Microdefocusing method for measuring acoustic properties using acoustic microscope

Many papers have been reporting on measuring acoustic properties of materials by acoustic microscopy. In a conventional method of V (z) curve analysis, the phase velocity and the propagation attenuation of a leaky surface acoustic wave (LSAW) are determined from the interference period Deltaz and the slope of the V(z) curve, respectively. For this method it is necessary to measure the V(z) curve for a period several times as long as the interference period Deltaz. Therefore, it is difficult to measure the acoustic properties of a sample with high resolution by the method. In order to overcome these problems, a method called the microdefocusing method is proposed. The method determines the acoustic properties of a sample by analyzing V (z) values measured in the microdefocusing region within an interference period Deltaz near a focal plane. An ultrasonic transducer called the butterfly transducer is proposed to be applied to this microdefocusing method and a digital signal processing procedure is developed to analyze the output of the ultrasonic transducer. Basic experiments are performed to confirm the principles of the new method.     

The effect of appraisers in estimating metabolic rate with the Edholm scale

A study was made of the appraisers' effect on the estimation of metabolic rate with the Edholm scale and a table of the ISO 7243 heat stress standard. The appraisers, five experienced and five inexperienced persons, estimated the metabolic rate of three different work tasks from videotapes. Analysis of variance indicated significant ( [Formula: see text] ) differences in the appraisers' recordings of the activities. The appraisers were grouped according to the similarity of the estimated values they gave. The groups thus contained both experienced and inexperienced appraisers, and it was not possible to classify the appraisers into experienced and inexperienced groups according to their earlier experience. The metabolic rates according to the Edholm scale were higher than according to the ISO 7243 table. The differences in metabolic rates given by the individual observers varied from 38 to 118 W/m(2). The variations in the estimation of metabolic rates were greater when the Edholm scale was used. This variation caused considerable variation also in the predicted mean vote, PMV index. It is recommended that the appraisers be selected carefully, because it is not possible to know whether a randomly selected appraiser is an 'average' or an 'extreme' appraiser without a test. Before conducting extensive field surveys where several appraisers estimate the metabolic rates, it would be useful to arrange training in order to calibrate the levels of the Edholm scale as well as ISO method among the appraisers because training clearly unified the estimation.     

When is light work heavy? Components of the physical workload of sewing machine operators working at piecework rates

Epidemiologists have associated the job of sewing machine operators with a high incidence of musculoskeletal and other health problems, despite its classifications as light work according to energy expenditure criteria. An ergonomic analysis was undertaken in a trouser factory in order to describe components of the physical load of this work: force exerted, repetitions, time allocation and postures. Work activity of ten operators was observed and timed in situ, and forces were measured with a dynamometer. The time required to sew one seam is very short, 10-15 s per trouser leg. This short cycle is repeated more than 1500 times during the work day, involving quasi-continuous movements of the same parts of the body. The fact that movements are repeated so many times means that small details of the task assume a great importance. During the work day, a substantial force is exerted, only part of which can be measured with current technology. By these measurements, operators lift an average 406.1 kg of trousers per day and exert an average total force of 2858.4 kg with the upper limbs and 24 267.9 kg with the lower limbs. The work posture is static: seated with upper back curved and head bent over the sewing machine. Movements of the upper limbs involve abduction and adduction of the shoulders while exerting a force. For the same task, there is considerable variation in the dimensions of workstations. Interviews were conducted to determine the types of musculoskeletal complaints. The components of work activity could be treated to these complaints and to existing epidemiological data on musculoskeletal problems among sewing machine operators. This type of detailed examination can be applied by health and safety personnel to identify task components which could be changed to minimize the probability of musculoskeletal problems.     

试析中专计算机教学中如何提高学生能力水平

在以往中专计算机教学中比较重视理论知识,而忽视了对学生实际操作能力的培养,导致中专计算机专业毕业生在社会中就业中没有足够的竞争力。所以加强中专教学中学生能力的培养是非常必要的。本文主要对如何加强中专计算机教学中学生的创新能力、抽象思维能力、自学能力以及应用能力进行了深入的分析。     

Post-mortem glycolysis in rabbit Longissimus dorsi muscles following electrical stimulation

The effects of both high voltage and low voltage electrical stimulation were studied in rabbit Longissimus dorsi muscles. The rate of fall of pH as well as the activities of phosphorylase a, phosphorylase kinase, and phosphorylase phosphatase were measured. The effects on the yield, ATPase activities, and calcium permeability of the sarcoplasmic reticulum (SR) were also measured. Although only high voltage stimulation increased the post-stimulation rate of pH fall, both types of electrical stimulation increased the phosphorylase a activity, apparently by increasing the activity of phosphorylase kinase and destroying a large part of the phosphorylase phosphatase activity. Electrical stimulation reduced the yield of SR and increased its basal ATPase activity. It also increased the ability of the SR to retain accumulated calcium. We conclude that the different rates of pH fall observed following the two types of stimulation are due to the differential effects of these treatments on one of the ATPase activities, probably the myofibrillar ATPase.     

Physiological levels of androstenedione and testosterone in some edible tissues from calves, bulls and heifers

The physiological levels of androstenedione and testosterone in muscle, kidney and fat of calves, bulls and heifers were determined by RIA. The androstenedione showed the highest levels in fat and the lowest in muscle tissues. Testosterone showed the same distribution only in male animals, whereas in females the highest levels were in kidney. In fat tissue androstenedione was constantly higher than testosterone in all examined animals. In muscle tissue androstenedione levels were higher than those of testosterone in all female animals and in male calves, whereas testosterone was higher in bulls. Testosterone was the main androgen in kidney tissue in both young and adult animals, irrespective of sex.     

Fractional brownian motion: a maximum likelihood estimator and its application to image texture

Fractals have been shown to be useful in characterizing texture in a variety of contexts. Use of this methodology normally involves measurement of a parameter H, which is directly related to fractal dimension. In this work the basic theory of fractional Brownian motion is extended to the discrete case. It is shown that the power spectral density of such a discrete process is only approximately proportional to |f|a instead of in direct proportion as in the continuous case. An asymptotic Cramer-Rao bound is derived for the variance of an estimate of H. Subsequently, a maximum likelihood estimator (MLE) is developed to estimate H. It is shown that the variance of this estimator nearly achieves the minimum bound. A generation algorithm for discrete fractional motion is presented and used to demonstrate the capabilities of the MLE when the discrete fractional Brownian process is contaminated with additive Gaussian noise. The results show that even at signal-to-noise ratios of 30 dB, significant errors in estimation of H can result when noise is present. The MLE is then applied to X-ray images of the human calcaneus to demonstrate how the line-to-line formulation can be applied to the two-dimensional case. These results indicate that it has strong potential for quantifying texture.