We compare simulated galaxy distributions in the cold ΛCDM and warm ΛWDM dark matter models. The ΛWDM model adds one parameter to the ΛCDM model, namely the cut-off wavenumber kfs of linear den...We compare simulated galaxy distributions in the cold ΛCDM and warm ΛWDM dark matter models. The ΛWDM model adds one parameter to the ΛCDM model, namely the cut-off wavenumber kfs of linear density perturbations. The challenge is to measure kfs. This study focuses on “smoothing lengths” π/kfs in the range from 12 Mpc to 1 Mpc. The simulations reveal two distinct galaxy populations at any given redshift z: hierarchical galaxies that form bottom up starting at the transition mas?Mfs, and stripped down galaxies that lose mass to neighboring galaxies during their formation, are near larger galaxies, often have filamentary distributions, and seldom fill voids. We compare simulations with observations, and present four independent measurements of kfs, and the mass mh of dark matter particles, based on the redshift of first galaxies, galaxy mass distributions, and rotation curves of spiral galaxies.展开更多
Rock sampling with traditional coring method would cause initial damage to rock samples induced by in-situ stress relief during coring.To solve this problem,a damage-free coring method is proposed in this paper.The pr...Rock sampling with traditional coring method would cause initial damage to rock samples induced by in-situ stress relief during coring.To solve this problem,a damage-free coring method is proposed in this paper.The proposed coring scheme is numerically modeled first,and then it is verified by comparative laboratory tests using rock samples both obtained by conventional coring method and the proposed damage-free coring method.The result indicates that the in-situ stresses in sampling area could be reduced by 30%-50% through drilling a certain number of destressing holes around the whole sampling area.The spacing between adjacent destressing holes is about 10 cm.The average uniaxial compressive strength（UCS） of rock samples obtained by the damage-free coring method in Jinping II hydropower station with overburden depth of 1 900 m is higher than that of samples obtained by the conventional coring method with the same depth by 5%-15% and an average of 8%.In addition,the effectiveness of damage-free coring method can also be verified by acoustic emission（AE） monitoring.The AE events monitored during uniaxial compression test of damage-free coring samples is fewer than that of conventional coring samples at the primarily loading phase.展开更多
The Reynolds effect and mass-damping effect on the peak amplitude of a freely vibrating cylinder is studied by using forced oscillating data from Gopalkrishnan＇ s research in 1993, in which all experimental cases wer...The Reynolds effect and mass-damping effect on the peak amplitude of a freely vibrating cylinder is studied by using forced oscillating data from Gopalkrishnan＇ s research in 1993, in which all experimental cases were carried out at a fixed Reynolds and the tested cylinder was recognized as a body that had no mass and damping. However, the Reynolds and roass-damping are the very important parameters for the peak amplitude of a freely vibrating cylinder. In the present study, a function F is introduced to connect the forced oscillation and free vibration. Firstly the peak amplitude AG^＊ can be obtained from the function F using forced oscillation data of Gopalkrishnan＇ s experimental at Re = 10^4, and then the Reynolds effect is taken into account in the function f（Re）, while the mass-damping effect is considered in the function K（ α ）, where a is the mass-damping ratio. So the peak amplitude of a freely vibrating cylinder can be predicted by the expression： A ^＊ = K（ α ）f（ Re ）AG^＊ . It is found that the peak transverse amplitudes predicted by the above equation agree very well with many recent experimental data under both high and low Reynolds conditions while roass-damping varies. Furthermore, it is seen that the Reynolds number does have a great effect on the peak amplitude of a freely vibrating cylinder. The present idea in this paper can be applied as an update in the empirical models that also use forced oscillation data to predict the vortex induced vibration （VIV） response of a long riser in the frequency domain.展开更多
In order to assess the effects of tuned mass dampers （TMDs） on wind actions, an aeroelastic model with a scale of 1：60 was constructed. Tests were performed in an atmospheric boundary layer wind tunnel to investiga...In order to assess the effects of tuned mass dampers （TMDs） on wind actions, an aeroelastic model with a scale of 1：60 was constructed. Tests were performed in an atmospheric boundary layer wind tunnel to investigate the buffeting response of the pylon with a TMD fixed by a wire rope instead of a spring. The model was tested under different levels of damping. The experimental and numerical results showed that with the TMD in the optimal condition, the buffeting response was reduced by 47%.展开更多
The structures in engineering can be simplified into elastic beams with concentrated masses and elastic spring supports. Studying the law of vibration of the beams can be a help in guiding its design and avoiding reso...The structures in engineering can be simplified into elastic beams with concentrated masses and elastic spring supports. Studying the law of vibration of the beams can be a help in guiding its design and avoiding resonance. Based on the Laplace transform method, the mode shape functions and the frequency equations of the beams in the typical boundary conditions are derived. A cantilever beam with a lumped mass and a spring is selected to obtain its natural frequencies and mode shape functions. An experiment was conducted in order to get the modal parameters of the beam based on the NExT-ERA method. By comparing the analytical and experimental results, the effects of the locations of the mass and spring on the modal parameter are discussed. The variation of the natural frequencies was obtained with the changing stiffness coefficient and mass coefficient, respectively. The findings provide a reference for the vibration analysis methods and the lumped parameters layout design of elastic beams used in engineering.展开更多
目的:探究江苏省部分地区不同性别成年人脂肪质量随年龄增长的变化情况以及不同年龄段人群体质量指数(body fat index,BMI)和脂肪质量之间的关系。方法:收集2019年9月至2021年2月江苏省南京市、淮安市以及无锡市的体检人群数据,对符合...目的:探究江苏省部分地区不同性别成年人脂肪质量随年龄增长的变化情况以及不同年龄段人群体质量指数(body fat index,BMI)和脂肪质量之间的关系。方法:收集2019年9月至2021年2月江苏省南京市、淮安市以及无锡市的体检人群数据,对符合纳入标准人群进行体格检查和体成分检测,并分析其脂肪质量随年龄变化情况。结果:共收集2115名志愿者的基本信息,排除信息不全者46名,共纳入2069名进行研究分析。30岁以上成年人去脂体质量(fat free mass,FFM)随着年龄的增长呈现下降的趋势;30岁以上成年人的体脂肪量(body fat mass,BFM)、体脂百分比(percentage of body fat,PBF)、腰臀比(waist-hip ratio,WHR)和体脂指数(fat mass index,FMI)随着年龄的增长均呈现上升趋势,BFM、PBF和去脂体质量百分比(percentage of fat free mass,PFFM)在40岁出现显著上升,FFM和去脂体质量指数(fat free mass index,FFMI)在60岁开始出现显著下降。男性FMI在40岁出现显著上升,女性FMI从60岁出现显著上升。全年龄段成年人FFM随着BMI和腰围水平的升高呈上升趋势。结论:随着年龄的增长男性和女性的BFM、PBF和WHR均呈现上升趋势。各年龄段成年男性FFM显著高于女性,女性BFM、FMI、PBF和内脏脂肪面积显著高于男性。全年龄段成年人FFM随着BMI和WHR升高呈上升趋势。展开更多
文摘We compare simulated galaxy distributions in the cold ΛCDM and warm ΛWDM dark matter models. The ΛWDM model adds one parameter to the ΛCDM model, namely the cut-off wavenumber kfs of linear density perturbations. The challenge is to measure kfs. This study focuses on “smoothing lengths” π/kfs in the range from 12 Mpc to 1 Mpc. The simulations reveal two distinct galaxy populations at any given redshift z: hierarchical galaxies that form bottom up starting at the transition mas?Mfs, and stripped down galaxies that lose mass to neighboring galaxies during their formation, are near larger galaxies, often have filamentary distributions, and seldom fill voids. We compare simulations with observations, and present four independent measurements of kfs, and the mass mh of dark matter particles, based on the redshift of first galaxies, galaxy mass distributions, and rotation curves of spiral galaxies.
基金Supported by the National Basic Research Program of China (973 Program) (2010CB732003)the National Natural Science Foundation of China (51009013,50909077)
文摘Rock sampling with traditional coring method would cause initial damage to rock samples induced by in-situ stress relief during coring.To solve this problem,a damage-free coring method is proposed in this paper.The proposed coring scheme is numerically modeled first,and then it is verified by comparative laboratory tests using rock samples both obtained by conventional coring method and the proposed damage-free coring method.The result indicates that the in-situ stresses in sampling area could be reduced by 30%-50% through drilling a certain number of destressing holes around the whole sampling area.The spacing between adjacent destressing holes is about 10 cm.The average uniaxial compressive strength（UCS） of rock samples obtained by the damage-free coring method in Jinping II hydropower station with overburden depth of 1 900 m is higher than that of samples obtained by the conventional coring method with the same depth by 5%-15% and an average of 8%.In addition,the effectiveness of damage-free coring method can also be verified by acoustic emission（AE） monitoring.The AE events monitored during uniaxial compression test of damage-free coring samples is fewer than that of conventional coring samples at the primarily loading phase.
基金This project was financially supported by the National Natural Science Foundation of China (Grant No.50323004)a Grant fromthe Science &Technology Commission of Shanghai Municipality (No.05DJ14001)
文摘The Reynolds effect and mass-damping effect on the peak amplitude of a freely vibrating cylinder is studied by using forced oscillating data from Gopalkrishnan＇ s research in 1993, in which all experimental cases were carried out at a fixed Reynolds and the tested cylinder was recognized as a body that had no mass and damping. However, the Reynolds and roass-damping are the very important parameters for the peak amplitude of a freely vibrating cylinder. In the present study, a function F is introduced to connect the forced oscillation and free vibration. Firstly the peak amplitude AG^＊ can be obtained from the function F using forced oscillation data of Gopalkrishnan＇ s experimental at Re = 10^4, and then the Reynolds effect is taken into account in the function f（Re）, while the mass-damping effect is considered in the function K（ α ）, where a is the mass-damping ratio. So the peak amplitude of a freely vibrating cylinder can be predicted by the expression： A ^＊ = K（ α ）f（ Re ）AG^＊ . It is found that the peak transverse amplitudes predicted by the above equation agree very well with many recent experimental data under both high and low Reynolds conditions while roass-damping varies. Furthermore, it is seen that the Reynolds number does have a great effect on the peak amplitude of a freely vibrating cylinder. The present idea in this paper can be applied as an update in the empirical models that also use forced oscillation data to predict the vortex induced vibration （VIV） response of a long riser in the frequency domain.
基金The National Natural Science Foundation of China (Nos. 50808148 and 90815016)
文摘In order to assess the effects of tuned mass dampers （TMDs） on wind actions, an aeroelastic model with a scale of 1：60 was constructed. Tests were performed in an atmospheric boundary layer wind tunnel to investigate the buffeting response of the pylon with a TMD fixed by a wire rope instead of a spring. The model was tested under different levels of damping. The experimental and numerical results showed that with the TMD in the optimal condition, the buffeting response was reduced by 47%.
基金Supported by the National Natural Science Foundation of China(51109034)
文摘The structures in engineering can be simplified into elastic beams with concentrated masses and elastic spring supports. Studying the law of vibration of the beams can be a help in guiding its design and avoiding resonance. Based on the Laplace transform method, the mode shape functions and the frequency equations of the beams in the typical boundary conditions are derived. A cantilever beam with a lumped mass and a spring is selected to obtain its natural frequencies and mode shape functions. An experiment was conducted in order to get the modal parameters of the beam based on the NExT-ERA method. By comparing the analytical and experimental results, the effects of the locations of the mass and spring on the modal parameter are discussed. The variation of the natural frequencies was obtained with the changing stiffness coefficient and mass coefficient, respectively. The findings provide a reference for the vibration analysis methods and the lumped parameters layout design of elastic beams used in engineering.
文摘目的:探究江苏省部分地区不同性别成年人脂肪质量随年龄增长的变化情况以及不同年龄段人群体质量指数(body fat index,BMI)和脂肪质量之间的关系。方法:收集2019年9月至2021年2月江苏省南京市、淮安市以及无锡市的体检人群数据,对符合纳入标准人群进行体格检查和体成分检测,并分析其脂肪质量随年龄变化情况。结果:共收集2115名志愿者的基本信息,排除信息不全者46名,共纳入2069名进行研究分析。30岁以上成年人去脂体质量(fat free mass,FFM)随着年龄的增长呈现下降的趋势;30岁以上成年人的体脂肪量(body fat mass,BFM)、体脂百分比(percentage of body fat,PBF)、腰臀比(waist-hip ratio,WHR)和体脂指数(fat mass index,FMI)随着年龄的增长均呈现上升趋势,BFM、PBF和去脂体质量百分比(percentage of fat free mass,PFFM)在40岁出现显著上升,FFM和去脂体质量指数(fat free mass index,FFMI)在60岁开始出现显著下降。男性FMI在40岁出现显著上升,女性FMI从60岁出现显著上升。全年龄段成年人FFM随着BMI和腰围水平的升高呈上升趋势。结论:随着年龄的增长男性和女性的BFM、PBF和WHR均呈现上升趋势。各年龄段成年男性FFM显著高于女性,女性BFM、FMI、PBF和内脏脂肪面积显著高于男性。全年龄段成年人FFM随着BMI和WHR升高呈上升趋势。
