Table of Content

25 August 2020, Volume 48 Issue 8

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Electronics, Communication & Automation Technology

A Detection Method with Deep Neural Networks for Video Motion Vector Steganography



HUANG Xiongbo HU Yongjian WANG Yufei

2020, 48(8):  1-9.  doi:10.12141/j.issn.1000-565X.190917

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The existing deep neural network steganography detection technology was mainly proposed for digital image steganography． Since there are great differences between image steganography and video steganography，the deep neural networks designed for image steganalysis cannot be simply extended to video steganalysis． Therefore，a motion vector-modification video steganography was taken as the target example and a deep neural network for video steganalysis was proposed based on state-of-the-art image steganalysis network SＲNet． A data input matrix which can well reflect the steganographic modification of motion vectors was also introduced． Experimental results demon-strate that the proposed method outperforms two traditional video steganalysis algorithms in detection accuracy for low and middle-bitrate videos，and behaves well for videos at different bitrates．


Recognition of Passengers＇Abnormal Behavior on Escalator Based on Video Monitoring



DU Qiliang, HUANG Liguang, TIAN Lianfang, et al

2020, 48(8):  10-21.  doi:10.12141/j.issn.1000-565X.200010

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Aiming at the problem that dangerous behavior of passengers on the escalator is difficult to be accurately detected in real time，an algorithm for identifying abnormal behavior of escalator passengers based on video surveil-lance was proposed． Firstly，YOLOv3 was used to detect the position of the passenger in the image． Secondly，MobileNetv2 was used as the base network，which was combined with the deconvolution layer to extract the human skeleton of the detected passenger． Thirdly，the Hungarian assignment algorithm based on skeleton distance was used to realize the allocation of passenger ID numbers in the video． Finally，with keypoints as the input，the graph convolutional neural network was used to recognize the abnormal behavior of passenger． The experimental results on the GTX1080GPU show that the proposed recognition algorithm can achieve a processing speed of 15 f/s and an abnormal behavior recognition accuracy rate of 94. 3%，which can accurately recognize the abnormal behavior of passengers on the escalator in real time．


Laser Speckle－Based Real－Time Stereo Matching Algorithm and Its Application



PAN Chuang LIU Yiqi HUANG Daoping

2020, 48(8):  22-28.  doi:10.12141/j.issn.1000-565X.190656

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Stereo matching is the key and challenging problem of binocular stereo vision and it restricts the applica-tion of binocular stereo vision． Noises，obstacles and textureless region reduce the matching accuracy． In this pa-per，a laser speckle based stereo matching algorithm was proposed to solve these problems． Based on the gradient orientation of each pixel，a new matching cost function was proposed． Then semi-global matching and guided filter were cascaded to aggregate matching cost． This method can meet the real-time requirements and improve the adap-tive capacity of algorithm for slant plane． Finally，a confidence detection method was proposed to refine the disparity in obstacle regions and the edges regions based on the mean value and minimum value of the aggregated matching cost． Its application in logistics industry shows that the proposed algorithm can be used to measure the size of pac-kage and the accuracy can reach to ±5%．


Block Classification－Based Adaptive Threshold AdjustmentGroup Sparse Ｒeconstruction for CVS



YANG Chunling ZHENG Zhaobiao LI Jinhao

2020, 48(8):  29-37,48.  doi:10.12141/j.issn.1000-565X.190347

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Aiming at the problems that structural similarity based inter-frame group sparse representation (SSIM-In-terF-GSR) algorithm can＇t fully utilize the high-quality reconstructed key frame information when reconstructing the smooth region and the sparse processing threshold setting is unreasonable，block classification-based adaptive threshold adjustment group sparse reconstruction (BC-ATA-GSR) algorithm was proposed in this paper． Firstly，image blocks were classified into smooth blocks and motion blocks according to the motion state of the objects in the blocks，and reasonable reference frames were allocated for different types of blocks to improve the reconstruction quality of the smooth regions in the video sequence． Then，in order to retain the sufficient structural information，the initial threshold of sparseness was set adaptively according to the sampling rate and the image block type． Fina-lly，an iterative threshold gradient reduction scheme was proposed to accelerate the iterative convergence rate and improve the quality of reconstruction． Compared with SSIM-InterF-GSＲ algorithm，BC-ATA-GSR algorithm achieves better reconstruction effect，and the average PSNR of the reconstructed QCIF and CIF video sequence are increased up to 3. 77dB and 2. 28dB respectively，and the time complexity is reduced up to 42. 08%．


Attribute－Aware Task Allocation and Privacy－Preserving Coordination Mechanism for MCS



YANG Peng WU Qiming

2020, 48(8):  38-48.  doi:10.12141/j.issn.1000-565X.190722

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Aiming at the problems of sensing task allocation and the protection of private information of the sensing user in mobile crowd sensing network，a collaborative mechanism of task allocation and privacy protection based on user attribute awareness was proposed． Firstly，according to the inherent attributes of the sensing user and the his-torical task participation record，the user＇s different tendencies，wishes and access to the task were mined and taken as the indexes to quantify the user＇s static attributes and social attributes． Then，the user attributes were considered as input，and the BP neural network was used to analyze user service capability，so as to realize the optimal alloca-tion of tasks and users． Finally，the sensing user generated pseudonyms to participate in the sensing task，and the random number generated by user attributes was encrypted based on the ring signature． Under the premise of ensu-ring the privacy of the perceived users，the accuracy of the platform＇s perceived data was improved． The simulation experiment results show that the proposed strategy can effectively select the sensing users，validate the availability of the user＇s uploaded data，and protect the user＇s identity security．


Saliency Detection Based on Multi－Level Deep Features and Random Walk



CUI Dong, WANG Ming, LI Gang, et al

2020, 48(8):  49-55.  doi:10.12141/j.issn.1000-565X.190515

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In order to solve the problems of incomplete feature learning and unobvious salient regions in complex scenes for the traditional saliency detection methods，a saliency detection algorithm based on multi-level deep fea-tures and random walk was proposed． Firstly，the fully convolutional networks (FCN) was used to perform multi-level convolution deep feature extraction on the image by combining the deep and shallow feature information． Se-condly，superpixels segmentation on the image was carried out and the extracted deep convolution features were assigned to the corresponding superpixels to construct a feature matrix． Finally，the final saliency map was generated by regularizing the random walk ranking model． The experimental results on the ECSSD and DUT-OMRON databases show that the proposed method has certain advantages in accuracy and F value，compared with the six representa-tive saliency detection algorithms．


Chemistry & Chemical Engineering

Determination of 20 Migratable Organotins in Toys Based on GC－MS/MS Method



MA Tongmei, REN Peng, HUANG Lina, et al

2020, 48(8):  56-64.  doi:10.12141/j.issn.1000-565X.200188

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In order to solve the problem that the quantification limit of organotin in the second type of toy materials is difficult to reach，and to increase the types of migrating organotin compounds (OTCs) detected in toys，a gas chromatography-tandem mass spectrometry (GC-MS/MS) detection method capable of simultaneously determining 20 migrating OTCs in toys was established，by taking the second type of toy materials as the research object and optimizing the experimental conditions． After migration from simulated gastric juice (HCl) followed by derivatization using the derivatizing agent (sodium tetraethylborate)，the OTCs were analyzed by multiple reaciton monitoring mode (MRM)，during which，migration conditions，derivatization steps as well as operating parameters of GC-MS/MS were optimized． The experimental result shows that the 20 kinds of OTCs display good linear relationship in the concentration range from 0. 005 to 0. 200 mg/L with the linear correlation coefficients of 0. 9963 ～ 0. 9999． The spiked recoveries of OTCs in samples are in the range of 80. 6% ～117. 2% with relative standard deviations less than 5% (n = 6) and their detection limits are as low as 0. 019 ～ 3. 196 μg/kg with the limit of quantifications between 0. 065 and 10. 652μg/kg． Compared with GC-MS，the most commonly employed method for OTCs detection in toys，the newly established method can separate 20 different kinds of OTCs within 20min at one time，indicating the advantages of strong selectivity，accurate quantification，high sensitivity with a very low detection limit and quantitation limit，dissolving the problem that the quantitation limit of OTCs for the second type of toy materials was difficult to be achieved． Furthermore，this method also extends the detection limitation of OTCs types in toys to 20 types from the original 11 types given in the EU standard． The developed method was proved to be comprehensive，efficient，reliable and sensitive for fast determination of OTCs in toys．


An Evacuation Path Model of Chemical Industrial Park Based on Road Network Risk



CHEN Guohua, LIANG Xu, ZHOU Lixing, et al

2020, 48(8):  65-71.  doi:10.12141/j.issn.1000-565X.190734

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Based on the analysis of the severity of chemical accident，an evacuation path model based on the road networks risk was proposed． Firstly，based on accident statistics and accident probability of chemical industrial park accidents，a targeted accident model was established and accident consequences and regional individual risks were quantitatively calculated． Secondly，the evacuation path model of chemical industrial park was constructed based on the road network risk which was calculated according to three factors that influence the choice of evacua-tion personnel road network，that is，the distance from the evacuation exit，the risk of the evacuation position，and the evacuation space of the evacuation position． Finally，the Dijkstra algorithm was used to calculate the path of the evacuation scene in the accident scene to avoid the accident and shorter evacuation time． The simulation results show that the proposed path selection model can plan a safe evacuation path that effectively avoids the scope of acci-dents and provides a reference for evacuation personnel transfer and park evacuation design．


Inhibition Effect and Mechanism of Three Kinds of Flame Ｒetardant Powders on the Explosion Intensity of Zirconium Dust Clouds



WANG Qiuhong MIN Rui WANG Qingfeng

2020, 48(8):  72-81,90.  doi:10.12141/j.issn.1000-565X.190344

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In order to analyze the effect and mechanism of three flame retardant powders，namely，Ammonium dihydrogen phosphate (ABC)，Melamine Pyrophosphate (MPP)，and Melamine Cyanurate (MCA)，on suppressing the explosion intensity of zirconium dust clouds，A 20-L near-spherical explosion test system and a thermogravime-tric and differential thermal analyzer were used to carry out experiments． The results show that all three flame retar-dant powders can effectively inhibit the explosion intensity of zirconium dust clouds． ABC powder has a significant advantage in inhibiting the explosion of zirconium dust clouds，and ABC powder of 200g/m 3 can completely inhibit the most violent explosion of zirconium dust clouds． When the mixture of zirconium powder and these three kinds of flame retardant powders are heated in air atmosphere，the process of variation appears to be from weight gain to weight loss then to weight gain，and from exothermic reaction to endothermic recreation then to exothermic reaction．The lower decomposition temperatures of flame retardant powder are，the better inhibiting performance of oxidation of zirconium powder is． When the mass ratio of zirconium powder to flame retardant powder is 2∶ 1，the starting temperature of the rapid oxidation reaction of zirconium powder augment from 257. 08 ℃ to 591. 45，581. 43 and 401. 30℃ with the additions of ABC，MPP，and MCA powder，respectively． ABC powder possesses the best inhi-bition effect on the explosion of zirconium dust clouds among the tested samples because of ABC powder prolonging the time of rapid oxidation reaction of zirconium powder，enhancing the starting temperature of rapid oxidation of zirconium powder，and maximizing the inhibition of the combustion process of the zirconium powder．


Compression－Resilience Property of Wet Paper－Based Friction Materials



LIANG Yun ZHANG Riying ZHANG Chunhui

2020, 48(8):  82-90.  doi:10.12141/j.issn.1000-565X.190106

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The effects of beating degree of cotton fiber，carbon fiber morphology，friction powder content and resin elastic modulus on the compression-resilience property of wet paper-based friction materials were investigated by adjusting the raw material characteristics and formula． And 4 paper-based friction materials with different compres-sion-resilience property were prepared to explore the influence of compression-resilience property on the friction and wear performance． The results show that the material has good dimensional stability when the beating degree of cot-ton fiber is above 20^o SR; the short carbon fiber of 3 mm and ethanol solvent type resin with high elastic modulus can improve the dimensional stability of the samples; the stable compression ratio can be improved by adding the friction powder; the compression-resilience property has significant influence on friction and wear performance． The friction and wear performance of the material is rather better when the permanent deformation rate of the wet paper-based friction material is below 4. 0% and the stable compression ratio is above 7. 0%．


Mechanical Engineering

Analysis of Stress Distribution and Wear in Surface Contact



HOANG Van Cuong, LI Wei, MAO Feiyu, et al

2020, 48(8):  91-101.  doi:10.12141/j.issn.1000-565X.190623

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The contact stress distribution significantly influences the working surface damage． In order to analyze the wear surface damage，the finite element method was used to analyze the evolution process of surface contact stress of three-dimensional slider friction model from static state to sliding state，and comparative study on the plane stress photoelasticity experiments were carried out． By simulation analysis，the distribution of principal stress diffe-rence，contact pressure and frictional stress were obtained． Simulation results show that along with the contact state changes，the contact stresses firstly concentrate on the edges of slider and then concentrate on the front edge of the motion; the influences of load and friction coefficient on contact stresses are significant． The photoelasticity experi-mental results of plane stress field show that the contact stresses is concentrated in front of the movement，which is consistent with the simulation results． The results of abrasion experiment show that when the wear begins，the front edge of the slider shows the biggest damage and the maximum contact stress; as the wear distance increases，the damage of contact surface expands from the front to the back，and finally covers the whole contact surface; the lar-ger load on the contact surface，the higher wear degree．


Mixed－Lubrication Analysis of Journal Bearing Considering Local Wear and Cavitation Effect



SONG Xintao SUN Shiqing WU Wei

2020, 48(8):  102-107,114.  doi:10.12141/j.issn.1000-565X.190863

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A mixed hydrodynamic lubrication model of bearing with local wear was established based on the ave-raged Ｒeynolds equation and JFO cavitation boundary condition，in order to analyze the effects of local wear and cavitation effect on the mixed lubrication performance of journal bearing． The effect of different maximum wear depths on oil film thickness distribution，average hydrodynamic pressure distribution，position of axial center and Stribeck curves of the bearing were investigated by numerical solution． The results show that local wear significantly changes oil film thickness distribution and average hydrodynamic pressure distribution． The large wear depths lead to the change of the position of axial center，which deviates from the original design． The small wear depths reduce the friction coefficient of the bearing in mixed-lubrication regime，and can transfer from mixed-lubrication to hydro-dynamic lubrication at a lower speed． The friction coefficient increases with the increase of the wear depth．


Fatigue Test and Fatigue Reliability Evaluation of Loader Working Device



WAN Yipin SONG Xuding YUAN Zhengwen

2020, 48(8):  108-114.  doi:10.12141/j.issn.1000-565X.190921

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In order to design an anti-fatigue loader working device and evaluate its fatigue reliability，two dimen-sional load spectrum of the fixed attitude equivalent external load of the ZL50G loader was obtained． Loading spec-trum of accelerated fatigue test and the fatigue reliability evaluation of very small samples were carried out． The results show that 35. 88h of acceleration loading spectrum can be equivalent to 495. 67h of continuous operation of loader，and the purpose of fast fatigue test of working device is realized． The average actual fatigue life of the wor-king device is 9132. 20h． The main cause of fatigue fracture is the weld toe crack near the boom plate． Based on the fatigue reliability evaluation of very small samples with given working life and fatigue life test results，the cubic polynomial of the mathematical relationship between the life and reliability of the working device was obtained．


Heat Dissipation Performance of Silicone－Oil Fan Clutch



WANG Hongmin, CHEN Yalou, WANG Xihui, et al

2020, 48(8):  115-123,129.  doi:10.12141/j.issn.1000-565X.190699

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A silicone-oil fan clutch was taken as the studying object，and the finite element and the analytical model for estimating heat dissipation of silicone-oil fan clutch was developed，considering of the heat generation changes with shear radius． The temperature of the monitoring points on the housing surface of the clutch at different rotational speeds was measured，and the measured results was compared with the simulated results． The results show that the finite element model of the heat dissipation calculation of the silicone-oil clutch is correct． Then the structure of silicone-oil fan clutch was optimized． Finite element analysis of the optimized clutch was carried out and the result indicates that the optimized structure of the clutch has better heat dissipation performance．


Finite Element Simulation Analysis and Evaluation of Ｒadial Tire＇s Transient Dynamic Characteristics



ZANG Mengyan, WANG Lichen, ZHOU Tao, et al

2020, 48(8):  124-129.  doi:10.12141/j.issn.1000-565X.180517

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The finite element analysis method has the advantage of high simulation accuracy and it can obtain the change of contact stress and internal stress during the rolling process． So the dynamic characteristics of the tire was studied by using implicit and explicit finite element analysis method in this paper． The radial tire 215/60Ｒ16 was taken as the research object and the finite element simulation model was built． The axle forces at vertical，longitu-dinal and lateral direction were obtained through cleat impact test carried out on the drum test machine under two working conditions，that is when speed is 10 km/h，impact angle is 90° and speed is 60 km/h，impact angle is 45°． The good agreement between simulation result and experiment result shows that the finite element analysis method is valid to predict the dynamic characteristic of tire．


Optimization of Fused Deposition Modeling Process Parameters Based on Different Part Dimensions and Assessment Indexes



CHEN Songmao CHEN Yulin

2020, 48(8):  130-138.  doi:10.12141/j.issn.1000-565X.190884

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Different dimensions of fused deposition parts cause the differences in dimensional accuracy，which will mislead the optimizing process of parameters by employing different quality assessment indexes． Therefore，three types of samples with different dimensions were tested by the Taguchi orthogonal experiment method，which took layer thickness，filling velocity，nozzle temperature and filling rate as the factors and took dimensional error，dimensional deviation and build time as quality assessment indexes to investigate the influence of different part dimen-sions and assessment indexes on the optimization of fused deposition modeling process parameters． The results show that three types of samples exhibit differences in size accuracy during deposition; curves of both equivalent and each dimensional deviation values of different groups generally present an increasing trend of waves，and the fluctuation range of equivalent dimensional deviation values declines with the increase of the size of samples． Two accuracy assessment indexes are different． The dimensional deviation index are more scientifically reasonable in general，and sequences of factors for evaluating printing efficiency of these samples were the same． Finally，the results of factors＇optimized levels were compared，and the optimization scheme of the combination of process parameters of three samples under different quality requirements was proposed．


Application of Interpolation Loop Surface Subdivision Algorithm in Free Surface Reconstruction of Surfacing



HONG Bo, LI Peng, WU Hongbao, et al

2020, 48(8):  139-144.  doi:10.12141/j.issn.1000-565X.190858

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In order to solve the problems of low weld seam recognition accuracy and difficult automatic welding caused by the irregular shape of the weld seam of the surfacing free-form surface，a surface reconstruction method using the interpolation Loop surface subdivision algorithm for the three-dimensional morphological data of the surfa-cing welds collected by the rotating arc sensor was proposed． Firstly，high-quality topography data was obtained by using the Grubbs test algorithm to filter the abnormal sampling points． Then，initial triangle meshing on topography data was carried out by using local optimal Delaunay algorithm． Finally，interpolation Loop tessellation algorithm was used to tessellate the initial triangle mesh in order to rebuild the three-dimensional appearance of weld．Research result indicates that this method has good surface reconstruction effect and can reduce the error of the initial triangle meshing．Thus it has high usability．