Structure Definition and 1000 Threads

Hi, last semester I did a project with two fellow students. We made a numerical model to calculate the reflectance from a periodic V-shaped structure of silicon similar to this: In the course of doing so, we came across something we could not explain. I have placed an image of it below...

Homework Statement Identify the [221] vector? A B C D E Homework Equations The Attempt at a Solution I reduce [221] to [1 1 0.5].BUT after getting the wrong answer, the feed back is as follows "Feedback: [221]: has a 0.5 component along the x-axis...

Homework Statement Given force F (=5000N), find Moment on member 4. I have attempted to start solving this problem by drawing the following diagram: I added the letter 'A' to the support of member 2, and also put an angle of 7 degrees to the vertical at the support 1. I have...

Hey guys, I was looking at both the time-dependent and time-independent schrodinger equations, and I notice that we often choose to solve these in spherical coordinates. I understand that we do this because they are convenient for problems with azimuthal symmetry. However, how do we know that...

As far as I understand wurtzite is the name given to the crystal structure defined by the stacking sequence ABABABAB.. However, I am having a hard time understanding what the unit cell is of wurtzite. From what I know the unit cell is the smallest repetitive unit and in it you specify the...

My teacher wrote down something to day which I wish I had written down myself. It was about the crystal structure of wurtzite, which is an ABABABAB stacking of hexagonal lattices. What he wrote was two different specifications of the unit cell of wurtzite depending on which groups of elements in...

Hello all. I need to build a weight supporting structure with the following requirements. At this point, I'm still in learning mode and need help understanding the appropriate terms and formulas to search for. Of course solutions are awesome too, but any direction forward would be most...

Homework Statement Draw the best LS for N2O5, which studies show a) has a N-O-N central atom skeleton and b) Has a central atom bond angle of 180 degrees. Comment on the unexpected bond angle of 180 degrees around the central atom. Homework Equations There are 40 valence electrons...

I am reading R.Y. Sharp's book "Steps in Commutative Algebra" At the moment I am trying to achieve a full understanding of the mechanics and nature of LEMMA 1.11 and am reflecting on Exercise 1.12 which follows it. LEMMA 1.11 reads as follows: (see attachment)...

Hi there , I have two cast iron crankshafts for an engine I'm building , now even though they are similar in every way , made ofr the same engine etc etc, there is one thing I noticed different and it got my attention , I took a stainless steel screwdriver and hit each one of the cranks at...

Hi everyone, :) Here's is a question I have trouble understanding. Hope you can help me out. :) Specifically what is meant by the structure tensor and how is it computed when given a \(2\times 2\) triangular matrix? Problem: Write the structure tensor for the algebra \(A\) of traingular...

What are the best ways to exploit the structures of a given non-finitely generated cancellative commutative monoid? This is not the best way to put together a question, I admit, as what I am asking is very general, but I think it is best to put in here rather than the Chat Room. Also, is the...

Homework Statement 15) How is it possible that many different linear sequences of amino acids can form the same secondary structure (alpha helices, beta sheets, random coils, etc.)? I understand that alpha-helices, beta-sheets, etc. appear in tons of proteins and peptides, but I do not...

When (canonically) quantizing a classical system we promote the Poisson brackets to (anti-)commutators. Now I was wondering how much of Poisson bracket structure is preserved. For example for a classical (continuous) system we have $$ \lbrace \phi(z), f(\Pi(y)) \rbrace = \frac{\delta...

Homework Statement So I'm taking the safe side by posting this question as a h/w problem, since even though its just to satisfy my curiosity, I don't want to take the risk of being penalized for putting a specific case like this one on another forum. Please look at...

Does anyone know of a good code-oriented book on molecular electronic structure theory? I've been looking for a good modern book that teaches how to write SCF code to solve simple cases of the kind of problem that standard quantum chemistry packages (e.g. Gaussian, Orca) are used for without...

I am always wondering, when we are analysing beam structure where many externally applied moments are added on, why we can sum up all the externally applied moments and write equilibrium equations according to that. Because these moments are actually along different axes. Is it because in...

I am studying QFT and got stuck on one question which may be simple. Why is structure constants (in Lie algebra) real and independent on representations? Can you give me a detailed proof? Thanks!

I have read that the structure of almost all organic molecules can be represented visually as Planar Graphs, i.e. 2-dimensional lattice-like structures consisting of nodes (points) connected by lines in which no lines cross. From the perspective of Physical Chemistry, does anybody know why this...

Homework Statement "A force F of magnitude 90 kN is applied at point C at an angle of 45°. The pin-joint B may be assumed to be resting on frictionless rollers. Determine the reaction forces at A and B" Image of the diagram here: http://i.imgur.com/jUL0rJe.jpg?1 Homework Equations two...

Hello, I was wondering why it might be advantageous in some applications to create a structure that is statically indeterminate? Thanks

Homework Statement http://i.minus.com/jxoYt94CAd9LY.png Homework Equations The total number of valence electrons in SOCl2 is 6 + 6 + 7(2) or 26 valence electrons. Dividing by 8, this implies a total of three bonds formed with the central atom (the least electronegative atom, or...

Introduction Dear all, I'm working on an assignment to model a ship-to-shore crane for a FEM design course. Having modeled the crane, I now need to apply the load of the trolley (which is hoisting the container) on the boom (which in my case is a lattice structure made up of beam elements)...

Hello everybody Two questions concerning the notion of wave function. 1. Every quantum mechanics book describes the space of wave functions (or more generally of quantum states) of a given system as a Hilbert space. But correct me if I'm wrong QM also says that two elements of such a...

Homework Statement Homework Equations The Attempt at a Solution Hello, my problem seems to be that I have two values that are possible for the Force FG, but I also am not considering the internal forces F_DE and F_FE. I'm not sure how to go about finding those if they are important for...

How we can distinguish between different type of magnetic structures by simply looking at neutron diffraction data??

I'm thinking about a flat sheet-like structure approaching a massive object (maybe a black hole?). If it were to approach with the plane of the object tangent to the mass, it seems to me that eventually, with enough gravity, the sheet would end up looking much like those hokey "bowling ball...

My problem here seems that I can't figure out how to solve for my unknowns. I have 3 equations for force, and I'm not sure if that equation I have for the moment around the origin counts as 3 new independent equations if I split them up into i, j, and k components. If that is allowed, then I...

Homework Statement Problem 4.36 http://xps2pdf.co.uk/4c82ad8dcb91d5507169e0a18804ea30bf81d592/4.36.pdf Homework Equations The Attempt at a Solution I am not sure if I am doing this correctly..there is a lot of information that I am not using to solve the problem (i.e. all the different...

Does liquid water have ordered structure? I.e., are there significant domains of ordered H2O molecules that maintain crystallinity - translational symmetry - in liquid water at room temperature? I guess this is essentially a hydrogen bonded network - How big are these domains? Or are they...

Homework Statement Draw the VSEPR structures. CH3CH3 Homework Equations The Attempt at a Solution This is throwing me off because there are basically 2 tetrahedral. So, that is what I did. I drew a tetrahedral VSEPR structure and I connected another one to it upside down. Is...

A naive question from someone who knows nothing about the subject: I was wondering how much we can tell experimentally about what's going on inside a star. Can we determine, say, how the temperature or pressure vary as a function of the radius? Thanks in advance.

Is it possible for a disordered or amorphous structure to have band structure? I understand derivation of bands from Kronig-Penney model. E.g. does amorphous silicon have a band structure? While amorphous silicon oxide does not have a band structure?

or else what is the difference between structure,union and enum. can anyone please provide the exact information about them.

A Galilean transformation is defined as a transformation that preserves the structure of Galilean space, namely: 1. time intervals; 2. spatial distances between any two simultaneous events; 3. rectilinear motions. Can anyone give a short argument for the fact that only measuring the...

(inspired partially by this blog post: http://johncarlosbaez.wordpress.com/2012/01/19/classical-mechanics-versus-thermodynamics-part-1/ To my understanding, the thermodynamic configuration space has a nice symplectic structure. For example, using the language of classical mechanics, starting...

Hi, I am trying to simulate a tangential force acting on a point on a structure and the corresponding opposing force caused by the moment of inertia of a mass at a different position. In this image the structure rotates around point c and there is a vector out of mass m opposing the...

There was some excitement a few months ago about the discovery of the Huge-LQG quasar structure, claimed to be the "largest structure in the Universe", which was said to violate the cosmological principle and the assumption of homogeneity of the Universe. Some previous threads on this topic on...

Hello everyone, I would like to buy some Si wafer with SiO2 layer on it. The manufacturer told me that they obtain the SiO2 with a wet oxidation process. My question is, would this layer be amorphous or crystalline or polycrystalline? Thanks!

Homework Statement Use the Jacobi identity in the form $$ \left[e_i, \left[e_j,e_k\right]\right] + \left[e_j, \left[e_k,e_i\right]\right] + \left[e_k, \left[e_i,e_j\right]\right] $$ and ## \left[e_i,e_j\right] = c^k_{ij}e_k ## to show that the structure constants ## c^k_{ij} ## satisfy the...

This question occurred to me while working through some textbooks. Since it is dimensionless, its value can't be explained away saying it's because of the way we chose the units. Well it turns out I'm a 100 years late to this game. I found it's even more serious than I had realized. (And it...

I have been trying to find information on the crystal structure or phase of solid elemental metals at temperatures close to absolute zero, but I can only find information on there ambient structures. Does anyone know of any sources that would have thermodynamic tables for solid metals at low...

My physics core is a little bit weak, and this one question confuses me. Homework Statement A 3kg box sits on top of a 7 kg box. The object accelerates at 1 m/s^2. Find the force applied on the bottom block; if there are no forces besides this one. Homework Equations F= ma The...

Hello! I'm having my materialphysics exam in a few days, and looking some of the older exams I saw that there are many times questions about band structure and density of states. More specifically there might be a picture of some band structure plus the density of states, like this. Then...

Homework Statement Draw the best Lewis Dot Structures the following species: ClF4+Homework Equations none The Attempt at a Solution I calculated that there should be a total of 34 e- in the Lewis structure": 7 (1 chlorine atom) + 28 ( 7 from each of the four fluorine atoms) - 1(b/c the atom...

what is this answer choices: a. Primitive cubic with an octahedral hole b. Body centered cubic with an octahedral hole c. Face centered cubic with an octahedral hole d. None of the above e. Not enough information to determine We didn't talk about this in class, and this was a question...

Homework Statement Hello could someone please help me on how to work this question out I have attached a photo so you can see the question. The equation i think you use is the equation of equilibrium. thanks if someone could please help me! you would be my life saver! Homework Equations...

Do you think it would be possible to use a beam of neutrinos to probe the structure of atomic nuclei? Since they do not interact electronically, they would be useful to study the structure of both neutrons and protons, either through gravitational deflection or weak interactions. Could this...

I was taking a look at the SM particle table and I noticed that the up/down quarks seem to be "reversed" from the usual structure. Neglecting those two quarks, the "up" family is the most massive, then the "down" family, then the "electron" family, then the "neutrino" family. However for some...

Most all familiar with the terms dominant and recessive trait in a general way. I have seen little on the biochemical difference. Assume 1. Gene codes for characteristic 2. Variance in characteristic due to sequence within gene How does the structure of an allele differ from an...