Table of Content

28 May 2019, Volume 53 Issue 5 Previous Issue    Next Issue

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The Creep Properties and Numerical Simulation for PMMA Window GUO Dayou, HUANG Xiaoping, WANG Fang 2019, 53 (5):  513-520.  doi: 10.16183/j.cnki.jsjtu.2019.05.001 Abstract ( 877 )   PDF (2489KB) ( 557 )   Save The traditional linear elastic model demonstrates large limitation to simulate the creep deformation of the polymethyl methacrylate(PMMA) observation window on human occupied deep-sea vehicle. A linear viscoelastic constitutive model was built based on Prony series form. The mass scaling method together with the equivalent duration method was introduced to accelerate FEM analysis. The numerical-simulation results showed much stability and fitted well with test data. It was concluded that PMMA window showed viscoelastic behavior when loaded gradually to a high level at room temperature. So the viscoelasticity must be considered during a whole loading-holding process. Under quasi-static condition, traditional static FEM was replaced by dynamic explicit FEM which is adaptive to the time-varying property of PMMA viscoelasticity. It was also found that a fillet could help prevent local stress concentration and improve grid convergence. References | Related Articles | Metrics

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Preparation and Characterization of Bioactive Mg-P Coating on the Biodegradable Porous Pure Zn Scaffold HOU Yi,JIA Gaozhi,HUANG Hua,YUAN Guangyin 2019, 53 (5):  521-528.  doi: 10.16183/j.cnki.jsjtu.2019.05.002 Abstract ( 674 )   PDF (9626KB) ( 196 )   Save Recently, zinc and its alloys are proposed as a new generation of biodegradable metal for medical implant. Particularly, porous Zn-based scaffolds with 3D interconnected pore structure were considered as promising candidates for bone tissue engineering scaffold. In order to improve the cytocompatibility of porous Zn scaffold, a bioactive Mg-P coating was firstly prepared on the surface of porous pure Zn scaffold utilizing a chemical conversion method. The morphology, thickness, composition and bonding force of the Mg-P coating were characterized, and the effect of the Mg-P coating on the degradation behavior and biocompatibility of the porous pure Zn scaffold were systematically studied. The results showed that the Mg-P coating consisted of tiny strip-like Mg-P grains which stack with a flower-like orientation. The thickness of the Mg-P coating was about 10 μm and the bonding force was good. The Mg-P coated scaffold presents significantly decreased Zn2+ releasing rate and obviously improved the cytocompatibility, which demonstrates great potential in bone tissue engineering application. References | Related Articles | Metrics

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Micromotion Simulation and Optimal Design of Multi-Shank Fish-Bone-Shaped Electrode YIN Xuele，ZHANG Wenguang，TANG Jiaqi，YU Qian 2019, 53 (5):  529-534.  doi: 10.16183/j.cnki.jsjtu.2019.05.003 Abstract ( 906 )   PDF (1295KB) ( 244 )   Save In order to improve the long-term effectiveness of neural electrode, kinetic analysis of the micromotion at the electrode-brain interface was conducted using finite element simulation method. Compared with the traditional commercial electrode, the fish-bone-shaped electrode shows great effectiveness in reducing the micromotion induced injury. Moreover, the influence of the number of electrode shanks on micromotion induced injury of brain tissue was revealed. Based on the rationality and optimization principles of electrode site distribution, a novel multi-shank fish-bone-shaped electrode was developed. The electrode decreases the maximum strain, von Mises stress and total deformation of brain tissue by 73.23%, 48.78% and 76.92% respectively compared with the original one. In addition, the novel electrode performs better than the commercial three-shank electrode with the same size and site distribution when both of the electrodes collect the same electrical signal. The results reveal that the novel electrode reduces the strain in the brain tissue considerably, and is expected to improve the lifetime of electrode effectively. References | Related Articles | Metrics

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Constitutive Model of Soft Soil After Considering Small Strain Stiffness Decay Characteristics ZHANG Shuo,YE Guanlin,ZHEN liang,LI Mingguang,CHEN Chaobin 2019, 53 (5):  535-539.  doi: 10.16183/j.cnki.jsjtu.2019.05.004 Abstract ( 1022 )   PDF (881KB) ( 288 )   Save Although the Shanghai soil unified model can describe the influence of soil structure and over consolidation, it cannot simulate the highly nonlinear modulus in small strain range. In this paper, combined with the classical theory of small strain stiffness, a small strain constitutive model based on Shanghai soil unified model is developed. The small strain constitutive model can describe the change rule of soil stiffness in the small strain range. The capability of the model is checked by the triaxial compression test results on Shanghai shallow soil. The results show that small strain constitutive model can describe that soil stiffness in the small strain range has initial high modulus and the non-linear attenuation characteristics, and the influence of structure and over consolidation on soil can also be reproduce well by the model. References | Related Articles | Metrics

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Coupling Effects of Liquid Loading Vessels in the Floating Liquefied Natural Gas System ZHAO Dongya,HU Zhiqiang,CHEN Gang 2019, 53 (5):  540-548.  doi: 10.16183/j.cnki.jsjtu.2019.05.005 Abstract ( 921 )   PDF (1662KB) ( 231 )   Save This study develops a program to investigate the coupling effects between liquid sloshing and vessel’s motion in the floating liquefied natural gas (FLNG) system. In the program, hydrodynamic coefficients of vessel in frequency-domain are solved and solution of vessel’s motion in time-domain is calculated based on impulsive response function (IRF), liquid sloshing model is built based on potential flow theory and is solved by boundary element method. The solution of vessel’s motion and liquid sloshing are coupled in time domain through iteration method. Model tests of solid and liquid vessels in waves are conducted to validate the feasibility of the program. The coupling mechanism of liquid loading vessel is studied based on numerical and experimental results, and effects of liquid tank arrangement on vessel’s responses are discussed. It is found that vessel’s sway and roll motions are significantly affected by liquid sloshing in tank, while heave motion is slightly affected; the change of tank width can reduced the wave elevation caused by roll motion, and sway motion excited sloshing properties is mainly related to the natural sloshing frequency; the vertical position of liquid tank only affects the coupling effects of sloshing with roll motion mode and has no influences on coupling with sway motion mode. References | Related Articles | Metrics

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Formation Control of Multiple Autonomous Underwater Vehicles Based on Sensor Measuring System PANG Shikun,WANG Jian,YI Hong,LIANG Xiaofeng 2019, 53 (5):  549-555.  doi: 10.16183/j.cnki.jsjtu.2019.05.006 Abstract ( 1335 )   PDF (1055KB) ( 400 )   Save Autonomous underwater vehicle (AUV) formation is of significance to the efficiency and viability of improving underwater operating. Leader-follower formation of AUVs is researched based on sensor measuring system aimed at the coordination control of AUV formation. The problems of communication delay and data lost caused by underwater acoustic communication can be avoided, and the reliability and survivability of the formation system can be improved. Firstly, the reference route of follower AUVs is generated according to the position information of leader AUV and the desired formation structure. The followers can measure the range and bear information of the leader, and then compare the date with the reference route. A back-stepping controller based on Lyapunov function is designed to make sure that the orbit of followers could converge to the reference trajectory in a short time and the desired formation can be achieved. The simulation analysis of formation control is conducted. The results show that the AUVs can preserve the designed formation, and the proposed method has a high feasibility. References | Related Articles | Metrics

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Short-Term Shipping Freight Volume Prediction Based on Temporal-Spatial Features CHEN Chen，WU Qing，GAO Song 2019, 53 (5):  556-562.  doi: 10.16183/j.cnki.jsjtu.2019.05.007 Abstract ( 981 )   PDF (843KB) ( 405 )   Save Considering spatial correlation in shipping network is an effective method to improve veracity of the short-term freight volume prediction. But the shipping network is much more complicated than the highway transportation. The high-dimensional data of shipping network cannot be used effectively. A short-term freight volume prediction model FR-NN which is based on frequent pattern mining and neural network is constructed. Frequent ports in cargo network are found out according to idea of frequent pattern mining, and they represent the main spatial relations in network. Neural network is used for fitting statistical relationships among ports. Example analysis shows that the model can improve veracity of the short-term freight volume prediction in different time particle sizes. Furthermore, the model can forecast to the weeks and days freight volume, that the time series method is not ideal for the prediction results. References | Related Articles | Metrics

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An Electromagnetic Bandgap Microstrip Line Interconnection with Noise Suppression WANG Xiangting,LI Xiaochun,MAO Junfa 2019, 53 (5):  563-568.  doi: 10.16183/j.cnki.jsjtu.2019.05.008 Abstract ( 763 )   PDF (2544KB) ( 375 )   Save In this paper, a microstrip transmission line interconnection and its design method are proposed based on the electromagnetic bandgap (EBG). It has good passband transmission characteristics and stopband rejection characteristics, so it can suppress simultaneous switching noise (SSN) and keep the signal integrity. The proposed EBG microstrip line interconnection is realized with printed circuit board (PCB) and measured with network analyzer. Simulation and experimental results of the S parameter of the proposed interconnection agree very well. Besides, comparison between the proposed interconnection with EBG etched on the signal line and the microstrip line with EBG structure etched on the ground plane of the same size show that the proposed interconnection has a stronger capability of suppressing SSN and better signal integrity. References | Related Articles | Metrics

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Time-Domain Analysis of Noise in Power/Ground Planes with Narrow Slots Based on WLP-FDTD SUN Wei,LI Xiaochun,MAO Junfa 2019, 53 (5):  569-574.  doi: 10.16183/j.cnki.jsjtu.2019.05.009 Abstract ( 998 )   PDF (748KB) ( 255 )   Save In this paper, a numerical method based on weighted Laguerre polynomials finite-difference time-domain (WLP-FDTD) is proposed to analyze noise propagating problem in power/ground planes with narrow slots. Firstly, the planes are divided into two parts, one is the planes, and the other is the slots. Then the planes are modeled as 2D equivalent circuit networks and the slots are modeled as coupled circuits. Finally, the equivalent 2D circuits are solved by WLP-FDTD. Numerical results show that the WLP-FDTD-based method can achieve higher efficiency than the traditional finite-difference time-domain method but the accuracies are the same. Therefore, the proposed WLP-FDTD-based method is suitable for accurate and efficient analysis of noise propagating on power/ground planes in high-speed circuits. References | Related Articles | Metrics

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NISI-MU-CDSK Communication System Based on Frequency Division Multiplexing ZHANG Gang,XU Lianbing,ZHANG Tianqi 2019, 53 (5):  575-583.  doi: 10.16183/j.cnki.jsjtu.2019.05.010 Abstract ( 829 )   PDF (1158KB) ( 193 )   Save In view of the defects of poor error performance in traditional correlation delay shift keying, a novel multi-user correlation delay shift keying with no intra-signal interference communication (NISI) system is proposed based on frequency division multiplexing (FDM). In the proposed system, the transmitter uses two branches those are orthogonal to each other and uses serial-parallel converter to transmit multi-bit information in one bit period, and it utilizes FDM to send the linear combination of simple addition and subtraction of two orthogonal chaotic signals and simultaneous information bearing signal. At the receiver, the received signals are noncoherent demodulation with the chaotic signals respectively to recover the multi-bit information signal. The bit error rate (BER) formula over Rayleigh fading channel is derived and Monte Carlo simulation experiments are worked. Theoretical analysis and simulation results show that with the increase of the number of users, the new scheme proposed in this paper can effectively improve BER performance and transmission rate, which indicates the good practical application feasibility. References | Related Articles | Metrics

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The Computing-Data File: A Key Technology of Applying Ternary Optical Computer JIN Yi,ZHANG Sulan,LI Shuang,SHEN Yunfu,OUYANG Shan,PENG Junjie 2019, 53 (5):  584-592.  doi: 10.16183/j.cnki.jsjtu.2019.05.011 Abstract ( 1066 )   PDF (1948KB) ( 412 )   Save This paper proposes a new theory and method of writing application program of ternary optical computer (TOC). The theory is to collect all of raw data and calculation rules into a special file which is called the computing-data file, or SZG file for short, and then send the file to the ternary optical computer by using an expansion command in application program. A multi-center onion diagram is used to show the programming platform’s architecture which involves two computing units, i.e., electronic processor and ternary optical processor. The important role of the SZG file of writing the application program is shown in the multi-center onion diagram. This paper also introduces the origin, history, format and generation method of the SZG file, and describes the main extended commands to programing language. Finally, a specific process of using the SZG file is introduced via a suitable example. The example is also tested in a TOC’s software simulation environment, and the correctness of this theory is proved by the test. The program technique proposed in this paper is an important reference for those computer systems which include various types of processors. References | Related Articles | Metrics

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Improved Smith Predictive Decoupling Control Based on Disturbance Observer for Compression Refrigeration System LI Donghui,GAO Feng 2019, 53 (5):  593-599.  doi: 10.16183/j.cnki.jsjtu.2019.05.012 Abstract ( 946 )   PDF (942KB) ( 331 )   Save Since compression refrigeration system has problems of delay, coupling and external disturbance, an improved Smith predictive decoupling control based on disturbance observer has been proposed. First, the disturbance observer is used to observe overall disturbances of the system in the conventional Smith predictive control structure. The time-delay element is linearized by first-order Pade model. Then a diagonal matrix is applied to decouple the compression refrigeration system. Finally, the tuning of the controller parameter is realized based on the minimization of ITAE criterion, and the robust stability of the whole control system is discussed. Through the simulation, the proposed method can provide a better decoupling, better robustness and immunity for the compression refrigeration system. Moreover, it saves about 0.6% energy. References | Related Articles | Metrics

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Modeling and Optimization of Resource Investment Problem with Resource Vacations LU Zhiqiang,SHI Ting 2019, 53 (5):  600-609.  doi: 10.16183/j.cnki.jsjtu.2019.05.013 Abstract ( 956 )   PDF (1321KB) ( 235 )   Save Considering problem that some key resources are unavailable during aircraft assembly process, resource investment problem with resource vacations was studied. A mathematical model with objective function of minimizing the resource usage cost was built. By analyzing the influence of resource vacation on decision of job start time, a genetic algorithm was designed to code job positions. By making full use of the information in the iteration process that different start times corresponded to different target values, a method which determined the job start time based on the probability distribution was put forward to improve the mutation operation. And branch-and-bound algorithm was used to make local improvement. Comparative computational results reveal that the algorithm mentioned above can obtain approximate solution for small scale case, and improves the accuracy about 3% for the larger scale case compared with existing algorithms. References | Related Articles | Metrics

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Automatic Identification System Signal Detection Algorithm Based on Improved Feedback Decision TANG Ran,ZHAO Yingxin,WU Hong 2019, 53 (5):  610-615.  doi: 10.16183/j.cnki.jsjtu.2019.05.014 Abstract ( 935 )   PDF (1001KB) ( 330 )   Save The shipborne automatic identification system (AIS) signals received by satellite based receiver have the advantages of low complex structure low signal to noise ratio (SNR). Moreover, the Gaussian pulse shaping filter in Gaussian filtered minimum shift keying (GMSK) modulation can cause inter-symbol interference (ISI)，and the non-coherent GMSK detector is sensitive to noise. To deal with these issues, a modified decision feedback algorithm is presented. It is to narrow the bandwidth of postdetection filter to sufficiently suppress the noise in the output of frequency discriminator. Meanwhile, we adjust the feedback level according to the bandwidth of the postdetection filter in order to compensate for the resulting distortion as well as ISI caused by Gaussian filter. We also design a method to calculate the actual feedback level for the proposed modification in practical system by utilizing the synchronization preamble and starting flag in AIS frame. Simulation results show that a bit error ratio (BER) of 10-5 can be obtained as the SNR is 4.5dB by using the proposed method. Its simple structure and effectiveness enable its promising application in other GMSK mobile systems. References | Related Articles | Metrics

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Simulation on Mechanical Properties of Resistance Element Welding of Aluminum and Steel HE Guanzhong,LOU Ming,MA Yunwu,LI Yongbing 2019, 53 (5):  616-623.  doi: 10.16183/j.cnki.jsjtu.2019.05.015 Abstract ( 981 )   PDF (15942KB) ( 365 )   Save The mechanical properties of resistance element welding (REW) joints are decided by both effects of fusion welding and mechanical joining. The mechanical properties of REW for aluminum alloy to steel could be effectively studied by three-dimensional finite-element (FE) models. The modeling input consists of cross-section profile of joint observed by metallography, and stress-strain parameters of regional materials obtained by hardness test and empirical formula. Based on this new modeling method, the geometrical evolution and stress distribution during the mechanical testing of REW joints are studied systematically. Via comparing with parallel experimental results, the failure mode of REW joints is analyzed, which provides useful reference to understand the failure mechanism of REW joints. References | Related Articles | Metrics

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Predication of the Titanium Alloy’s Chip Morphology Based on TANH Constitutive Model and Smoothed Particle Hydrodynamic Method NIU Weilong，MO Rong，SUN Huibin，HAN Zhoupeng 2019, 53 (5):  624-632.  doi: 10.16183/j.cnki.jsjtu.2019.05.016 Abstract ( 1009 )   PDF (3541KB) ( 229 )   Save By implementing a TANH constitutive equation, a cutting model is established with smoothed particle hydrodynamic (SPH) method to simulate the titanium alloy’s cutting process. The new model effectively avoids the element distortion problem which always occurs in the traditional cutting model based on the finite element method (FEM). Additionally, the correction parameters of TANH equation are calibrated with control variable method. Compared to the traditional Johnson-Cook constitutive model, the new model takes the strain softening into account, describes the dynamic mechanical properties of the material more accurately under a large strain condition and dynamic recrystallization mechanism. The new model also explains the formation and mechanism of saw-tooth chips very well in the cutting process of titanium alloy. Compared with experimental results, simulation results show the new cutting model predicts the chip morphology and cutting force accurately. References | Related Articles | Metrics

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Dynamic Wetting Characteristics of Droplets in a Tool-Workpiece-Chip Slit XU Ming, YU Xin, NI Jing 2019, 53 (5):  633-638.  doi: 10.16183/j.cnki.jsjtu.2019.05.017 Abstract ( 946 )   PDF (3317KB) ( 298 )   Save In view of the difficulty in observing and analyzing the wetting spreading behavior of cutting fluid droplets in the slit formed by tool-workpiece-chip (TWC) in cutting process, a simulated TWC micro-slit was made up of a transparent quartz brick and a piece of stainless-steel plate with grooves. The dynamic wetting process of droplets in the slit was recorded by a high-speed camera with microscope function. Based on the image processing technology, the data in the experimental video frames were extracted and analyzed. The two-dimensional diffusion process of droplets in micro-slits was described by Logistic model. Combined with the parameters of the model, the relative size of penetration velocity in slits with different heights was qualitatively described. It is found that when the water droplets are spread in slits with height below 200 μm, the flow rate into the slit decreases with the slit height reduces, which indicates that it is still more and more difficult for droplets to infiltrate into the slit although the capillary pressure increases with the decrease of slit. This conclusion was verified by the average results of repeated experiments. References | Related Articles | Metrics