A new chaotic genetic hybrid algorithm(CGHA) based on float point coding was put forward in this paper.Firstly,it used chaos optimization to search coarsely and produced a better initial population.Then,a power functi...A new chaotic genetic hybrid algorithm(CGHA) based on float point coding was put forward in this paper.Firstly,it used chaos optimization to search coarsely and produced a better initial population.Then,a power function carrier was adopted to improve the ergodicity and the sufficiency of the chaos optimization.Secondly,the genetic algorithm(GA) was used to search finely and guaranteed the population's evolution.To avoid the search being trapped in local minimum,a chaos degenerate mutation operator was designed to make the search converge to a global optimum quickly.Finally,CGHA was used to solve a typical mechanical optimization problem of shear stress checking for a cylinder helix spring.Compared with traditional penalty function method,chaos-Powell hybrid algorithm and standard GA,CGHA shows better performance in solution precision and convergence speed than those of the algorithms.Therefore,CGHA is a new effective way to solve the problems in mechanical optimization design.展开更多
BACKGROUND: Mental disorders are often a cause of long-term sickness absence (LTSA). Kessler 6 (K6) and the Brief Job Stress Questionnaire (BJSQ) are short mental health assessment questionnaires and widely used for a...BACKGROUND: Mental disorders are often a cause of long-term sickness absence (LTSA). Kessler 6 (K6) and the Brief Job Stress Questionnaire (BJSQ) are short mental health assessment questionnaires and widely used for assessing mental health in the workplace. OBJECTIVE: The purpose of this study is to evaluate the screening performance of these tools for the prediction of LTSA due to mental disorders (LTSA-MD). METHODS: K6 and BJSQ were administered to 19,321 public servants, of whom 131 took LTSA-MD during the study period. A receiver operating characteristic curve was drawn to estimate the area under the curve (AUC), sensitivity, and specificity with optimal cut-off points for K6 and four BJSQ subscales (Job Stressors;Stress Responses;Social Support;and Job Stressors + Social Support). RESULTS: K6 showed the highest AUC, and K6 and the Stress Responses subscale of the BJSQ showed higher AUC and sensitivity than other BJSQ subscales. CONCLUSIONS: The psychological distress experienced at the time, i.e. K6 and the Stress Responses, was the best predictors of LTSA-MD. Using these instant effective tools will enable us to identify high-risk workers, employ suitable interventions to improve mental health at an early stage, and reduce the incidence of LTSA-MD.展开更多
This paper introduces a type of out-of-plane microelectrothermal actuator, which is based on the principle of bimetal film thermal expansion in the fuse. A polymer SU-8 material and nickel are used as the functional a...This paper introduces a type of out-of-plane microelectrothermal actuator, which is based on the principle of bimetal film thermal expansion in the fuse. A polymer SU-8 material and nickel are used as the functional and structural materials of the actuator. Through heating the resistance wire using electricity, the actuator produces out-of-plane motion in the perpendicular axial direction of the device and the bias layer contact with the substrate, completing signal output. Using Coventorware software to establish the three-dimensional model, the geometric structure is optimized and the electrothermal capabilities are determined theoretically. From electrothermal ana- lysis, the actuator＇s displacement is 18 #m and the temperature rises from 300 to 440 K under a voltage of 5 V and the response time is 5 ms. The actuator＇s displacement is 20μm under a 100000 m/s2 acceleration in the accelerating field. In the coupled field, applying a 3 V voltage, the initial temperature is 300 K, while the acceleration is 50000 m/s2, the driving displacement of the actuator is 23μm, and temperature rises to 400 K. Finally, through checking the stress in different field sources, the maximum stress of the actuator is smaller than the allowable stress of nickel. The results show that the electrothermal actuator has high reliability.展开更多
基金Sponsored by the National Natural Science Foundation of China (50875186)the Research and Development Projects of Tianjin University of Technology and Education (KJ2008028,KJ2008043)
文摘A new chaotic genetic hybrid algorithm(CGHA) based on float point coding was put forward in this paper.Firstly,it used chaos optimization to search coarsely and produced a better initial population.Then,a power function carrier was adopted to improve the ergodicity and the sufficiency of the chaos optimization.Secondly,the genetic algorithm(GA) was used to search finely and guaranteed the population's evolution.To avoid the search being trapped in local minimum,a chaos degenerate mutation operator was designed to make the search converge to a global optimum quickly.Finally,CGHA was used to solve a typical mechanical optimization problem of shear stress checking for a cylinder helix spring.Compared with traditional penalty function method,chaos-Powell hybrid algorithm and standard GA,CGHA shows better performance in solution precision and convergence speed than those of the algorithms.Therefore,CGHA is a new effective way to solve the problems in mechanical optimization design.
文摘BACKGROUND: Mental disorders are often a cause of long-term sickness absence (LTSA). Kessler 6 (K6) and the Brief Job Stress Questionnaire (BJSQ) are short mental health assessment questionnaires and widely used for assessing mental health in the workplace. OBJECTIVE: The purpose of this study is to evaluate the screening performance of these tools for the prediction of LTSA due to mental disorders (LTSA-MD). METHODS: K6 and BJSQ were administered to 19,321 public servants, of whom 131 took LTSA-MD during the study period. A receiver operating characteristic curve was drawn to estimate the area under the curve (AUC), sensitivity, and specificity with optimal cut-off points for K6 and four BJSQ subscales (Job Stressors;Stress Responses;Social Support;and Job Stressors + Social Support). RESULTS: K6 showed the highest AUC, and K6 and the Stress Responses subscale of the BJSQ showed higher AUC and sensitivity than other BJSQ subscales. CONCLUSIONS: The psychological distress experienced at the time, i.e. K6 and the Stress Responses, was the best predictors of LTSA-MD. Using these instant effective tools will enable us to identify high-risk workers, employ suitable interventions to improve mental health at an early stage, and reduce the incidence of LTSA-MD.
文摘This paper introduces a type of out-of-plane microelectrothermal actuator, which is based on the principle of bimetal film thermal expansion in the fuse. A polymer SU-8 material and nickel are used as the functional and structural materials of the actuator. Through heating the resistance wire using electricity, the actuator produces out-of-plane motion in the perpendicular axial direction of the device and the bias layer contact with the substrate, completing signal output. Using Coventorware software to establish the three-dimensional model, the geometric structure is optimized and the electrothermal capabilities are determined theoretically. From electrothermal ana- lysis, the actuator＇s displacement is 18 #m and the temperature rises from 300 to 440 K under a voltage of 5 V and the response time is 5 ms. The actuator＇s displacement is 20μm under a 100000 m/s2 acceleration in the accelerating field. In the coupled field, applying a 3 V voltage, the initial temperature is 300 K, while the acceleration is 50000 m/s2, the driving displacement of the actuator is 23μm, and temperature rises to 400 K. Finally, through checking the stress in different field sources, the maximum stress of the actuator is smaller than the allowable stress of nickel. The results show that the electrothermal actuator has high reliability.
