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    25 March 2015, Volume 43 Issue 3
    Mechanical Engineering
    Hu Guo-qing Gong Xiao-shan Zhou Yong-hong Zou Chong Jahangir Alam
    2015, 43(3):  1-8.  doi:10.3969/j.issn.1000-565X.2015.03.001
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    In order to analyze the performance of silicon pressure sensor influenced by the deformation of sensor substrate,firstly,the stress distribution of pressure sensor quadrate in the thin diaphragm was deduced on the basis of elastic mechanics theory and plate-shell theory,which provided a basis for the arrangement of resisters in strain membrane. Secondly,the effect of substrate deformation on the stress difference of strain membrane was analyzed via a simulation in ANSYS environment. Then,in order to diminish the influence of sensor substrate deformation,an appropriate optimization of substrate structure was conducted,and a comparison of simulation results was made.Finally,experiments were carried out to test the outputs of the sensor before and after optimization. It is indicated that,after the optimization,the largest deformation of sensor chip center reduces from 2. 172μm to 1. 819μm,and the output error decreases from 0. 95% to 0. 60%.
    Cao Biao Li Hai-bo Pang Shao-hui
    2015, 43(3):  9-14.  doi:10.3969/j.issn.1000-565X.2015.03.002
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    Single-phase AC resistance welder provides alternating current similar to sine-wave. Due to the long zero-crossing time and high peak current,welding heating becomes discontinuous and splash occurs easily. In order to solve these problems,a control system for AC resistance welding,which takes DSP(Digital Signal Processor) as the controlling core and is composed of information detection,PWM (Pulse Width Modulation) output control,human-computer interaction,I/O (Input/Output) interface and fault detection circuits,is developed,and the correspond-ing software is also designed to assure system function. By employing PWM control to adjust the primary voltage of welding transformer,a relative continuous output in wide current range is ensured. The control system possesses three feedback control modes respectively in terms of current,voltage and power,provides several output frequen-cies,and implements quick and stable output control in half a period. Thus,both high control precision and adaptive welding process can be achieved.
    Zhu Qiang Xue Jia-xiang Xu Min Dong Chang-wen Wang Lei-lei Heng Gong-chun
    2015, 43(3):  15-20,28.  doi:10.3969/j.issn.1000-565X.2015.03.003
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    “One droplet per pulse”is widely regarded as the best droplet transfer mode for pulsed metal inert gas welding. A peak pulse followed by median pulse in a square wave pulse can enhance the controllability of droplet transfer effectively and improve welding stability as well as seam appearance. In this paper,firstly,instantaneous current and voltage signals were acquired by using a wavelet analyzer. Secondly,current-voltage distribution proba-bility and U-I graphs were obtained by analysis,which were then combined with seam appearance to assess the welding efficiency. Experimental results on 1. 2-mm ER4043 aluminum alloy welding wire show that (1) at the same average current,the adoption of median waveform helps improve the welding quality significantly and form uniform scaly ripples on seam surface; (2) too small median current has no obvious effect on droplet transfer,and only an increase of base current is observed; (3) too large median current results in instability of welding process,and only an increase of peak current is observed; (4) if the median time is too short,the accumulated energy is not enough to control droplet transfer; if the median time is too long,irregular droplet transfer appears and scaly ripples disappear; and (5) a backward median time ranging from 6 to 10ms as well as a current value varying around the mean of peak current and base current may result in stable welding process and bright scaly ripples with excellent regularity and good appearance.
    Li Wei-Guang Yang Qi-jiang Meng Qi-yong Peng Zhe Luo Jian-bin Zhao Wei Luo Jie-xing
    2015, 43(3):  21-28.  doi:10.3969/j.issn.1000-565X.2015.03.004
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    Firstly,according to the lubrication characteristics of tilting pad bearing,a novel three-pad tilting pad bearing with leading edge groove (LEG) was proposed. Secondly,in order to obtain the test parameters of the bearing,a dynamic performance test rig with the functions of automatic data acquisition and real-time data analysis was developed. Then,the temperature characteristics of flooded bearing and LEG bearing were analyzed in a com-parison way,and eight dynamic parameters of tilting pad bearing were obtained respectively via finite difference al-gorithm and frequency sweep excitation test. Finally,the effectiveness of the proposed test method was verified by a comparison between the theoretical results and the test ones. It is found that the developed bearing is of good tempera-ture,stiffness and damping characteristics.
    Zuo Bin Wang Bao-yu Li Zhi Zheng Ming-nan
    2015, 43(3):  29-34,48.  doi:10.3969/j.issn.1000-565X.2015.03.005
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    As gear manu facturing is a continuous production process,not only the continuity and efficiency of manu-facturing but also the reliability of forging tools should be guaranteed in the process of precision forging for manufac-turing gears. In this paper,firstly,three tool design schemes respectively with mandrel,without mandrel-hollow billet and without mandrel-solid billet were proposed for the precision forging of hollow cylindrical gears,and the corresponding forming loads were predicted. Secondly,tooth formation,metal flow,tool stress and forming load were analyzed via finite element simulation. Then,the procedures corresponding to the three schemes were de-signed,and a comparison was made between these three precision forging processes and the conventional cutting process in terms of production efficiency and material utilization. Finally,forging trials for hollow cylindrical gears were conducted to verify the validity of finite element simulation and forming load calculation,and the manufactur-ing process without mandrel-solid billet was proved to be the best for the hot precision forging of gears.
    Du Jin-fu Fang Zong-de Gao Hong-biao Zhang Yong-zhen Zhao Guo-rui
    2015, 43(3):  35-40.  doi:10.3969/j.issn.1000-565X.2015.03.006
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    In order to evaluate the meshing quality of real hypoid gear with cycloid tooth,firstly,the digital gear surfaces that exactly approximate real tooth surfaces are obtained by fitting the measured discrete points with non-uniform rational B-spline (NURBS) curve. Then,on the basis of space meshing theory,a tooth contact analysis (TCA) of digital gear surfaces is carried out,which provides contact patterns the same as the traditional rolling test and transmission error curves that can not be obtained from the traditional test. As a result,actual meshing informa-tion can be relatively fully reflected. Finally,the feasibility of the proposed method is verified through a comparison between digital gear surface TCA and rolling test of a high-speed axle gear pair.
    He Zhan-shu Wang Pei-zhuo Li Da-lei Li Yan-min Ma Yong-tao Tang Yong
    2015, 43(3):  41-48.  doi:10.3969/j.issn.1000-565X.2015.03.007
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    Firstly,a functional surface structure with regular pores for heat transfer,namely cross-connected micro-channel mesh plate (CCMMP),was designed and fabricated via multi-cutter milling. Secondly,three pore charac-teristic parameters,namely porosity,specific volumetric surface area and specific weight surface area,were theoretically calculated,and the effects of microchannel interval,depth and width on these three parameters were investigated. Then,CCMMPs were applied to a plate heat exchanger to analyze the pressure drop and the heat transfer performance affected by volume flow,porosity and specific volumetric surface area by experiments. The re-sults show that (1) the porosity ranges from 10. 9% to 88. 0% and the specific volumetric surface area ranges from 2.89mm-1 to 6.40mm-1 if the interval,depth and width of microchannels are all adjusted correctly; (2) CCMMPs quadruple the heat transfer performance; and (3) high porosity and large specific volumetric surface area are favor-able to heat transfer.
    Ding Ya-dong Chen Bai Wu Hong-tao Shen Hao-yu
    2015, 43(3):  49-56.  doi:10.3969/j.issn.1000-565X.2015.03.008
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    As the identification equations for robots’dynamic parameters become very complicated with the increase of joints,it is difficult to obtain accurate equations of dynamic parameters when a robot is of more than four joints.In order to solve this problem,a step-by-step identification method is proposed. In this method,less inertial parame-ters should be identified in each step,which results in simpler identification equation,more efficient calcu-lation and smaller accumulative error. Therefore,the parameter estimation can be achieved quite well for the robots with more than four joints. In order to validate the effectiveness of the proposed step-by-step identification method,a robot with six degrees of freedom is taken as an object to conduct the corresponding identification experiments.The results demonstrate that the proposed method is a simple but effective way to obtaining the key dynamic parame-ters of robots without changing their key dynamic characteristics.
    Electronics, Communication & Automation Technology
    Ma Li-hong Huang Yin Li Jian-hui
    2015, 43(3):  57-65.  doi:10.3969/j.issn.1000-565X.2015.03.009
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    A multi-feature joint dictionary (MFJD) is suggested to improve the structural distinction in dictionary training and to accelerate the atom matching in sparse reconstruction. Firstly,two dictionaries branched respectively for edge-and texture-descriptions are created using gradient and LBP operators. Secondly,tree structures are intro-duced to represent the hierarchical clustering of atoms,which leads to a quick atom searching. Then,bilateral total variation (BTV) regularization is employed to achieve the optimal resolution. Experimental results show that,in comparison with the sparse coding super-resolution reconstruction (SCSR) algorithm,MFJD averagely improves the PSNR,MSSIM and FSIM of an image by 0. 2424dB,0. 0043 and 0. 0056,respectively,and reduces the recon-struction time to approximately 22.77% of that of SCSR algorithm owing to the reduction of dictionary dimensionality.
    Zhao Jun-hong Ai Wei Zhu Xue-feng
    2015, 43(3):  66-71.  doi:10.3969/j.issn.1000-565X.2015.03.010
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    This paper deals with an image analysis method,namely passive forensics,to detect copy-move forgery,the most popular manipulation in digital tampered images. On the basis of ASIFT (Affine Scale-Invariant Feature Transform) and circle projection features,a new algorithm is proposed to detect copy-move forgery in images. The results show that the adoption of ASIFT is effective only in finding the forgery area in a tampered image with obvious corner information,while the adoption of improved circle projection features is effective only in finding the forgery area in a tampered image without such obvious corner information as random textures and flat areas. Thus,it comes to the conclusion that the combination of ASIFT and improved circle projection features is more effective for the pas-sive forensics of copy-move forgery.
    Li Hong-tao Wei Xiao-Dong Hu Bin-Jie Zhang Hong-lin Zeng Wei-sen
    2015, 43(3):  72-77.  doi:10.3969/j.issn.1000-565X.2015.03.011
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    Proposed in this paper is a novel orthogonal Hybrid coupler applied to multi-beam electronic toll collec-tion (ETC) systems. In this coupler,two common frequency bands of ETC system including 2. 4 GHz (2. 2 ~2. 6GHz)and 5. 8GHz (5. 4 ~ 6. 0 GHz) are covered to adapt different working frequency bands,and different power distribution characteristics are endowed in the two frequency bands,that is,equally orthogonal output in 2. 4GHz band and orthogonal output in the range of 0. 5 ~7dB in 5. 8GHz band. The proposed divider is of broad bandwidth and small circuit size,and,it is proved feasible due to the good agreement between real test results and simulation data.
    Zhong Wei-zhi Zhong Dan-dan Jing Qing-feng Liu Xin
    2015, 43(3):  78-83.  doi:10.3969/j.issn.1000-565X.2015.03.012
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    In order to overcome the high iteration load and error diffusion existing in maximum entropy method (MEM) and to improve the prediction accuracy of ESPRIT algorithm subjected to autocorrelation function estima-tion,a flat fast-fading channel prediction algorithm on the basis of extended Prony algorithm is proposed. By means of extended Prony algorithm,complex roots can be obtained via least square fitting and higher algebraic equations without estimating autocorrelation function,batch computation becomes possible,and thus both the prediction accu-racy and the computation efficiency improve. Theoretical and simulated results show that,in comparison with MEM and ESPRIT algorithms,extended Prony algorithm provides higher prediction accuracy,3 ~5 dB advantages at the same prediction accuracy,more steady performance and higher operation efficiency.
    Li Dong-wu Pei Chang-xing
    2015, 43(3):  84-89.  doi:10.3969/j.issn.1000-565X.2015.03.013
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    Proposed in this paper is a new diversity receiving algorithm for cooperative communication systems.Firstly,space-time block coding is carried out by relay nodes to acquire a transmission signal. Secondly,spatial and frequency domain equalization is executed to the received signal by means of fast Fourier transform (FFT) at the receiver. Then,the transmitted signal is estimated by hard decisions after inverse FFT operations. In this algo-rithm,a new scheme combining decision feedback and interference cancellation is adopted to acquire cooperative diversity gain of the relay and to reduce the signal-to-noise ratio (SNR) loss in the process of equalization. Thus,transmission quality of cooperative communications is improved. Simulated results show that the proposed algorithm decreases the magnitude of bit error rate from original 10-2 to 10-3 when SNR is 12dB.
    Zhou Xiong Feng Sui-li
    2015, 43(3):  90-97.  doi:10.3969/j.issn.1000-565X.2015.03.014
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    In order to solve the problems existing in the deployment and operation of femtocell base stations as well as in the spectrum resource share between femtocells and macrocells,an optimal allocation and pricing strategy for spectrum resources is proposed on the basis of Stackelberg game. By modeling the game between base stations and users,the relationship between spectrum price and user demands is analyzed. Then,by modeling the game between macrocells and femtocells,an optimal strategy of spectrum allocation and pricing in various scenes is proposed for two-tiered hierarchical cellular networks. This strategy allocates spectrum resources between macrocells and femto-cells reasonably,maximizes their utility,effectively inspires operators and owners to deploy femtocell base stations,and promotes the process of green communication.
    Lan Lin-feng Song Wei Shi Wen Peng Jun-biao
    2015, 43(3):  98-102.  doi:10.3969/j.issn.1000-565X.2015.03.015
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    In order to meet the requirements of novel display technologies such as flexible active-matrix organic light-emitting diodes (AMOLED),thin film transistors (TFTs) are fabricated,with low-temperature solution-pro-cessed ZnO as the semiconductor layer and with electrochemical oxidized alumina neodymium as the gate dielectric layer. In the preparation of ZnO semiconductor layer,carbon-free aqueous Zn(OH)x-(NH3)y(2-x)+ solution with low cost and fabrication simplicity is employed,and,more importantly,the energy for metal-ammine dissociation and ZnO formation is rather low thanks to the highly activated hydroxyl radicals. As a result,ZnO polycrystalline films can be realized at a relatively low temperature,namely 180℃. The proposed low-temperature solution-pro-cessed ZnO fabrication method combining with room-temperature electrochemically-oxidized gate dielectric layer helps achieve high mobility up to 0. 9 cm2 /(V·s),and is completely compatible with flexible substrates,so that it meets the demand of flexible electronic devices well.

    Li Xiang-yang Tian Sen-ping
    2015, 43(3):  103-110.  doi:10.3969/j.issn.1000-565X.2015.03.016
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    For a class of uncertain nonlinear time-varying systems with arbitrary initial states and aperiodic bounded disturbance,an iterative learning control (ILC) method on the basis of boundary layer is presented. In this me-thod,boundary layer is designed as a decaying exponential function with residual width,the arbitrary initial state problem of ILC is transformed into a zero initial state problem by the designed boundary layer,and learning laws of periodic and aperiodic terms are designed for periodic and aperiodic disturbances,respectively. On the basis of these two laws,an ILC algorithm is presented,and the corresponding theorem is given with detail proof through Lyapunov-like approach. Simulated results show that the proposed algorithm is effective and is capable of conver-ging trajectory tracking errors to boundary layer.
    Huang Dao- ping Qiu Yu Liu Yi- qi Li Yan
    2015, 43(3):  111-120,129.  doi:10.3969/j.issn.1000-565X.2015.03.017
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    Environmental Science & Technology
    Cheng Xiang-ju Kuang Yun-qi Lin Wen-xin Xie Jun Xu Ting-da
    2015, 43(3):  121-129.  doi:10.3969/j.issn.1000-565X.2015.03.018
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    In order to achieve dynamic balance in a re-circulating aquaculture system (RAS),the idea of“oppo-sing flow”and the principle of Venturi air entrainment were adopted,and 15 experimental conditions were deter-mined to investigate the effect of opposing flow on the aeration in water with different Venturi settings. The results show that the volumetric mass transfer coefficient of oxygen is proportional to water flow rate,but is inversely pro-portional to Venturi setting depth at the same flow rate. By comprehensively considering the aeration effect and the re-circulating opposing flow characteristics,it is suggested that Venturi aerator should be set as A—B stagger layer at the beginning and the end of cultivation,while it should be switched to A—C stagger layer in the mid-term culti-vation.
    Zhang Yan-zhuo Li Jun Li Yun Chen Guang-hui Bian Wei
    2015, 43(3):  130-136,150.  doi:10.3969/j.issn.1000-565X.2015.03.019
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    The ability of aerobic granular sludge (AGS) to adsorb sunset yellow (SY) in aqueous solutions is inves-tigated,and the adsorption process affected by pH value,adsorbent dosage,initial SY concentration and tempera-ture is explored. The results show that (1) pH value is an important influencing factor of adsorption efficiency;(2) the best adsorption is achieved at a pH value of 2,an AGS dosage of 2 g/L and a temperature of 35℃;(3) the equilibrium adsorption capacity is positively correlated with the initial SY concentration; and (4) the equilibrium adsorption data accord the Langmuir model and the pseudo-second-order kinetic model well,with a saturated SY adsorption capacity of 142. 86 mg/L. Thermodynamic analysis indicates that the adsorption process is spontaneous and endothermic for dye,and that low SY concentration benefits the adsorption affinity. Thus,it comes to the conclusion that AGS can be used as a low-cost adsorbent for the removal of SY dye from wastewater.
    Guan Xiao-hong Xin Xiao-yan Gao Nai-yun Tan Chao-qun Zhuang Zhen-zhen
    2015, 43(3):  137-142.  doi:10.3969/j.issn.1000-565X.2015.03.020
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    This paper deals with the degradation of acetaminophen by Fe2+-activated peroxymonosulfate( PMS) in aqueous solution. By investigating the effect factors,reaction kinetics,mineralization and radical( SO-·4or OH·)identification,two degradation stages,one is fast and the other is slow,are discovered,and an optimal concentration ratio of PMS to Fe2+,namely 1. 5∶1,is determined for achieving the highest degradation rate. Moreover,it is found that the optimal pH value is 5. 0,and that relatively high PMS and Fe2+dosages help achieve a mineralization rate more than 55%. ESR test indicates that SO-·4 and OH·appear in the degradation process and play their important roles; and that SO-·4 and OH·appear after 3 min from the reaction initiation,then the quantity of OH·decreases and then vanishes,so that SO-·4 is the main radical for the slow degradation stage.
    Yu Cheng-long Huang Bi-chun Yang Ying-xin
    2015, 43(3):  143-150.  doi:10.3969/j.issn.1000-565X.2015.03.021
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    Low-temperature NH3 -SCR is an efficient technology with high economic value and broad application prospect for transforming NOx into N2 below 200 ℃. Great attention has been paid worldwide to develop low-temperature SCr denitration catalysts with high activity and strong resistance to sulfur dioxide and water,which is also crucial for the development and application of low-temperature SCr technologies. Molecular sieves are of ex-cellent adsorption performance,suitable surface acidity,good shape selectivity and flexibility,as well as the capa-bility of introducing transition metal elements. This paper reviews the research progress of molecular sieves used in denitration catalysts for low-temperature NH3 -SCR,and emphasizes the low-temperature selective catalytic reduction performance,the sulfur dioxide and water resistance,as well as the reaction mechanism of ZSM-5,SAPO-34,SBA-15,MCM-41 and beta molecular sieve. Moreover,the application of calculating simulation to the design of molecular sieve catalysts is introduced,some problems existing in the application of molecular sieves to low-tempe-rature NH3-SCR are analyzed,and the future research trend is also pointed out.
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