Z94.9 Human Factors (Ergonomics) Engineering

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WAIST DEPTH. The horizontal distance between the back and abdomen at the level of the greatest lateral indentation of the waist (if this is not apparent, at the level at which the belt is worn).

WARM-UP TIME. Time measured from the application of power to an operable system to the instant when the system is capable of functioning in its intended manner.

WARNING. A signal, statement, or label indicating the existence of hazardous conditions.

WATCHKEEPING. That task in which the operator monitors some condition such as the status of automatic equipment.

WEAK COLOR. A color of low saturation.

WEBER-FECHNER LAW. An approximate psychophysical law relating degree of response or sensation of a sense organ and the intensity of the stimulus.

WEBER’S LAW. A law that states that for each sense parameter the ratio between the just noticeable difference and the stimulus intensity remains constant.

WEIGHTLESSNESS. (1) A condition in which no acceleration, whether of gravity or other force, can be detected by an observer within the system in question. (2) A condition in which gravitational and other external forces acting on a body produce no effect, either internal or external on the body. (3) The absence of gravitational pull on a body or object. (4) Condition in free fall or in space beyond the earth’s gravitational field; may be simulated by air-bearing devices or during parabolic flight of high-performance aircraft. (5) A condition that is characterized by the absence of gravity. For clarity, it has been proposed that the term zero g or null g be used to refer to the physical state of an object or body and that the term weightlessness be used to refer to the physiological and psychological experience of living organisms under zero g conditions.

WHITE NOISE. (1) Randomly fluctuating noise. (2) The noise that is heard when many sound waves of different lengths are combined so that they reinforce or cancel one another in a non-uniform fashion. (3) A noise for which the spectrum density is substantially independent of frequency range. (4) A sound or electromagnetic warehouse spectrum is continuous and uniform as a function of frequency.

WHITEOUT. An atmospheric and surface condition in the arctic in which no object casts a shadow, the horizon being indiscernible, and only very dark objects being seen.

WINDCHILL. A commonly used scale for expressing the severity of cold environments, indicates the effects of wind velocity and temperature combined.

WORK. (1) Expression for human effort measured in physical units, or specific output results. (2) General description of task.

WORK CYCLE. The total series of actions and events which characterizes or describes a work assignment or single operation.

WORK PACE. The rate at which a task or activity is done. Work may be paced externally, as by machine or mission rates, or self-paced by the worker.

WORK PHYSIOLOGY. The study of bodily responses to physical and mental effort. Includes measures of stress on the cardiovascular, respiratory and musculoskeletal systems in particular.

WORK REST CYCLE. The ratio of work time to non-work time. The larger the ratio the more opportunity there is for fatigue.

WORKSPACE. The physical area in which an individual performs some duty or task.

WORK SPACE LAYOUT. A design of work area or work station to include provisions for seating, physical movement of human operators, operational maintenance, and other factors permitting adequate person-to-person contact and man-machine interaction.

WORK STUDY. Analysis of work methods, techniques, and procedures.


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