Modulated high frequency （HF） heating of the ionosphere provides a feasible means of artificially generating ex- tremely low frequency （ELF）/very low frequency （VLF） whistler waves, which can leak into the inner...Modulated high frequency （HF） heating of the ionosphere provides a feasible means of artificially generating ex- tremely low frequency （ELF）/very low frequency （VLF） whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency arti- ficially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ~ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval （△f） of the discrete, multi-frequency waves. We find that there is a threshold value of Af for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to △f （proportional to the frequency components Nw） when △f is below the threshold value but it remains unchanged with increasing Af when △f is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the ＇effective frequency band＇. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better performance of controlled precipitation of high energy electrons in the plasmasphere by artificial ELF/VLF whistler waves can be achieved.展开更多
The behavior of a chemical tanker(CT)in extreme waves was discussed in detail,that is,in terms of rigid body heave and pitch motions,vertical bending moments(VBMs)amidships,green water,and slamming impacts through the...The behavior of a chemical tanker(CT)in extreme waves was discussed in detail,that is,in terms of rigid body heave and pitch motions,vertical bending moments(VBMs)amidships,green water,and slamming impacts through the analysis of the experimental data from model tests.Regular wave tests conducted for two wave steepness showed that the increase in wave steepness caused the increase in the asymmetry between hogging and sagging moments and the contribution of green water on deck to the decrease in vertical wave bending moments.Random uncertainty analysis of statistical values in irregular wave tests with various seeds revealed slight experimental uncertainties on motions and VBMs and slightly higher errors in slamming pressure peaks.With the increase in forward speed,experimental uncertainty on slamming pressures at the bow increased.Breather solutions of the nonlinear Schrödinger equation applied to generate tailored extreme waves of certain critical wavelengths showed a good performance in terms of ship response,and it was further verified for the CT.展开更多
The speed of a ship sailing in waves always slows down due to the decrease in efficiency of the propeller. So it is necessary and essential to analyze the unsteady hydrodynamic performance of propeller in waves. This ...The speed of a ship sailing in waves always slows down due to the decrease in efficiency of the propeller. So it is necessary and essential to analyze the unsteady hydrodynamic performance of propeller in waves. This paper is based on the numerical simulation and experimental research of hydrodynamics performance when the propeller is under wave conditions. Open-water propeller performance in calm water is calculated by commercial codes and the results are compared to experimental values to evaluate the accuracy of the numerical simulation method. The first-order Volume of Fluid(VOF) wave method in STAR CCM+ is utilized to simulate the three-dimensional numerical wave. According to the above prerequisite, the numerical calculation of hydrodynamic performance of the propeller under wave conditions is conducted, and the results reveal that both thrust and torque of the propeller under wave conditions reveal intense unsteady behavior. With the periodic variation of waves, ventilation, and even an effluent phenomenon appears on the propeller. Calculation results indicate, when ventilation or effluent appears, the numerical calculation model can capture the dynamic characteristics of the propeller accurately, thus providing a significant theory foundation forfurther studying the hydrodynamic performance of a propeller in waves.展开更多
After the erection of the Three Gorges Dam, the water level of Yangtze River will reach 175 m, and the average wave crest will be up to 1 m. Therefore the wave action cannot be neglected for the slope stability. Throu...After the erection of the Three Gorges Dam, the water level of Yangtze River will reach 175 m, and the average wave crest will be up to 1 m. Therefore the wave action cannot be neglected for the slope stability. Through simulation tests, the wave-induced dynamic response of the slope is analyzed. The soil body is taken as linear elastic body when it has a small deformation under the small wave action. Based on tests, the excess pore pressure and slope displacement under the loading in different wave period are analyzed. The ratio of dynamic strength and static strength to the breaking process of the slope is discussed. It is demonstrated that smaller wave period gives rise to a larger strain of the slope under the same stress. At different depth of water, different weakness effect on the stability of the soil slope is observed and the slope has an adaptability to the wave action to some extent.展开更多
A moored array of circular cylinders undergoes slow oscillations in the horizontal plane,i.e.surge,sway and yaw,due to the non linear excitation of ocean waves.To evaluate wave drift damping,the slow oscillation is ap...A moored array of circular cylinders undergoes slow oscillations in the horizontal plane,i.e.surge,sway and yaw,due to the non linear excitation of ocean waves.To evaluate wave drift damping,the slow oscillation is approximated by quasi steady motions or equivalently,a uniform flow is superposed to the wave field.In the case of yawing motion,a uniform rotation about the yawing axis is enforced to the entire fluid domain.The velocity potential is expanded into perturbation series based on two small parameters that measure wave slope and velocity of steady flow.Wave drift forces (moment) are calculated by the far field method.Experiment arrangements are also discussed.Measured data are compared to the calculated results to verify the present theory.展开更多
This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves....This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.展开更多
U-wave changes during treadmill exercise test were compared between 34 patientswith CAD and 33 normal controls.All of them were confirmed by coronary angiographv.Tenpatients with CAD and 1 normal subject in this study...U-wave changes during treadmill exercise test were compared between 34 patientswith CAD and 33 normal controls.All of them were confirmed by coronary angiographv.Tenpatients with CAD and 1 normal subject in this study showed U-wave inversion during exercisetest.Of the 10 patients,4 had significant stenosis in one-vessel and 6 in multi-vessel of the ma-jor coronary arteries.The sensitivity,specificity and predictive value of exercise-inducedU-wave inversion were 29％, 97％ and 91％,respectively.It is proposed that exercise inducedU-wave inversion is a reliable predictive index of CAD.展开更多
近年来,随着摩尔定律逐渐放缓,晶上系统(System on wafer, SoW)技术作为最热门的“超越摩尔”技术路线之一,已经成为先进封装领域的研究热点。基于晶上系统技术,将传统的毫米波收发前端阵列组件进行三维重构集成,可实现全新的轻薄化毫...近年来,随着摩尔定律逐渐放缓,晶上系统(System on wafer, SoW)技术作为最热门的“超越摩尔”技术路线之一,已经成为先进封装领域的研究热点。基于晶上系统技术,将传统的毫米波收发前端阵列组件进行三维重构集成,可实现全新的轻薄化毫米波晶上阵列,具有“三免”(免连接器、免电缆、免管壳封装)的颠覆性结构。本文针对毫米波晶上阵列的自动化测试需求,创新性提出一种毫米波双面晶圆测试方法,突破了多尺寸双面晶圆可靠固定、双面探针精确对准和自动切换以及扎针强度精确控制和实时调节等关键技术,在此基础上研制出毫米波双面晶圆自动测试平台,解决了毫米波收发前端晶上阵列三维测试的难点,对毫米波晶上系统的测试具有重大参考价值。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41204120 and 41304130)the Fundamental Research Funds for the Central Universities(Grant No.2042014kf0251)
文摘Modulated high frequency （HF） heating of the ionosphere provides a feasible means of artificially generating ex- tremely low frequency （ELF）/very low frequency （VLF） whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency arti- ficially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ~ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval （△f） of the discrete, multi-frequency waves. We find that there is a threshold value of Af for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to △f （proportional to the frequency components Nw） when △f is below the threshold value but it remains unchanged with increasing Af when △f is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the ＇effective frequency band＇. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better performance of controlled precipitation of high energy electrons in the plasmasphere by artificial ELF/VLF whistler waves can be achieved.
文摘The behavior of a chemical tanker(CT)in extreme waves was discussed in detail,that is,in terms of rigid body heave and pitch motions,vertical bending moments(VBMs)amidships,green water,and slamming impacts through the analysis of the experimental data from model tests.Regular wave tests conducted for two wave steepness showed that the increase in wave steepness caused the increase in the asymmetry between hogging and sagging moments and the contribution of green water on deck to the decrease in vertical wave bending moments.Random uncertainty analysis of statistical values in irregular wave tests with various seeds revealed slight experimental uncertainties on motions and VBMs and slightly higher errors in slamming pressure peaks.With the increase in forward speed,experimental uncertainty on slamming pressures at the bow increased.Breather solutions of the nonlinear Schrödinger equation applied to generate tailored extreme waves of certain critical wavelengths showed a good performance in terms of ship response,and it was further verified for the CT.
基金Supported by the National Natural Science Foundation of China （51379043, 41176074, 51209048, 51409063）, High Tech Ship Research Project of Ministry of Industry and Technology （G014613002）, and the Support Plan for Youth Backbone Teachers of Harbin Engineering University （HEUCFQ 1408）
文摘The speed of a ship sailing in waves always slows down due to the decrease in efficiency of the propeller. So it is necessary and essential to analyze the unsteady hydrodynamic performance of propeller in waves. This paper is based on the numerical simulation and experimental research of hydrodynamics performance when the propeller is under wave conditions. Open-water propeller performance in calm water is calculated by commercial codes and the results are compared to experimental values to evaluate the accuracy of the numerical simulation method. The first-order Volume of Fluid(VOF) wave method in STAR CCM+ is utilized to simulate the three-dimensional numerical wave. According to the above prerequisite, the numerical calculation of hydrodynamic performance of the propeller under wave conditions is conducted, and the results reveal that both thrust and torque of the propeller under wave conditions reveal intense unsteady behavior. With the periodic variation of waves, ventilation, and even an effluent phenomenon appears on the propeller. Calculation results indicate, when ventilation or effluent appears, the numerical calculation model can capture the dynamic characteristics of the propeller accurately, thus providing a significant theory foundation forfurther studying the hydrodynamic performance of a propeller in waves.
基金the National Natural Science Foundation of China (No. 50104013).
文摘After the erection of the Three Gorges Dam, the water level of Yangtze River will reach 175 m, and the average wave crest will be up to 1 m. Therefore the wave action cannot be neglected for the slope stability. Through simulation tests, the wave-induced dynamic response of the slope is analyzed. The soil body is taken as linear elastic body when it has a small deformation under the small wave action. Based on tests, the excess pore pressure and slope displacement under the loading in different wave period are analyzed. The ratio of dynamic strength and static strength to the breaking process of the slope is discussed. It is demonstrated that smaller wave period gives rise to a larger strain of the slope under the same stress. At different depth of water, different weakness effect on the stability of the soil slope is observed and the slope has an adaptability to the wave action to some extent.
文摘A moored array of circular cylinders undergoes slow oscillations in the horizontal plane,i.e.surge,sway and yaw,due to the non linear excitation of ocean waves.To evaluate wave drift damping,the slow oscillation is approximated by quasi steady motions or equivalently,a uniform flow is superposed to the wave field.In the case of yawing motion,a uniform rotation about the yawing axis is enforced to the entire fluid domain.The velocity potential is expanded into perturbation series based on two small parameters that measure wave slope and velocity of steady flow.Wave drift forces (moment) are calculated by the far field method.Experiment arrangements are also discussed.Measured data are compared to the calculated results to verify the present theory.
文摘This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.
文摘U-wave changes during treadmill exercise test were compared between 34 patientswith CAD and 33 normal controls.All of them were confirmed by coronary angiographv.Tenpatients with CAD and 1 normal subject in this study showed U-wave inversion during exercisetest.Of the 10 patients,4 had significant stenosis in one-vessel and 6 in multi-vessel of the ma-jor coronary arteries.The sensitivity,specificity and predictive value of exercise-inducedU-wave inversion were 29％, 97％ and 91％,respectively.It is proposed that exercise inducedU-wave inversion is a reliable predictive index of CAD.
文摘近年来,随着摩尔定律逐渐放缓,晶上系统(System on wafer, SoW)技术作为最热门的“超越摩尔”技术路线之一,已经成为先进封装领域的研究热点。基于晶上系统技术,将传统的毫米波收发前端阵列组件进行三维重构集成,可实现全新的轻薄化毫米波晶上阵列,具有“三免”(免连接器、免电缆、免管壳封装)的颠覆性结构。本文针对毫米波晶上阵列的自动化测试需求,创新性提出一种毫米波双面晶圆测试方法,突破了多尺寸双面晶圆可靠固定、双面探针精确对准和自动切换以及扎针强度精确控制和实时调节等关键技术,在此基础上研制出毫米波双面晶圆自动测试平台,解决了毫米波收发前端晶上阵列三维测试的难点,对毫米波晶上系统的测试具有重大参考价值。
