To develop a method for the early diagnosis of health damage due to arc welding, we measured serum ferritin in 96 general employees and 320 arc welders in Company A. A positive correlation was observed between age and...To develop a method for the early diagnosis of health damage due to arc welding, we measured serum ferritin in 96 general employees and 320 arc welders in Company A. A positive correlation was observed between age and the serum ferritin level in the young group (age, 20 - 44 years) among the general employees. The mean serum ferritin level in the general employees was 119 ± 56 ng/ml. When the mean ± 2.5 SD was used as the standard value, ferritin levels > 260 ng / ml could be regarded as high. Based on this standard value, high ferritin levels were observed in 7 (6.6%) of 106 young arc welders in Company A but none of the general employees. Chest X-ray films showed minimal abnormality in one of 7 young arc welders who showed high ferritin levels. These results suggest that the determination of the serum ferritin level is useful for the early diagnosis of health damage due to arc welding.展开更多
Arc welding converter (AWC) power source is a nonlinear and discrete abnormal system. It is difficult to get the accurate analytic solution in theory. In this paper, an average state equation of the system is establi...Arc welding converter (AWC) power source is a nonlinear and discrete abnormal system. It is difficult to get the accurate analytic solution in theory. In this paper, an average state equation of the system is established by means of state space analysis method. The mathematics model of the reverse converter is gotten after the average equation of the system is linearized. The model is a two ranks oscillation link. With the parameters of the AWC, when the condition of (1/RC) 2 >>4/LC is available, the mathematics model may be simplified to a serial structure which includes a integral link and a one rank inertia link. On the basis of this, it can be analyzed and rectified in frequency domain, then some groups of reality rectification parameters are gotten around the theory rectification parameters. These groups of parameters are taken to do the resistance load experiment and welding technology experiment. The result of experiment accords with the theory analysis result. This paper also provides some practical analysis of the model under the large signal process such as the sudden opening of the load, short circuit, turning on and turning off the machine. The result of the research shows that the power source system of AWC can be analyzed and rectified by the frequency domain analysis method in the engineering. The deduced mathematics model of small signal average frequency domain shows the basic characteristics of the system, and the structure parameters of the system is formed by R, L, C and switching ratio D. The model is very simple and clear, and it can be used to analyze and design the power source system of AWC and it can also be used to direct the regulation for dynamic characteristics of the system.展开更多
Objective To investigate whether photochemical smog emitted during the process of electric arc welding might cause oxidative stress and potential oxidative damage in the bodies of welding operators. Methods Seventy...Objective To investigate whether photochemical smog emitted during the process of electric arc welding might cause oxidative stress and potential oxidative damage in the bodies of welding operators. Methods Seventy electric arc welding operators (WOs) and 70 healthy volunteers (HVs) were enrolled in a randomized controlled study design, in which the levels of vitamin C (VC) and vitamin E (VE) in plasma as well as the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and the level of lipoperoxide (LPO) in erythrocytes were determined by spectrophotometry. Results Compared with the average values of the above experimental parameters in the HVs group, the average values of VC and VE in plasma as well as those of SOD, CAT and GPX in erythrocytes in the WOs group were significantly decreased (P<0.005-0.0001), while the average value of LPO in erythrocytes in the WOs group was significantly increased (P<0.0001). The findings from the partial correlation analysis on the controlling of age suggested that with a prolonged duration of exposure to photochemical smog the values of VC, VE, SOD, and GPX, except for CAT, in the WOs were decreased gradually (P<0.05-0.005), the value of LPO in the WOs was increased gradually (P<0.001), and that with the ozone dose increased in the air in each worksite VC, VE, SOD, CAT and GPX decreased (P<0.005-0.001), but LPO increased (P<0.001). The findings from the reliability analysis for the VC, VE, SOD, CAT, GPX, and LPO values which were used to reflect oxidative stress and potential oxidative damage in the WOs showed that the reliability coefficients?alpha (6 items) was 0.8021, P<0.0001, and that the standardized item alpha was 0.9577, P<0.0001. Conclusion Findings in the present study suggest that there exists an oxidative stress induced by long-term exposure to photochemical smog in the bodies of WOs, thereby causing potential oxidative and lipoperoxidative damages in their bodies.展开更多
文摘To develop a method for the early diagnosis of health damage due to arc welding, we measured serum ferritin in 96 general employees and 320 arc welders in Company A. A positive correlation was observed between age and the serum ferritin level in the young group (age, 20 - 44 years) among the general employees. The mean serum ferritin level in the general employees was 119 ± 56 ng/ml. When the mean ± 2.5 SD was used as the standard value, ferritin levels > 260 ng / ml could be regarded as high. Based on this standard value, high ferritin levels were observed in 7 (6.6%) of 106 young arc welders in Company A but none of the general employees. Chest X-ray films showed minimal abnormality in one of 7 young arc welders who showed high ferritin levels. These results suggest that the determination of the serum ferritin level is useful for the early diagnosis of health damage due to arc welding.
文摘Arc welding converter (AWC) power source is a nonlinear and discrete abnormal system. It is difficult to get the accurate analytic solution in theory. In this paper, an average state equation of the system is established by means of state space analysis method. The mathematics model of the reverse converter is gotten after the average equation of the system is linearized. The model is a two ranks oscillation link. With the parameters of the AWC, when the condition of (1/RC) 2 >>4/LC is available, the mathematics model may be simplified to a serial structure which includes a integral link and a one rank inertia link. On the basis of this, it can be analyzed and rectified in frequency domain, then some groups of reality rectification parameters are gotten around the theory rectification parameters. These groups of parameters are taken to do the resistance load experiment and welding technology experiment. The result of experiment accords with the theory analysis result. This paper also provides some practical analysis of the model under the large signal process such as the sudden opening of the load, short circuit, turning on and turning off the machine. The result of the research shows that the power source system of AWC can be analyzed and rectified by the frequency domain analysis method in the engineering. The deduced mathematics model of small signal average frequency domain shows the basic characteristics of the system, and the structure parameters of the system is formed by R, L, C and switching ratio D. The model is very simple and clear, and it can be used to analyze and design the power source system of AWC and it can also be used to direct the regulation for dynamic characteristics of the system.
文摘Objective To investigate whether photochemical smog emitted during the process of electric arc welding might cause oxidative stress and potential oxidative damage in the bodies of welding operators. Methods Seventy electric arc welding operators (WOs) and 70 healthy volunteers (HVs) were enrolled in a randomized controlled study design, in which the levels of vitamin C (VC) and vitamin E (VE) in plasma as well as the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and the level of lipoperoxide (LPO) in erythrocytes were determined by spectrophotometry. Results Compared with the average values of the above experimental parameters in the HVs group, the average values of VC and VE in plasma as well as those of SOD, CAT and GPX in erythrocytes in the WOs group were significantly decreased (P<0.005-0.0001), while the average value of LPO in erythrocytes in the WOs group was significantly increased (P<0.0001). The findings from the partial correlation analysis on the controlling of age suggested that with a prolonged duration of exposure to photochemical smog the values of VC, VE, SOD, and GPX, except for CAT, in the WOs were decreased gradually (P<0.05-0.005), the value of LPO in the WOs was increased gradually (P<0.001), and that with the ozone dose increased in the air in each worksite VC, VE, SOD, CAT and GPX decreased (P<0.005-0.001), but LPO increased (P<0.001). The findings from the reliability analysis for the VC, VE, SOD, CAT, GPX, and LPO values which were used to reflect oxidative stress and potential oxidative damage in the WOs showed that the reliability coefficients?alpha (6 items) was 0.8021, P<0.0001, and that the standardized item alpha was 0.9577, P<0.0001. Conclusion Findings in the present study suggest that there exists an oxidative stress induced by long-term exposure to photochemical smog in the bodies of WOs, thereby causing potential oxidative and lipoperoxidative damages in their bodies.
