Table of Content

30 July 2012, Volume 46 Issue 07 Previous Issue    Next Issue

Metallography and Metallurgical Technology

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Robust Optimization for an Autobody Outer Panel Stamping Process ZHANG Ji-Chao-1, LIU Gang-2, LIN Zhong-Qin-1, GAO Wei-3, LI Shu-Hui-1 2012, 46 (07):  1005-1010.  Abstract ( 3703 )   Save In the case of an autobody outer panel stamping process, a metamodel based on FEsimulation, design of experiment, response surface methodology(RSM) and MonteCarlo method was constructed and the deterministic optimization result was obtained. By constructing and solving the robust optimization model composed of mean and standard deviation of quality index, the robust optimal solution was obtained and compared with the deterministic optimization result. It is demonstrated that the product quality variations are reduced significantly, and quality targets (reject rate) are achieved under the robust optimal solution. This method can also be used during the early phase of product and tooling design to reduce commissioning period. References | Related Articles | Metrics

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Spherical Shape Error Analysis and Compensation in Conventional Generative Sphere Grinding LI Dong-Dong-1, 2 , CHA Ti-Jian-1, XU Ming-Ming-1, HU De-Jin-1, XU Li-Ming-1 2012, 46 (07):  1011-1014.  Abstract ( 3199 )   Save In order to improve the precision of the spherical shape of conventional generative sphere grinding (CGSG), spherical shape error of CGSG was analyzed. A novel sphere grinding machine tool was developed, and a variable depth of cut sphere grinding method was introduced to decrease the sphericity error of valleyshaped. The experiment results show that the sphericity error can reach less than 5 μm by using variable depth of cut sphere grinding. The sphere can satisfy the requirements of the operating by using this method. References | Related Articles | Metrics

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Research of Relationship Between Interelectrode Dielectric Properties and Energy Distribution in Wire Electrical Discharge Machining LIU Zhi-Dong, WEI Wei, LU Lin-Yan, XU An-Yang 2012, 46 (07):  1015-1020.  Abstract ( 2580 )   Save A resistance model of interelectrode dielectric fluid in wire electrical discharge machining(WEDM) was established. And the relationship among machining energy, electrical conductivity and thickness of a workpiece was analyzed. The resistance model of interelectrode dielectric fluid was verified by experiments. The results show that with the higher electrical conductivity or the thickness of workpiece, the larger the interelectrode leakage current is during discharge, the more the energy loss in the interelectrode dielectric fluid, the lower the machining efficiency. Cutting efficiency is obviously influenced by the change of the resistance which is due to the change of electrical conductivity. References | Related Articles | Metrics

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Experimental Study of MistJetting Electrical Discharge Milling YANG Kai, GU Lin, XUE Rong, ZHANG Fa-Wang, ZHAO Wan-Sheng 2012, 46 (07):  1021-1025.  Abstract ( 2477 )   Save This study investigated the optimization of mistjetting electrical discharge machining (EDmilling) process. Firstly, experiments were carried out to choose the ranges of parameters such as ton/toff, milling layer depth（MLD）and tool electrode wall thickness for optimization. Then a set of experiments was designed based on Taguchi method to investigate these effects of main machining parameters on the material removal rate(MRR) and tool wear ratio(TWR). The analysis of variance(ANVOA) results show that the ton/toff has a dominate influence on the MRR and the influences of the machining parameters on the TWR are negligible. A higher MRR is obtained through the optimized parameters. Key words： References | Related Articles | Metrics

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Analysis and Suppression of the Simi-Crawling Phenomenon during High Hardness Spherical Grinding Process WANG Jian-Lou, LUO Rui, XU Li-Ming, WANG Yu-Jue, HU De-Jin 2012, 46 (07):  1026-1031.  Abstract ( 2674 )   Save The simi-crawling phenomenon is first discovered during the high hardness spherical grinding process. Through the modeling of spindle-wheel-workpiece system in the spherical grinding machine, the ralationship between the actual feed rate and the theoretical feed rate was presented, and the influence of feed system stiffness, theoretical feed rate and feed interval upon the feed error was quantitatively analyzed. The mechanism of the simicrawling phenomenon is revealed and its impact on sphere grinding quality and efficiency was discussed. In order to prevent from the harm caused by the simi-crawling phenomenon in sphere grinding, the adaptive fuzzy control strategy based on dual-threshold of both acoustic and electrical current signals was proposed to monitor the high hardness spherical grinding process. The strategy greatly improves the stability of grinding process and workpiece surface quality, and effectively suppress the simi-crawling phenomenon. References | Related Articles | Metrics

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Distribution of Surface Roughness on Cup-Wheel Spherical Grinding HOU Hai-Yun-1, 2 , LUO Rui-1, XU Li-Ming-1, HU De-Jin-1 2012, 46 (07):  1032-1036.  Abstract ( 3823 )   Save An approach to predict distribution of spherical surface roughness was proposed based on the density of cupwheel spherical grinding trajectories. Statistics of amount of trajectories’ points in oneunit length circle were carried out aiming to segmented spherical surface. Trajectories density distribution varies with different sizes of cup wheel. Two groups of experiments were done to test the distribution of surface roughness and the conclusion above was verified by the experimental results. The final conclusion is that the sizes of cup wheel and spherical workpiece are key factors that impact the distribution of spherical surface roughness with cupwheel grinding. References | Related Articles | Metrics

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Wear Mechanism of Tool in High-speed Milling of Titanium Alloy TC6 XU Jin-Yang, ZHENG Xiao-Hu, AN Qing-Long, CHEN Ming 2012, 46 (07):  1037-1042.  Abstract ( 3003 )   Save The PVD and CVD coated carbide tools were adopted for highspeed milling of α+β phase titanium alloy TC6. Both the wear pattern and wear mechanism were investigated. The results show that PVD coated tool obtains smaller tool flank wear, longer tool life, and is more suitable for milling of titanium alloy TC6 compared with CVD coated tool under the same cutting condition. The rake face of PVD coated tool mainly suffers adhesive wear and oxidation wear while the flank face suffers border wear. Micro chipping is observed to be the main tool failure ascribed to the negative effects of adhesive wear and border wear on the main cutting edge. In contrast, the tool life of CVD coated tool is shorter; its rake face mainly suffers early microchipping and subsequent crater wear and adhesive wear while its flank face suffers abrasive wear. Coating peeling is confirmed to be the main tool failure for CVD coated tool. References | Related Articles | Metrics

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Study on Cracking Mechanism of Laser Clad NiCrBSi Coating YU Ting-1, 2 , DENG Qi-Lin-1, ZHANG Wei-3, DONG Gang-4, YANG Jian-Guo-1 2012, 46 (07):  1043-1048.  Abstract ( 4026 )   Save Cracking mechanism of laser clad NiCrBSi coating was studied through investigation on the microstructure of the coating. The microstructure, crack behavior and chemical compositions of fracture section were investigated. The results show that the Ni60 coating has high crack susceptibility, which still has numerous cracks due to high brittle brittleness and high thermal gradient even if the difference of thermal expansion coefficient between the coating and substrate is low. The reasons are: the coating has a large amount of coarse hard primary phases, hard eutectics and a few of tough phase, resulting in high brittle hardness; the fracture section has slag containing Ca, S, Si elements; the coarse hard phase obstructs the flow of metal liquid, resulting in the discontinuity of the metal matrix; the grain boundary of the coarse hard phase is crack source due to the separation of the liquid films formed on the grain boundary under the action of tensile stress induced in cooling process. In addition, cracks initiate and propagate downwards along grain boundary of coarse hard phase, which has a typical characteristic of hot crack. References | Related Articles | Metrics

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Study on the Microstructure, Chemical Gradient and Machinablity of High-strength Alloy Boron Cast Iron AN Qing-Long, NIU Qiu-Lin, MING Wei-Wei, CHEN Ming 2012, 46 (07):  1049-1053.  Abstract ( 3234 )   Save Alloy boron cast iron has high property of hardness, high strength, abrasion resistance and heat resistance, which is often used in cylinder liner of highspeed locomotive diesel. The microstructure and chemical composition of the alloy boron cast iron were discussed. The machinability evaluation was carried out by turning tests. The result indicates that the alloy boron cast iron as one kind of Atype graphite cast iron has excellent mechanical property. Sialon ceramic tool shows much better performance compared with uncoated and TiAlN coated P20 carbide tool during high speed cutting of alloy boron cast iron. References | Related Articles | Metrics

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Recognition of Work-piece and Location of Initial Seam Position for Mobile Welding Robot DENG Yong-Jun-a, WU Ming-Hui-b, CHEN Jin-Yun-a, CHEN Shan-Ben-a 2012, 46 (07):  1054-1058.  Abstract ( 3678 )   Save Considering the environmental characters of welding in unstructured space, via vision technology, a twosteps template matching method for workpiece recognition based on circle projection and Zernike moments was presented. An algorithm based on Hough line detection was designed to extract special lines which were used to calculate initial seam position with subpixel precision. Experiment was carried out by mobile welding robot, and series of templates were acquired by snapping workpiece images with different rotation angles. Circle projection results and Zernike moments were calculated, and they could effectively represent features of templates for typical workpiece, meanwhile errors due to rotation could be eliminated. These algorithms were proved to perform satisfied robustness of illumination and camera view. Subpixel location of initial seam position can satisfy the need for visual calculation. References | Related Articles | Metrics

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Electroplastic Effect and New Development of  Its Applications in Plastic Forming JIE Huan-Yang, DONG Xiang-Huai, FANG Lin-Qiang 2012, 46 (07):  1059-1062.  Abstract ( 3971 )   Save This paper analyzed the influencial factors and the mechanism of the electroplastic effect (EPE) and discussed its applications in plastic forming. Specially, the applications of EPE in plastic forming including micro forming and incremental forming etc. were also forecasted. This will supply references to the applications of EPE in plastic forming. References | Related Articles | Metrics

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Mathematical Model of Quasi-state Temperature Distribution of  Hot-Wire during Hot-Wire TIG Welding Process ZHAO Fu-Hai-a, b , HUA Xue-Ming-a, b , YE Xin-a, b , WU Yi-Xiong-a, b , c 2012, 46 (07):  1063-1068.  Abstract ( 2644 )   Save Based on the law of the conservation of energy and Fouriers law, the mathematical odels respectively considering the effect of resistance heat and the heat transferred through the weld pool on the hotwire temperature distribution were developed. And then based on the superposition principle the mathematical model of quasistate temperature distribution of hotwire heated by resistance energy  was  developed. The   accuracy   of  the   mathematical   model   was  validated   by comparing   the   result   of   calculating   from   the   mathematical  model  with   the   experimental  result from the literature. The impact of current density, wire feeding speed, wire extension on temperature  distribution   of   hot-wire  was elaborately  discussed.   The  results   show  that  the mathematical model has high accuracy to effectively analyze the process of wire heated   by  resistance   energy.   The  larger the current  density  or   wire  extension  is,  the   higher  the temperature in different positions on the wire extension is, however, the bigger the wire feeding speed is, the higher the preheating temperature is. In some certain cases, the matching relations  among current density, wire feeding speed and wire extension can be concluded. References | Related Articles | Metrics

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Die Face Correction Method for Springback Compensation of Sheet Metal Incremental Air-Bending Forming FU Ze-Min, ZHANG 而Geng, LIU Xu-Hui, HU Da-Chao 2012, 46 (07):  1069-1073.  Abstract ( 3348 )   Save There exist errors between the made workpieces and the CAD models owing to the springback of sheet metal incremental airbending forming. To reduce these errors, three die face correction methods for singlestep stamping (displacement adjustment method, DAM; smooth displacement adjustment method, SDAM; deformation transfer function method, DTFM) were applied to the multiplestep incremental airbending forming. With these methods, the die surfaces of sheet metal incremental airbending forming are properly corrected to compensate for springback. It is manifested by the experimental results of workpieces formed with three different die face correction algorithms that the die face correction method of closedloop forming based on experimental iteration can effectively improve the forming accuracy of workpieces.  References | Related Articles | Metrics

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Numerical Simulation in Resistance Spot Welding of Ultra-High Strength Hot-Formed Steel 2012, 46 (07):  1074-1078.  Abstract ( 2964 )   Save Based on the software SORPAS, an axial symmetric finite element model for the resistance spot welding process (RSW) of ultrahigh strength hotformed steel (UHSS) was established. By numerical simulation, change rules of the temperature field, the nugget size, etc during the spot welding were discovered quantitatively. Comparing  the numerical simulation results with the experimental measured ones, it was proved that the finite element model is feasible.  It can also provide guidance for the RSW process of the UHSS. Key words： References | Related Articles | Metrics

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Prediction of Hydrogen Induced Delayed Fracture Initiation Time of High Strength Steel Using Cohesive Zone Modeling BAI Xiao-Min, GONG Jian-Ming, WANG Yan-Fei 2012, 46 (07):  1079-1083.  Abstract ( 3124 )   Save A sequential coupling calculation method on hydrogen induced delayed fracture was developed based on cohesive zone modeling (CZM) by using finite element program-ABAQUS. Using this method, the fracture initiation time was numerically predicted for circumferentially notched round bar specimen of AISI4135 high strength steel under a constant load after electrochemically precharged. The effect of various hydrogen contents was also considered. The results show that the hydrogen dependent CZM can be used in the prediction of failure in actual structures. The predictions of the time to fracture are in good quantitative agreement with the some experimental results. The delayed fracture occurrs when a critical hydrogen concentration at the location of max hydrostatic stress is reached by diffusion. The critical hydrogen concentration is not dependent on initial hydrogen content.   References | Related Articles | Metrics

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Vision System for Molten Pool and Cathode Cleaning Zone Detecting during VP TIG Welding   YU Zhong-Gui-a, b , HUA Xue-Ming-a, b , XIAO Xiao-a, b , LI Fang-a, b 2012, 46 (07):  1084-1087.  Abstract ( 2495 )   Save To realize the realtime detection of  molten pool and cathode cleaning zone of VP TIG welding,  this article analyzed  arc spectrum of aluminum alloy variable polarity TIG welding. Based on it, appropriate filtering was selected, and a vision system was designed to observe the molten pool and the cathode cleaning zone, and clear images were obtained. Images of the molten pool and cathode cleaned zone with different percent of reverse polarity were obtained and compared. The results agree well with the cleaned zone observed after welding.In addition,the effect of the EP% on cathode cleaning and molten pool was studied and the relation curve was obtained, which can be put into practical welding for welding parameters setting. References | Related Articles | Metrics

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Welding Deformation Research on Former Window Frame of High-speed Train XU Zhi-Qiang-1, LI Zhi-Min-1, ZHU Ping-1, FENG Xiao-Zhong-2 2012, 46 (07):  1088-1091.  Abstract ( 3320 )   Save The former window frame of highspeed train is welded by spacecurved beam made up of aluminum alloy, whose welding deformation is difficult to be under control. The correction of welding deformation mostly depends on experience in the factory, which leads to the reduction of manufacture precision. This article focuses on the welding deformation simulation of former window frame of highspeed train based on the inherent strain method. Compared with the actual measurement, it suggests that the method is accurate and applicable. References | Related Articles | Metrics

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Arc Behavior and Droplet Transfer Analysis in AC-P-MIG Welding of Aluminum Alloys YUAN Lei-a, b , HUA Xue-Ming-a, b , ZHANG Wang-a, b , LI Fang-a, b , WU Yi-Xiong-a, b , c 2012, 46 (07):  1092-1096.  Abstract ( 3213 )   Save The variation in arc behavior, stability and control of droplet transfer in ACPMIG welding were studied by data acquisition system and high speed video photography system. The research reveals that the arc in EN polarity moves around the droplet and climbs up to the wire end, as a result of this behavior the wire melting rate increases, while in EP polarity the shape of arc is a typical “bell jar” and its size and brightness become the largest during the pulse stage. The droplet grows rapidly in EN stage and transfers in falling stage of EP. The alternative transformation between EN polarity and EP polarity is beneficial to the reduction in both plasma arc flow power and welding pool arc force. By controlling the EN ratio, a rapidly wire melting rate and shallow penetration appear; by controlling the pulse stage current and time, a stable one pulse one drop transfer process forms. References | Related Articles | Metrics

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Development of a Five-axis CNC System for Electro-discharge Machining Based on Linux LIANG Su, ZHAO Wan-Sheng, KANG Xiao-Ming 2012, 46 (07):  1097-1102.  Abstract ( 3529 )   Save This paper introduced a new 5-axis computer numerical control (CNC) system for electro-discharge machining (EDM) based on Linux. In the system, a motion controller of programmable multiaxis controller (PMAC) was employed as the subordinate computer, and a PC-based platform running on the Linux operating system was applied as the principal computer. An environment-friendly human-machine operating interface and various software modules used to implement non real-time tasks were developed based on Linux. Some key programs which serve controlling servo motion, main axis’ high-speed jump motion, 5-asix motion and rolling motion were also designed based on PMAC. By being applied to 5axis EDM machine and carrying out the experiments of processing shrouded turbine blisk and narrow slot, the system validated its performance of strong real-time ability, high stability and reliability as well as stable control for main axis’ highspeed jump motion. References | Related Articles | Metrics

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Technology and Weldability of Resistance Spot Welding of B1500HS Hot-Stamped Steel YANG Liu-1, CHENG Xuan-Ting-2, SUN You-2, WU Jia-Yuan-2, WANG Min-1, LIU Yu-3 2012, 46 (07):  1103-1106.  Abstract ( 3203 )   Save Resistance spot welding of B1500HS hot-stamped steel with 1.5 mm was researched, using power-frequency alternating current welding equipment. The tension strength, hardness distribution, microstructure and the cross-tensile fracture appearance were analyzed. The test results show that the hot stamped steel has good weldability, and the nugget diameters and tensile shear strength both meet production requirements. The microstructure of spot welded metal is martensite. It is easy to get button fracture mode and shear dimples. The cross-tensile strength has sharply decreased, mainly as a result of the existence of softened zone in plastic ring. References | Related Articles | Metrics

Electrotechnology

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A Novel Selective Harmonics Elimination PWM Method for Multilevel Voltage Inverters FEI Wan-Min-a, WU Qin-b, ZHANG Yan-Li-b 2012, 46 (07):  1107-1111.  Abstract ( 2926 )   Save The schemes of waveform symmetry of selective harmonic elimination (SHE) PWM methods for multilevel voltage inverters were investigated. In order to provide more opportunities for optimization design in practice, a novel generalized halfwave symmetry SHEPWM method was proposed. The advantages of the proposed method include simplicity in format, flexibility in PWM waveforms and a broad solution space. Taking a fivelevel inverter with 20 points in half a cycle as an example, twelve groups of solutions at modulation index (M) of 0.8 were obtained. Simulations based on two groups of selected keys were carried out. An experimental prototype with a fivelevel cascade voltage inverter topology was built and investigated based on the same keys. The experimental results agree well with the simulated ones and prove the validity and practicability of the new method. References | Related Articles | Metrics

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An Equivalent Circuit Method for Computing Lightning-Induced Magnetic Fields in Structures with Metallic Plates  HUANG Xiao-Hong-1, ZHOU Qi-Bin-1, DU Ya-Ping-2 2012, 46 (07):  1112-1116.  Abstract ( 2894 )   Save An equivalent circuit method was presented to calculate lightning-induced magnetic fields in a metallic structure with non-ferromagnetic plates. With this method, thin plates in the structure were divided into tangential elements. According to the skin effect, a double exponential equation was used to simulate the current distribution across the thickness. By the transformation of electric field integral equation, the plates were modeled as interconnected and coupled circuit. By combining the equivalent circuit model of plate and columns, the current distribution on the metallic structure were then solved with a circuit analysis technique. The resultant magnetic field was calculated with the Biot-Savart law. The proposed approach was compared with the numerical method of boundary element method (BEM) and validated by an experiment conducted in the lab. A good agreement among these results was found. Finally the proposed method was used to evaluate the lightning-induced magnetic field in a building equipped with plates. The shielding effect of plates was analyzed. References | Related Articles | Metrics

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Effect of Different cell Connection Methods on MCFC/MGT Hybrid System Performance LIU Ai-Guo-1, WENG Yi-Wu-2, ZHANG Ling-1 2012, 46 (07):  1117-1121.  Abstract ( 2536 )   Save The model of hybrid system was built using modular modelling method to compare the effect of different connection methods on the system performance. Characteristics of fuel cell stacks and hybrid system were compared when the fuel and oxidant are both series and series fuel and parallel oxidant. The condition that fuel and oxidant are both parallel was viewed as an example and the comparisons between different connection methods and example were completed. The results show that the fuel cell stack can be cooled better and the temperature distributions are uniform with the fuel and oxidant are both series, so the performance of whole hybrid system is better. References | Related Articles | Metrics

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Optimal Strategy for Distribution Companies to Purchase and Sell Electricity and Manage Risk Considering Consumers’ Price Elasticity of Demand HUANG Hai-Lun-1, YAN Zheng-2, YANG Yun-Yi-1, WEN Rui-1, YANG Pei-Juan-1 2012, 46 (07):  1122-1126.  Abstract ( 2505 )   Save An optimal strategy for distribution companies to purchase and sell electricity that considering consumers’ price elasticity of demand was proposed. Its objective is to maximize the companies’ expected sale profit and minimize purchase risks, quantified by CVaR. Moreover, it can optimize the procurement structure and determine the sale price to consumers. Because it is a stochastic programming model, transformation method is adopted to solve it. In this model, multiple power supply options are provided, such as spot market, forward contracts, and selfproduction. The simulation results show that the strategy is very close to the actual situation as it simultaneously considers the reflection of consumers on sale price and spot price at the purchase side. This provides a new frame for distribution companies to implement integrated risk management in electricity procurement and sale. References | Related Articles | Metrics

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Optimization Design of Transmitting Coils in the Wireless Power Transmission Based on Human Tissue Safety JIA Zhi-Wei, YAN Guo-Zheng, SHI Yu, ZHU Bing-Quan 2012, 46 (07):  1127-1131.  Abstract ( 2829 )   Save  The relationships between the biological safety in electromagnetic field, the safety of temperature rise inside  human body and the design of the receiving coil of the wireless power transmission system were analyzed. An optimization model, which is aimed at the transmission efficiency and restrained by the power demand as well as the human safety, was built to optimize the design of the receiving coil. The receiving coil of the endoscope capsule was optimized using this model, and experiments verified the validity of the method.  References | Related Articles | Metrics

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Control and Prevention of Ice Disasters in Power Grid with Power Supply Continuity   ZHU Lei, MA Dian-Guang, WANG Sheng-Yong, SHI Zhan-Guo, XIANG Chen, ZHANG Xiu-Bin 2012, 46 (07):  1131-1137.  Abstract ( 2838 )   Save A smart system to control and prevent ice accretion on transmission lines without suspending power supply was designed. Based on image information identification this system uses the technology of highpass and lowpass shunt, sinusoidal pulse width modulation (SPWM) controlled inverter, high frequency current heating, electrically induced mechanical shock and so on to generate high frequency deicing current which has controllable frequency and amplitude. At the same time, the phase of the deicing currents in different transmission lines varies periodically so that the interaction of two transmission lines changes in the manner predesigned. The system takes this advantage to make the transmission line shock in order to accelerate the deicing process. So the system provides a new way to protect the transmission line from the disaster caused by ice with no need to change the existing technical standards of the power transmission and distribution system in most of the region. The indoor experiment shows that the system is able to accelerate the deicing process efficiently. References | Related Articles | Metrics

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Indirectly Measuring Aortic Flow in a Mock Circulatory System HUANG Huan, YANG Ming, WU Shun-Jie 2012, 46 (07):  1138-1141.  Abstract ( 3060 )   Save In mock circulatory systems, the aortic flow is of violent pulsation. Measuring this signal directly with flow meter will limit its applications to mimic different physiological objects, considering the effects of diameter and wall thickness of the tube, the measurement range of flow meters, etc. In order to solve these problems, an indirect method using pressure signal to estimate the pulsatile flow was proposed. The mock circulatory system is first modeled with different Windkessel models. Then the aortic pressure and arterial pressure are considered as the input and observation variable, respectively, to estimate model parameters and aortic flow based on the extended Kalman filter (EKF). The accuracy of flow estimation is evaluated by the root mean square error index. The experimental results show that the fourelement Windkessel model can describe the dynamic performance of the mock circulation system and thus estimate the aortic flow. This paper provides a novel method to measure the aortic flow in testing and evaluating cardiovascular devices. Key words： References | Related Articles | Metrics

Hydraulic Engineering

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The Mixed Energy Storages and the Exploitation of River Estuary CAO Chu-Sheng-1, 2 , ZHANG Cong-Lin-1 2012, 46 (07):  1142-1145.  Abstract ( 2434 )   Save After the sixty years exploitation, the water hydropower resources of some districts are short or have been fully developed. Mixed energy storage is favorable to the development of river estuary. By this kind of exploitation the surplus power may be renewable and is favorable to the sustainable development.    References | Related Articles | Metrics

Communication and Transportation

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Study on Stability Control for Tractor-Helicopter System on Deck WANG Neng-Jian, ZHOU Li-Jie, LIU Hong-Bo 2012, 46 (07):  1146-1152.  Abstract ( 3146 )   Save The problem of enhancing tractor-helicopter system stability through controlling tractor rear steering angles was addressed, when the helicopter is towed by the tractor on the deck. Considering the inertial force on the helicopter traction system produced by coupled roll-pitch-heave motion of ship, a time varying, nonlinear 3DOF tractor-helicopter system dynamic model including steering system was established. To cope with the variation of aircraft parameters and ocean environment, tractor rear active steering controller and front compensative steering controller were designed based on constructive backstepping variable structure control method with the characteristic of steering subsystem taken into account. The simulation results show that the variable structure controllers can control the relative yaw angular velocity between the tractor and aircraft effectively, meanwhile, can follow the reference model and improve the handling of the system; the control system can restrict the effect of the uncertain outer disturbance and parameter perturbations, has strong robustness. References | Related Articles | Metrics

Astronomy,Geoscience

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Research about Sea-floor Engineering Exploration of Marine-Controlled Source Electromagnetic Method LI Hui-1, LIN Jun-2, ZHOU Feng-Dao-2, LIU Chang-Sheng-2, WANG Yan-2, ZHOU Guo-Hua-2 2012, 46 (07):  1153-1158.  Abstract ( 3027 )   Save  Sea-floor controlled source electromagnetic method is employed in the sea-floor engineering and resource exploration. Vertical magnetic dipole device is used for dragging measurement. The influence of induced electromotive force curve caused by overlying seawater and different dipole moments and the theoretical form of cross-section diagram are both analyzed. Coil miniaturization research has been performed. Parameters of magnetic dipole device, which are used to sea-floor detection, can be obtained by calculation and experiments. Submarine model experiments and oil pipeline detection experiments are fulfilled based on the above theoretical study，thus, accurately detecting the seafloor abnormal accidents and the position, depth of oil pipeline. References | Related Articles | Metrics

Physics

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Measurement of Cross-plane Thermal Diffusivity of Thin-Films by Thermal Wave Method SHEN Chao, ZENG Zhi-Gang, SHEN Bin-Jie, HU Zhi-Yu 2012, 46 (07):  1159-1162.  Abstract ( 3181 )   Save Considering the difficulty of measuring cross-plane thermal diffusivity of thin films, a new method of measuring the cross-plane thermal diffusivity of thin films was approached by combining the apparatus of steady-state comparative-longitudinal heat flow (SCHF) method and the one-dimensional thermal wave in Angstr-m method. The propagation of thermal wave was analyzed and the cross-plane thermal diffusivity of thin films was deduced. By this method, three types of thin films samples (PTFE, polyvinylchloride and polypropylene) with various thicknesses ranging from 30 μm-1 mm were tested and this method is reliable. References | Related Articles | Metrics

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Research on the Echo Characteristic of Underwater Small Targets  PAN An, ZHUO Lin-Kai, FAN Jun 2012, 46 (07):  1163-1167.  Abstract ( 2615 )   Save Theory of the article was applied in research of the echo characteristic of underwater small targets，comprising the target strength and the multibeam of short range echo highlight of sonar image emulation using the BKY method which used to forecast the large size targets such as submarines. The theory was tested and verified by the experiment on the lake. It can be concluded that the target strength of small targets changes dramatically with the angle variation. It is difficult to detect underwater small targets owing to the target strength minor. The optimization of line shape is important to conceal property. The BKY method can be applied to forecast the echo characteristic of underwater small targets.  References | Related Articles | Metrics

Architechural Science

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Risk Controlling Technology of Super Deep Excavation in Urban Metro Hub Construction SHEN Wei 2012, 46 (07):  1168-1172.  Abstract ( 2881 )   Save Urban metro hub construction faces a large number of deep excavations in downtown districts which exist many risks. This paper proposes a risk controlling method called “five steps in risk controlling” to eliminate the sources of risks and control the risk events. This method emphasizes that excavation is a systematic project which risks come from every phase, such as investigation phase, design phase, and construction phase. As the final executive of risk controlling, construction side should participate the risk management of the whole course of the excavation project. The five steps in risk controlling mainly include rechecking of the investigation data, negotiation of the design scheme, construction process control, analyzing and feedback of the monitoring data, and the emergency response of the risk events. This method will be helpful for controlling the risks of deep excavation in large metro hub constructing.   References | Related Articles | Metrics