# Search results

1. ### Found a cool Non-autonomous Coupled System of ODEs

By a fortuitous mistake in copy/pasting, I happened across this system. It exhibits very chaotic behavior for some initial values and spiral-like shapes for others. (About a 70%/30% split, respectively.) x'=cosy+sint y'=sinx+cost Here's an album of it plotted from t=0 to 1000. The titles of...
2. ### Coauthoring papers as an undergrad (as a programmer slave)

I've been given the opportunity to write programs for two different professors working on separate papers (one math, one physics), and when published they say they will list me as a coauthor. With the first, I sorta resisted a little, because I don't see the amount of work I did as really...
3. ### Global max of a multivar func when restriced to a given plane.

On this year's Virginia Tech test there was a problem to prove: \frac{x}{1+x^2}+\frac{y}{1+y^2}+\frac{z}{1+z^2}\leq \frac{3\sqrt{3}}{2} when x+y+z=xyz So my approach was to consider the function, f, where f(x, y, z)=\frac{x}{1+x^2}+\frac{y}{1+y^2}+\frac{z}{1+z^2} then restrict f to the...
4. ### Extensible phone design! - Phonebloks

It may be impossible. I was under the impression that phones are designed in such weird ways to try to pack as much stuff into the given volume as possible. But, that could just as possibly be an excuse for not having replaceable/upgradable parts and thus forcing new purchases. Idk. If you like...
5. ### Metric for rating funtion accuracy from R^m to R.

I'm writing program in which I generate pseudo random expressions with the hope of finding one that closely approximates the given data set. The functions map from R^m (an m-tuple of reals) to a real. What I need is a way to rate the functions by their accuracy. Are there any known methods for...
6. ### Numerical Approximation of a 4D System of ODE's

What is the most general method of approximating arbitrary systems of ODEs of 4 variables(x,y,z,t) that fit these conditions? The conditions that are assumed true of the ODEs are: 1) that I require differentials to be explicitly defined (but they can be defined in terms of other...
7. ### Python Overlapping Matches Python

I'm writing a function to take a string like "aXYb" and return a regex in which the lower case letters act like actual character and the upper case become free variables. The regex generated from "aXYb" should match anything of the form a([a-z]+)([a-z]+)b. It does. But not exactly as "freely"...
8. ### Culture for microscope fun

Hi, so I have a little background in biology. I took AP bio in HS and got a 5 and really enjoyed it along the way. I got a microscope for my own amusement and also to maybe spark an interest in my little brother. What I'm having trouble with is finding good densities of moving microorganisms...
9. ### Commutator subgroup.

1) Find the commutator subgroup of the Frobenius group of order 20. 2) I have the Cayley table. 3) What is the definition of a commutator subgroup? I am absolutely sure we haven't heard this term all semester.
10. ### Set malloc's memory area

I want to set the area from with malloc gets its memory to a mmap'ed shared memory file, to share data between children and parents without causing pagefaults. It is safe because the data used by children is guaranteed not to be touched by the parent and the children are guaranteed not to malloc...
11. ### SIGCHLD handler hanging

My program is generating a complete, ordered list of primes and children are the worker processes deciding the primality of a single number and exiting with true iff the number they are assigned it prime. The map procs maps pids to numbers being checked. Here is where I register the handler...
12. ### Presentation of a group to generators in A(S)

Is there a general algorithm for taking the presentation of a group and get the permutation generators for the subgroup of A(S) to which the group is isomorphic? For example, given x^5=y^4=e, xy=f(c^2) how do I find (12345) and (1243), the permutations corresponding to x and y? BTW, the example...
13. ### Cardinality of the set of all ordinals.

What would the cardinality of the set of all ordinal numbers be? Is it even known or does the question even make sense in the case of such a weird, almost paradoxical set?
14. ### Reinstall all drivers XP

Hi, so I broke my dad's computer by forcing it to power down. Some how this really messed something up. At first it wouldn't boot at all. But I fixed the MBR with rescue mode on an XP disk. After that, it managed to boot correctly, but it blue screens every time within 30 seconds. The odd thing...
15. ### Python Python: Old-style to New-style Class Conversion Causes Error

I'm trying to convert my __init__ to __new__, but I can't find any docs on how the syntax differs or anything really, that pertains to how this bug could be caused by it. What am I doing wrong here? import copy; class grid(list): def __new__(self, size): self.size = size...
16. ### RTC causing laptop not to boot. Why?

Basically, my problem is, sporadically (as far as I can tell), my laptop will get this problem where when I try to boot it, it will start to boot, but hang. The fans will come on, the power lights come on, the harddrive and optical disk drives POST (I can hear them), but the screen remains dead...
17. ### Why would more RAM of same type/speed not work?

I know what type of RAM I have: DDR3-PC3 12800 at 1600MHz. My laptop came with 2x4GB and I want to upgrade to 2x8GB and every resource I've found says 4GB per slot (and I only have 2 slots) is the most memory this laptop can use (...
19. ### Effects of social status on correlation between intelligence and life sucesss

I've noticed an interesting observation about how the lives of all the people in my elementary AIG (academically intellectually gifted). Out of the 11 of us, the only two not to go to college came from very poor homes. (Even from the beginning, only 4 of us were the kids of a...
20. ### Sodium Bicarbonate and Citric Acid

Homework Statement What salt is produced from sodium bicarbonate and citric acid? Just to be clear, this isn't actually homework. I would hope no professor would ever be so hard. I'm not even in chemistry. Although I did take it last year in high school. Homework Equations I really...
21. ### How to lookup symbols at runtime?

Is there a library with which I can lookup the value of a given symbol in Linux? Also, I've read that C++ name manglingboth unstandardized and difficult. Are there libraries for GCC or Clang? I want use these to build a GUI that uses HTML to design the interface and symbol lookup to allow...
22. ### All my posts are being double posted

The title says it. I'm not double clicking or anything simple like that. Just posting to say sorry, I'm not intentially defacing the forum. If anybody has any idea how to stop it, suggestions are welcome.
23. ### Booting from an SD card.

I'm finally getting a new computer that actually has an SD slot. What I'm wondering is: are SD/flash cards are faster than a 5400rpm hard drive? And, is it possible to boot from a SD card? Basically, I'm thinking it would be a poor man's SSD. Also, is there a way to set windows to use a...
24. ### HCl with Ca(OH)2

Homework Statement I'm trying to understand what happens, chronologically, when 2mol HCl is mixed with 1mol Ca(OH)2 in aqueous solution. Also, is the resulting solution acidic or alkaline. Homework Equations 2HCl + Ca(OH)_2 = 2H^+ + 2Cl^- + Ca^{2+} + 2(OH)^- = ? The Attempt at a...
25. ### Programs Minor to go with double major in math and CS

I'm double majoring in math and cs and will probably do the 4+1 program to get a MS in applied math. But, since I'm starting with a lot of hours (27), I thought I'd go ahead and get a minor in something. Is it even advisable for me to have a minor? I'm not sure what field I want to go into...
26. ### Medical Does CO2 and HCO3- inhibit N2O absorbtion into the blood?

I'm asking because I want to know whether the technique of rebreathing N2O back into a balloon reduces the the amount absorbed when inhaled again. It obviously dilutes the N2O with some CO2 and water vapor, but I assume the dilution is pretty minimal.
27. ### How to determine bond strength

Is it possible to determine the strength of a bond given the elements involved and the order of the bond? If so, how does one go about doing so? The reason I'm asking is because I'm considering trying to code an analytical chemistry library as a way to increase my understanding of chemistry...
28. ### Anyone know of a good OOP plotter for C++

I'm interested in a lot of science involving ODEs, PDEs, and discrete functions of up to 4 dimensions (one of time). Can anyone suggest a library that would be capable of plotting even a subset of that?
29. ### Does Planck length and irrational solutions mean time can't be reversed?

If there is an irrational solution to an equation for where a particle should be, for example from an ODE, then what effect does Planck length have on that? Does the actual position of the particle get rounded to an a multiple of the Planck length? If it does, wouldn't that imply there is a loss...
30. ### Minimum number of elements to in one set to sum to all in another.

Is there a name for the concept of trying to find the minimum number of elements from one set of integers that will sum to all elements in another set? Like, for example, with the Pythagorean Theorem, this would be to find the minimum number of elements from the set of all squared integers that...