甲板上牵引车-直升机系统的稳定性控制

探讨了甲板上牵引车牵引直升机行驶时,通过主动控制牵引车后轮转向角来提高直升机牵引系统操纵稳定性的基本原理.考虑船体横摇、纵摇和垂荡3个自由度的耦合运动对牵引系统产生的惯性力,建立了包含转向子系统模型在内的3自由度时变、非线性牵引车 直升机系统动力学模型.针对直升机参数和海洋环境的不确定性,结合转向子系统特性,应用扩展后的反演变结构控制方法设计了牵引车后轮主动转向+前轮补偿转向控制器.仿真结果表明,变结构控制器在有效控制牵引车和直升机之间相对横摆角速度的同时,很好地跟随了理想模型,增强了牵引系统的操作性;并且控制系统能够很好地克服参数摄动和不确定的外界干扰对系统稳定性的影响.     

多轴特种车辆缺胎行驶动力学特性研究

为了探究多轴特种车辆在轮胎损失极限工况下的行驶特性，基于TruckSim车辆动力学软件，建立包括整车参数、动力传动与制动系统、车桥与悬挂系统、转向系统和轮胎系统的五轴特种车辆动力学仿真试验模型，通过对仿真模型进行调整和改进，建立符合实车驱动的特种车辆动力学模型.为重点分析轮胎缺失状态的影响，以轮胎六分力试验为基础，选取TruckSim中性能相似的非线性轮胎模型进行修改，通过进行0～80～0 km/h直线加速制动平顺性仿真试验和双移线操稳性仿真试验，研究不同位置处轮胎缺失状态下的车辆平顺特性和操稳特性.同时，以车辆质心偏移量为标准，分析讨论不同行驶速度下的最大缺失轮胎数量，提出不同行驶速度下缺胎工况的轮胎布置方法以及各桥轮胎对车辆行驶影响的程度级别.研究结果表明：多轴特种车辆具备在缺胎工况下行驶的极限条件，不同位置处轮胎缺失对车辆的最大行驶速度影响不显著；该型车辆各桥轮胎对车辆行驶影响的重要程度依次为一桥、五桥、三桥、二桥和四桥；车辆分别以50、30和20 km/h速度行驶时，最大缺失轮胎数量分别为1、2和3个.研究结论为多轴特种车辆行驶安全性评估提供了理论支撑.     

浮吊海上补给作业的动态特性仿真分析与研究

浮吊在进行海上补给时,吊重绳索的下降、摆动以及船体的受迫运动,使吊重下降时很容易碰撞甲板,引发重大事故。考虑吊点处的弹性力,建立了浮吊吊物系统的动力学方程。在MATLAB平台上采用数值分析的方法,分别对吊重静止时和作业时的动态特性进行研究。结果表明绳长、海况、下降速度等对补给安全有重要影响。计算得出的吊重下降速度和位移规律,可为波浪补偿系统提供重要依据。     

基于车辆动态负载的开关磁阻电机驱动特性分析

为了研究车辆动态负载高度时变性和随机性对电动汽车用开关磁阻电机驱动系统影响特性并实现电机驱动系统性能评价分析,基于车辆行驶工况动态负载特性,在开关磁阻电机非线性数学模型及车辆动力学模型基础上,分别建立了电动汽车用开关磁阻电机驱动系统及电动汽车动态载荷仿真模型.并根据电动汽车行驶过程中2个典型工况对建立模型进行了实时仿真,得到了开关磁阻电机主要性能参数随车辆动态载荷变化的响应曲线.分析并评价了开关磁阻电机驱动系统在各工况下的动态驱动特性,仿真结果对电动汽车车型设计及改进具有很好的参考价值.     

舰载机无杆式牵引车横摆稳定性控制

对舰载机无杆式牵引车的横摆稳定性控制进行深入的研究分析.考虑舰船横摇、纵摇和垂荡的耦合运动影响,建立轮毂电机驱动的舰载机无杆式牵引车时变非线性动力学模型.分别基于滑模变结构和自适应模糊比例积分微分(PID)控制理论获得横摆稳定性控制所需的补偿力矩,从而实现对理想参考模型的横摆角速度值的跟随.应用MATLAB/Simulink平台对两种控制方法进行仿真对比验证.仿真结果显示,所建立的动力学模型能够很好地反映舰载机牵引车的横摆运动特性.基于准滑动模态的滑模控制方法能够很好地控制牵引车的横摆角速度对理想模型的跟随,实现了对牵引车的稳定控制.在5级及以下海况的干扰下,能够保证系统响应迅速、稳健性高,有效地提高了舰载机无杆式牵引车的行驶稳定性.     

船坞牵引(定位)小车-缆绳-船舶系统动力响应分析

船坞引船系统作为船坞的重要组成部分,其性能直接关系到船舶能够安全进出船坞。基于MMG模型理论,构建了船坞牵引(定位)小车-缆绳-船舶系统的动力学方程。通过数值计算,模拟了船舶在不利海况条件下进坞运动过程的动态响应,以及缆绳张力的变化情况。重点研究探讨了牵引缆绳长度、牵引绞车启动加速时间以及牵引速度等因素对牵引缆绳受力的影响。仿真结果表明,牵引缆绳张力作为船坞引船系统的主要外载荷,一方面为船舶进坞运动提供动力;另一方面为限制船舶横向位移提供主要作用。适当加长缆绳长度、延长绞车启动加速时间以及降低绞车牵引速度,可显著改善引船系统所受载荷情况。     

自动化弹库交流伺服系统研究

舰炮自动化弹库在转运过程中,要求伺服系统具有较高的转运效率和较高的位置跟踪精度,并在5级海况的干扰下仍然能够正常工作.基于上述条件,该文首先分析了在5级海况下,电机轴负载力矩的变化情况.并运用矢量控制的方法,建立自动化弹库三闭环结构的永磁同步电机伺服系统模型.位置环采用模糊自适应PI控制器,提高系统快速性,提高弹库的转运效率;并设计负载观测器,在速度环采用前馈控制,达到抗海况干扰的作用.利用MATLAB/Simulink进行了系统仿真,仿真结果表明:该方法提高了自动化弹库伺服系统的快速性,能够较好地抑制海况导致的负载扰动.     

调速阀出口节流调速系统动态特性仿真研究

为获得节流调速系统在不同工作条件下的动态特性,在MATLAB/Simulink环境下建立调速阀出口节流调速系统的仿真模型,分析不同开口面积和不同外负载对系统启动及速度切换时动态特性的影响,得出如下结论:(1)在不同开口面积和外负载工况下启动时,液压缸均会有不同程度的速度超调,尤其是在低速和轻载的工况下更为明显;(2)外负载一定时,液压缸速度与调速阀的开口面积成比例,表现为开口面积越小启动时的超调量越大;(3)在同一调速阀开口面积、不同外负载情况下,系统启动后的速度稳态值基本一致,表明该回油调速系统具有良好的速度刚度特性;(4)外负载主要影响系统的瞬态响应过程,在小负载情况下,系统超调量和速度达到稳定值所经历时间较大负载时有所增加。     

民用飞机舵面运动特性对飞行特性影响研究

针对舵面运动特性对现代电传民用飞机飞行特性及飞行安全的影响以及现阶段国内研究的局限性。 这里建立了飞机六自由度动力学模型、舵面运动动力学模型;依据飞机选定的舵机偏转速率限制速度、全机气动力特性、舵面铰链力矩特性,利用MATLAB/simulink工具以纵向操纵面升降舵为例,仿真研究了舵面动力学特性以及舵面动力学特性对飞行特性的影响。结果表明,不同操纵状态下,舵面运动特性差异很大,操纵频率高,舵面以及飞机的响应幅值减小,飞机响应相位滞后增加;过高的操纵频率,将会引入非线性因素,以及附加相位滞后。     

圆筒形超深海半潜式钻井储油平台运动特性分析

使用Pro/E软件对SEVAN 650平台和GVA 7500平台建模,将模型导入ANSYS Workbench程序的Hydrodynamic Diffraction模块,计算出2座半潜式钻井平台南海海况风暴自存状态下的运动响应幅值算子,得出2座平台各自的垂荡、横摇和纵摇特性曲线,进而对2座平台南海海况风暴自存状态下的运动特性进行对比分析.结果表明:SEVAN 650圆筒形半潜式平台在原油存储性能和甲板承受可变载荷性能优于GVA 7500平台的前提条件下,其在风暴自存状态时具有比GVA 7500更优的抗倾性能,但SEVAN 650平台在风暴情况下的垂荡响应幅值需要进一步减小.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to