ABSTRACT
Highly precise and controllable liner implosions driven by a pulsed power facility have extensive applications in exploration of advanced hydrodynamics at the extremes of pressure and material velocity. In this paper, we describe a new pulsed power facility developed in China named FP-2 (a series of facilities for Fluid Physics investigations-the second generation) for liner implosions. Benefiting from the reliable and stable operation of 48 rail gap switches, the FP-2 facility can steadily transmit a current of 10.5 MA to a dummy load of 10 nH in the case of a charging voltage of ±40 kV. The first quarter cycle is 5.5 µs, and the percentage shot-to-shot deviation of the current history is less than 1%. When the aluminum liners of 60 mm in height and 0.6 mm in thickness are adopted, the maximum velocity of 4.5 and 7.5 km/s has been achieved with the liner diameter of 90 and 60 mm, respectively, at the diameter of 10 mm. Experimental results show that the percentage shot-to-shot deviation of the liner velocity history is less than 1%. As impact on the target, the maximum of the impact time deviation measured from four perpendicular fiber pins is less than 20 ns. Due to the modular design of FP-2, it is convenient for a future upgrade. The confirmation of high-quality implosion on FP-2, such as high repeatability, high reliability, and high symmetry, makes it a bright prospect to explore the advanced hydrodynamic problems at extremes of pressure and material velocity in the future.
ABSTRACT
OBJECTIVE: To investigate atmospheric mercury concentration in the workplace and urinary mercury concentration in workers exposed to mercury in a thermometer factory, and to determine the levels and influencing factors of urinary Β2-microglobulin (Β2-MG) and retinol-binding protein (RBP) in these workers. METHODS: An occupational health survey of the workplace was completed according to relevant national occupational health standards. Questionnaire survey and occupational health examination were conducted in 178 workers exposed to mercury in the factory. Statistical analysis was accomplished using SPSS 19.0. RESULTS: In the workplace, atmospheric mercury concentration was out of limits at seven of eight detection points expressed by short-term exposure limit; it was out of limits at all the eight detection points shown by time-weighted average. Statistically significant difference in atmospheric mercury concentration was found among different detection points (F = 138.714, P < 0.001). The geometric mean of urinary mercury concentration measured in 154 workers was 171.607 µg/g. There were 127 workers with urinary mercury concentration exceeding the standard (82.5% over-standard rate). Significant difference in urinary mercury concentration was shown in the workers among different positions (χ² = 44.531, P < 0.01). Urinary mercury concentration was positively correlated with atmospheric mercury concentration (r = 0.624, P < 0.01). The mean urinary Β2-MG level measured in 148 workers was 0.142 mg/L, and seven workers had urinary Β2-MG levels greater than 0.3 mg/L (4.7% abnormal rate). The mean urinary RBP level measured in 153 workers was 0.485 mg/L, and 19 workers had urinary RBP levels greater than 0.7 mg/L (12.4% abnormal rate). Ordinal logistic regression showed that age >34 years (OR = 4.88, 95%CI: 2.24â¼10.62) and length of service >15 years (OR = 2.50, 95%CI: 1.06-5.92) were risk factors for increased urinary Β2-MG level. Age >45 years (OR = 7.52, 95%CI: 2.50â¼22.65) was a risk factor for increased urinary RBP level. CONCLUSION: In the thermometer factory under study, atmospheric and urinary mercury concentrations both seriously exceeded the standards, which were harmful to the health of workers. High atmospheric mercury concentration, old age, and long length of service were risk factors for increased urinary Β2-MG and RBP levels in workers exposed to mercury.
