磁场中旋转圆板的磁弹性行波动力学分析

研究磁场作用下导电旋转圆形薄板的行波动力学特性问题。根据哈密顿原理推导出磁场作用下旋转运动圆板的磁弹性振动控制方程,根据边界条件设定行波特性振型函数,应用伽辽金积分得到了行波动力学特征方程。通过算例分析旋转运动圆板在磁场作用下的前、后行波振动频率变化和各阶模态的临界转速与振动失稳问题,并得到了圆形薄板临界转速对应各阶模态的变化规律,分析了不同磁场强度对各阶模态振动频率的影响曲线和不同振动模态阻尼的变化曲线,以及相同磁场作用下旋转圆板厚度变化对振动频率和临界转速的影响曲线。结果表明:磁场、转速、板厚等参数对旋转圆板的行波振动有显著影响。

一类行波动的非线性振荡(英文)

研究了满足Dirichlet边界条件及关于变量t满足周期条件的非线性振荡偏微分方程 .利用变分约化法原理 ,证明了当 - 5 <a<- 1 ,3<b <7时所研究的方程至少存在 4个解 .

空间灾害性扰动事件数值预报初探——行星际激波动力学问题6步求解法

空间灾害性天气的预报是日地物理学界及高科技领域的热门话题 .未来预测太阳剧烈扰动所造成的行星际风暴到达地球空间的状态势必借助于数值方法 .浅析了空间灾害性扰动事件数值预报存在的问题及未来设想 ,针对这一目的对一维球对称问题提出了处理行星际激波的 6步求解方法 ,指出未来空间灾害性扰动事件预报模式应是一个基于三维的以真实太阳风为背景自洽建立起来的、以太阳等离子体输出及磁场全球结构为初边值、太阳、行星际、地磁因果耦合模式 .

压电智能桁架结构/控制系统的波动分析及优化设计

基于波动的观点 ,分析了压电智能桁架结构 /控制系统的行波动力学模型 ,并从能量观点进行控制器设计。结构单元中传播的波在节点处反射、散射 ,考虑节点处的位移和力的边界条件 ,将局部波动模型合并成总体模型 ,并相应建立了结构 /控制系统的一体化优化设计模型。数值算例的结果表明 。

EDA设计中时钟的可靠性探讨

在CPLD/FPGA芯片编程设计时,通常需要用时钟来控制系统中各模块协调工作,如果时钟设计不当,在极限温度、电压或制造工艺偏差的情况下将导致错误的行为,并且调试困难。本文就此对全局时钟、门控时钟、多级逻辑时钟和波动式时钟进行分析探讨,以求在设计电路中消除毛刺,提高电路系统的稳定性。

LEAD SCREW LINEAR ULTRASONIC MOTOR USING BENDING VIBRATION MODES

The operating principle of a lead screw linear ultrasonic motor using bending vibration modes is analyzed. The simplified beam bending vibration model is used to analyze the dynamics characteristics of the motor. Motion trajectory equations are derived for driving points of the stator. The motor operation and driving mechanisms are investigated. The vibration modes and the construction of the motor are analyzed by using the finite element method （FEM）. A prototype motor is built and its stator dimension is 13 mm × 13 mm× 30 mm. The motor is experimentally characterized and the maximum output force of 5- 2 N is obtained.

THE EQUIVALENT CIRCUIT AND CONTROL SYSTEM OF TRAVELLING WAVE TYPE ULTRASONIC MOTOR

The ultrasonic motor is a sort of new type of micromotor with special structure. By use of piezoelectric converse effect of ceramics, the electrical energy is transformed into mechanical energy. Its operating principle is quite different from that of the traditional motors. In this paper the equivalent circuits of the ring stator and even the whole motor are proposed after studying the equivalent circuit of piezoelectric vibrator. Then the paper makes detailed analyses of each part of the control system, which has been simplified by the equivalent circuit. The theory in this paper has been proved through experiments.

Solution of Travelling Wave for Nonlinear Disturbed Long-Wave System

The approximate expressions of the travelling wave solutions for a class of nonlinear disturbed long-wave system are constructed using the generalized variational iteration method.

Dynamic Interaction of Parallel Moving Ships in Close Proximity

Nowadays,there are many studies conducted in the field of marine hydrodynamics which focus on two vessels traveling and floating in sufficiently close proximity to experience significant interactions.The hydrodynamic behavior of parallel moving ships in waves is an interesting and important topic of late.A numerical investigation has been carried out for the prediction of wave exciting forces and motion responses of parallel moving ships in regular waves.The numerical solution was based on 3D distribution technique and using the linear wave theory to determine the exciting forces and ship＇s motion.The speed effects have been considered in the Green function for more realistic results.The numerical computations of wave exciting forces and motion responses were carried out for a Mariner and Series 60 for the purpose of discovering different Froude numbers and different separation distances in head sea conditions.Based on the numerical computations,it was revealed that the sway,roll and yaw have a significant effect due to hydrodynamic interaction.

Bifurcations of Exact Traveling Wave Solutions for(2+1)-Dimensional HNLS Equation

For the(2+1)-Dimensional HNLS equation,what are the dynamical behavior of its traveling wave solutions and how do they depend on the parameters of the systems? This paper will answer these questions by using the methods of dynamical systems.Ten exact explicit parametric representations of the traveling wave solutions are given.

ANALYSIS OF GROUND TARGET STEALTH BASED ON PASSIVE MILLIMETER-WAVE DETECTION

Passive Millimeter-Wave(MMW)detection has become a threat to ground targets.Toenhance the survivability of the ground target in the future battlefield,passive MMW stealth tech-nology is analyzed in this paper.Based on the passive MMW detection principle,computation andanalysis are made for the MMW apparent temperature of tank in different actual combat conditions.The necessity of the passive MMW stealth is analyzed and the passive MMW stealth methods arealso studied.

Northern Hemisphere Stratospheric Polar Vortex Extremes in February under the Control of Downward Wave Flux in the Lower Stratosphere

Using ECWMF ERA-40 and Interim reanalysis data, the planetary wave fluxes associated with the February extreme stratospheric polar vortex were studied. Using the three-dimensional Eliassen-Palm (EP) flux as a measure of the wave activity propagation, the authors show that the unusual warm years in the Arctic feature an anomalous weak stratosphere-troposphere coupling and weak downward wave flux at the lower stratosphere, especially over the North America and North Atlantic (NANA) region. The extremely cold years are characterized by strong stratosphere-troposphere coupling and strong downward wave flux in this region. The refractive index is used to examine the conception of planetary wave reflection, which shows a large refractive index (low reflection) for the extremely warm years and a small refractive index (high reflection) for the extremely cold years. This study reveals the importance of the downward planetary wave propagation from the stratosphere to the troposphere for explaining the unusual state of the stratospheric polar vortex in February.

Numerical simulation of heat transfer and flow of cooling air in triangular wavy fin channels

Numerical computation models of air cooling heat transfer and flow behaviors in triangular wavy fin channels(TWFC) were established with structural parameters of fins considered.The air side properties of heat transfer coefficient and pressure drop are displayed with variable structural parameters of fins and inlet velocities of cooling air.Within the range of simulation,TWFC has the best comprehensive performance when inlet velocity vin=4-10 m/s.Compared with those of straight fins,the simulation results reveal that the triangular wavy fin channels are of higher heat transfer performances especially with the fin structural parameters of fin-height Fh=9.0 mm,fin-pitch Fp=2.5-3.0 mm,fin-wavelength λ=14.0-17.5 mm and fin-wave-amplitude A=1.0-1.2 mm.The correlations of both heat transfer factor and friction factor are presented,and the deviations from the experimental measurements are within 20%.

Nonlinear wave-wave interactions and wedge waves

A tetrad mechanism for exciting long waves, for example edge waves, is described based on nonlinear resonant wave-wave interactions. In this mechanism, resonant interactions pass energy to an edge wave, from the three participating gravity waves. The estimated action flux into the edge wave can be orders of magni- tude greater than the transfer fluxes derived from other competing mechanisms, such as triad interactions. More- over, the numerical results show that the actual transfer rates into the edge wave from the three participating gravity waves are two- to three- orders of magnitude greater than bottom friction.

The Traveling Wave Reactor: Design and Development

The traveling wave reactor （TWR） is a once-through reactor that uses in situ breeding to greatly reduce the need for enrichment and reprocessing. Breeding converts incoming subcritical reload fuel into new critical fuel, allowing a breed-burn wave to propagate. The concept works on the basis that breed-burn waves and the fuel move relative to one another. Thus either the fuel or the waves may move relative to the stationary observer. The most practical embodiments of the TWR involve moving the fuel while keeping the nuclear reactions in one place-sometimes referred to as the standing wave reactor （SWR）. TWRs can operate with uranium reload fuels including totally depleted uranium, natural uranium, and low-enriched fuel （e.g., 5.5% 23sU and below）, which ordinarily would not be critical in a fast spectrum. Spent light water reactor （LWR） fuel may also serve as TWR reload fuel. In each of these cases, very efficient fuel usage and significant reduction of waste volumes are achieved without the need for re- processing. The ultimate advantages of the TWR are realized when the reload fuel is depleted uranium, where after the startup period, no enrichment facilities are needed to sustain the first reactor and a chain of successor reactors. TerraPower＇s conceptual and engineering design and associated technolo- gy development activities have been underway since late 2006, with over 50 institutions working in a highly coordinated effort to place the first unit in operation by 2026. This paper summarizes the TWR technology： its development program, its progress, and an analysis of its social and economic benefits.

The feasibility experimental study of pumping and shunting pump under pressure in water injection station

At present in the process of water injection station operation, starting and stopping the pump caused system pressure fluctuations, and the fluctuations caused many problems about downstream injection wells. In order to eliminate the fluctuations and reduce problems, taking start pump, connect pump test under pressure in the water injection station installed the rotor frequency control system Changqing oil field developed. During the experiment, by progressively increasing the pressure pump to verify start pump with pressure feasibility test, the result shows when the pressure in the 0-25MPa pressure start and connect pump can be realized, and forecast the maximum pressure of the current start of the station with pressure pump. Start pump with pressure achieve the elimination of pressure fluctuations, provide the prerequisites about realizeing stable water injection pressure, and ultimately realize oil field water injection station to be automatic water injection laid a foundation.

Impact of Oil Price Fluctuations on Returns of Different Sectors of Malaysian Stock Market

Oil price fluctuations affect equity values in North American, European, and Gulf Cooperation Council （GCC） stock markets, as evidenced by prior studies. However, they only focus on market-wide level analysis. This study, through both market level and sector level analyses, examines the sensitivity of Malaysian stock returns to oil price fluctuations over the period from January 2000 to March 2014. A multifactor market model has been employed to capture this sensitivity. The regression results show a positive impact of oil price changes on the Financial Times Stock Exchange Kuala Lumpur Composite Index （FTSE KLCI） market return. Consumer staples and energy sector index returns were also positively affected by oil price changes. On the other hand, utilities and telecom services were negatively affected over the study period. Moreover, Granger causality analysis was performed to see if oil price fluctuations Granger cause the stock indices to change. With one month lag period, oil price fluctuations Granger cause consumer staple, energy, industrials, and telecommunication services return. Relevant policymakers and market caretakers （Ministry of Finance, Central Bank, and Security Commission） may use the fmdings of this study to develop and incorporate a preventive mechanism to minimize the unfavorable impacts of oil price fluctuations on different sectors of stock market, and Malaysian economy in general.

Coal price fluctuations and the impact on financial risk Evidence from China＇s coal listed companies

With the rise of coal price, the proportion of loss-making enterprises shows an upward trend in China＇s coal industry. This paper uses Altman Z-Score model to measure financial risk of 19 listed companies in the coal industry in A-share market from 1995 to 2007. Empirical results show that Year-Based price index of coal price has a negative correlation with the financial risk but has no significance, and coal chain price has a significant negative correlation with the financial risk. Further research indicates that enterprises increase bad investment, and a lot of debts caused by short-term rise in coal prices. The results also show that the financial risk in the coal industry declines with the rise of GDP growth rate and increases with the rise of inflation rate.

Optimal Filtering Correction forMarine Dynamical Positioning Control System

This paper focuses on the problem of control law optimization for marine vessels working in a dynamical positioning （DP） regime. The approach proposed here is based on the use of a special unified multipurpose control law structure constructed on the basis of nonlinear asymptotic observers, that allows the decoupling of a synthesis into simpler particular optimization problems. The primary reason for the observers is to restore deficient information concerning the unmeasured velocities of the vessel. Using a number of separate items in addition to the observers, it is possible to achieve desirable dynamical features of the closed loop connection. The most important feature is the so-called dynamical corrector, and this paper is therefore devoted to solving its optimal synthesis in marine vessels controlled by DP systems under the action of sea wave disturbances. The problem involves the need for minimal intensity of the control action determined by high frequency sea wave components. A specialized approach for designing the dynamical corrector is proposed and the applicability and effectiveness of the approach are illustrated using a practical example of underwater DP system synthesis.

Navigation of Robot Using VFH＋ Algorithm

This paper describes a reactive navigation proposed for a differentially driven robot. The aim of the reactive navigation is to prescribe behavior to the robot based on actual sensor values that is collision-free. Analysis of reactive navigation methods shows that there is no reliable reactive collision-free method. However, method VFH＋ is suboptimal reactive navigation method for static environment. Original method was proposed for ultrasonic rangefinders. Nowadays, much more sophisticated sensors are available. That is why our modification is proposed for a laser rangefinder attached to indoor mobile robot. Results are presented as simulation in Matlab and also as experiments with real robot. Based on these experiments, it can be claimed that VFH＋ is very effective reactive navigation method for various sensors and environments and it can be modified for different requirements on robot behavior.