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Configuring a numeric keypad for a touch screen
20.3.24 (111426)
Martin, G.L. Configuring a numeric keypad for a touch screen. Ergonomics, 1988, 31.6, 945-953. This paper reports on a study comparing keying accuracy and speed for eight different numeric keypad configurations on a touch screen. Using touch-sensitive keypads displayed on a computer terminal, operators entered numbers presented to them through a speech synthesiser. Dependent measures collected were keying rates, errors, and the x- and y-dimension standard deviations from the centre point of the key. The primary finding was that keypads with square keys resulted in improved speed and a higher degree of accuracy than do keypads with regular keys (either a long horizontal dimension or a longer vertical dimension). Spread-out versions of the keypads (inter-key spacing = 1"3 cm) did not yield superior performance compared with compressed versions (inter-key spacing = 0"6 cm). 20.3.25 (111454)
Padmos, P., Van den Brink, T.D.J., Alferdinck, J.W.A.M., and Folles, E. Matrix signs for motorways: System design and optimum photometric features. Lighting Res and Teehnol, 1988, 20.2, 55 60. A system of computer-controlled variable message signs (matrix signs), which was implemented several years ago on many sections of Dutch freeways, is described. The signs can display lnessages like speed limits and 'change lane'. The main conclusions from an evaluation study are that the system reduces the number of accidents considerably, but has less influence on traffic flow. Field trials to determine optimum display features are described. These trials provided relations between the most relevant photometric quantities: horizon luminance, message luminance, pixel intensity and inter-pixel distance. Practical examples of the control of the sign's light output as a function of varying ambient light level are given. 20.3.26 t 111459)
Farrell, J.E., Casson, E.J., Haynie, C.R., and Benson, B.L. Designing flicker-free video display terminals. Displays Technol and .tpplications, 1988, 9.3, 115 122. The notion of a standard observer for flicker is described based on a theory of human flicker sensitivity. Based on this model and the data collected from the independent studies, an analytical method is proposed for predicting whether or not a particular display will be flicker-free given inform-
ation about its phosphor, refresh rate and screen luminance. This method will provide display engineers with a way to evaluate screen flicker during the design phase of a display and will be a satisfactory alternative to the present, rather cumbersome, empirical methods.
better result than those with a colour index of less than 85 Ra (77 Ra). Of those lamps with a colour index of 85 Ra, the best results are achieved with 'normal white' and 'cool white',
20.3.29 (111519 i
Fitzpatrick, D.T. An analysis of noise-induced hearing loss in army helicopter pilots. Aviation, Space & Enviroitl Med, 1988, 59.10, 937- 941.
Workplace and equipment design 20.3.27 (111471)
Haslegrave, C.M., and Gregg, H. Improving the ergonomics of production sewing machines. In: Advances in Manufacturing Technology III, B. Worthington (Fd), Kogan Page, London, 1988, pp 284-293. The layout of sewing workstations has a significant effect on both productivity and health of machinists. Upper limb strain injuries are recognised as a widespread problem in production sewing, but postural strain and fatigue also contribute to reduced efficiency among machinists. Several production sewing tasks have been studied and some of the more important factors in the machine layout have been identified as influencing the visual and postural demands of the tasks. Consideration of these can produce improvements to the design of existing workstations as well as defining guidelines for design of industrial sewing machines.
Hearing loss in the aviation environment has been attributed to a variety of factors ranging from aircraft noise exposure to the ageing process. Consequently, this study was conducted to determine the relative contribution of age, total flight hours, type of aircraft, and use of hearing protection to hearing loss in US army aviators. Information from a survey of the aviators in an aviation brigade was combined with audiometric records to create the data file. The final study group, 83% of the unit aviators, was evaluated for hearing loss using two criteria: (1) existing US army standards, and (2) four empirical categories of significant threshold shift. Data analysis suggests that hearing loss is primarily a function of noise exposure as measured by total flight hours. Age was found to be a less significant factor; aircraft type has no significant effect. The results indicate that combination hearing protection appears to lower the risk of hearing loss significantly.
Environment
20.3.30 (111533i
20.3.28 (111509)
Vincent, M.J., and Tipton, M.J.
Zegers, D., and Van den Berg, V.
The effects of cold immersion and hand protection on grip strength. Aviation, Space & Environ/Med, 1988, 59.8, 738 741.
The effect of lighting quality and intensity on the efficiency of seed potato inspection (Ergonomische Forschung der Beleuchtungseinflusse auf Selektionsarbeiten bei Pflanzkartoffeln). (In German.) Zeitschr~ft ,/ur A rbeitswissenschaft, 1988, 42.2, I06-112. To determine the influence of lighting on selection work, a standard sample of Bintje potatoes was chosen. The sample consisted of 5000 'good' and 200 'irregular' tubers (washed, size 28/35 ram). The portion designated 'irregular' was spread over an 'average' sample. The percentage of correctly identified irregular tubers was taken as a measure of the visual perceptual and mental stress assuming that this percentage is higher with a lower stress. The following deductions can be made from the results: ( 1) the three lighting levels of 500, 1000 and 2000 Lux have no significant effect on the selection results; (2) the choice of lamp type has a significant effect on the selection result. Fluorescent lamps with a colour index of 85 Ra give a significantly
The maximal voluntary grip strength (MVGS) of male volunteers was examined following a series of five intermittent 2-min cold water (5°C) immersions of the unprotected hand or forearm. MVGS changes due to wearing a protective glove were also investigated. The surface electrical activity over the hand flexor muscles was recorded, as was the skin temperature of the hand and forearm. MVGS decreased significantly (p < 0.01 ) following hand immersion (16~:~ ) and forearm immersion (13+S). The majority of these reductions occurred during the first 2-rain period of immersion. The effect of wearing a glove after unprotected hand cooling also produced significant (p -'/--0"01 ) MVGS reductions which averaged 14g. These reductions were in addition to those caused by hand cooling. It is concluded that both hand and forearm protection are important for the maintenance of hand-grip strength following cold water immersion.
Applied Ergonomics
September 1989
235
Martin, G.L. Configuring a numeric keypad for a touch screen. Ergonomics, 1988, 31.6, 945-953. This paper reports on a study comparing keying accuracy and speed for eight different numeric keypad configurations on a touch screen. Using touch-sensitive keypads displayed on a computer terminal, operators entered numbers presented to them through a speech synthesiser. Dependent measures collected were keying rates, errors, and the x- and y-dimension standard deviations from the centre point of the key. The primary finding was that keypads with square keys resulted in improved speed and a higher degree of accuracy than do keypads with regular keys (either a long horizontal dimension or a longer vertical dimension). Spread-out versions of the keypads (inter-key spacing = 1"3 cm) did not yield superior performance compared with compressed versions (inter-key spacing = 0"6 cm). 20.3.25 (111454)
Padmos, P., Van den Brink, T.D.J., Alferdinck, J.W.A.M., and Folles, E. Matrix signs for motorways: System design and optimum photometric features. Lighting Res and Teehnol, 1988, 20.2, 55 60. A system of computer-controlled variable message signs (matrix signs), which was implemented several years ago on many sections of Dutch freeways, is described. The signs can display lnessages like speed limits and 'change lane'. The main conclusions from an evaluation study are that the system reduces the number of accidents considerably, but has less influence on traffic flow. Field trials to determine optimum display features are described. These trials provided relations between the most relevant photometric quantities: horizon luminance, message luminance, pixel intensity and inter-pixel distance. Practical examples of the control of the sign's light output as a function of varying ambient light level are given. 20.3.26 t 111459)
Farrell, J.E., Casson, E.J., Haynie, C.R., and Benson, B.L. Designing flicker-free video display terminals. Displays Technol and .tpplications, 1988, 9.3, 115 122. The notion of a standard observer for flicker is described based on a theory of human flicker sensitivity. Based on this model and the data collected from the independent studies, an analytical method is proposed for predicting whether or not a particular display will be flicker-free given inform-
ation about its phosphor, refresh rate and screen luminance. This method will provide display engineers with a way to evaluate screen flicker during the design phase of a display and will be a satisfactory alternative to the present, rather cumbersome, empirical methods.
better result than those with a colour index of less than 85 Ra (77 Ra). Of those lamps with a colour index of 85 Ra, the best results are achieved with 'normal white' and 'cool white',
20.3.29 (111519 i
Fitzpatrick, D.T. An analysis of noise-induced hearing loss in army helicopter pilots. Aviation, Space & Enviroitl Med, 1988, 59.10, 937- 941.
Workplace and equipment design 20.3.27 (111471)
Haslegrave, C.M., and Gregg, H. Improving the ergonomics of production sewing machines. In: Advances in Manufacturing Technology III, B. Worthington (Fd), Kogan Page, London, 1988, pp 284-293. The layout of sewing workstations has a significant effect on both productivity and health of machinists. Upper limb strain injuries are recognised as a widespread problem in production sewing, but postural strain and fatigue also contribute to reduced efficiency among machinists. Several production sewing tasks have been studied and some of the more important factors in the machine layout have been identified as influencing the visual and postural demands of the tasks. Consideration of these can produce improvements to the design of existing workstations as well as defining guidelines for design of industrial sewing machines.
Hearing loss in the aviation environment has been attributed to a variety of factors ranging from aircraft noise exposure to the ageing process. Consequently, this study was conducted to determine the relative contribution of age, total flight hours, type of aircraft, and use of hearing protection to hearing loss in US army aviators. Information from a survey of the aviators in an aviation brigade was combined with audiometric records to create the data file. The final study group, 83% of the unit aviators, was evaluated for hearing loss using two criteria: (1) existing US army standards, and (2) four empirical categories of significant threshold shift. Data analysis suggests that hearing loss is primarily a function of noise exposure as measured by total flight hours. Age was found to be a less significant factor; aircraft type has no significant effect. The results indicate that combination hearing protection appears to lower the risk of hearing loss significantly.
Environment
20.3.30 (111533i
20.3.28 (111509)
Vincent, M.J., and Tipton, M.J.
Zegers, D., and Van den Berg, V.
The effects of cold immersion and hand protection on grip strength. Aviation, Space & Environ/Med, 1988, 59.8, 738 741.
The effect of lighting quality and intensity on the efficiency of seed potato inspection (Ergonomische Forschung der Beleuchtungseinflusse auf Selektionsarbeiten bei Pflanzkartoffeln). (In German.) Zeitschr~ft ,/ur A rbeitswissenschaft, 1988, 42.2, I06-112. To determine the influence of lighting on selection work, a standard sample of Bintje potatoes was chosen. The sample consisted of 5000 'good' and 200 'irregular' tubers (washed, size 28/35 ram). The portion designated 'irregular' was spread over an 'average' sample. The percentage of correctly identified irregular tubers was taken as a measure of the visual perceptual and mental stress assuming that this percentage is higher with a lower stress. The following deductions can be made from the results: ( 1) the three lighting levels of 500, 1000 and 2000 Lux have no significant effect on the selection results; (2) the choice of lamp type has a significant effect on the selection result. Fluorescent lamps with a colour index of 85 Ra give a significantly
The maximal voluntary grip strength (MVGS) of male volunteers was examined following a series of five intermittent 2-min cold water (5°C) immersions of the unprotected hand or forearm. MVGS changes due to wearing a protective glove were also investigated. The surface electrical activity over the hand flexor muscles was recorded, as was the skin temperature of the hand and forearm. MVGS decreased significantly (p < 0.01 ) following hand immersion (16~:~ ) and forearm immersion (13+S). The majority of these reductions occurred during the first 2-rain period of immersion. The effect of wearing a glove after unprotected hand cooling also produced significant (p -'/--0"01 ) MVGS reductions which averaged 14g. These reductions were in addition to those caused by hand cooling. It is concluded that both hand and forearm protection are important for the maintenance of hand-grip strength following cold water immersion.
Applied Ergonomics
September 1989
235