Mine accidents and injuries are complex and generally characterized by several factors starting from personal to technical, and technical to social characteristics.In this study, an attempt has been made to identify t...Mine accidents and injuries are complex and generally characterized by several factors starting from personal to technical, and technical to social characteristics.In this study, an attempt has been made to identify the various factors responsible for work related injuries in mines and to estimate the risk of work injury to mine workers.The prediction of work injury in mines was done by a step-by-step multivariate logistic regression modeling with an application to case study mines in India.In total, 18 variables were considered in this study.Most of the variables are not directly quantifiable.Instruments were developed to quantify them through a questionnaire type survey.Underground mine workers were randomly selected for the survey.Responses from 300 participants were used for the analysis.Four variables, age, negative affectivity, job dissatisfaction, and physical hazards, bear significant discriminating power for risk of injury to the workers, comparing between cases and controls in a multivariate situation while controlling all the personal and socio-technical variables.The analysis reveals that negatively affected workers are 2.54 times more prone to injuries than the less negatively affected workers and this factor is a more important risk factor for the case-study mines.Long term planning through identification of the negative individuals, proper counseling regarding the adverse effects of negative behaviors and special training is urgently required.Care should be taken for the aged and experienced workers in terms of their job responsibility and training requirements.Management should provide a friendly atmosphere during work to increase the confidence of the injury prone miners.展开更多
[Objective] The aim was to study the changes of zymography in 6 kinds of isozymes after long-term subculture of Emmenopterys henryi Oliv.. [Method] Non-denaturing polyacrylamide gel electrophoresis was used to analyze...[Objective] The aim was to study the changes of zymography in 6 kinds of isozymes after long-term subculture of Emmenopterys henryi Oliv.. [Method] Non-denaturing polyacrylamide gel electrophoresis was used to analyze isozyme patterns such as esterase (EST),acid phosphatase (ACP),ATP enzyme (ATPase),amylase (AMY),superoxide dismutase (SOD) and peroxidase (POD) in long-term subculture callus of Emmenopterys henryi Oliv. [Result] The research showed that there were differences among the 6 kinds of isozymes in embryogenic callus and non-embryogenic callus of Emmenopterys henryi Oliv.,and both levels could be taken as the basis for identification,the EST,ACP,and POD of non-embryogenic callus were significantly higher than embryogenic callus. The browning of non-embryogenic callus was non-level in the AMY,SOD and POD isozymes when was compared with normal non-embryogenic callus,while the EST,ACP and ATPase isozymes decreased; When the browning of embryogenic callus was contrasted with normal embryogenic callus,EST isozyme increased and the other 5 kinds of enzymes decreased. [Conclusion] The study provided theoretical basis for research morphological difference and browning of long-term tissue culture of Emmenopterys henryi Oliv..展开更多
A series of AZ80 billets were compressed with 60%height reduction on hot process simulator at 250,300,350,400℃ under strain rates of 0.01,0.1,1 and 10 s- 1.In order to predict the occurrence of surface fracture,the v...A series of AZ80 billets were compressed with 60%height reduction on hot process simulator at 250,300,350,400℃ under strain rates of 0.01,0.1,1 and 10 s- 1.In order to predict the occurrence of surface fracture,the values of the Cockcroft-Latham equation were calculated by the corresponding finite element numerical algorithm developed.A concept about damage incremental ratio in plastic deformation was defined as the ratio of damage increment at one step to the accumulated value.A method of finding the intersection of incremental ratio varying curve and simulation step axis was brought forward to make the fracture step certain. Then,the effects of temperature and strain rate on critical damage value were achieved.The results show that the critical damage value is not a constant but changes in a range of 0.021 8-0.378 0.It decreases significantly with the increase of strain rate at a certain temperature.While under a certain strain rate,the critical damage value has little change with the increase of temperature.展开更多
The dynamic interaction between maglev vehicle and three-span continuous guideway is discussed. With the consideration of control system, the dynamic interaction model has been developed. Numerical simulation has been...The dynamic interaction between maglev vehicle and three-span continuous guideway is discussed. With the consideration of control system, the dynamic interaction model has been developed. Numerical simulation has been performed to study dynamic characteristics of the guideway. The results show that bending rigidity, vehicle speed, span ratio and primary frequency all have important influences on the dynamic characteristics of the guideway and there is no distinct trend towards resonance vibration when fl/（v/l） equals 1.0. The definite way is to control impact coefficient and acceleration of the guideway. The conclusions can serve the design of high-speed maglev three-span continuous guideway.展开更多
A theoretical model of relationship between subsurface damage and surface roughness was established to realize rapid and non-destructive measurement of subsurface damage of ground optical materials.Postulated conditio...A theoretical model of relationship between subsurface damage and surface roughness was established to realize rapid and non-destructive measurement of subsurface damage of ground optical materials.Postulated condition of the model was that subsurface damage depth and peak-to-valley surface roughness are equal to depth of radial and lateral cracks in brittle surface induced by small-radius(radius≤200 μm)spherical indenter,respectively.And contribution of elastic stress field to the radial cracks propagation was also considered in the loading cycle.Subsurface damage depth of ground BK7 glasses was measured by magnetorheological finishing spot technique to validate theoretical ratio of subsurface damage to surface roughness.The results show that the ratio is directly proportional to load of abrasive grains and hardness of optical materials,while inversely proportional to granularity of abrasive grains and fracture toughness of optical materials.Moreover,the influence of the load and fracture toughness on the ratio is more significant than the granularity and hardness,respectively.The measured ratios of 80 grit and 120 grit fixed abrasive grinding of BK7 glasses are 5.8 and 5.4,respectively.展开更多
This paper presents a new algorithm to predict locations and severities of damage in structures by changing modal parameters. An existing algorithm of damage detection is reviewed and the new algorithm is formulated t...This paper presents a new algorithm to predict locations and severities of damage in structures by changing modal parameters. An existing algorithm of damage detection is reviewed and the new algorithm is formulated to improve the accuracy of damage locating and severity estimation by eliminating the erratic assumptions and limits in the existing algorithm. The damage prediction accuracy is numerically assessed for each algorithm when applied to a two-dimensional frame structure for which pre-damage and post-damage modal parameters are available for only a few modes of vibration. The analysis results illustrate the improved accuracy of the new algorithm when compared to the existing algorithm.展开更多
A new type of intelligent geosynthetic product,sensor-enabled geobelt(SEGB),is developed to improve the health monitoring of geotechnical structures.It can be used as a strain monitoring sensor owing to its unique pro...A new type of intelligent geosynthetic product,sensor-enabled geobelt(SEGB),is developed to improve the health monitoring of geotechnical structures.It can be used as a strain monitoring sensor owing to its unique property.As a conductive polymer,its electrical resistance regularly changes with its strain.Simultaneously,the SEGB is a geosynthetic product.This implies that it can be used as a reinforcement to strengthen a geotechnical structure.Therefore,to investigate its long-term mechanical properties within the temperature range of its service,a stress relaxation test is performed within the range of−20℃ to 40℃.The results show that the stress relaxation of the SEGB stabilizes at a certain stress level instead of decreasing to zero.Additionally,the process of its stress relaxation is accompanied by damage.Based on this phenomenon,a ternary physical constitutive model reflecting the constitutive relationship of the SEGB is established.Furthermore,a stress relaxation model involving damage evolution,temperature,and initial strain is established.It can be used to describe the stress relaxation process of SEGB at different service temperatures.展开更多
The friction characteristics of rock damage plane have important impact on the stability of block structure formed after the stratum is broken. The mechanics properties of rock damage plane are described by parameters...The friction characteristics of rock damage plane have important impact on the stability of block structure formed after the stratum is broken. The mechanics properties of rock damage plane are described by parameters such as roughness coefficient, wall compress strength and basic friction angle. These three coefficients for fine grain sandstone and medium granular sandstone and grit sandstone are test. The friction stress is researched at the condition of different normal compressive stress acting on the tension damage plane. The friction law of tension damage plane of sandstone abided by is summed up. This law will provide scientific basis for block structure stability judging in basic roof stratum and roof pressure intensity calculating.展开更多
Concrete dam construction, reservoir impoundment and operation are a complicated and long-term process. During the course of this process dam suffers lots of factors including changing temperature, humidity, deformati...Concrete dam construction, reservoir impoundment and operation are a complicated and long-term process. During the course of this process dam suffers lots of factors including changing temperature, humidity, deformation, loads and restraints around dam. With time going by, damage to darn concrete happens. As a result, the strength, stiffness and resistance of concrete will decrease accompanying with damage accumulation and dam structure performance behavior and lifetime will be shorten or even destructed. At present, most of researches focus on concrete material itself and seldom consider effects of water content for concrete structures. That is apparently inconsistent with the actual situation. In engineering practice, it is urgently needed to assess existing dam structure damage state considering dry zoning in concrete. Through taking C30 dam concrete as standard specimen, alternate freezing and thawing tests are undertaken and changing law of time-dependent concrete damage state resulting in alternate wetting and drying has been studied in this paper. And then calculation formulas of time-dependent concrete damage evolution process considering alternate wetting and drying under condition of freeze-thaw cycle tests are established. Combining with four parameters Hsieh-Ting-Chen （ H -T-C ） model, some relevant factors or parameters are obtained through indoor testing and life prediction model of concrete dam based on dry zoning and damage theory is put forward which provides technical supports for dam safety evaluation and management of sustainable development.展开更多
文摘Mine accidents and injuries are complex and generally characterized by several factors starting from personal to technical, and technical to social characteristics.In this study, an attempt has been made to identify the various factors responsible for work related injuries in mines and to estimate the risk of work injury to mine workers.The prediction of work injury in mines was done by a step-by-step multivariate logistic regression modeling with an application to case study mines in India.In total, 18 variables were considered in this study.Most of the variables are not directly quantifiable.Instruments were developed to quantify them through a questionnaire type survey.Underground mine workers were randomly selected for the survey.Responses from 300 participants were used for the analysis.Four variables, age, negative affectivity, job dissatisfaction, and physical hazards, bear significant discriminating power for risk of injury to the workers, comparing between cases and controls in a multivariate situation while controlling all the personal and socio-technical variables.The analysis reveals that negatively affected workers are 2.54 times more prone to injuries than the less negatively affected workers and this factor is a more important risk factor for the case-study mines.Long term planning through identification of the negative individuals, proper counseling regarding the adverse effects of negative behaviors and special training is urgently required.Care should be taken for the aged and experienced workers in terms of their job responsibility and training requirements.Management should provide a friendly atmosphere during work to increase the confidence of the injury prone miners.
基金Supported by the Project of Natural Reserve of the State Forestry Administration (460-8101)the 948 Project of the State Forest-ry Administration (2006-4-73)~~
文摘[Objective] The aim was to study the changes of zymography in 6 kinds of isozymes after long-term subculture of Emmenopterys henryi Oliv.. [Method] Non-denaturing polyacrylamide gel electrophoresis was used to analyze isozyme patterns such as esterase (EST),acid phosphatase (ACP),ATP enzyme (ATPase),amylase (AMY),superoxide dismutase (SOD) and peroxidase (POD) in long-term subculture callus of Emmenopterys henryi Oliv. [Result] The research showed that there were differences among the 6 kinds of isozymes in embryogenic callus and non-embryogenic callus of Emmenopterys henryi Oliv.,and both levels could be taken as the basis for identification,the EST,ACP,and POD of non-embryogenic callus were significantly higher than embryogenic callus. The browning of non-embryogenic callus was non-level in the AMY,SOD and POD isozymes when was compared with normal non-embryogenic callus,while the EST,ACP and ATPase isozymes decreased; When the browning of embryogenic callus was contrasted with normal embryogenic callus,EST isozyme increased and the other 5 kinds of enzymes decreased. [Conclusion] The study provided theoretical basis for research morphological difference and browning of long-term tissue culture of Emmenopterys henryi Oliv..
基金Projects(CSTC,cstc2009aa3012-1)supported by Science and Technology Committee of Chongqing,ChinaProject(20100470813)supported by China Postdoctoral Science FoundationProject(2010011511)supported by Sharing Fund of Chongqing University’s Large-scale Equipment
文摘A series of AZ80 billets were compressed with 60%height reduction on hot process simulator at 250,300,350,400℃ under strain rates of 0.01,0.1,1 and 10 s- 1.In order to predict the occurrence of surface fracture,the values of the Cockcroft-Latham equation were calculated by the corresponding finite element numerical algorithm developed.A concept about damage incremental ratio in plastic deformation was defined as the ratio of damage increment at one step to the accumulated value.A method of finding the intersection of incremental ratio varying curve and simulation step axis was brought forward to make the fracture step certain. Then,the effects of temperature and strain rate on critical damage value were achieved.The results show that the critical damage value is not a constant but changes in a range of 0.021 8-0.378 0.It decreases significantly with the increase of strain rate at a certain temperature.While under a certain strain rate,the critical damage value has little change with the increase of temperature.
基金Project (No. 2005AA505440) supported by the Hi-Tech Researchand Development Program (863) of China
文摘The dynamic interaction between maglev vehicle and three-span continuous guideway is discussed. With the consideration of control system, the dynamic interaction model has been developed. Numerical simulation has been performed to study dynamic characteristics of the guideway. The results show that bending rigidity, vehicle speed, span ratio and primary frequency all have important influences on the dynamic characteristics of the guideway and there is no distinct trend towards resonance vibration when fl/（v/l） equals 1.0. The definite way is to control impact coefficient and acceleration of the guideway. The conclusions can serve the design of high-speed maglev three-span continuous guideway.
基金Project(50375156) supported by the National Natural Science Foundation of China
文摘A theoretical model of relationship between subsurface damage and surface roughness was established to realize rapid and non-destructive measurement of subsurface damage of ground optical materials.Postulated condition of the model was that subsurface damage depth and peak-to-valley surface roughness are equal to depth of radial and lateral cracks in brittle surface induced by small-radius(radius≤200 μm)spherical indenter,respectively.And contribution of elastic stress field to the radial cracks propagation was also considered in the loading cycle.Subsurface damage depth of ground BK7 glasses was measured by magnetorheological finishing spot technique to validate theoretical ratio of subsurface damage to surface roughness.The results show that the ratio is directly proportional to load of abrasive grains and hardness of optical materials,while inversely proportional to granularity of abrasive grains and fracture toughness of optical materials.Moreover,the influence of the load and fracture toughness on the ratio is more significant than the granularity and hardness,respectively.The measured ratios of 80 grit and 120 grit fixed abrasive grinding of BK7 glasses are 5.8 and 5.4,respectively.
基金The project was financially supported by the National Natural Science Foundation of China （No. 50479027）.
文摘This paper presents a new algorithm to predict locations and severities of damage in structures by changing modal parameters. An existing algorithm of damage detection is reviewed and the new algorithm is formulated to improve the accuracy of damage locating and severity estimation by eliminating the erratic assumptions and limits in the existing algorithm. The damage prediction accuracy is numerically assessed for each algorithm when applied to a two-dimensional frame structure for which pre-damage and post-damage modal parameters are available for only a few modes of vibration. The analysis results illustrate the improved accuracy of the new algorithm when compared to the existing algorithm.
基金Project(2018YFB1600100)supported by the National Key Research and Development Project of ChinaProjects(51778346,52027813)supported by the National Natural Science Foundation of ChinaProject(2019GSF111007)supported by the Key Research and Development Project of Shandong Province,China。
文摘A new type of intelligent geosynthetic product,sensor-enabled geobelt(SEGB),is developed to improve the health monitoring of geotechnical structures.It can be used as a strain monitoring sensor owing to its unique property.As a conductive polymer,its electrical resistance regularly changes with its strain.Simultaneously,the SEGB is a geosynthetic product.This implies that it can be used as a reinforcement to strengthen a geotechnical structure.Therefore,to investigate its long-term mechanical properties within the temperature range of its service,a stress relaxation test is performed within the range of−20℃ to 40℃.The results show that the stress relaxation of the SEGB stabilizes at a certain stress level instead of decreasing to zero.Additionally,the process of its stress relaxation is accompanied by damage.Based on this phenomenon,a ternary physical constitutive model reflecting the constitutive relationship of the SEGB is established.Furthermore,a stress relaxation model involving damage evolution,temperature,and initial strain is established.It can be used to describe the stress relaxation process of SEGB at different service temperatures.
文摘The friction characteristics of rock damage plane have important impact on the stability of block structure formed after the stratum is broken. The mechanics properties of rock damage plane are described by parameters such as roughness coefficient, wall compress strength and basic friction angle. These three coefficients for fine grain sandstone and medium granular sandstone and grit sandstone are test. The friction stress is researched at the condition of different normal compressive stress acting on the tension damage plane. The friction law of tension damage plane of sandstone abided by is summed up. This law will provide scientific basis for block structure stability judging in basic roof stratum and roof pressure intensity calculating.
基金This research was supported by NSFC （National Natural Science Foundation of China） （Granted No.： 50909054, 50925933）.
文摘Concrete dam construction, reservoir impoundment and operation are a complicated and long-term process. During the course of this process dam suffers lots of factors including changing temperature, humidity, deformation, loads and restraints around dam. With time going by, damage to darn concrete happens. As a result, the strength, stiffness and resistance of concrete will decrease accompanying with damage accumulation and dam structure performance behavior and lifetime will be shorten or even destructed. At present, most of researches focus on concrete material itself and seldom consider effects of water content for concrete structures. That is apparently inconsistent with the actual situation. In engineering practice, it is urgently needed to assess existing dam structure damage state considering dry zoning in concrete. Through taking C30 dam concrete as standard specimen, alternate freezing and thawing tests are undertaken and changing law of time-dependent concrete damage state resulting in alternate wetting and drying has been studied in this paper. And then calculation formulas of time-dependent concrete damage evolution process considering alternate wetting and drying under condition of freeze-thaw cycle tests are established. Combining with four parameters Hsieh-Ting-Chen （ H -T-C ） model, some relevant factors or parameters are obtained through indoor testing and life prediction model of concrete dam based on dry zoning and damage theory is put forward which provides technical supports for dam safety evaluation and management of sustainable development.
