Relationship of mode transitions and standing waves in helicon plasmas

Helicon wave plasma sources have the well-known advantages of high efficiency and high plasma density, with broad applications in many areas. The crucial mechanism lies with mode transitions, which has been an outstanding issue for years. We have built a fluid simulation model and further developed the Peking University Helicon Discharge code. The mode transitions, also known as density jumps, of a single-loop antenna discharge are reproduced in simulations for the first time. It is found that large-amplitude standing helicon waves(SHWs) are responsible for the mode transitions, similar to those of a resonant cavity for laser generation.This paper intends to give a complete and quantitative SHW resonance theory to explain the relationship of the mode transitions and the SHWs. The SHW resonance theory reasonably explains several key questions in helicon plasmas, such as mode transition and efficient power absorption, and helps to improve future plasma generation methods.

Roll System and Stock's Multi-parameter Coupling Dynamic Modeling Based on the Shape Control of Steel Strip

The existence of rolling deformation area in the rolling mill system is the main characteristic which dis- tinguishes the other machinery. In order to analyze the dynamic property of roll system＇s flexural deformation, it is necessary to consider the transverse periodic movement of stock in the rolling deformation area which is caused by the flexural deformation movement of roll system simul- taneously. Therefore, the displacement field of roll system and flow of metal in the deformation area is described by kinematic analysis in the dynamic system. Through intro- ducing the lateral displacement function of metal in the deformation area, the dynamic variation of per unit width rolling force can be determined at the same time. Then the coupling law caused by the co-effect of rigid movement and flexural deformation of the system structural elements is determined. Furthermore, a multi-parameter coupling dynamic model of the roll system and stock is established by the principle of virtual work. More explicitly, the cou- pled motion modal analysis was made for the roll system. Meanwhile, the analytical solutions for the flexural defor- mation movement＇s mode shape functions of rolls are discussed. In addition, the dynamic characteristic of the lateral flow of metal in the rolling deformation area has been analyzed at the same time. The establishment ofdynamic lateral displacement function of metal in the deformation area makes the foundation for analyzing the coupling law between roll system and rolling deformation area, and provides a theoretical basis for the realization of the dynamic shape control of steel strip.

Analysis of microstructure and performance of temper bead welded joints for SA508-3 steel by Quenching and Tempering mode

The HAZ microstructure and performance of Quenching and Tempering mode temper bead welding and general welded joints which were made on SA508-3 steel of 60 mm thickness were compared in this article. The result shows that tempering sorbite which has excellent overall performance was obtained in both modes. The microstructure of Quenching and Tempering mode welded joints got more fine grain. Even though the hardness of tempering bead welded joints is higher than the general one,it still meets the standards which is lower than 350 HV. The impact absorbing energy of each district of tempering bead welded joints HAZ reached 170 J,which is equal to general one.

MIXED MODE SCC OF 18-8 STAINLESS STEEL IN BOILING 42% MgCl_2 SOLUTION

A series of mixed mode tests were carried out on 18-8 stainless steel in boiling 42% MgCl_2 solution.The results show that for any K_Ⅱ/K_Ⅰ ratio,the SCC direction coin- cides well with the crack tip maximum normal stress plane,while the SCC resistance of the material reduces as the ratio of K_Ⅱ/K_Ⅰ increases.The experimental results were discussed in the light of anode dissolving mechanism and the effect of mixed mode loading on crack tip stress and strain.It is concluded that for fracture analysis if mixed mode cracks were simply taken into account as mode Ⅰ cracks,and only mode Ⅰ testing results as mode Ⅰ fracture criter- ion were employed,it may not be safe.

Eurovet Unveils the New Image of Hong Kong Mode Lingerie 2010 March 30-31, at the Hong Kong Convention and Exhibition Centre

Organized by Eurovet, the world’s leading lingerie and beachwear trade show organizer and supported by Hong

100 kHz弹光调制器多功能调制仿真

针对弹光调制器(photoelastic modulator,PEM)在超高速全偏振领域的测量问题,研究一种目标频率在100 kHz附近的圆型PEM,由弹光晶体和2个方位角相差45°的压电驱动器组成。通过理论计算弹光晶体谐振频率和压电驱动器振动频率,当二者频率达到一致时,PEM工作在谐振状态,此时PEM的调制效率达到最高。当PEM达到谐振状态并趋于稳定后,调节两压电驱动器驱动电压的幅值与相位,实现纯驻波模式和纯行波模式两种特殊调制,纯驻波模式可实现纯电控制下调制快轴的延迟量和方位角;纯行波模式可实现纯电控制下调制快轴以PEM谐振频率的半频速度高速旋转。最后,利用COMSOL有限元仿真模拟两种调制模式下PEM,验证两种调制状态下的PEM振型及其快轴方向,表明PEM可实现多功能弹光调制,为后续偏振测量提供理论支撑。

骨转移瘤治疗中骨盆假体的生物力学数值分析

为研究骨盆骨肿瘤手术后骨盆假体的强度和稳定性,针对具体病例建立骨盆-假体结构系统的有限元模型,分别进行静力和动力问题计算。静力工况为双腿和单腿站立状态,动力工况为骨盆不同方向、不同高度跌落以及不同固定方式的跌落过程,通过数值模型分析骨盆-假体结构系统不同工况的受力和变形。计算结果显示:在3种站立姿态下,结构最大应力均小于骨骼假体材料的强度极限,患侧的应力更大;骨盆从5 m高处跌落造成的最大应力可能超过骨骼和假体材料的屈服强度;螺钉固定方式对应力分布影响也较大。

Lateral resonances in initial stressed 1-3 piezocomposites

A theoretical analysis of the lateral resonances in 1-3 piezocomposites with poling initial stress is conducted using the Bloch wave theory. Based on the linear piezoelectricity theory, theoretical formulations that include initial stress for the propagation of acoustic plane waves are made. Numerical calculations are performed to study the effects of the initial stress on the lateral mode frequencies and the stop band. It is found that lateral mode frequencies increase with the piezoelectricity of the piezocomposites, but decrease with the poling initial stress. The influence of the initial shear stress on the lateral mode frequencies is minimal, and can thus be neglected.

Investigation on the choice of boundary conditions and shape functions for flexible multi-body system

The objective of this investigation is to examine the correctness and efficiency of the choice of boundary conditions when using assumed mode approach to simulate flexible multi-body systems. The displacement field due to deformation is approximated by the Rayleigh-Ritz assumed modes in floating frame of reference （FFR） formulation. The deformations obtained by the absolute nodal coordinate （ANC） formulation which are transformed by two sets of reference coordinates are introduced as a criterion to verify the accuracy of the simulation results by using the FFR formulation. The relationship between the deformations obtained from different boundary conditions is revealed. Nu- merical simulation examples demonstrate that the assumed modes with cantilevered-free, simply-supported and free- free boundary conditions without inclusion of rigid body modes are suitable for simulation of flexible multi-body system with large over all motion, and the same physical deformation can be obtained using those mode functions, differ only by a coordinate transformation. It is also shown that when using mode shapes with statically indeterminate boundary conditions, significant error may occur. Furthermore, the slider crank mechanism with rigid crank is accurate enough for investigating boundary condition problem of flexible multi-body system, which cost significant less simulating time.

Video-based measurement and data analysis of traffic flow on urban expressways

A new video-based measurement is proposed to collect and investigate traffic flow parameters. The output of the measurement is velocity-headway distance data pairs. Because density can be directly acquired by the reciprocal of headway distance, the data pairs have the advantage of better simultaneity than those from common detectors. By now, over 33 000 pairs of data have been collected from two road sections in the cities of Shanghai and Zhengzhou. Through analyzing the video files recording traffic movements on urban expressways, the following issues are studied：laws of vehicle velocity changing with headway distance, proportions of di0erent driving behaviors in the traffic system, and characteristics of traffic flow in snowy days. The results show that the real road traffic is very complex, and factors such as location and climate need to be taken into consideration in the formation of traffic flow models.

Investigation into rail corrugation in high-speed railway tracks from the viewpoint of the frictional self-excited vibration of a wheel–rail system

A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.

Synthesis,Crystal Structure and DNA-binding Properties of a New Copper(Ⅱ) Schiff Base Complex

A new asymmetric bidentate copper（Ⅱ） complex,CuL 2（HL=2-（（E）-（4-bromophenylimino）methyl）-6-bromo-4-chlorophenol）,has been synthesized and characterized by elemental analyses and single-crystal X-ray diffraction.The complex crystallizes in the monoclinic space group P2 1 /c with a=11.218（3）,b=9.355（3）,c=13.449（4）,β=108.722（4）°,V=1336.8（6）3,Z=2,Dc=2.008 g/cm 3,μ（MoKα）=7.024 mm-1,F（000）=806,S=0.999,the final R=0.0342 and wR=0.0641for2611observed reflections （I〉2σ（I））.The central copper（Ⅱ） is four-coordinate and bonds to two nitrogen and two oxygen atoms from two Schiff base ligands.The complex is linked into a two-dimensional supramolecular structure by weak intermolecular interactions.In addition,DNA-binding properties of the metal complex were investigated using spectrometric titrations and viscosity measurements.The results show that the complex binds with calf-thymus DNA（CT-DNA）,presumably via a partial intercalative mode.The intrinsic binding constant of the Cu（Ⅱ） complex with DNA is 7.335×10 3 M-1.

Experimental investigation on flow modes of electrospinning

Electrospinning experiments are performed by using a set of experimental apparatus, a stroboscopic system is adopted for capturing instantaneous images of the cone- jet configuration. The cone and the jet of aqueous solutions of polyethylene oxide （PEO） are formed from an orifice of a capillary tube under the electric field. The viscoelastic con- stitutive relationship of the PEO solution is measured and discussed. The phenomena owing to the jet instability are described, five flow modes and corresponding structures are obtained with variations of the fluid flow rate Q, the electric potential U and the distance h from the orifice of the cap- illary tube to the collector. The flow modes of the cone-jet configuration involves the steady bending mode, the rotat- ing bending mode, the swinging rotating mode, the blurring bending mode and the branching mode. Regimes in the Q-U plane of the flow modes are also obtained. These results may provide the fundamentals to predict the operating conditions expected in practical applications.

3D Track-keeping Method for Autonomous Underwater Vehicle

In this paper, 3D track-keeping control method for autonomous underwater vehicle (AUV) with and without the influence of ocean current is investigated. Because the system to be controlled is highly nonlinear and strong coupled, an approach is used to divide it into two subsystems. One is to control the heading and the track error on the horizontal plane. The other is to control the pitch and the track error on the vertical plane. The results of computer simulation show that the autopilot works properly, it can capture the current waypoint and turns to track the next path automatically.

Contents and Abstracts of Journal of Mechanical Engineering ISSN 0577-6686,CN 11-2187/TH

Review on Key Technology of Hydrodynamic and Hydrostatic High-frequency Motor Spindles XIONG Wanli YANG Xuebing LV Lang YUAN Julong （National Research Center for High Efficiency Grinding, Hunan University, Changsha 410082, China） Abstract： High-speed spindles supported by hydrodynamic and hydrostatic hybrid bearings are widely applied in the field of high-speed precision machine tools due to highrotation accuracy, high dynamic stiffness, high vibration damping and long life. But some technical problems caused by integrated structure and high speed, including temperature rise control and motor performance optimization, are yet to be resolved when the integration of hybrid bearings and motor are developed to meet the requirements of ultra-high speed and ultra-precision machining Also major scientific problems involved in the dynamic and thermal characteristics of hybrid journal bearings and the mechanism of electromagnetic losses of high-frequency motor are to be further studied.

Contents and Abstracts of Journal of Mechanical Engineering ISSN 0577-6686, CN 11-2187/TH

Effect of Kinematic Behavior of Caudal Fin on Fishlike Robot Propulsion during Steady Swimming CHEN Weishan XIA Dan LIU Junkao SHI Shengjun （State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150080, China）Abstract： The speed convergence algorithm is applied in the numerical simulation of a fishlike robot in self-propelled swimming. All simulations are started with the body at rest, the swimming speed is dynamically modified to converge to the steady value by verifying the fluid forces during the swimming process. The effects of kinematic behavior of caudal fin on fishlike robot propulsion are numerical investigated in the converged steady speed, while the propulsive mechanism and flow field structure are revealed. The results show that the steady speed can be predicted validly by using the speed convergence algorithm, while the relation between the kinematic behavior and the propulsion, power consumption and propulsive efficiency can be obtained through varying the phase difference and the maximum angle of attack. The effects of kinematic behavior of caudal fin on the wake structure and wake strength are clearly reflected in the three dimensional flow field structures. The fmdings are of great significance to the swimming speed prediction, effect of kinematic behavior on fishlike robot propulsion as well as the motion narameter design for fishlike robot

Contents and Abstracts of Journal of Mechanical Engineering ISSN 0577-6686,CN 11-2187/TH

Recent Research Advances and Expectation of Mechanical Engineering Science in China;Research Progress of Friction Behavior during Powder Forming;Review of Vehicle State Estimation Problem under Driving Situation;Fault Diagnosis Method Based on Acoustic Holography;Effect of Track Structure Parameters on Rolling Contact Stresses of Wheel-rail

Contents and Abstracts of Chinese Journal of Mechanical Engineering (Chinese Edition),ISSN 0577-6686,CN 11-2187/TH

Vol.43,No.3,2007 NEXT GENERATION LITHOGRAPHY——IMPRINT LITHOGRAPHY DING Yucheng LIU Hongzhong LU Bingheng LI Dichen (State Key Laboratory of Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, China) 1

“N-2”方式线路备自投装置研制

随着社会对供电可靠性要求的进一步提高,电网的网架结构不断得到加强,单线路链式供电方式逐渐增强为辐射状双回线供电,但即使是双回线供电,也存在全站失压的风险,且失电后恢复供电的时间较长,影响范围广,风险不容忽视。针对以上问题,有效利用网架优势来降低双回线的安全风险,用第三条线路作为备用电源,并研发“N-2”方式线路备自投装置来代替人工,自动完成逻辑动作,达到快速恢复供电的目的。