ABSTRACT
Background The hearing of Chinese young adults is far less sensitive than 0 dB defined by international standards, with the threshold values mostly being at double digits, which is worthy of investigation. Objective To study the influencing factors of hearing threshold measurement. Methods The hearing measurements were conducted in two different ways, one was a standard method performed in a specialized audiometry experiment room, and the other one was an on-site audiometry test which included a daily examination of hearing and an onsite hearing test. From the workers who participated in the occupational health examination, 300 people were randomly selected as experimental subjects, and their hearing was measured in the hearing examination room of the Occupational Disease Prevention and Treatment Institute according to standard methods. A total of 9 766 workers from the General Motors factory were included in the daily group, and their hearing thresholds were measured in the hearing examination room in the factory. There were 4 617 people in the onsite group, and their hearing was measured in the test chamber of our mobile medical vehicle in their factories. The hearing threshold data of the three groups, i.e. experiment, daily examination and on-site, was compared and analyzed. In addition, the environmental noise in the hearing examination room and the mobile test chamber was measured. Results The hearing threshold value of the experimental group was the lowest. Despite this, its dB value remained at double digits at any frequency band. The hearing value of the daily group was in the middle. The onsite group had the highest hearing threshold, which was 58.2% higher than that of the experimental group. As the hearing data was not normally distributed, Kruskal-Wallis non-parametric test was conducted for statistical analysis. It was found that the hearing threshold difference among the three groups was statistically significant at all the frequency band (P< 0.01). The ambient noise level was 23.9-28.3 dB(A) in the hearing examination room, and 32.5 - 67.9 dB (A) in the mobile test chamber. Age and gender were not confounding factors to the results. Conclusion The hearing test method and its environmental noise were able to make the threshold measurements shift up significantly. The environmental noise of the mobile test chamber in the examination vehicle has exceeded the standard and needs to be improved.
ABSTRACT
Zr based alloys are widely used in hydrogen storage and purification systems. For hydrogen isotope capturing and recycling, it is possible to design the tritium extraction system of the glove box taking into account the operating conditions and technical constraints. Zr2Fe alloy bed was adopted in the 2.5%H2/Ar capturing experiments as well as numerical simulation was also constructed. In this work, the breakthrough curve under conditions of 300 °C@200 sccm for the carrier gas penetration was obtained by establishing a single flowing bed. Then a new numerical model of the bed was established for simulating the penetration process, and a numerical solution to the mass conservation equation of carrier gas passing through the bed was obtained concerning the actual experimental parameters. Calculation results have shown the two-dimensional distribution of H2 concentration flowing through a one-dimensional reactor. It can be seen clearly that the H2 concentration distributed along the bed axial at different time. This distribution profiles can be used to globally illuminate the concentration variation of hydrogen in the reactor within the whole reaction time scale. Comparing the experimental result of 1.27 days in the breakthrough curve, the results of numerical simulation can predict the curve of about 1.5 days began to breakthrough, although there were certain deviation (â¼18%). The results can provide a feasible numerical model support for optimizing the tritium capturing bed design.
