mechanism (redirected from Mechanisms)

mechanism, philosophical theory about the nature of organic systems, holding that organisms are machines in the sense that they are material systems. Mechanism seeks to explain biological processes, including behavior, within the framework of classical physics and chemistry. The mechanistic approach has caused great controversy and is considered by its opponents, including vitalists (who contend that living organisms must be explained in terms of a mysterious self-determining principle rather than in physical or chemical terms) as inadequate and oversimplified.

Bibliography

See A. R. Anderson, Minds and Machines (1964); R. E. Schofield, Mechanism and Materialism (1969).

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mechanism

In mechanical construction, the means of transmitting and modifying motion in a machine or an assembly of mechanical parts. The chief characteristic of the mechanism of a machine is that all members have constrained motion; that is, the parts can move only in certain ways in relation to each other. Despite its complexity, the mechanism of a machine can always be analyzed as a group of simple basic mechanisms, each of which contains members that transmit motion from one moving link to another. In general, motion is transmitted in one of three ways: by a wrapping connector such as a chain drive or belt drive, by direct contact as in a cam or gear, or by a pin-connected linkage.

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mechanism

Form of materialism that holds that all natural processes can be explained in terms of laws of matter in motion. Upholders of mechanism were mainly concerned with eliminating from science all occult entities, such as substantial form, that could not be empirically observed or mathematically treated. It thus opposed the use of teleological assumptions as explanatory principles in natural science (see teleology). See also atomism.

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mechanism

1. a system or structure of moving parts that performs some function, esp in a machine

2. any form of mechanical device or any part of such a device

3. Philosophy

a. the doctrine that human action can be explained in purely physical terms, whether mechanical or biological

b. the explanation of phenomena in causal rather than teleological or essentialist terms

c. the view that the task of science is to seek such explanations

d. strict determinism

4. Psychoanal

a. the ways in which psychological forces interact and operate

b. a structure having an influence on the behaviour of a person, such as a defence mechanism

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Mechanism

Classically, a mechanical means for the conversion of motion, the transmission of power, or the control of these. Mechanisms are at the core of the workings of many machines and mechanical devices. In modern usage, mechanisms are not always limited to mechanical means. In addition to mechanical elements, they may include pneumatic, hydraulic, electrical, and electronic elements. In this article, the discussion of mechanism is limited to its classical meaning. See Machine

Most mechanisms consist of combinations of a relatively small number of basic components. Of these, the most important are cams, gears, links, belts, chains, and logical mechanical elements. The last include such devices as ratchets, trips, detents, and interlocks. In order to understand how any mechanism works, their degree of freedom, structure, and kinematics must be considered. See Cam mechanism, Gear, Linkage (mechanism)

Degree of freedom is conveniently illustrated for mechanisms with rigid links. The discussion is limited to mechanisms which obey the general degree-of-freedom equation, where F = degree of freedom of mechanism, l = number of links of mechanism, j = number of joints of mechanism, f_i = degree of freedom of relative motion at ith joint, σ = summation symbol (summation over all joints), and λ = mobility number (the most common cases are λ = 3 for plane mechanisms and λ = 6 for spatial mechanisms).

The kinematic structure of a mechanism refers to the identification of the joint connection between its links. Just as chemical compounds can be represented by an abstract formula and electric circuits by schematic diagrams, the kinematic structure of mechanisms can be usefully represented by abstract diagrams. The structure of mechanisms for which each joint connects two links can be represented by a structural diagram, or graph, in which links are denoted by vertices, joints by edges, and in which the edge connection of vertices corresponds to the joint connection of links; edges are labeled according to joint type, and the fixed link is identified as well. Thus the graph of the slider-crank mechanism of illustration a is as shown in illustration b. In this figure the circle around vertex 1 signifies that link 1 is fixed.

Kinematics is divided into kinematic analysis (analysis of a mechanism of given dimensions) and synthesis (determination of the proportions of a mechanism for given motion requirements). It includes the investigation of finite as well as infinitesimal displacements, velocities, accelerations and higher accelerations, and curvatures and higher curvatures in plane and three-dimensional motions.

The design of mechanisms involves many factors. These include their structure, kinematics, dynamics, stress analysis, materials, lubrication, wear, tolerances, production considerations, control and actuation, vibrations, critical speeds, reliability, costs, and environmental considerations. Modern trends in the design of mechanisms emphasize economical design analysis by means of computer-aided design techniques.