Astructure is an arrangement and organization of interrelated elements in a material object orsystem, or the object or system so organized.[1] Material structures include man-made objects such asbuildings andmachines and natural objects such asbiological organisms,minerals andchemicals. Abstract structures includedata structures incomputer science andmusical form. Types of structure include ahierarchy (a cascade of one-to-many relationships), anetwork featuring many-to-manylinks, or alattice featuring connections between components that are neighbors in space.
Buildings,aircraft,skeletons,anthills,beaver dams,bridges andsalt domes are all examples ofload-bearing structures. The results ofconstruction are divided intobuildings andnon-building structures, and make up theinfrastructure of a human society. Built structures are broadly divided by their varying design approaches and standards, intocategories including building structures,architectural structures, civil engineering structures and mechanical structures.
The effects of loads on physical structures are determined throughstructural analysis, which is one of the tasks ofstructural engineering. Thestructural elements can be classified as one-dimensional (ropes,struts,beams,arches), two-dimensional (membranes, plates,slab,shells,vaults), or three-dimensional (solid masses).[2]: 2 Three-dimensional elements were the main option available to early structures such asChichen Itza. A one-dimensional element has one dimension much larger than the other two, so the other dimensions can be neglected in calculations; however, the ratio of the smaller dimensions and the composition can determine theflexural andcompressive stiffness of the element. Two-dimensional elements with a thin third dimension have little of either but can resist biaxial traction.[2]: 2–3
The structure elements are combined instructural systems. The majority of everyday load-bearing structures aresection-active structures like frames, which are primarily composed of one-dimensional (bending) structures. Other types areVector-active structures such astrusses,surface-active structures such as shells and folded plates,form-active structures such as cable or membrane structures, and hybrid structures.[3]: 134–136
Load-bearing biological structures such as bones, teeth, shells, and tendons derive their strength from a multilevel hierarchy of structures employing biominerals andproteins, at the bottom of which arecollagen fibrils.[4]
Inbiology, one of the properties oflife is its highlyordered structure,[5] which can be observed atmultiple levels such as incells,tissues,organs, andorganisms.
In another context, structure can also observed inmacromolecules, particularlyproteins andnucleic acids.[6] The function of these molecules is determined by their shape as well as their composition, and their structure has multiple levels.Protein structure has a four-level hierarchy. Theprimary structure is the sequence ofamino acids that make it up. It has apeptide backbone made up of a repeated sequence of a nitrogen and two carbon atoms. Thesecondary structure consists of repeated patterns determined byhydrogen bonding. The two basic types are theα-helix and theβ-pleated sheet. Thetertiary structure is a back and forth bending of the polypeptide chain, and thequaternary structure is the way that tertiary units come together and interact.[7]Structural biology is concerned withbiomolecular structure of macromolecules.[6]
Chemical structure refers to both molecular geometry and electronic structure. The structure can be represented by a variety of diagrams calledstructural formulas.Lewis structures use a dot notation to represent thevalence electrons for an atom; these are the electrons that determine the role of the atom in chemical reactions.[8]: 71–72 Bonds between atoms can be represented by lines with one line for each pair of electrons that is shared. In a simplified version of such a diagram, called askeletal formula, only carbon-carbon bonds and functional groups are shown.[9]
Atoms in a crystal have astructure that involves repetition of a basic unit called aunit cell. The atoms can be modeled as points on alattice, and one can explore the effect ofsymmetry operations that include rotations about a point, reflections about a symmetry planes, andtranslations (movements of all the points by the same amount). Each crystal has a finite group, called thespace group, of such operations that map it onto itself; there are 230 possible space groups.[10]: 125–126 ByNeumann's law, the symmetry of a crystal determines what physical properties, includingpiezoelectricity andferromagnetism, the crystal can have.[11]: 34–36, 91–92, 168–169
A large part ofnumerical analysis involves identifying and interpreting the structure of musical works. Structure can be found at the level of part of a work, the entire work, or a group of works.[12] Elements of music such aspitch,duration andtimbre combine into small elements likemotifs andphrases, and these in turn combine in larger structures. Not all music (for example, that ofJohn Cage) has ahierarchical organization, but hierarchy makes it easier for a listener to understand and remember the music.[13]: 80
In analogy tolinguistic terminology, motifs and phrases can be combined to make complete musical ideas such assentences andphrases.[14][15] A larger form is known as theperiod. One such form that was widely used between 1600 and 1900 has two phrases, anantecedent and aconsequent, with a halfcadence in the middle and a full cadence at the end providing punctuation.[16]: 38–39 On a larger scale are single-movement forms such as thesonata form and thecontrapuntal form, and multi-movement forms such as thesymphony.[13]
A social structure is a pattern of relationships. They are socialorganizations of individuals in various life situations. Structures are applicable to people in how a society is as a system organized by a characteristic pattern of relationships. This is known as the social organization of the group.[17]: 3 Sociologists have studied the changing structure of these groups.Structure and agency are two confronted theories about human behaviour. The debate surrounding the influence of structure and agency on human thought is one of the central issues in sociology. In this context,agency refers to the individual human capacity to act independently and make free choices.Structure here refers to factors such associal class,religion,gender,ethnicity, customs, etc. that seem to limit or influence individual opportunities.
Incomputer science, a data structure is a way of organizing information in acomputer so that it can be used efficiently.[18] Data structures are built out of two basic types: Anarray has an index that can be used for immediate access to any data item (someprogramming languages require array size to beinitialized). Alinked list can be reorganized, grown or shrunk, but its elements must be accessed with apointer that links them together in a particular order.[19]: 156 Out of these any number of other data structures can be created such asstacks,queues,trees andhash tables.[20][21]
In solving a problem, a data structure is generally an integral part of thealgorithm.[22]: 5 In modern programming style, algorithms and data structures areencapsulated together in anabstract data type.[22]: ix
Software architecture is the specific choices made between possible alternatives within a framework. For example, a framework might require a database and the architecture would specify the type and manufacturer of the database. Thestructure of software is the way in which it is partitioned into interrelated components. A key structural issue is minimizing dependencies between these components. This makes it possible to change one component without requiring changes in others.[23]: 3 The purpose of structure is tooptimise for (brevity, readability, traceability, isolation and encapsulation, maintainability, extensibility, performance and efficiency), examples being:language choice,code,functions,libraries,builds,system evolution, or diagrams forflow logic anddesign.[24] Structural elements reflect the requirements of the application: for example, if the system requires a high fault tolerance, then a redundant structure is needed so that if a component fails it has backups.[25] A high redundancy is an essential part of the design of several systems in theSpace Shuttle.[26]
As a branch of philosophy,logic is concerned with distinguishing good arguments from poor ones. A chief concern is with the structure of arguments.[27] An argument consists of one or morepremises from which a conclusion isinferred.[28] The steps in this inference can be expressed in a formal way and their structure analyzed. Two basic types of inference arededuction andinduction. In avalid deduction, the conclusion necessarily follows from the premises, regardless of whether they are true or not. An invalid deduction contains some error in the analysis. An inductive argument claims that if the premises are true, the conclusion is likely.[28]
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