Structure Definition and 1000 Threads

If you were the mister of education or whatever, how would you structure high school physics? Would you make it more math heavy, would you put an emphasis on critical thinking and understanding or would you increase rote-learning or decrease it? Would you make it so that it prepares students...

Hello, Is there an established relationship between the diffraction intensity that a sample produces with its band structure? Thanks

Hi! I'm reading about band structure and conduction in regular crystals and semiconductors, and I've hit a few confusing points my book doesn't explain well enough for me. In one part, they're explaining conduction in a 1D crystal with lattice spacing a (and therefore reciprocal lattice...

What are the parameters affects the band gap in a band structure?

what are the internal force in the hinged member 1-4?

Homework Statement Let's say I have two compounds in an identical solvent. The compounds are also identical except for the following: One has a Br bonded to a tertiary carbon, and the other has an I bonded to a secondary carbon. Which would react first in an Sn1 nucleophilic reaction...

Hello! If anybody has a minute, I'd appreciate a quick look-through of my proof that a finite abelian group can be decomposed into a direct product of cyclic subgroups. I'm new to formal writing (as well as Latex) and all feedback is greatly appreciated! Thanks in advance for your time...

Homework Statement Let (R,+, ·) be an algebraic object that satisfies all the axioms for a ring except for the multiplicative identity. Define addition and multiplication in R × Z by (a, n) + (b,m) = (a + b, n + m) and (a, n) · (b,m) = (ab + ma + nb, nm). Show that (R × Z,+, ·) is a...

Many times, I find it hard to draw correct Lewis structure of molecules with nitrogen. For instance: the Lewis structure of H2CNN. I thought it should be double bond between C and N and single bond between N and N, like this: But actually it's not. I have done many problems like this wrong...

Homework Statement (see attachment) Homework Equations The Attempt at a Solution How the equation ##x^2+y^2-x=0## is that of a cylinder? That looks to me an equation of a circle. I haven't learned about the different 3-D structures so I tried solving this using graphs. I tried to...

Homework Statement Hi All, I am new to this forum and have a question for which I need some assistance. My knowledge about this subject is limited, but I need te following: For a project we need to specify the torque required to uprighten a structure when rotated to a certain angle. The...

Hi, How can I calculate such terms d^Aae d^ebD f^AaE f^EbD d^Aae d^EbD f^AaE f^ebD Cheers, Safinaz

Just saw this http://www.space.com/19220-universe-largest-structure-discovered.htmlarticle about a quasar group that's 4 Gly long. Not to speculate too much, but any thoughts on how much of an impact this could have on our current models and understanding of the formation of the universe? The...

I'm trying to do a HW involving the Darwin Term in the fine structure of hydrogen. I'm given that the perturbation from the Darwin term is equal to (times a constant factor which I'll ignore), V_D = [p_i,[p_i, \frac{e^2}{r}]] = e^2\vec{p}^2\frac{1}{r} -2e^2\vec{p}\frac{1}{r}\vec{p} +...

Upper limit to size of Air Supported Structure?? Hey yall! I am new here, and I'd like to ask a question I can't seem to get an answer to anywhere else, so why not get it here! I'll get right to it! The question is...What is the upper limit of an air supported structure, and what is the maximum...

What would be the structure of the crystal if rc/ra=1? hexagonal closed packed or anything else? What would be the structure of the crystal if rc/ra< .23 ? What would be the structure of the crystal if rc/ra>1 ?

Suppose an electron in a crystal(periodic potential) has the Bloch wave function \psi (k_0,x) at t=0. Applying a constant electric field E(at t=0), the electron would still have Bloch-type wave function at any time t with k(t)=-(1/\hbar) eEt+k_0. Now According to this formula for k(t), one can...

Hello Everyone I'm currently working on a unstructured quadrilateral mesh for a discontinuous galerkin free surface flow model. I use the half-edge data structure in the two dimensional code. Does something like a half-edge or "half-face" three dimensional data structure exist. Otherwise...

Author: Jerry March, Michael B. Smith Title: March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure Amazon Link: https://www.amazon.com/dp/0471720917/?tag=pfamazon01-20 Prerequisities: High-School Chemistry Contents: User comments...

Hi there. I am having trouble interpreting the Kolmogorov K41 scaling relation for homogeneous and isotropic turbulence: S_{p}(l) = <\delta u(l)^{p}> = <|u(r+l) - u(r)|^{p}> \propto (\epsilon l)^{p/3} where l is the length of displacement between two points under consideration in the...

Largest Structure in Universe Discovered By Mike Wall | SPACE.com Astronomers have discovered the largest known structure in the universe, a clump of active galactic cores that stretches 4 billion light-years from end to end. The structure is a large quasar group (LQG), a collection of...

Homework Statement Construct a C∞ natural differential structure on the ellipsoid \left\{(x_{1}, x_{2}, x_{3})\in E | \frac{x_{1}^{2}}{a^{2}}+\frac{x_{2}^{2}}{b^{2}}+ \frac{x_{3}^{2}}{c^{2}}=1\right\} Is this diffeomorphic to S2? Explain. Homework Equations Do I need to prove...

So this is my idea: make concrete using iron sand, preferably one with a decent ferromagnetic interaction. As the concrete sets, apply a magnetic field. The ferromagnetic particles align to the field creating a structure within the concrete. Possible to coat the iron sand in a retarding...

I'm trying to understand the difference between diffeomorphisms, diffeomorphism invariance, reparameterization invariance, and differential structures and how each of these terms relate to physics. Perhaps there's a book out there that explains the differences between these constructs and the...

Please take a look at my program. Please help. I want to allocate memory dynamically for one field in structure. I tried to write the code but it has error. I posting a paint document for you to see. Help me please. Please tell me why is my code not working properly and what needs to be done...

The angle of the water H2O molecule is 104.5°, the angle of ammonia H3N is 107°. The angle between 2 p-orbitals is 90°, the angle between 2 sp3 hybrid orbitals is 109°28', the tetrahedral angle. Why is it assumed that water is a "greatly" expanded p-orbital angle, rather then a "slightly"...

The Daily Mail Even as a novice in biology, I found this amazing and had to post it here.

The S molecule of SO2 forms a double bond with one O and dative covalent bond with another O Meanwhile,XeO4 is a molecule which Xe forms a double bond with each O I have a question here Why doesn't that S forms 2 double bonds with O to extend its octet structure? Similarly,why doesn't that...

Is this structure statically indeterminate? I'm thinking it actually statically determinate, since there are three unknowns (Ax, Bx, By) and three equations. The external loading Px, Py are known. I also solved for the forces in the members of the truss and they seem to work out, but my...

Hi there. I have to determine the Lewis structure for NSF. So first I thought of something like this: N=S-F, with the nitrogen with four free electrons, the sulfur with two, and the fluorine with six. The formal charges gives -1 for Nitrogen, +1 For sulfur, and 0 for Fluorine. But the...

Homework Statement I'm implementing the transfer matrix method (manually) for an EM wave through a 1D layered structure. Basically I'm just considering a plane wave in the positive-x direction, conserving E and H across each material interface, and constructing interface matrices, the...

Can someone give me a real-life example of an aerospace structure buckling? I need a real example to discuss column buckling theory..etc. I couldn't find any online. Thanks.

1. The problem statement. Calculate the energy generated per unit mass, if helium burning produces equal amounts (mass fractions) of carbon and oxygen. mH = 1.672621581 x 10^-27 kg 2. The attempt at a solution Helium burning produces carbon according to the following reaction: 3He -> C...

I'm wondering if anyone can help me with the reasoning for what follows, I'm thinking I must just be missing something quite obvious but I can't seem to see what that is at the moment! :redface: I understand how to get the structure by starting from a 'skeleton structure' and just filling in...

I have put down https://dl.dropbox.com/u/6040582/CategoricalPhysicsAug26_2012.pdf on how we can start to see physics as an interface to underlying "structure". "Structure" is posed without its normal qualifier "Causal" and it will become more clear why I am doing this if you read the paper. Does...

Griffiths writes that the formula for the hydrogen energy levels taking fine structure into account "breaks the degeneracy in l" but "still preserves degeneracy in j." I'm confused by this, because the formula he gives (Eq. 6.67 in the textbook) depends on j. How can the system be degenerate...

I have designed this truss but I'm reading on the internet that this equation, 2j = m + r IS NOT enough to determine whether a structure is statically determinate. It has to do with the arrangement of the members as well? How can I tell beyond the equation I guess is my question? Also...

For metals for instance, is the metallic bond that determines the crystal structure(i.e. FCC (face centered cubic), HCP (hexagonal close packed)) or is the crystal structure that determines the type of bond? In other words, if someone were to ask me what kind of bond an element with an FCC...

In the following link http://en.wikipedia.org/wiki/File:Silicon-tetrafluoride-2D-dimensions.png the bonds are represented pictorially in different ways(like the black triangle). Do these just show the physical structure of the bonds or do they show the different types of bonds?

Homework Statement This isn't a homework question. I'm working through my book's exercises and am having difficulty interpreting an answer. Any guidance will be very much appreciated. The problem is to come up with a structure function for a graph (image attached with this post). The answer is...

Could a universal "Oort cloud" structure cause expansive acceleration? Could there be a giant sphere of invisible non-reactive matter (neutrinos?), left over from the big bang, so massive that it's gravity is pulling galaxies outward? I know the Oort cloud doesn't pull planets outward, but...

Quantum mechanics tells us that particles have a wave-like nature: their position, momentum and energy are not absolutely defined, and obey the Uncertainty principle. One thing that strikes me as peculiar in String Theory is how much internal structure string appear to have at the Planck...

hello! what are the available methods to determine the sequence (primary structure) of a protein? from where one can start (what info he can gather) and how he can deduce the primary structure? thanks!

Homework Statement e is charge epsilon is permittivity Homework Equations e^2 = 4\pi \epsilon GM^2 The Attempt at a Solution This is just a question really because I am a bit confused about something. Was reading up on the fine structure constant and apparently the fine...

Can anyone tell me what a high gradient RF structure is? I think it is referring to the strength of say an electric field in a structure oscillating at radio frequency but I am not sure. I would appreciate any explanation.

Dolphins have larger brains than humans. So, why aren't they smarter than humans... or, are they? Are those sneaky Dolphins playing dumb? j/k It's my (very limited) understanding that the cortex is responsible for the higher levels of what we think of as intelligence. So, what's different...

I found a lecture on the internet where a LCAO assumptions are used to calculate the phonon band structure. In this lecture (Here) we can find that the true Hamiltonian: H = \frac{p^2}{2m}+V_0(x) where V_0(x)=V_0(x+a) is replaced with the following aproximate hamiltonian: H\cong \sum_n...

Hello, Does anyone know any (free) software for generating simple crystal structures like forms of SiO2 or TiO2? It must be a really common problem. My current strategy is to search the web for hours until I get lucky. There are online databases which have really complicated structures from...

Hey Everyone, I've a quick a question regarding the make-up of bosonic Green's functions, taking the free propagator for phonons as example. According to Mahan, 3rd ed. it is given by: D(q, \lambda, t-t')=-i\langle0|TA_{q}(t)A_{-q}(t')|0\rangle with A_{q}=a_{q}+a^{+}_{q} [ Eqs...

What does it mean to give a group structure? I'm working on a problem and part of it asks for the structure of the group. The law of composition and generators seem to be given already (and an expression that says that a^2 = 1 for any elt a of the group). Is there anything to do other than...