aircraft controllers, who are also human beings. And also if you fly an airplane with a pilot, like the pilot wants to talk to a person, right?  Most people don't like it, right? So we still have human controllers. And we are trying to like develop the students supporting tours to help ease the work of traffic controllers. But still, we still have those human factors in terms of the air traffic control systems. Let me throw out a challenge. Should we should we get rid of the high altitude air traffic controllers and automate them out of the system? I would vote no, which I would like to keep human in a loop. See, I think we should, I think we should get rid of the high altitude. Because I think the air traffic control, if for like, to say the North Atlantic or the South Pacific, there's plenty of space there. I have on board equipment. I want someone to call when I have a problem, but I don't think I need to be talking to them all the time, right? So so I, you know, we spend about $300 an hour for every flight hour of air traffic control services. And I'm not sure we need it with the current technology. Go ahead and jump in, Dr. Leeson, if you like. Yeah, I can jump in here, maybe from the kind of viewpoint of the aircraft designer, who's also a person. So first of all, I want to thank Professor Hansman for his talk. It was really good. And I'm really happy to be on this panel. And I think this new class of aircraft is really exciting and interesting from the perspective of vehicle design. And you kind of talked about that a little bit, because you have these new technologies, these new operations kind of open up the design space. And so I think it's really interesting for our students and faculty here to kind of address these things. And also it's an opportunity to work with the industry on these things. So where there are a lot of new things happening. So from the designer perspective is that now you have this new kind of new designs or new concepts. And you kind of have to go away from historical kind of data and kind of statistical based designs. And you're going to start to have to use physics based modeling and maybe optimization as well. And I think there's tremendous opportunity here kind of to leverage those things to really design these things. And because these are really complex systems with a lot of design parameters, especially when you kind of open it up like you talked about. So we're going to have to leverage these physics based models as well as optimization tools. And the good thing about this is there's been a lot of development in the recent history. So there's a lot of open source tools that can do kind of aircraft design using physics. And having those tools, we can use them to kind of evaluate and kind of compare these different concepts. So he showed a lot of concepts today. So I thought that was very interesting. And for example, if you're doing initial sizing, you know, for your those are going to take aircraft design class next semester, initial sizing that you can use these low fatality physics based models. They may be less accurate than the high fatality ones, but they're really fast. So you can kind of explore a lot of different concepts really quickly. And if you need added confidence, then you can resort to the high fatality tools as well. They are really long to evaluate. But so what I want to say here, there are ways to come to combine them and they're like these multi-fatality methods. You can create these surrogate models. And with these surrogates, you can kind of try to simultaneously optimize the vehicle shape, the vehicle parameters with respect to all these different constraints, because there are going to be a lot of constraints within the airspace. That's what I wanted to say. Great. I definitely appreciate that. And something that comes to mind are a lot of the technical challenges that we face moving forward, especially enabling electric aircraft. So Dr. Hubbard, I want to know your thoughts on those technical challenges and you know, where do you think we should be looking at to put research dollars towards? Sure. Well, I actually come to it from the airport's perspective. So I come to it from the infrastructure and really a big concern of mine is integrating the new systems with the existing systems that we have, the transportation systems, the community impacts. And so actually I'm going to leave a lot of technical stuff to you all. But I do think that that's something that's challenging. Right now, FAA Office of Airports has done interim guidance on the kinds of infrastructure that we will need for vertiports. Certainly the uncertainty is we don't know what those aircraft are going to look like. That makes it really hard for us. And one other comment is a lot of historically, if we're talking about the advanced air mobility model, a lot of the systems for the ground with the heliports have typically been licensed at the state level. And so that's kind of, we have a lot of policy issues that really haven't been addressed yet. So I guess some of those issues, those policy issues, those regulatory issues, those are things that will need to be sorted out as we move forward. And honestly, in some cases from an airport's perspective, that's a pretty big deal. One other comment from a technical standpoint, sustainability came up. And that's a really huge issue. And actually that's a big driver for advanced integration of technology at airports because airports are very concerned about their sustainability footprint. When we talk about sustainability at airports, one thing to note is we're not just looking at environmental sustainability, which is critically important. But we also look at the three, sort of the three pillars of sustainability, which are environmental as well as economic. And so what's the sort of economic footprint and how our infrastructure can support the community. And then the third pillar would be the social or the community impact. So again, we have kind of a probably a more broad based perspective than some of the really detailed things that you all are looking at, which are of course critical. But that's kind of where I come in at the airport's piece. Because especially this come to mind where you think about these vehicles that need to use the infrastructure. And so depending on your configuration and depending on your metropolitan, it could lead to a certain configuration that you may need. And again, I just want to remind the audience that if you do have a question, feel free to find us. And I don't know where the microphones are, but I'm sure someone can help us with that. Another question that I have, if we're looking at introducing new technologies into a safety conscious, highly regulated domain like aviation, it can present a lot of challenges. And so from your expertise, you know what trends give us the most concerns on this on the safety side? I think that that the when we're trying to certify things for which we don't don't have an existence proof, we don't have a current method, I would say the when we talked about the thermal runaway of the batteries, we can do that. The solutions we have now are very heavy. So that's going to be hard. The all these new configurations, the tilt rotors and whatever. They're not airplanes. They're not helicopters. They're sort of like the v 22 or the six and so they're they're kind of in there. But we don't have quite the same rules. And fundamentally, you have to look at what the failure modes are. So the the the thermal runaway is a problem that's well identified. The other one I mentioned is the energy density on a normal airplane commercial flight. We need to guarantee the amount of gas I need to take is dependent on what the weather is and what my diversion requirements are whatever. So I know how much gas I need to take. If I do that same calculation, I don't actually know what that transfers to on my battery. Okay, because it's not reliable. So there needs to be a solution for what the battery energy dispatch condition is. That's an open item. And then all of these airplanes have complicated flight control systems. Okay. So if you're in a fly by wire flight control system, and that way we think about this is if it fails and it's critical, it has to it can't fail with a probability of greater than 10 to the minus 9th or 7th or 8th depending on the class of the airplane. So what that means is that I have to have redundancy in the system. Okay. So I have to have and what what has to be redundant? Well, I have to have at least two actuators because if an critical actuator fails, did that that's why you saw so many rotors on the on the helicopter. Okay. But I also have to have redundant sensors. So and by the way, sensors are a problem because it how many sensors are enough? Well, two sensors, if I have two sensors and one breaks, which one is broken? So I don't know the answer. So typically I have to be triply redundant. Oh, by the way, now I have to have the computer could fry. Okay. So now I have to be redundant on the computers. Maybe I can get by with two. I don't know. Okay. Maybe two, maybe three. Oh, by the way, the data bus. Okay. I need to I need to have the wiring. And by the way, if the rotor goes out and cuts the wire, I can't cut all the systems. So I have to run wires in different parts of the airplane. Okay. Oh, I forgot about the software. Okay. Okay. So so in in, you know, how do we prove the software not there? So now, by the way, this is not an this is not a new technology. We do this on fly by wire airplanes. It's incredibly expensive. I think there's a lot of motion on making that more efficient and cheaper. And so that's a place where the technology is there. The processors are smaller. The sensors are smaller. The we can reuse software and things like that. So I think you'll see the Costco down there. But it has to be done right. And these are complicated systems. So how do I check them and certify them as there? So so I, I think it will be there, but it will be hard. So what let me follow up on that because I've been spending a lot of my time recently looking at low altitude operations and lots of discussions about we're going to have these automated systems and taxis and Uber eats over or whatever you're going to call it, right? And everybody is using the low altitude space. You can't get to transcontinental high altitude until you transit low out low altitude. You can't get to space in what until you transit low altitude. So imagine trying to deal with all of these things in a local airspace where someone is saying, yeah, but that's where my market is. So I want to I want to have lots of things in the L.A. Basin and I want to be able to dial up to get my delivery in 25 minutes. I want to get something from Port of L.A. in 20 minutes. I've also got dozens of commercial airliners. I've got everything else going on. Oh, by the way, there's also traffic helicopters and med flights and all that. I really have a lot of worry about how all of those operations are going to interconnect, interoperate and intercommunicate in these spaces. And I haven't even talked about an executive that might buy one of these companies and decide to completely redo the operations model and fire half the employees. Oh, no, that would never happen. Yeah. So I was wondering about what does this mean for EV tall aircraft, for example, like Joby and and whisk with these issues, these failure modes that you mentioned, as opposed to having an East all aircraft that maybe is less prone to those things. I mean, I think all of the airplanes will have to go through that process and do the safety analysis in whatever. I think that the more non traditional, you know, that's why if you look at the Joby airplanes, you know, what happens when one of the actuators gets stuck 50% of the way, right? So you have to they're you've just introducing new sort of failure mode. So there is there is elegance and simplicity of design, which is to minimize that. So but but I think it'll I think they're solvable. They just have to be worked and there's a process there. One of the things that got added into this NPRM is the ability to deal with the total power system. So if you look at the Joby or a lot of these airplanes, they they've been designed so that there's enough redundancy of one system goes out, they can still fly. Many of these things, if you have a total power failure, become a brick, right? And so that's actually in the regulation that it has to be survivable. So you'll probably have a ballistic parachute on that airplane. But those only work for higher altitude. So you have to design it. So the crash is survivable. Okay. Yeah. So I mean, it'll I don't know. I mean, it'll it'll be interesting how they come up with it. They're very complex design choices that need to be made. And forward with that, I think we have a couple of questions, three questions. We can start with one in the back. Feel free. Thank you guys for being a part of this panel to answer our questions. Could you stand up for us? Can we see? Thank you. I'd like to jump back a bit to the overall topic of how in in the electrification and automation of of automated aircrafts, like there's a lot that needs to be processed, right? So do you see semiconductors as a plateau for this processing? And if so, how what are ways to work around that? Do you guys need clarification for the question? Let me start and then you might.  I think we have enough processing power to do it right now. OK, so I don't I don't see that as the limiting technology, right? I think in some future applications where people are doing more autonomy and whatever, but part of the reason why we still have humans doing the supervisory control is for really subtle A.I. type applications that would require a huge processing. We're just not there. And by the way, we don't know how to make sure that that that neural net is right. OK, so it's very hard for the certification agencies to actually approve nondeterministic software. So it's actually much easier for them to say when when the problem gets to this class, call the operation center and bring in a human. Right. So that's why I think it's going to become a supervisory control system where the humans will be there, but they will be there for the value added parts of the human. So they won't be doing.  Right. Thank you. Yeah, I agree. So I in terms of the hardware, I really don't see like much difference as compared to our current aircraft in terms of these electric craft. The major kind of challenge might be like as John mentioned, there is going to be some software and particularly nowadays you have artificial intelligence. I believe that there will be a core part in terms of autonomous vehicles, autonomous aircraft, how to certify the functional AI. I think that's going to be another way to think of it is we will only approve what we can. By the way, it's the same thing on the safety part. We'll only approve or only design to what we can do with confidence with the processors we know we can buy. So if you come up with a new processor, right, which is significantly better, that will open up the design space of what we will do. But it's not going to limit it. Same thing on the safety case. So, you know, when, you know, when you're worried about all of these other operations, they're simply going to say, well, you know what, you guys can't fly there because there's a commercial airplane and we're not going to put any risk to the commercial airplane. So there is a, it's more a safety limitation, you know, is the sort of way to think of it. Yeah. So I'm not really as worried about the on board flops as the bandwidth for comms between everybody. 5G is wouldn't be enough for the projections for LA or New York or Dallas Metro. Hartzfield would be a nightmare. So we have to think about not just what everybody does on their own, but at what rate can you update all of the onboard processors with all the state information that they're generating and then sharing with each other about very local phenomena? No, that's going to be the problem. And remember what's going to really, it isn't going to be the normal operation. It's going to be, you have to guarantee that you design it so when the loss of comm occurs, when I lose the link, that the system can't fall apart. Right. So it's got to be able to coast through a failure of some sort. And even with that, I'll take that question next. And even with that bandwidth, does that affect the like ground operations when you think about remote towers in locations that may not have the infrastructure to have their own tower? Is that also an effect that should be addressed with future technology? Yeah, it should. I mean, the good thing on the ground tower right if you're doing remote is it's probably a landline with alternate is to just take another route on the internet. The ones that are tend to be the toughest ones are the ground to air or air to air links that if you get saturated or you have a failure. So again, in all that safety analysis, someone has to think about that's a failure case.  You then have to make sure you design the system so that when that happens, their plane may have to divert or may have to do something, but it can't crash. Right. Of course. We have a question in the front. Go ahead. Yeah. So I wanted to ask in 2009, there was kind of like a push for smaller jets, which are jet powered. And it ended up being like really expensive. And a lot of the jet projects for like smaller aircrafts didn't really take off because it was too expensive. So I looked at like these hybrid electric vehicles and also like electric and automated aircrafts. And we are putting like batteries on them, which are like really, really expensive technology as well. Will there be any concern that the technology that we're using is too expensive? So that's a good example. So so in that jet thing, the reason why they thought that it would be cheaper was that they thought that they were going to get the remember I use the word scale, they thought there were going to be lots and lots of cases. And so the prices go down when your production rates go up. Okay. For a variety of reasons, partly having to do with the economy, the economy tanked, they didn't get the scale that they thought that we're going to get in.  Okay. There's a lot of that same behavior going on here, which is a lot of the projections that people have have been on assumptions of scale. And that it's going to be really cheap and whatever. These airplanes are not going to be cheap. They're going to be good, and they're going to be safe. But particularly in the beginning, they're not going to be cheap. So the first markets are going to be markets that can justify the cost because you're doing something really beneficial. It may be Medevac. It may be Oregon. One of the big applications is Oregon delivery. So for beta, the big funding is this is the biggest organ delivery outfit. So they're going to fly organs. There's some advantages, you know, on some freight things. So again, these will be applications where the the performance justifies the high cost and then it'll get it'll get cheaper over time. But I think you're right on it's it's don't believe all the prices you read. All right, thank you. And I think we have another question in the front. So my question kind of pertains to risk and reliability assessment, especially for fully autonomous systems. Professor Caldwell, you mentioned that we have these theoretical low altitude systems like air taxis and delivery systems. Would these fully autonomous systems pose any additional challenges and the risk and reliability assessment of these systems over a more manual mechanical system and then kind of a follow up with that Professor Hansman, you mentioned in a con ops that we have an off board human operator. Would this neglect any of these additional challenges, if any? Well, I think one of the problems that you may be referring to is that we've got remotely piloted, unpiloted pilot in cockpit and trying to understand what are the risk profiles of what let's say intent communication between those different models. Just think about on our campus, we've got these little robots moving around. Fortunately, they're not very fast and they're not very bright and they're not likely to hurt us. And even if they completely break up, they're not going to fall on anybody. Okay. Being able to project what the risk profile is for one of these things flying around and we don't and you won't always know if it is remotely piloted or or completely autonomous. So it's very hard for someone else to figure out what the failover mode is for the other thing that you may see. And if you're trying to scan for five or 20 or 50 other things and trying to guess what they're likely to do, not being able to understand what their intent or the source of their intent is becomes a very difficult, deeply uncertain risk profile. I think that and again, I'm not sure I fully understood, but I'd say a couple of things. For the overflight, for the UAV overflights on the population, the ground, the reason why we do fly at 400 feet is because actually, let me step back. Right now, what we do is we segregate the unmanned airplanes from the manned airplanes by and large. So the low altitude is chosen because that's below the altitude that normal airplane operations are. So normally, you're not allowed to fly lower than 500 feet because you're too close to people. And that's what set the 400 foot cap for the UAVs. The limit of 54 pounds in a small UAV was actually set by the risk of passenger people on the ground. So under assumptions of some UAV randomly colliding and going, you know, we're actually involved in some of those calculations, you sort of figured out whether you're an acceptable level of safety. So it's considered, you can argue whether it's right. I think as we get to higher densities, I don't actually care about UAVs crashing into each other. Okay. So NASA had a big program of things to sort of solve that. You know, nobody's going to pay a lot of money, you know, the $200, $300 an hour to prevent UAVs from crashing. They're just going to take the risk. So they're either going to be good enough or they're not there. But lots of people, everybody cares about an airplane taking out a commercial airliner. So you're not going to be allowed to do something that would pose risk to that. So our job in terms of conceiving the system is to come up with systems by which we can guarantee everybody's safe enough so that commercial airplanes can stay safe. We're still allowed to operate. If he wants to deliver the donuts under the flight path to Indianapolis. Sorry, man. That mark is not available. So you're going to be restricted from so the places you can't you can't fly. So it's going to be a system that's designed and remember around the world, the FAA in the US, but the Airwardness Authority has access to the airspace. So you're going to have to convince them it's okay to operate your airplane in a safe way. So I think it's it's totally what we're thinking about. But I think there are things in process. I'm not sure I fully addressed your question. Yeah, I was mostly thinking towards the design and assessment conceptually when, you know, we have this system that is more fully autonomous. So it's mostly running on software and programs versus having a human in the loop, which with the conups that has a human on the ground, they can interject and take over when there's a fault in the program. But trying to predict the failure rates and the reliability of an autonomous system over more of a predominantly manual mechanical system. If there's any significant differences between the reliability and risk assessed with between fully autonomous and having a more manual. We've seen that even with the autonomy that we have in commercial airplanes today. When we went to the airbus and in Boeing sort of advanced cockpits, and Barry knows this, we created a whole new class of failures that were not anticipated or confusion with the part of the crew. I think we have to be ready for the same thing to happen as we inject these new systems in. This is typically in safety analysis is what we see as an entry into service blip. So we have to monitor and this is part of our safety thing is how do we monitor as we enter something into service to make sure it doesn't go really unsafe, right? So so I think it's a totally legitimate concern and we have to watch for that. It's worth thinking about that. And how much of it can we pick up ahead of time in simulation and design? That was thank you. That was mostly it is how could we actually simulate something like that effectively because it's like a newer technology. It's kind of shifting towards a more fully in their techniques. There's human and loop testing. You know, so you sort of do that. There's agent based models. There's, you know, so you you have to sort of think through what the risks are, right? And then figure out how you're going to address and quantify them. Thank you. I think we have another question in the back. So there's been a huge push for sustainability in the commercial aviation space sector. So I'm wondering and it seems like there's also been a push to return commercial I guess commercial travelers at supersonic speeds. I know like the company boom is specifically and then even pushing that past that to hypersonic. Well, there's a lot. There's a big sustainability hit when you do that. So how do you balance those two aspirations? I have a personal opinion, but yeah, I basically don't think that the supersonic is credible and I don't think it's particularly environmentally and ethically. So we've looked at it. I think it's you know, when the Concorde was flying, I think we didn't appreciate all the environmental impacts, but those airplanes are really dirty airplanes. And so you have to ask yourself, what is the what is the social value of having a really rich person get to their meeting faster and how much is it? And I think we now appreciate some of the environmental impacts. It's hard to justify going that far again for social defense for defense missions.  Even even with potential advancements, with getting those potentially like more sustainable, it's just the the benefits now aren't worth exploring those options. It's totally it's only worth to explore as a research standpoint. Totally totally there, right? Because but you know, my hope would be what you would learn and thinking about that would apply across the system or generally to make the whole system better. But but I think you know, the the supersonic thing you know, and we can have a whole dialogue about supersonic in whatever. I won't you know, everything is a trade off on on cost and benefit. So what is the benefit I'm getting from this capability, supersonic capability? And what is the cost? And those are really expensive airplanes that would be hard to be safe enough to be safe, which have to get exemption on the noise footprint on take off, which have to get an exemption for the noise from the sonic boom, which would then fly at higher altitude where they have an higher impact into the ozone depletion effect, which burn five times the amount of fuel that you would have on a transporter plane to save two hours. It's just the trade to me just doesn't make it. Thank you. I think the cost of this like one flight one seat per flight for the Concorde was ten thousand dollars. I was actually telling Dan to say so we did an analysis 20 years ago or 15 years ago on supersonic business jets with Gulfstream. And we looked at the history of the Concorde when it was flying when the Concorde flew. I used to fly over New York all the time when the Concorde flew. It would fly one cycle a day. One of the mission routes was, you know, New York to London. So go over once and come back. So every time you flew over JFK, the Concorde, you'd see it was beautiful. You'd see it on the ground because it was sitting there because it sat on the ground most of the time. OK. Right. And then when we looked into it, I can't remember the sea load was like 60 passengers. We looked at how many people were willing to pay full fare to fly Boston to New York. It turns out it was about six a day. So there are people who need to want to be in New York in the morning, fly to London, have their meeting and be back for dinner. Right. But there's not a lot of them and they don't fly every day. So there's not a huge demand. One other thing on the supersonic airplanes is if you look at it from an airline standpoint, it's very hard to put together a network of supersonic airplanes that makes sense. So on most commercial airplanes we fly them, you know, between 14 and 16 hours a day. So we put together networks where the airplanes are busy. The problem of the supersonic airplane is it gets to, you know, let's just say you could fly to Tokyo. You get to Tokyo at a point when nobody wants to fly back so the airplane has to sit there. So it's hard to put together those networks.  There are a few rich people who would buy them if you could make the airplanes. But I think from and they would really require a new engine technology to be credible. So in order to get there, it's it's a real push. I'm sorry to be so down on it, but it just, you know, when I think about the challenges we have in aviation, it's not where I would spend my buck. Thank you. So recently, you know, with the push for electrification and UAVs, that's really been at least what I've seen the main driver behind this urban air mobility movement. Why now? Why not with, you know, the helicopters of previous generations? And why not just make those helicopters autonomous? Why spend the time to develop all new vehicles? Jet packs. Where am I going with this? The urban air mobility movement is at least seventy five or eighty years old. There have been people talking about jet packs and personal mobility even before World War Two. The question was, was there a viable technology that could do that without you putting serious explosive hypergolic cryo on your back? OK, so, you know, and I don't want to do that. So I think the urban air mobility movement is basically sort of like Jules Verne saying let's go to the moon and then it taking another almost hundred years to say, oh, yeah, we know how to do that now. So the desires, I mean, that's what science fiction gives us is the ability to think about a future like the supersonic or something like that and say, OK, can we do that? How do we do this? Should we do this? I would say two other things. Well, one is science fiction. I mean, the Jetson car was always the right. OK, but there was a convergence of two things. One is the Uber effect, which is people suddenly realize there was a way to do on demand that was reliable. OK, so on demand mobility became a thing. But then the whole push for urban air mobility was really because of the limitations of the battery technology. So there really wasn't much. You know, you could build an airplane, but it only had a range of 25 miles. So what is the mission you could do at a 25 mile range that would make sense? And it turns out taxi cab rides are it, right? So so I think that was that pulled together in the people who who pushed that originally from NASA were really driven by looking for again, it was a technology push, looking for a mission, not a requirements pull. And I I said exactly the same thing at the time, which is, you know, if you're really if this is such a great market, why aren't people flying it today in helicopters? By the way, there was a time in the seventies when people did do helicopter missions. OK, but it it got run out by noise reasons and a series of accidents. Tell you one sort of anecdote that used to be able to fly from the Pan Am building in New York to JFK for like twenty five bucks or additional to your feet, which was great. OK, so you would do that. And they were doing it with Sikorsky's, I think. So the land on the top of the Pan Am building. So they actually had an accident. There was a wind. There was a dynamic roll over. The helicopter fell off the building into the street and killed a woman on the street in New York City. So as a consequence of that, it's illegal to land a helicopter in Manhattan. OK, so that and you say, well, but there are heliports in Manhattan. It turns out, if you look carefully, the heliports in Manhattan are actually in peers over the water. They're not in the land in Manhattan. OK. So those are the kind of things that that that happened. So this is one of the miracles that would have to occur for urban air mobility to really reach this vision that people had is suddenly you'd have to have all these facilities all over the place that will be very hard to get into each of the neighborhoods due to local licensing and all kinds of things that go on. And it actually wasn't just New York, but also scheduled helicopter service on a very frequent basis out of San Francisco as well. So you're exactly right. We we did do it with traditional helicopters. But and actually, as I understand it, some of the celebrities will go from their home G.A. Airport to, you know, LAX to catch their international flight by helicopter, although that's certainly not scheduled commercial service. That's private general aviation. So and that and that is the killer app for urban air mobility when we look at it, which is going to an airport, right, which means which turns out from a system standpoint, remember, we're talking about the the airspace use between commercial transports and in the in urban air mobility. That has to be worked out at that at that nexus. And it's they don't want to be shutting down landings that JFK to allow, you know, some helicopter in there.  Thank you. We have one more in the back. Hello, I have a question. So traditionally on commercial aviation, when there's a contingency event, they usually do the contingencies managed through traffic traffic management, air traffic control. But now that we have all the autonomous systems, let's say UAM or UTM, that according to the con ops, that it's the is the service providers that helps resolve the situation. But how do we how are we prepared to transition from the purely ATC to service providers operated contingency management? Do you have anything to say about that? So that that's a great question. And that's so I don't know which kind of you're talking about, but there are a lot of con ops that were proposed that actually didn't make much sense because they didn't address those problems. So there was this notion of this distributed system and whatever, but you really have to structure the authority of who has access to the airspace, who does the approval and things like that. So I think that that's that's one of the reasons why I thought the wiskops was pretty good, because it's sort of thought through that a little bit better than some of the other ones. So they just separate out the air traffic control from the service provider and have a pretty good architecture. But it's it's totally legitimate comment. OK, and I mean, there is a real challenge on all these things when you have a con ops, you have to figure out all of the transitions that have to occur to make it reality. So who has to give up airspace? How does the system work? Will everybody buy in? And that's a real challenge. Yeah. Yeah, one thing I was going to comment on is for airports, there's been a move to have an integrated operation center where we can have all players close together physically. They work together on a day to day basis. So when you do have an emergency, you can step in and you can manage it more effectively. So now if we're adding a remote operation center, that obviously lends another degree of complexity to it. So again, probably scaling the system and identifying a limited number of service locations at first would be an important step to identify sort of the role and how that works. And one other aspect and all that, again, which is the big challenge is when you have competing agents and who has priority. Right. So that's the fundamental issue. Who makes the call on who goes first? Well, and I think the other point we've spent a lot of time today talking about commercial, the overwhelming number of airports in the U.S. are not scheduled, commercial, towered, all the big heavy players. So you would start asking what's the role of the community airport? I can start thinking about a lot of these smaller vehicles, different missions starting out from like a Columbus as a community airport or something like that. There are a lot of other capabilities here. But then the con ops has to be able to handle that level of operations as well as the Indianapolis Midway O'Hare sort of operations. And so layering the con ops for the different classes of service for the different classes of vehicle starts to be, I mean, you're in essence redesigning the national airspace. But that's also where it gets kind of exciting because we have a whole different role for some of our smaller airports. A few years ago, United actually put out a press release that for some of their small electric aircraft, one of the, you know, they describe the sort of the target market and they use the example from our Purdue airport to Chicago, which wouldn't that be fabulous? And of course, that might have been some of our graduates who are giving some PR. But again, you're right, it does change it. But that's where it gets exciting in terms of, wow, we can really tailor our air system to meet the needs of the nation. And we have another question in the back. Go ahead. Good afternoon. I have questions about wanting to follow up on the topic of urban air mobilities. So I think looking at these UAM startups, these startup aircrafts take so many different shapes and forms. And some of them have the capability, or some of them have the capabilities, also the failure modes as a traditional aircraft, not to say I'm losing a propeller, losing an engine. But there are also some of the capabilities, also the failures that the traditional fixed wing aircrafts or helicopter aircraft doesn't have, let's say, transition between cruise and hover. So my main question is one day there will be accidents. So what are the challenges for the engineers to analyze and learn from these failures when they happen? How do we count for these differences between the conventional and the new aircrafts? Yeah, I mean, I think this is the crux of what we've been discussing a lot today. There are new airplanes, there are new failure modes, some of which we will anticipate and design for. And we'll find them, by the way, in flight tests in the whole development process. Anytime you make a major change of the system, then you also have unexpected properties, emergent properties. So there are probably failure modes out there that we don't anticipate. Those are some of the things we talked about. Those will be the entry to service effects. We will be monitoring them very closely. One thing we haven't done well enough is to, which we're trying to do a little bit more, is to use the UAV, the small UAV system, as a surrogate to look for changes that occur there. But we don't have a way of tracking small UAV accidents or incidents or things like that. We will, on these newer airplanes, have a way of tracking any failures. There will be a requirement to report and things like that. So there will be a process as they come in. And there'll be a very stringent process on certification, which is why it will take longer than some people speculate. Do we have one question? I think our last question. I have an airport-specific question. So I'm from Atlanta. So I'm used to Hartfield-Jackson. But I've read that a lot of the some of the problems with how busy it is comes from them not having a second airport around Atlanta. So I'm wondering what are the pros and cons of adding that second airport and then what are the difficulties that you have to deal with communicating between two very closely nearby airports? Yeah, that's a really interesting topic. Actually, there has been a push to have a second airport in Atlanta. But then, quite frankly, Atlanta pushed back. Atlanta-Hartsfield Airport and did not want that secondary airport. And we see it with other cities as well. I don't know if you know, but there is a third airport planned for the Chicago area. And of course, New York has three airports. So it really becomes an airspace issue in managing the airspace. So that and I guess that's a fair question as we talk about these other kinds of aircraft. We might start to get those issues at other airports as well. So I sort of answered your I didn't really completely answer your question. But I guess I talked a little bit about surrounding issues. I think, you know, again, if this is on commercial transport airplane, if you look back, some airports that were getting significant delays in the 80s, you saw the expansion in Chicago as an example. But in Boston, we had Manchester and Providence show up. Typically, Southwest Airlines was the one who introduced those kind of expanded services. I think the problem there is that that's fine if you want to go to that basin, but you can't like transfer flights and whatever. So there isn't a real efficiency of the consolidation, which is, I think, why Atlanta went there. I would like to circle back, though, to what's come back on the discussion of a lot of these advanced air mobility, urban air mobility, want to go to the airport. OK. And it turns out under our current regulations, it's actually fine and visual a nice day. So the helicopters or the AM can come in as a way that are not interfering. If the weather's bad, OK, there's a three mile separation and it turns out that legally you can't do it. So we need new rules in order to get those AM airplanes in in a way that don't interfere or slow down. And I'll give you one other anecdote. We remember talked about priority. The highest priority airplanes in the system are Medevac airplanes. OK, they actually have priority over the over the president. OK, Air Force One is number two. OK, Medevac is number one. OK, so if an airplane, if a Medevac helicopter is flying into Boston, I'm sorry, Mass General Hospital, that's within three miles of the final approach course to Logan. So if that occurs in instrument conditions, they have to shut down Logan till the helicopter gets into the hospital. Now they've worked it out. If the helicopter, if they can get below the clouds, we'll do it and then they'll they'll cancel and not shut that down. But that problem has to be solved in instrument conditions in order to open up the air mobility access to the airports. And I think it will be, but that's we have to work the rules. A lot of implications to that. And we definitely appreciate all the questions and thank you so much.  To the panel. And also, thank you to Brandon, Dr. Sun, Dr. Laveson, Dr. Hansman, Dr. Caldwell and Dr. Hubbard. Thank you. And thanks for sticking with us for the panel. I'm sure the panels will hang out for a few more minutes if you want to chat with them. Otherwise, enjoy the rest of your afternoon. Thank you, everyone.


Air Force Global Strike Command Airmen conducted an operational test launch of an unarmed Minuteman-3 ballistic missile on August 11 to demonstrate the readiness of the U.S. nuclear forces and provide confidence in the lethality and effectiveness of the nation's nuclear deterrent. Today's test launch is a randomly selected intercontinental ballistic missile pulled from F.E. Warren Air Force Base, Miami. The missile was transported within 1,300 miles and reassembled at Vanderbilt Space Force Base, California. The ICBM was equipped with a test reentry vehicle and traveled approximately 4,200 miles at a speed of more than 15,000 miles per hour to a test range near the Quadralina Tull and the Marshall Islands. The ICBM test and evaluation program helps validate the reliability of the nuclear umbrella our allies and partners rely on, eliminating the need to obtain their own nuclear weapons to counter potential adversaries. The 50-year-old Minuteman-3 is based in Colorado, Montana, Nebraska, North Dakota, and Miami and will be replaced by the ground-based strategic deterrent program of record. Reporting from Vanderbilt Space Force Base, I'm Michael Stonesiper.


can set up a few exercises and check it out for yourself. In cycles, I have a number of exercises and many of them are pretty heavy, there are 33 exercises. So, I do not expect you to do these immediately, but in the time that you have today evening and tomorrow morning if at every center there are at least 15-20 people, if they do a division of labor and at least go through each problem and see lay it out, do not do numerical that will take a lot of time, but lay it out and see that they are confident of proceeding with the numerical that will be a job well done. I will now take questions. So, I am first going to JNTU Hyderabad. So, Dr. Brahmara again, good evening and any questions from your side, over to you. Good evening sir. There is one question from the participant Mr. Prasad. I hand out the mic to him. Sir, good afternoon sir. We will consider isentropic process as a ideal process, but in case of a compressor, the work is less than isentropic process. The ideal work is less than in case of compressors, when compared to isothermal process and isentropic process, what is the reason sir? Can you explain it? Thank you, over and out. You said over and out. So, I assume that this is the only question that you had to ask. Anyway, the question asked is the work done in a compressor, when you do the compression isentropically is higher than the work done in the compressor, when you do it isothermally. But in my opinion that the two processes are not comparable, because the end states are different. If your requirement is to compress from say P naught ambient pressure, ambient temperature, compress the gas and if you want to compress gas also at the ambient temperature T naught, that means the initial and final states are isothermal. Now, you have a choice that either you do a direct isent isothermal compression in some way from state initial state to final state, in which case the compressor outlet is the state you want. In the second case, you do first an isentropic compression, that means you will be increasing the temperature of the fluid and then you will be cooling it back to the final state that you want. So, naturally if you have to do cooling, that means you have to extract energy and that means in the isentropic compression you have already added that much extra energy. So, this explains the difference, but you should not say that isentropic compression is more efficient than isentropic compression, because the cases are different. When you do isentropic compression, then if you want to go back to a situation where you want higher pressure, but the same initial temperature, then you have to do cooling. So, that means you are taking a round above truth and if you want that state, you go directly through isothermal compression, then you are directly approaching that state. So, the isothermal compression is a direct truth, it will naturally consume less power than the isentropic compression and cooling, which is a rather indirect truth and hence will consume. Now, let me go to some other center, KJ Somaia Mumbai, Somaia over to you. Hello sir, my question is, we normally talk about constant pressure gas turbine like based on Brayton cycle, but in some textbook I have seen constant volume gas turbine also. So, we normally does not talk about much about this constant volume gas turbine. So, please elaborate on this. Thank you, over to you sir. I would not come across an idea called the constant volume gas turbine because if you have a flowing system, in a flowing system it is very very difficult to create a constant volume process. So, this constant volume gas turbine is something which is may not be an anathema, but something which is odd at the idea of a gas turbine. There may be something called constant volume gas turbine, but I have not come across anything like that. Over. No sir, actually in classification they have mentioned, but they have not given any description about that. So, in the book of Professor Dhamkundwar, I have seen that. Over to you sir. Well, I have not seen that book and if we had just listed it, we can list 10 different things if we does not have to describe it. So, I do not want to comment anything more on that. Over to you. Any other question? Over and out. Vajchan called it sangly, over to you. Hello sir, my question is about Rankin with regeneration cycle. In that case the process 2 to 3 and 6 to 3, these are the mixing processes which should be highly irreversible, but we have shown with a continuous line, is that approximation is good or not? Over to you. Yes, from a purely thermodynamic point of view, showing 2 to 3 and that is the mixing process, you can only show by dotted line saying one stream goes in at 2, another stream goes in at I think 6 and the mixed stream comes out at 3. So, I think you are right, it should be shown only by dotted lines. Over to you. Sir, over and out. PSG Kohimbatur, over to you madam. Good evening sir. I have 2 questions to ask sir. First one is in which engine the Erikson cycle and dual combustion cycle is practiced and the next one is regarding the sterling cycle, that you said that sterling cycle is used for cryogenic refrigeration, whether it is used for liquefaction of gases to produce cryogenic fluids like liquid, oxygen, helium, hydrogen like. Over to you sir. I will answer the second question first. Yes, sterling cycle, if not the basic sterling cycle with minor modifications so that it can be implemented properly is used and is one of the workhorse cycles, that is the mainstream cycles for refrigeration and one of the mainstream cycles for liquefaction of gases. So, whether you have liquid nitrogen production or liquid oxygen production or liquid hydrogen or liquid helium production, a significant load of that work is done by implementing sterling cycles. So, what you have said is right, the sterling cycle is used for liquefaction of gases. The first question was that Erikson cycle and dual combustion cycle. The Erikson cycle by itself is hardly ever implemented in practice, but I showed you and I mentioned that you can have a Brayton cycle with reheat, intercooling and regeneration and I will leave it to you as a exercise to show that if instead of one reheat in which the turbine is split into two parts and you have one reheat in between. If you say that you split the turbine into a number of small parts and have small small reheats in between. Similarly, the compressor can be split into a number of small parts and have small small intercoolers in between and you have a regenerator. If you really implement this, it will be a complex scheme, but if you really implement this, then you are coming somewhere near the Erikson cycle implementation. It becomes very complicated and that is why an Erikson cycle is usually or why it is hardly ever used in practice. About the dual combustion cycle, remember that the constant volume combustion in an auto cycle, the constant pressure combustion in a diesel cycle and the dual combustion cycle where partly you have at constant volume, first you have at constant volume and then you have at constant pressure. These are approximate models for what actually happens in an engine. In an engine whether it is petrol, whether it is diesel or whether it is any other type of IC engine, the combustion does not follow any of these idealizations. Depending on the situation, one can approximate for example, for light fuels like hydrogen, CNG, LPG up to petrol. We can say that the combustion is so fast that you can reasonably approximate as a constant volume process. For diesel whether it is a constant pressure or dual, that is a choice of detail, it is left to you. The actual thing is for look at an actual indicated diagram and you will find the actual thing is neither of the three, neither constant volume, neither constant pressure nor an appropriate mixture of the two. So, over to you. Any more questions? One more question, sir. We are using a representable diagram for representing compressor and turbine, sir. Is there any other specific representation for pump or any thermodynamic devices? Over to you, sir. There is no standard as such. We show an expanding trapezoid for a turbine. We show a reducing trapezoid for a compressor because that is the typical shape of a gas turbine or a steam turbine or a gas compressor. For a pump, usually you show that condenser, you have that sigma type of diagram. That also is a very common industrial practice. For pumps, either you show a circle with an arrow in it or circle in which the inlet pipe goes up to the center and the exit pipe, exhaust pipe comes as a tangent representing some sort of centrifugal pump. But since here we are not saying that it is a centrifugal pump necessarily, circle with an arrow is good enough for a pump. For heat exchangers, etcetera, there is nothing really very special. So long as you create a very simple symbol which is understandable, I think that is good enough. These are anyway schematic block diagrams. These are not actual drawings of the exit pipe. Over to you. Over, sir. Thank you. K. K. Wagnashik, over to you. Hello, sir. My question is on isobaric heating and cooling in open system. You have shown that isobaric heating and cooling happens only in open system. Why it is not in closed system? Isobaric heating and cooling. Over to you, sir. I did not say isobaric heating happens only in the open systems and not in a closed system. We have isobaric heating and cooling examples in many of our exercises in closed systems. I said that it is easy to implement isobaric heating and cooling in an open system. All that you have to do is let the fluid pass through a pipe or a number of pipes, provide reasonable area so that the velocity is low and the pressure drop is small because when a fluid is flowing through a pipe, there will be some pressure drop. So, see to it that the pressure drop is small so that we can still argue that our process is near isobaric, if not exactly isobaric. And then heat it up by burning something on the outside or making another hot fluid flow on the outside. Cooling cool it up by, you know, submerging that pipe in another cold fluid. That is all I said. Over to you. Hello, sir. Another question is when we extract steam at higher pressure, whether it results in reduction in entropy generation? Over to you, sir. I think you are talking about the extraction cycle. I have not done the detailed calculation, but notice that since the overall efficiency increases, I expect the total entropy production of the cycle to go down a bit, but I have not done detailed calculation. Maybe one should do it from that point of view and see exactly how does the overall entropy production behave. Maybe there are some contributions which will go down, some contributions may go up, but my feeling is overall the entropy production is likely to go down. Because if you have the same source and the same sink and if your overall efficiency is going up, at least grossly that means on an overall basis entropy production should be going down. Over to you. So, one more question. Can you please explain us in detail the throttling process which occurs in refrigeration or in expansion of steam? So, I am going to NIT-3C now. May I request every one of you including NIT-3C to restrict yourself to maybe one major question? So, over to you NIT-3C. So, good evening sir. My doubt is about temperature measurement by using constant volume gas thermometer. There is given that relation like theta is equal to 273.16 degree Kelvin into P by Pt by putting reference state as a triple point of water and he is calculating the temperature of the saturated liquid at one atmosphere for different triple point pressure references. He is plotted the theta values and he said that as the triple point pressure reference tends to zero the temperature is arriving at 373.15 degrees. He said means how should he is decreasing? Can you provide me that reference from which you are talking about? Over to you. Sir, from PK Nag, I have read this information sir that is about consistent volume gas thermometer. He said that as limit Pt tends to zero the theta is the approaches to 373.15 degree Kelvin. I think what Professor Nag is talking about is he showing the behavior of various constant volume gas thermometer. Remember that we talked only about the constant volume gas thermometer using ideal gas as a working fluid and when you use various real gases as a working fluid their behavior is not really ideal but their behavior tends to be like an ideal gas when the pressure goes down. So, you work those thermometers at various pressures lower and lower pressures and as you approach lower and lower pressures as you approach zero pressure that means very low pressures the behavior of any gas will be like that of an ideal gas and hence that ratio which is shown there approach the 273.16 Kelvin ratio. I think that should explain it. I do not have Professor Nag's book with me just now but if you really insist I will find it out from it is there in my office somewhere I will extract it and find out and we will discuss more about it. Over to you. Hello sir, one more question regarding work ratio. Sir you defined work ratio as the work consumed by the compressor or pump to that work produced by the turbine but I follow a book Unisanger in that book it is specifically defined for the gas turbine that it is called as the back work ratio. Sir tell me what we should use back work ratio or work ratio? Sir is it same or different? Over to you sir. It is the same you may be calling it as a back work ratio we simply call it work ratio it is a slightly different term it means the same thing. Let me go to NIT Calicut now. NIT Calicut over to you. Hello sir, my question is this cycle has maximum pressure compared to auto diesel and dual cycle. And my second question is why dual cycle is called as limited pressure cycle? Over to you. As I understand the first question was which cycle has the maximum pressure auto diesel or dual. Difficult to ask because in auto cycle the maximum pressure is near the end of combustion but the compression ratio is small. So end of compression the pressure is small but the instantaneous pressure at the end of combustion is pretty high. In case of diesel cycle the compression ratios are large of the order of 16 to 20. So the pressure at the end of compression is high but after that during combustion pressure may increase to some extent. So I think it will my guess is the two things are comparable but diesel is likely to be a bit higher but not much higher. And whether I think you can always find out high performance petrol engine as used in may be F1 racing cars where the maximum pressure may be higher than some other typical diesel cycle type of engine. But I think generally they will be comparable if at all diesel cycle may have a slightly higher pressure. Though I do not know what the second question was can you ask it again please over to you. Hello sir, in the first digital I asked in the reference to diesel engine also auto diesel and diesel cycle I asked it earlier. So compared to diesel and diesel it is having more pressure maximum pressure. See the pressures and parameters of each cycle depend on its application. And for Joule cycles, Brayton cycles the pressure ratios are in the pressures are much lower than what you get in auto and diesel cycles. But otherwise the cycles are not directly comparable to each other. The pressure ratios and maximum pressures are likely to be unrelated to each other. They will depend more on the application and the working fluid. Truba college Indore over to you. What is the need of Brayton cycle when we are Carnot cycle as an theoretical cycle over to you sir. I think I mentioned that that Carnot cycle is a theoretical cycle. It is very good for thermodynamic analysis but it is very bad for implementation. That is because the for a given size the work output will be pretty low. Even if you have everything ideal because the mean effective pressure will be pretty low. Second thing the work ratio is so horribly near one that I doubt that a pure Carnot cycle will ever be operated in practice. And that is why we are looking for alternative cycles and there are good alternatives you know Brayton, Otto, Rankine and all these cycles are very good alternatives to Carnot. Except that on paper they may not have the same efficiency as Carnot for the same temperature limits. The fact is that we are engineers we want to finally have an engine which works and which is not exorbitantly costly. So we will say that look with all due respects to Carnot cycle which we will chew apart in thermodynamics when it comes to actual practice. We will work with Brayton, Rankine and other cycle as needed over to you. So VNIT Nakpur over to you. Good afternoon sir. Our question is with reference to the Mollio diagram. We find that the isentropic expansion of 20 bar and 500 degree Celsius steam up to 0.1 bar and the isentropic expansion of 100 bar and 500 degree Celsius steam up to the same pressure that is 0.1 bar results into almost comparable enthalpy drop 20 bar, 500 degree Celsius into 0.1 bar and 100 bar and 500 C up to 0.1 bar is resulting into comparable enthalpy drop in kilojoule per kg. So why should we go for high pressure turbines? Over to you sir. You are only looking at the enthalpy drop in the turbine. You should also look at the enthalpy rise which you need to provide in the boiler. Calculate the efficiency of the cycle as well as the specific output and then decide what is good for a plant. And finally remember that going to a higher pressure means a thicker equipment because you have to have pressure vessels and pipelines that thick. But if it means more efficiency and more power output that is an attraction. Finally it is the economics of setting up and running the plant which decides and from that point of view today there are one optimal or near optimal turns out to be around 150 bar and roughly 570, 580 degree C and there is another rather costly optimum but that is at the supercritical pressures around the same but sorry temperatures around the same but pressures of roughly 250 bar. Attempts are being made to find out whether something like 350 bar, 750 degree C will be feasible but those are still design attempts we do not have a working plant at those conditions today. Over to you. Point of view who relates work output to the enthalpy drop he would certainly ask when 20 bar, 500 steam is giving the same enthalpy drop as 100 bar and 500 degree C S. Yeah student may ask that but ask him to do the complete cycle analysis and then discuss this further. Over. I think that is the end for us today.


11 Psychological Tips for Staying Focused Whether you're a student, professor, entrepreneur, or employee, people of all walks of life and ages struggle with keeping focus. In this day and age, with new technologies and life becoming more busy as we grow older, distraction surrounds us. Here are some tips on how you can keep concentrated more easily. 1. Plan out your times Start by figuring out during which times your focus is at its best. Maybe it's right after dinner or in the first hours of the day. Well, arrange your schedule so that you do the most important tasks during your most efficient hours. 2. Train your brain It's become the norm to multitask almost an autopilot without putting much thought into it. Start by training your brain to put all effort into one task. Put away all distracting devices as well. It doesn't have to be for longer than 10 minutes. You can work your way up as you go. 3. Let it flow This is entirely dependent on what works for you. Sticking to a strict schedule will slow down your efficiency. If you're working very well, you might want to extend your working time. At the same time, if you can't seem to focus too well, step away from your work for a bit to clear your head. 4. Sleep well, eat well Your productivity is proven to increase when you have slept well. Not to mention, focusing while running on an empty stomach is extra hard. Having 15 minutes of full uninterrupted concentration is much better than 30 of exhausted studying. Don't forget to take time to take care of your needs. 5. Make a list Make it clear to yourself what you want to accomplish in this session by writing it down. Being specific is key here. Having a clear idea of what you have to do will not only make it easier to manage your work in separate sessions, thanks to the visual map it will be less likely for you to be distracted. 6. Repeat, repeat, repeat Studying a subject for a couple of 30-minute sessions is more effective than studying for one long 3-hour period. This requires a more careful distribution of your time. If done right, your productivity and focus will improve. 7. Clear up Once you're ready to start a new task, it's time to leave all potential distractions from your previous task behind. It's easy to catch something you missed and want to go back to do that, but you need to move forward. Write down what you need on your to-do list and go back to do it later. 8. Pay attention to your habits Pinpoint what is exactly that keeps distracting you. Maybe it's your phone, your laptop, or the fridge that is preventing you to give your full attention to the task at hand. Once you have identified the source, you can deal with getting rid of it while you work. 9. Time's up You don't always have to work until everything is finished. Taking breaks in between long, tedious work sessions will help keep you motivated for the time you have left. 10. Separate relaxation space and workspace Have you ever tried working in bed and it just made it so hard to focus? Designating a specific space to work will let your brain know when it's time to concentrate, in addition to making it easier to fall asleep when you've finished. 11. Finish A lot of students will study until late in the evening and then go straight to bed. However, it's better to end it by doing something you enjoy. This gives your brain an opportunity to cool down after a work session. Do you have any more tips that help you focus?


What's going on everyone Sam here with late in sports cards ripping 22 23 a Panadiprism basketball hobby four box break number 15 pick your team style We've got list of names in our teams here But he would be with the Pacers see Wong with the Warriors Dale F Bulls and Raptors David F with the Jazz Edward P Lakers Eric W Thunder Magic Evan H Spurs Jeff M with the Hornets cabs nuggets Clippers and Sixers Jeffrey H Kings Jeffrey C with the Grizzlies Joel B Mabs Josh D Hawks Justin E Rockets Karl P. Nicks Mark S with the Heat Patrick Z Nets Raquel B Bucks Sean M. Pelicans Tom B. Pistons Saj H with the Celtics Wyming H wizards Wenshin S with the Timberwolves Blazers and Zachary A with the Suns Good luck here guys. Let's do it Yeah, eat eight stitches On the webbing of your five stitches on the webbing your hand does not sound good.  Just watering his plants and he cut his hand on a base Silver lamella ball There's Jason Richardson for the Warriors On the signatures autumn Nice one there Vince Williams Ravia McCollum purple Josh Hart to One no to 99 feeling green quiet Leonard silver Kiehl's Tyrese Martin, there's James Hardin red wave for the Sixers Giannis Devin Booker Dirk Nowitzki Jay Nivey Zion Williamson Silver James Hardin Brown silver Jonas Valenshunis Roddy J Val again Christian Coluco for the Raptors Patrick Baldwin Tony Parker Mark Williams Red wave on Yucca Okangwu James Hardin Silver Aaron Gordon Pierce Ryan Rollins Red wave Jake Liravia For the Gris Clayson Daniels John Collins Pulsar TJ Warren Ben Wallace Charles Barkley Orange wave Quentin Grimes for the Knicks to 60 QG Julius Randall Montemore Silver Tarry Eason Roby Jason Kidd Silver Donovan Mitchell Fearless Yolkic Giannis Hyper Branham Rookie Marys Dotomire Keegan Murray Silver Prismatic DeMar Wacka Lottery Palom Silver Patrick Baldwin Rookie Jabari Smith Rookie Little Chamberlain And Terry Eason on the Rookie Auto Nice one there for the Rockets Congrats Houston Ben Simmons Ty Washington Duncan Thurman I know that's what I'm saying illegal They should suspend him for lying He can't play in the first round of the playoffs Silver Grayson Allen Marjan Bochin He's the Boston Strangler He's the Boston Strangler The Tattletale Strangler I got a new prank in today It's Exploding Chewing Gum Try it To 199 We've got A.J. Griffin Rookie Signatures for the Hawks Nice one there, congrats Atlanta A.J. Griffin Steele of the Draft Cole Anthony McGowan's Wilkins Yovitch Silver Jay Neivey Luck of the Lottery Luck of the Lottery Shade on Sharp Paul Pierce Johnny Davis Rookie Tyries Martin Nice one there Atlanta 3 of 10 Tyries Martin Congrats on that Walker Kessler Let's go Josh Gold Tyries Martin Rookie now too Silver Alonzo Duncan Devante Hawks fan connection Right there Red Wave Jordan Jackson Jr Joel Embiid Troll Embiid Pippin Jr. Jaylin Williams Jay Will Go Hawks baby, yes sir Bojan Bogdanovich To 299 We've got Caleb Houston for the Magic Rookie Auto That's Williams, Hyper Rookie Coloco and T-Mac Yellow Border There's PJ Tucker Purple in the 99 The Sixers And Wendell Moore Literally when we're ripping contenders Every Ochai Agbaji rookie to your contenders I think is like a gold No I don't think so Scooter I don't think so Scotty Barnes Red um Power to 75 Trey Young Pat Bev Walker, Isaiah Mobley Helby and Bowman Draft Kevin Garnett to 199 John Jones Payton Watson Red Wave Jason Daniels Sakim the Dream Silver Dane Griffin Blake Wesley Jayden Ivey Luck of the Lottery Bradley Beal Zion Robinson Jabari Smith Red Wave Austin Reaves second year Marshawn Beauchamp Jayden Hardy if it's a 42 year old Tom Brady Photoshopped into an Expo's uniform Pretty funny Silver Trayman Jadon Chirp Blue to 199, EJ Liddell Photo with Tony Dungey Uh oh you freaking moron You just got jingled Send this to three of your friends Slowly jingle them as well Down Terry Even jingled like 10 times today My friend Stopped to come back from Very tough to come back from Blue Ice, Trevor Keels 125 Do you see that picture of Tom Brady and Tony Dungey Together I'll see if I can find it really quick after this pack Ah of course Red Wave Pistol Pete for the Jazz Steph Curry, Dave Yon Mitchell Chet Rookie It's a terrifying picture They just look insane dude Look at this Tom Brady It's just like a regular picture Of them just like They just look weird Like this is the picture They just kind of look like a little scary Yeah a little scary What was I going to say I saw one that looks like It goes Tom Brady and Tony Dungey look like They just poison your food and they're watching you eat it Orange Clint Capella, Swiss Bank It's a 49 Marcus Moore Sr, Chris Muller Yeah it's a It's a scary picture Whoa Red Wave, Rudy Gay Nigelio Kitch Fearless Dwayne Wade, Pulsar So it's that pace of Brady just photoshopped On the X-Bow player Yeah that'd be funny Blue Isaiah Roby 1999 Walker Kessler Silver Nicolio Kitch Fearless Yanis Silver Josh Richardson Palo Rookie Silver Julius Randall Silver Vince Williams Kendall Brown, Kevin Garnett Jaylen Durring Rookie Lucky Lottery Palo Hyper Derrick White Loco Brown and T-Mac Red is Jaylen Williams Nice one there to 2.99 For the Thunder and then we've got Jaylen Williams again J-Dub Go into the Thunder, congrats O.K. See great pack for you there Can't really get much better than that Jeff Green Monu Vendik Matherin And Tyus Jones I'd say like anything number that's not the red Is probably Maggul for him Still like 189 or less Jake Lewin last year I know I wish his signature was J-Dub too Spencer that'd be sweet That'd be so sick Purple Ice, 3-Pow 149 Detlef Schrempf Silver that's going to the Thunder by way of the Supersonics Detlef Schrempf Deandre Hunter Jake Laravia And Trevor Keels Purple, Chris Middleton Reggie Bullock Trey Jones Bradley Beale Yannis Hyper Big Ben Wallace Barkley, Terry Eason For the Rockets Orange in here That is a...Luca Another Luca Orange Pulled two of these now 39-49 Nice one there Pulled 1.30 of the Lucas 2.49 David Davis 50 Fair Oh, gotcha 2.49 Red Kevin Herger 2.99 Dennis Rodman Kegan Murray Red Wave Jason Tatum Obi Toppin Jaden Ivey Poison Ivey Rookie David Robinson Silver Fireworks Chris Mullin Patrick Baldwin Remind me again to tell you that thing I was laughing at earlier I was halfway through the prism case after I told you that Prismatic Steph Curry Keneth Woffin Jr Barry Smith Ty Ty Washington What were you doing in those cases? Oh, we were dialed The Luca Tatum Duel 101 out of Eminence Good God, dude, that'd be insane Dotton Mitchell to 1.99 Scotty Pippen Jr Rookie Otto for the Lakers Dallin Terry Hyper Marjon Bochamp Trey Murphy, Hyper Sony Parker Trey Murphy Red Wave, Spencer Dinwiddie Beninick Matherin, Luck of the Lottery Silver, KCP Rawens, Pete Maravich And the last pack of the break Good luck, everybody, we'll do a quick recap after No points right now Silver, Caleb Jaden Hardy Rookie Hayton and Dallin Terry Let's go, Scott I'll do a quick recap here, y'all Pretty solid overall, I would say Luca Donchich to 49 Gold, Tyrese Martin, Rookie to 10 Scotty Pippen Jr Detliff Shrempf Udoka Azubukei, Caleb Houston AJ Griffin, Terry Eason Jason Richardson and Jalen Williams On these signatures For the Thunder That'll do it for the break, guys Thanks again for the fill, next up, Eminence


In this video, I will describe the process of bone remodeling and define osteoporosis, differentiate among the different types of fractures, and finally describe the process of bone regeneration to repair a fracture. Bone remodeling is a process that occurs throughout the lifespan where new bone is formed by the activity of osteoblasts and bone is also simultaneously being broken down and reabsorbed by osteoclasts. This occurs in order to maintain the proper proportions of bone as we grow, as our bones become longer to remodel the proportions of the bone throughout adolescence, throughout growth, but also in order to repair bone that is damaged if we have a fracture, or to strengthen bone in response to mechanical stresses that are occurring throughout our life. Mechanical stress will stimulate remodeling of bone in order to make bone strong enough to adapt to the load which it experiences. This is a fundamental principle of bone remodeling known as Wolff's law that under normal circumstances bone can adapt to strengthen areas that experience the most mechanical stress. Bone remodeling is also important to maintain blood calcium homeostasis as parathyroid hormone stimulates osteoclasts. More calcium will be released from bone and bone will become weaker in the area where calcium has been released. Osteoporosis is the reduction in bone mass that results in a decreased bone density and bones that are light and fragile, that are more prone to fracturing. Osteoporosis occurs when the osteoclast activity that breaks down the matrix of bone to release calcium occurs at a higher rate than osteoblast activity that deposits calcium in the bone to strengthen bone. This leads to bones that are fragile and light. We can see the example here of the effects of osteoporosis on the thoracic vertebrae where there is normally a curvature to the vertebral column in the thoracic region to help support the weight of the upper body. That weight can lead to compression of the vertebral column and exaggerate the curvature of the thoracic region, a condition known as kyphosis or hunchback, which is more common in individuals with osteoporosis. While both men and women are at risk of osteoporosis, there is a higher risk of osteoporosis in women after menopause. This is because estrogen normally reduces the activity of osteoclasts and as estrogen levels fall during menopause, osteoclast activity increases. There's normally an increase in bone density throughout the early years of life that peaks around 30 years of age and then declines afterward. A variety of factors can contribute to the rate of the increase or decrease in bone density. For example, dietary intake of calcium and vitamin D levels that are available sufficient enough to absorb calcium from our diet so we can get vitamin D that we can synthesize from the sun or we could also get vitamin D from food, especially if it's been added as is the case with fortified milk. Vitamin D is important for the absorption of calcium, so if we don't have enough vitamin D we can become calcium deficient because we can't absorb the calcium in our diet. However, a poor diet with a low calcium level of the diet could also lead to calcium deficiency and decreased bone density. Losses is an important factor because putting a load on our bones, providing some mechanical stress to our bones stimulates bone remodeling, stimulates the activity of osteoblasts to strengthen the regions of the bone that are experiencing the most mechanical stress. Other lifestyle factors include smoking and drinking alcohol that can reduce calcium absorption and genetics is also an important factor. The tendency to accumulate bone mass is something that runs in families and there are mutations in certain genes that can increase our risk for osteoporosis. Nutrition for osteoporosis includes nutritional supplementation with calcium and vitamin D and when possible, exercise to promote remodeling and strength to help maintain bone. However, it's also important to be careful to avoid fractures in osteoporosis, not to over exert or to lose your balance and fall. There are also drugs that are effective against osteoporosis, including hormone replacement therapy in women especially, replacement of estrogen and progesterone can be a treatment in order to decrease the activity of osteoclasts. There are drugs called bisphosphonates, a couple of examples of bisphosphonates are Phosamax and Boneva. So bisphosphonate is a broad class of drugs that inhibit osteoclast activity, but it's a specific chemical classification of drugs. There are other drugs that have been more recently developed in order to stimulate the activity of osteoblasts. Interestingly, Forteo is a form of parathyroid hormone that has a paradoxical effect when injected. This form of parathyroid hormone can stimulate the activity of osteoblasts even though the normal effect of parathyroid hormone released by the parathyroid gland in our body is to stimulate the activity of osteoclasts. In this situation when it is injected it has the opposite effect and stimulates osteoblast activity. Vitamin D is an important factor for the maintenance of bone density and the development of bone because vitamin D is necessary for the absorption of calcium from the diet. We can produce vitamin D if we have sufficient exposure to the sun, UVB radiation is necessary for a step in the synthesis of vitamin D. Vitamin D is synthesized from cholesterol and so it is considered a steroid hormone. We could also get vitamin D from the food or from supplements although there are not many foods that naturally contain vitamin D. Fatty fish is an example that contains vitamin D and some mushrooms contain vitamin D. And then you could also take supplements of vitamin D. You could take vitamin D pills and vitamin D has been fortified in whole milk and so the vitamin D has been added to whole milk as an effort to increase the calcium absorption from that milk and reduce the risk of calcium deficiency and a disorder that results in children called rickets where bones become weak and bend under the weight of the body. If there is not enough calcium available to strengthen the bones during childhood it results in this condition known as rickets. After the precursor form of vitamin D is absorbed from the diet or synthesized in the skin it is further activated in the liver through a process of hydroxylation. So hydroxylation is when a OH oxygen and hydrogen hydroxyl group is added to the chemical and there are multiple steps of hydroxylation that are involved in activating vitamin D. The first step occurs in the liver and then it's subsequently activated in the kidney and this activation is under the regulation of parathyroid hormone so that parathyroid hormone stimulates the activation of vitamin D and increases calcium absorption from the diet. A fracture in which the skin remains intact is known as a closed or simple fracture in contrast. An open or compound fracture is when an end of a bone carries through the skin. This carries a high risk of infection so an open or compound fracture is very serious to make sure that both the bones are reset so that they can heal properly and also so that the wounds are cleaned thoroughly and closed to prevent infection. A transverse fracture is a fracture where the bone breaks straight across the long axis of the bone. In contrast an oblique fracture is when the bones break at an angle that is not a straight 90 degrees relative to the long axis but rather at an oblique angle such as 45 degrees or 30 degrees. A spiral fracture occurs when bone segments are pulled apart as a result of a twisting motion. A comminuted fracture is when several fragments are formed from one bone that breaks into numerous small pieces. An impacted fracture is when one bone fragment is driven into the other. This is also known as a compression fracture from a strong compression force could cause one bone to be forced into another. Last we see a green stick fracture. A green stick fracture is a partial fracture in which only one side of the bone is broken. Green stick fractures are more common during adolescence because the bones are more flexible with a relatively higher amount of collagen and a lower concentration of hydroxyapatite making the bones less brittle and more flexible. In order to heal after a fracture the first stage in fracture repair is the formation of a fracture hematoma commonly referred to as a blood clot which occurs when ruptured blood vessels are detected by platelets and clotting factors which leads to activation of the platelets and clotting factors. Platelets will stick together and form a platelet plug and the clotting factors will lead to the formation of an insoluble fibrous network of protein which helps to reinforce the platelet plug in order to stop bleeding. Then the formation of an internal and external callus occurs where osteogenic cells from the bone membranes will differentiate into osteoblasts and osteoblasts will fill in spongy bone in order to help hold together the bone fragments. There will also be chondroblasts that migrate in and create cartilage to help stabilize the bone fragments. The internal and external callus are a mixture of both spongy bone and cartilage. In the next step the ossification of the cartilage is a mechanism of endocondral ossification so the cartilage is replaced with osseous tissue.  The last stage in fracture repair is remodeling of that callus where the osteoclasts will remove damaged bone fragments and remove spongy bone from the surface and then osteoblasts will lay down a new layer of compact bone around the surface and gradually the bone will be remodeled to have the same overall shape as the original bone.