The wheels have a considerable influence on the aerodynamic properties and can contribute up to 25%of the total drag on modern vehicles.In this study,the effect of the wheel spoke structure on the aerodynamic performa...The wheels have a considerable influence on the aerodynamic properties and can contribute up to 25%of the total drag on modern vehicles.In this study,the effect of the wheel spoke structure on the aerodynamic performance of the isolated wheel is investigated.Subsequently,the 35°Ahmed body with an optimized spoke structure is used to analyze the flow behavior and the mechanism of drag reduction.The Fluent software is employed for this investigation,with an inlet velocity of 40 m/s.The accuracy of the numerical study is validated by comparing it with experimental results obtained from the classical Ahmed model.To gain a clearer understanding of the effects of the wheel spoke parameters on the aerodynamics of both the wheel and Ahmedmodel,and five design variables are proposed:the fillet angleα,the inside arc radius R1,the outside radius R2,and the same length of the chord L1 and L2.These variables characterize the wheel spoke structure.The Optimal Latin Hypercube designmethod is utilized to conduct the experimental design.Based on the simulation results of various wheel spoke designs,the Kriging model and the adaptive simulated annealing algorithm is selected to optimize the design parameters.The objective is to achieve the best combination for maximum drag reduction.It is indicated that the optimized spoke structure resulted in amaximum drag reduction of 5.7%and 4.7%for the drag coefficient of the isolated wheel and Ahmed body,respectively.The drag reduction is primarily attributed to changes in the flow state around the wheel,which suppressed separation bubbles.Additionally,it influenced the boundary layer thickness around the car body and reduced the turbulent kinetic energy in the wake flow.These effects collectively contributed to the observed drag reduction.展开更多
give someone the cold shoulder的意思是“采取冷淡的态度”。shoulder是指“牛羊等连前腿在内的肩肉”,因此,所谓cold shoulde就是“凉了的前腿肉”的意思。古时候有这样的风俗习惯:在招待贵客时,飨以美味佳肴;对于行商和乞丐,则给“...give someone the cold shoulder的意思是“采取冷淡的态度”。shoulder是指“牛羊等连前腿在内的肩肉”,因此,所谓cold shoulde就是“凉了的前腿肉”的意思。古时候有这样的风俗习惯:在招待贵客时,飨以美味佳肴;对于行商和乞丐,则给“凉了的前腿肉”吃。这就是give someone thecold shoulder具有“采取冷淡态度”意思的来源。在日常会话中,give someone the cold shoulder, 既可以指表示冷淡的耸肩动作,也可以指“采取冷淡的态度”。例如:展开更多
Shoppers,crowding into the West End of Londonyesterday for the start of sales,answered demands fromthe police to use public transportation rather than theircars.They also decided not to invite danger,after thebursting...Shoppers,crowding into the West End of Londonyesterday for the start of sales,answered demands fromthe police to use public transportation rather than theircars.They also decided not to invite danger,after thebursting of a bomb in the West End on Christmasevening,by not waiting in line outside the shops.“Iwould have been very worried of what they had.”saidMr Harry Weblin,manager of Liberty’s.Last night the police,which operated a big actionincluding special searches outside the main shops,spoke highly of the common sense of the展开更多
介绍了麦克风效应和洛伦兹力作用对C-ADS注入器I的Spoke012超导腔的影响以及腔的压电陶瓷快调谐传递函数的特性,并详细叙述了依据传递函数特性搭建频率控制基本环路及利用阻尼技术来对腔的特定频率边带进行抑制的方法。所设计的PI控制...介绍了麦克风效应和洛伦兹力作用对C-ADS注入器I的Spoke012超导腔的影响以及腔的压电陶瓷快调谐传递函数的特性,并详细叙述了依据传递函数特性搭建频率控制基本环路及利用阻尼技术来对腔的特定频率边带进行抑制的方法。所设计的PI控制基本环路和特定频率边带抑制环路在实际运行中得到使用,前者有效抑制了低频振荡,后者抑制特定频率振荡幅度达到15 d B。展开更多
Jack London(1876-1916) is known as an American novelist in the early 20 th century. He lived in the gilded times that were full of different kinds of trend of thought in literature and art. His experiences made his li...Jack London(1876-1916) is known as an American novelist in the early 20 th century. He lived in the gilded times that were full of different kinds of trend of thought in literature and art. His experiences made his life more colorful. He saw the cruelty of Capitalism and spoke for Socialism with his words. His novels, The Call of the Wild, The leading character, in their own way, witnessed the survival of the fittest in their life. Jack London told the unchanged truth — the survival of the fittest in his brilliant words. It is difficult to change the world, but easy to change oneself. One adjusts to his life space with his"evolution",and one goes in a new environment where every cloud has a silver lining.展开更多
在阅读英文书刊的过程中,我们可以注意到英语中有大量的短语包含两个同一词性的词,如short and sweet(敏捷的;不迟延的;说话扼要的),life and soul(中心人物;主脑,精力最充沛的人),pick and Choose(挑三拣四;挑肥拣瘦)等等,当中用连接词...在阅读英文书刊的过程中,我们可以注意到英语中有大量的短语包含两个同一词性的词,如short and sweet(敏捷的;不迟延的;说话扼要的),life and soul(中心人物;主脑,精力最充沛的人),pick and Choose(挑三拣四;挑肥拣瘦)等等,当中用连接词AND连接起来,表示一个整体的概念。这种词叫着“成对词(Twin Words)”。展开更多
The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conduct...The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conducting(SC)linear accelerator(linac)for the ADS project in China.The injector adopted a four-vane copper structure radio frequency quadrupole(RFQ)with an output energy of 3.2 MeV and an SC section accommodating 14 β_(g)=0.12 single spoke cavities,14 SC solenoids,and 14 cold beam position monitors(BPMs).A 10-MeV pulsed beam with a beam current of 10 mA and a 2-mA continuous wave(CW)beam were successfully shooting through.The commissioning results confirmed the feasibility of using a 325-MHz spoke-type cavity for accelerating the proton beam in the low β and medium β sections.This paper describes the results achieved,the difficulties encountered,and the experiences obtained during commissioning.展开更多
现代英语中有大量表达无生命事物运动、变化和作用的动词,常常与作主语的无生命名词连用,例如:make,bring,come,do(with),enable,tell,say,see,show,speak,expand,prevent,remind,release,drive,grip,give,change,disturb,lead(to)……...现代英语中有大量表达无生命事物运动、变化和作用的动词,常常与作主语的无生命名词连用,例如:make,bring,come,do(with),enable,tell,say,see,show,speak,expand,prevent,remind,release,drive,grip,give,change,disturb,lead(to)……等等。现代英语中的一个趋势是:许多表示实际动作和言语思维动作的动词,通过“拟人化”和词义“隐喻”的手段,愈来愈多地与非生命词主语连用。如: 1.And even in his unhappiest moments field and skyspoke to him with a deep and powerful persuasion.展开更多
基金funding of the National Natural Science Foundation of China (Nos.52072156,51605198)Postdoctoral Foundation of China (2020M682269).
文摘The wheels have a considerable influence on the aerodynamic properties and can contribute up to 25%of the total drag on modern vehicles.In this study,the effect of the wheel spoke structure on the aerodynamic performance of the isolated wheel is investigated.Subsequently,the 35°Ahmed body with an optimized spoke structure is used to analyze the flow behavior and the mechanism of drag reduction.The Fluent software is employed for this investigation,with an inlet velocity of 40 m/s.The accuracy of the numerical study is validated by comparing it with experimental results obtained from the classical Ahmed model.To gain a clearer understanding of the effects of the wheel spoke parameters on the aerodynamics of both the wheel and Ahmedmodel,and five design variables are proposed:the fillet angleα,the inside arc radius R1,the outside radius R2,and the same length of the chord L1 and L2.These variables characterize the wheel spoke structure.The Optimal Latin Hypercube designmethod is utilized to conduct the experimental design.Based on the simulation results of various wheel spoke designs,the Kriging model and the adaptive simulated annealing algorithm is selected to optimize the design parameters.The objective is to achieve the best combination for maximum drag reduction.It is indicated that the optimized spoke structure resulted in amaximum drag reduction of 5.7%and 4.7%for the drag coefficient of the isolated wheel and Ahmed body,respectively.The drag reduction is primarily attributed to changes in the flow state around the wheel,which suppressed separation bubbles.Additionally,it influenced the boundary layer thickness around the car body and reduced the turbulent kinetic energy in the wake flow.These effects collectively contributed to the observed drag reduction.
文摘Shoppers,crowding into the West End of Londonyesterday for the start of sales,answered demands fromthe police to use public transportation rather than theircars.They also decided not to invite danger,after thebursting of a bomb in the West End on Christmasevening,by not waiting in line outside the shops.“Iwould have been very worried of what they had.”saidMr Harry Weblin,manager of Liberty’s.Last night the police,which operated a big actionincluding special searches outside the main shops,spoke highly of the common sense of the
文摘介绍了麦克风效应和洛伦兹力作用对C-ADS注入器I的Spoke012超导腔的影响以及腔的压电陶瓷快调谐传递函数的特性,并详细叙述了依据传递函数特性搭建频率控制基本环路及利用阻尼技术来对腔的特定频率边带进行抑制的方法。所设计的PI控制基本环路和特定频率边带抑制环路在实际运行中得到使用,前者有效抑制了低频振荡,后者抑制特定频率振荡幅度达到15 d B。
文摘Jack London(1876-1916) is known as an American novelist in the early 20 th century. He lived in the gilded times that were full of different kinds of trend of thought in literature and art. His experiences made his life more colorful. He saw the cruelty of Capitalism and spoke for Socialism with his words. His novels, The Call of the Wild, The leading character, in their own way, witnessed the survival of the fittest in their life. Jack London told the unchanged truth — the survival of the fittest in his brilliant words. It is difficult to change the world, but easy to change oneself. One adjusts to his life space with his"evolution",and one goes in a new environment where every cloud has a silver lining.
文摘在阅读英文书刊的过程中,我们可以注意到英语中有大量的短语包含两个同一词性的词,如short and sweet(敏捷的;不迟延的;说话扼要的),life and soul(中心人物;主脑,精力最充沛的人),pick and Choose(挑三拣四;挑肥拣瘦)等等,当中用连接词AND连接起来,表示一个整体的概念。这种词叫着“成对词(Twin Words)”。
基金This work was supported by Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA03030201)the Key Laboratory of Particle Acceleration Physics and Technology Autonomous Foundation of CAS China(No.JSQ2017ZZ01).
文摘The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conducting(SC)linear accelerator(linac)for the ADS project in China.The injector adopted a four-vane copper structure radio frequency quadrupole(RFQ)with an output energy of 3.2 MeV and an SC section accommodating 14 β_(g)=0.12 single spoke cavities,14 SC solenoids,and 14 cold beam position monitors(BPMs).A 10-MeV pulsed beam with a beam current of 10 mA and a 2-mA continuous wave(CW)beam were successfully shooting through.The commissioning results confirmed the feasibility of using a 325-MHz spoke-type cavity for accelerating the proton beam in the low β and medium β sections.This paper describes the results achieved,the difficulties encountered,and the experiences obtained during commissioning.
文摘现代英语中有大量表达无生命事物运动、变化和作用的动词,常常与作主语的无生命名词连用,例如:make,bring,come,do(with),enable,tell,say,see,show,speak,expand,prevent,remind,release,drive,grip,give,change,disturb,lead(to)……等等。现代英语中的一个趋势是:许多表示实际动作和言语思维动作的动词,通过“拟人化”和词义“隐喻”的手段,愈来愈多地与非生命词主语连用。如: 1.And even in his unhappiest moments field and skyspoke to him with a deep and powerful persuasion.
