It started out as a research study to describe what the elements are over design driven culture, but the research took an unexpected turn when the stories of the participants unveiled a disturbing pattern. The day to day reality of design professionals is not what most expect and not in a good way. In this conversation you'll hear everything about the research, about the most important insights and how you can use them to find more meaning and joy through your work. Here's the guest for this episode. Let the show begin. Hi, I'm Marc and welcome back to The Service Design Show. On this show we explore what's beneath the surface of service design. What are the hidden and invisible things that make the difference between success and failure all to help you design great services that have a positive impact on people, business and our planet? Our guest in this episode is Mauricio Manias, a well respected leader in our field who has had many roles, including being the service design professor at SCAD and most recently being the service design director at Truist. We're in a very interesting time as a community. More and more organizations are growing their internal service design capabilities. Sure, we have layoffs every now and then, but the overall trend is pointing up. And as service design professionals, we are stepping up our game by connecting with business leaders and showing that we can be even more impactful. But even though service design is on the rise, it's no time to celebrate as you'll hear in this episode. Because when you look under the surface at how design is adopted within a lot of organizations, you'll see that we still have a very long way to go. There are some systemic issues that aren't just wasting time and resources, they're also hurting careers and the well-being of many design professionals. When Mauricio started having conversations with some very well respected and accomplished design professionals to uncover what a design driven culture looks like on a day-to-day basis, he uncovered through the stories that the pattern that emerged looks a lot more like workplace bullying instead of what one might expect from a design driven culture.  They were the disturbing commonality amongst many design professionals. And findings like this were just the tip of the iceberg. The outcomes of the research have recently been published. So I invited Mauricio on the show to share the most important insights with us. Not to blame or point fingers, but just to get a deeper understanding of the situation design is currently in. So if you stick around till the end of the episode with us, you'll know what workplace bullying actually means from a designer's perspective, what the systemic issues are that are creating this harmful environment and what we can do to take the first step in order to try and fix this. I hope you're ready because this is going to be a very important conversation. So sit back, relax and enjoy the chat with Mauricio Mañas. Welcome back to the show Mauricio. My pleasure. Always a pleasure talking to you. I had a look in the service design show archives and the last time we officially spoke on the service design show was back in, I think it was January 2017. So that's six years ago. And episode number 20 Mauricio. And now we're at 186. Isn't that amazing? Yes, it's amazing. The work you're doing with this series is awesome. Some people call it crazy. But it will preserve a history of the field, right? That's amazing. A snapshot in time. That's true. I haven't looked at it like that. And I think if somebody would have the courage to analyze the episodes, they could make a snapshot of the service design field every six months. And I think we would definitely see some patterns emerging and trends evolving. Yeah. Don't get me started. That would be interesting to do, for sure. Nowadays with AI, I think that's going to be a much more feasible act. But anyways, Mauricio, good to have you back on. We've spoken outside of the show quite a few times as well, but it's good to have you officially back on.  Could you give a quick intro into what you do these days? So I'm originally from Brazil. A city called Florianopolis, the southern part, moved to the United States in 2015 to teach at the Savannah College of Art and be the grad program coordinator of service design and left SCAD joined tourist bank as a service design director and left the bank in the end of March this year, 2023. And I'm working as an independent consultant focusing on service design in AI, taking this time to really dive deep into how can we use AI tools, not so much to provide services, but in our practice. That's my main focus for now. I would love to talk about that topic as well, but that's not the focus of this conversation. I'm really interested in computer aided service design through AI. That is already happening and there's a lot to explore there. Mauricio, before we dive into today's topic, the research, I have a lightning round which you haven't experienced before. I have five questions for you. Just answer them as quickly and as briefly as possible. Just the first thing that comes to your mind. And sooner, the quicker we get through these questions, usually the better it is. And this is just to get to know you as a person next to the professional. Are you ready? Perfect, ready. If you could recommend just one book for us to read, which book would you recommend? Oh my god, you're asking a heavy reader. As quickly as possible Mauricio. The first one that comes to your mind. I would recommend one book that really changed my life was Truth and Method by Hans Gort Gademer. Heavy reading, but it really was important. Usually the heavy readings are the ones that are impactful. So, thank you. Moving on to question number two. Let's see if this one is easier. What did you want to become when you were a kid? I wanted to be an aircraft builder. That's still my hobby today. I love building aircrafts and remote controls. Oh nice.  Yeah, I guess that's an excuse for us to have these kind of playful hobbies. Mauricio, you're now in Savannah, but if you could pick a place to work from anywhere in the world, which place would you pick? I have a strange relationship with Madrid. I'm usually a small town person. I love small towns in Madrid for many reasons. I've been there since I was a kid several times and always surprised me that I've never lived in Madrid, so I actually don't know, but would be Madrid. Messiness and a big city and I don't know, I love Madrid. And the fourth question is what's always in your fridge? Yogurt and ice cream. I can leave out of ice cream. Which flavor? Mostly fruits, mango, pineapple. I'm not very much into the sugary thing, more like this. All right. I could leave out of this. Fifth question, tradition, and again Mauricio, challenge to you. Keep this one brief because I know you could spend a whole episode talking about this one. When did you first learn about service design? I learned about service design was around 2005, 2006, after a project that you went really bad and I was desperate to find a better way to do this. There must be a better way to develop softwares and I found service design and connected to Professor Birgit Maguer and it changed my life. There we go. And the rest is history. Thank you. Thank you for this lightning round Mauricio. Always nice to learn a few things about you that I didn't know personally as well. Let's dive into the main topic of today's episode, the research you did. We're going to unpack, try to unpack as much as possible but the research, like there's always more to explore so this isn't going to be a comprehensive, all-encompassing explanation of what it is but we want to give enough information that gets people curious, that's already applicable, that they can use and take and run with it but there's always more to read and learn. So yeah, let's see how practical we can make it. So let's start at the beginning. I've been referring to the research but what is the research? What is the study? What is it called that you did and that you recently published your results from? Yeah, so that was a series of interviews with designers in North American, working in North American corporations and I tried to capture their daily, ordinary experiences. But as a designer, what happens to you in corporations? Not macro things but in the daily, ordinary activities, daily work activity and that resulted in a paper when they start to tell me their experience, their daily workplace experiences. So it almost sounds like you did a typical user research study a day in the life of, but in this case, a service design professional wondering why nobody had thought of this before. What made you embark on this journey to explore this? Because you might assume we already know what service design professionals do on a day-by-day basis. You teach this stuff so like why did you do this? So it was completely unplanned, serendipitous. I started to contact some friends in management, design, management roles in corporations and discuss with them what is design-driven culture. Do we have a framework that is there like a set of elements that compose a design-driven culture? And in total, I don't know, I contact 15 people during this, trying to map the design-driven culture and they would say, oh, design-driven culture has to have an element X. So okay, in abstract element X is interesting but how in a daily life this would make a difference, right? In the work experience, how that would change. And they would tell me episodes that happened to them and mostly not pleasant episodes that they went through, right? And they say if element with X, X was there, or Y, that would not have happened. Okay, as a way to justify why that person was advocating for that specific element. And when I start to collect those high-level experiences, they start to cluster into four groups. And okay, what is this? What groups are these? They were very similar. And then I did a literature review around these four types of experiences. And actually the literature, the academic research literature that talks about these four experiences is the literature about workplace bullying. That's the breakdown, right? What? All these people, in my opinion, well-placed, successful in organizations are, experience these four types of workplace bullying. What is this? Then I shift gears and started to contact them about this. So hold on, Maurizio, before we dive into that, because okay, so you start out trying to explore what is a design-driven culture, right? That's your initial question. Not in theory, but what does it look in practice? I'm assuming you're expecting to hear about the context that the organization has created, like, I don't know, budgets, teams, forms of sport, like all the, you're expecting to hear something like this, right? Yeah, yeah. Yeah. But you hear something else. Yeah. So whenever I explain, oh, why this would be valuable, right? Oh, if we have a budget, if we have an independent instructor, why justify to me why this would be important, right? The interview, I would ask the interviewer, and they say, for instance, this happened to me, blah, blah, blah. They'll usually a very not so good experience and say, if the budget or whatever was in place, I would not have gone through this, right? So that was the, they were trying to advocate for what element they want to add, and trying to do so, they would say, or tell me an experience that wasn't pleasant. That's how I started to collect these experience, right? Oh, if you have an independent instructor or a budget, this will not happen. And then immediately start to become way more interesting to talk about the lived experience than the abstract state of, okay, whatever. So yeah, so the enabling, the enabling factors of a design driven culture, like that was your initial hunch, turns out that people were much more interested to share about what it's, what it feels like to be and design professional inside an organization. And that made you flip the research to focus more on those experiences and document what is it like, what is it actually like, not according to the theory, but based on lived experiences. And while going through these conversations, a few patterns emerge, correct? Yeah. So the four types of the experience that they were telling me or sharing with me are social exclusion, which felt like strange, social exclusion. That's the technical name, right? They didn't say this. They said, oh, I was not involved in high level meetings or strategic meetings or important decisions. Whenever I was consulted, there was already some kind of decision made. Then they also refer to ways that their work was obstructed. And actually, the technical name is obstruction, like work obstruction. You try to achieve something and you are somehow prevented or lured into something else and you can't finish what you tried. So yeah, let me comment briefly on that one. So that's, and I haven't checked with you, but please let me know if these were mainly people inside an organization rather than an agency. I'm assuming they were, but the thing that I've been hearing quite often is a comment in the form like, they've hired me as a service design professional. And now that I'm in, the organization isn't allowing me to do the work that they actually hired me for. And it's not uncommon. It's not always the case, but it's not uncommon to hear a comment like that. Yes. And the surprising fact was I tapped into people on management level in large organizations like my network. So if you check the population that was interviewed, you will see clearly they are my network, right? 71% worked on companies of 7,000 employees or more on North America. 51% male, 40 something female. 80% had a master degree or higher. So people that would not be innocent or ignorant of the situation, right? So that's very interesting to hear about the context. And I'm sure that within the research you document even more about who the group is. So you mentioned social exclusion as the first pattern, obstruction. Work obstruction, verbal hostility. Verbal hostility. Yeah. People diminishing what someone said during a meeting in a very top-down way, right? Ah, this makes no sense.  And then stereotyping. Oh, designers, you know, designers, creative people, right? So the consistency throughout, and one thing that was interesting was talking to them, people that I consider and admire highly, right? They were kind of self-blaming. They were saying, oh, I should have done this. I should have done that. Oh, that was my fault. I was not able to communicate. But when you put this all in perspective, right? At the end, I talked to more than 25 interviewed, more than 25 people, and then had 13 surveys on the thing you responded. And when you put this in perspective, Sylvia blamed herself because she did X and should have done A. John did A and think he should have done X. And no matter what, the result was always the same, right? So it's kind of like, whatever you try, at the end, this happens, right? And again, I'm not talking to junior or initial young career designer, right? No, I'm talking to experienced designers. And at some point, the self-blaming didn't make much sense, right? Well, yeah, I can imagine. And also, unfortunately, I resonate a lot with what you're saying, because those are the stories I also hear, for instance, with the in-house service designers that I sometimes often speak to. And when it's just you, and you have no benchmark, you don't hear the stories of others, like the first thing that you do is you assume that it's you, because other people within the organization somehow do manage to be successful, right? If somebody, department A, B, or C is successful, and you're not, it might feel like that it's your fault, right? So, yeah, these four things, you mentioned workplace bullying. When did this epiphany happen that you realized, hey, something, we are seeing a much bigger systemic issue here? Yeah, that's exactly right. When you interviewed, like, in total, I guess it was 27 interviews, by the 10th, right, in total, since the design driven culture, it's more than 50 half an hour chats. But when we decide to focus on this, having done like the 23 prior to the ones we started to focus on this, and then by the 10th that you're specifically asking for these experiences, you can't ignore a trend, right? It was blunt, like, I didn't have to dig deeper. It's what thrown on me, this harsh environment that they were experiencing. How did you feel about this? Like, you're at some point, you're like, I'm onto something. And then, how did you as a service design professional who has a passion for this field, feel about this? It was not a pleasant experience. I have to tell you at some point when I was in the really at the midst of the thing, family, friends were always asking, are you depressed? What's happening? Because the shock was, it was a breakdown, right? Using Alveson's concept of breakdown, like, oh my God, I'm talking to people who I admire, who I reach out for advice. And they are telling me that their experience, all these intelligence and experience that I see in them, didn't protect them from having this sort of experience, right? And having thought and having connection with many young designers, I could, I couldn't refrain or avoid becoming sad for them in a way. It's, on the one hand, you could sort of maybe gain an even deeper sense of respect for these people who are in these situations and still advocating for the value of design, still pushing for human centered perspective, even though like, all the odds are stacked against them and they feel it, like maybe they have become resilient to it or just ignore it. Or I would be curious to hear some of these coping strategies that you found. But on the other hand, like you said, it's hard to ignore that you also feel sorry for these people because we wish them all the best. We want them to succeed. So yeah, I don't have a question here, but just a remark. Yeah, the thing was they were all self blaming, right? Only, no, that was my responsibility to make it work. But again, and all protected by non disclosure agreements, right? They were mostly or most of them were talking about past experience in the timeframe sense. The oldest one that was told me was in 1990 way, 1998. And the most recent one was in 2023. And again, the consistency and clarity of this experience. Ask begs the question, right? It's not their fault. There must be something playing on top of this systemic. So this begs the question. How do we label this systemic thing? Is that workplace? Is that described as workplace bullying? Or do you have other ways to capture that? Yeah, so the first connection was with the literature on workplace bullying. And then Alveson has a very well known paper on advertising agencies. And he makes in this paper a connection between femininity and creativity. And how this impacts how creative professionals are treated and treat others. And that's the connection that was interesting, because it puts the problem that designers are facing, not as a thing against designers, but is the same models operandi that creates the creates the gender gap, the pay gap between women and men. The lack of minorities are in a higher ranking organization. At the end, it's all the same thing. It's this male dominated world, right? And everything that sounds holistic and static, creative, is labeled as feminine. That's the both in terms of the literature in workplace bullying that kind of nudges into this. In order for you to ascend in an organization, you need to be male, in a sense, the aggressive and heartless and concrete in a way. And then the connection that Alveson does, it's unforgiven, right? There's no way for you to not see the picture. So when I start to go back to the interviewees and say, Hey, this is what I'm seeing. That's when I started to hear them say, Oh, okay. So organization streets, designers like women in several different wordings and tones from surprising to, Oh, okay, makes sense. Right. That was also a very cathartic moment. Okay. So we're not dreaming when you present. And that's the tone of the article at the end, the touch point article that published. The intention was just to describe, but we're not raising any controversy or stark catchy sentences, right? But when we start to present afterwards, we had this STN cafe with the first presentation of the results. The reaction was the same. Okay. The designers are treated like women, right? Not women, the sex, the sex assigned at birth, let's say, but the stereotypical femininity traits. So the word is femininity, not women. Right. But that's the help people, the knee jerk reaction was, Oh, also treated like women. And yeah, what does that mean? Few discussions I had with more the academics about this. The two, two ways, I guess, right? One is, Oh, okay. So we're part of a bigger thing. We're not the ones that are prosecuted or it's not personal. It's not about personal, right? It's not designed.  The far you are from this cisgender white male, the more you will be bullied. Yeah. The more you'll have to, the more struggle you will experience on your journey. Yes, your journey. Yeah. Yeah. And that goes into all dimensions, not just design, but it could be people of color, like you said, or whatever form of quote unquote, women, quote unquote, minorities. This is encouraging at the same time. Yeah. But that's the thing that I was kind of happy. If we can use the word happy is, Oh, okay, so we're part of a broader issue, right? We have more allies to tap into, right? It's not just, Oh, let's see how designers can fit better in the organization. It's broader and way more, in my opinion, interesting. So yeah, some people who are listening to this right now will be like, you know, I've been experiencing this thing all my life already, because again, I'm somebody of color. I'm from a third world country, whatever, like, and they will be listening to our conversation, like, what are you talking about? This is my daily reality. But yeah, you are, yeah. Yeah, Mauricio, one thing we didn't yet tap into in this, maybe a sidestep for a minute, but you mentioned that you just wanted to capture reality, like create a snapshot in time rather, instead of giving maybe a judgment. And I think part of your, the way you communicate the insights or the outcomes is through journey map, correct? And can you tell us a bit more about that? So they started to point, again, every time that they were mentioned, things that happened to them, they would place this in time, in a sequence, right? In a context. So the journey kind of started to present itself. And as a service designer, that's a journey, right? If you joined, you just joined the organization, you would have more stereotyping kind of events. And later on, you have more work, in the middle, you have more work obstruction and later on social exclusion, right? It seemed to have a sequence. It would change if you're working on an independent org inside the company, or the design org was part of IT or marketing, whatever, right? So the journey kind of like revealed itself, right? If you have a hammer, everything is a nail, right? So it was easy, obvious for me that, okay, we need to put this into a graphic. And if you want to see this GraphQ, you've shared this online so people can easily access this. I'm going to jump back from question to question, because so many things are on my mind here. I want to circle back to what you said about people, maybe you take blaming themselves for not being able to achieve success. I want to talk with you about the balance in taking ownership of the issue versus being the victim and pointing like they don't understand the like you see like we're we're being treated like women and it's it's it's their fault. So it's it's very it seems to be very polar. It's like you're either the victim or you take full ownership and then it's like you might get depressed from that. Is there like there must be a third strategy because both of these don't seem to be very healthy? No, no. Yeah, the precise right so at first they were blaming themselves I should have done this should have done that. And at some point we saw now this is a major issue, a bigger issue and it's not sometimes you would hear a reference to a specific person oh that manager was awful. But then you see this kind of complaint going on over and again referring back to the academic research they say it's not a bad actor right a bad actor would not be able to act that badly if there was not a support system. So clearly the past show them all it's don't don't try to pinpoint the bad actor because this becomes me against you right like oh I'm right you're wrong and and the literature is very clear on suggesting this right don't try to find the of course reserving clear legal issues like unlawful behavior mostly they fit into this larger picture right there's a system that rewards a certain behavior and even when I was providing the first return of the results several women that were had grown and ascended in corporations they were all very honest saying no yeah I play male in order to go up so it's bigger than yeah yeah yeah well the good thing about this is that we should be really good at analyzing this by zooming out taking a more holistic view don't making it personal and just like the third strategy is let's understand the system like you said that we are part of how is it rewarding certain types of behavior then look at that and change the the context change the system that we're in easier said than done most likely but yeah that's that's probably the most helpful approach so now that we have this this this observation this snapshot and this these insights how do we actually use it to to improve the situation assuming that we want to improve the situation assuming that there is something that needs to be fixed and I think there is but the article itself just presents a picture like the journey map and suggests that people should discuss over as a boundary object right so hey well this happened to me this happened to sylvia this happened to john and there are all these things that might happen forward right just a discussion the integration of this discussion into a larger picture involving minorities and women would would be the the way forward especially for designers right you give designers the the the context and they will find out the way to apply or design the journey forward right so we refrain from from providing any type of suggestions or solutions to them yeah I can also imagine Mauricio that sure this is going to be hopefully very empowering to designers to start a conversation around this topic at the same time these organizations with higher design professionals and want to create apparently who want to create a design driven culture or bring design into the organization I'm hoping that they want to do that in a successful way that they don't want to waste resources time they don't want to fail and this could be a piece of the puzzle to show like if you put design in a system in an environment which looks like this then these are the outcomes that you can expect so like even before you it's not a disclaimer or it's not a manual but it's creating awareness about like the garden metaphor comes up over and over again but if you're trying to plant design on I don't know in a desert it's not going to work right so like what kind of soil do you need does it make yeah does this make sense that organizations could use this so we're speaking in terms of cost right so talking with these senior designers several of them went through this process in three different organizations right so higher designers establish a design team at some point there's a economic crisis there's a they are canceled right now let go this is a tremendous cost right if organizations are trying to do this more than once right even in terms of diversity equity and inclusion right adding more diverse people and they are failing there is a cost to this right so one of the the senior design that I presented the journey map they told me only if I had this journey map during a few meetings very important meetings that I had with top managers of my company it would have made a huge difference right to have someone to point and show a boundary object right to discuss those issues would have made I don't know exactly what he would have done or how he would argue or discuss or talk about this but he pointed to the fact that just to have this outline is powerful now I'm assuming that with every research you do it leads to insight but it also leads to at least three new questions where do we go from here Marisol what needs to be explored next from your perspective one so going back to the start right what is the design driven culture and the discussion and especially if you read Herbert Simon's work you understand that business is designed right business as designing right you organizations are always trying to devise ways to change prefer change current situations into preferred ones right so one thing that would be interesting to to moving forward is to make it clear especially for our management students and future professionals how design is core to business not graphic not interface the knowledge of how to devise ways to change current situations into preferred ones right oh we need to increase sales we need to this process is defined as design the one thing would be to share this more clearly the other put the design that is a core again going by Simon's work that is a core feature in an organization and in this broader perspective of gender gap day gap and and diversity right I think broadening the scope of designers concern of fitting to organizations to this hey it's a broader picture would help minorities and women would help designers would help would help everybody right having designers actually feeling the heat with the experiences of these people as their own right like okay I I'm I'm facing exactly the same consequences of the same cause right those two things would be I think in my opinion right these senior designs whenever I presented the journey map they thought about very tactical things that they would do with the journey map itself right like daily negotiations conversations convincing but I think the two major ones would be this right not not saying that business needs to treat designers better but no business is designed business as designing right and having this broader picture like adding designers to this other communities that are facing the same challenges those two things in my opinion yeah let's let's schedule a follow-up in a in a year time see what happened Mauricio um what if you could give a call to action for anybody who's listening and resonates with this message what would you what would you hope that they would do what is something that they could do based on our conversation today um what I would suggest is take this download the journey map assess your situation what which of these experiences you've been through and start sharing this with your colleagues at work your organization as politely as possible share the the this connection between femininity and design with the diversity equity and inclusion people I think this would give a leverage for their work too right if you make the the connection between design is a core capability of businesses and businesses are not profiting as much as they could because we have all this systemic discrimination against women so I think everybody would be right in sharing and understanding that journey map I will make sure to add all the relevant links in the show notes we will be discussing your findings with our circle community seeing how that resonates I have some assumptions about that we'll see how that goes Mauricio if somebody would like to reach out to you regarding this research is there a way to get in touch with you yes I've posted a summary of the discussions that were that happened already on LinkedIn I'll be happy to to discuss this morning I had a person also reach out to me yesterday so I'm trying to keep some windows on my schedule to discuss the the results with people that are interested and I'm sure that you're open to any suggestions but if is there anything in particular that you hope people will reach out with to you is there anything you are looking for specifically I guess it's how can we in a tactical level right like in a again high level ordinary workplace experience how can we devise ways or actions or tactics that would change the current situation to preferred ones right if they have any idea on how to high level right I'm working on my desk and by doing this I can notch the system not like oh let's create a program that will promote no on a very ordinary level right what can we do in in terms of tactical small actions I would love to collect this right oh do this no nudge that like I'm saying share discuss about this journey with your colleague just this no no second intention just share the journey with the journey map with your colleagues like this kind of tactic like gorilla small nudges well yeah I'm easy to interrupt you here it's not it's not even gorilla what I have found in our design community is that we often neglect the nuances and details of our work and prefer I prefer to talk about the bigger picture the strategies well the details the nuances are the things that make a difference on a day-to-day basis and somehow it feels like it's very hard for us to talk about them because like ah you know it was just a meeting or it was just a scribble like it was just a thing um but those are the things that do make the difference and I sort of I'm fully with you that we need to share more of those nuances those details you made me think about a really interesting connection was watching this Netflix series the blue zones right white people live for 100 years so this guy located communities that live for 100 years and he said they they don't exercise they don't eat healthy they don't they embedded all exercise and eating healthy in their that it's the easiest choice for them right so there's this villa village in Sardinia that it's steepy and they have to go around there's no way to have cars they're not exercising right the the thing is the easiest choice right would be um so what we're making this parallel what are the easiest simple things that we can add to our not add embed into our work activities that would match this and make it a caution conscience approach a constant approach to this right i'm adding all this easy steps and activities that will turn the time let's uh let's take this question at least for starters into our circle community discuss it there see what comes up and uh i hope many people will reach out to you as well sharing these things morriso we need to slowly but surely wrap up for anybody who's interested also have a look at it episode 20 from 2017 see who got more gray hair if it's morriso or if it's me in the last six six years i don't know you already had some gray hair six years ago true so uh mark you're never old that mark you have you're the same that's true that's true that's true but uh encourage everybody to have a look at that video as well that episode morriso thanks so much for coming on thanks again for doing this important work uh painful but uh sort of we need to raise awareness that's the only way to start fixing a system that is uh that is broken that's not working and i'm optimistic that we can actually do this because that's one of the threats of design being optimistic so again morriso thanks thanks for coming on the show thank you thank you mark always a immense immense pleasure to talk to you and especially in such a touchy subject so important to many of us thank you very much for inviting well this was a pretty loaded conversation wasn't it i'm really curious to know which question do you have right now after listening to this story leave a comment down below and we'll try to reply to all of them of course if you want to know more about the research or reach out to morriso have a look in the show notes because all the relevant links are over there if you've made it this far into the conversation and enjoyed it please do me a quick favor press the like button on this video not to feed the youtube algorithm but just to let me know whether or not we're on the right track by addressing topics like this my name is mark from time and i want to thank you for spending a small part of your day with me please keep making a positive impact and i look forward to see you very soon in the next video


We will look at gas solid reactions today. Now, there are several examples of interest to us in which we want to react say a gas with a solid which gives us products. Now, we can look at several types of examples. A simple example would be let us say we have calcium carbonate and it undergoes decomposition. It gives us calcium oxide is carbon dioxide or a very common example would be an oxide reacting with carbon monoxide giving you iron plus CO2. We can balance this reaction. Now, whenever we are looking at a gas solid reaction of course, our prime interest is to see that the product that we get is of good quality. We want the product is of good quality or in other words we do not want unreacted material in the product. Let us take one more example zinc sulphide plus oxygen giving you zinc oxide plus sulphur dioxide. Now, these are all commercially extremely important reactions. Millions of tons of products are produced by these reactions. Each of them great value to us in daily life. If you look at reactions like zinc sulphide, zinc is available in this form called zinc blend. It reacts with oxygen to form zinc oxide and sulphur dioxide. Notice here that sulphur dioxide is also a very valuable product. On other words, if this zinc sulphide does not react completely then part of the sulphur is also lost because sulphur dioxide is used for making sulphuric acid. Therefore, ensuring that this reaction actually goes to completion is of great interest to us. Therefore, in whatever we do, we would like to understand how to manage the reaction so that we are able to drive the reaction to completion. Let us look at some simple examples to understand what might be the way to handle all this. Let us say you have a spherical solid. Now, let us say that this solid was of this size when we started and due to reaction it has become of a smaller size. In other words, the material which is unreacted, this is unreacted. So, when you started the whole thing was unreacted. Now, as the reaction proceeded part of it has gotten reacted. We want to understand how this whole thing solves this reaction proceeds. We will take once again, we will just recognize a gas plus b b solid giving you products. Let us for the moment assume that the film which is on the outside of this solid. There is a gas film which is in the outside of the solid on the solid and all the resistance to supply of the gas is in this external film. So, in other words you have I mean I am just draw this external film in a slightly big way.  So, that you know we understand that you know it is this is the external film. I will call this as the external film external film. So, this gas concentration let us say gas is coming. So, this is the gas gas is here and in this distance the concentration of gas becomes 0. So, if you start at C A G is a concentration of gas and as it enters the film it concentration drops from C A G to 0. On other words the rate at which the supply of gas to the solid surface is controlled by the resistance in the external film. Now, we know from our basic understanding that as the velocity of gas over the solid changes this external film thickness changes. In fact, it decreases velocity increases to the extent we can control this rate of transfer by managing the velocity of gas over the solid. So, if this is the reaction then we can say A A based on our understanding of stoichiometry by minus of 1 sorry equal to R B S divided by minus B sorry minus minus B that is equal to this is these two are equal because of the fact that it is stoichiometry. And also we say that R A with a minus sign is K G times C A G. How do we understand this that the rate at which this is R it is not written properly this is rate R A. Then is rate of supply the rate at which chemical reaction takes place what are we saying that we have a spherical particle. Now, the rate at which the gas is supplied to the solid surface is controlled by external diffusion that is the case we are considering right now. Therefore, we have the rate at which chemical reaction occurs is minus of K G times C A G. K G is the mass transfer coefficient C A G is the gas concentration. We are assuming that the gas outside is in large quantity therefore, as the reaction proceeds the change in the concentration of gas external to I mean on the outside as the solid does not is not significant. And therefore, we can ignore it at least for the moment in this formulation.  So, this basically statement stoichiometry the word this term S refers refers to the surface area of solid which is in responsible for reaction. On other words what we trying to say here is that in gas solid reaction surface area is very important. Therefore, R A is the reaction rate per unit area if you multiply by S it tells you the total reaction rate. Now, if you want to find out what happens to the solid after all our interest is to find out what happens to the solid and how the solid changes. So, we write here our material balance D by D T of N B this is the rate which change must be equal to R B times S we understand this D by D T is R B times S. So, what is R B times S we have said this minus of K G times C A G times S please recognize here. So, R B times S is the rate of chemical reaction. Now, what is R B times S is related to R A times S you have to multiply by this stoichiometry that clear what we are saying. Therefore, the rated which the solid changes that means the rate number of moles of N B the rated which changes is equal to R B times S which is minus of B times K G times C A G multiplied by S which is the surface area which is appropriate to the controlling regime. What is the surface area through which the supply of gas is contact the solid whatever may be the state of the unreacted core. We find that the surface area through which the oxygen the material has to diffuse is the external surface area which is size of the radius if it is R the external surface area is 4 pi R square. Therefore, surface area S that is relevant for this controlling regime is C A G times 4 pi R square. Let us go through this formulation once again what we are saying we are having a spherical particle of radius R. This spherical particle radius R is in contact with the large quantity of gas and it undergoes chemical reaction. And this chemical reaction is controlled by rated which the gas is supplied to the solid surface and that rate of supply of gas is taken as K G times C A G with a minus sign showing that component A is getting consumed because of the reaction.  Therefore, we have on the basis of these that the rated which the solid B changes is R B times S which is minus of B times K G times C A G times S where this surface area refers to the external surface area. And what is N B by definition? N B by definition is the unreacted material whose quantity is this multiplied by density refers to total number of moles. So, what is our model? Our model is we look upon the solid which is undergoing chemical reaction as that of a sphere which undergoes chemical reaction. And as the reaction proceeds as the reaction proceeds the unreacted material which was initially here it keeps on progressing inwards or unreacted course keeps on shrinking. Therefore, it is also called as a shrinking core model. So, what is our model? We have a solid sphere spherical particle which is in contact with the gas of concentration C A G and this concentration does not change because the amount of gas is so large that the change in the gas concentrations are taken as unimportant in this formulation. We will relax all these things that we go along. Now as the reaction proceeds the unreacted surface which is initially of radius R this unreacted surface keeps on shrinking as the reaction proceeds. So, this is the reacted material is this. This is the reacted material this is the unreacted material. So, our interest is to find out how the radius of the unreacted core this is the radius the initially it was R. Now, the radius is let us say small R unreacted core how the radius of the unreacted core changes as the reaction proceeds this is what. So, this equation here now that we know we can substitute for N B we get D by D T of 4 by 3 pi this this is at any time it is small R. So, pi R cubed times rho B. So, this is left hand side equal to minus of K G C A G. Now, we know that the area this that is relevant to this supply of the reagents that is 4 pi R squared. Even if the core radius keeps on shrinking even if the unreacted core which keeps on shrinking the surface area through which is supply of reagents takes place that is 4 pi capital R squared that surface area does not change even though the reaction the core which is unreacted keeps on shrinking. So, what do we get we get that D R D T 3 cancels of. So, we get 4 pi 4 pi R D T rho B equal to minus of K G C A G C A G. So, this is G 4 pi R squared we just check we have got everything right. So, here we get 4 pi R D R C by D T. So, when you differentiate this it becomes R C squared there is a 3 here this is a 3 here which cancels of R C squared here have you got it right rho B 4 pi R C squared D R C by D T minus of B missing here B is B K G C A G 4 pi capital R squared. So, this tells you how the general approach here is to call this is R C to indicate that the core this is the unreacted core. This is the unreacted core and initially the radius of the unreacted core was capital R. So, the capital R is the radius of the particle which, but R C is the radius of the unreacted core which is shrinking because of the chemical reaction. So, we have set up the equations properly here N B is 4 pi R C cubed times rho B. So, I put all the numbers here. So, that the equation looks like this. So, let me simplify this a little R C squared D R C by D T equal to minus of K G C A G R squared. So, this that because you cancel the 4 pi. Now, we can integrate this. So, that the integrated form becomes R B divided by when I integrate this it becomes R C cube by 3 it goes from we started R and goes to R C equal to minus of B K G C A G B missing here R squared and time. Now, put the limits it becomes B times I take the minus sign on this side it becomes R cubed minus R C cubed divided by 3 equal to B K G C A G R squared. Now, I can divide throughout by R here. So, I put R squared here. So, this whole thing can be written as T equal to B K G C A G T equal to rho B R divided by 3 is B K G C A G within brackets of 1 minus of R C cube by R cubed I have got it right that is equal to time. So, it is simply you know taking R cubed outside it simplifies like this. So, let me write it once again just to put it in a nice form. So, time required for complete for reaction of this particle under what I call as external diffusion control is given by T equal to rho B R divided by 3 equal to R C cubed divided by 3 times B which is the stoichiometric coefficient K G is the mass transfer coefficient and C A G is the bulk concentration which is assumed to be unchanging. Now, what happens when R C becomes 0 which means the particle fully consumed or I can call this as the time required for complete consumption of the particle when the external film controls. So, what is tau f time required for complete consumption when external diffusion controls. So, that is equal to rho B R divided by 3 is B K G times C A G. So, that now what it becomes is that time required is simply 1 minus of R C cubed by R cubed or T divided by tau f is 1 minus of R C cubed by R cubed. So, this relationship tells us that if there is external diffusion which is controlling then the time required for complete consumption of particle or time required for consumption of a certain amount of particle is given by 1 minus of R C cubed by R cubed. Now, we also know from our basic understanding is that N B which is a total particle that is present is 4 by 3 pi R C cubed times rho B and we also know N B 0 equal to 4 by 3 pi R cubed times rho B. Therefore, what is this ratio N B divided by N B 0 by definition is 1 minus of X B which is the conversion of the solid that ratio is equal to R C cubed by R cubed. In other words we can also write this equation T by tau f which is 1 minus of R C cubed we can say it here therefore, X B equal to 1 minus of R C cubed by R cubed and therefore, we write T by tau f is also equal to X B. This is a result which comes out of our understanding of the system. What are we saying now what we saying is that if you have a spherical particle which is undergoing chemical reaction which is undergoing chemical reaction under external film diffusion control. If this solid is in contact with the large quantity of gas and this reaction takes place and as a result of this reaction the core keeps on shrinking unreacted core keeps on shrinking. We have our equation which says that the time required for complete consumption to the time required for any extent of reaction the time required for complete consumption is given by 1 minus of R C cubed by R cubed and when we recognize some of these simple relationships we will notice that the extent of reaction X B is equal to T by tau f that is how this relationship nicely comes. So, for the case of external diffusion control we have the extent of reaction X B is simply T divided by tau f. So, if you want to find out a case where there is external diffusion kind of control. Similarly, find the time required for complete consumption time required at any given instant of time that ratio is the extent to which the reaction is occurred. Our next example is we have a particle we have a shrinking particle sorry we have a particle which undergoes reaction. So, what does it mean the particle is undergoing reaction means we have this is the reacted core this is reacted core this is reacted. So, this is unreacted in this case we are looking at the case where this reaction that is taking place is controlled by chemical reaction chemical reaction control. What is meant by chemical reaction control is that let us say at any instant of time at any instant of time the this is the what we call as the reacted core let us say at any instant of time let us say this is the reacted core. So, what we are saying is that the concentration of the gas remains at C A G and as it reaches a solid surface it drops to 0. So, in the same way here concentration remains like this and it drops to 0. So, what we are trying to say here is that there is no drop in concentration of gas as it moves through the external film there is an external film here you can see external film and as it moves through the react this is reacted layer these are all reacted layers you see. So, the assumption here is that this reaction control reaction control means what it means that all the resistance lies in the at the reaction surface. Therefore, there is no drop in concentration as it moves through the external film as it moves through the reacted components and as it comes to the surface it drops to 0. When concentration at the surface drops to 0 means it is an irreversible reaction. Now, if the concentration does not drop to 0 it means that it is a reversible reaction. So, that the surface concentrations will be appropriately described by the equilibrium relationship as of now we are taking the surface concentration to going 0. Therefore, it is an irreversible reaction. So, for reaction control we have d n b by d t d n b by d t as usual equal to r b times s. We also know r a s with a minus 1 equal to r b s with a minus b this also we know because comes to the stoichiometry. So, what is s? What is s which is appropriate to reaction control? We recognize that as the reaction proceeds the surface area that is appropriate to the reaction is the unreacted core surface. So, as the core keeps on shrinking the unreacted core of radius r c it keeps on shrinking. Therefore, the value of s refers to 4 pi r c square. So, here s refers to 4 pi r c square. So, that now we can write what is our rate functions? We have r a r a which is the rate of chemical reaction which is equal to minus of k s times c a g r b equal to minus of b times k times c a g. And we also know r a times minus of 1 equal to r b times minus of b therefore, we get this relationship. So, what is d n b by d t? So, d n b by d t equal to minus what is this relationship minus of b times k s times c a g multiplied by the area which is appropriate to the process. We said the area which is appropriate to reaction control is the area which is the unreacted surface. And at any instant of time the radius of the unreacted core is r c. So, that particular surface area is 4 pi r c square. So, this equation represents the variation of what is happening to component b as a reaction proceeds. So, we get now here the left hand side is 4 by 3 pi r c cubed times rho b. So, this is the left hand side d by d t equal to what is the right hand side b times k s times c a g times 4 pi r c square. This refers to the surface area which is relevant to the controlling surface area. This surface area was 4 pi capital R squared when we talked about external film diffusion control. So, the surface area for reaction control is the unreacted core surface where the reaction is taking place which is 4 pi r c square. Let me simplify this. So, 4 pi. So, it is r c squared into 3 divided by 3 rho b d r c by d t minus of k s c a g 4 pi r c squared. 3 cancels of 4 pi cancels of 4 cancels of. So, you get d r c by d t equal to minus of b k s c a g by rho b. Integrating it is r c minus of r equal to minus of b k s c a g by rho b. So, this r we can simplify this further and write this as r minus of r times rho b equal to minus of b k s c a g t. This t should come here because integrating. So, taking r common 1 minus of r by r rho b equal to b k s c a g t. So, you have rho b r divided by b k s c a g into 1 minus of r by r equal to time. So, what we get here is for the case of reaction control, for the case of reaction control, the time required for consumption to any extent of reaction is given by this. Therefore, when r equal to 0, you have to put r c here, this is r c here to indicate there is a shrinking core. So, r c c equal to 0 becomes t becomes tau reaction control, which is rho b r divided by b k s c a g.  So, this is reaction control. What we say, if you have reaction control, the time required for any extent of reaction to time required for complete consumption is given by the right hand side. At r equal to 0, we know it is fully consumed. Therefore, the time therefore, t becomes equal to tau s that is equal to rho b rho b r rho b r divided by b k s c a g. So, what we are saying once again, let us just repeat what we have said, we have said that this is the relationship that explains reaction control. So, when r equal to 0, which means the particle is completely consumed, which means the r equal to 0 means then this rho b r by b s k h becomes the time required for complete consumption. Therefore, this whole term can be written as tau s t divided by tau s is equal to 1 minus of r by r. This is what I have written. Notice here that as the reaction proceeds, this point the surface which is in contact with the gas, concentration at that point is taken as 0. If equilibrium constants are finite, then that assumption is not correct and then we have already developed procedures to take care of all that. So, what have we done? We have taken two cases so far. First case is when there was external film diffusion control. The second case is the case of reaction control for which we have both derived what is t by tau a tau f or t by tau f, which is in terms of r c, which is unreacted core and then r is the size of the particle. Now, let us look at the third situation, which is what is called as third situation of interest to us is what is called as ash diffusion control. What are we trying to say here is the following? We have a particle, we have what we call as the unreacted core and outside the unreacted core we think and there is a laminar film, which is the external film. Now, what we expect is the following? As the reaction proceeds, as the reaction proceeds, this is the unreacted layer and this is the this is the reacted layer. Now, the distance between the unreacted and the reactor, this thickness keeps on growing as the reaction proceeds. That means, as the reaction proceeds, the thickness of the reacted layer keeps on increasing. So, and we also say that the reaction takes place, reaction takes place at this unreacted surface unreacted surface, which means what? As the reaction proceeds, that the diffusion path around which this gas must diffuse before reaching the solid surface keeps on increasing. This is an instant, we should keep on understanding. Now, for this case, let us see how to solve so that we can understand, what is the rate of chemical reaction? How do we do this? We do this by recognizing the following. We know d n b by d t equal to r b s, we know this. You also know minus of r a times s equal to minus of r b times s equal to d times del c del r into 4 pi r square. What do we mean by this relationship? What we mean by this relationship is that, in the case of ash diffusion control, the rate at which the chemical reaction takes place would be the rate at which the material arrives at this solid surface, because that is the meaning of reaction control. Control means what? The entire process is governed by this rate of supply. So, in other words, here is an instance, where the rate of supply through the reacted layer is what will determine the rate of chemical reaction. So, we must account for it appropriately, so that we can appropriately put these numbers in our equations. Let us see how we do this. What we said so far is that, the unreacted layer, the unreacted layer is here, the reacted layer is here. So, this driving force through this column of this reacted material is what determines the rate of chemical reaction. So, we must take that into account, that resistance into account to be able to handle this problem. Now, what is the general situation? The general situation is that, this is a case in which we have continuous diffusion of particles, diffusion of gas at the same time shrinking of these particles. We have an instance, where the diffusion of gas through the product layer. Simultaneously, at the solid surface, the reaction is taking place. So, we have to take all these things into account, which we will try to do by writing the material balance for what is going on. Let me put the material balance like this input, minus of output plus generation equal to accumulation. So, we are writing the material balance for this gas in this. So, what are the inputs? Our inputs are 4 pi r squared d del c del r at r plus delta r minus of 4 pi r squared d del c del r at r. So, this is the input. In this, between r plus d r and r, there is no chemical reaction. Therefore, there is no reaction is 0. That must be equal to del by del t of 4 pi r squared d r epsilon times del c del t times c. You have to multiply by c. What are we saying here? What we are saying here is that the unreacted layer, this is the reactor layer. The red one is the unreacted layer. The rate of supply of gases to this surface depends upon resistance here. That is what we have taken into account. That difference is the accumulation. So, simplifying, what we get is 1 by r squared del by del r, r squared d del c del r multiplied by porosity. So, this gives you the accumulation of gas in this system. So, simplifying, we get 1 by r squared del by del r, r squared d del c del r equal to epsilon del c del r, del c del t, this epsilon. Make sure all the terms are correct. 4 pi r squared cancels off, 4 pi r squared cancels off. So, this becomes d del c del r 1 by r squared d del c del r with a minus sign. So, no minus sign r plus d r to r, no minus sign epsilon del c del t. So, this is the point of writing this is the following. What we are saying is the following. What we are saying is that in the case of ash diffusion control, the resistance to all the resistance lies in this layer of in this red layer, all the resistance lies here. As the reaction proceeds, this thickness will keep on changing. We have said and correctly that the rate of chemical reaction is minus of r a s or which is r b s with a minus b with a miss already taken. So, r a s and r b s are related. Therefore, minus of r a s into b equal to minus of r b s. This is something we know comes stoichiometry. So, what we are saying now is that the rated which chemical reaction occurs at this solid surface can be given can be obtained from this equation which tells you the variation of c with respect to r. So, what we have done is that we have looked at an unsteady state problem and made certain simplifications. Let us see what the simplifications are. The simplification we would like to do is to do non dimensionalization r by r theta equal to t by tau d. And tau d you might ask how I came to this kind of formulation. Let me explain how it comes? It becomes very easy d c 0 by r by 2 d c 0 r by 2 into 4 pi r square. Now, how do we understand this term tau d equal to 4 by 3 pi r cube rho? What is 4 by 3 pi r cube rho? This is a total mass of material that is been put into the system. What is the denominator? Denominator d c 0 this term t c 0 is the maximum diffusive flux because c 0 is the concentration at the inlet. Therefore, t c 0 is the maximum diffusion flux divided by what is the path length? The length of the path as you can see here or path length is at best r by 2. This is the r by 2. So, this is how path length of r by 2 is chosen. So, that we get this tau d is the total amount of material divided by the rate of diffusion which is d c 0 r by 2. So, we are able to determine a priori what is the diffusion time. Now, let us look at a simplification. What is the simplification that we want to do is we want to solve this. So, our equation is 1 by r square del by del r by r square d del c del r equal to epsilon del c del t. To solve this, we have what is called as the non-dimensional representation. It makes it a little easier to understand what is going on and tau d equal to 4 by 3 pi r cubed rho b divided by b times d del c del r by 6 d c 0 by r by 2 4 pi r square. Please let us understand what is meant by these terms. Why equal to r by r? This is you know it is a well known thing and theta is tau this is reaction time versus the complete consumption time for diffusion control. So, with this we find that our tau d becomes this and when you simplify what is it become rho b r square 6 b d c 0. Let us see whether all the numbers are correct 4 by 3 pi r cubed by r cubed. Now, let us look at the solution. Now, I want to non-dimensionalize this differential equation in terms of these variables. So, you get 1 by r squared y squared del by del y del by del y which is r squared y squared d del by del y is del by del y times r correct. That is equal to the right hand side which is epsilon by tau d tau tau d del psi by del theta. Please understand this what are we saying now? What we are saying is that we have this differential equation 1 by r squared del by del r r squared del psi by del r. The right hand side is epsilon is porosity this is porosity and this is time and so on. So, we have non-dimensionalize with respect to y equal to r by r and theta equal to t by tau d. So, this whole equation must now be written in terms of the our del y squared therefore, it will be r squared del by del y.  So, let me see I have got all the terms right 1 by r squared is correct del by del y is correct del by del r. So, 1 more r will come. So, 1 more r will come here because of this r correct. So, r squared y squared. So, d del c del r. So, it is r del by del y on the other side epsilon tau d del c by del theta this is tau d. Let me simplify this further what do we get going from this to the next one you can see here r squared there is r cube. So, there is r squared here. So, essentially the denominator there is 1 r here there is 1 r here. Therefore, it simplifies as 1 by r squared y squared del by del y of y squared d del psi del y equal to epsilon by tau d del psi del theta. Now our tau d please recognize I will just put it down here tau d we have defined tau d in such a way that it looks like this rho b r squared by 6 b d c 0. Now you can replace tau d here. So, that I am just writing the right hand side only epsilon and then tau d is what 6 b 6 b d c 0 by rho b r squared the right hand side is del psi del theta. Now there are lot of simplifications you can do from. So, that now this equation looks like this r squared cancels of d cancels of and so on. So, you are left with 1 by y squared del by del y y squared del psi del y equal to 6 epsilon c naught by rho b del psi del theta this is the equation that governs what happens inside the particle. See why are we doing all this we are doing all this just to understand an important feature of our problem what is the important feature of our problem. The important feature of our problem under ash diffusion control is that as the reaction proceeds the thickness of the ash layer or product layer keeps on increasing. And our reaction the drop in concentration the drop in concentration comes from it is c a g here and it drops to 0 here. So, it from here now when this when this distance is more that means the second case in this case the second case the drop this distance has increased. That means the drop occurs over a larger distance on other words our mathematical formulation must take into account this increase in the diffusion path has the reaction proceeds. What are we done for this what we have done for this is to recognize that our equation that describes the motion or the variations are given by this equation. Where we can non dimensionalize under certain conditions where we assume tau d to be this which is the total amount of material divided by the average diffusion through this. So, that we define the average time of what is called time of diffusion time. So, with all these simplifications we have reduced this equation to look like this 1 by y square del by del y equal to equal to right hand side 6 epsilon c naught by rho b del side del theta. Please notice that the order of magnitude of y is maximum value y can take is 1 the order of magnitude of psi is 1 order of magnitude of theta is also 1. Because it is non dimensionalized with respect to tau d. So, on other words here is a non dimensional representation of the diffusion equation through the product layer where the multiplicative factor is 6 epsilon c naught by rho b. What is this 6 epsilon c naught by rho b you know from our experience we know the following what do we know we know that c naught. So, let me write this equation once again 1 by y square del by del y y square del psi del y equal to 6 epsilon c naught by rho b del psi del theta. Now, c naught typically is about 0.05 gram mole per liter we know this rho b for solids is typically 10 gram moles per liter. So, what are we saying this and epsilon is about 0.2 to 0.4 shall be same. So, this whole term 6 epsilon c naught by rho b we can calculate 6 multiplied by 0.3 let us say 0.18 this is 0.05 0.18 multiplied by 0.05 divided by 10. So, you can see here this number is a small number on other words this term 6 epsilon c naught by rho b this is approximately I will just put the numbers here you please calculate say 0.3 is 0.05 divided by 10 equal to. So, you can see 0.3 0.3 0.09 something like 9 10 minus 3. So, this is the value it takes is it correct 6 into 0.6 into 0.5 0.3 0.3 0.09 0.009. So, about 10 minus 3. So, this is a small number what you want to say here is that this quantity is a small this is small. So, what is it mean it means that under the conditions of the formulation of the problem it is possible for us to delete the right hand side saying that the right hand side is not very important it goes to 0 or this is what is called also called as quasi steady state approximation. So, that means accumulation accumulation of material inside the particle as the reaction proceeds is small therefore, we can as well assume that the left hand side is approximately 0. So, our problem therefore, what we are trying to say here is that this 1 by y square del by del y y square del psi by del y equal to the right hand side 6 epsilon C naught by rho b del psi by del theta. This is not very important and this is what is called as quasi steady state approximation. Therefore, we might as well solve this problem by assuming that 1 by y square del by del y square del psi del equal to 0. This would be a satisfactory way of understanding diffusion of gas through a solid particle under the conditions of quasi steady state approximation. On other words to understand the rate at which the reaction would take place over the solid during the instance of as diffusion control. We might as well solve a simpler problem 1 by which is essentially the quasi steady state approximation problem which will give us answers which are quite satisfactory. We will take this up when we meet next. Thank you.


we weren't rolling before wow you missed the whole like cringy I don't I didn't like the other one it was like I didn't you're so close to me it's making me really nervous what's happening guys what's happening guys it's your boy Nick chay today I'm here with my good friend a drillie you've seen her in a few of my vlogs and today is a little bit exciting we're doing our very first mukbang today we have buffalo wild beans and we're gonna be answering sponsored not sponsored I wish it was sponsored but today we're gonna be answering some questions for a freshman year college Q&A and yeah let's get it I'm hungry first let's eat okay all right you're really close to me did I mention that it's mmm you got to do the yummy before this video begins a drill is a gonna be she's in my year so she's gonna be a sophomore at NYU studying fashion merchandising wrong you are so wrong she was at my you so follow you don't even know what my major is with it global rural studies alright first question from Tyler when did you start college applications I started mine in August September I always recommend starting early just so you have a lot more time to figure that out is it okay to be stylish slash fashionable if you're living on campus doesn't matter yes 100% of course it's okay doesn't matter in my opinion I think it does like I'm always dressed up for class like you always want to be looking on fleek I like never wear t-shirt yeah dude if you wear sweatpants and t-shirts and slides to class like you're doing something wrong what is something you wish you would have known before you arrived on campus during like the first week like you have like make sure you make a lot of friends make sure like you just make the most connections as you can because that's when you're gonna meet like the most people yeah I think going off that like the very first week that you get on campus it's gonna be a little overwhelming there's gonna be so many people people you've never seen before and you know it's hard to like try and find your good friends especially within that first few months but I think the best advice is to just go out there and like be proactive in making your friends and be outgoing and join clubs join clubs but don't feel pressured to join like too much because like you don't want to make and I were pretty involved but like you don't have to have like that whole mindset of I have to be just as involved in high school and especially in college like the clubs just take up a lot more time so only invest your time into things that you're really passionate about do I get to beat up nerds if I get into an Ivy League school I hearted that one like absolutely where are the negative things about being a Frenchman just ignored me what are the negative things about being a freshman nothing no I think there's a fair amount of I think freshman year is like the best year you literally get you get a pass for everything okay you do get a pass like you're you can act like you're that naive freshman who doesn't really know anything but on the other side seniors and upperclassmen will look down on you if you're being that annoying I'm not just freshman so don't be that kid how's it to live in a college dorm what is positive what is negative one big pro is that like you're obviously independent you don't have parents to be looking out for you but that does kind of count as a con because you don't have someone to cook for you and do your laundry and chores and whatnot now you disagree yeah it's like so much freedom yeah I want to go back right now I'm ready to be back but some people don't know how to do their own laundry or cook or anything do anything for themselves no tino shade but tips for college applications what to say what to put down what to not to do also the advantages of choosing different deadlines earlier regular I don't think there's like an end-all be-all perfect college application and I was pretty close I think the biggest thing is like just be yourself what are you doing bro don't try and be someone you're not and try and use like bigger words or put stuff on your resume that doesn't really accurately reflect who you are wait did you do ed for Princeton I did ed for Harvard I got deferred and I got rejected but I think the advantages of your application early on is really stellar it's on point like you have it figured out really early then I mean like go ahead and submit it to your top school because it there statistically speaking it is a higher chance to get accepted if you do early I think if you have a dream school then definitely do ed because NYU was my dream school that was the only school I wanted to go into and I did ed and I should accept it I was there when she got in I'll play the video right now I don't know I advocate for advocate I'm an advocate you're an advocate but you advocate for ed oh this one's a good question it was how hard it was it for you to stay in touch with all of your high school friends that went to different schools so like I said she goes to NYU I go to Princeton meaning that it's only an hour and a half away from each other I mean since we are really good friends she came down for one of my formals I went up for her birthday I'm in New York a lot so I mean we see each other a fair amount of times regarding like other friends like if you're not close like for me it wasn't hard at all because I mean you have a phone like all you have to do is send a text like there's not yeah there's no excuse for you to not keep up with your friends like what I would do is like I would go on like Google Hangouts with my boys back home we would do that like once a month and once every few weeks just to catch up because like especially in college like everyone's schedule is so busy that you don't have time to always be texting or snapchatting every single day but like if you want that friend and that friend really wants you then like it's a reciprocal relationship worry ways of managing time and having a productive day during freshman year I have a planner oh angel is literally the best person I know about planning her schedule she has a planner literally every single day like hour by hour it is planned out with lunches dinners meetings homework when she sticks to it to a tea like if you texted her to hang out like she's like nope I'm already busy that day it took us like two weeks to plan this no it didn't don't lie I definitely recommend you get a planner it's a life-saver for me it's more so just like having a consistent schedule every single day of like waking up at a certain time going to the gym getting breakfast going to your classes and then dedicating like a few hours to do your homework to study etc etc and then once you like get into a routine and a constant schedule you find that like it just gets easier and easier and you find that like when you miss the day of the gym or miss going to eat at a certain time then your schedule is kind of out of whack but at the same time like be flexible know that like your college schedule is gonna fluctuate a lot so don't like be dependent on one thing every single day be dependent on your college classes schedule that's the only thing that's ever gonna stay in place and everything else is like interchangeable basically in terms of clothing how much should I pack for the first semester let me tell you right off the bat that you will not wear half exactly like bring half of what you think you're gonna need and leave everything else at home because I guarantee that first you're gonna get a lot of t-shirts second you're just gonna be rotating the same few items that you wear every single day and third like not having clothes at home to wear when you're on home for breaks sucks like that's the worst thing this kind of applies to both of us cuz she's just now starting out of her YouTube channel I will link it down below make sure you guys go subscribe she hasn't posted anything yet but hopefully this will force her to make more videos but what motivated you to make your YouTube videos and how did you grow your YouTube channel what motivated me was that I found that there was a big lack of Princeton youtubers or Ivy League youtubers in general and I found that like since I was accepted I have a very like unique position and a lot of advice for those who are in that same position and wanting to get into these really selective schools and how it grew so fast was that just consistency and finding ways to post out content and I think for me specifically is that I don't just do college or Princeton vlogging I do you know fashion and photography and videography so that I have a lot of like different sub topics which are good to expand on why do you want to start a YouTube channel just for the hell of it why not be fun like I think the biggest thing like to start a YouTube channel is to just do it like don't stop asking questions about how to start or what you need to get started is just do advice of finding your people and making real friends in a big college campus I think she can speak better on that because I might use a lot bigger I think we kind of have the same story like this goes back to high school like we never had like a solid group of friends we were like the floaters so like we were friends with a lot of people from different groups I think college was the same like I don't have like a like solid group of friends I just like like meeting people from like everywhere but if you do that like you're genuine and people like you then it should be fine like it's not it shouldn't be hard finding real friends and the biggest thing is like put yourself out there and don't be afraid to step out of your comfort zone and just make the initiative to talk to someone I think that's the biggest thing is like if you don't put your foot forward and be like hey I'm Nick nice to meet you especially those first few months when everyone's trying to make friends like be that person that goes out of their way because because you can't expect other people to do the same if you're not willing to do that yourself how do you manage stress and get over anxiety me personally I'm actually never want to really get stressed like I do pretty well with managing my time and yeah like how often might actually stress or get anxiety or like have like don't that whoa I never thought of that with all the things I have going on like you would think that I'd be someone who stressed out all the time but I don't know I just I just don't find things that that important in life like there's nothing really to stress over like obviously grades are important and like making time for your friends and academics and YouTube like obviously those are all important but I'm at the point where like I figured out how to balance it how to work hard and like get through it like I know that the end of the day I'll be fine so I mean that's not a lot of help but you get stressed I get stressed so easily you just over the little things and I think that's the problem is that like you know I don't get stressed over the little things it's because I try to please everyone like all the time and then it's like it takes a toll on me but that's another story it sounds like a personal issue stop talking in your life especially near as bad as people make it to be when I went into college I thought oh my god like midterm season final season like whatever it's gonna be so hard like it's gonna be just the most stressful time of my life actually it really wasn't like if you know what you know and you're confident in that then it should be fine I think of all the years freshman year is going to be the hardest because you have to figure out how to acclimate to college environment it's an entirely new ballpark from high school like once you get over that world block like I think the first like three months of college with the hardest but after that you like get settled in and now like going back for sophomore year I'm like ready I'm pumped I'm excited I think college is honestly easier than high school in my opinion how so like okay so the workload is not easier the work itself is not easier the content is not easy it's not none of nothing is ever um what's called busy work you don't like your professors are actually like so cool well most of them you're more of like friends with your professors rather than like you're like colleagues and like they're your mentors and you look at them as professors not just as teachers and they're not out to like get you or like try to like I don't know it's just a different dynamic how should a freshman efficiently and effectively effectively figure out their career path slash what major they want to go in the hardest thing when it comes to like finding a major is like finding what you're passionate about and especially at a young age like when we're 18 and 19 like it is hard to think about what we want to be doing as a career when we're in our mid 20s so if you have something you're passionate about whether it's music or art or fashion or business or whatever like obviously pursue that but if you're like someone like me who doesn't really know like I I'm like I said I'm doing I'm doing economics but you guys know my passions photography and film but I think the more practical route for me to take is to get the economics degree have it in my back pocket as a safety and then pursue whatever creative endeavors I want and if it doesn't work I still have an economics degree to fall back on yeah I think it's like key to always be practical or like even have a backup plan because what if that doesn't work out then you have to be able to get back on your feet with something and then just start over it is a little scary thinking about like pursuing a major and then finding out maybe that's not right for you so I mean take a lot of time ask your friends ask your parents like what what they think you should be doing you should definitely have a good relationship with your academic advisor that's like that's the most important thing like if she sees a internship then she's gonna take that and give it to you and say hey are you interested or if you have like a schedule problem like she'll be more than happy to help you if you she's basically like she's gonna be like your best friend in high school or in college because like you're gonna go to her with all the problems that you have like I don't know when to graduate blah blah like all that stuff and that I think that same thing applies for high schoolers like get in touch with your high school counselors and you know make sure you're close with them because they're writing letters of recommendation for you and they're super important for you to get into your college if you would sum up your freshman year in one sentence what would it be a growing experience a learning experience absolutely yeah that's what I was it's so fun and you learned so much it's honestly I think freshman year was probably the best year of my life I think you mature a lot I think you figure your own shit out and like realize that like there's no one else to be accountable for your actions so you have to be responsible for everything whether it's your classes or going to eat healthy or working out like all that responsibility lies on you which may it's probably not have ever been the case for any of you guys before especially with her living in New York like she's living in the real world every single day she takes a metro she like goes out on the weekends like in the city so it's very liberating yeah it's liberating it's like it can only get better from here it's not going to get worse this is the start of a big journey are you sure you don't want that bro I'm full that's a lot bro I'm gonna finish this okay I don't doubt it but that wraps it up for this video thank you guys so much for watching if you enjoyed this mukbang Q&A leave a like down below comment any more videos you guys want to see I will have her instagram and hopefully her youtube channel link down below so give her a follow she is super cool kind of you didn't say anything peace out guys


on this continuing quest to try and work my way through all historical innovations of humanity and work my way up from the Stone Age to the Modern Age and right now I'm just at the cusp of gunpowder with the procurement of salt peter a very crucial ingredient but before the invention of gunpowder you ever wondered like how good of a gun-like weapon could you make I wanted to dig a little bit deeper into pre-gunpowder weapons and see how good of a basically machine gun like crossbow you can make this is a really common trope in a lot of different forms of media where you basically have a crossbow that is in the place of a gun and basically in a lot of media it's a stand-in for a gun and time before guns were invented I think is most interesting is that there's historical existence of this item it dates back to roughly 300 BC in China with the Chukonu and use a really ingenious design to allow you to draw and reload a crossbow in one motion however they ended up having a lot of drawbacks preventing them from really have many wide-scale use because of their design the draw strength of them wasn't that strong it also was a bit more awkward and bulky so it was rather difficult to aim so it's found very limited application however some later designs did make some improvements against these setbacks large versions will be mounted on stands such as depicted in the screen painting with the stand it's easier to operate an aim and with a larger size a more powerful draw strength is possible so I think that's gonna be my goal let's just make a pretty big one but to get a little hands-on inspiration for this device I did see that you buy your own model of it on wish.com so that's what I did so it's a little bit smaller than what I expected um the website made no mention of its size kind of a neat little toy because it's a two-piece at the same time the overall design is impressively simple a single lover when you drop forward holds back and then when you release it it both fires it and allows the next shot to drop down which then when you drop back it fires that one as well so step one is going to be making the stock of the body and this is basically what holds everything together holds the bow in place allows the track for the arrows to be launched from and uh it's basically what you hold on to starting first from a decent chunk of wood these steel hardened chisels I made in one of our last videos will be very useful the first step is going to be carving out the rough shape of the body that makes it a bit more ergonomic to hold on to then using the hand auger we can start the hole that the bow will go into then the last part will be carving in a channel for the upper portion to slide down next I need to construct some sort of stand to hold the body the next step is going to be the this upper portion or kind of an arrow holster this is going to be the device that holds the actual arrows and allows them to drop down to be able to slide back and forth on the rail that we carved into the stock slot here for the bolstering to go into including a notch that it gets stuck to so then when the whole device is pulled back it fires first we'll start with the bottom of it there will be the sliding part that corresponds with the notch we carved into the stock then putting together the sides for the box next to the notch for the drawstring all right so now it's time to do the prod or bow for the crossbow here for our more traditional one we did got a european style which used a forge steel prod wasn't traditionally done much in the east instead they often did a recurve bow or a bamboo I did make a recurve bow before but it's a bit crispy now so I'm going to try and use bamboo and have a variety of different split bamboo here they require a bit of finessean to get the right amount of draw weight generally these do not have a huge drawstring probably because you needed to be able to do the reloading motion all at once too heavy of a draw way probably hinders that it's just going to bundle them together at various lengths to offer enough resistance we'll put it in the hole we put inside the crossbow thank you to the sponsor of today's video lavoit lavoit is the number one air filter brand in the united states and on amazon they sent me the lavoit 600s now the workshop is finished i've been able to use the filter in the new space i was a little skeptical at first we do have a couple forms of dust collection and an air filter already to remove any sawdust and other particulates in the air so i wasn't sure how valuable another air filter would be but i actually found it to be really useful because one of the biggest health risks which i work like this is the small particles get in the air and you end up breathing in it was really important to take care of that caught up in a project and sign something there's a bunch of dust in there not even realizing that i'm breathing it in but the lavoit system actually detects it and turns it on and starts filtering even nicer the fact that it's synced to an app on my phone it gets dusty in the room i get notification and then when i should turn on the other collection systems or put on a mask this is definitely a really important tool in our workshop thanks again to lavoit for sponsoring our video check out some of their products in the link below and then the last piece we need is the actual lever that connects the two devices and is what is basically the firing mechanism you make mine out of steel so it's a little bit stronger so let's start forging that so you will need our ammo the bolts we'll basically use the same design as the previous set of bolts we made for the regular crossbow except with some of larger shafts to attach them to which we'll attach by heat setting them then let's put the last few pieces together and see if it works all right so we've got everything assembled here this one's just got to put tension onto the prod here and then we can see if it actually works and how well it fires just give it a shot okay just to draw strength same for over 50 so that's it's pretty good actually so this is out and draw a fire the thing you're not supposed to do there we go all right so I think we're all set now it adds a little handle thing easier to help push the string out but it looks like it's all set to fire now we've got a decent draw strength to it so let's take it out and start firing some stuff see what we can do so let's just start with one for now there's a chance that my clog will back right in the head it fires it worked got him right in the head got a misfire there I think that's the biggest issue I see is they slide back so it doesn't hook onto it so I probably just need to put a little block there to stop them from falling back that far so probably that's the only issue I see then it should fire oh hit the tree didn't look like there's some penetrating power there and we lost your head by the way I got a couple tweaks here let's hopefully get things to line up so we got two boards on the edges kind of wedge it into the middle and just one at a time and we have this block at the very end here to stop things from going and dropping in past the drawstring yeah hopefully that should work out hopefully start to load that with a few more arrows a little bit of alignment issue uh the tip stayed up and it's just rammed into here two tried to go in at once and that wound up with it tilted up so then when it released it just jammed it to the front of it knot out the hole a few more tweaks got some uh shims in the front there to kind of force the arrows in one at a time so hopefully that should address the last issue here and maybe get some consistent rate of fire that was all of them just one misfire that is definitely an improvement I say a lot of my little front all right so I took a little bit of tweaking but I think I have this guy all set and able to fire repeatedly now fun device to shoot and it packs some decent punch I'm very satisfied I was able to get at least 60 pounds of draw strength with this that puts it in the realm of a kind of a standard crossbow a little bit on the low end I think a hundred pounds would have been really ideal but the fact that it stood up to this and it's not too hard to cock and everything I think it's a good sign that I can actually increase it the advantage of doing it with the bamboo is it going to just add more layers for more resistance and it kind of makes it a little bit more adjustable as far as I can tell this is a pretty accurate recreation of the one depicted in the Korean painting with the naval armament and I have to say I think this would make a pretty effective weapon to use in an actual war once it was tweaked and ran a little bit smoother it was to get a pretty pretty decent rapid rate of fire and with the increased size and on the mount I was actually able to aim it pretty well so I think in a stationary conflict where you're like stuck to the bow of a ship this is a pretty effective tool but this is just the first iteration and I want to try and kind of raise the bar even further because this is not really a machine gun this is just kind of semi-automatic like you still have to manually fire each shot so the real goal would be to make this fully automatic which is going to take a lot more sophistication and for that I've been talking to someone who's kind of an expert at this of yours from the slingshot channel who has made a few different versions of repeating crossbows including the normal size version of this of course he uses slingshot technology and elastic bands which were not invented until the 1800s so to try and do this historically he's gonna require some extra challenges and a little ingenuity so I'm gonna consult with him try and get some advice and try to make this a fully automatic machine gun thanks again for everybody for watching this is one of many different projects that I pulled at the beginning of the year to see what people interested in and this one right relatively high up there moving forward if you are a supporter on patreon me kind of conducting small polls continuously allow you to import what projects I do and don't do so look forward to that coming up and you can have a little bit more say in the type of content we end up doing otherwise thank you to everybody for your continued support thanks for watching if you enjoyed this video be sure to subscribe and check out other content we have covering a wide variety of topics also if you've enjoyed these series consider supporting us on patreon we are largely a fan-funded channel and depend on the support of our viewers in order to keep our series going thanks for watching