Solar tracker

A solar tracker is a device for orienting a solar photovoltaic panel or concentrating solar reflector or lens toward the sun. Concentrators, especially in solar cell applications, require a high degree of accuracy to ensure that the concentrated sunlight is directed precisely to the powered device, which is at (or near) the focal point of the reflector or lens. Non-concentrating applications require less accuracy, and a tracker is not necessary, but can substantially improve the amount of power produced by a system by enhancing morning and afternoon performance.

Plesiosaur

Plesiosaurs(Greek: plesios meaning 'near' or 'close to' and sauros meaning 'lizard') were carnivorous aquatic (mostly marine) reptiles. After their discovery, they were somewhat fancifully said to have resembled "a snake threaded through the shell of a turtle", although they had no shell. The common name 'plesiosaur' is applied both to the 'true' plesiosaurs (Suborder Plesiosauroidea) and to the larger taxonomic rank of Plesiosauria, which includes both long-necked (elasmosaurs) and short-necked (polycotylid) forms. Short-necked, large-headed plesiosaurs are more properly called pliosaurs. There were many species of plesiosaurs and not all of them were as large as Liopleurodon, Kronosaurus or Elasmosaurus.

Proportional control

When controlling the temperature of an industrial furnace, it is usually better to control the opening of the fuel valve in proportion to the current needs of the furnace. This helps avoid thermal shocks and applies heat more effectively.

Proportional negative-feedback systems are based on the difference between the required set point (SP) and measured value (MV) of the controlled variable. This difference is called the error. Power is applied in direct proportion to the current measured error, in the correct sense so as to tend to reduce the error (and so avoid positive feedback). The amount of corrective action that is applied for a given error is set by the gain or sensitivity of the control system.

Living systems theory

Living systems theory is an offshoot of Bertalanffy's general systems theory, created by James Grier Miller, which was intended to formalize the concept of "life". According to Miller's original conception as spelled out in his magnum opus Living Systems, a "living system" must contain each of 20 "critical subsystems", which are defined by their functions and visible in numerous systems, from simple cells to organisms, countries, and societies. In Living Systems Miller provides a detailed look at a number of systems in order of increasing size, and identifies his subsystems in each.

James Grier Miller (1978) wrote a 1,102-page volume to present his living systems theory. He constructed a general theory of living systems by focusing on concrete systems—nonrandom accumulations of matter-energy in physical space-time organized into interacting, interrelated subsystems or components. Slightly revising the original model a dozen years later, he distinguished eight “nested” hierarchical levels in such complex structures. Each level is “nested” in the sense that each higher level contains the next lower level in a nested fashion.