Table of Content

30 May 2015, Volume 49 Issue 05 Previous Issue    Next Issue

Energy and Power Engineering

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Simulation of Bubble Behavior of Cohesive and Non-Cohesive Particles in Fluidization MEI Dengfei,FAN Haojie,TIAN Fengguo,CUI Xuan,ZHANG Mingchuan 2015, 49 (05):  577-582.  Abstract ( 740 )   Save Abstract： The discrete element method (DEM) was applied to study the bubble behavior of type D particles to analyze the formation and the growing up process of the bubble in fluidized bed, and the effect of cohesive forces on bubbles. The results of DEM simulation reveal that the formation of bubbles in fluidized bed is related to fluidizing velocity; the introduction of cohesive force causes the first occurrence of bubbling to shift to a higher fluidizing velocity. Compared with noncohesive particles, cohesive particle fluidization exhibits a smaller bubble size and lower rise velocity. In addition, the pressure and the particle velocity around the bubble are found to be sensitive to the inter-particle force. References | Related Articles | Metrics

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Experimental Study of H2-NSR Performance of Pt/Ba/Ce/γ-Al2O3 Catalyst YANG Wenjie,WEN Yalin,ZHANG Wugao 2015, 49 (05):  583-589.  Abstract ( 647 )   Save Abstract： The perovskite catalyst Pt/Ba/Ce/γAl2O3 was prepared by the improved SolGel method combined with incipient impregnation, and the surface properties were tested. Using the NOx storage reduction circulation test, the impact of the reaction conditions, including reductant concentration, reduction time and space velocity, and components of IC engine exhaust gas represented by CO2 and HC on the performance of NOx storage reduction (NSR) with H2 as reductant were studied. The experimental results indicate that the specific surface area and catalytic activity of Pt/Ba/Ce/γAl2O3 catalyst are favorable; within the scope of the study, with different reductant concentration there is an optimum reduction time when the NOx conversion rate is the highest, and the optimum reduction time decreases when the reductant concentration increases; the increase of reductant concentration accelerates the NOx desorption; if the reductant concentration is too high, some amount of NOx will spill, and the NOx conversion rate will drop; when the space velocity characteristic is perfect, the NOx conversion rate could still maintain 86.9% under high space velocity of 7.0×104 h-1; to some extent CO2 inhibit the NOx storage activity, but the catalyst can be regenerated; using C3H6 to simulate the exhaust HC, C3H6 has a negative effect on the NOx reduction process when the C3H6 concentration is low, however the C3H6 of high concentration could accelerate this process. References | Related Articles | Metrics

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Numerical Analysis of Low-Cycle Fatigue and Damage of a Ultra-Supercritical Steam Turbine High-Pressure Rotor ZHAO Nailong1a,1b,WU Qiong1a,1b，WANG Weizhe1a,1b,ZHANG Junhui2 2015, 49 (05):  590-594.  Abstract ( 675 )   Save Abstract： The axisymmetric high-pressure rotor of a ultra-supercritical steam-turbine was modeled by commercial finite element software Abaqus for assesment of its high temperature strength. The loaded thermomechanical coupling boundary condition, the temperature and stress distributions of the rotor, and the equivalent strain history of key points under cold start-up procedure were analyzed. The fatigue damage of the rotor during a start-up and shut-down cycle was predicted by the Mansoncoffin formula. The results demonstrate that the temperature difference caused by comdensation heat transfer between the surface and center of the rotor is initially large. The rotor is affected more significantly by thermal stress, and uneven heating results in large thermal stress at the initial phase of the start-up procedure, while the stress reduces during the later period of the startup. Furthermore, the maximum fatigue damage occurs on the arc segments of the balance pistons, and the damage value is 1.692×10-4. Consequently, the danger of low-cycle fatigue failure should be ignored in application. References | Related Articles | Metrics

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Idle Emission Characteristics of High-Pressure Direct-Injection Natural Gas Engine LI Menghan1,ZHANG Qiang1,SHAO Sidong2,LI Guoxiang1,LI Junyin2 2015, 49 (05):  595-599.  Abstract ( 739 )   Save Abstract： This paper studied the CO, HC and NOx emission characteristics of high-pressure direct-injection natural gas engine at different diesel rail pressures and gas injection timing by a series of experiments. The experimental results show that, at idle operation, diesel rail pressure has little influence on CO emissions when the gas is injected near top dead center (TDC). CO emissions decrease with the diesel rail pressure when the gas is injected at a certain angle after TDC and increase with the diesel rail pressure when the gas is injected at a certain angle before TDC. The advancing of gas injection results in lower CO emissions at three different diesel rail pressures. HC emissions increase with the rising of diesel rail pressure and reduce with the advancing of gas injection timing, both increasing significantly when the diesel rail pressure rises from 18 MPa to 24 MPa. NOx emissions  increase  with the advancing of gas injection, and increase markedly when the diesel rail pressure rises from 12 MPa to 18 MPa. References | Related Articles | Metrics

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Numerical Simulation of Natural Convective Heat Transfer Characteristics of Nanofluids in an Enclosure Using Multiphase-Flow Model CHEN Yanjun,LI Yuanyang,LIU Zhenhua 2015, 49 (05):  600-607.  Abstract ( 94 )   Save Abstract： The natural convection heat transfer and flow characteristics of nanofluids in an enclosure were numerically simulated using the multiphaseflow model and single phase model respectively. The simulated results were compared with the experimental results from the published papers to investigate the applicability of these models for nanofluids. The multiphaseflow model is mixture model. The effects of various parameters such as Rayleigh number, Grashof number and volume concentration of nanoparticles on the heat transfer and flow characteristics were investigated and discussed. Comparisons of the central velocity profiles between nanofluid and water for various Gr numbers were studied as well. In addition, streamlines contours and isotherms for different volume concentration were analyzed. The results show that a great deviation exists between the simulated results based on single phase model and experimental data on NuRa heat transfer curve, which indicates that the simulation based on single phase model and NS equations cannot reflect the heat transfer characteristic of nanofluid, while the simulated results using multiphaseflow model have good agreement with the experimental data of nanofluid, which means that the multiphaseflow model is more suitable for the numerical study of nanofluid. Moreover,  nanoparticles can significantly enhance the motion of fluid in the enclosure, which is in favor of strengthening the energy transfer in fluid. Besides, nanofluids also show the characteristic of strengthening the convection in the enclosure. References | Related Articles | Metrics

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Exergy Performance Analysis of an Electric Vehicle Heat Pump System Under Variable Conditions SUN Xudong,GU Bo,TIAN Zhen 2015, 49 (05):  608-613.  Abstract ( 100 )   Save Abstract： Based on the experimental data and the first and second law of thermodynamics, outside air temperature and compressor speed, the coefficient of performance (COP) and exergy destruction and exergy efficiency of an electric vehicle heat pump system were deduced by changing conditions involving refrigerant (R134a) charge. The results show that the optimum refrigerant charge is at 400 g. The exergy destruction is within a range of 0.61-1.28 kW. The condenser and the evaporator has a relatively lower exergy efficiency (37.9%-53.1% for condenser and 34.2%-61.8% for evaporator, respectively). Key words： electric vehicle heat pump system (EVHPS); refrigerant charge; variable conditions; exergy performance References | Related Articles | Metrics

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Influence of Dimple Shapes on Turbulent Flow and Heat Transfer FENG Yan,RAO Yu,LI Bo 2015, 49 (05):  614-619.  Abstract ( 130 )   Save Abstract： Dimples are very effective structures to enhance heat transfer. Based on numerical simulations, this paper investigated the heat transfer and friction factor of sphere, eliptical, inclined eliptical and teardrop dimple. Comparisons of the heat transfer and friction factor results obtained by using the Relizable k-ε, SST, and Standard k-ω models with the experimental results indicate that the Standard k-ω model can best predict the flow and heat transfer in the dimpled channels. The heat transfer and flow structure characteristics in the four dimpled channels have been obtained and compared with each other for the Reynolds numbers of 8 500 to 60 000.The Matlab software is used in this paper to process the numerical data to get the heat transfer distribution along the streamwise direction. The study shows that compared to the flat channel, the sphere dimple enhances the heat transfer by 40% and the friction factor by 70%; the eliptical dimple enhances the heat transfer by 30% and the friction factor by 60%;the inclined eliptical dimple enhances the heat transfer by 40% and the friction factor by 60%; and the teardrop dimple enhances the heat transfer by 70% and the friction factor by 100%. Generally speaking, the teardrop dimple has the best heat transfer and overall performance. References | Related Articles | Metrics

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Differential Evolutionary Modeling with Residual Correction and Down-load Characteristic Analysis for Marine Turbocharged Unit NI He,XIAO Hang,ZENG Fanming,SUN Fengrui 2015, 49 (05):  620-625.  Abstract ( 86 )   Save Abstract： For the modeling and operation characteristic analysis of marine turbocharged unit, an improved differential evolutionary modeling method with residual correction was designed in this paper. This method adopted the differential evolution algorithm to identification model parameters based on the mechanistic model of turbocharged unit, and then used the residuals of original data and model outputs to correct errors, which avoided the deviation caused by experience or experimental data under ideal state. Simulation experiments were conducted based on this model and existing supercharged model to studied the dynamic characteristics of turbocharged unit in pastdown load process. The comparsion of the simulation result with the original data proved that the differential evolution algorithm with residual correction could automatically generate dominant model that met realtime and accuracy requirements in a given model space and parameter ranges. Further analysis of simulation results showed that there was ignificant lag of turbocharged unit in the pastdown load process. References | Related Articles | Metrics

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Mixed Thermo-Elastohydrodynamic Lubrication of Connecting Rod Big End Bearing Considering Cavitation and Micro-Elastohydrodynamic Conditions LIU Xiaori，LI Guoxiang，HU Yuping，BAI Shuzhan 2015, 49 (05):  626-632.  Abstract ( 104 )   Save Abstract： Based on multi-body dynamics, the lubrication calculation model was built for connecting rod big end bearing with consideration of mixed thermoelastohydrodynamic, cavitation and micro-elastohydrodynamic conditions. The method to find cavitation erosion region was proposed, the lubrication state was analyzed, and the heat dissipation of frictional power loss was calculated. The results show that the bearing is in a mixed lubrication state, the asperity contact takes place at both edges of upper bearing top; the cavitation erosion position is recognized by the axis orbit, the lube oil fill ratio, the fill ratio rate of change and the hydrodynamic pressure rate of change; the mean frictional power is 0.44 kW; the maximum transient asperity frictional power is only 111.1 mW, and the monitoring of transient frictional power will not accurately recognize the local lubrication state; and the heat conduction is the main way of energy dissipation in big end bearing lubrication. Key words： References | Related Articles | Metrics

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Noise Performance Investigation of Heat Exchanger of Air Condition SUN Kangjie,OUYANG Hua,TIAN Jie,WU Yadong,DU Zhaohui 2015, 49 (05):  633-636.  Abstract ( 95 )   Save Abstract： The behaviors of noise through the heat exchanger of indoor unit at a low-speed free stream were studied by aeroacoustic performance measurements in a semi-anechoic chamber with different velocities and angles. The experimental results indicate that the noise can be generated at particular velocity and angles which are considered as the most important factor that influences the aerodynamic performance of the heat exchanger. With the increasing in the flow velocity, the frequency of noise increases linearly, and there exists a fixed Strouhal number for the given heat exchanger. References | Related Articles | Metrics

Engergy and Power Engineering

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Improvement of SNR of Vibration Response Signal Excited by In-Cylinder Pressure Using Pattern Recognition Method ZHAO Xiuliang,CHENG Yong,WANG Limei 2015, 49 (05):  637-643.  Abstract ( 122 )   Save Abstract： A model was established to describe the response signal excited by reciprocating inertia force. The parameters of the model were identified by the pattern recognition method. The processing results of the experiment data from a 195 diesel engine indicate that the influence of the instantaneous speed could be ignored. A fourthorder model is appropriate to describe the response signal and the data of early stage in compression stroke is suitable for identifying the model parameters. The trend of the processed internal combustion engine vibration velocity remains consistent with that of the pressure rise rate and the correlation between them is improved, which verifies the proposed method. References | Related Articles | Metrics

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Flow and Heat Transfer Performance of Steam Cooling in V-Shaped Ribbed Channels MA Chao,ZANG Shusheng,CHEN Xiaoling,JI Yongbin 2015, 49 (05):  644-650.  Abstract ( 132 )   Save Abstract： The distributions of Nusselt number (Nu) for steam cooling on V-shaped rib roughness channel with different rib angles were measured by an infrared camera for a Reynolds number (Re) range of （6.0 to 17.7)×103. The results show that the heat transfer performance in the region following the upwind side of Vshaped ribs is greatly enhanced. With the rib angle decreasing, the heat transfer performance of steam cooling in the channel increases. The 45° Vshaped rib roughness channel has the best heat transfer performance in all investigated objects. The flow characteristics and pressure loss of steam flow for all investigated channels were also studied by the CFD method and compared with those of air flow in the similar operating conditions. It is concluded that the secondary flow in ribbed channels is induced by the Vshaped rib turbulator. The cooler flow in the core region of the channel provides a supplement to the area, which results in a thermal boundary layer thinning in that region. Therefore the heat transfer performance is enhanced for the Vshaped rib roughness channel. In the same Reynolds number conditions, the pressure loss coefficients for steam flow and air flow are nearly the same, however, the heat transfer performance of steam flow is obviously higher than that of air flow. References | Related Articles | Metrics

Weapon Industry

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Numerical Simulation of Underwater Piston Pulling Launched Missile LIU Chuanlong,ZHANG Yuwen,WANG Yadong,CHEN Cheng 2015, 49 (05):  651-656.  Abstract ( 104 )   Save Abstract： To combine the advantages of each submarines and missiles in combat, the piston pulling mode which was generally used in landbased missiles was ported to underwater missiles launched by submarines. A numerical simulation model coupled calculation of unsteady flow and motion was established to carry out piston pulling launched missile. The process of the missile launched underwater and air while ejecting out of launching tube was calculated by the given initial conditions. The evolution of missile launching flow and motion parameters was given. The simulation results indicate that there is no enough time for the sea water to fill up the space caused by the motion of the missile during the underwater launching process. The unfilled space comes into cavitation, which increases the pressure drag of the missile, thus reducing the velocity of the missile and increasing the time for ejecting out of launching tube. The cavitation around the missile tail raises the uncertainty of the missile hydrodynamic characteristic, and has an adverse effects on the design and controlling of internal ballistics. The impact load on the tail and the bottom of the tube of collapse and perish by the cavitation will pose higher requirements for structure protection of those places. References | Related Articles | Metrics

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Sensitivity Analysis of Affecting Factors for Additional Load of Adaptive Base ZHOU Xiaohe1,REN Jie1,MA Dawei1,ZHU Zhongling1,WANG Xi2 2015, 49 (05):  657-662.  Abstract ( 45 )   Save Abstract： The additional load is one of the most important mechanical performance index of the adaptive base. To research the sensitivity of affecting factors for additional load of the adaptive base, the additional load mechanical model of the adaptive base was established, and the mathematical calculation formula of the additional load was deducted. Besides, the numerical model of the adaptive base was built, the numerical modeling method was verified by the test, and the numerical result was compared with the analytical solution of the additional load. Combining the parametric technology, the multipleinput with the singleoutput neural network method, the sensitivity research for affecting factors of additional load was conducted. The research shows that the minimum diameter D2 in the S bending and the height H from the ground are proportional to the peak value of additional load. The maximum diameter D1 in the S bending, the down bending radius R1 and the upper bending radius R2 of the S bending are inversely proportional to the peak value of additional load. D2, D1 and H are the main affecting factors while R1 and R2 are the secondary affecting factors for the peak value of additional load, and the affecting factors for the additional impact load are D1>H>D2>R2>R1 in order. References | Related Articles | Metrics

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Piezoelectric Actuators for Insect-Like Flapping-Wing Micro Aerial Vehicle CHAI Shuangshuang，ZHANG Weiping，KE Xijun，ZOU Yang，ZHANG Wei，YE Yinan，ZHANG Zheng，HU Nan，WU Fan，CHEN Wenyuan 2015, 49 (05):  663-668.  Abstract ( 165 )   Save Abstract： Flappingwing micro aerial vehicles demand high force, high displacement and low mass actuators. In this paper, the laminated plate theory, the energy method and experimental method were used to derive the displacement and block force, actuator’s equivalent mass, stiffness and damping coefficient. Then the second order lumped parameter model was obtained. The experimental results show that the actual displacement is larger than the theoretical value. According to the transfer function, the bode diagram   was mapped whose resonance frequency is 2.540 kHz. Compared with the theoretical value, the error is 0.5%, which proves that the model is valid. References | Related Articles | Metrics

Mechanical instrumentation engineering

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Quality Analysis of Correlated MultiStage Manufacturing Systems Based on Markov Model XU Rui1,DU Shichang1,REN Fei2,LIANG Xinguang2,LIU Weihong2 2015, 49 (05):  669-674.  Abstract ( 56 )   Save Abstract： In manufacturing systems, the complex parts like astronautical valve are often processed through several correlated stages. It is absolutely of great importance to evaluate and analyze the quality of such correlated multistage systems. This paper, based on the Markov chain method and incorporating iteration, presented an analytical model to evaluate the quality of the correlated multistage system. The model took machine states as well as the quality of the incoming parts into consideration. It emphasized the quality propagation between adjacent stages, revealed the quality changes after each stage and proposed to improve the quality of the final product from the aspect of the parameters of the processing machine. The effectiveness of this model was validated by a case of multistage manufacturing system of astronauticalvalve used in a domestic rocket manufacturing company. Key words： References | Related Articles | Metrics

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Unequal Head Hydraulic Optimal Design and Experiment on a Non-clogging Centrifugal Pump ZHU Rongsheng1,XING Shubing1,LONG Yun2,WANG Xiuli1,HE Bo1,CAO Liang1 2015, 49 (05):  675-680.  Abstract ( 114 )   Save Abstract： In order to make non-clogging centrifugal pump meet the requirement of multiple operating conditions, optimization design of the 100QW110167.5 model pump impeller was done by using the unequal head hydraulic design method. Combining with the CFD numerical simulation technology, the internal flow field of the original scheme and new scheme were analyzed. It shows that the new impeller does work more fully, its flow lines distributed more uniformly and smoothly at different conditions, and the flow condition of the pump is improved. Besides, the optimal model prototype, based on the simulation, was tested. And the results show that the head of the model pump is 16.89 m and the efficiency reaches 83.11% at the rated point, which has exceeded energysaving level product requirement of the centrifugal water pump. At low flow conditions, no saddle area and no intense vibration phenomenon occure, meeting the design requirements. The efficiency curve, between 0.8q and 1.3q of its efficient region, has a wide efficient area. And the nonclogging performance is better than the original scheme. The predicted curve is basically consistent with the experimental one, and the maximum error is 7.56%, indicating that the numerical simulation is accurate. References | Related Articles | Metrics

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An Approach to Fault Diagnosis of Rolling Bearing Using SVD and Multiple DBN Classifiers LI Yanfeng，WANG Xinqing，ZHANG Meijun，ZHU Huijie 2015, 49 (05):  681-686.  Abstract ( 47 )   Save Abstract： A novel approach to fault diagnosis of rolling bearing using singular value decomposition (SVD) and multiple deep belief network (DBN) classifiers was proposed. According to this approach, vibration signals of rolling bearing under different conditions were reconstructed in the phase space and characteristic matrixes were obtained. Then, the characteristic matrixes were decomposed by SVD to get the singular values. After that, all the singular values were used to form a characteristic vector. Finally, a multiple DBN classifiers model was developed to identify the faults of rolling bearing. To confirm the superiority of the proposed approach, it was compared with DBN, BP neural network and SVM. The experimental results indicates that the proposed approach has a better performance in accuracy and efficiency to identify the fault patterns and severity of rolling bearing. References | Related Articles | Metrics

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Calculating Method of Surface Dissipation Factor and Normal Damping TIAN Hongliang，ZHENG Jinhua，ZHAO Chunhua，ZHAO Xinze，FANG Zifan，ZHU Dalin 2015, 49 (05):  687-695.  Abstract ( 102 )   Save Abstract： Calculating equations of surface normal contact stiffness, loss factor and normal contact damping were explored based on the Hertz normal contact mechanics expression and the fractal geometry theory analyzing surface normal contact stiffness, by improving the previous calculating model. The results reveal that the calculating method proposed can better predict the changing laws of normal contact stiffness, loss factor and normal contact damping. The normal contact stiffness increases by decreasing the fractal roughness and increasing the normal contact load, and it increases at first and then decreases with the increase of fractal dimension. Enhancing the fractal roughness and reducing the normal contact load both make the loss factor ascend which decreases first and then increases with the increase of fractal dimension. The loss factor converges to a certain definite value as the fractal dimension approaches 2. The normal contact damping lessens first and whereafter aggrandizes with the augment of fractal dimension, and there exist two inflexions in the variable process. When the fractal dimension is smaller than the first inflection value, the normal contact damping increases with the increase of fractal roughness. When the fractal dimension is in excess of the first inflection value, the normal contact damping decreases with the increase of fractal roughness. The normal contact damping decreases with the increase of normal contact load for D≤1.4. The normal contact damping increases with the increase of normal contact load for D>1.4. References | Related Articles | Metrics

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A Novel Design Method for Impeller of Medium Specific Speed Non-Overload Multistage Centrifugal Pumps MA Yi1,2,MA Zhongqiang1,ZHANG Shengchang1,2,ZHANG Zhihong1,FAN Weigang3,WANG Jinquan3 2015, 49 (05):  695-701.  Abstract ( 95 )   Save Abstract： To meet the demand of the non-overload characteristic of medium specific speed multistage centrifugal pumps, a formula for the design of impeller was derived by using empirical correlations, based on the theory of non-overload. Two pumps, the specific speeds of which were 89.3 and 135.0, were designed using this formula and the traditional formula, and the performance curves were obtained using Fluent. The results indicate that the extreme point of shaft power curve appeares in both of the pumps designed using the derived formula, and the coefficient K, the ratio of the maximal axle power to the power in designed working condition are 1.13 and 1.03, validiting the derived formula. Compared with the pumps designed using the traditional formula, the head of the pumps designed using the derived formula increases by 14.0% and 7.5%, and the efficiency increases by 2.68% and 1.03%. Meanwhile the radial dimension becomes smaller. The derived formulas can be used for medium specific speed non-overload multistage centrifugal pumps. References | Related Articles | Metrics

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Opportunistic Preventive Maintenance Strategy for Series-Parallel System Considering Line Balancing ZHANG Xiaowen,SUN Xiaoming,JIANG Zuhua,HU Jiawen 2015, 49 (05):  702-707.  Abstract ( 95 )   Save Abstract： Proper maintenance schedule is required to improve the profitability and productivity of manufacturing systems. Thus, an opportunistic preventive maintenance model aiming at serial-parallel machining line consisting of much equipment was developed. Considering the specificity of this system, the concept of line balancing was proposed to get a better utilization of the equipment and balance the production capacity of each station. The opportunistic preventive maintenance model was based on reliability and made a target of the minimal maintenance cost. Proper threshold values as well as the maintenance scheme were obtained by Monte Carlo simulation of the model. An applied case shows that the model is practical and efficient to get a proper maintenance schedule for the series-parallel system. References | Related Articles | Metrics

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Scheduling Flexible Manufacturing System Based on Timed Petri Net and Heuristic Search LI Cheng,LI Shuang,FENG Yiping,RONG Gang 2015, 49 (05):  708-713.  Abstract ( 121 )   Save Abstract： The place-timed Petri net was used to model the flexible manufacturing system scheduling problems. Combined with the execution capacity and heuristic search, Petri net can achieve the minimum makespan strategy by expanding the partial reachability tree. The heuristic function for calculating the machine remaining operation time was improved. First, remaining operations for general FMS were classified into two categories to guarantee the optimality. Besides, the remaining time of onprocessing operations was also considered, which improved the lower bound for heuristic function. As a result, the optimal scheduling strategy could be achieved in less effort. Experiment results demonstrate the proposed heuristic function performs better as expected. References | Related Articles | Metrics

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Free-Form Deformation for Reuse of Mesh Models of Finite Element Analysis YU Xiang,NIU Qiang,LIU Wei,ZHOU Xionghui 2015, 49 (05):  714-717.  Abstract ( 131 )   Save Abstract： Meshing, which is very important to the result of finite element analysis (FEA), is often conducted  manually. It takes a long time while the geometry model has to be re-meshed every time if the design is changed. A new method was presented in this paper that helped to reuse FEA meshes to improve efficiency with an extended technology of free-form deformation (FFD). This method generalized the previous FFD by allowing local deformation based on trivariate Bspline and proposing a way to control vertexes of the FFD lattice. A three-level framework was presented that was “geometry feature-FFD lattice vertexesFEA nodes” to realize the reuse of FEA meshes with preserving geometry features continuous to the 2nd derivative and parameterizing mesh models. This approach saved time to re-mesh when the design variables change within a relatively narrow range. The result of a case study of helical gear shaft at the end of this paper shows that this method is able to apply deformation on the FEA meshes directly, keeping topology structures and geometry features stable instead of re-meshing from computer-aided design models. References | Related Articles | Metrics

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Impact of Humidity on Aerosol Thermophoretic Deposition Rectangular Narrow Channel ZHOU Tao1,2,YANG Xu1,2,LIN Daping1,2,FAN Yunan1,RU Xiaolong1 2015, 49 (05):  718-724.  Abstract ( 156 )   Save Abstract： The code of Fortran and Fluent were selected to study thermophoretic deposition of particles in rectangular narrow channel by considering the humidity ratio of air. Meanwhile, an approach of using the code of Fluent to calculate the thermophoretic deposition rate was proposed, and verified by the results of Fortran programming. The results show that the thermophoretic deposition rate increases with the increase of humidity ratio of air. When the humidity ratio is invariant, the thermophoretic deposition rate increases with the decrease of particle size and pressure, and with the increase of temperature gradient. In addition,different thermal properties of different particles lead to differences in thermophoretic deposition rate. Although the method proposed could reflect the law that the thermophoretic deposition rate changes with the humidity ratio, particle size and variation of the pressure, the calculation result is small. Measures  such as improving the humidity ratio of gas and reducing the pressure in the pipe can be taken to increase the deposition rate of fine particles. References | Related Articles | Metrics

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Method for Selection of Temperature Key Points Based on Thermal Error Sensitivity Images and Genetic Optimization ZHAO Haitao1,FENG Wei1,ZHOU Hai1,YANG Jianguo2 2015, 49 (05):  725-729.  Abstract ( 119 )   Save Abstract： The transient temperature fields and corresponding thermal deformations of a computer numerical control (CNC) turning center headstock were simulated using the finite element method. Based on the concept of thermal error sensitivity, the sensitivity images of thermal errors of the turning center headstock were derived from the simulation results. 512 candidate temperature key points were extracted from finite element nodes by using the wavelet image compression technique. According to the principle of the genetic optimization algorithm, the optimization object function was expressed as a flowchart which could be programmed as an Mfile in Matlab. The selection of temperature key points and building matching thermal error models were simultaneously realized. The validation experimental results on the turning center show that the fitting precision of thermal error models built on optimized temperature key points is better than that on arbitrarily selected temperature measuring points. References | Related Articles | Metrics

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Coupling Model of 2-D Variable Zone Storm Surge and Waves for Bohai Bay LI Daming1，LI Yangyang1，PAN Fan2 2015, 49 (05):  730-736.  Abstract ( 160 )   Save Abstract： Based on the theory of 2-D variable zone storm surge equations and the wave action balance equation, a acoupling model combining 2-D variable zone storm surge with the SWAN wave computing model was established, and the effect of the wave-induced radiation stress on 2-D variable zone storm surge for Bohai Bay was studied. Through the simulation of two variable zone storms in this region, the storm surge current field and current process considering and not considering wave-induced radiation stress were obtained and compared with the observation from Tanggu Tide Station. The results show that in relation to the distribution of wind field, the degree of influence for different storm surge was different.The tide process from the coupling model was in good agreement with the observation, considering waveinduced radiation stress and combining  2-D variable zone storm surge with the SWAN wave computing model. The waveinduced radiation stress has a certain effect on the current field near the shoreline. References | Related Articles | Metrics