Biomedical subjects

Alan H S Chan

Publications and source records attributed to Alan H S Chan.

7 recordsLinked to original sources

PubMed2006

Control and management of hospital indoor air quality.

BACKGROUND: The complex hospital environment requires special attention to ensure healthful indoor air quality (IAQ) to protect patients and healthcare workers against hospital-acquired (nosocomial) infections and occupational diseases. The aim here is to recommend effective guidelines for the control and management of hospital IAQ. MATERIAL/METHODS: The authors have done an extensive literature review and conducted comprehensive IAQ assessments in nine hospitals. It is noted that the IAQ measurements are not presented in this paper because of confidentiality. However, the IAQ analysis was studied carefully in the development of the recommendations given in this paper. RESULTS: The airborne chemical and microbiological contaminants of concern for hospitals have been identified and the major emission sources, monitoring methods, and exposure limits have been well documented and are reviewed here. Proper engineering system designs and operations are also reviewed, with recommendations for effective dilution and removal of the contaminants. The control and mitigation measures cover mechanical ventilation, filtration, differential pressure control, directional airflow control, local exhaust ventilation, and ultraviolet germicidal irradiation (UVGI) disinfection. Their applications in critical environments, such as operating theatres, isolation rooms, and other typical units, such as outpatient departments and laboratories, are also considered. CONCLUSIONS: Effective IAQ monitoring methods and mitigation measures suitable for the hospital environment have been identified. Accordingly, strategies for the implementation of a hospital indoor air quality management system are recommended. Healthcare workers, hospital engineers, and administrative staff can use the above as guidelines to manage and run their hospitals with healthful indoor air quality.

Air Microbiology↗

PubMed2005

Synchronous and asynchronous presentations of auditory and visual signals: Implications for control console design.

In this study, the effects of synchronous and asynchronous auditory and visual signal presentation on reaction times and response errors were examined to provide data for developing ergonomics recommendations for control console design. The results showed that synchronous presentation for combined visual and auditory stimulation facilitated responses, and shorter reaction times and higher response accuracies were obtained. When visual and auditory stimuli were presented synchronously but in opposing (left and right) positions, a visual dominance phenomenon was found, such that the subjects responded more often (81%) with faster responses to the visual signal. This visual dominance effect occurred even in the asynchronous condition when the auditory stimulus was presented 200 ms earlier than the visual one. It was also found that response speed and accuracy improved with increasing length of the warning time interval, and when an uncrossed hand posture was used for making responses. The above results were translated into practical ergonomic recommendations for response key layout, warning time interval, and ways of presenting visual and auditory signals to improve control console design.

Acoustic Stimulation↗

PubMed2005

Occupational exposure to volatile organic compounds and mitigation by push-pull local exhaust ventilation in printing plants.

The extensive use of multiple organic solvents in offset lithographic printing causing high emissions of volatile organic compounds (VOCs) indeed poses a serious risk to printing workers' health. In this study, indoor air quality (IAQ) assessments were carried out in seven printing plants and the main objectives were to understand the effect of VOC emissions on IAQ and develop effective mitigation measures to protect workers. The thorough gas chromatography/mass spectrometry (GC/MS) measurements showed that although a variety of VOCs were presented in the indoor air, none of them was found close to individual 8-h time-weighted average (TWA) of the occupational exposure limit (OEL). The additive effect was also found below the critical value of unity. However, short-term personal exposure to total volatile organic compounds (TVOCs) was exceedingly high when a print worker carried out blanket and ink roller cleaning procedures. Therefore, the occupational health risk was mainly due to repeated short-term exposures during intermittent VOC-emitting procedures rather than long-term exposure to background VOCs. Push-pull local exhaust ventilation (LEV) was identified as an effective mitigation measure. Computational fluid dynamics (CFD) analysis was conducted to study the push-pull LEV operation. It was found that there existed a threshold LEV air flow rate for an abrupt reduction in the worker's exposure to VOCs. The reduction was less sensitive when the LEV airflow was further increased beyond the threshold. These phenomena, consistent with experimental results reported by other investigators, were explained by detailed CFD analysis showing the competition between the general ventilation and the push-pull LEV to become the dominating driving force for the resultant local flow pattern.

Air Pollutants, Occupational↗

PubMed2005

Quantifying visual field shape for improving accuracy of search performance prediction.

The current study calculated a set of 16 shape indices of six subjects (4 men and 2 women, 21-28 years old) for easy and precise quantification of visual lobe shapes using Visual Lobe Measurement System (VILOMS) software. The indices can be used in mathematical models of visual search for better understanding of search behaviour and higher accuracy of search performance prediction. General patterns in the shape indices showed that visual lobes of the subjects were slightly irregular, with low sphericity, a moderately rough boundary, horizontally elongated and slightly asymmetric along both axes. Given the complex relationships among visual lobe area, lobe shape, and search strategy, it seems that a more detailed analysis than hitherto attempted will be necessary. Quantifying lobe shape with the 16 shape indexes is a useful step to performing such analysis.

Adult↗

PubMed2004

Comparative research on response stereotypes for daily operation tasks of Chinese and American engineering students.

A group of Mainland Chinese engineering students were asked to respond to 12 questions by indicating their design conventions and expectations about operations, directions-of-motion, and descriptions of movement for items such as doors, keys, taps, and knobs. Chi-square tests demonstrated strong response stereotypes for tasks of all 12 questions. A comparison of the stereotype strengths found here with that of Hong Kong Chinese and American engineering students reported earlier indicated that stereotype strengths of engineering students from the three regions were generally different. For some cases stereotype characteristics of two regions were more alike than the other, and also for some subjects in the three regions performed similarly. The Mainland and Hong Kong Chinese were more alike in making their choices on questions of conceptual compatibility, while more consistent preferences on movement compatibility and spatial compatibility were noted between the Mainland Chinese and American students than Hong Kong Chinese.

Adolescent↗

PubMed2003

Movement compatibility for rotary control and circular display--Computer Simulated Test and real Hardware Test.

This experiment studied strength and reversibility of direction-of-motion stereotypes and response times for different configurations of circular displays and rotary knobs. The effect of pointer position, instruction of turn direction, and control plane on movement compatibility was analyzed with precise quantitative measures of strength and reversibility index of stereotype. A comparison of results was made between a Computer Simulated Test and a Hardware Test with real rotary controls. There was consensus in the results of the two tests that strong and significantly reversible clockwise-for-clockwise (CC) and anticlockwise-for-anticlockwise (AA) stereotypes were obtained at the 12 o'clock position. Subjects' response times were found to be generally longer when there were no clear movement stereotypes. Nevertheless, differences of results were observed that while the CC and AA preferences were found to be dominant and reversible at all the planes and pointer positions in the Hardware Test, there was variation in the strength and reversibility of the two stereotypes amongst different testing configurations in the Simulated Test. This phenomenon was explained by the operating of the clockwise-for-right and anticlockwise-for-left principles, as shown in the analysis of contributions of component principles to the overall stereotype. The differences of results from the two tests were discussed with regard to simulation fidelity and it was suggested that a real Hardware Test should be used whenever possible for determination of design parameters of control panels in consideration of movement compatibility. Based on the Hardware Test, a pointer is recommended to be positioned at 12 o'clock position for check reading or resetting purpose, and the frontal plane is the best plane for positioning a rotary control with circular display. The results of this study provided significant implications for the industrial design of control panels used in man-machine interfaces for improved human performance.

Adult↗

PubMed2002

Visual performance on detection tasks with double-targets of the same and different difficulty.

This paper reports a study of measurement of horizontal visual sensitivity limits for 16 subjects in single-target and double-targets detection tasks. Two phases of tests were conducted in the double-targets task; targets of the same difficulty were tested in phase one while targets of different difficulty were tested in phase two. The range of sensitivity for the double-targets test was found to be smaller than that for single-target in both the same and different target difficulty cases. The presence of another target was found to affect performance to a marked degree. Interference effect of the difficult target on detection of the easy one was greater than that of the easy one on the detection of the difficult one. Performance decrement was noted when correct percentage detection was plotted against eccentricity of target in both the single-target and double-targets tests. Nevertheless, the non-significant correlation found between the performance for the two tasks demonstrated that it was impossible to predict quantitatively ability for detection of double targets from the data for single targets. This indicated probable problems in generalizing data for single target visual lobes to those for multiple targets. Also lobe area values obtained from measurements using a single-target task cannot be applied in a mathematical model for situations with multiple occurrences of targets.

Attention↗