What is Structures: Definition and 350 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. Y

    Capillary Action, Are there structures that aid it?

    Hello, I'm an art student trying to recreate this phenomenon, but maybe on a larger scale. I'm trying to create a sculpture that is able to do that. If I can rely on just structure and not worry about materials, that would be great, since my plan is to be able to 3D print it out of plastic...
  2. Jimster41

    Explanation for similar structures at different scales

    I hope this is the most appropriate place for this question... So the PF posted this cool set of pictures yesterday on FB. Hopefully the link below works. It shows how some really big things "look" similar to some really small things...
  3. M

    Questions of calculus of crystal structures

    We know the rule of cross product or Why here |absinΘ| = , and = c cos Φ in the above picture? Thanks for explanation.
  4. L

    Do FCC Structures only have a CN of 12?

    Hi all, Without first delving too deeply into the literature I wanted to ask if its is only permissible for FCC structures to have a coordination number of 12. In the case of lattice vacancies and/or distortion: wherein the atomic sites are slightly displaced; is there a kind of tolerence for...
  5. T

    Castigliano's Second Theorem on Curved Structures

    Homework Statement A semi-circular ring of stiffness EI and radius R is supported on an anchored hinge and on a roller hinge. A vertical load F is applied at the center. Determine the horizontal displacement of the roller support. Homework Equations The Attempt at a Solution So I apply a...
  6. H

    Structures, Beams: Proof of formulas for a beam

    Ok I'm struggling with something here. I am rusty so have probably just misunderstood something simple mathematically. There are equations to create the Bending moment diagram for each different type of beam subject to a UDL; cantilever, simply supported, fully fixed ends etc. However I just...
  7. praveenpandiyan

    Airys stress function -- structures

    Homework Statement For (fi)= (b/6) x*y3 +C*xy show that simply supported beam of 2L loaded concentrated load at mid span.,the stress function satisfy loading condition is (fi) .treat concentrated load as shear stress suitably distributed to shoot this function. so that intergtal of limit (h to...
  8. praveenpandiyan

    Solid Hollow Shaft Torsion Resistance: How Will It Change?

    Homework Statement internal diameter of a hollow shaft is two third of its external diameter .if it is melted and new solid shaft is made.what would happen to the shaft resistance of torsion. in percentage? Homework Equations as i know T/j=G*angle of twist/length. torsional...
  9. Fredrik

    What is a fiber bundle and how is it related to smooth manifolds?

    I was asked what a bundle structure is in a PM. I'm posting my reply here, to give others a chance to add comments. I didn't get to see the exact sentence in which the term "bundle structure" was used. I would guess that it was used informally to say that some smooth manifold is the total space...
  10. Y

    What really are resonance structures?

    This is a concept I have never really understood. I mean to say is how can we include such a thing in a theory? How can we use them if we know that they don't actually exist? Are they some sort of calculation tool?
  11. D

    Crystal structures of violet phosphorus and red phosphorus

    For violet phophorus,it seems that the crystal structures given by two websites are not the same.In Openstax CNX,the link is http://cnx.org/contents/f46e8679-ee00-4073-9f5e-a87ca9955a9e@25.9:67/Chemistry_of_the_Main_Group_El and the Figure 12 displays it as follows: But in Chemwiki,the link is...
  12. M

    Fortran Exploring Unimplemented Data Structures in C: Matrix Storage by Columns

    See attached image. I have never heard that before. Why wouldn't one be able to implement a data structure that stores a matrix by its columns using C? Is that true?
  13. M

    MHB Is it Possible? - Running a Program with Data Structures in Separate Files

    Hey! :o I have the main function of a program in a .c file. The main function uses data structures which are defined in an other .c file. And the main function uses also a .txt file to get some inputs. Is it possible to run the program if the main function is an other file as the definition...
  14. A

    How to detect simple carbon structures

    I'm in high school and I have a science project, I must test for carbon without testing gas emissions using the following materials. 1.) Take the center carbon rod out of a heavy duty battery and scrape some of the powder off/ or use it directly. 2.) Create a chemical test and/or process...
  15. A

    Chemistry Resonance Structures for a Certain Molecule

    Here attached is a question from my exam. My TA removed 1 point out of 7 for a reason. Can anyone decipher for what? There's the writing in red but it is illegible to me. I don't understand to what he refers by 8 and 6 t or +, or whatever he wrote. http://imgur.com/igpyp8V Or can anyone write...
  16. gfd43tg

    What is the order of traversal in this recursive fibonacci function?

    Hello, There are three different orders of traversal that we learned about ##\bullet## pre-order traversal ##\bullet## in-order traversal ##\bullet## post-order traversal Anyone know of any easy ways of remembering these 3 and how to order them? I have posted my lecture slides, but I could...
  17. K

    Engineering Structural engineer - vehicle structures after civil degree?

    Hi, I'm an engineering student in Civil/Structural engineering and am interested in structures. As well as fixed structures I am also interested in mobile structures like ships. Can I get a job designing vehicle structures after graduating from a degree focused on civil structures? Would the...
  18. A

    What topic is "conditional structures" under?

    So i have a book that covers the fundamentals one needs to know before starting C++. I'm self teaching myself so i don't have to take the intro programming class at school. Anyways, our professor sent us all a email that among a few other other topics (such as arrays and functions and loops), we...
  19. A

    Chemistry Resonance Structures for a Certain Molecule

    Please look at the pictures. I do not understand why they have not included the resonance structure for that molecule for which all the double bonds are displaced is not included.
  20. Q

    Figuring out Primary/Secondary/Tertiary Structures

    Homework Statement In general, when presented with a problem such as write out all the primary alcohols/amines/ketones/aldehydes with this formula ________, how do I actually go about systematically figuring them out? I have seen problems with up to 8 different structures for me to figure...
  21. Q

    Chair Conformations of Cyclohexane - equivalent structures?

    Homework Statement Are these structures equivalent? Here's the professor's rendering: http://i.minus.com/jnojtCx6wYvqD.png The Attempt at a Solution Here's my rendering. The molecule is 1-chloro-2-ethylcyclohexane. I had projected the chlorine out of the page and the ethyl group into the page...
  22. A

    How to build different structures using programming

    Hi All, Greetings..! I am a master student in nanoelectronics from India. I wish to know how to generate nanostructures (for example as shown in figure attached) using programming (C/Python). Are there any algorithms or literature that discuss how some random structure of...
  23. Q

    Resonance structures for nitric oxide

    Homework Statement Is N triple bond O with a radical on oxygen a valid LS for the nitric oxide molecule? Homework Equations Max number of valence electrons in a shell - 2n2. Oxygen is in second row of periodic table. Max valence electrons: 2(2)2 = 8. The Attempt at a Solution I...
  24. U

    Lewis Dot Structures: Understanding Mistakes for Chemistry Tests

    So 3 days ago I had a chemistry test and part of the test included Lewis dot structures. I counted my valance electrons and distributed them equally but I have no Idea why I got these wrong.The second one I know why I got wrong but the rest of them look fine to me. I would really appreciate it...
  25. W

    Dividing Sets in Contact Structures, and Induced Orientations

    Hi everyone, a couple of technical questions : 1) Definition: Anyone know the definition of the induced orientation of a submanifold S of an orientable manifold M? 2)Dividing sets in contact manifolds: We have a contact 3-manifold (M3,ζ ). We define a surface S embedded in M3 to be a convex...
  26. A

    Choosing materials for space structures

    Interstellar travel is mostly a though experiment at this stage (although NASA will be launching the solar sail SunJammer in a couple of years). My question is a very broad one about what type of materials would be well-suited for structures to support interstellar travel. Any human habitat...
  27. M

    Problem from Aircraft Structures for Engineering Students - 5ed

    Hello to all , I need your help again , if you can . My question is about a problem / exercise book solved Aircraft Structures for Engineering Students - 5ed , example 20.4 . So the problem this section supports a vertical load of 10kN and the objective is to calculate the flow section...
  28. J

    Resonance Structures Chemistry: What is Potential Energy?

    I was reading this article from Wikipedia on resonance structures: http://en.wikipedia.org/wiki/Resonance_(chemistry ) What I do not understand is, what is meant by potential energy in terms of chemistry? In physics, potential energy is defined by location in a force field. What is it that...
  29. M

    Analysis of Structures Homework: Find Forces on Member AD

    Homework Statement A structure is made of 3 members, AD, AC, and BD (as shown in the attached image). A and B are NOT directly connected. There is also a pulley attached to D with radius 0.15 m. 1 end of the cable is attached to a 500 N weight, the other on is fixed in a horizontal sense. A is...
  30. R

    RCC structures and load bearing walls

    In modern buildings (I'm talking about taller structures, apartments, etc. not houses) that have a reinforced concrete framework are the internal / external walls (usually brick, masonry etc.) ever load bearing? In the sense is the strength / integrity of the structure ever depending or...
  31. J

    Convergence of different macromolecular structures with same function

    My professor had given us a lecture on the RNA World Hypothesis. He provided evidence for this hypothesis by citing the in-vitro selection experiments carried out on RNA. The outcome of one (or more) of these experiments resulted in the "creation" of an RNA polymerase ribozyme which totally...
  32. M

    Why Do Resonance Structures for ClO- and ClO4- Differ in Formal Charges?

    Hi, When drawing the resonance structures for ClO-, two exist. One where the O has a formal charge of -1 and there is then a single bond. The other structure is Cl with -1 for formal charge. Why is this second structure an equal resonance structure (why does the Cl have a negative formal...
  33. G

    What is the purpose of resonance structures?

    I`ve started reading up and practically making various resonance structures of various molecules. Though in the book I am reading I have only been subsituted with the information that it can be very necessary for chemical mechanics later on in the book. Is this correct? Also, the book doesn`t...
  34. J

    Understanding Mathematical Structures

    I have been studying topology and abstract algebra for some years, and for a lot of time I have been having a hard time trying to understand the definition and concept of "preservation of mathematical structures". For instance for binary operators a Homomorphism is said to preserve...
  35. N

    Finding Chiral Centres in Ring Structures

    How to find chiral centres of rings structures?For example take the following ringhttp://img203.imageshack.us/img203/7994/8vmq.jpg How to calculate no. of chiral centres?? thanks
  36. J

    Draw VSEPR Structures: CsF Ionic, Polar Covalent or Non-Polar?

    Homework Statement I'm supposed to draw VSEPR structures showing all valence electrons for the molecule. Draw in the partial charges δ+ and δ- if they exist. Classify the molecules as ionic, polar covalent or non-polar covalent. Some molecules may be of hypothetical existence. Homework...
  37. E

    Band structures with non-primitive cells

    How does one interpret band structures (i.e. E,k solution pairs for a given Hamiltonian) for a non-primitive cell? I was looking at these slides: http://www.tcm.phy.cam.ac.uk/castep/CASTEP_talks_06/clark2.pdf Slide 9 has the "normal" silicon band structure obtained with a primitive cell...
  38. M

    Help with lewis structures and resonance forms (CH3NCS)

    I need to write the lewis dot structure along with the 3 resonance forms for CH3CNS. This is what I had but it was wrong. Not sure what to do. Thanks.
  39. S

    3D Printed Tensile Structures in Space

    I was looking at this demonstration of a new kind of 3D printer: and I was wondering if this approach to 3D printing could be useful for creating structures in space, perhaps in Low Earth Orbit. I was wondering how these tensile types of structures could be put to practical use in space...
  40. tom.stoer

    Classification of manifolds and smoothness structures

    Except for the work of Torsten I am not aware of any paper which discusses these topics. Some ideas: 1) all theories for QG I am aware of do either use manifolds and smootheness (string theory, geometrodynamics, shape dynamics, ...) or are constructed from them (LQG, CDT, ...) 2) in some...
  41. M

    Need Intuition Behind Expansion of Smaller Structures in the Universe

    I am trying to understand what is meant when people say space itself is expanding. When I hear that, I imagine a 3-d Cartesian coordinate system in which every axis gets scaled at a given rate (like in an animation). What I don't understand is, if everything gets scaled, then how can...
  42. R

    Mathematical Logic and Structures

    URGENT ! Mathematical Logic and Structures Hey guys, i need a HUGE favor, i need the resolution for this 5 questions, its a question of end this year my degree or stay one year just with a subject. Please I am begging, who knows the resolution please say me something. Part 1...
  43. R

    Mathematical Logic and Structures

    URGENT ! Mathematical Logic and Structures Hey guys, i need a HUGE favor, i need the resolution for this 5 questions, its a question of end this year my degree or stay one year just with a subject. Please I am begging, who knows the resolution please say me something. Part 1...
  44. R

    Tournament-style payout structures using exponential growth

    Hello! Excuse me for my very basic understanding of math. I'll try and present my idea and problem clearly. I'd like to devise a payout structure for a tournament. 20% of the entrants will be paid. The payout will be an exponentially sloping function. The payout is in percentages that equal...
  45. M

    KNCalculating Member Forces in Truss Structures

    Attached is a picture of the truss. I am trying to calculate the member forces. I know a moment is = force * perpedicular distance, but in this case, for example, if i am taking moments about A, Would the equation be -(1*2KN)+(1*c) = 0 or using an alternative perpedicular distance...
  46. A

    Do we use these data structures?

    I have seen many data structures like stacks, queue, binary search tree, avl tree etc. Except stack and queue do we actually use these data structure outside the field of computers? Suppose I want to store by books(or any other stuff) according to some priority I would not use a binary heap...
  47. S

    Rate of thermal conduction in various copper structures

    A cylinder is constructed from a super insulator. The dimensions of the cylinder are Length L: 1 M; inside diameter i.d.: 12 mm. The entire Length of the cylinder contains copper (cases described below). Heat (T > 100C) is continuously applied to the copper on one end of the cylinder...
  48. H

    Close packed structures with bases

    Could we have close-packed structures with bases? Or, is it possible in close-packed structures that atoms of bases have arbitrary sizes? For example could we have a fcc close-packed structure with a two-atomic base (of any types of atoms)? If yes, what would happen if sizes of the bases be...
  49. L

    Can there be molecular structures according to QM?

    In molecular orbital theory, only the electrons are considered and from that we draw conclusions about molecular shape and such. I was thinking just now, what about the nuclei? If we apply QM to the nuclei as well, wouldn't that mean that we can't know where the atoms are? or is the...
  50. M

    Understanding Resonance Structures: Tips and Guidelines

    Hello, I am having difficulty discerning which resonance structures are considerable enough to include and which are so unimportant that they should be discarded. There seems to be no general rule on this that I can find, so I was wondering if such a rule existed or if someone can lead me in...
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