Structures Definition and 324 Threads

The definition of having multiple differentiable structures is that given two atlases, {(U_i ,\phi_i)} and {(V_j,\psi_j)} (where the open sets are the first entry and the homeomorphisms to an open subset of Rn are the second entry), that the union {(U_i,V_j;\phi_i,\psi_j)} is not necessarily...

It is a well known view that mathematical logic together with set theory can be used as a foundation for the whole the rest of mathematics. Category theory also has been mentioned as a candidate for this, as an alternative of set theory. But recently I heard (from a non-mathematician) a view...

Homework Statement Assign formal charges to the possible lewis structures of the following and decide which structure is the most important: OCH^{-}Homework Equations The Attempt at a Solution Most important I'm wondering how can i come up with all possiblities..

A cable has an unstretched length of 12.0m and is stretched by 1.2 x 10^(-4)m when a 6.4 x 10^(8) Pa stress is applied. What is the strain per unit volume in the cable in J m^(-3), when this stress is applied? Any help would be very nice. I don't understand what to do.

I often watch tongues of cold mist spreading over a high plain ahead of an approaching cold front. Their upper surfaces are characteristically corrugated by whorls of mist rotating about a horizontal axis, which form and dissolve as a slab of cold air slides under the warmer upper air. Meshed...

in the following question it is known that the rod BD has only axial internal forces, (which i called Q) if AL2=10*I, find the reaction at C and the internal force Q. Assume that the energy of normal forces is negligible compared to moment where there are both. instead of using L/4 i...

Homework Statement Prove that the set of even permutations in Sn (i.e, An) is a group. List the elements of A4 Homework Equations How do I even try to prove these The Attempt at a Solution I have started a new course and am finding the problems very difficult. Is there any books...

Hey, sorry this isn't really a homework question, wasn't too sure where to put it. At the moment I'm taking a concrete structures course. I ordered the textbook online but it's not here yet. I have an assignment due on friday, and really need somewhere to start. So my question is: Does...

Homework Statement The rope BC exerts an 800 N force F on the bar AB at B. Determine the vector components of F parallel to the bar. Homework Equations I already know how to complete dot product (e.g. a.b), cross product (e.g. axb) and understand the basic principles of these...

I live in northern California and there was a substantial earthquake here yesterday. To me, it seemed as though the shaking continued for somewhere between 30 seconds and 60 seconds, but one newspaper article stated the ground shook for 10 seconds. Does anyone know how long structures such...

I'm in a bit of a hairy situation right now. Spring 2010 will be my last semester at my current school studying Forensic Science, and in the fall I'll be transferring to a physics program at another school. I'm trying to get some classes in that will help me in th fall before I leave but there's...

Let's say we have a set S, and a function f : S -> S. Now let S be endowed with a binary operation, forming a group G. Is it correct to write f : G - > G? Up to now I have been operating on the assumption that yes, although G is not technically a set, there is little harm in being sloppy and...

Bowen & Wang, in Introduction to Vectors and Tensors often define some algebraic structure as an n-tuple, e.g. "A semigroup is a pair (G,*) consisting of a nonsempty set G with an associative binary operation: (a*b)*c=a*(b*c) for all a,b,c in G." For more complicated structures, they use this...

Homework Statement determine the electron dot structure of molecules a and b http://session.masteringchemistry.com/problemAsset/1144353/2/MMAt.05.067.jpgHomework Equations The Attempt at a Solution A) ::O: H | | H-C=N-HB) H | .. H-C-N=C=O:: | H I am not at all sure...

Homework Statement I'm having trouble drawing a wedge-and-dash, 2 dimensional molecular structure for Vitamin C (ascorbic acid). All of the diagrams I've looked at (on the Wikipedia page, and some .edu websites) are incomplete: they either don't include the carbon and/or hydrogens molecules, or...

Will we ever be able to find the smallest or the largest structures of the universe or is that not possible in the way infinitesimals and the number line never end.

Homework Statement Draw at least one resonant structure of the nitrate ion in AgNO_{3}. The Attempt at a Solution Is this a possible resonant structure of the nitrate ion?

I have a question on setting up a problem to find the reactions and forces in members of trusses. So initially I find the reactions at the pins using a free body diagram, I get that. However, when I need to find the forces of the particular members am I supposed to take an initial guess as...

Ok so I have been looking over the internet on reading material on structures of tube. From experience I know this happens with items like straws (see illustration below). Is there an actual name of the phenomenon that happens (maybe a few formulas) If you don't understand the picture...

Hello everybody. Well, I failed my airframe structures exam in May, and now have to resit it. I have been attempting to do some exercises to get back into it, but it all looks foreign to me. I'm struggling A LOT, and another fail would mean that I have to resit the year (even though I...

I am doing some simulation like recrystallizaiton, crystal A-amorphous-crystal B. This crystal B is different from A and experimentally proved that B is more like crystal C. Even though the recrystallizaiton is not obvious. As far as I have done, the bond lengths and radial distribution...

I'm new to electrical engineering so this is probably a stupid question. But after reading about piezo-electricity, can it be applied to large structures, like a bridge, to generate electricity when traffic travels over it ?

Is this how you tell when to form double bonds when drawing lewis structures, such as with CO2?

Homework Statement A crane consists of a crane arm which is held in place and moved by strong steel cables. The crane arm is a truss structure, which is a rigid framework of quite thin steel beams welded together, forming many triangles. The cables are made of steel and they are not one...

Hi Well I have been thinking of this quite sometime, but i really dint know anyone who could answer my question. We all know that may elements exist in the form of crystals e.g. Si, Cu etc. And they have very specific crystal structure like Diamond for Si and face centered for Cu. Can we...

the foolowing program is to read inputed data and display them all at once but when i run it it asks for the first information and then runs the total program without asking for the input of other information.after that it doesn't respond and closes immediatelly. can someone help me and tells...

Hi, I made an m-file which which outputs movies at the end. The movie frames are made from images of a 200 by 200 matrix. I wanted to input the movies into a second program which then analyzes each frame. The problem is the frames are structure files and I don't know how to convert the frame...

Hello my smart fellows, I was wondering why scientists say that when an ancient civilization constructs a structure, they can tell the date that the structure was built with radioactive dating methods? Surely the materials used to make the structure already HAD an age, so how would they be able...

Hi, I am a student pursuing an MS in Aerospace Engineering with a concentration in Aerospace Structures. I am currently taking a course in Stability of Structures. The "required" textbook is Guide to Stability Design Criteria for Metal Structures (ISBN 0471127426), and the other recommended text...

Hello, I have this ongoing argument with my professor. I read in a paper (friction and wear) that the crystal structure can affect friction. HCP crystal structures having lower friction coefficients. I have two papers that mention this in passing one, linking FCC crystal structures to have...

When we see structures like DNA for example is it to be understood that if we had a microscope powerful enough to see detail at the level of a DNA molecule we would see the double helix structure? Or are our structures simply models to help explain experimental results? Either way, at what...

Homework Statement the question is in the picture. the rectangular steel bar shown supports a concentric load of 13000lbf. Both ends are fixed. If te modulus of elasticity is 29x10^6 lbf/in^2, what is the maximum length the rod can be without experiencing buckling failure? Homework...

Are there stress and strain graphs for different crystal structures?

Homework Statement Let n>1 be an integer, and let a be a fixed integer, prove or disprove that the set E will stand for is an element of H = {xEZ| ax = (mod n) is a subgroup under addition. The Attempt at a Solution I recognized that ax = a + a + a... + a. I figured this might help...

chemistry, how do i draw the lewis structures for these molecules? i have tried all sorts of ways but keep on geting stuck with atoms which i can't connect, don't have enough non paired valence electrons to join em all up H_{5}IO_{6} TeF_{6} IF_{7} SF_{4} BrCL_{3}

are these the correct lewis structures for these molecules?? http://picasaweb.google.com/devanlevin/DropBox?authkey=sbH95pBl_D8#5275619652409681410 also, if i have an ion for example Al^{3+} what is its lewis structure, this ion is like noble gas Ne as far as valent electrons, so is its...

I have a question regarding Cayley tables, specifically using the composition operator for this particular problem. I had to miss class the other week and was just now sitting down to catch up on my homework for this class when I was hit with the algebraic structures section. They have a...

Hi there! I was wondering if anyone could help me. With Lewis Structures and Valence electrons, do the valence electrons have to go in a certain order around the element symbol? ie: four dots around each side of carbon, or two on the left side and two on the right side? How would you do...

If M is a topological manifold, a smooth structure A (or maximal atlas) on M is a set of smoothly compatible charts of M that is maximal in the sense that if we consider any chart that is not in A, then there is some chart in A with whom it is not smoothly compatible. Now, it is a fact that...

Hey All.. I'm having some problems trying to understand the tetrahedral and octahedral sites in face centered cubic (fcc) and body centered cubic (bcc). It is hard to visualise the structures in 3D.. I wanted to know how to find out the positions per unit cell for the tetrahedral and...

Just wondering.

I'm reading my lectures on TBM and I don't understand the following thing: \omega(\overrightarrow k)=\omega_0-4t\cdot[\cos(k_xa/2)\cos(k_ya/2)+...] It's related to FCC structures, in which the number of Nearest Neighbors (Z) of an atom is equal to 12. Basically the three dots at the end...

Homework Statement Is there some sort of Latex that allows one to draw Lewis structures on the computer? The Attempt at a Solution The following code works in Textify: http://www.texify.com/links.php but not here, apparently. Anyway, I can make 1D Lewis structures (every element in a...

Homework Statement how would you draw this structure in 3d using dash-wedge representation? HN=C=CH2 From my guess, I drew the N=C=C as being parallel, and the two hydrogens coming off the second C without having any dashes or wedges, but curving at 120 degrees from the carbon. For the...

OK this is the first assignment I have in this class and I can't figure out how to negate and simplify the logical structure of W <--> S (bi-conditional implication) I got this so far: ~[(W --> S) ^ (S --> W)] by Definition ~(W --> S) v ~(S --> W) by DeMorgan's Law ~(~W v S) v ~(~S v W)...

Is it possible to form or "glue together" somehow a structure out of other (not necessarily identical to one another) structures such that each of the other structures is elementarily embeddable within the formed structure? With ultraproduct formulation and Los's theorem, it appears that only...

1. I need to be able to draw K C2H3O2 and any resonance structures. SO far I have drawn four and I can think of at least four more to draw... does anyone know if there are more than four and if so, could you please submit a pdf of the resonance structures?

Hello, can anyone help me out the the relationship of the atomic radius R with the lattice parameter a for a Hexagonal close packed cystals (HCP) and how to prove the ratio of a:C is 1.633. Any information on this issues would be appreciated. Thanks

So I’m trying to understand a bit more about the structure of the universe and I keep running across all these “if you think that’s strange wait until you hear this” moments and they almost always cause me an almost painful paradigm shift (without a clutch). Here is the latest. I was always...

can one give me Formalise 3D for adinine , citozin , guoanine , urasil , timine