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15 May 2019, Volume 40 Issue 5 Previous Issue    Next Issue
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Information & Control

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Frequency-Based Seed Selection Algorithm for Read Mapping MA Hai-tao， QI Shi，YU Chang-yong， ZHAO Yu-hai 2019, 40 (5):  609-613.  DOI: 10.12068/j.issn.1005-3026.2019.05.001 Abstract ( 808 )   HTML   PDF (509KB) ( 703 )   The selection of the optimal seed(that is， the seed with the lowest frequency)is a complex calculation problem， which often takes a long time. A frequency-based merge seed selection(FMSS) algorithm is proposed， which can efficiently select the suboptimal set of seeds and improve the performance of existing mapping tools. In the experiment， FMSS was compared with the average seed selection method and the optimal seed solver(OSS). Experimental results show that FMSS can select the optimal set of seeds close to OSS， and the time cost of FMSS is far lower than that of the OSS algorithm. The FMSS algorithm is more suitable for seed selection in terms of time cost and seed selection quality. References | Related Articles | Metrics

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Facial Recognition Algorithm Based on Multi-universe Parallel Quantum Genetic Neural Network LI Hai-peng， LI Jing-jiao， JIN Shuo-wei， YANG Dan 2019, 40 (5):  614-618.  DOI: 10.12068/j.issn.1005-3026.2019.05.002 Abstract ( 650 )   HTML   PDF (628KB) ( 702 )   In order to solve the problem that the process of cross and mutation in traditional genetic algorithm is too cumbersome， and the extreme value judgment and the convergence rate is limited， a parallel quantum genetic algorithm(QGA) is proposed to optimize the weights of the neural network. The concept of quantum computing is firstly introduced. In the process of quantum computation， the quantum rotation gate is used to train the chromosomes. Then the quantum cross is introduced to overcome the precocious convergence and to avoid the cumbersome cross and mutation process in the genetic algorithm. Finally， the parallel convolution neural network is designed and implemented. The parallel quantum genetic algorithm is used to optimize the weights of the convolution neural network， and a facial recognition system based on parallel quantum genetic neural network is realized. Experimental results show that compared with the original genetic algorithm， the quantum genetic neural network algorithm has obvious improvements in terms of robustness and processing speed. References | Related Articles | Metrics

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Observer Design for Uncertain Fractional-Order Linear Systems with Sensor Fault ZHANG Xue-feng， LIU Bo-hao 2019, 40 (5):  619-624.  DOI: 10.12068/j.issn.1005-3026.2019.05.003 Abstract ( 684 )   HTML   PDF (366KB) ( 684 )   The observer for the uncertain fractional-order system with sensor fault and system measurement noise is developed. By using the method of augmented matrix and the invariant property of matrix rank， the uncertain fractional-order system is augmented into the singular fractional-order uncertain system. Based on the linear matrix inequality approach of stability criterion for fractional-order systems， an asymptotic stability criterion of the error dynamic system with fractional-order satisfying 1 References | Related Articles | Metrics

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Effects of Sampling Frequency and Data Length on the Central Aortic Waveform Reconstruction XU Li-sheng， JIANG Zhi-hao， YAO Yang， LIU Wen-yan 2019, 40 (5):  625-629.  DOI: 10.12068/j.issn.1005-3026.2019.05.004 Abstract ( 686 )   HTML   PDF (652KB) ( 623 )   Non-invasive CAP(central aortic pressure)reconstruction is mostly based on the auto regressive eXogenous(ARX)model or Fourier transform in transfer function method， without considering the factors such as sampling frequency and data length. Based on the ARX model and the Fourier transform， the error of reconstruction CAP was analyzed for studing the effects of sampling frequency and data length on the CAP. The results show that when sampling frequency is 100Hz and data length is greater than 3s， CAP can be better reconstructed by ARX model(RMSE:(306.6±80.0)Pa; FIT: 89%). The algorithm based on the Fourier transform is insensitive to sampling frequency. When data length is set to 6s， the reconstructed CAP has a better performance(RMSE:(493.3±320.0)Pa，FIT:84%). References | Related Articles | Metrics

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Two Novel Algorithms Based on Extension Rule for Solving #SAT Problem LYU Shuai， ZHANG Tong-bo， WANG Qiang， LIU Lei 2019, 40 (5):  630-635.  DOI: 10.12068/j.issn.1005-3026.2019.05.005 Abstract ( 815 )   HTML   PDF (364KB) ( 636 )   A novel #SAT solver NCER based on extension rule is proposed， which adds heuristic strategy on #ER algorithm. The heuristic strategy chooses the longest clause in current set of clauses every calling procedure to reduce the maxterm space， and it helps decrease the frequency of recursive invocation to enhance the efficiency of solving. Besides， a mixed model counting algorithm called NCDPER is proposed by combining NCER algorithm and CDP algorithm， to overcome the poor performance on instances where complementary factor of the #SAT solvers is small using the extension rule. NCDPER integrates advantages of NCER algorithm and CDP algorithm. According to the experimental results， NCER has a significant improvement over previous #SAT solvers on all 85 random SAT instances. The #SAT solvers proposed are compared with state-of-the-art #SAT solvers using extension rule， and the results show that the proposed #SAT solvers have better performances. References | Related Articles | Metrics

Materials & Metallurgy

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Research and Application of Deep Learning Method for Plate Ultra Fast Cooling ZHANG Tian， ZHANG Zi-hao， TIAN Yong， WANG Zhao-dong 2019, 40 (5):  635-640.  DOI: 10.12068/j.issn.1005-3026.2019.05.006 Abstract ( 691 )   HTML   PDF (655KB) ( 905 )   The heat transfer coefficient (HTC) is a key parameter to determine control precision in a cooling-controlled model. However， the correction for the HTC isn’t always stable and robustness by a traditional self-learning method. In order to solve such problems，the deep neural networks for the self-learning HTC were built based on the deep learning technology. The optimization of hyper parameter and the selection of algorithm in the network frame are studied. Therefore， the stability of the cooling control model can be greatly enhanced. The application of the 3500mm plate mill plant proves the better accuracy and robustness of the model， which can meet the requirements of actual on-site production. References | Related Articles | Metrics

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Numerical Simulation to Optimize Heating System in Vacuum Carburizing Furnace LIU Jing， LI Jia-dong， WANG Hao-jie， WANG Zhao-dong 2019, 40 (5):  641-646.  DOI: 10.12068/j.issn.1005-3026.2019.05.007 Abstract ( 763 )   HTML   PDF (962KB) ( 867 )   In order to optimize the structure of heating system and improve heating efficiency， a numerical model was built to study heating transfer in vacuum carburizing furnace using COMSOL finite element software. The effects of key structural parameters such as number， length and distribution radius of graphite heating tube on the heat flux of workpiece surface and the temperature distribution of effective heating zone were studied. The results show that when the number， length and distribution radius of heating tubes decrease， the heat flux density increases and the heating efficiency improves. Moreover， when setting the number of heating tubes into even， decreasing the length and increasing the distribution radius can improve the temperature uniformity in effective heating zone. The findings can provide guidelines to optimize the structure of heating system in vacuum carburizing furnace. References | Related Articles | Metrics

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Experimental Study on Bending Capacity of Copper/Steel/Copper Cold Rolled Composite Strip CHEN Jing-qi， LIU Xiang-hua， YAN Shu， YU Qing-bo 2019, 40 (5):  647-652.  DOI: 10.12068/j.issn.1005-3026.2019.05.008 Abstract ( 735 )   HTML   PDF (1120KB) ( 828 )   Using Q345 steel strip as the matrix and T3 pure copper as cladding material， a copper/steel/copper composite strip can be produced by a process route of cold-rolled composing-intermediate annealing-cold-rolled thinning-post rolling. The effects of the strip thickness and annealing temperature on the bending capacity of the composite strip were investigated by repeated bending experiments. It is found that the bending capacity of the composite strip mainly depends on mechanical interaction during the cold-rolled composing and the diffusion features during annealing. When the strip thickness becomes thinner during rolling， the bending capacity of the cold-rolled strip almost linearly increases. Moreover， the annealing process improves the bending capacity of the strip as well. The results shows that the bending capacity has an exponential relationship with annealing temperature. References | Related Articles | Metrics

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Preparation and Modification of Three-Dimensional ZnO-Based Ethanol Gas Sensitive Materials YU Hui-min， WANG Shuo， LI Qi-wei， LI Jian-zhong 2019, 40 (5):  653-658.  DOI: 10.12068/j.issn.1005-3026.2019.05.009 Abstract ( 622 )   HTML   PDF (959KB) ( 731 )   Nanosized ZnO with a special three-dimensional (3D) structure was prepared by a solvothermal method using carbamide as the precipitant and then an ZnO-based ethanol gas sensitive material was obtained successfully by changing the doping amount of Ag. The phase structure and microstructure of the obtained products were characterized by XRD and SEM and the gas sensing property was tested using the static volumetric method. The results show that the gas sensing performance of 3D ZnO-based ethanol can improve effectively by doping Ag， in comparison with pure 3D-ZnO. When the amount of doping Ag is 1.5% and the volume fraction of ethanol is 0.1%， the value of gas sensor is up to 31.61， the operating temperature decreases from 350℃ to 200℃ and the response/recovery time are shorted to 10s/10s. Meanwhile， the selectivity to ethanol gas is enhanced. References | Related Articles | Metrics

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Optimization of Continuous Casting Secondary Cooling Based on An Enhanced Multi-objective Genetic Algorithm ZHAI Ying-ying， LI Ying， AO Zhi-guang 2019, 40 (5):  658-662.  DOI: 10.12068/j.issn.1005-3026.2019.05.010 Abstract ( 703 )   HTML   PDF (473KB) ( 671 )   An enhanced multi-objective genetic algorithm is adopted to optimize secondary cooling process， which uses the probability method to select the operator and calculates crossover and mutation probability dynamically according to the fitness value. A better global optimal solution is achieved and the algorithm precision and overall performance improve greatly. In the secondary cooling optimization process， the model based on solidification heat transfer is solved by the variable spacing difference method. Compared to particle swarm algorithm and the traditional multi-objective genetic algorithm， the enhanced multi-objective genetic algorithm has the highest search efficiency and the minimum value function. In industrial applications， the optimized secondary cooling process can reduce the total consumption of water by 10% and improve the quality of casting billet， which meet the requirements of energy saving and consumption reduction. References | Related Articles | Metrics

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Effects of Microwave Pretreatment on the Grinding Kinetics of Vanadium Titano-Magnetite WANG Jun-peng， JIANG Tao， LIU Ya-jing， XUE Xiang-xin 2019, 40 (5):  663-667.  DOI: 10.12068/j.issn.1005-3026.2019.05.011 Abstract ( 698 )   HTML   PDF (1724KB) ( 698 )   The specific rate of breakage(S○1)and primary breakage distribution(Bi,j)of untreated and microwave-treated vanadium titano-magnetite(VTM) with different particle size were investigated using grinding kinetics， and the variations of surface topography and phase composition of ground products were analyzed. The results show that the breakages of both untreated and microwave-treated VTM obey the first-order grinding kinetics. The S○1 of microwave-treated VTM is higher than that of untreated ore and the S1 increment increases with increasing particle size. The primary breakage distribution parameters(γ) are dependent upon the feed particle size. The γ value of Bi,j of microwave-treated VTM is less than that of untreated ore. The SEM analysis shows that the ground products have smaller particle size and rougher surface after microwave treatment. The XRD analysis shows that microwave-treated VTM has stronger diffraction peaks and larger amounts of gangue phases after ball mill， compared to those of untreated ore， which indicates that the degree of dissociation of ore is improved. References | Related Articles | Metrics

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Preparation of Nano Cuprous Oxide by Plasma Induced Cathode Discharge Electrolysis SHEN Ling-ling， ZHAO Bo， XU Jun-li， SHI Zhong-ning 2019, 40 (5):  668-672.  DOI: 10.12068/j.issn.1005-3026.2019.05.012 Abstract ( 948 )   HTML   PDF (781KB) ( 851 )   Nano cuprous oxide(Cu2O)powders were prepared by plasma induced cathode discharge electrolysis in CuSO4 solution， and the components and morphology of the prepared particles were investigated by various concentrations， electrolysis voltage and time. The results showed that a higher concentration of solution had a positive effect on the formation of Cu2O phase. As the discharge time extended， the particles aggregated and the size increased from 100nm to 400nm. Increasing the voltage was beneficial for the refinement of particles from 200nm to 40nm.Emission spectrum analysis indicated that there existed hydroxyl radicals and Cu atoms in plasma emission area， which was suggested that the formation mechanism of Cu2O. Theoretical calculation showed that excitation temperature， the electric field intensity and the arc column jet velocity was 9563K， 2.4×105V/m， and 73m/s， respectivively. References | Related Articles | Metrics

Mechanical Engineering

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Research on Dynamic Load Identification Based on Explicit Wilson-θ Method FAN Yu-chuan， ZHAO Chun-yu， LU Yan， ZHANG Yi-min 2019, 40 (5):  673-677.  DOI: 10.12068/j.issn.1005-3026.2019.05.013 Abstract ( 591 )   HTML   PDF (808KB) ( 849 )   The explicit expression of Wilson-θ numerical algorithm for multi-dofs(degree of freedoms) dynamic equation is derived， as well as an explicit Wilson-θ dynamic load identification algorithm is proposed， avoiding the iteration error while keeping the characteristics of the implicit iteration algorithm. The algorithm is unconditionally stable when applying appropriate θ value. The recognition effect of the algorithm is verified by an example and an experiment of a cantilever beam， and the results were compared with those from the traditional state space method. The results show that the algorithm not only can accurately identify the rectangular load， the harmonic load and the random load， but also has higher recognition accuracy than state space method. References | Related Articles | Metrics

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Reliability Sensitivity Analysis Based on Random Load and Strength Degradation YANG Zhou， GUO Bing-shuai， ZHANG Yi-min， GU Luo-wei 2019, 40 (5):  678-683.  DOI: 10.12068/j.issn.1005-3026.2019.05.014 Abstract ( 661 )   HTML   PDF (460KB) ( 848 )   In order to solve the dynamic reliability problem caused by random load and strength degradation， the load and strength are considered as stochastic processes simultaneously. The maximum equivalent load is obtained by using the theory of sequence statistics， the strength degradation process of mechanical parts is described by Gamma process， and the dynamic reliability model is established. Consequently using the stochastic perturbation theory and the four-order moment technique， the solution formula for the dynamic reliability sensitivity is derived， solving the sensitivity problem of the parameters from arbitrary distribution. For variation， a dynamic reliability model for screw bolts was established. The dynamic curves of the sensitivity of each parameter variable vs. time were calculated with the said model， and were also verified by Monte Carlo method. The results show that the established model indicates the rule of reliability change of mechanical parts vs. time accurately. References | Related Articles | Metrics

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Study On the Chatter Stability of Robotic Milling Based on the Probability Method LIU Yu， HE Feng-xia 2019, 40 (5):  683-687.  DOI: 10.12068/j.issn.1005-3026.2019.05.015 Abstract ( 777 )   HTML   PDF (892KB) ( 891 )   The reliability method was introduced into the prediction of modal coupling chatter in robotic milling. Firstly， the reliability model was established and the limit state equation was obtained. Secondly， the fourth-order moment method was used to calculate the reliability and sensitivity to analyze the influence of various parameters on the milling stability. Finally， an example was given based on the engineering background of robotic milling bone. The results showed that the two-degree-freedom stiffness， cutting force coefficient and feeding direction of the robot will affect the stability of the milling process. Within a certain range， increasing the stiffness in X divection，reducing the stiffness in Y direction， reducing the cutting force coefticient and choosing the feed divection resonably are helpful to avoiding modal coupling chatter. The system is more sensitive to the change of cutting force coefficients than to the stiffness in X and Y directions， and has more significant benefit influence on stability. References | Related Articles | Metrics

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Vibration Characteristics Study for the Hard Coating Blisk Using Finite Element Method GAO Feng， SUN Wei， GAO Jun-nan 2019, 40 (5):  688-693.  DOI: 10.12068/j.issn.1005-3026.2019.05.016 Abstract ( 805 )   HTML   PDF (883KB) ( 749 )   Vibration characteristics of hard coating blisk and the damped vibration reduction of hard coating were investigated using finite element method. Firstly， the equation of motion of hard coating blisk was achieved according to the energy method and the Mindlin plate theory and the complex modulus theory; then， modal characteristics and forced vibration response of hard coating blisk were solved; finally， a blisk with NiCoCrAlY+YSZ deposition hard coating on both sides of blades was taken as study case， the finite element model of hard coating blisk was validated by the theoretical analysis and experimental test. The results reveal that the NiCoCrAlY+YSZ hard coating has weak effect on natural frequencies， but a strong damping effect on the blisk， and forced responses of the blisk were suppressed remarkably by the NiCoCrAlY+YSZ hard coating. References | Related Articles | Metrics

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Piston Wind Speed Calculation Method and Analysis of Influence Factors for Subway Tunnel LUO Zhong， HAN Gui-xin， ZHAO Kai， HUANG Shu-zhi 2019, 40 (5):  694-699.  DOI: 10.12068/j.issn.1005-3026.2019.05.017 Abstract ( 874 )   HTML   PDF (627KB) ( 1217 )   To avoid damages by the piston wind to the safty doors and AD light boxes in subway tunnels， the aerodynamic characteristics of subway tunnel with and without shaft were analyzed， one-dimensional Bernoulli equations and fluid continuity equations between tunnel sections were established， the numerical calculation model of the piston wind under different tunnels were analyzed， the simulation model established by SES software and calculation model results were also verified. The principal factors affecting the piston wind speed are studied. The results show that the piston wind speed is proportional to the train speed， the length of the train and the smoothness of the train surface. The height， the section area and the position of the air shaft have little effect toward the piston wind speed. The proposed numerical calculation model can be used for the simple calculation of the piston wind speed in actual projects. References | Related Articles | Metrics

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Analysis of Bolted Joint Rotor System with Uncertain Axial Stiffness LI Yu-qi， LUO Zhong， LI Jiang， HOU Xiao-jie 2019, 40 (5):  700-705.  DOI: 10.12068/j.issn.1005-3026.2019.05.018 Abstract ( 615 )   HTML   PDF (577KB) ( 690 )   The stiffness uncertainty of bolted joint structure plays an important role in dynamic characteristics of the rotor system. The influences of the uncertainty of the axial stiffness on the vibration behaviors of the bolted joint rotor system are studied. Firstly， the motion equations of the bolted joint rotor system are established based on the finite element method， and then the stochastic dynamic model with uncertainty of axial stiffness of bolted joint structure is obtained by the nonintrusive polynomial expansion method. Finally， the dynamic characteristics is illustrated. The results show that the axial stiffness uncertainty will affect the critical speed and the steady response amplitude of the rotor system. The response amplitude of the disk in the vertical direction decreases as the increasing of axial stiffness uncertainty. The results can provide a theoretical reference for the design of the bolted joint rotor system. References | Related Articles | Metrics

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Cutting Mechanism Research and Experimental Study on Axial Ultrasonic Vibration Assisted Drilling TIAN Ying-jian， ZOU Ping， CHEN Shuo， WEN Quan 2019, 40 (5):  705-709.  DOI: 10.12068/j.issn.1005-3026.2019.05.019 Abstract ( 693 )   HTML   PDF (672KB) ( 839 )   An axial ultrasonic vibration assisted drilling method was proposed for solving problems such as difficulties in chip breaking， chip removal and poor processing quality in traditional drilling process. Motion characteristics and chip breaking mechanism were studied， and the comparative tests of conventional drilling and axial ultrasonic vibration assisted drilling were performed on the 45# steel using an own-designed axial ultrasonic vibration assisted drilling system. Investigations were done toward the machining precision of holes， surface morphology and the shape of chips. The experimental results demonstrate that axial ultrasonic vibration assisted drilling can effectively reduce the surface roughness and improve the microscopic morphology compared with the traditional processing. In addition， variance analysis is used for data processing， indicating that the spindle speed and ultrasonic amplitude have significant influences on the surface roughness， and the processing effect is best when the amplitude is 20μm and spindle speed is 450r/min. References | Related Articles | Metrics

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Optimization of Longevity Technology for Bosh Copper Cooling Stave with Shaped Tubes Based on Response Surface Method MA Xiao-gang， CHEN Liang-yu， LI Yang 2019, 40 (5):  710-715.  DOI: 10.12068/j.issn.1005-3026.2019.05.020 Abstract ( 540 )   HTML   PDF (1188KB) ( 674 )   Based on the principle of heat transfer， a parametric model of thermal structure of blast furnace(BF)bosh with shaped tube copper cooling stave(ellipse， rectangle， double circle， three circle and hexagon)for heat transfer is presented. From the heat transfer analysis of copper cooling stave， the optimal choice of cooling water tubes is achieved. Stimulating the normal working condition of BF， the coupled thermal and structural analysis of the model at the initial stage of furnace opening， with the hot and cast-in-brick surface of cooling stave not covered by slag， is conducted to obtain the mutual influencing rules between parameters and its mechanical properties. The response surface method combined with genetic algorithm(NSGA-Ⅱ)is applied to optimize the structural parameters and longevity technology of bosh. The optimized bosh structure has been significantly improved in heat transfer characteristics and mechanical properties. The model and the parametric calculation program can be applied to assess and optimize the design of longevity technology of bosh. References | Related Articles | Metrics

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Robust H○∞ Control of Active Suspension Based on Differential Geometry LI Wu-jie， CHEN Cong-gen， GUO Li-xin 2019, 40 (5):  716-721.  DOI: 10.12068/j.issn.1005-3026.2019.05.021 Abstract ( 689 )   HTML   PDF (559KB) ( 712 )   By means of the differential geometry method and the robust H○∞ control theory， a robust H○∞ control strategy for active seat suspension and vehicle active suspension based on differential geometry method is proposed. On the basis of establishing the three-degree-of-freedom model of the "car-chair" vehicle， considering the nonlinear characteristics of the elastic force and damping force of seat suspension and vehicle suspension， the differential geometry method and the nonlinear state feedback transformation method are applied to precisely linearize the active suspension nonlinear system. Then， the vertical accelerations of the chassis and the seat are taken as the control targets， and the robust suspension H○∞ controller of seat suspension and vehicle suspension is designed with the wheel dynamic displacement and the vehicle suspension deflection range less than the specified value as the constraint conditions. The simulation experiment with Matlab/Simulink is carried out to verify the effectiveness and feasibility of the integrated variable gain LQR control method. References | Related Articles | Metrics

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Study on the Circular Profile of Scroll Compressors with Changing Radii DING Jia-nan， ZHANG Ying-li， YUE Xiang-ji， BA De-chun 2019, 40 (5):  722-727.  DOI: 10.12068/j.issn.1005-3026.2019.05.022 Abstract ( 716 )   HTML   PDF (984KB) ( 1130 )   The scroll profile of variable base circles with internal and external starting angles was studied. Based on whether the opening angle started on x axis， the external and internal profile equations of two types of variable base circles were given. The expression of eccentric distance was deduced and the relation between two types of base circles with changing radius profile equations was analyzed. The scroll profile of variable base circles was modified in double arc and the modified profile equations of double arc were given. The relation between two types of modified profile equations was analyzed and the influences of the modified opening angles on the modified tooth profile and compression ratio were explored， which may provide a reference for further studies on variable base circle scroll profiles. References | Related Articles | Metrics

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Study on Process Parameters in Transverse Bending of Tailor Rolled Blanks ZHANG Hua-wei， WANG Xin-gang， CHEN Xiao-hui， HOU Dong-xiao 2019, 40 (5):  728-733.  DOI: 10.12068/j.issn.1005-3026.2019.05.023 Abstract ( 640 )   HTML   PDF (1113KB) ( 728 )   The forming properties and characteristics of tailor rolled blanks(TRB)in transverse bending process were studied by taking U-channel as the research object. The mechanisms of forming defects， including bending springback and thickness transition zone(TTZ)movement etc.， were discussed. On this basis， the special emphasis was put on the effects of process parameters on springback and TTZ movement. Results indicated that the springback of TRB decreases with the increase of blank holder force(BHF)， and this trend is especially prominent for unannealed TRB. Springback decreases first and then increases with the increase of friction coefficient， and increases with the increase of die clearance. TTZ movement decreases first and then increases with the increase of BHF， decreases with the increase of friction coefficient， and it is almost not affected by die clearance. Overall， BHF of (1~4)t， friction coefficient of around 0.12 and die clearance of 2.2~2.4mm are advantageous in controlling springback and TTZ movement. References | Related Articles | Metrics

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Control Strategy and Trajectory Planning of Serial Multi-arm Inspection Robots FANG Li-jin， HE Chang-lin， ZHU Shuai， TAO Guang-hong 2019, 40 (5):  734-739.  DOI: 10.12068/j.issn.1005-3026.2019.05.024 Abstract ( 636 )   HTML   PDF (787KB) ( 708 )   With a three-arm inspection robot taken as an example， a hierarchical planning control strategy was analyzed and divided into a line information library layer， an action planning layer and an execution planning layer. The line information library layer is based on the known information of the high-voltage transmission line to be detected， including information on the type， location， and quantity of obstacles. The overall action planning layer and the execution planning layer are summarized according to the finite-state machine theory that when the input event is a (the second layer of the action planning layer)， under the action of f (the third layer of the execution layer)， the state q (the robot’s initial state) is mapped to the state p (the robot’s termination state). In the end， the trajectory planning of this robot was simulated by Matlab and the experiment of the prototype laboratory spanning the anti-vibration hammer and overhanging metal fittings， whose results verified the effectiveness and feasibility of the control strategy and the trajectory planning method. References | Related Articles | Metrics

Resources & Civil Engineering

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Application of Double Base Point Iterative Weighting Method in Bridge Engineering LIANG Li， XING Guan-hua， WU Feng-yuan 2019, 40 (5):  740-744.  DOI: 10.12068/j.issn.1005-3026.2019.05.025 Abstract ( 625 )   HTML   PDF (378KB) ( 599 )   Accuracy of the indicator weight is one of the keys to the assessment problem and the subjective and objective weighting methods have their own drawbacks. Thus， a group decision-making weighting method based on double base point analysis is proposed. The subjective weights of experts are collected by AHP. Taking the subjective weighted average as the initial positive and negative basis， the weight sequence is normalized relative to the positive base. The minimum Euclidean distance is constructed to solve the expert credibility and correct the subjective weights. The revised weight is repeated as a positive basis point until the result converges to the optimal weight. A case study verifies that the iteration of weight weakens the influence of over-ambiguous weight on the final weighting result. The process of merging credibility and subjective weight takes into account the respective advantages of the subjective and objective weighting methods， and it improves the scientificity of the empowerment results. References | Related Articles | Metrics

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Extension Process and Fracture Mechanism of Hydraulic Fractures in Low Permeability Reservoir ZHANG Peng-hai， ZHANG Zi-lin， LI Ming， ZHANG Liao-yuan 2019, 40 (5):  745-749.  DOI: 10.12068/j.issn.1005-3026.2019.05.026 Abstract ( 666 )   HTML   PDF (1166KB) ( 803 )   In order to evaluate the hydraulic fracturing effect in the low permeability reservoir of Huagu 6 well， a microseismic monitoring system was established on the surface of the well. Based on microseismic data， the spatio-temporal extension process and fracture mechanism of hydraulic fractures are analyzed by means of crack extension path and moment tensor inversion. The results show that the spatial distribution characteristics of fractures changed with the liquid viscosity. The injection of high viscosity liquid formed a fracture network with low fracture density. The injection of low viscosity liquid formed a large-ranged dense fracture network with short extension path， and many crack branches. The injection of medium viscosity liquid formed some fractures that initiated from the branching fracture ends. The fracture type was mainly shear fracture(89.5%)， and was not affected by the viscosity of the liquid. References | Related Articles | Metrics

Management Science

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Evaluation Model of Bus Route Service Quality Based on Passengers Perceptions LIU Ying， YU Miao， LIU Yang 2019, 40 (5):  750-755.  DOI: 10.12068/j.issn.1005-3026.2019.05.027 Abstract ( 673 )   HTML   PDF (429KB) ( 749 )   Aiming to solve the limitation of the evaluation method of traditional bus route service quality， a universal weight analysis method based on passengers perceptions is proposed. Firstly， a weight determination method is established based on passengers perceptions in order to determine the weight of experts and the comprehensive weight of each group. Secondly， the quality evaluation AHP-BP network model of urban bus route service can be acquired by training， testing and verifying with the above data as prior samples. Finally， an empirical study is launched on a certain bus route in Shenyang， and the results demonstrate that the model reflect passenger perceptions adequately as well as reduce the randomness of subjective evaluation which can provide an improved direction for a bus route service. References | Related Articles | Metrics

Mathematics

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An Improved Uzawa-PSS Method for to Solve Point Problems SHEN Hai-long， LI Hong-li， SHAO Xin-hui 2019, 40 (5):  756-760.  DOI: 10.12068/j.issn.1005-3026.2019.05.028 Abstract ( 559 )   HTML   PDF (465KB) ( 771 )   Aiming at the non-Hermitian saddle point problem， an improved Uzawa-PSS iteration method is constructed based on the existing Uzawa-PSS method. The main idea of the new method is to solve two linear subsystems in each iteration step of Uzawa-PSS method， whose coefficient matrices are αI+P and αI+S， respectively. The first subsystem can be solved by CG method， but the second subsystem is very difficult to solve. The improved algorithm uses the single-step PSS iteration method to approximate the problem. Then the new method is used to solve the non-singular and singular saddle point problems respectively， and the corresponding convergence analysis is given. The numerical simulation also proves that the improved Uzawa-PSS iteration method has obvious advantages in iteration steps， CPU time and relative residuals. References | Related Articles | Metrics