No description available.

The exposure to fumes and gases is one of the hazards associated with welding operations. Apart from research conducted on the mechanism of fume and gas formation and the relationship between fume formation rates and common welding parameters, little is known about the exposure process during welding. This research project aimed to identify the factors that influence exposure, develop an understanding of their role in the exposure process and through this understanding formulate strategies for the effective control of exposure during welding. To address these aims a literature review and an experimental program was conducted The literature review surveyed epidemiological, toxicological and exposure data. The experimental program involved three approaches, the first, an evaluation of the factors that influence exposure by assessing a metal inert gas/mild steel welding process in a workshop setting. The second approach involved the study of exposure in a controlled environment provided by a wind tunnel and simulated welding process. The final approach was to investigate workplace conditions through an assessment of exposure and control strategies in industry. The exposure to fumes and gases during welding is highly variable and frequently in excess of the health based exposure standards. Exposure is influenced by a number of a factors including the welding process, base material, arc time, electrode, arc current, arc voltage, arc length, electrode polarity, shield gas, wire-to-metal-work distance (metal inert gas), metal transfer mode, intensity of the UV radiation (ozone), the frequency of arc ignitions (ozone), thermal buoyancy generated by the arc process, ventilation (natural and mechanical), the welding environment, the position of the welder, the welders stance, helmet type, and helmet position. Exposure occurs as a result of three processes: the formation of contaminants at or around the arc region; their transport from the arc region, as influenced by the entry and thermal expansion of shield gases, the vigorous production of contaminants, thermal air currents produced by the heat of the arc process, and ventilation; and finally the entry of contaminants into the breathing zone of the welder, as influenced by the position of the welder, the welders stance, helmet type, and the helmet position. The control of exposure during welding can be achieved by several means: through the selection of welding parameters that generate low contaminant formation rates; through the limitation of arc time; and by isolating the breathing zone of the welder from the contaminant plume through the use of ventilation, welder position or the welding helmet as a physical barrier. Effective control is achieved by careful examination of the workplace, the selection of the most appropriate control option, and motivation of the workforce.

The market for Wireless Local Area Networks (WLANs) has experienced tremendous growth over the last few years and this trend is expected to continue in the future. This growth is due to the fact that wireless LANs provide several benefits including mobility, efficiency, and accuracy. In addition, the cost of installation for wireless LANs is several orders of magnitude lower than with traditional wired LANs due to reduced cabling costs. The two major components of a WLAN are Access Points (APs) and Radio Cards (RCs). Efforts have been made in the past to assess the performance of different APs and RCs from different vendors. However, these evaluations have been restricted to tests of interoperability and roaming. Tests to assess performance with respect to range, throughput, and power consumption are less common. Moreover, these tests are usually performed using homogeneous test beds (i.e., hardware components belong to the same vendor). The objective of this research was to assess how commercial-off-the-shelf (COTS) WLAN systems perform with respect to interoperability, roaming ability, power consumption, throughput, and range. In order to accomplish this, a test procedure composed of five experiments was developed. The evaluation was performed not only on homogeneous systems but also on systems constructed with hardware components from different vendors (i.e., heterogeneous). The results of the performance tests indicated that the different AP, RC, and their combinations, significantly affect the performance of the WLAN systems with respect to range, throughput, and power consumption. No significant differences were observed in the WLAN systems with respect to interoperability or roaming. The results of this research will help decision makers in understanding the key parameters that have to be considered when selecting WLAN equipment. In practice, however, it would be difficult for decision makers to determine which vendor of WLAN equipment has the best solution without actual testing. / Graduation date: 2003

Thesis (M. Phil.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 163-183).

No description available.

The purpose of this study was to investigate whether ice hockey facial protectors can decrease overall head acceleration during blunt impacts as well as to identify if attenuation differences exist between visors and cages. Commercial models of three cages and three visors were assessed. Blunt impacts were simulated permitting the measurement of peak accelerations (PA) within the surrogate head form. Results indicated that indeed face protectors in combination with helmets substantially reduced PA during blunt impacts within threshold safety limits (below 300 g's). In general, cages showed lower PA than visors (p=0.004). Differences between models were also observed during repeated impacts and impact site (p=0.0001, p=0.007). In conclusion, this study demonstrates that facial protectors function beyond their role in preventing facial injuries, complementing the role of the helmet in attenuating head deceleration during impact. Consequently, the utilization of facial protectors may reduce the severity and incidence of mTBI.

No description available.

No description available.

No description available.