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38648 results in Cambridge Textbooks

Page 1450 of 1933

  • 10 - Work Related MSDs Risk and Work Postures Assessment

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 203-227

  • Summary

    Introduction

    The reasons behind injuries in a variety of work-related circumstances have been possible to observe since last few decades. For example, consider the case of physically demanding jobs such as casting process in steel industries where a number of tasks involve heavy lifting, carrying, pulling, pushing and moving of equipment in awkward postures that may result into musculoskeletal disorders (MSDs). So, the primary cause of musculoskeletal disorders (MSDs) has been found as manual material-handling tasks.

    Likewise in the service industry, IT professionals devote six to eight hours on video display terminals (VDT) and consequently they undergo some MSD complaints. Employees of any organization, who are physically engaged in the task, are unknowingly exposed to the bad work posture. In hospitals the professionals such as dentists, ophthalmologists and nurses are exposed to frequent bending posture while attending patients. Similarly in manufacturing industry also the shop floor workers are working in bad postures, chronic effect of ergonomically bad posture could result in MSD complaints like low back ache, neck pain, wrist stiffness, etc. have been reported by different authors like; Singh et. al (2010). These further could result in low back injuries, cervical problems and carpals tunnel syndromes, etc. Therefore, it becomes very essential that as a preventive measure, the work posture of employees/workers must be investigated using suitable tools. Although, there are a number of ergonomic tools available for the MSD risk assessment out of which RULA (Rapid Upper Limb Assessment) and REBA (Rapid Entire Body Assessment) are the most prevailing for work posture assessment.

    The objective of this chapter is to make the reader understand about the procedural steps of using the ergonomic tools to analyze the working postures of an employee or workers. Hence the cases of workers engaged in various processes of small scale casting industry have been taken and discussed. The present chapter is confined to the used two assessments tools, i.e., Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA) that recommend the various body postural changes to be made while working.

    In 1993, McAtamney and Corlett develop an ergonomics tool known as RULA which is used to assess the risk of musculoskeletal disorders caused in sedentary tasks having high demand of upper body.

  • 13 - Occupational Noise Exposure

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 265-286

  • Summary

    Introduction to Noise

    Any unnecessary sound which creates disturbance to human is generally treated as noise. Thus any unnecessary sound is known as noise that results in disturbance and lowers quality of life which leads to sleep and mental/auditory fatigue. The annoying effect of noise, whether from a factory, motorway, marriage palace or nightclub, varies from person to person. Secondly, it can divert concentration and audible caution signals or interfere with occupation that may result into accidents. Finally exposure to excessive noise can result in hearing loss, provided the exposure period is of sufficient duration; for example, loud music may lead to hearing disorders.

    Sound

    The pressure difference in air, water or any other medium that is detected by human ear is known as sound. Physically, sound is a vibration of gas, liquid or solid medium particles.

    The nature of sound

    Sound is a mixture of many waves or fluctuations (sound waves) impinging on the eardrum. It is generated from any energy source setting up hasty and varying pressure in the nearby air. The rate at which variations occur, is called frequency or pitch, and is expressed in hertz (Hz), i.e., cycles per sec. One hertz means the number of complete air waves passing a fixed point per sec. The normal human ear is sensitive to frequencies between about 20 and 20,000 Hz being particularly sensitive in the range 2,000–6,000 Hz. (with maximum sensitivity at 4000 Hz.) that is less perceptive at elevated and lower frequencies.

    Characteristics of sound waves

    Sound having one frequency only is called as pure tone, such as sound produced by the tuning fork (see Figure 13.1 A). As components distributed over a wide range of frequencies, most of industrial noise are very complex, called broad band (see Figure 13.1 B). Noise produced by looms, an air jet industrial machinery or printing presses, are few examples.

    There is a significant noise due to impact between metal parts in steel industry setup. Due to a wide range of impacts per sec, noise is treated as broad band noise, as in a riveting machine. On the other hand noise having widely spaced impacts termed impulse noise, as drop hammer-operated hand tool (see Figure 13.1 C).

  • 11 - Office Ergonomics

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 228-250

  • Summary

    Introduction

    In current scenario every one working in the office is greatly dependent upon computers to perform work. Millions of people work with computers every day. Depending upon the type of job, some people perform dedicated computer work, while others do multiple tasks throughout the day. As people are diverse and ergonomics strives to fit the task to the person doing it, therefore, office ergonomics is concerned with the designing of office work place and is deliberated to help an individual for the assessment of the ergonomic design of computer workstation. Therefore office ergonomics help us to setup the job place as per the need of human comfort and provide basic tools to maintain a healthy workspace in the office. Some of the helpful tips show how to identify and correct ergonomic problems to prevent repetitive strain injury, eye strain, fatigue and discomfort.

    Issues in Workstation Design

    Whenever a work station or office is designed, most importantly the following issues are considered:

  • Body posture, back, neck, upper arms, lower arms, wrist extension and ulnar deviation

  • Keyboard and mouse

  • Typing speed

  • Hours spent using keyboard and mouse

  • Rest breaks

  • Overtime

  • Unaccustomed work

  • Lighting and glare

    • Body posture is the most significant aspect when considering the workstation design. Besides that, seat, job facing (working on VDT) aides, observations in maintaining the fine posture are also important. An ergonomically well-designed seat does not assure for accurate position although it provides some help to be in unbiased posture. It is up to the individual to learn and practise appropriate posture. The working posture can be analyzed using various ergonomic tools available, like RULA, which is described in the previous chapter.

    Sitting posture

    To identify the sitting posture, whether it is poor posture or good, one must be capable to reply a query; ‘what do you mean by good posture’? When using a computer, one may start with correct posture, but after some time change to slumping or forward bending posture. At a computer workstation, perfect posture is identified by observing the following points:

  • Head is upright and above the shoulders.

  • Eyes are in downward direction (30° from horizontal line of sight) without bending the neck.

  • Back must be supported by back-rest of the chair which encourages normal curvature of the lower back in lumbar region.

  • 12 - Physical Stresses

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 251-264

  • Summary

    Introduction

    The present chapter considers the aspects of physical stresses due to ambience, the omnipresent sensations to which worker is exposed from diverse sections of machinery or from other systems in his workplace. These ambiance pollutants mainly include vibration, the noise, the temperature, the illumination, etc. But the current chapter is confined to a brief description.

    Vibration

    Vibration is the most fundamental environmental factor. Therefore, it is essential to understand the definitions and parameters of structure-borne vibration, and it will help us understand the processes of other environmental parameters – particularly noise and, to a lesser extent illumination. A body is said to vibrate when it describes an oscillating motion about a fixed position. As like sound, the number of times a complete motion cycle takes place during the period of one second is referred to as the frequency, which is measured in hertz (Hz). The motion can consist of a single component occurring at a single frequency, as with a tuning fork, or of several components occurring at different frequencies simultaneously, e.g., with piston motion of an internal combustion engine.

    Vibration signals in practice usually consist of many frequencies occurring simultaneously, so that it is not possible to see immediately, just by the examination of; the amplitude–time pattern, how many components there are and at what frequencies they occur. These components can be revealed by plotting vibration amplitude against frequency, the process being known, as in case of sound as frequency analysis. The graph showing the vibration level as a function of frequency is known as frequency spectrogram, and the vibration amplitude is the characteristic which describes the severity of vibration.

    Frequency ranges of significance

    (a) The principal hazards associated with vibration are cold body vibration and condition known as vibration induced white finger (VWF), the physiological aspects of which are discussed in another subsequent section. The human body is most sensitive to vibration in the frequency range 1–80 Hz and is principally subjected to vibration in 3 supporting surfaces, viz., the feet of a person while standing, the buttocks of a seated person, and the supporting areas of a person lying down. In the longitudinal direction, i.e., feet to head, the human body is most sensitive to the vibration in the frequency range 4–8 Hz. In the transverse direction, however, it is the most sensitive to the frequency range 1–2 Hz.

  • 5 - Wages and Incentive Plans

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 116-132

  • Summary

    Introduction

    In any organization no work can be accomplished without involving manpower; hence, the efforts and time devoted by the manpower are payable in terms of wages and incentives. Before we discuss the various wages and incentive schemes, let us first define these terms. The term wages refers to the payment or remuneration made by the employer for the efforts put in by the worker, employee or staff. According to the Payment of Wages Act, ‘wages refer to all remunerations capable of being expressed in terms of money, which would, if the terms of the contract of employment, expressed or implied, were fulfilled; be payable to a person employed in respect of his or her employment or of work done in such employment and includes any bonus or other additional remuneration of the nature aforesaid which should be so payable’. Thus it may be observed that the wage is a contractual obligation of the management to be paid to the persons employed by them. Wages are tangible and have to be paid in terms of money. The basic wage of a worker, once fixed by the management, must not be altered and has to be paid irrespective of the quality or quantity of work.

    Incentive

    Incentive may be defined as an influence which tends to produce an increased effort on the part of the employee above a standard. It provides the stimulus to motivate the worker towards higher productivity. Incentives can be negative or positive. The disciplinary actions taken against non-compliance are termed as negative incentives. Psychologically negative incentives are not conducive to human-relations. Positive incentives refer to both extra financial and non-financial benefits provided by the management. Positive incentives would lead to increased production levels and productivity. Non-financial incentives are generally more welcome by the executives. Financial incentives are more effective with the workers.

    Incentive plan

    Incentive plan refers to financial incentive based on the wage structure. Incentive plan is a scheme of arrangement, which lays down a systematic procedure of payment to the employee based on the performance of the task set. It is developed in such a manner as to produce benefit to both the employee and the employer. The earnings of the worker bear a direct relationship to the quantity of output by the individual or by the group in which he/she belongs.

  • 16 - Dust Fumes and Respiratory System

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 312-331

  • Summary

    Introduction

    Dust is as an aerosol composed of solid inanimate (non-living) particles, as defined by the ILO. The term aerosol implies that airborne particles are carried in or contained in air which may be inhaled. An aerosol can embrace liquid droplets as well as solid particles.

    Some dusts are fibro-genic that causes fibrotic changes to lung tissue or toxic, they eventually poison the body systems. Examples of fibro-genic dust are silica, cement dust and certain metals, whereas toxic dust may include arsenic, mercury, beryllium, phosphorous and lead. Some toxic dust, such as arsenic, has an acute effect. Others, such as mercury, have a chronic effect. A number of dusts, although not harmful to health, can have a nuisance effect, for example, dust from combustion of solid fuels.

    Definitions Relevant to Dust and Fumes

    Particulate–It is a collection of solid particles, each of which is an aggregation of many molecules.

    Mist–It is airborne liquid droplets, e.g., oil mist.

    Fumes–These are airborne fine solid particulates formed from the gaseous state usually by vaporization or oxidation of metals, e.g., lead fume.

    Vapour–These are airborne liquid droplets given off from the surface of a volatile liquid, e.g., trichloroethylene.

    The Behavior of Dusts

    All dusts are potential aerosols and the behavior of particles is influenced by

  • (a) The rate of air movement,

  • (b) Brownian motion, that is the ‘joggling’ movement or effect imparted to submicron particles by molecular bombardment and

  • (c) The size, density and shape of the particle.

    • The unit of particle size is the micron, which equals one thousandth of a millimetre, designated µm.

    When a particle falls in air it does not accelerate indefinitely. Eventually it reaches a speed at which air resistance equals its weight, and thereafter it falls at constant speed, which is called as ‘terminal velocity’. That depends to a great extent upon its size and density.

    Physiology of the Human Lung

    The lungs are enclosed in the thoracic cavity and have a sponge-like elastic texture. There are expanded or compressed by movements of the thorax in such a way that air is repeatedly taken in and expelled. They communicate with the atmosphere through the trachea or windpipe, which opens into the pharynx. In the lungs, gaseous exchange takes place.

  • 2 - Human Factors in Work Study

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 16-23

  • Summary

    Introduction

    Work study is described as a management tool to achieve higher efficiency concerned chiefly with manual work. In order to survive, the industry must use latest technology and most efficient method improvised with a consistent aim of producing best quality goods at lower prices.

    One way to improve is through efficient utilization of plant, equipment and labour. Work study is specifically a study of work, describing partition of work into smaller units followed by rearrangement of these units to provide the same effective use at a minimum cost. Work study gives methodology and calculates time period required for the work involved in the process. Robert Owen, Taylor and Bedaux had their vital contributions to this particular topic. According to International Labour Organization (ILO), work study is defined as follows:

    Work study is primarily concerned with finding the best ways of performing job and establishing benchmarks based on such ways. It is the technique of method study and work measurement employed to ensure the best possible use of human and material resources in carrying out a specified activity.

    In other words, work study can be defined as “the systematic investigation of the methods, conditions and effectiveness of industrial work and thus to determine the way in which human efforts can be applied most economically”.

    Historical Glimpse Related to Work

    Industrial revolution started around 1770s, when James Watt gave steam engine and Henry Maudslay devised the screw-cutting lathe. In factories, automated machines started replacing workers to enhance production rapidly and more accurately. The interchangeability enabled the factories mass manufacturing. Better machines, modern parts, special tools, fixtures, etc., and then unique products replace custom-fabricate common products. Henry Ford (1863–1947) started mass production through assembly lines.

    The concept of scientific management came in late 1800s; Frederick W. Taylor (1856–1915) was the father of scientific management, whereas Frank (1868–1924) and Lillian Gilbreth (1878–1972), were the father and mother of motion studies. Frank Gilbreth was born in Freeport, Maine on 7 July 1868. After finishing school, Frank Gilbreth began to work for a construction company as an apprentice brick layer. At age 27, Frank Gilbreth became the chief superintendent of the company. By the time of his promotion, Frank Gilbreth developed a number of methods, both technical and procedural, for improving efficiency at the workplace, particularly in his field of construction.

  • 14 - Occupational Noise Induced Hearing Loss (NIHL)

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 287-303

  • Summary

    Introduction

    The most common condition associated with exposure to noise is occupational hearing loss. Occupational noise is an integral part of the job especially in iron and steel industries, noise may cause severe hearing loss. The hearing loss occurred due to occupational noise exposure is called as occupational noise induced hearing loss or occupational deafness. Worldwide, about 16 per cent of the hearing disability is caused by occupational noise exposure, according to Nelson et al. (2005). The workers in industries such as mining, construction, printing, crushers, drop forging, iron and steel companies are at high risk of NIHL (Nadi et al., 2008). When an individual is over-exposed to excessive sound levels, sensitive structures of the inner ear can be damaged. This can result in permanent noise-induced hearing loss (NIHL). These structures can be injured by exposure to a brief but intense sound, such as an explosion, or from regular exposure to excessive sound levels over time. Noise may cause hearing loss in three ways.

  • (a) Temporary threshold shift (TTS) refers to the short-term effect, i.e., a temporary reduction in the hearing ability of an individual that may follow to noise exposure. For example, if a person attend a concert or party function for 1–2 hours, in which DJ system was run at high decibel level, or an individual visit a factory in which various machines such as forge hammer and mechanical presses are running simultaneously and noise level is very high. This noise exposure will consequent in short-term hearing disability which is called temporary hearing threshold shift. The state of temporary threshold shift is usually recoverable, a person has hearing disability for some time, and then recovers the original hearing threshold level, and this is also known as auditory fatigue.

  • (b) Permanent threshold shift happens where the permissible limit of tolerance is exceeds in terms of; exposure time, noise level and individual vulnerability or susceptibility. The permanent hearing threshold shift (PTS) is result of chronic auditory fatigue, i.e., repeated temporary threshold shifts (TTS). It has been established by Chiu et al. (2007) that TTS driven by noise exposure is further enhanced by heat and work load. In this case recovery from threshold shift does not take place completely, rather will reduce and ultimately stop at some point of time, even after the end of the exposure.

  • 1 - Productivity and Work Study

  • Lakhwinder Pal Singh
  • Book:
    Work Study and Ergonomics
    Published online:
    17 August 2019
    Print publication:
    02 December 2015, pp 1-15

  • Summary

    Introduction

    A significant proportion of the Indian population is still struggling for its basic needs: food, shelter, clothes, security and health services. A nation can only raise the level of satisfaction with respect to these basic needs only if the return from resources is maximized or the productivity is improved. Then, the economy will grow and help provide a better quality of life. Productivity at an enterprise is assessed in terms of output of a production variable per unit of input. Fundamentally, it is used to measure the output of resources such as manpower, machinery, materials and money, in producing goods and services or commodities to produce income or profitability. There are ample examples of Japanese manufacturers increasing their productivity, after the Second World War when they faced the dilemma of vast shortage of material and human resources. The problem of Japanese manufacturers was entirely different from their Western counterparts. Later, in the mid-1940s, it was recognized by the president of Toyota Motor Company that American companies were outperforming them by a factor of ten. Therefore, in order to make a move towards rapid movement, Japanese leaders, such as Toyota, Shingo and Ohno devised a new process-oriented approach that is known as the ‘Toyota Production System or Lean Manufacturing’. The main objective of this approach is to reduce wastes, which in Japanese terms is called ‘Muda’ and maximizing the activities that add value to the good or services in the customer's perspective. The term value can be attributed to anything in a product or service for which the customer is willing and ready to pay. The value addition in goods and services will increase the overall profitability of system, company or whole supply chain. According to the lean philosophy, at an organizational level or throughout the supply chain there are three types of activities:

  • Non-necessary and non-value adding activities

  • Necessary but non-value adding activities

  • Necessary value adding activities

    • The first type of activities that constitutes majority (about 60 per cent) of all the activities, includes internal handling of material at the shop floor or packing and unpacking of semi-finished components and materials. The second category of activities is necessary but does not add value to the goods and services. These contribute about 35 per cent of the total supply chain activities; therefore labelled necessary, non-value adding activities.

  • 14 - Observational constraints

  • from IV - Expansion models
  • William D. Heacox, University of Hawaii, Hilo
  • Book:
    The Expanding Universe
    Published online:
    28 May 2018
    Print publication:
    26 November 2015, pp 164-174

  • Summary

    Solutions to the Friedmann Equations constitute a four-parameter family of expansion functions a (t); it is the cosmologists’ job to determine which of them is correct, or at least plausible. One way to do so is to measure the Universe's mass/energy densities so as to determine the inputs to the Friedmann Equations, but this approach is inherently inaccurate due to difficulties in determining such densities observationally (Chapter 12) and to the possibility of forms of energy density that leave no direct trace (e.g., dark energy). The alternative is to infer such densities from evidence left by expansion in the form of spatial and kinematic structures in the observable Universe. Most of these hinge upon observational estimates of distances to galaxies.

    Primary expansion diagnostics

    Distance estimates on cosmological scales are sufficiently difficult as to have generated a small industry among cosmologists over the past several decades. The overall outline of such methods is hierarchical: distances on one scale are calibrated with those on a previous, smaller scale. Thus:

  • • a fundamental distance is the Astronomical Unit (AU), conveniently measured by bouncing radar beams off the surface of the Sun;

  • • distances to relatively nearby stars are then measured in terms of trigonometric parallaxes based on the AU (shifts in apparent star position as the Earth revolves about the Sun);

  • • distances to other, more distant stars are estimated from stellar properties (e.g., spectral class luminosities) calibrated from nearby stellar parallaxes.

    • All this is sufficient to determine distances within local portions of our Galaxy. To extend this procedure to cosmological distances we require standards that can be seen at such distances and that have either luminosities or other characteristics of known values. Bright objects of known or presumed luminosities are particularly helpful in that they can be used to infer luminosity distances via Equations (9.63) or (9.66); such creatures are known prosaically as ‘standard candles’. Historically, the most useful standard candles have been Cepheid variable stars, whose luminosity can be inferred from their readily observable pulsation periods.

Page 1450 of 1933