Optimal work-rest schedules under prolonged vibration.
This research was conducted for the purpose of studying the performance and recovery characteristics of men when subjected to low-level, whole-body vertical sinusoidal vibration for durations of one to two hours. Several male subjects performed a vertical compensatory tracking task using a CKT display according to three work-rest schedules under both normal and vibratory environments. The vibratory environment was that of vertical sinusoidal vibration with a frequency of.5 cps and an amplitude- of 0-08 inches resulting in an acceleration intensity of approximately 0.20 g. The working period was divided into equal intervals during which performance was continuously monitored. Decrement of performance was measured using absolute error score. Results and conclusions are presented regarding performance decrement and recovery under varying work-rest schedules. Optimum work-rest schedules and implications of control tasks under a vibratory environment are discussed.
Research Note: Personal Characteristics and Whole Body Vibration
Review of the research on human perforApparatrts mance in a vibration environment leads, in agreement with the opinion of Buckhout (1964), to conflicting findings. Hornick (1962, p. 326) said “While there is a common core of findings, enough conflict exists in the literature to merit questioning the basis of such discrepancy.” Hornick cites procedural variations and subject age, sex, intellectual status, physical differences, motivation, and experience levels as sources of the conflicting results. Linder (1962, p. 939) states “the personal, psychophysical, and physiological responses of a human to vibration determine his performance in a given task.” Goldman and von Gierke (1961, p. 44) remark “Control of, and compensation for. the nonuniformity in size, shape, sensitivity, and responsiveness of people. . . .” The purpose of this study was the investigation of the relationships between certain individual human parameters and performance decrement due to whole body, sinusoidal vibration. The parameters investigated were subject height, weight, age, chest circumference, waist circumference, estimated proportion of body fat, estimated puImonary condition, time ofday ofperformance, and each subject’s opinion of his motivational level. The subject’s task was one-dimensional, vertical compenVibratiori platfonti. The vibration was provided by a mechanical shake table. The driving force was supplied by a variable-speed electric motor connected by a V-belt to a doubly eccentric camshaft. A metal stool was mounted in the approximate center of the platform so that the force was transmitted vertically through the approximate center of gravity of a subject. Perfoniiatice console. A performing console was mounted in front of the metal stool. A cathode-ray tube (CRT) was placed in the center of the console. On the CRT the tracking task was presented in the form of a small dot moving vertically above and below a fixed horizontal black line. The subject provided compensatory input to the trackingsystem by moving a control handle with his right hand. Track iq task. The tracking signal was prerecorded on magnetic tape as an FM signal. During the experiment the tape was played back and the signal was converted to a DC voltage. This voltage was then summed with the compensatory input signal from the control handle. The resulting voltage represented tracking error. An electronic integrating network measured absolute error over the first 50 sec of each min.
A new power measuring circuit using a bridge-connected magnetic circuit and another magnetic core
The authors describe the operating characteristics of an oscillating circuit using a bridge-connected magnetic circuit and another magnetic core. A square-shape output voltage is obtained in the oscillating circuit. The pulsewidth in positive and negative half cycles of output voltage changes with the current of the U-form core windings and with the signal voltage applied to the exciting windings. The mean value of the output voltage varies in proportion to the product of the current and the signal voltage. Utilizing this feature, an application of the oscillating circuit to a novel power measuring circuit of simple construction is presented. >