期刊文献+
共找到166,866篇文章
< 1 2 250 >
每页显示 20 50 100
Study of the Interception Scheme Based on A* Path Finding Algorithm in Computer Game 认领
1
作者 Haiming Li 《电脑和通信(英文)》 2020年第7期32-49,共18页
In the game, we generally use A* algorithm for pathfinding according to the target location and map information to realize the tracking and interception task. This approach is simple to implement, but is often less th... In the game, we generally use A* algorithm for pathfinding according to the target location and map information to realize the tracking and interception task. This approach is simple to implement, but is often less than ideal in its presentation, because it does not allow game units to predictably choose paths based on dynamic targets or obstacles, and may lead to blocked channels or difficulty in choosing the actual optimal path. This paper focuses on analyzing the need of a unit when intercepting another unit in the game, and make an interception scheme which can adapt itself to dynamic obstacles and moving target thus presents artificial intelligence to some extent. 展开更多
关键词 Interception Path A* Algorithm Dynamic Obstacles Dynamic A* Algorithm
在线阅读 免费下载
An Efficient Non-Linear Application Algorithm Predictive Model for a Multi Aircraft Landing Dynamic System <i>AIRLADYS R</i>2019<i>A</i><sup>+</sup> 认领
2
作者 Fulgence Nahayo Salah Khardi 《最优化(英文)》 2020年第2期15-26,共12页
The aim of this paper is to set up an efficient nonlinear application algorithm predictive model for a multi aircraft landing dynamic system called “Aircraft Landing Dynamic System, Release 2019<em>A</em>... The aim of this paper is to set up an efficient nonlinear application algorithm predictive model for a multi aircraft landing dynamic system called “Aircraft Landing Dynamic System, Release 2019<em>A</em><sup>+</sup> version “<em>AIRLADYS R</em>2019<em>A</em><sup>+</sup>”. This programming software combines dynamic programming technic for mathematical computing and optimisation run under AMPL and KNITRO Solver. It uses also a descriptive programming technic for software design. The user interfaces designed in Glade are saved as XML, and by using the GtkBuilder GTK+ object these can be loaded by applications dynamically as needed. By using GtkBuilder, Glade XML files can be used in numerous programming languages including C, C++, C#, Java, Perl, Python, AMPL, etc. Glade is Free Software released under the GNU GPL License. By these tools, the solved problem is a mathematical modelization problem as a non-convex optimal control governed by ordinary non-linear differential equations. The dynamic programming technic is applied because it is a sufficiently high order and it does not require computation of the partial derivatives of the aircraft dynamic. This application will be coded with Linux system on 64 bit operating system, but it can also be run on the windows system. High running performances are obtained with results giving feasible trajectories with a robust optimizing of the objective function. 展开更多
关键词 Glade Software Aircraft Dynamic System Optimal Control System Dynamic Programming GUI GPL Application AIRLADYS R2019A+
在线阅读 免费下载
Low embankment dynamic response under vehicle traffic loads in arid-oasis areas 认领
3
作者 WAN Qi YANG Xiao-hua +1 位作者 YIN Pei-jie BAO Han 《山地科学学报:英文版》 SCIE CSCD 2020年第7期1776-1789,共14页
The use of low embankments is of significant concern for ecological protection in aridoasis areas.Based on the project of Sansha Expressway located in Kashgar City,Xinjiang,China,physical model tests were conducted in... The use of low embankments is of significant concern for ecological protection in aridoasis areas.Based on the project of Sansha Expressway located in Kashgar City,Xinjiang,China,physical model tests were conducted in this study to investigate the dynamic response of the low embankment as per the effects of road structure,load amplitude,load frequency,load cycle,and moisture content.The dynamic stress is shown to increase with load amplitude while the dynamic elastic modulus decreases with load amplitude under short-term loading.The load frequency slightly influences the soil’s dynamic behavior;higher frequencies can improve the dynamic elastic modulus of the subgrade soil.The moisture content has greater influence on the mechanical properties of the subsoil than that of subgrade layer.The subgrade bears the majority of the traffic load as the stress dissipates to 37%of the whole value on its surface.The number of load cycles has the greatest effect on the dynamic response among the influencing factors tested.The dynamic elastic modulus with the type of long-term dynamic loading is only 40%-52%of that with static loading across the entire depth range.The dynamic stress shows significant accumulation with load cycles over the long-term dynamic loading test and becomes stable after 8×10~4 cycles of loading.An equation is established to quantify the cumulative dynamic stress in the low embankment under long-term dynamic loading conditions. 展开更多
关键词 Low embankment Dynamic response Model test Moisture content Dynamic elastic modulus Cumulative dynamic stress
Study at Two Dimensions of Thermal Transfer through a Fibers Panel Subjected to Climatic Constraints in Dynamic Frequency Regulations Established 认领
4
作者 Mohamed Sidya Ould Brahim Issa Diagne +7 位作者 Mamadou Babacar Ndiaye Youssou Traore Seydou Faye Cheikh Thiam Pape Touty Traore Ablaye Fame Sokhna Khadidiatou Ben Thiam Gregoire Sissoko 《能源与动力工程(英文)》 2020年第5期135-142,共8页
From resolution of two-dimensional equation of heat in dynamic frequency regime, we have plotted evolution curves of temperature according to depth of material or in lateral direction. They will allow us to evaluate t... From resolution of two-dimensional equation of heat in dynamic frequency regime, we have plotted evolution curves of temperature according to depth of material or in lateral direction. They will allow us to evaluate thermal behavior of towed material. Aim of study is to use fibers as a thermal insulating material by proposing a method for determining effective thermal insulation layer in dynamic frequency regime. 展开更多
关键词 Thermal Transfer Heat Exchange COEFFICIENT Frequency Dynamic REGIME Fibers
在线阅读 免费下载
串联机构质量配置方法研究 认领
5
作者 苏芳 王晨升 +1 位作者 梁宝英 赵聪 《制造技术与机床》 北大核心 2020年第8期53-57,共5页
为实现串联机械结构质量的优化配置,以三自由度系统为例开展串联机构质量分配方法研究。首先,建立了系统动力学模型,在保持刚度条件不变的情况下,考察不同质量分配结果对系统首阶固有频率的影响。然后,以此系统为研究对象,基于敏感性分... 为实现串联机械结构质量的优化配置,以三自由度系统为例开展串联机构质量分配方法研究。首先,建立了系统动力学模型,在保持刚度条件不变的情况下,考察不同质量分配结果对系统首阶固有频率的影响。然后,以此系统为研究对象,基于敏感性分析和直线拟合方法,开展系统质量块质量对系统动刚度和末端执行器运动精度的影响规律研究。最后,在此基础上,分别提出基于系统总质量上限和系统首阶固有频率下限的两种质量优化配置方法。结果显示,系统质量块质量与系统动态特性紧密相关,系统总质量比与系统动刚度成正比关系,该比值可用于串联机构设计初始阶段的质量分配和设计后期的轻量化,亦可作为串联机构结构件质量分配合理性和动态特性的评价指标。 展开更多
关键词 串联机构 质量分配 动力学 质量比 动刚度
在线阅读 下载PDF
Temperature Effect on Light Concentration Silicon Solar Cell’s Operating Point and Conversion Efficiency 认领
6
作者 Dieudonné Joseph Bathiebo 《智能电网与可再生能源(英文)》 2020年第5期61-72,共12页
It is well known that temperature acts negatively on practically all the parameters of photovoltaic solar cells. Also, the solar cells which are subjected to particularly very high temperatures are the light concentra... It is well known that temperature acts negatively on practically all the parameters of photovoltaic solar cells. Also, the solar cells which are subjected to particularly very high temperatures are the light concentration solar cells and are used in light concentration photovoltaic systems (<i><span style='font-family:Verdana;'>CPV</span></i><span style='font-family:Verdana;'>). In fact, the significant heating of these solar cells is due to the concentration of the solar flux which arrives on them. Light concentration solar cells appear as solar cells under strong influences of heating and temperature. It is therefore necessary to take into account temperature effect on light concentration solar cells performances in order to obtain realistic results. </span><span style='font-family:''><span style='font-family:Verdana;'>This one-dimensional study of a crystalline silicon solar cell under light concentration takes into account electrons concentration gradient electric field in the determination of the continuity equation of minority carriers in the base. To determine excess minority carrier’s density, the effects of temperature on the diffusion and mobility of electrons and holes, on the intrinsic concentration of electrons, on carrier’s generation rate as well as on width of band gap have also been taken into account. The results show that an increase of temperature improves diffusion parameters and leads to an increase of the short-circuit photocurrent density. However, an increase of temperature leads to a significant decrease in open-circuit photovoltage, maximum electric power and conversion efficiency. The results also show that the operating point and the maximum power point (</span><i><span style='font-family:Verdana;'>MPP</span></i><span style='font-family:Verdana;'>) moves to the open circuit when the cell temperature increases.</span></span> 展开更多
关键词 TEMPERATURE Electric Power Conversion Efficiency Light Concentration Maximum Power Point Junction Dynamic Velocity
在线阅读 免费下载
Nuclear Energy and Its History: Past Consequences, Present Inadequacies and a Perspective for Success 认领
7
作者 Romney B. Duffey Francesco D’Auria 《能源与动力工程(英文)》 2020年第6期193-236,共44页
An attempt is made to locate nuclear technology within a logical context considering history, risks, societal catastrophes and perspectives: the need is identified for a new direction in the exploitation in order to r... An attempt is made to locate nuclear technology within a logical context considering history, risks, societal catastrophes and perspectives: the need is identified for a new direction in the exploitation in order to restore the role in energy production. We depict the situation coming from a marvelous history of discoveries started at the beginning of the XX century;heroes are recalled who made possible something that is inconceivable today: design, construction and production of electricity in a few years;that history was tainted by intentional nuclear explosions, </span><i><span style="font-size:12px;font-family:Verdana;">i.e.</span></i><span style="font-size:12px;font-family:Verdana;"> the original sin that we are now paying. Then, we attempt to show that the societal risk is an inherent part of the civilization. Restoring the public trust (towards nuclear fission technology) by matching nuclear safety with the current technological status and advancers in risk assessment is the key objective. The </span></span><span style="font-family:Verdana;font-size:12px;">“</span><span style="font-family:Verdana;font-size:12px;">independent assessment</span><span style="font-family:Verdana;font-size:12px;">”</span><span style="font-family:Verdana;font-size:12px;">, or a principle for the exploitation of nuclear energy already stated in the 50’s of the previous century, shall then re-appear. This is used to erect the signpost for a </span><span style="font-family:Verdana;font-size:12px;">“</span><span style="font-family:Verdana;font-size:12px;">dynamic barricade</span><span style="font-family:Verdana;font-size:12px;">”</span><span style="font-family:Verdana;font-size:12px;"> to further reduce the risk of operation of nuclear reactors and to match the design with current technological capabilities and with the frontiers of the research. 展开更多
关键词 Societal Risk Risk and Probability CATASTROPHES Nuclear Fission Nuclear Reactor Technology Dynamic Barricade Cost of Safety
在线阅读 免费下载
Dynamic Modelling of Submersible Pump Based Solar Water-Pumping System with Three-Phase Induction Motor Using MATLAB 认领
8
作者 Faisal Alkarrami Tariq Iqbal +1 位作者 Kevin Pope Geoff Rideout 《电力能源(英文)》 2020年第2期20-64,共45页
The main purpose of this paper is to design and model a water-pumping system using a submersible multi-stage centrifugal pump driven by a three-phase induction motor. The system is intended for pumping water to the su... The main purpose of this paper is to design and model a water-pumping system using a submersible multi-stage centrifugal pump driven by a three-phase induction motor. The system is intended for pumping water to the surface from a deep well using three power supply systems: a general network, a photo-voltaic (PV) system, and a PV system with a battery bank. These systems are used to compare two three-phase induction motors—namely, a motor with a drive and another one without a drive. The systems dynamic models are simulated in MATLAB/Simulink and the results compared with the manufacturer’s data for validation purposes. The simulation results generally show system dynamics and expected performance over a range of operation. 展开更多
关键词 Dynamic Modeling Induction Motor WATER PUMPING SYSTEM SUBMERSIBLE PUMP PV SYSTEM Battery BANK MATLAB/Simulink
在线阅读 免费下载
Pediatric Application of Dynamic Contrast-Enhanced MR Imaging (DCE-MR) in the Management of Extra-Cranial Tumor: Experience in Routine Clinical Practice 认领
9
作者 Wendy Wai-Man Lam Daniel Cheuk Godfrey Chi-Fung Chan 《放射学期刊(英文)》 2020年第2期57-68,共12页
<strong>Background: </strong>Dynamic contrast-enhanced MR imaging (DCE-MR) is becoming a widely accepted complementary method for diagnosing breast cancer and other cancers in adults. It is useful to predi... <strong>Background: </strong>Dynamic contrast-enhanced MR imaging (DCE-MR) is becoming a widely accepted complementary method for diagnosing breast cancer and other cancers in adults. It is useful to predict tumor response to anticancer therapy and monitor the tumor response to the therapy. This form of imaging techniques has not been adequately explored in pediatric oncology patients. <strong>Objective:</strong> To determine the potential role of dynamic contrast-enhanced MR imaging (DCE-MR) in the diagnosis and treatment response monitoring of childhood and young adult extra-cranial tumors in routine clinical setting.<strong> Methods:</strong> Children with suspected extra-cranial solid tumors, including newly diagnosed or follow-up cases of confirmed tumors, were recruited. DCE-MR was performed with intravenous injection of 0.1 mmol/kg contrast. The enhancement time curves were plotted and the enhancement patterns were categorized into type 1, 2 and 3 curves. Enhancement curve patterns and maximal enhancement intensity were compared with types of tumor in newly diagnosed cases. The preoperative percentiles of inactive area on the colour map were compared with the necrotic areas on histologic sections of the resected specimens in follow-up cases. Pearson Chi-square test and Unpaired two-sample t-test were used for statistical analysis. <strong>Results: </strong>There were 36 patients, involving 28 malignant and 8 benign cases. There were 14 type 3 curves, (all of them were malignant tumors), 6 type 2 curves and 16 type 1 curves. All the benign cases (n = 8) demonstrated type 1 curve (accuracy & negative predictive value = 100%). All the malignant cases after treatment showed type 2 or 1 curve. For those cases with operation done afterwards, the extent of tumor necrosis was correlated closely with pathology findings (accuracy = 93.3%). <strong>Conclusion:</strong> Type 1 curve was a good predictor of benign lesion. DEC-MR may have a role to play in the monitoring of the progress of treatment and extent of tumor 展开更多
关键词 MR DCE-MR Dynamic Contrast MR TUMOR Children PEDIATRIC
在线阅读 免费下载
二维冲箱式造波机的间隙和形状效应数值研究 认领
10
作者 Amir H.Nikseresht Harry B.Bingham 《船舶与海洋工程学报:英文版》 CSCD 2020年第1期101-115,共15页
The installation of plunger-type wave makers in experimental tanks will generally include a gap between the back of the wedge and the wall of the tank.In this study,we analyze the influence of this gap on the wave mak... The installation of plunger-type wave makers in experimental tanks will generally include a gap between the back of the wedge and the wall of the tank.In this study,we analyze the influence of this gap on the wave making performance of the plunger using two-dimensional(2 D)CFD calculations for a range of nearly linear wave conditions and compare the results with both experimental measurements and linear potential flow theory.Three wedge-shaped profiles,all with the same submerged volume,are considered.Moreover,the generated waves are compared with the predictions of linear potential flow theory.The calculations are made using the commercial ANSYS FLUENT finite-volume code with dynamic meshes to solve the Navier-Stokes equations and the volume of fluid scheme to capture the air-water interface.Furthermore,the linear potential flow solution of Wu(J Hydraul Res 26:481-493,1988)is extended to consider an arbitrary profile and serve as a reference solution.The amplitude ratios of the generated waves predicted by the CFD calculations compare well with the predictions of linear potential flow theory for a simple wedge,indicating that viscous effects do not influence this ratio for small-amplitude motions in 2 D.By contrast,significant higher harmonic components are produced by larger amplitude motions.Also,the simple wedge is found to produce the smallest spurious higher harmonic content in the far-field wave. 展开更多
关键词 Wave maker Plunger-type Berkeley wedge Hyperbolic sine profile Gap Dynamic mesh Volume of fluid
在线阅读 下载PDF
Fixed Time Control of Dynamic Positioning Ship with Unknown Interference 认领
11
作者 Peng Xu 《应用科学(英文)》 2020年第5期246-257,共12页
This paper proposes a fixed-time control scheme to ensure that the dynamic positioning can accurately reach the specified position under external interference. A fixed-time state observer was developed to accurately e... This paper proposes a fixed-time control scheme to ensure that the dynamic positioning can accurately reach the specified position under external interference. A fixed-time state observer was developed to accurately estimate the total external unknown interference. Based on the dynamic positioning ship motion model, the inversion design method is used to ensure the stability of the system and eliminate various uncertain effects. A fixed-time backstepping sliding mode controller is designed. Finally, the simulation results show that the method has good performance and advantages. 展开更多
关键词 Dynamic POSITIONING Fixed-Time OBSERVER SLIDING Mode CONTROL
在线阅读 免费下载
Microstructure and mechanical properties of Mg-4Zn-xGd(x=0,0.5,1,2)alloys 认领
12
作者 Cui-ju Wang Jin-wen Kang +3 位作者 Kun-kun Deng Kai-bo Nie Wei Liang Wei-guo Li 《镁合金学报(英文)》 SCIE 2020年第2期441-451,共11页
The present work inainly focuses on tlie effect of minor cofiteut of Gd cicmcnt on the micrGstmcturc and mechanical properties of Mg Zn alloy.The Mg-4Zn-xGd(x=0,0.5,1,2)alloys were fabricated and subjected to extrusio... The present work inainly focuses on tlie effect of minor cofiteut of Gd cicmcnt on the micrGstmcturc and mechanical properties of Mg Zn alloy.The Mg-4Zn-xGd(x=0,0.5,1,2)alloys were fabricated and subjected to extrusion at 280℃ with the ratio of 25:1.Results revealed that the addition of Gd could inhibit the dynamic recrystallization(DRX)of Mg-4Zn alloy,and both the size and volume fraction of DRXed grains demonstrated a decreasing tendency as the Gd content increased from 0.5 to 2 wt.%.It is the weakening effect on DRX behavior that lead to the smaller amount of fine precipitate and the stronger texture intensity.As compared with the Mg-4Zn alloy,the yield strength and ultimate tensile strength of Mg-4Zn-xGd alloys were improved obviously by the addition of minor content of Gd,however,at the expense of elongation.Excellent tensile properties with the yield strength of〜369.8 MPa and ultimate tensile strength of〜400.3 MPa were obtained when the Gd content was 2 wt.%. 展开更多
关键词 Magnesium alloy Dynamic recrystallization Dynamic precipitation MICROSTRUCTURE Mechanical properties
在线阅读 下载PDF
“21世纪海上丝绸之路”沿线国家商业银行全要素生产率评价研究——基于两阶段Dynamic Network Malmquist-Luenberger指数和Tobit模型 认领 被引量:1
13
作者 谭涛 吴江 +1 位作者 王旻轲 张培文 《数理统计与管理》 CSSCI 北大核心 2020年第2期289-307,共19页
现有文献对商业银行的全要素生产率进行了大量研究,但未同时考虑中间产品和结转产品对整个经营过程的影响,得到的测算结果存在一定的偏差。本文使用"21世纪海上丝绸之路"沿线29个国家2011-2016年的商业银行数据,将商业银行的... 现有文献对商业银行的全要素生产率进行了大量研究,但未同时考虑中间产品和结转产品对整个经营过程的影响,得到的测算结果存在一定的偏差。本文使用"21世纪海上丝绸之路"沿线29个国家2011-2016年的商业银行数据,将商业银行的经营过程看成是一个两阶段的动态网络结构,采用动态网络方向距离函数构造了一种新的动态网络Malmquist-Luenberger指数研究商业银行整体和子阶段的全要素生产率变化,并进行了影响因素分析和β收敛检验。得到的结论有:(1)"21世纪海上丝绸之路"沿线国家商业银行整体全要素生产率年均下降0.61%,呈现N型趋势,两个子阶段的全要素生产率年均下降0.06%,呈现V型趋势,技术进步是整体和子阶段全要素生产率增长的主要动力。(2)四个地区和四种收入类型国家整体的全要素生产率都是下降的,各子阶段全要素生产率变化有所差异。(3)人均GDP水平、信贷市场结构、外商投资、银行经营年限、银行规模、银行资产配置等因素会对全要素生产率产生影响。(4)"21世纪海上丝绸之路"沿线国家商业银行整体和子阶段的全要素生产率都存在绝对β收敛和条件β收敛,不同地区和不同收入类型国家的收敛特征不尽相同。 展开更多
关键词 21世纪海上丝绸之路 Dynamic Network Malmquist-Luenberger指数 两阶段DEA 全要素生产率 TOBIT模型
Analysis of Vibration of the Euler-Bernoulli Pipe Conveying Fluid by Dynamic Stiffness Method and Transfer Matrix 认领
14
作者 Yunfeng Li Yundong Li Naveed Akbar 《应用数学与应用物理(英文)》 2020年第1期172-183,共12页
The dynamic stiffness method and Transfer method is applied to study the vibration characteristics of the Euler-Bernoulli pipe conveying fluid in this paper. According to the dynamics equation of the pipe conveying fl... The dynamic stiffness method and Transfer method is applied to study the vibration characteristics of the Euler-Bernoulli pipe conveying fluid in this paper. According to the dynamics equation of the pipe conveying fluid, the element dynamic stiffness is established. The vibration characteristic of the single-span pipe is analyzed under two kinds of boundary conditions. The results compared with the literature, which has a good consistency. Based on this method, natural frequency and the critical speed of the two types of multi-span pipe are deserved. This paper shows that the dynamic stiffness method and transfer matrix is an effective method to deal with the vibration problem of pipe conveying fluid. 展开更多
关键词 DYNAMIC STIFFNESS Transfer Matrix Euler-Bernoulli Pipe
在线阅读 免费下载
Risk Evaluation Based on Variable Fuzzy Sets and Information Diffusion Method 认领
15
作者 W. Gong K. Chen +1 位作者 T. J. Huggins L. Yang 《应用数学与应用物理(英文)》 2020年第5期821-830,共10页
Risk evaluation is an effective way to reduce the impacts of natural hazards and it plays an increasingly important role in emergency management. Traditional methods of assessing risks mainly utilize Geographic Inform... Risk evaluation is an effective way to reduce the impacts of natural hazards and it plays an increasingly important role in emergency management. Traditional methods of assessing risks mainly utilize Geographic Information System (GIS) to get risk map, and information diffusion method (IDM) to deal with incomplete data sets. However, there are few papers discuss the uncertainty of integrated hazards and consider dynamic risk under time dimension. The model proposed in this study combines the variable fuzzy set theory with information diffusion method (VFS-IDM) to solve the uncertainness of multiple hazards dynamic risk assessment when data sets are incomplete. This study employs fuzzy set theory (VFS) to calculate the relative membership degree and applies information entropy method (IEM) to obtain the weights of criteria indicators for multiple hazards evaluation. Then applies information diffusion method (IDM) to estimate condition probability distribution and vulnerability curve with the VFS-IEM model results, time data and multiple hazards losses. Then the expected value of multiple hazards dynamic risk can be calculated by using the normal information diffusion estimator so as to improve the accuracy of risk evaluation results. 展开更多
关键词 RISK Evaluation INTEGRATED RISK DYNAMIC RISK FUZZY SETS VFS-IDM
在线阅读 免费下载
Climate Change Assessment Using Negative Extreme Deviations of Surface Temperature Field (Case Study: Tbilisi) 认领
16
作者 Kukuri Tavartkiladze Nana Bolashvili +2 位作者 Maia Ananidze Nikoloz Suknidze Giorgi Chartolani 《地质学期刊(英文)》 2020年第5期491-500,共10页
To conduct regional climate change assessment for the selected location (Tbilisi) more than century period hydrometeorological observation data of day-night minimal temperature is used. In the presented paper only tem... To conduct regional climate change assessment for the selected location (Tbilisi) more than century period hydrometeorological observation data of day-night minimal temperature is used. In the presented paper only temperature negative values of whole winter season are used. The temperature field change is characterized by the following four parameters: the minimal temperature sum (winter-day temperature is less than zero) of winter frost days;frost day number;season minimal temperature and the occurrence date of season minimal temperature. The modular structure of the above listed parameters has been studied and the mathematical expressions for temporal changes of those parameters have been obtained considering dynamical norms and cyclical changes. The intensity of this change in terms of global warming has been determined. One of the main parameters determining climate change is the variations of temperature field. Despite the fact that this parameter has been modified in the large range due to numerous impacts, they kept stable and provide sustainable equilibrium of the Earth’s energy potential during long-term (several decades) period. This was the reason why the Earth climate remained unchained. As it is known, the anthropogenic impact on the environment has breached the sustainable balance of the Earth energy potential, the potential has been gradually grown almost for more than a century and is known by the name of global warming. The above-mentioned process has already created the greatest threat to the existence of Earth’s biosphere and if it still continues the catastrophic results eventually have to be expected. This led that the problem solving has been set as an urgent task. The numerous fundamental studies for all regions of the world have been carried out to assess the intensity of this process. 展开更多
关键词 Climate Change Dynamic NORM NEGATIVE EXTREME DEVIATIONS SURFACE Temperature
在线阅读 免费下载
Influence of blade negative twist on aerodynamic performance of cycloidal propeller 认领
17
作者 ZENG Jianan ZHU Qinghua +2 位作者 WANG Kun SHEN Suiyuan ZHU Zhenhua 《航空动力学报》 EI CAS CSCD 北大核心 2020年第3期620-632,共13页
In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller,a set of CFD methods suitable for the simulation of the cycloidal propeller flow fie... In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller,a set of CFD methods suitable for the simulation of the cycloidal propeller flow field based on the dynamic overset mesh and Unsteady Reynolds time average method equation were established.The characteristics of the spanwise lift distribution and surface pressure distribution in case of different negative twist were provided.The influence of the negative twist on the aerodynamic performance of cycloidal propeller was emphasized.The results showed that,the change of negative twist caused the change of azimuth for cycloidal propeller lift.The larger the absolute value of negative twist,the lower the figure of merit of the cycloidal propeller;the smaller the negative twist,the more gentle the instantaneous aerodynamic fluctuation;the influence mechanism of negative twist on the aerodynamic performance of cycloidal propeller was generated from changing the non-uniform distribution of the cycloidal propeller’s effective angle of attack. 展开更多
关键词 cycloidal PROPELLER figure of MERIT NEGATIVE TWIST DYNAMIC overset mesh DYNAMIC STALL
Verification of Tire Hydroplaning Phenomenon Using Coupled FSI Simulation by CFD and FEM 认领
18
作者 Hyun Chul Jung Mi Dum Jung +1 位作者 Kyoung Moon Jeong Kyunghoon Lee 《应用科学(英文)》 2020年第7期417-431,共15页
<span style="font-family:Verdana;">Hydroplaning phenomenon is one of the major factors that must be considered to ensure safe driving on wet road surfaces. In this paper, the approach to numerical simu... <span style="font-family:Verdana;">Hydroplaning phenomenon is one of the major factors that must be considered to ensure safe driving on wet road surfaces. In this paper, the approach to numerical simulation of the physical hydroplaning characteristics using patterned tire is described. A detailed 3-D patterned tire model is constructed by in-house modeling program and the water flow is considered as incompressible. The complex tire material compositions are effectively modeled using composites, and rubber properties generalize the Mooney-Rivlin model. The finite element method (FEM) and the advanced finite volume method (FVM) are used for structural and for fluid-tire interaction analysis, respectively. Performance prediction of hydroplaning via coupling of computational fluid dynamics (CFD) and FEM has delivered a detailed insight into the local mechanisms and root causes of hydroplaning. Numerical examples were verified by comparing the experimental test results and it is confirmed to indicate similar correlation tendency and high reliability. The effect of driving velocity, pattern groove size, and pattern direction on hydroplaning phenomenon of tire is discussed and logical results were obtained.</span> 展开更多
关键词 TIRE HYDROPLANING Finite Element Method Computational Fluid Dynamic Fluid Structure Interaction
在线阅读 免费下载
Structural Behavior of Long Span Overhead Sign Support Bridges 认领
19
作者 Ishtiaque Ahmed Tuhin 《土木工程期刊(英文)》 2020年第1期1-8,共8页
Overhead sign-support bridges that allow displaying necessary information for travelers across the multiple lanes in highways often use large message sign panels: static message sign (SMS) panels or dynamic message si... Overhead sign-support bridges that allow displaying necessary information for travelers across the multiple lanes in highways often use large message sign panels: static message sign (SMS) panels or dynamic message sign (DMS) panels. Along with conventional SMS panel, the use of DMS panel is increasing in highways over time owing to their effective capability to guide the travelers in real-time. A 230-ft long span 4-chord overhead steel truss bridge attached with SMS and DMS panel has been studied through extensive finite element analysis to observe the structural integrity. The static wind load was applied in model truss for four different configurations as per 2016 AASHTO LRFD design specification. The innovative structural detailing approach for truss end support and connection detailing for toll-equipment supporting frame was proposed based on static analysis. The present study will help engineers to design overhead sign support bridges by ensuring both public safety and structural integrity. 展开更多
关键词 Sign-Support Bridge Static MESSAGE SIGN (SMS) Dynamic MESSAGE SIGN (DMS) Finite Element Analysis Wind Load
在线阅读 免费下载
Model-free adaptive optimal design for trajectory tracking control of rocket-powered vehicle 认领
20
作者 Wenming NIE Huifeng LI Ran ZHANG 《中国航空学报:英文版》 SCIE EI CAS CSCD 2020年第6期1703-1716,共14页
An adaptive optimal trajectory tracking controller is presented for the Solid-RocketPowered Vehicle(SRPV)with uncertain nonlinear non-affine dynamics in the framework of adaptive dynamic programming.First,considering ... An adaptive optimal trajectory tracking controller is presented for the Solid-RocketPowered Vehicle(SRPV)with uncertain nonlinear non-affine dynamics in the framework of adaptive dynamic programming.First,considering that the ascent model of the SRPV is non-affine,a model-free Single Network Adaptive Critic(SNAC)method is developed based on the dynamic neural network and the traditional SNAC method.This developed model-free SNAC method overcomes the limitation of the traditional SNAC method that can only be applied to affine systems.Then,a closed-form adaptive optimal controller is designed for the non-affine dynamics of SRPVs.This controller can adjust its parameters under different flight conditions and converge to the approximate optimal controller through online self-learning.Finally,the convergence to the approximate optimal controller is proved.The theoretical analysis of the uniformly ultimate boundedness of the tracking error is also presented.Simulation results demonstrate the effectiveness of the proposed controller. 展开更多
关键词 Adaptive dynamic program­ming Dynamic neural network MODEL-FREE Solid-rocket-powered vehi­cle Trajectory tracking
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈