期刊文献+
共找到6,053篇文章
< 1 2 250 >
每页显示 20 50 100
Research and development of a 0.5-m-long helical superconducting undulator prototype
1
作者 Xiang-Chen Yang Xiao-Wu Yu +6 位作者 Jun-Hao Wei Xiang-Zhen Zhang Zi-Lin Chen Xiao-Juan Bian He-Ting Li Guang-Yao Feng Yu-Hui Li 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2024年第10期86-95,共10页
The helical undulator is in high demand in synchrotron radiation facilities for circular polarization generation.Owing to the higher field strength provided by the superconducting undulator compared to the conventiona... The helical undulator is in high demand in synchrotron radiation facilities for circular polarization generation.Owing to the higher field strength provided by the superconducting undulator compared to the conventional permanent-magnet undulator,greater research efforts should be directed toward this area.The helical superconducting undulator holds great potential in synchrotron radiation facilities,especially in low-energy storage rings that seek circularly polarized radiation with the highest possible radiation flux.Following the successful development of planar superconducting undulators,the Institute of High Energy Physics conducted research and development for the helical superconducting undulator.A 0.5-m-long Deltatype superconducting undulator prototype was developed and tested.Detailed information on the design,fabrication,and cryogenic testing of the prototype is presented and discussed. 展开更多
关键词 helical Superconducting undulator DELTA
下载PDF
Suppression of Vortex-Induced Vibration Caused by A Terebridae-Inspired Cylinder with Different Helical Angles
2
作者 YU Qi-dong MAO Zhao-yong +1 位作者 TIAN Wen-long WANG Wei 《China Ocean Engineering》 SCIE EI CSCD 2024年第5期739-754,共16页
Biomimetic design has recently received widespread attention.Inspired by the Terebridae structure,this paper provides a structural form for suppressing vortex-induced vibration(VIV)response.Four different structural f... Biomimetic design has recently received widespread attention.Inspired by the Terebridae structure,this paper provides a structural form for suppressing vortex-induced vibration(VIV)response.Four different structural forms are shown,including the traditional smooth cylinder(P0),and the Terebridae-inspired cylinder with the helical angle of 30°(P_(30)),60°(P_(60)),and 90°(P_(90)).Computational fluid dynamics(CFD)method is adopted to solve the flow pass the Terebridae-inspired structures,and the vibration equation is solved using the Newmark-βmethod.The results show that for P_(30),P_(60) and P_(90),the VIV responses are effectively suppressed in the lock-in region,and P_(60) showed the best VIV suppression performance.The transverse amplitude and the downstream amplitude can be reduced by 82.67%and 91.43%respectively for P_(60) compared with that for P0,and the peak of the mean-drag coefficient is suppressed by 53.33%.The Q-criterion vortices of P_(30),P_(60),and P_(90) are destroyed,with irregular vortices shedding.It is also found that the boundary layer separation is located on the Terebridae-inspired ribs.The twisted ribs cause the separation point to constantly change along the spanwise direction,resulting in the development of the boundary layer separation being completely destroyed.The strength of the wake flow is significantly weakened for the Terebridae-inspired cylinder. 展开更多
关键词 vortex-induced vibration(VIV) Terebridae CYLINDER SUPPRESSION helical angle
下载PDF
Multi-physical fields distribution in billet during helical electromagnetic stirring:A numerical simulation research
3
作者 Dong Pan Qing-tao Guo +3 位作者 Kai-lun Zhang Fu-zhi Yu Yu-ying Li Yu-bao Xiao 《China Foundry》 SCIE EI CAS CSCD 2024年第1期51-59,共9页
Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimens... Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow of molten metal and eliminating solidification defects.In this study,the single-winding helical stirring(SWHS)was introduced,offering advantages such as smaller volume and lower electromagnetic shielding compared to traditional helical stirring methods.Following a comprehensive numerical simulation,the stirring parameters of SWHS were adjusted to yoke inclination angle of 43°and frequency of 12 Hz.The higher electromagnetic force and flow velocity in drawing direction,as well as the lower temperature gradient induced by the SWHS,are positive factors for homogeneous solidification of billet.The experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the SWHS process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element segregation.The SWHS process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,SWHS holds great promise as a potential approach for improving the quality of continuous casting billets. 展开更多
关键词 BILLET electromagnetic stirring helical SOLIDIFICATION element segregation numerical simulation
下载PDF
Advancing high-speed train gearbox durability:enhanced bearing load and contact stress through transition from helical to herringbone gears
4
作者 Hao Wu Jing Wei +2 位作者 Pingbo Wu Fansong Li Yayun Qi 《Railway Engineering Science》 EI 2024年第4期461-479,共19页
High-speed trains typically utilize helical gear transmissions,which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings.This paper focuses on the gearbox bearings,es... High-speed trains typically utilize helical gear transmissions,which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings.This paper focuses on the gearbox bearings,establishing dynamic models for both helical gear and herringbone gear transmissions in high-speed trains.The modeling particularly emphasizes the precision of the bearings at the gearbox's pinion and gear wheels.Using this model,a comparative analysis is conducted on the bearing loads and contact stresses of the gearbox bearings under uniform-speed operation between the two gear transmissions.The findings reveal that the helical gear transmission generates axial forces leading to severe load imbalance on the bearings at both sides of the large gear,and this imbalance intensifies with the increase in train speed.Consequently,this results in a significant increase in contact stress on the bearings on one side.The adoption of herringbone gear transmission effectively suppresses axial forces,resolving the load imbalance issue and substantially reducing the contact stress on the originally biased side of the bearings.The study demonstrates that employing herringbone gear transmission can significantly enhance the service performance of high-speed train gearbox bearings,thereby extending their service life. 展开更多
关键词 High-speed train Herringbone gear helical gear Gearbox bearings Contact stress
下载PDF
Mathematical Modelling and Design of Helical Coil Heat Exchanger for Production of Hot Air for Fluidized Bed Dryer
5
作者 Iniubong James Uwa Uwem Ekwere Inyang Innocent Oseribho Oboh 《Advances in Chemical Engineering and Science》 CAS 2024年第3期125-136,共12页
In global industrialization, efforts have been made to increase the rate of heat transfer in heat exchanger, minimizing the size of heat exchanger to reduce cost as well as increasing the effectiveness. Helical coil h... In global industrialization, efforts have been made to increase the rate of heat transfer in heat exchanger, minimizing the size of heat exchanger to reduce cost as well as increasing the effectiveness. Helical coil heat exchanger (HCHE) has been proven to be effective in improving heat transfer due to its large surface area. In this study, HCHE was designed to provide hot air needed for fluidized bed drying processes. The HCHE design model was fabricated and evaluated to study the efficiency of the hot air output for a laboratory fluidized bed dryer. The mathematical model for estimation of the final (output) temperature of air, Taf, passing through the HCHE was developed and validated experimentally. The drying of bitter kola particulates was carried out with a drying temperature of 50C 3C and a bed height-to-bed diameter ratio (H/D) of 1.5. The time taken to dry bitter kola particulates to 0.4% moisture content was 1 hour 45 minutes. Hence, HCHE is recommended for use in the production of hot for laboratory-scale fluidized bed dryers. 展开更多
关键词 helical Coil Heat Exchanger Fluidized Bed Dryer Heat Transfer Output Air Temperature
下载PDF
Failure Envelopes of Single-Plate Rigid Helical Anchors for Floating Offshore Wind Turbine
6
作者 CHEN Hong-zhen WANG Le +3 位作者 TIAN Ying-hui ZHANG Chun-hui SHEN Zhi-chao LIU Meng-meng 《China Ocean Engineering》 SCIE EI CSCD 2023年第6期1000-1010,共11页
Helical anchor is a kind of novel foundation for floating offshore wind turbines,which should be subjected to combined tensile loading caused by wind,wave and current.However,the research about the capacity of helical... Helical anchor is a kind of novel foundation for floating offshore wind turbines,which should be subjected to combined tensile loading caused by wind,wave and current.However,the research about the capacity of helical anchor was mainly examined under uniaxial loading and scarcely explored under combined loading.In this study,three-dimensional finite element limit analysis is adopted to assess the bearing capacities of single-plate rigid helical anchors with different ratios of helix to shaft diameter,D_(H)/D_(S) and embedment ratios L/D_(S).Result shows that the vertical,horizontal and moment bearing capacities increase with increasing D_(H)/D_(S) and L/D_(S).The normalized V-H failure envelopes expands with increasing L/D_(S),while the normalized V-M failure envelopes tend to contract with the increase of D_(H)/D_(S).With increasing D_(H)/D_(S) or decreasing L/D_(S),the normalized H-M failure envelopes expand when the horizontal and moment loading act in the same direction and contract when they act in the opposite direction.The effect of D_(H)/D_(S) and L/D_(S) on the shape of H-M failure envelope become insignificant when L/D_(S)≥4.A series of failure mechanisms under different loading conditions were observed and can be used to explain the trend.Besides,a series of approximate expressions were proposed to fit the uniaxial bearing capacities and the failure envelopes. 展开更多
关键词 helical anchors bearing capacity failure envelope CLAY
下载PDF
Helically symmetric equilibria for some ideal and resistive MHD plasmas with incompressible flows
7
作者 S.M.Moawad O.H.El-Kalaawy H.M.Shaker 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2023年第2期192-209,共18页
In this paper, the problem of finding exact solutions to the magnetohydrodynamic(MHD) equations in the presence of incompressible mass flows with helical symmetry is considered. For ideal flows, a similarity reduction... In this paper, the problem of finding exact solutions to the magnetohydrodynamic(MHD) equations in the presence of incompressible mass flows with helical symmetry is considered. For ideal flows, a similarity reduction method is used to obtain exact solutions for several MHD flows with nonlinear variable Mach number. For resistive flows parallel to a magnetic field, the governing equilibrium equation is derived. The MHD equilibrium state of a helically symmetric incompressible flow is governed by a second-order elliptic partial differential equation(PDE) for the helical magnetic flux function. Exact solutions for the latter equation are obtained. Also, the equilibrium equations of a gravitating plasma with incompressible flow are derived. 展开更多
关键词 MAGNETOHYDRODYNAMICS helical symmetry resistivity incompressible ows exact equilibria
下载PDF
Improving energy storage by PCM using hybrid nanofluid[(SWCNTs-CuO)/H_(2)O]and a helical(spiral)coil:Hybrid passive techniques
8
作者 Aliakbar Hosseinpour Mohsen Pourfallah Mosayeb Gholinia 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2023年第4期299-310,共12页
The aim of this study is the numerical analysis of the melting process of the phase change material(PCM)in a spiral coil.The space between the inner tube and outer shell is filled with RT-50 as PCM.Moreover,the hybrid... The aim of this study is the numerical analysis of the melting process of the phase change material(PCM)in a spiral coil.The space between the inner tube and outer shell is filled with RT-50 as PCM.Moreover,the hybrid nanofluid(with a carbon component)flows through the inner tube.The novelty of this work is to use different configurations of fin and different percentage of hybrid nanoparticles(SWCNTs-Cu O)on the PCM melting process.In the numerical model created by ANSYS-Fluent,the effect of various inlet temperatures is investigated.The results indicate that the extended surface created by extra fin has a dominant effect on melting time,so by adding the third fin,the melting time is reduced by 39.24%.The next most influential factor in PCM melting is the inlet temperature of the working fluid,so that 10°C increment of temperature result in the PCM melting time decreased by 35.41%. 展开更多
关键词 PCM melting helical coli Thermal energy storage CFD analysis
下载PDF
Effect of antenna helicity on discharge characteristics of helicon plasma under a divergent magnetic field
9
作者 孙萌 徐晓芳 +3 位作者 王陈文 尹贤轶 陈强 张海宝 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第6期50-59,共10页
The characteristics of the blue core phenomenon observed in a divergent magnetic field helicon plasma are investigated using two different helical antennas, namely right-handed and lefthanded helical antennas. The mod... The characteristics of the blue core phenomenon observed in a divergent magnetic field helicon plasma are investigated using two different helical antennas, namely right-handed and lefthanded helical antennas. The mode transition, discharge image, spatial profiles of plasma density and electron temperature are diagnosed using a Langmuir probe, a Nikon D90 camera,an intensified charge-coupled device camera and an optical emission spectrometer, respectively.The results demonstrated that the blue core phenomenon appeared in the upstream region of the discharge tube at a fixed magnetic field under both helical antennas. However, it is more likely to appear in a right-handed helical antenna, in which the plasma density and ionization rate of the helicon plasma are higher. The spatial profiles of the plasma density and electron temperature are also different in both axial and radial directions for these two kinds of helical antenna. The wavelength calculated based on the dispersion relation of the bounded whistler wave is consistent with the order of magnitude of plasma length. It is proved that the helicon plasma is part of the wave mode discharge mechanism. 展开更多
关键词 helicon plasma non-uniform magnetic field helical antenna blue core discharge mechanism
下载PDF
Multi-objective Optimization of a Two-Stage Helical Gearbox to Improve Efficiency and Reduce Height
10
作者 Tran Quoc Hung Truong Thi Thu Huong 《Journal of Environmental Science and Engineering(B)》 2023年第5期236-247,共12页
The goal of this research is to look at multi-target optimization of a two-stage helical gearbox in order to determine the best key design elements for reducing gearbox height and enhancing gearbox efficiency.To do th... The goal of this research is to look at multi-target optimization of a two-stage helical gearbox in order to determine the best key design elements for reducing gearbox height and enhancing gearbox efficiency.To do this,the method known as Taguchi and GRA(Grey Relation Analysis)were used in two stages to address the problem.The single-objective optimization problem was addressed first to close the gap between variable levels,and then the multi-objective optimization problem was solved to determine the best primary design variables.The first and second stage CWFWs(Coefficients of Wheel Face Width),ACS(Permissible Contact Stresses),and first stage gear ratio were also calculated.The study’s findings were utilized to identify the best values for five critical design aspects of a two-stage helical gearbox. 展开更多
关键词 helical gearbox multi-objective optimization gear ratio gearbox height gearbox efficiency.
下载PDF
A new heat transfer correlation for flow boiling in helically coiled tubes 被引量:1
11
作者 冀翠莲 韩吉田 +2 位作者 刘晓鹏 邵莉 陈常念 《Journal of Southeast University(English Edition)》 EI CAS 2015年第3期380-383,共4页
Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of th... Based on the superposition principle of the nucleate boiling and convective heat transfer terms,a new correlation is developed for flow boiling heat transfer characteristics in helically coiled tubes.The effects of the geometric and system parameters on heat transfer characteristics in helically coiled tubes are investigated by collecting large amounts of experimental data and analyzing the heat transfer mechanisms. The existing correlations are divided into two categories,and they are calculated with the experimental data.The Dn factor is introduced to take into account the effect of a complex geometrical structure on flow boiling heat transfer.A new correlation is developed for predicting the flow boiling heat transfer coefficients in the helically coiled tubes,which is validated by the experimental data of R134a flow boiling heat transfer in them;and the average relative error and root mean square error of the new correlation are calculated.The results show that the new correlation agrees well with the experimental data,indicating that the new correlation can be used for predicting flow boiling heat transfer characteristics in the helically coiled tubes. 展开更多
关键词 helically coiled tube flow boiling heat transfer coefficient correlation heat transfer
下载PDF
立管扰流装置Helical Strakes的数值模拟分析 被引量:8
12
作者 王增波 黄维平 +3 位作者 苑健康 柳伟 芦斐 韩辉 《石油化工高等学校学报》 CAS 2011年第4期79-83,共5页
泻涡脱落诱发的涡激振动是海洋立管疲劳破坏的主要诱因,利用Helical Strakes(螺旋侧板)抑制涡激振动对立管的损伤。通过CFD数值模拟软件,对光滑立管和覆盖两种不同螺旋侧板的立管,在不同的雷诺数下进行模拟分析。将得到拖曳力和升力结... 泻涡脱落诱发的涡激振动是海洋立管疲劳破坏的主要诱因,利用Helical Strakes(螺旋侧板)抑制涡激振动对立管的损伤。通过CFD数值模拟软件,对光滑立管和覆盖两种不同螺旋侧板的立管,在不同的雷诺数下进行模拟分析。将得到拖曳力和升力结果与现有的数值和实验结果进行对比,得到相关的拖曳力系数和升力,研究Helical Strakes的相关特性。数值模拟结果表明,螺旋侧板可以影响拖曳力和升力的变化,扰乱流场,很好地抑制漩涡的产生。 展开更多
关键词 海洋立管 涡激振动 拖曳力系数 升力系数 CFD
下载PDF
Helical Bulbous Loop推上颌磨牙向远中移动的临床应用
13
作者 贵林 杨茜 王静 《大连医科大学学报》 CAS 2008年第6期583-584,共2页
[目的]用Helical bulbous loop远中移动上颌磨牙,探寻该技术的临床效果以及操作要点和优势。[方法]对磨牙关系为Ⅱ类,牙列为中度拥挤,牙体牙周健康的20例正畸患者,采用该技术推上颌磨牙远中移动,测量移动的距离,每月加力1次,观察3个月。... [目的]用Helical bulbous loop远中移动上颌磨牙,探寻该技术的临床效果以及操作要点和优势。[方法]对磨牙关系为Ⅱ类,牙列为中度拥挤,牙体牙周健康的20例正畸患者,采用该技术推上颌磨牙远中移动,测量移动的距离,每月加力1次,观察3个月。[结果]所有正畸患者的磨牙远中移动效果显著,平均每月移动1.12 mm,3个月共移动最大量为3.48 mm,最小量为3.06 mm。[结论]该技术临床效果显著,操作简单,相对于其他技术优势明显,值得临床推广使用。 展开更多
关键词 上颌磨牙 远中移动 helical Bulbous LOOP
下载PDF
Forced Convection Boiling Heat Transfer and Dryout Characteristics in Helical Coiled Tubes with Various Axial Angles 被引量:4
14
作者 郭烈锦 张西民 +1 位作者 冯自平 陈学俊 《应用基础与工程科学学报》 EI CSCD 1998年第4期61-69,共9页
对水和水蒸汽汽液两相流体在螺旋轴呈各种倾角放置的螺旋管内强制对流沸腾传热与烧毁特性进行了系统地试验研究,试验中系统及结构参数范围如下:压力:P=0.4~3.0MPa质量流速:G=100~2400kg/m2·s进口... 对水和水蒸汽汽液两相流体在螺旋轴呈各种倾角放置的螺旋管内强制对流沸腾传热与烧毁特性进行了系统地试验研究,试验中系统及结构参数范围如下:压力:P=0.4~3.0MPa质量流速:G=100~2400kg/m2·s进口水温:T=30~80℃出口干度:x=-0.05~1.2管内壁面热负荷:q=0~540kE/m2试验段结构参数:总长L=6448mm,管内径d=11mm,螺旋直径D=256mm,螺旋升角β=4.27°螺旋管轴向放置倾角:水平位置(0°)、向上倾斜45°(+45°)、垂直向上(+90°)、向下倾斜45°(-45°).共进行了1050个工况的试验.试验结果表明,螺旋管内汽液两相流强制对流沸腾传热可以划分为核态沸腾区、两相流强制对流区、烧毁及烧毁后传热区等3种区域.通过数据处理和分析总结,给出了3区域间转变的边界方程,和3个区域内两相流传热系数的计算公式.根据试验观察和数据结果,对烧毁现象及烧毁点或区域发生的条件及机理进行了深入的分析研究,发现一系列有关现象的规律和特点,指出了其主要影响因素,并给出了烧毁点临界质量干度的预报公式. 展开更多
关键词 螺旋管 水/水蒸汽汽液两相流 强制对流沸腾传热 烧毁
下载PDF
二维立管Helical Strakes绕流场的ANSYS-CFD分析 被引量:8
15
作者 苑健康 黄维平 《船海工程》 2010年第4期151-155,共5页
利用ANSYS-CFD软件模拟螺旋侧板(helical strakes)对立管涡激振动的抑制作用。对二维的光滑立管和覆盖两种不同螺旋侧板高程的立管,在不同的雷诺数下进行模拟分析,将得到拖曳力和升力结果与数值和实验结果进行对比表明,螺旋侧板可以影... 利用ANSYS-CFD软件模拟螺旋侧板(helical strakes)对立管涡激振动的抑制作用。对二维的光滑立管和覆盖两种不同螺旋侧板高程的立管,在不同的雷诺数下进行模拟分析,将得到拖曳力和升力结果与数值和实验结果进行对比表明,螺旋侧板可以影响拖曳力和升力的变化,扰乱流场,很好地抑制漩涡的产生。 展开更多
关键词 海洋立管 涡激振动 螺旋侧板 拖曳力系数 升力系数 ANSYS-CFD
下载PDF
Research on the Influence of Helical Strakes on Dynamic Response of Floating Wind Turbine Platform 被引量:21
16
作者 DING Qin-wei LI Chun 《China Ocean Engineering》 SCIE EI CSCD 2017年第2期131-140,共10页
The stability of platform structure is the paramount guarantee of the safe operation of the offshore floating wind turbine. The NREL 5MW floating wind turbine is established based on the OC3-Hywind Spar Buoy platform ... The stability of platform structure is the paramount guarantee of the safe operation of the offshore floating wind turbine. The NREL 5MW floating wind turbine is established based on the OC3-Hywind Spar Buoy platform with the supplement of helical strakes for the purpose to analyze the impact of helical strakes on the dynamic response of the floating wind turbine Spar platform. The dynamic response of floating wind turbine Spar platform under wind, wave and current loading from the impact of number, height and pitch ratio of the helical strakes is analysed by the radiation and diffraction theory, the finite element method and orthogonal design method. The result reveals that the helical strakes can effectively inhibit the dynamic response of the platform but enlarge the wave exciting force; the best parameter combination is two pieces of helical strakes with the height of 15%D (D is the diameter of the platform) and the pitch ratio of 5; the height of the helical strake and its pitch ratio have significant influence on pitch response. 展开更多
关键词 floating wind turbine PLATFORM helical strakes orthogonal design
下载PDF
Performance comparison of heat exchangers using sextant/trisection helical baffles and segmental ones 被引量:5
17
作者 Yaping Chen Hongling Tang +2 位作者 JiafengWu Huaduo Gu Shifan Yang 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2019年第12期2892-2899,共8页
The shell side flow fields of both sextant and trisection helical baffle heat exchangers are presented on meridian and multilayer hexagon slices.It verifies that the performance of sextant schemes is better than those... The shell side flow fields of both sextant and trisection helical baffle heat exchangers are presented on meridian and multilayer hexagon slices.It verifies that the performance of sextant schemes is better than those of the other kinds of helical baffle heat exchangers.The main mechanisms are due to the restricted leakage flow in the minimized gaps with increased baffle number and by one row of tubes dampen the leakage flow in the circumferential overlapped area of the adjacent helical baffles.The performance features were simulated on two different angled sextant helical heat exchangers and each compared with two trisection ones of either identical helical pitch or identical incline angle.The results verified that the performances of helical heat exchangers are mainly determined by the helical pitch rather than the baffle incline angle.The average values of comprehensive index hoΔpo-1/3 of the trisection helical schemes T-24.1°and T-29.7°are correspondingly 3.47%and 3.34%lower than those of the sextant ones X-20°and X-25°with identical helical pitches.The comparison results show that the average values of shell side h.t.c.hoand comprehensive index hoΔpo-1/3 of the optimal dual helix sextant scheme DX30°are respectively 7.22%and 23.56%higher than those of the segment scheme S100. 展开更多
关键词 HEAT transfer Computational fluid dynamics Convection helical BAFFLE HEAT EXCHANGERS SEXTANT helical baffles
下载PDF
Statistical Modification Analysis of Helical Planetary Gears based on Response Surface Method and Monte Carlo Simulation 被引量:15
18
作者 ZHANG Jun GUO Fan 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2015年第6期1194-1203,共10页
Tooth modification technique is widely used in gear industry to improve the meshing performance of gearings. However, few of the present studies on tooth modification considers the influence of inevitable random error... Tooth modification technique is widely used in gear industry to improve the meshing performance of gearings. However, few of the present studies on tooth modification considers the influence of inevitable random errors on gear modification effects. In order to investigate the uncertainties of tooth modification amount variations on system's dynamic behaviors of a helical planetary gears, an analytical dynamic model including tooth modification parameters is proposed to carry out a deterministic analysis on the dynamics of a helical planetary gear. The dynamic meshing forces as well as the dynamic transmission errors of the sun-planet 1 gear pair with and without tooth modifications are computed and compared to show the effectiveness of tooth modifications on gear dynamics enhancement. By using response surface method, a fitted regression model for the dynamic transmission error(DTE) fluctuations is established to quantify the relationship between modification amounts and DTE fluctuations. By shifting the inevitable random errors arousing from manufacturing and installing process to tooth modification amount variations, a statistical tooth modification model is developed and a methodology combining Monte Carlo simulation and response surface method is presented for uncertainty analysis of tooth modifications. The uncertainly analysis reveals that the system's dynamic behaviors do not obey the normal distribution rule even though the design variables are normally distributed. In addition, a deterministic modification amount will not definitely achieve an optimal result for both static and dynamic transmission error fluctuation reduction simultaneously. 展开更多
关键词 tooth modification helical planetary gears response surface method Monte Carlo simulation
下载PDF
Influences of the Helical Strake Cross-Section Shape on Vortex-Induced Vibrations Suppression for A Long Flexible Cylinder 被引量:10
19
作者 XU Wan-hai LUAN Ying-sen +1 位作者 LIU Li-qin WU Ying-xiang 《China Ocean Engineering》 SCIE EI CSCD 2017年第4期438-446,共9页
An experimental study on a bare flexible cylinder as well as cylinders fitted with two types of cross-sectioned helical strakes was carried out in a towing tank. The main purpose of this paper is to investigate the ef... An experimental study on a bare flexible cylinder as well as cylinders fitted with two types of cross-sectioned helical strakes was carried out in a towing tank. The main purpose of this paper is to investigate the effects of strakes’ cross-section on the vortex-induced vibrations (VIV) suppression of a flexible cylinder. The square-sectioned and round-sectioned helical strakes were selected in the experimental tests. The uniform current was generated by towing the cylinder models along the tank using a towing carriage. The Reynolds number was in the range of 800–16000. The strain responses were measured by the strain gages in cross-flow (CF) and in-line (IL) directions. A modal analysis method was adopted to obtain the displacement responses using the strain signals in different measurement positions. The comparison of the experimental results among the bare cylinder, square-sectioned straked cylinder and round-sectioned straked cylinder was performed. The helical strakes can effectively reduce the strain amplitude, displacement amplitude, response frequencies and dominant modes of a flexible cylinder excited by VIV. And the mean drag coefficients of straked cylinders were approximately consistent with each other. In addition, the square-sectioned and round-sectioned strakes nearly share the similar VIV reduction behaviors. Sometimes, the strakes with round-section represent more excellent effects on the VIV suppression of response frequency than those with square-section. 展开更多
关键词 helical strakes VIV suppression cross-section shape flexible cylinder
下载PDF
Clinical analysis of intracranial germinoma's craniospinal irradiation using helical tomotherapy 被引量:14
20
作者 Baolin Qu Lei Du +4 位作者 Yurong Huang Wei Yu Boning Cai Shouping Xu Lin Ma 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 2014年第3期247-254,共8页
Objective: To evaluate the short-term clinical outcomes of intracranial germinoma patients treated with craniospinal irradiation (CSI) using helical tomotherapy (HT) system in our center. Methods: Twenty-three p... Objective: To evaluate the short-term clinical outcomes of intracranial germinoma patients treated with craniospinal irradiation (CSI) using helical tomotherapy (HT) system in our center. Methods: Twenty-three patients who were treated with CSI in our center from January 2008 to July 2012 were collected, with an average age of 20. M1 of the patients' CSI used the HT system. The total doses were 27-36 Gy/15-20 F (1.5-2 Gy per fraction), and total local doses were 46-60 Gy/30-50 F (5 fractions per week). M1 female patients for CSI were treated with left-right parallel-opposed field irradiation to protect their ovarian functions. Median follow-up time was 30.9 months (range, 5-67 months). The SPSS19.0 software was used, and the overall survival (OS) was calculated using the Kaplan-Meier method. Results: Among 17 patients with assessable tumors, 9 cases (52.9%) were CR, 7 cases (41.2%) were PR, and 1 case (5.9%) was SD. Hematological toxicity was the severest side-effect occurred in the procedure of CSI. The level 1-4 acute leukopenia were 8.7%, 30.4%, 34.8% and 21.7% and the level 1-4 acute thrombopenia were 8.7%, 30.4%, 21.7% and 8.7%, respectively. Conclusions: For primary intracranial germinomas, HT can be used to implement CSI for simplifying radiotherapy procedures, improving radiotherapy accuracy, enhancing protection of peripheral organs at risk (ORA) and guaranteeing therapeutic effects. With the acceptable acute and long-term toxicity, CSI using HT in intracranial germinoma patients can be a safe and alternative mode. 展开更多
关键词 Germinomas craniospinal irradiation (CSI) helical tomotherapy (HT)
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部