Structure Definition and 1000 Threads

See attachment for question and diagrams. This problem is concerned with using the stiffness matrix method to find displacements and force in a structure. My problem is pre-eliminating the members. i have attached 2 diagrams. i would like help in trying to get from the first diagram, to the...

Hello Everyone, This is my first post. Background: I am an audio guy and seek to understand how cables contribute to the sound of my stereo. Issue: Do audio cables such as power cords, interconnects, and speaker cables "break in" as they are used? Typically, with high-end cables, users...

Recently I am reading the papers in the field of PT symmetry systems. What I am confused is that in these papers, authors directly write out the equations describe the dynamics of the given systems( For example, in this paper http://arxiv.org/ftp/arxiv/papers/1103/1103.3389.pdf , authors put...

As you can see, octet rule isn't satisfied for the central atom Xe, it has 2 more electrons attached to it. So does it mean, that you should first try to make sure octet rule works for any "side" atoms, and then you just put any remaining electrons to a central atom? (or central atoms?) And if...

In flat space the atoms in a metal have regular packing structures. A slight curvature of space would mean this wasn't geometrically possible. As a consequence do we expect metals to have a significantly lower density with a slight curvature of space? Obviously, this doesn't just apply to...

Homework Statement I want to find the force in the vertical purple member. Assuming I know the forces in all the other members, there's a problem with working out the force in the purple member. (Bear in mind, I'm using the method where I assume equilibrium at each joint in the...

Homework Statement This is not homework, I am trying learn fine structure. This site is reliable : http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html, can you tell me if the content of "hydrogen fine structure" is still valid or dated?. Even if it were classical oudated model, I'd like to...

Homework Statement The atomic mass of Niquel is 58.7 amu (atomic mass unit), and it's density (at 90ºC) is 8.86 g/cm³. (a) Find the distance from one atom to the closest one from him.Homework Equations 1 amu = 1.66053*19⁻²⁷ The Attempt at a Solution I started by finding the number of atoms...

Homework Statement Consider a star of radius R, with density p that is constant, composed of classical, nonrelativistic, idealg gas of fully ionized hydrogen. a. Solve the equations of stellar structure for the pressure profile, P(r) with the boundary condition P(R)=0 b. Find the temperature...

Homework Statement Hi, I am having trouble with the following problem and I can't seem to find any examples: I am trying to determine reactions at points A and D of the redundant structure below using the unit load method, there is a 10kN load at the top left point (B), all lengths are...

Atoms in solid are more closedly packed as compared to liquid and gases. But we exert more force, some solid gets compressed but liquid doesn't, why? If atoms are loosely packed in liquid than solids, liquids should get compressed...

Homework Statement Draw the structure of aspartic acid at PH 4. I calculated the PI and based on that, drew the charged structure. If anyone can confirm that this is the correct structure. Homework Equations The Attempt at a Solution I attached the structure. Thanks for any assistance.

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...

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...

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...

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...