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.

View More On Wikipedia.org
Recent contents Top users
  1. A

    What is the IUPAC name for this structure?

    I am trying to find the IUPAC name for this structure. I a keep coming across 1,3-diol cyclohexane, but my homework online keeps saying its wrong. Does anyone know what this structure is? Thanks:)
  2. P

    Discover the Fascinating World of Fine Structure: Explained in Detail

    What is fine structure?
  3. M

    Chemistry - Lewis Structure question

    I understand the idea of the Lewis Structure and the octet rule. What I don't know is where to place the atoms. And unfortunately my book doesn't explain it. They just draw the lewis structur and expect us to understand how they did it. For example: Draw the lewis structure of H_2CO...
  4. A

    What Is the Correct Chemical Structure for Hexane?

    please help me name the structure. The structure is a hexane. I can't figure out how to label it. could it be: 2-methyl butane 3-bromo-4,5-ene, 5-propyl- chloro hexane?
  5. mnb96

    Limits of classical views of the atomic structure

    Hello, this might be a trivial question for many of you. I would like to know what are the simplest phenomena/experiments, if any, (and perhaps the first historically) that contradict the assumption that subatomic particles like electrons, protons, neutrons..., can be thought of as "small...
  6. W

    Temperture Structure Parameter CT2

    I understand the physics behind the Temperature Structure Paramter, but need help find a intial value to divided by. Here what I am trying to do. dB = 10 log 10 (CT2/CT2i) What I need is an intial value (CT2i) for the temperature Structure Parameter for a monostatic sodar. The units need...
  7. R

    Unit translation vectors, bcc structure

    Homework Statement Can someone please try to help me with this. I have a bcc structure and the question is ''Clearly indicate the unit translation vectors and state their value in Å. I have attached the sketch : http://img440.imageshack.us/img440/4879/picture3lh.jpg are those t1,t2,t3...
  8. P

    How to get reactions from given structure

    Can anyone tell me how to find the reactions of this structure? If not by summing forces and moments, then how? I'm thinking it's indeterminate and assumptions have to be made.
  9. M

    Engineering Challenge: Create a Balsa Wood Structure to Hold 3 15lbs. Weights!

    In my engineering class, we were told to create a structure out of balsa wood (1/8"x1/8") and glue. The structure has to suport the weight of 3 15lbs. weights (donut shape). We are only give 72" of balsa wood, and the structure must hold the 3 15lbs. weights for 1min. Sorry I am new to this...
  10. U

    What is the moleculer structure of tooth enamel?

    what is the moleculer structure of tooth enamel and is it similar to egg shells?
  11. M

    A tight biinding calcualtion of graphene like structure

    I plot the tight binding bandstructure of graphene. There is a very good aggrement with ab-inition calculation in the valence band. but there is a problem in the non-localized orbitals of conduction band especially in the Gama(0,0) point. Any suggestion is appreciated.
  12. T

    Correlation between electronic band structure of an atomic species

    Hii, I was wondering whether there is any correlation between the energy eigenvalues of a single atom (say He) with the electronic band structure of a collection of He atoms. for example, for He atoms the lowest energy would be the ground state, with 2 electrons. So will the lowest band for a...
  13. I

    Universal fractal structure and the infinite universe

    Disclaimer: I am a science buff – not a scientist. I am curious to know if there has ever been a theory developed about the infinite nature of the universe, large and small, relating to a fractal structure. I was pondering fractal subdivision, and how it offers at least the theoretical...
  14. M

    Question in material structure.

    Assuming atoms pack together as hard spheres , find the largest intenstihal atom that can fit in a BCC arrangement of iron atoms . Take the radius of the irom atoms as 1,21 Å . Carry out the same calculations for an FCC arrangment of iron atoms . On the basis of these caluclation would you...
  15. P

    Question on Number of Degrees of Freedom in a Simple Structure

    I have attached the problem drawing. Please refer to it. This is a lumped mass structure and all elements have the same Modulus of Elasticity and Moment of Inertia. Determine the number of degrees of freedom of the structure So I am thinking between 2 different scenarios. 1 scenario...
  16. P

    Preserving cycle structure in transpositions

    Hi all, long time reader first time poster! Just need a hand on this problem I've been stuck on for a few days Homework Statement Let r=(a_1,a_2...a_k) be in S_n. Suppose that ß is in S_n. Show that: ßrß^-1=(ß(a_1), ß(a_2)...ß(a_k)). Homework Equations The Attempt at a...
  17. S

    Cell Membrane: Structure and Function of the Phospholipid Bilayer

    All I can really think to talk about is how the phospholipid bilayer (i.e. hydrophobic tails, hydrophilic heads) is structured, and how that only allows certains certain molecules in (blocks out polar molecules (except H2O), large molecules in general, ions etc.), while the others require forms...
  18. R

    Band Structure of Charged Insulator

    Dear all, I have been thinking, if insulators have their valence band filled, then which band does the extra electrons go when it is negatively charged?? If it is the conduction band, then it would become a conductor... Similarly, if it is positively charged, there would be a hold in the...
  19. G

    Can You Decode a Band Structure Plot and Identify Corresponding Atomic Orbitals?

    Hi! I'm new here... I'm going to go right to the point. I know that when you take atoms and get them closer together, the discrete energy levels turn into bands. But when I'm facing a band structure plot, such as this one (band structure of aluminum nitride in wurtzite structure)...
  20. T

    Exploring the Compact Structure of Universe

    If the universe is filled with matter, and that matter causes space-time to bend, wouldn't the over-all structure be closed? Meaning, if I fly off in some random direction I would eventually "wrap around" the universe like a person moving across the surface of a sphere? If so, is this...
  21. D

    Static Equilibrium and Structure problems

    Homework Statement [PLAIN]http://broadcastsol.com/123.JPG Prob. 1. The structure of massless members is shown in the figure. Determine the reaction forces at the supports C, and forces in the rod EF and DG. Givens: P, a, b, c. Prob. 2. The structure of massless members is shown...
  22. C

    New open-shell molecular electronic structure program: What to do with it?

    Hello forum members, I got a nifty new multireference CI program at my hands and now I'm wondering what to do with it. The program is able to correlate general MCSCF wave functions, and as such basically any kind of molecular electronic structure imaginable; in particular also electronic...
  23. G

    Sulphur Dioxide (SO2) Geometry & Hybridization

    Hi I was trying to understand the geometry of Sulphur Dioxide molecule on the basis of hybridisation involved in the central atom. I found that Sulphur atom should have SP2 hybridisation. I want to know that is there any promotion of electron from 3 p-orbitals to 3d-orbitals and then forming...
  24. I

    Predicting molecular shape without drawing lewis structure

    Is their a method for predicting the molecular shape of molecules without drawing the Lewis structure? I am preparing for an ACS exam and would like to try to save some time on these problems. I think I could determine the steric number by counting the total electrons available, and...
  25. A

    Medical Eye Lens Structure: Circular & Radial Fibres

    I just studied the structure of the lens of the eye. And I found out that there are two type of fibres present, which were the Circular Fibres and the Radial Fibres. Can anyone please tell me what is the purpose or function of these two fibres ? Or simply they are just fibres which are...
  26. P

    Derive an expression for the Fermi energy of a 2D structure at 0 kelvin?

    Homework Statement That's basically the whole question in the title there, ie; Derive an expression for the fermi energy of a 2d structure at 0 kelvin. 2. The attempt at a solution Basically the first part of the question had us sketching the Fermi-Dirac distribution function at 0K for...
  27. L

    How does atomic structure relate to how well things share energy.

    Like, let's say substance A, in the sun, is very hot. After the sun goes down, it stays hot, but after awhile it becomes cold. Element B, in the sun, is also very hot, but after the sun goes out, it basically becomes cold immediately. Why is this?
  28. W

    How to determine band structure (E(k)) of a one dimensional crystal?

    Hi! I'm new to the physics forum but I've read a little bit and I'm impressed with the knowledge a lot of people have here. I've tried searching for any topic on my question without any luck. My question is simply what the algorithm is to determine the band structure for a one dimensional...
  29. M

    Space group for cubic structure

    Hello all, I am having trouble figuring out the space group for a cubic structure having A atoms at 000 and B atoms at 1/2 1/2 0, 1/2 0 1/2 & 0 1/2 1/2. Now, I know that it is Pm3m, but what is confusing me is why is there not a 4 fold axis at the first m, thus, giving you a P(4/m)3m...
  30. B

    NASA NASA'S Fermi Telescope Discovers Giant Structure In Our Galaxy

    Sorry if someone already posted this link but did anyone see this in the news? http://www.nasa.gov/home/hqnews/2010/nov/HQ_10-295_FERMI.html What are people's opinions on what this might be?
  31. R

    Fine structure of X-Ray transition

    What's the main reason behind the fine structure of X-Ray transition?
  32. A

    Building the World's Tallest Structure in Record Time!

    A crazed billionaire has a lifelong dream to build the world's tallest structure as a testament to his glory. Fearing competition, he decides that his tower must be far taller than any other in order to remain that way for as long as possible. The goal: build a 10 km tower, and do it in as...
  33. L

    Why the crystal momentum k in 2D band structure is defined on a torus?

    Hi, Could someone help to explain that why for the 2 D system, like 2 dimensional electronic gas, the crystal momentum k in 2D band structure is defined on a torus? Thanks a lot.:)
  34. F

    Drag force on a two-dimensional structure

    "A two-dimensional structure is tested in a wind tunnel with an air density of 1 kg/m3. The wind tunnel is 1 m high, with upstream and downstream pressures of 1.5 kPa gage (i.e. above atmospheric) and 1 kPa gage respectively. If the mean velocity of the entering air is 30 m/s and the downstream...
  35. G

    Structure using Proton NMR Spectrum

    Homework Statement Draw the skeletal structure of the compound with molecular formulaC3H4Cl4 whose proton NMR spectrum contains a down-field triplet and an up-field triplet with relative integration of 2:2. 2. Rationale for Solution Integration ratio of 2:2 means CH2-CH2, after this one carbon...
  36. H

    Question about the universe structure?

    question about the universe structure? I have a question. Does universe consist curved spacetime everywhere? , I believe there are plenty of flat spacetime, isn't it? . If it is so then eveywhere worm hole is not possible isn't it?
  37. M

    Tight Binding calculation of band structure

    Dear all, I want to calculate the band structure of graphene for a unit cell with 8 atoms in the Tight Binding approximation. There is no problem about drawing the band structure for a unit cell with 2 atoms. But by increasing the unit cell size, first brillouin decrease and there is a gap in...
  38. M

    Planes of simple cubic structure and X-ray diffraction experiment

    In the book of the Dr. Ronald Askeland the problem about x-ray diffraction use the next planes indices to calculate the interplanar distance, but I don't understand why to use such planes indices? Are these planes all of planes in a cubic structure? (111) (200) (211)...
  39. K

    Can gas density be permanently altered and what influences it?

    Can the density of gas be changed for good, or is the change just temporary? And what increases density in gases?
  40. Z

    How is the microscopic crystal structure visible?

    I just noticed that it's often taken for granted that a macroscopic crystal has a similar geometric structure as in the atomic scale. What is the physical explanation for this (assuming it is true)?
  41. A

    How Is the Distance to the CMB Measured and How Does It Relate to Its Structure?

    Hello, I'm new here and have joined to ask the following two questions: 1 - The distance to the CMB has been measured at approximately 14 billion light years. How was this achieved, what is the error and is it the same in all directions? 2 - WMAP data clearly shows that the CMB has a plane...
  42. D

    Ways on how visualize the deflected shape of a simple structure?

    Hi guys, what are some ways to visualize the deflected shape of a simple structure? I know that there is no slope or deflection at fix ends. No deflection at supports (roller, fix ends, etc). Also, I am not really sure what a kink is. Thanks
  43. T

    Another large scale structure of the universe idea

    Has the following explanation for the large scale structure of the universe been considered and discounted?Consider a universe many billions of times the size of the observable universe, so big that the homogeneous nature of the universe could even be an illusion. At a very large distance...
  44. D

    Fine structure, and hyperfine structure

    Hello... I was just reading about that, and I have one question. In the chapter I've jut read about, the overall headline is about one electron atoms, so I was just wondering, since the overall equation got Z (Atomic number) in it, if this was for larger atoms as well, or ONLY one electron...
  45. P

    How Do Atoms Behave When a Spring Loses Its Elasticity?

    What happens to the atoms in a spring when the spring looses its elasticity in hookes law? I am aware of the hookes law F =-kx but for my assignment i am also to state what happens to the atoms when the spring becomes plastic and deforms how and why? my asumtion is that they atoms...
  46. A

    Solid state physics - FFC structure of NaCl

    Homework Statement NaCl is a face-centred cubic with a basis at Na(0,0,0) and Cl at (a/2,a/2,a/2) and lattice parameter a = 5.63 angstrom. calculate the separation between nearesr neighbours (Na and Cl). The Attempt at a Solution Just by looking at the NaCl structure the separation...
  47. A

    Variation of fine structure constant and spacetime?

    Hi all, I'm going to ask a naive question - hope that's ok. There's been a lot of recent discussion of the results from Webb et al. which indicate that the fine structure constant varies spatially. I realize the results are very controversial - I'm wondering, hypothetically, if these...
  48. M

    Unit cell dimensions of crystal structure

    Hello all, I already have the answer to my question, but what I would like to know is why. My question is: why in the question below is the plane 111 used to find ao and not another plane? An ordered compound of NiAl has a cubic structure with one formula unit/cell. One Al atom at...
  49. S

    What is the structure of a magnetic field produced by DC and AC currents?

    I am not much of a mathematician, and I am trying to understand Maxwell's equations. I am trying to visualise the structure of a magnetic field produced in a straight wire firstly by a DC current, and secondly by an AC current. I think I understand but I just need to make sure that I have...
  50. C

    Structure of a gravitational wave?

    Questions concerning GW's are very common on PF, but I think I have a new question on the concept. Maxwell explains that EM waves(photons) propagate in space due to a relationship between the sinusoidal representations of the electric and magnetic fields of the wave. Namely that these...
Back
Top