Numerical simulation of 3-D inner flow between Up-stream Pumping Mechanical Face Seals （UPMFS） faces was initially done by CFD software, which made the flow visualization come true. Simulation results directly disco...Numerical simulation of 3-D inner flow between Up-stream Pumping Mechanical Face Seals （UPMFS） faces was initially done by CFD software, which made the flow visualization come true. Simulation results directly discover the action of hydrodynamic lubrication, and by comparison with that of Conventional Mechanic Face Seals （CMFS）, the advantage over bigger bearing capability, less friction and much less leakage are explained clearly. Otherwise there are also some different ideas and results from precedent analysis and computational research results： dynamic and static pressure profiles can be obtained respectively instead of the analytic total pressure distribution only, pressure distribution is nonlinear, while always be solved as linear, lower pressure is observed at the area of inner diameter caused by the grooves, but its possible cavitations effects to the performance of UPMFS still need further study.展开更多
Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above b...Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above background concentrations with most (Ni, Cu, Fe, Cr and Cd) decreasing with soil depth. The distribution pattern were in the following order Fe > Cu > Zn > Pb > Cr > Ni > Cd. Across all the sampling locations and profiles, Fe and Cd showed the highest (476.4 μg·g-1) and least (37.5 μg·g-1) mean concentrations respectively. Pollution load index (PLI) and index of geoaccumulation (Igeo) revealed overall high and moderate contamination respectively but the enrichment factors (EFs) for Pb Ni and Cd are severe. The inter-element relationship revealed the identical source of elements in the soils of the studied area. The accuracy of the results has been cheeked using the standard reference material;SRM (PACS-2). The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.展开更多
Background: Automobile mechanics face different occupational hazards, which can have a wide range of physical and biological impacts depending on the frequency, intensity, and length of exposure. This study looked at ...Background: Automobile mechanics face different occupational hazards, which can have a wide range of physical and biological impacts depending on the frequency, intensity, and length of exposure. This study looked at the dangers and hazards that automobile mechanics in Kugbo Mechanic village in the Federal Capital Territory of Nigeria faced in their jobs. Research Objectives: The specific objectives were to determine the typical occupational risks faced by Kugbo automobile mechanics, evaluate the degree and risk of related health problems and injuries among Kugbo mechanics workers, examine the application of PPE and additional safety precautions among Kugbo mechanics, and assess Kugbo automobile workers’ understanding of the consequences of operating without PPE. Methods: A cross-sectional descriptive survey was conducted using purposeful sampling. A validated structured questionnaire was administered to 200 automobile workers at risk of exposure to hazards. The questionnaire covered socio-demographics, types of risk exposure, perceptions of their vulnerability, and the use of personal protective equipment. The data was analysed using descriptive and inferential statistics in Statistical Packages for Social version 26. Cross tabulation was used to identify patterns and associations between variables, and the Relative importance Index method was used to determine the relative importance of adherence to PPE and other safety issues. Results: Findings show that 5.1% of the respondents had completed secondary school, 25.3% had attended a technical school, 36.9% had completed primary school, and 32.8% had no formal education. Long exposure makes automobile workers more vulnerable to illnesses attributed to their job, as 91.9% work long hours sitting and 78.3% work long hours standing. The overall mean score of 3.72 shows that most respondents did not agree that automobile workers wear PPEs and follow other safety precautions. The medical issues listed include burns on the body, depression, heart illness, severe heada展开更多
The two kinds of rigid polyurethane （PU） foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in...The two kinds of rigid polyurethane （PU） foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight. The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams. The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples. The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently. Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples. The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.展开更多
This article reviews the status of thermomechanical analysis of the friction stir welding(FSW)process for establishing guidelines for further investigation,filling the available research gaps,and expanding FSW applica...This article reviews the status of thermomechanical analysis of the friction stir welding(FSW)process for establishing guidelines for further investigation,filling the available research gaps,and expanding FSW applications.Firstly,the advantages and applications of FSW process are introduced,and the significance and key issues for thermomechanical analysis in FSW are pointed out.Then,solid mechanic and fluid dynamic methods in modeling FSW process are described,and the key issues in modeling FSW are discussed.Di erent available mesh modeling techniques including the applications,benefits and shortcomings are explained.After that,at different subsections,the thermomechanical analysis in FSW of aluminum alloys and steels are examined and summarized in depth.Finally,the conclusions and summary are presented in order to investigate the lack of knowledge and the possibilities for future study of each method and each material.展开更多
The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribut...The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribution of Martian rocks mechanical property for the success of Mars exploration.In this paper,a fast and accurate probability distribution method for predicting the macroscale elastic modulus of Martian rocks was proposed by integrating the microscale rock mechanical experiments(micro-RME),accurate grain-based modeling(AGBM)and upscaling methods based on reliability principles.Firstly,the microstructure of NWA12564 Martian sample and elastic modulus of each mineral were obtained by micro-RME with TESCAN integrated mineral analyzer(TIMA)and nanoindentation.The best probability distribution function of the minerals was determined by Kolmogorov-Smirnov(K-S)test.Secondly,based on best distribution function of each mineral,the Monte Carlo simulations(MCS)and upscaling methods were implemented to obtain the probability distribution of upscaled elastic modulus.Thirdly,the correlation between the upscaled elastic modulus and macroscale elastic modulus obtained by AGBM was established.The accurate probability distribution of the macroscale elastic modulus was obtained by this correlation relationship.The proposed method can predict the probability distribution of Martian rocks mechanical property with any size and shape samples.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No:50475122).
文摘Numerical simulation of 3-D inner flow between Up-stream Pumping Mechanical Face Seals （UPMFS） faces was initially done by CFD software, which made the flow visualization come true. Simulation results directly discover the action of hydrodynamic lubrication, and by comparison with that of Conventional Mechanic Face Seals （CMFS）, the advantage over bigger bearing capability, less friction and much less leakage are explained clearly. Otherwise there are also some different ideas and results from precedent analysis and computational research results： dynamic and static pressure profiles can be obtained respectively instead of the analytic total pressure distribution only, pressure distribution is nonlinear, while always be solved as linear, lower pressure is observed at the area of inner diameter caused by the grooves, but its possible cavitations effects to the performance of UPMFS still need further study.
文摘Soil characterization and heavy metals in different layers (0 - 15 cm;15 - 30 cm and 30 - 45 cm depth) of automobile mechanic waste dumps were studied. The soils showed remarkably high levels of all the metals above background concentrations with most (Ni, Cu, Fe, Cr and Cd) decreasing with soil depth. The distribution pattern were in the following order Fe > Cu > Zn > Pb > Cr > Ni > Cd. Across all the sampling locations and profiles, Fe and Cd showed the highest (476.4 μg·g-1) and least (37.5 μg·g-1) mean concentrations respectively. Pollution load index (PLI) and index of geoaccumulation (Igeo) revealed overall high and moderate contamination respectively but the enrichment factors (EFs) for Pb Ni and Cd are severe. The inter-element relationship revealed the identical source of elements in the soils of the studied area. The accuracy of the results has been cheeked using the standard reference material;SRM (PACS-2). The mechanic waste dumps represent potential sources of heavy metal pollution to environment. The elevated levels of heavy metals in these soil profiles constitute a serious threat to both surface and groundwater.
文摘Background: Automobile mechanics face different occupational hazards, which can have a wide range of physical and biological impacts depending on the frequency, intensity, and length of exposure. This study looked at the dangers and hazards that automobile mechanics in Kugbo Mechanic village in the Federal Capital Territory of Nigeria faced in their jobs. Research Objectives: The specific objectives were to determine the typical occupational risks faced by Kugbo automobile mechanics, evaluate the degree and risk of related health problems and injuries among Kugbo mechanics workers, examine the application of PPE and additional safety precautions among Kugbo mechanics, and assess Kugbo automobile workers’ understanding of the consequences of operating without PPE. Methods: A cross-sectional descriptive survey was conducted using purposeful sampling. A validated structured questionnaire was administered to 200 automobile workers at risk of exposure to hazards. The questionnaire covered socio-demographics, types of risk exposure, perceptions of their vulnerability, and the use of personal protective equipment. The data was analysed using descriptive and inferential statistics in Statistical Packages for Social version 26. Cross tabulation was used to identify patterns and associations between variables, and the Relative importance Index method was used to determine the relative importance of adherence to PPE and other safety issues. Results: Findings show that 5.1% of the respondents had completed secondary school, 25.3% had attended a technical school, 36.9% had completed primary school, and 32.8% had no formal education. Long exposure makes automobile workers more vulnerable to illnesses attributed to their job, as 91.9% work long hours sitting and 78.3% work long hours standing. The overall mean score of 3.72 shows that most respondents did not agree that automobile workers wear PPEs and follow other safety precautions. The medical issues listed include burns on the body, depression, heart illness, severe heada
文摘The two kinds of rigid polyurethane （PU） foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight. The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams. The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples. The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently. Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples. The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.
基金Supported by National Natural Science Foundation of China(Grant Nos.51475272,51842507)Key R&D Program of Shandong Province in China(Grant No.2018GGX103001).
文摘This article reviews the status of thermomechanical analysis of the friction stir welding(FSW)process for establishing guidelines for further investigation,filling the available research gaps,and expanding FSW applications.Firstly,the advantages and applications of FSW process are introduced,and the significance and key issues for thermomechanical analysis in FSW are pointed out.Then,solid mechanic and fluid dynamic methods in modeling FSW process are described,and the key issues in modeling FSW are discussed.Di erent available mesh modeling techniques including the applications,benefits and shortcomings are explained.After that,at different subsections,the thermomechanical analysis in FSW of aluminum alloys and steels are examined and summarized in depth.Finally,the conclusions and summary are presented in order to investigate the lack of knowledge and the possibilities for future study of each method and each material.
文摘The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribution of Martian rocks mechanical property for the success of Mars exploration.In this paper,a fast and accurate probability distribution method for predicting the macroscale elastic modulus of Martian rocks was proposed by integrating the microscale rock mechanical experiments(micro-RME),accurate grain-based modeling(AGBM)and upscaling methods based on reliability principles.Firstly,the microstructure of NWA12564 Martian sample and elastic modulus of each mineral were obtained by micro-RME with TESCAN integrated mineral analyzer(TIMA)and nanoindentation.The best probability distribution function of the minerals was determined by Kolmogorov-Smirnov(K-S)test.Secondly,based on best distribution function of each mineral,the Monte Carlo simulations(MCS)and upscaling methods were implemented to obtain the probability distribution of upscaled elastic modulus.Thirdly,the correlation between the upscaled elastic modulus and macroscale elastic modulus obtained by AGBM was established.The accurate probability distribution of the macroscale elastic modulus was obtained by this correlation relationship.The proposed method can predict the probability distribution of Martian rocks mechanical property with any size and shape samples.
