Table of Content

28 August 2019, Volume 53 Issue 8 Previous Issue    Next Issue

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Characteristics of Surface Heat Flux in Shanghai During Summer and Its Influencing Factors LU Yifan，LI Yong，SHIGETOSHI Ipposhi，YASUMITSU Nomura，WANG Ruzhu 2019, 53 (8):  891-897.  doi: 10.16183/j.cnki.jsjtu.2019.08.001 Abstract ( 1194 )   PDF (1144KB) ( 531 )   Save The test accuracy of soil heat flux at 5 mm is verified through thermal diffusion equation-correction (TDEC) method, which can represent the surface heat flux. Meanwhile, considering different factors (solar radiation, soil moisture content and cloud cover, etc.), the diurnal variations of heat flux on three kinds of typical days (clear, cloudy and rainy days) are summarized in Shanghai. The influence of different factors on soil heat flux at 5mm and the principles are comprehensively analyzed through variable control approaches. The results show that soil heat flux at 5 mm obviously fluctuates on clear days, from -23.62W/m2 to 111.81W/m2. The fluctuation range decreases with the decrease of soil depth on cloudy and rainy days. The correlation (R2>0.74) between solar radiation and soil heat flux is strong on days without rain. The fluctuation range of soil heat flux is reduced by the increase of soil moisture content. Soil heat flux of different typical days is mostly affected by different factors. References | Related Articles | Metrics

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Solitary Wave-Induced Response of Sloping Seabed with a Buried Pipeline PAN Jiahe,LIAO Chencong,CHEN Jinjian 2019, 53 (8):  898-906.  doi: 10.16183/j.cnki.jsjtu.2019.08.002 Abstract ( 1078 )   PDF (1402KB) ( 390 )   Save Through the solitary wave-sloping seabed-submarine pipeline coupling model, the pore water pressure response, stress and displacements of submarine pipelines around the buried pipelines in shallow coastal areas under solitary waves are studied. The Navier-Stokes equations considering k-ε turbulence are used to simulate the break, rise and fall of solitary waves on the gentle slope of the seabed. The surface pressure of the gentle slope is calculated. Based on the Biot consolidation equation, the slope model under the wave pressure is established. Based on the linear elasticity theory, the pipeline model is established by partial differential equation. The pore water pressure response characteristics, stress and deformation of the buried pipe seabed soil are calculated and analyzed. Compared with the test data and analytic solutions in literatures, the accuracy of analytical method and the model is verified. By using the validated numerical model, the pore water pressure response and the vertical effective stress response of soil around the embankment on gentle slope seabed under the action of solitary waves are calculated. The vertical force and displacement deformation of the pipelines are also calculated. The results show that, during the solitary wave run-down phase, the pore pressure around the pipelines buried near the coastline of the slope descends obviously, and the pipelines go up greatly. Compared with the situation of buried horizontal seabed and slope foot, the stress and displacement of the pipelines are the most unfavorable here. Besides, pipeline depth, soil parameters and the break, rise and fall of wave have a significant impact on the calculation results. References | Related Articles | Metrics

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Experimental Research on Force Characteristics of a Spherical Particle in Deep Sea Hydraulic Collecting ZHAO Guocheng,XIAO Longfei,YANG Jianmin,YUE Ziyu 2019, 53 (8):  907-912.  doi: 10.16183/j.cnki.jsjtu.2019.08.003 Abstract ( 1144 )   PDF (2569KB) ( 452 )   Save Hydraulic collecting is a typical way to collect ores in deep sea mining. The study on mechanical characteristics of spherical particles in collecting flow field is the basis of collecting system design. The experiment system of hydraulic collecting is set up in the laboratory to study the impact of the ratio of bottom clearance to diameter of the particle (h/d), the angle between pipe inlet end face and the bottom of particle (θ), the towed speed of the suction pipe (vt) on vertical suction force coefficient (Cvs) and radius suction force coefficient (Crs). The results show that Cvs decreases exponentially with the increase of h/d; the vertical force predicting model of particles is established with the maximum error less than 10%; θ=20° is the point at which the fast fading of Cvs begins; the maximum of Crs and Cvs tend to increase slightly with the increase of vt, and Crs always reaches the maximum at θ=35° or θ=40°. The results of this article can provide reference for the design of hydraulic collecting system and refinement of collecting process. References | Related Articles | Metrics

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Fire Smoke Spread Law in Deep Water Semi-Submersible Platform XU Pengcheng，GAO Jin，QIU Guozhi 2019, 53 (8):  913-920.  doi: 10.16183/j.cnki.jsjtu.2019.08.004 Abstract ( 1085 )   PDF (3835KB) ( 291 )   Save Based on the fire dynamic simulator numerical method, the fire smoke spread law in deep water semi-submersible platform is studied. According to the most disadvantageous principles of fire scenario design, four fire cases are designed to investigate the fire smoke spread and distribution law of upward spreading ability along stairwell. And its influence on the distribution of extremum of temperature, visibility, CO volume fraction on the staircase of each deck are studied. The impact of height of fire deck on the distribution law of filling the deck within required time is analyzed. Its impact on the smoke spreading path is also analyzed.The results show that when the distance between the stairwell and the fire room decreases, the upward spreading ability of smoke along the stairwell will be strengthened. The maximum temperature, the shortest time of visibility reaching critical condition, the maximum CO volume fraction of decks above the fire deck are located in staircases with strong upward spreading ability of smoke. With the height of fire deck increasing, it would take shorter time for the smoke to fill the decks above the fire deck and longer time for that below the fire deck. The results can contribute to the design of fire protection and the evacuation path when the semi-submersible platform is on fire. References | Related Articles | Metrics

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Navigation Image Enhancement Based on Color Weighted Guided Image Filtering-Retinex Algorithm XU Fenglin,MIAO Yubin,ZHANG Ming 2019, 53 (8):  921-927.  doi: 10.16183/j.cnki.jsjtu.2019.08.005 Abstract ( 1569 )   PDF (9299KB) ( 329 )   Save Aiming at solving the difficulties in night-time edge detection of guideline during the autopilot navigation of rubber tyred gantry (RTG), a color weighted guided image filtering-Retinex (CWGIF-Retinex) algorithm is proposed. Firstly, the weight estimation of weighted guided image filtering is improved by using vector gradient method. And the edges of color images processed by Retinex are extracted as weights. Secondly, the illuminance components of guideline image are estimated by using CWGIF algorithm. And then, the reflection components are calculated by using the single-scale Retinex algorithm. Finally, an image with enhanced colors and edges is obtained. The results of experiments indicate that CWGIF-Retinex algorithm compared with traditional algorithms can enhance the colors of low illumination area while achieving the goals of removing halo effect, color fidelity, and enhancing the contrast of guideline edges. References | Related Articles | Metrics

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Multiple Signal Classification Beam-Forming Method Based on Time Domain Analysis LI Bing1,2,3,WANG Yongming1,3,HUANG Haining2,3 2019, 53 (8):  928-935.  doi: 10.16183/j.cnki.jsjtu.2019.08.006 Abstract ( 1218 )   PDF (2978KB) ( 342 )   Save For the instability problem of multiple signal classification (MUSIC) beam-forming estimating subspace in frequency domain, a multiple signal classification beam-forming method based on time-domain analysis (TAMUSIC) was proposed. Firstly, the complex analysis data were obtained from the time domain real data by the Hilbert transformation. Secondly, the covariance matrix was constructed in time domain after the time delay, and the noise subspace was statistically obtained by eigen-decomposition. Finally, the beam was obtained by the orthogonal properties of the noise subspace in direction of arrival. The processed results of numerical simulation and measured data show that under the case of fast moving target, compared to the MUSIC beam-forming method, TAMUSIC beam-forming method can statistically get the noise subspace and the beam in direction of arrival for fast moving target, improve the side-lobe level more than 3dB. It effectively detects the fast moving target, and has no phenomenon of false target and split beam. It also improves the stability of MUSIC beam-forming method in practical project. References | Related Articles | Metrics

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A High-Speed Read Circuit for Phase-Change Random-Access Memory LI Xiaoyun,CHEN Houpeng,LEI Yu,LI Xi,WANG Qian,SONG Zhitang 2019, 53 (8):  936-942.  doi: 10.16183/j.cnki.jsjtu.2019.08.007 Abstract ( 1232 )   PDF (2521KB) ( 350 )   Save The read circuit in phase-change random access memory (PCRAM) is improved to effectively accelerate the memory’s read speed. By reducing the output voltage swing of the sense amplifier in read circuit, output voltages can reach the intersection point earlier than before, so that can decrease the read access time. Based on SMIC 40nm complementary metal oxide semiconductor (CMOS) process, the novel high-speed sense amplifier is verified at an 8Mb PCRAM chip. The simulation results show that the read speeds of the novel circuit and the conventional circuit both are less than 1 ns when the Ge2Sb2Te5 (GST) resistance in set state (low resistance after set operation) is read. And the read speed can be accelerated more than 35.0% in the novel circuit compared to the conventional read circuit when the GST resistance in reset state (high resistance after set operation) is read. Monte Carlo simulation (the GST resistance in reset state) shows a 58ns worst read access time compared to the conventional circuit 111ns. And the read correctness of the novel read circuit was simulated in this paper. The simulation results show that the read validity can reach 98.8% in the worst reset resistance case (RGST=500kΩ). References | Related Articles | Metrics

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Application of a Geometric VOF Method in the Simulations of Sloshing Flow LI Jinlong,YOU Yunxiang,CHEN Ke 2019, 53 (8):  943-951.  doi: 10.16183/j.cnki.jsjtu.2019.08.008 Abstract ( 1513 )   PDF (3551KB) ( 771 )   Save The isoAdvector method is a new geometric volume of fluid (VOF) method. It overcomes the difficulties that the traditional geometric VOF methods cannot be applied on arbitrary polyhedral meshes. However, the isoAdvector method cannot be directly applied to sloshing simulations which involve the dynamic mesh technique. Thus, the motion flux correction is introduced, and the velocity correction for face-interface intersection line is proposed. The modified isoAdvector method can then be applied to the sloshing simulations. The non-resonant and the resonant sloshing under forced excitations and the single impace wave are simulated based on different VOF methods, and the results are compared with the experiments and the analytical solution. It demonstrates that the modified isoAdvector method can provide more accurate positions of the free surface and the hydrodynamic loads than the algebraic VOF method. In addition, the wave overturning and breaking can be predicted well without the wrinkles on the wave surface by using the modified isoAdvector method. A new approach for evaluating the interface thickness is proposed to analyze the reason for the improvement of the accuracy of free-surface elevations. References | Related Articles | Metrics

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Numerical Investigation of Three-Layer Liquid Sloshing in a Rectangular Tank LIU Dongxi,ZHUANG Suguo,WANG Jin,YOU Yunxiang 2019, 53 (8):  952-956.  doi: 10.16183/j.cnki.jsjtu.2019.08.009 Abstract ( 919 )   PDF (2358KB) ( 326 )   Save In the present study, the coupled level set and volume of fluid (CLSVOF) interface capturing method is employed to investigate the three-layer liquid sloshing in a rectangular wash tank installed aboard floating production storage and offloading (FPSO). The study shows that in the case of multi-layer liquid sloshing, the relevant physics can be much more complicated compared with the single liquid sloshing case. When the forced oscillation frequency is slightly away from the resonant frequency, there is an interesting phenomenon that the internal sloshing between liquid-liquid interfaces is significantly more pronounced than the actual oscillation of the top free surface. Another important issue for multi-interface problems is Kelvin-Helmholtz instability along the interface. Finally, the excellent capability of the CLSVOF method for multi-layer liquid sloshing simulation is validated by the qualitative comparisons of numerical and test results. References | Related Articles | Metrics

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Numerical Study on the Effect of Interceptors on the Resistance and Wake Field of Twin-Screw Ship SONG Kewei,GUO Chunyu,GONG Jie,LI Ping,WANG Wei 2019, 53 (8):  957-964.  doi: 10.16183/j.cnki.jsjtu.2019.08.010 Abstract ( 1215 )   PDF (4610KB) ( 400 )   Save Numerical calculation of DTMB5415 ship model with three different depth interceptors were carried out based on RANS（Reynolds-averaged Navier-Stokes） method in order to study the influence of interceptors on the ship resistance and wake field. The hydrodynamic performance of the ship with and without interceptor was analyzed in detail. Meanwhile, the variation of stern waveform, the hull pressure and the axial flow field were discussed. The results shown that the installation of interceptor could reduce the resistance of DTMB5415, and the average drag reduction rate could reach 4.19%. The increase of the virtual length of the hull and the improvement of the tail flow field of the transom stern ship reduced the wave making resistance, which was the main reason for the decrease of the total resistance. The existence of interceptor increased the boundary layer thickness at the ship stern and the axial nominal wake, meanwhile, the average wake fraction at the propeller disk increased by 11.9% when Fr=0.35 and d/LPP=0.0015, where Fr is Froude rumber, d is the depth of the spoiler and LPP is the length of the ship. References | Related Articles | Metrics

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Analysis of Tools Wear for Earth Pressure Balance Shield Based on Torque Energy of Cutterhead RONG Xuening,LU Hao,WANG Mingyang,WEN Zhu,RONG Xiaoli,Wang Zhen 2019, 53 (8):  965-970.  doi: 10.16183/j.cnki.jsjtu.2019.08.011 Abstract ( 1098 )   PDF (1124KB) ( 351 )   Save Excessive wear of cutting tools has been reported in some earth pressure balance tunneling project in gravel and the intermediately weathered mudstone. In order to reasonably organize the changing work, the wear of the cutting tools should be predicted. Based on the operational data collected from 20 units of Chengdu Metro, the torque energy of cutterhead was chosen as the input parameter of cutter wear model. A relationship between the number of cutter changes and the torque energy was fitted. The volume of foaming liquid was then added to develop a multiple regression model, which can further improve the prediction precision of tools wear. The result shows that the number of cutter replaced increases with the increase of torque energy or the decrease of volume of foaming liquid. The relationship between the number of cutter replaced and the two input parameters is statistically significant. The number of cutter replaced for the gravel and the intermediately weathered mudstone both agree with the multiple regression model. For different soil types, different fitting parameters are observed. The multiple regression model gives more reasonable predictions than the model based on excavated length and the JTS model. References | Related Articles | Metrics

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Effect of Surface and Adhesive-Bonded Properties of Carbon Fiber Reinforced Plastic/Polymer and Atmosphere Plasma Processing LIU Xiaodong,WU Lei,KONG Liang,WANG Min,CHEN Yidong 2019, 53 (8):  971-977.  doi: 10.16183/j.cnki.jsjtu.2019.08.012 Abstract ( 1142 )   PDF (7588KB) ( 524 )   Save In order to improve the surface infiltration of carbon fiber reinforced plastic/polymer (CFRP) and improve the bonding strength, the CFRP bonding surface was pretreated by the normal temperature and pressure air plasma treatment method, the contact angle of CFRP under different pretreatment parameters was tested, the surface energy was calculated. By using atomic force microscope, Fourier infrared spectrometer and X-ray photoelectron spectrometer, the physical and chemical properties of CFRP surface were analyzed under different treatment parameters, and 4 kinds of adhesives were used to test the tensile shear strength of bonding joints. The results show that the distance between the nozzle and the CFRP surface is 6mm, the nozzle movement speed is 50 mm/s as the best treatment condition. After plasma treatment, the contact angle between CFRP and water is reduced from 114° to 23°, and the surface can be raised from 32.49mJ/m2 to 72.19mJ/m2. Plasma treatment enhances the epoxy functional groups on the surface of CFRP, reduces the surface roughness, forms a large number of micro-scale gullies on the surface. The use of plasma treatment significantly improves the tensile shear strength of epoxy adhesive joints, so that the failures such as the interface failure and the substrate damage decrease, but pull shear strength of polyurethane adhesive joints changes little. The failure form is transformed from the composite failure of the interfacial adhesive layer to pure interface failure. References | Related Articles | Metrics

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Query Optimization of Data Based on Window Function and Distributed Cluster in Visual Academic Search System LUO Xiyi,HUO Xiaoyang,FU Luoyi 2019, 53 (8):  978-982.  doi: 10.16183/j.cnki.jsjtu.2019.08.013 Abstract ( 1154 )   PDF (579KB) ( 338 )   Save In order to address the issue of the poor performance of traditional MySQL database in application scenarios of densely analytical query requests and massive data processing, we proposed an approach based on window functions for analytical SQL query optimization. The approach replaces the fundamental grouping operation by the partitioning operation. In addition, we also designed distributed clusters based method for massive data query optimization, the method utilizes the in-memory columnar storage technology and Spark cluster’s distributed computation to lift the query performance. Meanwhile, the validity of the proposed approaches has been verified by typical analytical SQL queries. Experimental results show that the proposed methods have improved the query performance significantly, as the query optimization based on SparkSQL has reduced the execution time by a wide margin compared to traditional relational database MySQL. These proved the effectiveness when the methods are applied in AceMap, a visual academic search system. References | Related Articles | Metrics

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Improved Residual Encoder-Decoder Network for Low-Dose CT Image Denoising ZHANG Yungang,YANG Jianfeng,YI Benshun 2019, 53 (8):  983-989.  doi: 10.16183/j.cnki.jsjtu.2019.08.014 Abstract ( 1381 )   PDF (5994KB) ( 408 )   Save Aiming at the complex noise and artifacts in low-dose CT images, an improved residual encoder-decoder network for low-dose CT image denoising is proposed. The original residual encoder-decoder network consists of a series of convolution and deconvolution layers, and learns the residuals through shortcut connections. The improvement method mainly includes three aspects: firstly, batch normalization is introduced to improve the denoising performance of the network; secondly, dilated convolution is used to replace normal convolution so as to reduce the parameters in the network without degrading the denoising performance; besides, the number of feature maps in the hidden layer of the network has been adjusted to further optimize the network performance and complexity. Experimental results show that the improved network significantly reduces the complexity and also improves the denoising performance. References | Related Articles | Metrics

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Towing Winch Control System for a New Cable Laying Ship CHEN Qi,LI Gelun 2019, 53 (8):  990-999.  doi: 10.16183/j.cnki.jsjtu.2019.08.015 Abstract ( 1308 )   PDF (1892KB) ( 445 )   Save A towing winch control system based on industrial ethernet and programmable logic controller is designed for a new cable laying ship. An automatic cable arrangement system and a constant tension controller based on the fuzzy adaptive P+ID algorithm are proposed to improve the intelligence of the towing winch control system. The comparative studies of the proposed constant tension controller based on the fuzzy adaptive P+ID and conventional PID controllers were conducted, and the simulation results show that the fuzzy adaptive P+ID controller designed in this paper has a better performance than the PID controller. The real applications under harsh sea conditions demonstrated the robustness and effectiveness of the automatic cable arrangement system and the constant tension controller. References | Related Articles | Metrics

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Hybrid Genetic Algorithm for Solving Multi-Depot Joint Distribution Routing Problem FAN Houming,XU Zhenlin,LI Yang,LIU Wenqi,GENG Jing 2019, 53 (8):  1000-1009.  doi: 10.16183/j.cnki.jsjtu.2019.08.016 Abstract ( 1099 )   PDF (1561KB) ( 803 )   Save There are problems of traditional genetic algorithm in solving multi-depot vehicle routing problem. First, variable chromosome length produced by conventional coding techniques leads to low computation efficiency and easily produces infeasible solutions. Second, parental genetic operators have less efficient during perturbation. And it is difficult to balance the relationship between elite proportion and population diversity, search depth and search breadth in different evolutionary populations. This paper designs a hybrid genetic algorithm to solve the problem, and the distribution network information is separately expressed in the encoding and decoding method to improve the computational efficiency. The control parameters of balanced elite ratio and population diversity are introduced in the selection operation. In addition, an adaptive search range strategy is proposed to effectively balance the relationship in both search depth and breadth. Through experimental results and comparative analysis, the proposed algorithm is verified. The research results provide a new method to solve the multi-depot vehicle routing problem and can also provide guidance for related logistics distribution decisions. References | Related Articles | Metrics

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Blowing Effect Analysis of Single Saturated Liquefied Natural Gas Droplet Evaporation in Its Vapor DENG Jiajia,XU Jian,LU Jinshu,SHI Dunzhang 2019, 53 (8):  1010-1016.  doi: 10.16183/j.cnki.jsjtu.2019.08.017 Abstract ( 983 )   PDF (1513KB) ( 368 )   Save A novel model was built based on the computational fluid dynamics method. By multiple temperature differences, the static and moving liquefied natural gas (LNG) droplets of multiple relative velocity differences and multiple droplet diameters evaporation were simulated. Their blowing effects were identified. It was found that the higher vapor temperature is, the bigger relative velocity and the bigger diameter are, and they could enhance the droplet interface heat transfer rate. As the increase of vapor temperature, the temperature boundary layer becomes thicker and the thickness ratio becomes larger, but the heat transfer ratio presents a piecewise linearity characteristic. The piecewise linearity critical point of moving droplet evaporation is lower than the static droplet evaporation, but the blowing effect is bigger. The blowing effect is enhanced because vapor temperature increases. The blowing effect becomes weaker as the relative velocity increases, the blowing effect could be omitted when the relative velocity is bigger than 18m/s. The blowing effect almost keeps the same as the diameter increases. References | Related Articles | Metrics