What is Structure: Definition and 1000 Discussions

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. E

    Regions in the electronic band structure

    I'm thinking mainly within the context of the useful semiconductors here (Si, GaAs, etc.)... What does it mean for an electron to be in the L or X valley instead of the Gamma valley? If Gamma is the k = 0 point, then momentum p = 0. Does that mean being in L or X means all the electrons...
  2. A

    Micro structure from equilibrium diagrams

    I have this question: "What micro-structural features of metal alloys can be studied by using equilibrium diagrams and how? Can the equilibrium diagrams be used for some other purposes? What are the limitations?" I think that only the composition of micro-structure can be predicted in a...
  3. L

    Calculating the force exerted on structure by two large permanent magnets

    I am a mechanical engineering student so don't have experience in specifying magnets and or using them. So its out of my comfort zone. I currently have a U shaped structure holding two large permanent magnets apart at either end. The magnets will need to be 200x200x40 in size and the gap is...
  4. S

    Diffraction pattern to crystal structure

    How do crystallographers go from a diffraction pattern to actually determining the structure of the crystal? http://pwatlas.mt.umist.ac.uk/internetmicroscope/micrographs/microscopy/decr5a-a-big.jpg
  5. T

    Electronic Band Structure, Ionization Energy

    Hi, thanks for reading my questions. I've been reading and reading and reading and reading and I'm trying to understand the difference between conductors, semiconductors, and insulators at an atomic level. When reading about electricity I often find that metals have a "sea" of "free"...
  6. quasar987

    When can one reduce the structure group?

    I know of the theorem that says that in any fiber bundle with structure group G having finitely many connected component, the structure group can be reduced to a maximal compact subgroup of G. But here I am reading a thesis in which the author says: "[Since U(n,n)] is homotopic to its maximal...
  7. C

    Band structure and fermi surface of copper

    Hi I've been searching on the web for this two topics, band structure and fermi surface, both of copper. I can't find any of them from a free source, I am doing just a report of my class of introduction to solid state and I just have found this two things in articles that must be bought. If...
  8. S

    Vibration analysis of a structure with cyclic symmetry

    Lets us say we are doing a vibration analysis of a structure with cyclic symmetry In very brief (as pointed out by AlephZero in one of his excellent reply) the whole motion can be represented by complex numbers which describe the motion of one segment. Now, my question is: 1)Is it...
  9. A

    Structure and properties of polymers

    Hi! I need a reference (book, webpage) that explains how the structure of a polymer affects its properties. I've found plenty of material over how structure changes its mechanical properties, but I could not find how it changes other parameters (e.g. electrical conductivity, boiling point...)
  10. J

    New Models to Describe Nuclear Structure

    Hello all, I'm an amateur interested in nuclear structure. I'm interested in the (by now) age old questions of "Why is alpha radiation so much more prevalent than simple neutron or proton emission?" and "Why aren't nuclear isomers like Tantalum a lot more common or identified?" and especially...
  11. B

    Why does the LED structure favorizes p-type semiconductor?

    Why does the LED structure "favorizes" p-type semiconductor? Hi all, At first I apologize if my English makes this post harder to understand ;). I am trying to figure out why there is always P-type semiconductor flashing outside in LEDs, both planar and edge ones - P-type region is the active...
  12. M

    Fine structure correction in H atom

    Hi, I refer to the second edition (international edition) of Griffiths. He proves that the total fine structure correction (spin orbital plus relativistic) is given by E_{fs}^{1}\propto (3-\frac{4n}{j+1/2}) After that, he writes this. "Fine structure breaks the degeneracy in l (that is, for a...
  13. M

    Ways to prevent slippage of a structure under testing

    So I have a structure that I have to test, or more so a "model" structure. It is in the shape of a T, but rotated on its side, so that the stem of the T is a cantilever beam. An actuator will be used to load the structure at the free tip of the stem. My task is to design the supports of the...
  14. T

    Mechanics question, structure with unknown forces

    Homework Statement Find force between all members. Homework Equations torque=force x distanceThe Attempt at a Solution to use sections as seen in the photo, beyond that no idea how to attempt it. It would helpful if anyone could show me how to get the force out of even 1 member.
  15. S

    Can Anyone Explain How to Visualize a 4D Structure Like a 3-Sphere?

    I have been reading about http://en.wikipedia.org/wiki/3-sphere" and found it was impossible for me to visualize it. I tried visualizing a 4d structure with 3 space-like and one time-like dimensions by imagining a sphere (with 3 dimensions) growing with time, with successive layers (formed...
  16. B

    Lewis structure for Nitrogen Dioxide

    I am pondering on what the correct Lewis structure(s) for Nitrogen Dioxide (NO2) may be... I have come up with 7 possible structures, but am unsure which are correct and which are not. I have compiled a small list of notes for your convenience and they are all in this picture. Which...
  17. fluidistic

    Fine structure, hydrogen atom, principal quantum number 3

    Homework Statement The level n=3 for atoms with 1 electron have the states 3s_{1/2}, 3p_{1/2}, 3p_{3/2}, 3d_{3/2}, 3d_{5/2}. If we ignore the spin-orbit coupling these states are degenerated. Calculate the degeneration due to the the spin-orbit coupling for the levels 3p and 3d for the...
  18. Dotini

    Does Fine Structure Constant Vary From Place to Place?

    http://www.swinburne.edu.au/chancellery/mediacentre/media-centre/news/2011/10/natures-laws-may-vary-across-the-universe One of the laws of nature may vary across the Universe, according to a study published today in the journal Physical Review Letters. One of the most cherished principles in...
  19. jfy4

    Can Structure Constants Define a Metric in a 10D Lie Algebra?

    Hi, Let's say I have a 10 dimensional Lie algebra over some field of functions, something along the lines of at least twice differentiable with twice differentiable inverses. The structure constants have inputs from this field. Is it possible to build a metric from these structure...
  20. J

    Why Does ClNO2 Have Only One Double Bond in Its Lewis Structure?

    Homework Statement Draw the lewis structure for ClNO2 The Attempt at a Solution When I first drew this I had two double bonds in between the N and the Os. However, the answer suggests only one is a double bond in the structure. Why is this correct? Aren't we suppose to balance the...
  21. W

    Term structure isomorphic to the usual model/structure of number theory

    Hello, suppose I have a set of sentences Ʃ from the language of number theory ( the usual one ). Then, I extend this to a maximally consistent set of sentences Ʃ' and create a henkin term structure for it ( i.e. as in the popular proof of the completeness theorem ). Can it be true that this...
  22. A

    Lewis and dot structure of (NH4)2SO3, Al2(SO4)3 and Fe(ClO4)3

    Homework Statement I have to draw Lewis structures and Lewis dot structures of these salts The Attempt at a Solution I attached images of how I tried to traw Fe(ClO4)3 and (NH4)2SO3 but I can't figure anything out about Al2(SO4)3
  23. Jadaav

    Atomic Structure: Uncovering the Nucleon of Chlorine 35.5

    I got a question : Why is the nucleon of Chlorine 35.5 ? Why is is not a whole number ?
  24. D

    Compare the structure of RNA and DNA with respect to the following characteristics.

    Homework Statement 3) Compare the structure of RNA and DNA with respect to the following characteristics. Length Function Molecular components Homework Equations The Attempt at a Solution I know nothing about the length, Function: RNA reads the info in DNA and transports...
  25. naoufelabs

    Is the Group Law * Associative and Commutative? - Exploring Algebraic Structures

    Please I have a problem with natural log for group set as follow:a*b=eln(a)*ln(b) 1- Show that the group law * is associative and commutative 2- Show that the group law * accept an element e (Identity element) Thank you !
  26. T

    3-methylheptane draw the structure

    So I am given 3-methylheptane I know that it looks like this: CH3-CH2-CH-CH2-CH2-CH2-CH3 And the methyl group is attached to CH It is heptane so I have 7 carbons and a total of 15 Hydrogens but I don't understand why it isn't 16 Hydrogens don't I use the formula CnH2n+2=16Hydrogen If...
  27. P

    MATLAB What is a 3x3 subwindow structure in matlab?

    I am confused as to what that means? Is that a coordinate system with 3 y-values?
  28. A

    Deriving the Relationship of Cubic Crystal Structure

    How can one derive the relationship for a cubic crystal: d= \frac{a}{\sqrt{h^2 + k^2 + l^2}} It is shown here. This is probably trivial but I am having trouble proving it as the Miller indices are reciprocals but the reciprocal is not distributive. This isn't for homework by the way - I...
  29. P

    2-methyl, 3-phenylbutane structure?

    is this this the correct structure for 2-methyl, 3-phenylbutane?
  30. M

    Ideas for a lecture in new technologies in aircraft structure

    ideas for a lecture in "new technologies in aircraft structure" Hi everybody... One of my doctors wants to give a practical and a little technical lecture about "new technologies in aircraft structure" and he is requisting ideas from us... What practical ideas can be presented ...
  31. Y

    As i know, the metallic structure for example a pure copper metal

    As i know, the metallic structure for example a pure copper metal which is made up of all metal atoms that is the copper atoms actually have all its atom of metallic element bonded together by metallic bonding. Metallic bonding is the electrostatic force of attraction between the positively...
  32. U

    Need help with structure of stair climbing robot

    Im supposed 2 design a robo like this 1, but here, the mechanical part seems more tought thn the electrical and programming. I couldn’t make out what mechanical structure is being used to have this type of motion. Can anyone please help. Here’s a start: There r 2 motors attached in the...
  33. C

    Naming the following benzene structure

    Homework Statement Homework Equations - The Attempt at a Solution i understand that benzoate is derived from carboxylic acid (COOH) to which isopropyl has replaced the H, forming a benzoate substituent to which we derive the parent name of the structure. I understand that Chloro...
  34. O

    What property of molecule structure can be a conductor - electricity?

    As we know, plastic is non-conductor, iron metal is conductor, does anyone have any suggestions on what kind of property in term of molecule structure allows electricity to get through? Thanks in advance for any suggestions
  35. S

    Why in periodic table normally we have elements with FCC and HCP structure?

    what is basic principle followed by atoms to arrange in basic structure?
  36. H

    Are all acid have covalent structure in solid state?

    Are all acid have covalent structure in solid state?
  37. J

    Protein structure drawing method

    Protein structure drawing method I want to know the proper name given to this particular method of drawing proteins, RNA and Genes. I have two examples; If you look at the Wikipedia page for tRNA, they show the Tertiary structure of tRNA like this...
  38. J

    Identifying proteins by structure

    Identifying proteins by structure Can proteins be identified by their structural image alone? What do i mean by that? Well i understand the basics of protein folding and protein structure. I have a basic understanding of primary, secondary and tertiary structure of DNA/RNA. But i want to...
  39. D

    How to prove there is no primitive cell of diamond structure with only one atom?

    How to prove there is no primitive cell of diamond structure with only one atom? Thanks in advance!
  40. C

    MATLAB Matlab: Using the exist function within a structure

    Hi All, Does anyone if it's possibe to use the 'exist' function in Matlab to check whether any data has been entered into a particular field of a structure. I'd like something like the following, where 'identification' is a user-input variable, 'team' is the structure and 'city' is the field...
  41. W

    What is the Structure of Ganglioside and Its Variants GM1, GM2, and GM3?

    what is the general structure of ganglioside? and what are the differences between GM1, GM2 and GM3?
  42. S

    Fermi level, band structure of solids, and effect on electrical conduction

    how is the relationship between fermi level and band structure of solids can effect electrical conduction properties of a material?
  43. P

    What is the bond order of NO-, NO, and NO+?

    Homework Statement Bond Order of NO- Bond Order of NO Bond Order of NO+ Homework Equations No Equations The Attempt at a Solution I determined the Bond order of NO+ to be 3 due to their triple bond and the Bond order of NO- to be 1 due to their single bond Lewis Structures...
  44. B

    Def./Examples of Spin Structure Re Trivial Bundles?

    Hi, All: I am reading a paper in which , if I understood well, a spin structure in a manifold M is equivalent to M admitting a trivialization of the tg.bundle over the 1-skeleton of M ( I guess M is assumed to be "nice-enough" so that it is a simplicial complex ) so that...
  45. K

    Does metal coating on porous silicon have any effect on band structure?

    Metal nanoparticles (Au, Ag, Al or ...) can coat on porous silicon, the particles can be located inside the pores or on the silicon micro/nano structures. By applying this type of coating is there any change in band structure of porous silicon? As I've measured the band gap has changed.
  46. N

    What is a Space Structure in relativity?

    What is a "Space Structure" in relativity? I remember reading an article that said essentially that the point of reference and the number of "space structures" affect the speed of light. Is this a popular theory? What is a space structure in physics anyway, I'm pretty well versed in physics and...
  47. C

    MATLAB Matlab: dynamic data entry into structure

    Hi all, I've created a structure containing various fields of data. The data in these fields is stored in matrices and is be added to at regular intervals. I'd like the system to identify the amount of inputs the fields already contain and then extend said matrices to include this new data...
  48. Saitama

    How Is the Radius r Related to Quantum Number n in Bohr's Model?

    Homework Statement A small particle of mass m moves in such a way that P.E.=-1/2mk(r)^2, where k is a constant and r is the distance of the particle from the origin. Assuming Bohr's model of quantization of angular momentum and circular orbit, r is directly proportional to: (a)n2 (b)n...
  49. L

    CSCL Crystal Structure - Confused by Clarity?

    Hello, I'm really confused by something. Cscl is simple cubic. But how it this possible? With the cl in the middle it looks like a bcc structure. Also howcome when you have 2 caesium its bcc and not simple cubic? its the same structure yet it changes to bcc. Is it because they are both atoms...
  50. A

    Observational evidence for bottom-up structure formation

    I know that the only dark matter models consistant with the cosmic microwave background radiation require bottom-up structure formation, but all of the relevant press releases I've read are about finding surprisingly large/mature structures in the early universe. Do the same...
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