Abstract Tidal current energy is renewable and sustainable, which is a promising altemative energy resource for the future elec- tricity supply. The straight-bladed vertical-axis turbine is regarded as a useful tool t...Abstract Tidal current energy is renewable and sustainable, which is a promising altemative energy resource for the future elec- tricity supply. The straight-bladed vertical-axis turbine is regarded as a useful tool to capture the tidal current energy especially under low-speed conditions. A 2D unsteady numerical model based on Ansys-Fluent 12.0 is established to conduct the numerical simulation, which is validated by the corresponding experimental data. For the unsteady calculations, the SST model, 2x 105 and 0.01 s are se- lected as the proper turbulence model, mesh number, and time step, respectively. Detailed contours of the velocity distributions around the rotor blade foils have been provided for a flow field analysis. The tip speed ratio （TSR） determines the azimuth angle of the appearance of the torque peak, which occurs once for a blade in a single revolution. It is also found that simply increasing the incident flow velocity could not improve the turbine performance accordingly. The peaks of the averaged power and torque coeffi- cients appear at TSRs of 2.1 and 1.8, respectively. Furthermore, several shapes of the duct augmentation are proposed to improve the turbine performance by contracting the flow path gradually from the open mouth of the duct to the rotor. The duct augmentation can significantly enhance the power and torque output. Furthermore, the elliptic shape enables the best performance of the turbine. The numerical results prove the capability of the present 2D model for the unsteady hydrodynamics and an operating performance analy- sis of the vertical tidal stream turbine.展开更多
建立了一个SBS(基于服务的系统,service based system)应用端到端性能评价模型,并在该模型的基础上提出了SBS应用动态资源分配方法,该方法通过将静态的初始资源分配和动态的资源分配方案调整相结合,能够适应用户访问行为的动态变化,保证...建立了一个SBS(基于服务的系统,service based system)应用端到端性能评价模型,并在该模型的基础上提出了SBS应用动态资源分配方法,该方法通过将静态的初始资源分配和动态的资源分配方案调整相结合,能够适应用户访问行为的动态变化,保证SBS应用端到端性能.在SBS应用动态资源分配问题求解中,提出了服务吞吐量约束确定算法并在此基础上给出了SBS应用动态资源分配算法,该算法根据SBS应用吞吐量约束确定服务资源需求量并在此基础上通过起始服务到服务间的转移时间计算服务的资源分配时刻,从而能够在保证SBS应用端到端性能约束的同时提高资源利用率.实验验证了所提出的基于SBS应用端到端性能评价模型的动态资源分配方法的有效性.展开更多
Objective：The rapid expansion of knowledge regarding the functional anatomy of hand and wrist,increasing functional demands of senior citizens and improved methodologies of achieving and maintaining anatomic restorat...Objective：The rapid expansion of knowledge regarding the functional anatomy of hand and wrist,increasing functional demands of senior citizens and improved methodologies of achieving and maintaining anatomic restoration of distal radius fractures has generated a renewed interest in addressing these fractures in a more precise manner.The purpose of our study was to evaluate the difference in patients function among those treated by 1） closed reduction and Plaster of Paris cast,2） distractor application,or 3） open reduction and internal fixation with a volar plate,and to assess the treatment choice for each particular fracture type.Methods：A prospective study was carried out on 60 patients with fractures of the distal end radius.Fractures were classified according to the AO classification into type A （extra-articular）,type B （partial articular） and type C （complete articular）.After initial evaluation patients were taken up for either conservative or operative treatment and were followed up for two years.Results：Anatomical results were evaluated according to the Sarmiento＇s modification of Lindstrom Criteria,which showed that excellent results were more frequent with open reduction and internal fixation using the plating technique.Clinical and functional results were evaluated according to the demerit point system of Gartland and Werley with Sarmiento modification,which was revealed to relate with the type of treatment techniques.Conclusion：There is no customized solution for all the fractures of the distal radius.The choice of treatment should be based on the fracture type,the patient＇s characteristics,the patient＇s demands and the treating surgeon＇s experience and preference.展开更多
Lucas-Kanade(LK) algorithm, usually used in optical flow filed, has recently received increasing attention from PIV community due to its advanced calculation efficiency by GPU acceleration. Although applications of th...Lucas-Kanade(LK) algorithm, usually used in optical flow filed, has recently received increasing attention from PIV community due to its advanced calculation efficiency by GPU acceleration. Although applications of this algorithm are continuously emerging,a systematic performance evaluation is still lacking. This forms the primary aim of the present work. Three warping schemes in the family of LK algorithm: forward/inverse/symmetric warping, are evaluated in a prototype flow of a hierarchy of multiple two-dimensional vortices. Second-order Newton descent is also considered here. The accuracy & efficiency of all these LK variants are investigated under a large domain of various influential parameters. It is found that the constant displacement constraint, which is a necessary building block for GPU acceleration, is the most critical issue in affecting LK algorithm's accuracy, which can be somehow ameliorated by using second-order Newton descent. Moreover, symmetric warping outbids the other two warping schemes in accuracy level, robustness to noise, convergence speed and tolerance to displacement gradient, and might be the first choice when applying LK algorithm to PIV measurement.展开更多
基金the financial support provided by the National Natural Science Foundation of China (51279190 and 51311140259)National High Technology Research and Development Program of China (863 Project,2012AA052601)+2 种基金Shandong Natural Science Funds for Distinguished Young Scholar (JQ201314)Qingdao Municipal Science & Technology Program (13-4-1-38hy and 14-9-1-5-hy)the Program of Introducing Talents of Discipline to Universities (111 Project,B14028)
文摘Abstract Tidal current energy is renewable and sustainable, which is a promising altemative energy resource for the future elec- tricity supply. The straight-bladed vertical-axis turbine is regarded as a useful tool to capture the tidal current energy especially under low-speed conditions. A 2D unsteady numerical model based on Ansys-Fluent 12.0 is established to conduct the numerical simulation, which is validated by the corresponding experimental data. For the unsteady calculations, the SST model, 2x 105 and 0.01 s are se- lected as the proper turbulence model, mesh number, and time step, respectively. Detailed contours of the velocity distributions around the rotor blade foils have been provided for a flow field analysis. The tip speed ratio （TSR） determines the azimuth angle of the appearance of the torque peak, which occurs once for a blade in a single revolution. It is also found that simply increasing the incident flow velocity could not improve the turbine performance accordingly. The peaks of the averaged power and torque coeffi- cients appear at TSRs of 2.1 and 1.8, respectively. Furthermore, several shapes of the duct augmentation are proposed to improve the turbine performance by contracting the flow path gradually from the open mouth of the duct to the rotor. The duct augmentation can significantly enhance the power and torque output. Furthermore, the elliptic shape enables the best performance of the turbine. The numerical results prove the capability of the present 2D model for the unsteady hydrodynamics and an operating performance analy- sis of the vertical tidal stream turbine.
文摘建立了一个SBS(基于服务的系统,service based system)应用端到端性能评价模型,并在该模型的基础上提出了SBS应用动态资源分配方法,该方法通过将静态的初始资源分配和动态的资源分配方案调整相结合,能够适应用户访问行为的动态变化,保证SBS应用端到端性能.在SBS应用动态资源分配问题求解中,提出了服务吞吐量约束确定算法并在此基础上给出了SBS应用动态资源分配算法,该算法根据SBS应用吞吐量约束确定服务资源需求量并在此基础上通过起始服务到服务间的转移时间计算服务的资源分配时刻,从而能够在保证SBS应用端到端性能约束的同时提高资源利用率.实验验证了所提出的基于SBS应用端到端性能评价模型的动态资源分配方法的有效性.
文摘Objective：The rapid expansion of knowledge regarding the functional anatomy of hand and wrist,increasing functional demands of senior citizens and improved methodologies of achieving and maintaining anatomic restoration of distal radius fractures has generated a renewed interest in addressing these fractures in a more precise manner.The purpose of our study was to evaluate the difference in patients function among those treated by 1） closed reduction and Plaster of Paris cast,2） distractor application,or 3） open reduction and internal fixation with a volar plate,and to assess the treatment choice for each particular fracture type.Methods：A prospective study was carried out on 60 patients with fractures of the distal end radius.Fractures were classified according to the AO classification into type A （extra-articular）,type B （partial articular） and type C （complete articular）.After initial evaluation patients were taken up for either conservative or operative treatment and were followed up for two years.Results：Anatomical results were evaluated according to the Sarmiento＇s modification of Lindstrom Criteria,which showed that excellent results were more frequent with open reduction and internal fixation using the plating technique.Clinical and functional results were evaluated according to the demerit point system of Gartland and Werley with Sarmiento modification,which was revealed to relate with the type of treatment techniques.Conclusion：There is no customized solution for all the fractures of the distal radius.The choice of treatment should be based on the fracture type,the patient＇s characteristics,the patient＇s demands and the treating surgeon＇s experience and preference.
基金supported by the National Natural Science Foundation of China(Grant Nos.11372001 and 11490552)
文摘Lucas-Kanade(LK) algorithm, usually used in optical flow filed, has recently received increasing attention from PIV community due to its advanced calculation efficiency by GPU acceleration. Although applications of this algorithm are continuously emerging,a systematic performance evaluation is still lacking. This forms the primary aim of the present work. Three warping schemes in the family of LK algorithm: forward/inverse/symmetric warping, are evaluated in a prototype flow of a hierarchy of multiple two-dimensional vortices. Second-order Newton descent is also considered here. The accuracy & efficiency of all these LK variants are investigated under a large domain of various influential parameters. It is found that the constant displacement constraint, which is a necessary building block for GPU acceleration, is the most critical issue in affecting LK algorithm's accuracy, which can be somehow ameliorated by using second-order Newton descent. Moreover, symmetric warping outbids the other two warping schemes in accuracy level, robustness to noise, convergence speed and tolerance to displacement gradient, and might be the first choice when applying LK algorithm to PIV measurement.
