Ultra-fine grained TA5 titanium alloy was fabricated by friction stir processing(FSP).Temperature distribution and material flow were simulated by the coupled Euler−Lagrange(CEL)method.The microstructure and mechanica...Ultra-fine grained TA5 titanium alloy was fabricated by friction stir processing(FSP).Temperature distribution and material flow were simulated by the coupled Euler−Lagrange(CEL)method.The microstructure and mechanical properties of TA5 alloy were characterized by optical and scanning electron microscope,Vickers hardness,and tensile tests.The processed alloy was composed of ultra-fine grained and equiaxed grains due to dynamic recrystallization.The microstructure recrystallized through grain boundary rotation and dislocation accumulation.The grain size reached the minimum on the advancing side of the stir zone with the highest grain misorientation.Ultimate tensile strength was promoted to over 830 MPa after FSP at a rotating speed of 200 r/min,whereas elongation varied a little.The specimens all fractured on the retreating side of the stir zone and smaller dimples were depicted from the fracture morphologies of FSP specimens.展开更多
Background：Human immunodeficiency virus （HIV） is spreading rapidly among men who have sex with men （MSM） in China.Anonymous questionnaires or direct interviews have been frequently used to study their behavior.Th...Background：Human immunodeficiency virus （HIV） is spreading rapidly among men who have sex with men （MSM） in China.Anonymous questionnaires or direct interviews have been frequently used to study their behavior.The aim of the study was to describe the behavioral risk profile of the MSM in Beijing using the randomized response techniques （RRTs）.Methods：A cross-sectional survey of sexual behavior among a sample of MSM was conducted in two HIV counseling and testing clinics in Beijing.The survey was carried out with an anonymous questionnaire containing sensitive questions on sexual behavior.To obtain the honest responses to the sensitive questions,three distinctive RRTs were used in the questionnaire：（1） Additive randomized response model for quantitative questions,（2） randomized response model for multiple choice questions,and （3） Simmons randomized response model for binomial questions.Formulae for the point estimate,variance,and confidence interval （CI） were provided for each specific model.Results：Using RRTs in a sample of 659 participants,the mean age at first homosexual encounter was estimated to be 21.7 years （95% CI：21.2-22.2）,and each had sex with about three （2.9,95% CI：2.4-3.4） male partners on average in the past month.The estimated rate for consistent condom use was 56.4% （95% CI：50.1-62.8%）.In addition,condom was estimated to be used among 80.0% （95% CI：74.1-85.9%） of the population during last anal sex with a male partner.Conclusions：Our study employed RRTs in a survey containing questions on sexual behavior among MSM,and the results showed that RRT might be a useful tool to obtain truthful feedback on sensitive information such as sexual behavior from the respondents,especially in traditional Chinese cultural settings.展开更多
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(51974100).
文摘Ultra-fine grained TA5 titanium alloy was fabricated by friction stir processing(FSP).Temperature distribution and material flow were simulated by the coupled Euler−Lagrange(CEL)method.The microstructure and mechanical properties of TA5 alloy were characterized by optical and scanning electron microscope,Vickers hardness,and tensile tests.The processed alloy was composed of ultra-fine grained and equiaxed grains due to dynamic recrystallization.The microstructure recrystallized through grain boundary rotation and dislocation accumulation.The grain size reached the minimum on the advancing side of the stir zone with the highest grain misorientation.Ultimate tensile strength was promoted to over 830 MPa after FSP at a rotating speed of 200 r/min,whereas elongation varied a little.The specimens all fractured on the retreating side of the stir zone and smaller dimples were depicted from the fracture morphologies of FSP specimens.
基金the National Natural Science Foundation of China，the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions
文摘Background：Human immunodeficiency virus （HIV） is spreading rapidly among men who have sex with men （MSM） in China.Anonymous questionnaires or direct interviews have been frequently used to study their behavior.The aim of the study was to describe the behavioral risk profile of the MSM in Beijing using the randomized response techniques （RRTs）.Methods：A cross-sectional survey of sexual behavior among a sample of MSM was conducted in two HIV counseling and testing clinics in Beijing.The survey was carried out with an anonymous questionnaire containing sensitive questions on sexual behavior.To obtain the honest responses to the sensitive questions,three distinctive RRTs were used in the questionnaire：（1） Additive randomized response model for quantitative questions,（2） randomized response model for multiple choice questions,and （3） Simmons randomized response model for binomial questions.Formulae for the point estimate,variance,and confidence interval （CI） were provided for each specific model.Results：Using RRTs in a sample of 659 participants,the mean age at first homosexual encounter was estimated to be 21.7 years （95% CI：21.2-22.2）,and each had sex with about three （2.9,95% CI：2.4-3.4） male partners on average in the past month.The estimated rate for consistent condom use was 56.4% （95% CI：50.1-62.8%）.In addition,condom was estimated to be used among 80.0% （95% CI：74.1-85.9%） of the population during last anal sex with a male partner.Conclusions：Our study employed RRTs in a survey containing questions on sexual behavior among MSM,and the results showed that RRT might be a useful tool to obtain truthful feedback on sensitive information such as sexual behavior from the respondents,especially in traditional Chinese cultural settings.
