本文以竞技健美操常见 A 组动力性难度动作特点及身体伤害问题为研究对象。以江西省赣州市开展较好的厚德外国语学校的 60 名中学生健美操运动员作为调查对象,采用文献资料法、专家访谈法、个案问卷调查法、数理统计法,对中学生健美操...本文以竞技健美操常见 A 组动力性难度动作特点及身体伤害问题为研究对象。以江西省赣州市开展较好的厚德外国语学校的 60 名中学生健美操运动员作为调查对象,采用文献资料法、专家访谈法、个案问卷调查法、数理统计法,对中学生健美操训练常用的 A 组动力性难度动作进行筛选并对其动作特点进行深入的分析,再根据调查所得的中学生健美操运动员损伤部位、类型、时间、原因以及伤病的预防调查研究。展开更多
The purpose of increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft is presented. Aerodynamic characteristics, the surface pressure distribution and the max...The purpose of increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft is presented. Aerodynamic characteristics, the surface pressure distribution and the maximum lift are estimated for the baseline configuration for different Mach numbers and attack angles in subson- ic and supersonic potential flows, using a low-order three-dimensional panel method supported with the semi-empirical formulas of the data compendium （DATCOM）. Total nose-up and nose-down pitching moments about the center of gravity of the complete aircraft in the subsonic region depending on flight conditions and aircraft performance limitations are estimated. A software package is developed to implement the two-dimensional thrust vectoring flight control technique （pitch vectoring up and down） controlled by the advanced aerodynamic and control surface （the foreplane or the canard）. Results show that the canard with the thrust vectoring produces enough nose-down moment and can support the stabilizer at high maneuvers. The suggested surface can increase the aerodynamic efficiency （lift-to-drag ratio） of the baseline configuration by 5%-6% in subsonic and supersonic flight regimes.展开更多
The microstructure, hydrogen storage thermodynamics and kinetics of La5Mg95-xNix (x=5, 10, 15) ternary alloys with different Ni contents were investigated. The evolutions of the microstructure and phase of experimenta...The microstructure, hydrogen storage thermodynamics and kinetics of La5Mg95-xNix (x=5, 10, 15) ternary alloys with different Ni contents were investigated. The evolutions of the microstructure and phase of experimental alloys were characterized by X-ray diffractometry and scanning electron microscopy. The hydrogen storage kinetics and thermodynamics, and P-C-I curves were tested using a Sievert apparatus. It is found that increasing Ni content remarkably improves hydrogen storage kinetics but reduces the hydrogen storage capacity of alloys. The highest hydrogen absorption/desorption rate is observed in the La5Mg80Ni15 alloy, with the lowest hydrogen desorption activation value being 57.7 kJ/mol. By means of P-C-I curves and the van’t Hoff equation, it is determined that the thermodynamic performance of the alloy is initially improved and then degraded with increasing Ni content. The La5Mg85Ni10 alloy has the best thermodynamics properties with a hydrogenation enthalpy of -72.1 kJ/mol and hydrogenation entropy of -123.2 J/(mol·K).展开更多
The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophagea...The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophageal function is normally evaluated by means of manometry even though it reflects the squeeze force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe with combined axial force and manometry recordings showed that axial force amplitude increased by 130% in contrast to an increase of 30% using manometry. Using axial force in combination with manometry provides a more complete picture of esophageal motility, and the current paper outlines the advantages of using this method.展开更多
In this paper, we theoretically predict and experimentally measure the thrust efficiency of a biomimetic robotic fish, which is propelled by an ionic polymer-metal composite （IPMC） actuator. A physics-based model th...In this paper, we theoretically predict and experimentally measure the thrust efficiency of a biomimetic robotic fish, which is propelled by an ionic polymer-metal composite （IPMC） actuator. A physics-based model that consists of IPMC dynamics and hydrodynamics was proposed, and simulation was conducted. In order to test the thrust performance of the robotic fish, a novel experimental apparatus was developed for hydrodynamic experiments. Under a servo towing system, the IPMC fish swam at a self-propelled speed where external force is averagely zero. Experimental results demonstrated that the theoretical model can well predict the thrust efficiency of the robotic fish. A maximum thrust efficiency of 2.3x10-3 at 1 Hz was recorded experi- mentally, the maximum thrust force was 0.0253 N, recorded at 1.2 Hz, while the maximum speed was 0.021 m/s, recorded at 1.5 Hz, and a peak power of 0.36 W was recorded at 2.6 Hz. Additionally, the optimal actuation frequency for the thrust efficiency was also recorded at the maximum self-propelled speed. The present method of examining the thrust efficiency may also be applied to the studies of other types of smart material actuated underwater robots.展开更多
A new depth-integrated model deploying a non-hydrostatic pressure distribution is presented.With the pressure divided into hydrostatic and dynamic components,the horizontal momentum equations were obtained by integrat...A new depth-integrated model deploying a non-hydrostatic pressure distribution is presented.With the pressure divided into hydrostatic and dynamic components,the horizontal momentum equations were obtained by integrating the Navier-Stokes equations from the bottom to the free surface.The vertical momentum equation,in which the convective and viscosity terms were omitted,was approximated by the Keller-box scheme.The model has two steps.First,the dynamic pressure gradient terms were discretized semi-implicitly and the other terms were in explicit scheme.Second,the velocities expressed as the unknown dynamic pressure were substituted into the continuity equation,resulting in a five-diagonal symmetric matrix linear system that was solved by the conjugate gradient method.The model was validated with the propagation of a solitary wave and sinusoidal wave,indicating that it can predict free surface flows well.展开更多
文摘本文以竞技健美操常见 A 组动力性难度动作特点及身体伤害问题为研究对象。以江西省赣州市开展较好的厚德外国语学校的 60 名中学生健美操运动员作为调查对象,采用文献资料法、专家访谈法、个案问卷调查法、数理统计法,对中学生健美操训练常用的 A 组动力性难度动作进行筛选并对其动作特点进行深入的分析,再根据调查所得的中学生健美操运动员损伤部位、类型、时间、原因以及伤病的预防调查研究。
文摘The purpose of increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft is presented. Aerodynamic characteristics, the surface pressure distribution and the maximum lift are estimated for the baseline configuration for different Mach numbers and attack angles in subson- ic and supersonic potential flows, using a low-order three-dimensional panel method supported with the semi-empirical formulas of the data compendium （DATCOM）. Total nose-up and nose-down pitching moments about the center of gravity of the complete aircraft in the subsonic region depending on flight conditions and aircraft performance limitations are estimated. A software package is developed to implement the two-dimensional thrust vectoring flight control technique （pitch vectoring up and down） controlled by the advanced aerodynamic and control surface （the foreplane or the canard）. Results show that the canard with the thrust vectoring produces enough nose-down moment and can support the stabilizer at high maneuvers. The suggested surface can increase the aerodynamic efficiency （lift-to-drag ratio） of the baseline configuration by 5%-6% in subsonic and supersonic flight regimes.
基金Projects(51761032,51471054) supported by the National Natural Science Foundation of China
文摘The microstructure, hydrogen storage thermodynamics and kinetics of La5Mg95-xNix (x=5, 10, 15) ternary alloys with different Ni contents were investigated. The evolutions of the microstructure and phase of experimental alloys were characterized by X-ray diffractometry and scanning electron microscopy. The hydrogen storage kinetics and thermodynamics, and P-C-I curves were tested using a Sievert apparatus. It is found that increasing Ni content remarkably improves hydrogen storage kinetics but reduces the hydrogen storage capacity of alloys. The highest hydrogen absorption/desorption rate is observed in the La5Mg80Ni15 alloy, with the lowest hydrogen desorption activation value being 57.7 kJ/mol. By means of P-C-I curves and the van’t Hoff equation, it is determined that the thermodynamic performance of the alloy is initially improved and then degraded with increasing Ni content. The La5Mg85Ni10 alloy has the best thermodynamics properties with a hydrogenation enthalpy of -72.1 kJ/mol and hydrogenation entropy of -123.2 J/(mol·K).
基金Supported by Det Obelske Familiefond and Spar Nord Fonden
文摘The esophagus serves to transport food and fluid from the pharynx to the stomach. Manometry has been the "golden standard" for the diagnosis of esophageal motility diseases for many decades. Hence, esophageal function is normally evaluated by means of manometry even though it reflects the squeeze force (force in radial direction) whereas the bolus moves along the length of esophagus in a distal direction. Force measurements in the longitudinal (axial) direction provide a more direct measure of esophageal transport function. The technique used to record axial force has developed from external force transducers over in-vivo strain gauges of various sizes to electrical impedance based measurements. The amplitude and duration of the axial force has been shown to be as reliable as manometry. Normal, as well as abnormal, manometric recordings occur with normal bolus transit, which have been documented using imaging modalities such as radiography and scintigraphy. This inconsistency using manometry has also been documented by axial force recordings. This underlines the lack of information when diagnostics are based on manometry alone. Increasing the volume of a bag mounted on a probe with combined axial force and manometry recordings showed that axial force amplitude increased by 130% in contrast to an increase of 30% using manometry. Using axial force in combination with manometry provides a more complete picture of esophageal motility, and the current paper outlines the advantages of using this method.
基金supported by the National Natural Science Foundation of China (Grant No. 61075100)
文摘In this paper, we theoretically predict and experimentally measure the thrust efficiency of a biomimetic robotic fish, which is propelled by an ionic polymer-metal composite （IPMC） actuator. A physics-based model that consists of IPMC dynamics and hydrodynamics was proposed, and simulation was conducted. In order to test the thrust performance of the robotic fish, a novel experimental apparatus was developed for hydrodynamic experiments. Under a servo towing system, the IPMC fish swam at a self-propelled speed where external force is averagely zero. Experimental results demonstrated that the theoretical model can well predict the thrust efficiency of the robotic fish. A maximum thrust efficiency of 2.3x10-3 at 1 Hz was recorded experi- mentally, the maximum thrust force was 0.0253 N, recorded at 1.2 Hz, while the maximum speed was 0.021 m/s, recorded at 1.5 Hz, and a peak power of 0.36 W was recorded at 2.6 Hz. Additionally, the optimal actuation frequency for the thrust efficiency was also recorded at the maximum self-propelled speed. The present method of examining the thrust efficiency may also be applied to the studies of other types of smart material actuated underwater robots.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110142110064)the Ministry of Water Resources’ Science and Technology Promotion Plan Program of China (Grant No. TG1316)
文摘A new depth-integrated model deploying a non-hydrostatic pressure distribution is presented.With the pressure divided into hydrostatic and dynamic components,the horizontal momentum equations were obtained by integrating the Navier-Stokes equations from the bottom to the free surface.The vertical momentum equation,in which the convective and viscosity terms were omitted,was approximated by the Keller-box scheme.The model has two steps.First,the dynamic pressure gradient terms were discretized semi-implicitly and the other terms were in explicit scheme.Second,the velocities expressed as the unknown dynamic pressure were substituted into the continuity equation,resulting in a five-diagonal symmetric matrix linear system that was solved by the conjugate gradient method.The model was validated with the propagation of a solitary wave and sinusoidal wave,indicating that it can predict free surface flows well.
