Recent content by haitrungdo82

Hi gnell, I just posted a question regarding how to convert some values in an array to other values or how to skip some values in an array. Hope you or nvn can help me since both of you are very good at MathCAD. Thank you very much!

Hi nvn, Thank you very much for your advice! I was afraid that if I did not press the "Quote" button, you would not be aware of my new messages. If this is not the case, I will press the "New Reply" next time. This is probably my last question for you. I was going to take the natural log...

Hi nvn, Thumb up! All the negative values disappeared and the model is physically perfect! It seems like the diffusion coefficient is the cause of all messy, unphysical things. I'm just curious! What were you thinking when you were trying to eliminate the negative values? I'm very curious...

Hi nvn, I just read your post. I think I got what you mean! Let's say we are faithful with my Professor's assumption, t= 200 min. Then, we take a "screen shot" from -10km to 10km, and ignore the rest. I guess you meant after 200 min, most of the pollutants already traveled far away from 10...

Hi nvn, Thank you very much for your kindness! This diffusion constant is actually a corrected version. He might have made a mistake again, but it should be rare because he probably ran the program and figured out the mistake with the original version, then corrected it, and the program...

Hi nvn, Also, since -10km <= x-x0 <= 10 km, probably x0 is the center of the range, which is probably x0 = 2000 if nx = 4000

Hi nvn, Yes. All original data were given in the question. But, t, x, delta t, and delta x can be varied. However, I think, eventually, the program should be large enough so that I am able to inspect the model behavior in the range [-10km,10km] for 200 mins. I'm still thinking about your...

Hi again, nvn, I just forgot! The question actually required me to inspect the evolution of the dispersion of the pollutant over a lateral distance -10km <= x-x0 <= 10km and a time span of 200 min. That's why I had to include a large number of t and x. And if the negative x direction can be...

Hi nvn, Right! Below is a direct quote from the question: "A stack emits at time t = 0 a short burst of pulluting gas that is carried by a steady wind (v = vx = 10 mi/h) (in x direction) while it undergoes lateral dispersion (in x direction). Stochastic dispersion is a process similar to...

Hi Dick! I was able to sketch the graph thanks to your advice. Good job!

Hi gnell, If you feel that's enough, you can ignore my question! I think the simulation is in shape now except some minor strange occurences (I believe!). If we disregard the graph (which is too dense to be visible) and just look at the table of values, the data are actually following an...

Hi gnell, Can the probability density be ever greater than 1? I think it can not exceed 1. But as the way the program is written, it can be very very large! I'm confused!

Homework Statement I'm looking for a closed form expression for the partition function Z using the Canonical Ensemble Homework Equations epsilon_j - epsilon_j-1 = delta e Z = Sum notation(j=0...N) e^(-beta*j*delta e) beta = 1/(k_B*T) t = (k_B*T)/delta e N is the number of excited...

Hi gnell, Actually delta t := 0.01 min and delta x := 5m are the best pair of variables that I was able to manage before the program crashed and after including your and nvn's suggestions. Minh

Hi gnell, Interestingly, when I converted the file from MathCAD to pdf, the graph actually appeared. May be the MathCAD program in my computer is not good enough to show the graph. They are attached below. I think it doesn't matter which 3D type I chose, surface or 3D scatter, the graphs...