bob手机在线登陆学报自然版

2019, 39(3): .

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2019, 39(3): .

Abstract(753) PDF(290)

Abstract:

Automatic Mobility Identification Method for Spherical Six-Bar Linkages

WANG Jun, NIE Liang-yi, DING Hua-feng, GONG Ya-jing, HE Hong-xiu

2019, 39(3): 221-227. doi:10.15918/j.tbit1001-0645.2019.03.001

Abstract(1041) PDF(518)

Abstract:
Branch (assembly mode or circuit) identification is a way to assure motion continuity among discrete linkage positions,which is the most fundamental issue among the mobility problems that may also include sub-branch (singularity-free) identification,range of motion,and order of motion.Branch analysis becomes more complex in spherical or spatial linkages.In this paper,an automated branch identification method was proposed based on discriminants of kinematic equations and the concept of joint rotation space (JRS) to analyze the branch formation of a spherical six-bar linkage.And an automated identification algorithm was presented to rectify the motion of a spherical six-bar linkage.The proposed method is general and conceptually straightforward.It can be applied for all linkage inversions.Examples were employed to illustrate the application of the proposed method.

Piston Stress and Deformation Comparison in FPE and CE Operating Mode

LI Yan-xiao, ZUO Zheng-xing, FENG Hui-hua, KUANG Nian-ling, YANG Jun

2019, 39(3): 228-234. doi:10.15918/j.tbit1001-0645.2019.03.002

Abstract(924) PDF(557)

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To study the stress and deformation characteristic of piston for free piston engine,a finite element method was used to analyze the differences of the piston stress and deformation between free piston engine (FPE) and crank engine (CE).Results show that:the stress level of FPE's piston is lower than that of CE and the difference is mainly caused by mechanical load.As a result is of lower combustion pressure load and larger inertial load,the max stress of FPE's piston is less,which is nearly 72% of CE's piston.Under the thermo-mechanical coupling load,the difference of piston deformation between FPE and CE is small at the top and large at the skirt.The characteristics of the thermal load and the mechanical load of FPE piston result in smaller skirt deformation compared with CE piston,and the max FPE's piston skirt radial deformation is nearly 56% of CE's piston.

Investigation on the Soot Formation of Cottonseed Oil Diffusion Flame by Two-Dimensional Laser Induced Incandescence

HE Xu, ZHANG Zhi-peng, WU Hao, GAO Yong-li, HUA Yang, LIU Feng-shan, LI Xiang-rong, LIU Fu-shui

2019, 39(3): 235-240,326. doi:10.15918/j.tbit1001-0645.2019.03.003

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A two-dimensional LⅡ (2D-LⅡ) experiment system was established to first measure the soot volume fraction distribution in the Gülder ethylene diffusion flame.Compared with the extinction method and the single-point LⅡ calibration method,the experiment results show its validity.The 2D-LⅡ setup was then used to investigate the effects of cottonseed oil on soot formation of vaporized diesel laminar diffusion flame produced on a liquid burner.The results show that with increasing the blending ratio both the maximum volume fraction and the total amount of soot decrease.In the flame centerline region,the soot volume fraction first increases with increasing the flame height to reach a peak and then decreases towards the flame tip.The peak value of the soot concentration appears in the flame-wing in the lower part of the flame and moves towards the flame centerline with increasing the flame height.

Influence of Deformed Friction Components on the Thermoelastic Instability

MA Biao, LI Ming-yang, LI He-yan, DU Qiu, LI Hui-zhu, YU Liang

2019, 39(3): 241-247. doi:10.15918/j.tbit1001-0645.2019.03.004

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Abstract:
The anti-symmetric thermoelastic instabilitymodel was developed to calculate the critical speed with the sliding condition of the perturbation fixed on friction components.The influence of material parameters such as elastic modulus and Poisson's ratio on thermoelastic stability of the friction system was studied.The model was verified by the finite element solution of Yi Yun-bo and Zhao Jianxin.The results show that the deformed discs have great influence on the process of shifting,however little effect on the creeping condition.Among the three kinds of friction discs,paper-based friction discs have the best thermoelastic stability,while the Cu-based friction discs are the worst.The critical speed increases with the increase of the specific heat,thermal conductivity of steel discs and thermal expansion coefficient of friction discs.On the contrary,the critical speed decreases with the increase of the other material parameters.Under the premise that the parameters of the separator discs remain unchanged,the stability of the friction system can be improved by decreasing the specific heat,Poisson's ratio,Young's modulus and thermal conductivity,meanwhile increasing the coefficient of the thermal expansion.

Displacement Wavelet of Piezoelectric Multilayer Stack Actuator and its Control Technology in Fuel Injector

WANG Jun, XIONG Qing-hui, JIN Yi, ZHANG You-tong

2019, 39(3): 248-254. doi:10.15918/j.tbit1001-0645.2019.03.005

Abstract(850) PDF(373)

Abstract:
Affecting the performance of needle opening-close in fuel injector,the displacement of piezoelectric multilayer stack actuator (PMSA) was analyzed by test measurement to find the position of displacement wavelet,and some factors causing the displacement wavelet of PMSA were analyzed.Firstly,a simulation model was established for the PMSA based on ABAQUS software to analyze the displacement change of PMSA in different time.Results show that the piezoelectric component inertia is the main reason causing displacement wavelet of PMSA in the expansion and contractive stage.Then a hydraulic vibration absorption method and a voltage optimization method were presented to decrease the displacement wavelet of PMSA.Experimental results show that hydraulic coupling displacement amplifier can reduce the displacement wavelet to a certain extent,and trapezium current control can effetely reduce displacement wavelet of PMSA.

Face Recognition via Deep Learning and Constraint Sparse Representation

ZHANG Ji-wei, NIU Shao-zhang, CAO Zhi-yi, WANG Xin-yi

2019, 39(3): 255-261. doi:10.15918/j.tbit1001-0645.2019.03.006

Abstract(1199) PDF(553)

Abstract:
The matching between single image and single image has attracted much attention in the current face feature matching algorithms,in order to make use of the correlation information between image sequences effectively,a face feature matching algorithm based on deep learning and constraint sparse representation was proposed.The feature extraction of face images was carried out through CNN network,and an improved sparse expression method was used to automatically select similar image sequences for feature matching,so that the correlation information between image sequences could be effectively utilized.Experimental results show that the proposed algorithm can achieve better result in LFW and AR databases,and is superior to other face feature matching methods,such as SRC,L1-norm and CRC-RLS.

Splicing Trajectory Pairs Search Based on Location

CHEN Zi-jun, ZHANG Jing, LIU Wen-yuan, LIU Yong-shan

2019, 39(3): 262-268. doi:10.15918/j.tbit1001-0645.2019.03.007

Abstract(927) PDF(359)

Abstract:
With the proliferation of mobile devices,a large number of trajectories are generated.Location-based trajectory search is to find the top-ktrajectories from a database,given a small set of locations.However,the returned trajectory may not go through all locations as close as possible.Location-based splicing trajectories pair search was proposed based on the idea that trajectory could be spliced to help users to get closer trajectory to all the query points.In the termination of search process,an effective termination condition of the search process was given for splicing trajectory pairs.At last,the effectiveness and efficiency of the proposed algorithm were verified based on the real data set.

A New Model for Scene Text Recognition

WANG Mao-sen, JIANG Xiao-sen, NIU Shao-zhang

2019, 39(3): 269-275. doi:10.15918/j.tbit1001-0645.2019.03.008

Abstract(1085) PDF(547)

Abstract:
A LRAM model was proposed based on LSTM with ResNet (residual network) and attention model for reading text in natural image.In this model,a ResNet was adopted to accelerate the convergence speed of the network and to reduce the difficulty of network training,and an attention mechanism (AM) was utilized to carry out weigh distribution of different sequences for current text recognition and to improve the accuracy of text recognition.Extensive experiments on various benchmarks,including the Synth90K,Street View Text and ICDAR datasets,show that the performance of LRAM model substantially outperforms the existing methods.

Multi-Robot Cooperative Assembly Line Balancing Method Based on Energy Efficiency

ZHOU Bing-hai, KANG Xue-yun

2019, 39(3): 276-282. doi:10.15918/j.tbit1001-0645.2019.03.009

Abstract(891) PDF(307)

Abstract:
To achieve cooperative assembly for multi-robot in some station of an assembly line,taking the cycle time of an assembly line,the total energy consumption and the total cost of robots as the minimum optimizing objectives,a mathematical model with three objectives function was developed.To solve this problem,a multi-objective hybrid imperialist competitive algorithm (MOHICA) was proposed based on a three-level coding rule,i.e.the station level,the task level,and the robot level.In addition,a non-dominated sorted rule of genetic algorithm and a late-acceptance hill-climbing algorithm were combined into the algorithm to increase the exploration ability of the algorithm.Finally,simulation experiments and theory analysis were carried out to evaluate the proposed algorithm.The results indicate that the proposed algorithm is valid and feasible.

Transferable E-Cash System with Arbitrarily Spending Order

ZHANG Jiang-xiao, FENG Chun-hui, MA Jin-xin, ZHANG Bin, XU Chang, LI Zhou-jun, DANG Ying

2019, 39(3): 283-289. doi:10.15918/j.tbit1001-0645.2019.03.010

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There exist some problems such that the user spending order is fixed in the transferable E-cash system,and the transferable number is restricted.Using the Groth-Sahai proof system,Ghadafi group blind signature and commitment to commitment,a transferable E-cash system of equal length with optimal anonymity and arbitrarily spending order was designed in a standard model.It was arranged that,based on the commitment to commitment,the users could compress the transferable serial number,and the length of the E-cash could be constant in the spending protocol,based on the Ghadafi group blind signature,the arbitrarily spending order could be achieved.Finally,the security of the transferable E-cash system was verified in the standard model.Results show its unforgeability,anonymity,identification of double spender and exculpability.

An Android Malware Detection Method Based on Chi-Squared Test

LIU Ya-shu, WANG Zhi-hai, LI Jing-wei, ZHAO Xuan, WEN Wei-ping

2019, 39(3): 290-294. doi:10.15918/j.tbit1001-0645.2019.03.011

Abstract(922) PDF(319)

Abstract:
The explosive growth of mobile terminals has produced endless malicious applications,bring on great harm to the security of users'privacy and property.To solve this problem,a method based on chi-squared test and Gini impurity increment was proposed for more valuable features extraction and the Naïve Bayes algorithm improvement,so as to improve the estimation accuracy of Android malevolence applications.Test shows that the new features processing method can improve the classification performance of algorithms.At the same time,the improved Naïve Bayes algorithm can achieve higher accuracy than before.

Secure Data Storage Scheme in Hybrid Cloud

LIU Xue-jiao, YE Wei, JIANG Jing-wei, ZHANG Lei

2019, 39(3): 295-303. doi:10.15918/j.tbit1001-0645.2019.03.012

Abstract(988) PDF(328)

Abstract:
Aiming at the problem of data security storage and sharing in hybrid cloud,an efficient data security sharing scheme was proposed for hybrid cloud mode.In the scheme,an attribute-based encryption mechanism with ciphertext policy was used to encrypt data,the ciphertexts were stored on the public cloud through the private cloud;when mobile users wanted to access cloud data,anonymous key negotiation technology and the delegation mechanism of encryption and decryption were used to ensure fast access to data.The scheme was designed to ensure the secure storage of data on the public cloud,supporting fine-grained access control,and to arrange the private cloud to do most of the computing in the process of encryption and decryption,reducing the processing time for mobile cloud users to access cloud data.In this way,the time for encryption and decryption could be constant regardless of the increasing attributes in the access policy.

Enhanced LEACH Protocol Based Wireless Sensor Network Malicious Node Detection Model

YANG Hong-yu, CHENG Fang

2019, 39(3): 304-310. doi:10.15918/j.tbit1001-0645.2019.03.013

Abstract(812) PDF(390)

Abstract:
To solve the efficiency problem of the existing malicious node detection methods in wireless sensor networks (WSN),a malicious node detection model was proposed based on enhanced low energy adaptive clustering hierarchy (LEACH) routing protocol with reputation (MNDELR).Firstly,in wireless sensor network,the enhanced LEACH routing protocol was used to select the cluster-head nodes and make other nodes to be corresponding cluster-head nodes to form the clusters and determine the packets delivery paths in the network.Then,some information,including the node numbers and the reputation evaluation,were added to the data packets of nodes,and the data packets were sent to the sink node according to the delivery paths.The node numbers in the packets were parsed and compared with the source node numbers in the convergent node to form a list of suspicious nodes.Finally,the reputation values of the nodes were calculated and compared with the threshold to determine the malicious nodes in the network.The experiment results show that,compared with other methods,MNDELR model can detect malicious nodes in WSN more effectively.

Frequency Diverse Array Beam Control Based on Nonlinear Frequency Offset

WANG Bo, XIE Jun-wei, ZHANG Jing, FENG Xiao-yu

2019, 39(3): 311-319. doi:10.15918/j.tbit1001-0645.2019.03.014

Abstract(943) PDF(430)

Abstract:
Unlike the phased-array beam pattern with only angular correlation,the beam pattern of frequency diverse array (FDA) is a function on time,angle and distance.This feature provides a great application value in suppressing distance-related interference and other aspects,but the inherent distance-angle coupling of the beam pattern will bring about new frequency diverse array beam control problems.How to eliminate the distance-angle coupling relationship is the premise to achieve accurate beam control and precise target positioning.To solve this problem,an SD-LCMV (steepest descent linear constrained minimum variance) algorithm was proposed based on variable load constraints to compute the optimal weight vector.At the same time,the logarithm,trigonometric function,exponential function and reciprocal four nonlinear frequency offset increment methods were introduced into ULA-FDA array to verify the decoupling performance of the ULA-FDA array transmit patterns with four different nonlinear frequency offsets.Afterwards,the MUSIC (multiple signal classification) algorithm was used to simulate the MUSIC spectrum function under different frequency offset conditions,and the performance of the target distance-angle two-dimensional joint estimation under the four frequency offset increment methods was compared and analyzed.In addition,simulation was carried out to analyze the receiver structure pattern of the sin-FDA array and the three receive signal processing mechanisms of the sin-FDA transceiver conformal array.Results show the validity of the nonlinear frequency deviation FDA array structure.

Hyperspectral Target Detection Based on Balanced Distance Sub Spectra Selection

WANG Wen-zheng, ZHAO Bao-jun, TANG Lin-bo, FENG Fan

2019, 39(3): 320-326. doi:10.15918/j.tbit1001-0645.2019.03.015

Abstract(1156) PDF(620)

Abstract:
Accurate and fast target detection is one of the key problems in hyperspectral image applications.Band selection is an essential step to improve the utilization efficiency of hyperspectral data.The current hyperspectral band selection methods don't consider task correlation,which affects the effectiveness of band selection results in actual target detection tasks.A new spectra equal interval extraction method was proposed based on constructing the spectra interval difference equalization calculation model.Experiments on hyperspectral remote sensing image dataset have confirmed the superiority of the new method.The results show that the proposed method can achieve better results in terms of computational time and accuracy compared with other band selection methods,and can efficiently achieve target detection of hyperspectral images.

Application of Optimal Homotopy Asymptotic Method for Oldroyd 6 Constant Fluid Model with Slip

Hameed Ullah, SUN Hua-fei, SONG Yang

2019, 39(3): 327-330. doi:10.15918/j.tbit1001-0645.2019.03.016

Abstract(854) PDF(308)

Abstract:
Applying the optimal homotopy asymptotic method (OHAM) to study three nonlinear problems,plane Couette flow,plane Poiseuille flow and plane Couette-Poiseuille flow,of the Oldroyd 6-constant fluid.Firstly,the governing equation and boundary condition of plane Couette flow,plane Poiseuille flow and plane Couette-Poiseuille flow in the Oldroyd 6-constant fluid were introduced respectively.Then applying the optimal homotopy asymptotic method was used to solve the problem,and carrying out some simulations.Finally,the effect of the slip parameter on the velocity profile was discussed based on the simulations.

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