Structure Definition and 1000 Threads

A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as biological organisms, minerals and chemicals. Abstract structures include data structures in computer science and musical form. Types of structure include a hierarchy (a cascade of one-to-many relationships), a network featuring many-to-many links, or a lattice featuring connections between components that are neighbors in space.

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  1. ugenetic

    Band Structure of a solid is not related to the size/doping?

    Look at the diagram below, after all that doping, 2 blocks of Si have the same band structure? My understanding of band structure and fermi level is that: Given a block of solid (Please note, not a TYPE of solid, but this PARTICULAR block of solid) it will have its own unique band structure...
  2. J

    Constructing a Bending Moment Function Using McCauley's Method

    I have A beam of 1.2 m long, supports at 0m and 0.8 m. forces of 10 N at 0.4 m and 5N at 1.2 m I need to find the deflection equation for this situation. Can someone have a look and see if they can come up with the equation. As I have tried but my results do not match what I am expecting
  3. K

    How do I build this crystal structure in computing programs?

    It's Ti2Ni, which is in FD-3M spacegroup. I have its .cif file which can be loaded by many crystal building program. So I try to build the structure according to the loaded images. I started building a structure with FD-3M lattice. But when I tried to add atoms at the position read from the...
  4. G

    Subbands in semiconductor band structure

    i would like to know all the details about the band structure in a semiconductor and in particular what we call : yours sincerly guedman
  5. Ahmad Kishki

    The Mathematical Structure of QM and the Stern Gerlach

    Many books in QM (eg: Sakurai) mention that the stern-gerlach experiment provides enough motivation for the mathematical structure of QM, Sakurai even mentions Gottfried's book. Point is, i didnt find Gottfried's book, so i am looking for other books that develop the math of quantum mechanics...
  6. eis3nheim

    What is the best referece book to study atomic structure?

    what is the best referece book to study atomic structure and electronic structure of atoms ?
  7. U

    How Is Shell Structure Evidenced in Atomic Nuclei?

    Homework Statement (a) What shows the existence of shell structure? What are the other numbers? (b) Deduce the spin and parities. Homework EquationsThe Attempt at a Solution The shell model is given by: So for Li, 3 protons pair up with 3 neutrons, leaving an unpaired neutron in...
  8. M

    Structure of generated sigma algbra

    I am think what is the structure of generated ##\sigma##-algebra. Let me make it specific. How to represent ##\sigma(\mathscr{A})##, where ##\mathscr{A}## is an algebra. Can I use the elements of ##\mathscr{A}## to represent the element in ##\sigma(\mathscr{A})##?
  9. H

    Independent calibration of structure and load cell?

    I have a load cell which must be placed onto a piece of vehicle structure. In an ideal world I would attach the load cell to the structure and calibrate both together to ensure a very accurate calibration, and that accurate loads are measured. However a problem arises if I need to replace the...
  10. nate crosby

    Free Body Diagram -- forces on a structure over a balcony wall

    Hi, I am trying to work out the forces involved at the contact points in a design of a structure over a balcony wall. I have drawn up the cross section of the situation equilibrium, with a tolerance. I want to find out what forces will be acting on the structure and the balcony wall when a...
  11. R

    Determine Crystal structure of non-cubic crystal in XRD plot

    Given only 2theta and intensity, how to know the crystal structure (except cubic) of non cubic crystals, and also determine their lattice parametera,b,and c, if there's a link or website discussing techniques to determine crystal structure of all crystals, please don't hesitate to put it here...
  12. N

    What is the format for ionic lewis structure w/ resonance?

    Homework Statement I need to draw NH4NO2 which is an ionic compound. 3. The Attempt at a Solution NH4 is fairly straightforward to draw, with one N in the middle and four H surrounding, and no lone pairs. The problem comes with NO2- which is one nitrogen bonded to two oxygens. However, one...
  13. Robsta

    Why Does the Matrix Element <2 0 0|z|2 1 0> Equal -3a0 in Hydrogen?

    Homework Statement Show that for hydrogen the matrix element <2 0 0|z|2 1 0> = -3a0 where a0 is the Bohr Radius. On account of the non-zero value of this matrix element, when an electric field is applied to a hydrogen atom in its first excited state, the atom's energy is linear in the field...
  14. Saint.V8

    How Do I Calculate Floor Loading for My Structure?

    Been trying to bend my head round something that is no doubt so simple it is unreal...! I am designing a structure that has a total weight of 1.6 tonnes (1600kg), the structure floor area is 8m x 3.5m and sits on 8 pads of 500mm x 500mm. To calculate the floor loading do I: Divide the weight...
  15. A

    Determine the structure function

    hi how can I determine structure function ## F_2## in ##R=QCD##, with having ##F_2## in ##R=0## in special ##x## and ##Q## ? thanks
  16. J

    Aluminum structure modifications for use near a very hot fire

    I'm building an frame out of solid 5/8 inch thick aluminum square bars. this frame will be around a fire temps close to melting points but there will be insulation in make sure it won't melt. I was thinking about drilling holes in the free space of the aluminum to reduce it's weight and if you...
  17. C

    Simple Statics Question: Truss Structure

    Homework Statement Homework Equations ∑M = 0, ∑Fx = 0, ∑FY = 0 The Attempt at a Solution If so, If so, I will be using the method of sections to cut along the red line as indicated in the picture. This gives me 3 equations of equilibrium as shown above. However, before solving these...
  18. Oxymoron

    Metrics and Group Structure Reduction

    I don't understand the geometry of what happens when you give a manifold a metric, in particular how the group structure reduces to the orthogonal group. I've read the wikipedia article http://en.wikipedia.org/wiki/Reduction_of_the_structure_group a dozen times but I get stuck when it says that...
  19. S

    Gold Atom Count in O-Ring: 10.4x10^21

    Homework Statement A golf O-ring is used to form a gastight seal in a high-vacuum chamber. The ring is formed from a 100-mm length of 1.5-mm-diameter wire. Calculate the number of gold atoms in the O-ring. Homework Equations Volume of cylinder = PI*h*r^2 The Attempt at a Solution I got the...
  20. S

    Books on Atomic Structure, Chemical Bonding, Quantum for Beginners

    Hi all! I would like to ask your help! I am a rookie in the subject. I have to admit i don't exactly interested in the mathematical way. I really don't have the "basic" advanced math which would needed it. :) Look at me if i would be a high school physics and chemistry teacher whose imaginary...
  21. L

    Structure of orbits at a tornado, whrilwind, etc.

    Any sites showing the whole structure of direct orbits of air molecules inside and outside of any type of turbine? By "direct" orbits, I mean between the two successive clashes of each molecule with other molecules.
  22. I

    Compute subband structure of graphene

    There’re 2 ways to calculate the subband structure of graphene nanoribbon using tight-binding model, for Zigzag chain: The first one is to diagonize the Hamiltonian $H = H_0 + H_10*exp(i*k_x) + H_01*exp(-i*k_x)$ and obtains the eigenvalues. The second method is just diagonize the Hamiltonian in...
  23. Paul Shredder

    Structure of a Matrix With Empty Null Space

    Hi guys, I hope you are having a great day, this is Paul and, as you have seen in the title, that's what I'm looking for, let me explain: When you have a square matrix with empty null space, that is, the only solution to the equation Ax=0 (with dim(A)=n x n) is the vector x=0n x 1, means that...
  24. J

    Inner product structure for classical diff equations

    I'm interested in what people know about the application of inner product structures (usually reserved for QM) to diff equations describing classical physics, in particular non- hermitician diff operator of the Fokker-Plank equation. Thanks.
  25. H

    Why is CNT considered a 1D structure despite having movement in two dimensions?

    The electronic structure of CNT is discussed on the basis of band structure of graphene. Graphene has a linear dispersion relation: E = h_cut vF |k| where k is the 2D wavevector and vF is the Fermi velocity. CNTs are macroscopic along the axis but have a circumference of atomic dimensions, which...
  26. R

    Derive Primitive Vectors in Complex Crystal Structure

    Hi Guys, please help me. how can i derive the primitive vector of copper oxide (I)? basically this is cuprous oxide having a cubic crystal structure but since it has oxygen in it the directions and magnitude of primitive vector are far different compare to basic cubic structure. also please help...
  27. L

    What Would Happen to Humanoid Bone Structure If the Moon Crashed Into Earth?

    Hi all, This is a bit of a bizarre question, but: If some way, some how, the moon crashed into Earth... then (oh so many) years later humanoid life appeared, what might its bone structure be like in contrast to ours? That is all
  28. L

    Does glucose in its cyclic structure react with HI ?

    does glucose in its cyclic structure react with HI to form CH3-CH2-CH2-CH2-CH2-CH3? (open chain structure of glucose reacts with HI to form CH3-CH2-CH2-CH2-CH2-CH3)
  29. G

    S-matrix structure of the lightest particle

    If you have a particle that is the lightest particle, then it cannot decay into other particles. As a consequence of this, its T-matrix amplitude on-shell should be zero, since the S-matrix is S=1+iT, and the amplitude for the particle to be found with the same quantum numbers and momentum is 1...
  30. LokiReise

    A question about a rotating space structure

    So I was thinking to myself, if i had a somewhat disproportionate tripodal space structure, how would i make it rotate around a chosen point where the arms of the structure (hallways and passes most likely) converged ? TORQUE AND MOMENT OF INERTIA ! Then I thought about something else...
  31. T

    Optics - Obtaining structure of an object using a laser

    Hi, Recently I did an experiment to try and discover what some objects look like microscopically, using a laser and looking at their diffraction patterns. We used the fact that the intensity profile you obtain is the Fourier transform of the object you're shining it through, so we can recover...
  32. M

    Formation of Excimer Structures: Explained for Engineers

    Reposting from another section... Can anyone explain to me how an excimer is formed? Like structure wise? Considering Xenon. I've gathered that an excited state Xe*, ground state Xe, and a 3rd body M react resulting in an Xe* excimer + M(carrying away excess energy). I'm struggling to find...
  33. E

    Solving structure optimization with Lagrange duality

    Homework Statement I need to optimize the following structure with respect to compliance P\cdot u_y. the constraint is that the volume of the truss must not exceed V_0. The design variables are the bar cross sections A_1,A_2,A_3 Homework Equations The mathematical programming problem I got is...
  34. TrickyDicky

    Fine structure constant meaning

    I admit that I have always seen this number as a simple proportionality constant relating other constants and units. But there is a long tradition attributing it all kinds of deep physical and even mystic significance, what do you think?
  35. G

    Calculating Stiffness & Displacement of Structure w/100kN Weight

    Homework Statement 1. A structure with weight of 100 kN and which has a natural period of 1 second. Compute the stiffness of the structure. The structure has 5% critical damping. The structure when at rest is subjected to a half sine wave loading having a magnitude of 10kN and lasting 2...
  36. R

    Primitive vector of complex ceramics structure

    Hi Guys, please help me. how can i derive the primitive vector of copper oxide (I)? basically this is cuprous oxide having a cubic crystal structure but since it has oxygen in it the directions and magnitude of primitive vector are far different compare to basic cubic structure. also please help...
  37. T

    Chemistry Molecular Structure: Thorium & Rubidium; Thorium & Phosphour

    Homework Statement Got a homework question for what kind of molecular structure you would get by combining these to metals: Thorium and rubidium, thorium and phosphour. Got to draw the Lewis diagrams and VSEPR model for these molecular structures, and predict the geometry - bond angles - bond...
  38. ORF

    Mesonic effects in the nuclear structure

    Hello The textbooks about nuclear physics I have read don't explain too much about the Yukawa's model. For example, the textbook Structure of the Nucleus -by Preston and Bhaduri- finish the Yukawa's model with open questions about the "mesonic effects" by virtual pions. And my doubt: are the...
  39. R

    Crystal Structure of TiO2 and Aluminum Nitride

    Hey guys, I'm actually had a hard time in figuring out about our assignment in crystallography of semiconductors, the problem said that, Identify the atomic line lattice axes in a, b,c axis and basal plane diagonal, face plane diagonal, and body plane diagonal of TiO2 and Aluminum Nitride...
  40. C

    Packing fraction in ionic structure

    Homework Statement The CsCl structure is stable when the ratio of the smaller ion radius to larger ion radius is ##r > 0.73##. Why is this so? Show that the packing fraction, ##p##, is given by $$p = \frac{\sqrt{3} \pi}{2} \frac{1+r^3}{(1+r)^3}$$ Homework Equations volume of sphere, volume of...
  41. G

    Why diamond is a hardest structure

    Why diamond lattice structure is a hardest (?) one? If it is because each atom connected to 4 adjacent, then why simple cubic, where each atom connects to 6 adjacent is not the case? And why ZnS having the same geometrical structure is not as strong as, say, carbon, or silicon diamond? Thank you.
  42. S

    The Case of Electronic structure of Liquid Metals

    I have been contemplating for a few days now about how one could think about the electronic structure of Liquid metals. The cases of an isolated atom or that of solid metal crystal are well known and easy to understand. Though, a google search reveals (to me) that nothing much has come out for...
  43. A

    Modeling an Accelerating Structure as Static

    Hello all, I am calculating the loads on an unconstrained structure in space that is accelerating. There is a constant known force (T) being applied to it at one end (point A). The structure is a rocket with distributed mass but let's assume it is a uniform beam with constant density. I would...
  44. C

    Packing fraction of spheres in a HCC structure

    Homework Statement Show that the ratio of atomic sphere to unit cell volume in HCP (hexagonal close packing) is 0.74. Homework Equations volumes of spheres, geometry The Attempt at a Solution I did the same problem for FCC and BCC and it was fine. My unit cell structure is that...
  45. D.R.U

    Stargazing Mirror Mounting Structure in Space Telescope

    Hello/... Give me reference or ready made material ...for following mounting method of mirror in space telescope and its mechanical Design and structure for mounting mirror.
  46. fisher garry

    Problem about lattice structure proof

    I have looked at the cation anion ratio of cubic, octahedral and tetrahedral arrangments on an internet site. By a mathematical derivation they find the minimum value for the cation anion ratios for cubic, octahedral and tetrahedral arrangments. My problem is that even though I get the...
  47. W

    Contact Vector Fields. "Flow Preserves Contact Structure?

    Hi All, I am going over a definition of a Contact Vector Field defined on a 3-manifold: this is defined as " a vector field v whose flow preserves the contact structure " . 1) Background (sorry if this is too simple) A contact structure ## \xi ##( let's stick to 3-manifolds for now ) is a...
  48. R

    Drawing a Lewis Dot Structure for Octathiocane (S8)

    Homework Statement How can I draw a Lewis dot structure for octathiocane (S8) which is non-cyclic, net neutral, and which does not violate the octet rule? Homework Equations None. The Attempt at a Solution First, I tried drawing a straight chain molecule, but the two terminal...
  49. W

    2D-Spheres with Complex Structure

    Hi, it is a "well-known" result that the only 2d-sphere that allows a complex structure is S^2 ; it is open whether S^6 admits a complex structure, though it does admit an almost-complex structure. I know there are proofs that require knowledge of characteristics classes; does anyone...
  50. J

    Calculating density of a perovskite structure, a question, phase diagr

    Homework Statement See attachment q2 for the perovskite structure The Attempt at a Solution For the perovskite structure, I assume that the lattice constant is equal to 2*(R1+R2+R3) and calculate the density based on this. Am I correct? (The attachment q2ans is my attempt on the...
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