Table of Content

28 January 2019, Volume 53 Issue 1 Previous Issue    Next Issue

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The Application of Novel Synthetic Biology Technology in Precisely Regulating Gene Expression and Promoting the Efficiency of Fatty Acid Biosynthesis WANG Yushu, HE Lin, MA Gang 2019, 53 (1):  1-10.  doi: 10.16183/j.cnki.jsjtu.2019.01.001 Abstract ( 1007 )   PDF (1530KB) ( 497 )   Save Gene expression is one of the most essential activities in life, so exerting the accurate artificial regulation on gene expression is an important method to manipulate protein synthesis and physiological activity. The International Genetically Engineered Machine Competition (iGEM) team from Shanghai Jiao Tong University has exploited three types of innovative genetic regulatory devices based on the concept of synthetic biology since the first participation in 2009, including rare codon switch, membrane scaffold and light-controlled CRISPR interference (CRISPRi) system. By inserting an appropriate number of rare codon right after the start codon of target genes, the precise regulation of gene expression can be achieved so as to manipulate the reaction of a multi-enzyme system in its optimal stoichiometric ratio. Membrane scaffold can anchor target proteins on the cell inner membrane, which shortens the space distance between different proteins, and accelerates the enzymatic reaction rate, while light-controlled CRISPRi system has innovatively combined biological light sensor and emerging CRISPRi technique to achieve the precise regulation of endogenous genes expression on transcriptional level through light signal. These new technologies have favorable applications in improving the fatty acid synthesis and secretion efficiency in Escherichia coli. References | Related Articles | Metrics

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Tensile Behavior and Failure Mechanisms of Plain Weave SiC/SiC Composites at Room and High Temperatures CHEN Mingming, CHEN Xiuhua, ZHANG Daxu, WU Haihui, GUO Hongbao, GONG Jinghai 2019, 53 (1):  11-18.  doi: 10.16183/j.cnki.jsjtu.2019.01.002 Abstract ( 993 )   PDF (2076KB) ( 273 )   Save Monotonic tensile experiments at room temperature and 1200℃ were performed to investigate the mechanical behaviour of 2D-SiC/SiC composites. The microstructures of specimens were observed by using scanning electron microscope to analyse the damage modes and failure mechanisms. The results indicate that the stress-strain responses of 2D-SiC/SiC composites under tensile loading at both room temperature and 1200℃ are bi-linear and damage appears at the high stress level. Their tensile strengths are fairly close, but the fracture strain at 1200℃ is higher than that at room temperature. Specimens at both room and high temperature demonstrate ductile behaviour, but their pullout length of fibre and smoothness of fracture surfaces are different. Transverse matrix cracking, longitudinal tensile fractures of warp tows with serious interface debonding, and axial splitting failure of weft tows with intact fibres are the main damage mechanisms. The high temperature oxidation was found to have an influence on the properties of fibre-matrix interface of 2D-SiC/SiC composites. The weak interface and decrease of interfacial sliding stress result in the longer pullout length of fibre at 1200℃ in the oxidation environment, and therefore, 2D-SiC/SiC composites has high fracture toughness at 1200℃. References | Related Articles | Metrics

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Stochastic Defect Method for Finite Element Simulation of Buckling Problems YAN Di, SU Qi, LI Siping 2019, 53 (1):  19-25.  doi: 10.16183/j.cnki.jsjtu.2019.01.003 Abstract ( 1242 )   PDF (1084KB) ( 281 )   Save In view of limitations of finite element simulation method of bifurcation buckling in literature, this article presents to introduce stochastic defects in ideal artifacts to transform eigenvalue buckling problems into geometrically nonlinear static deformation problems. The simulation on stability problems of columns and buckling of elastic foundation beam indicates that stochastic defect method can calculate both the first mode and higher modes of buckling. In this article, the first and the second buckling mode by stochastic defect method are presented for stability problems of columns. Furthermore, this article points out limitations of introducing defect by influencing factors in some literature and indicates the applicability of stochastic defect method on nonlinear buckling problems by calculating the buckling of rectangular delamination bridged by fibers. Meanwhile, by contrasting results of different scales defect, this article provides some suggestions to implement this method. References | Related Articles | Metrics

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Reliability-Based Design Optimization of Ship Structures Based on SMOTE Algorithm LONG Zhou, CHEN Songkun, WANG Deyu 2019, 53 (1):  26-34.  doi: 10.16183/j.cnki.jsjtu.2019.01.004 Abstract ( 1168 )   PDF (1639KB) ( 291 )   Save Aimed at the problem that ship structures reliability-based design optimization has poor efficiency and difficult convergence due to high nonlinearity, a reliability-based design optimization of ship structures based on SMOTE (synthetic minority oversampling technique) algorithm is proposed. The innovation is to establish an improved BP (back propagation) neural network by SMOTE algorithm and the limit state function with high approximation could be set up with fewer samples, which overcomes the shortcoming that old model cannot satisfy both accuracy and efficiency requirements. Moreover, the feasibility of establishing BP neural network model by SMOTE algorithm has been proved by a mathematical instance. Then put the improved BP neural network and simulate anneal arithmetic into single loop approach optimized strategy to solve the issue of ship structure reliability-based design optimization. The result confirms the efficiency and accuracy of the model. In addition, the proposed model can provide an idea for large engineering structures reliability-based design optimization. References | Related Articles | Metrics

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Improvements of Scaling Method Recommended by ITTC at a Lower Reynolds Number Range YAO Huilan, ZHANG Huaixin 2019, 53 (1):  35-41.  doi: 10.16183/j.cnki.jsjtu.2019.01.005 Abstract ( 1429 )   PDF (2218KB) ( 334 )   Save A transition model based on unstructured mesh was applied for simulation of the model and full scale propeller with varied Reynolds number (Re) on the commercial software STAR-CCM+platform. Changes of boundary-layer flow over blade face and blade back with Re were studied. Numerical results of friction coefficient of the 0.75R blade section were compared with those calculated by the ITTC formulas and the plate resistance formulas. The scaling method recommended by ITTC was improved at low Reynolds number range that two formulas were proposed for calculating viscous force coefficients of propeller blade face and blade back separately. Results show that the boundary-layer flow over blade face and blade back are different. Thus, different equations were needed to calculate the friction coefficients of suction side and pressure side of the blade section. Results show that when Re is small (close to the critical Re), results of the revised method are better than those of the ITTC method; when Re is greater than 1.0×106, results by the two methods are basically the same; when Re continues to increase (greater than 2.0×106), results calculated by the two methods both deviate from the actual value with the increase of Re. References | Related Articles | Metrics

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Prediction of Internal Solitary Wave Loads on NANHAI 8 Semi-Submersible Platform CHEN Min, CHEN Ke, YOU Yunxiang, LI Fei 2019, 53 (1):  42-48.  doi: 10.16183/j.cnki.jsjtu.2019.01.006 Abstract ( 962 )   PDF (930KB) ( 240 )   Save A prediction method is established for internal solitary wave loads on NANHAI 8 semi-submersible platform based on internal solitary wave theory, Morison equation and pressure integral. A series of experiments were carried out to study the internal solitary wave loads in a wave flume. The inertial and drag coefficients in Morison equation for the platform have been determined by experimental results. It shows that the coefficients are not only related to Re number, KC (Keulegan-Carpenter) number and the layer thickness ratio, but also affected by the platform structures. The inertia coefficient decreases with KC number in power function, while the drag coefficient decreases with Re number in exponential function. References | Related Articles | Metrics

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Electrical Characteristics of Power Lithium-Ion Batteries for Full Ocean Depth Submersible ZHOU Shiyao, CHEN Ziqiang, ZHENG Changwen, HUANG Deyang, LIU Jian, GE Yunlong 2019, 53 (1):  49-54.  doi: 10.16183/j.cnki.jsjtu.2019.01.007 Abstract ( 1103 )   PDF (972KB) ( 243 )   Save A series of lithium iron phosphate batteries characteristics test were taken to analyzing the relationship between batteries electrical characteristics and the temperature or pressure. The relationship between maximum depth of discharge (DOD), internal resistance and open circuit voltage with temperature and pressure was studied. The results show that under atmospheric pressure and 3℃, the maximum DOD of the battery is greatly attenuated. The ohmic internal resistance and the polarization internal resistance increase significantly, and the open circuit voltage is slightly reduced. Compared with atmospheric pressure and 20℃, at the high pressure of 100MPa and 20℃, the maximum discharge depth of the battery is greatly attenuated, the ohmic internal resistance is slightly increased, and the open circuit voltage is slightly lowered. References | Related Articles | Metrics

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Parameter Analysis of Vehicle-Pedestrian Accidents in Untypical Contact State Based on Orthogonal Tests and Polynomial Regression Analysis ZHANG Dongming, ZHANG Xiaoyun, YANG Xiaobo, HOU Xinyi 2019, 53 (1):  55-61.  doi: 10.16183/j.cnki.jsjtu.2019.01.008 Abstract ( 950 )   PDF (751KB) ( 228 )   Save Aimed at traffic accidents in untypical contact state such as side impact accidents and oblique impact accidents, the relationship between optimized parameters and input parameters was fitted by the combination of orthogonal test and polynomial regression analysis based on a real-world accident, and the initial parameters in this accident was optimized. Simulation results show that this method has a high degree of accuracy in optimizing initial parameters. Meanwhile, the injury of pedestrian in numerical simulation agreed with the conclusions of medical report, which further verified the reliability and rationality of simulation. References | Related Articles | Metrics

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Distortion Prediction and Geometry Compensation Method for Laser Welding-Induced Distortion of Body-in-White WANG Qing, LIU Zhao, HUANG Pinghua, ZHU Ping 2019, 53 (1):  62-68.  doi: 10.16183/j.cnki.jsjtu.2019.01.009 Abstract ( 1143 )   PDF (1291KB) ( 326 )   Save Aimed at the problem that hot-forming steel parts occur large distortion after the laser welding of body-in-white, a geometry compensation method was presented to eliminate the impact of weld-induced distortion, and the process of this method was established. The welding-induced distortion was accurately predicted based on finite element method. The geometry compensation solution of B-pillar was obtained utilizing optimal Latin hypercube method, Kriging metamodel technology and particle swarm optimization algorithm. Results show that the optimized B-pillar is in a good agreement with the ideal design after laser welding procedure. References | Related Articles | Metrics

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Dynamic Decision Making for the Integrated Allocation of Berth and Yard Resources at Import/Export Container Terminals HAN Xiaole, JU Liuhong, QIAN Lina, LU Zhiqiang 2019, 53 (1):  69-76.  doi: 10.16183/j.cnki.jsjtu.2019.01.010 Abstract ( 1295 )   PDF (959KB) ( 240 )   Save The multi-stage decision process of integrated resource reallocation at import/export container terminals is addressed, considering the uncertainty of vessel arrival time at operational level. To satisfy both robustness and flexibility requirement, a dynamic decision framework based on 2-stage approximation is proposed. At each decision point, the dynamics of information and operation are analyzed, based on which the vessel classification is proposed and a stochastic-scenarios-based mixed integer programming model is established. The model is to determine both the 1st-stage fixed decisions and the 2nd-stage adjustable pre-decisions, with the objective of minimizing expected dwelling time of all vessels. Dependent on such decision logic, a two-stage Tabu Search is proposed to solve the optimization problem at each decision point. Numerical experiments verify the efficiency and effectiveness of the proposed decision method, which makes better utilization of updating certain and uncertain information. References | Related Articles | Metrics

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Crashworthiness Research of Honeycomb-Filled Thin-Walled Structure Under Multi-Impacting Cases ZHANG Yong, YAN Xiaogang, ZENG Yi, LAI Xiongming 2019, 53 (1):  77-84.  doi: 10.16183/j.cnki.jsjtu.2019.01.011 Abstract ( 926 )   PDF (1381KB) ( 291 )   Save A square honeycomb-filled thin-wall composite structure is proposed, and the crashworthiness of honeycomb filled structure and corresponding unfilled (thin-walled empty tube) structures under 12 kinds of impact conditions are systematically studied by experimental research and numerical analysis. At the same time, numerical optimization design of honeycomb filled structure is carried out by combining Kriging approximation technique and small population genetic algorithm. The results show that under various impact conditions, the energy absorption of the honeycomb filled structure is higher than that of the thin-walled empty tube structure, and the impact angle and velocity have significant effects on the energy absorption performance of the honeycomb filled structure. At the same impact velocity, the energy absorption of the honeycomb filled structure decreases as the impact angle increases. At the same impact angle, the energy absorption of the filled structure increases as the impact velocity increases. The Kriging approximation technique and the small population genetic algorithm optimize the optimal parameter matching of the honeycomb filled structure obtained by optimizing the honeycomb filled structure, which can improve the energy absorption of the honeycomb filled structure. References | Related Articles | Metrics

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Interaction Between Mono-Pile and Porous Seabed Under Cnoidal Wave and Pile Rocking ZHANG Yizhou, LIAO Chencong, CHEN Jinjian 2019, 53 (1):  85-92.  doi: 10.16183/j.cnki.jsjtu.2019.01.012 Abstract ( 1006 )   PDF (1537KB) ( 178 )   Save For research of offshore mono-pile foundation in shallow water, a 3-D model is established by combining wave, seabed and mono-pile to investigate dynamic response of coupled seabed and mono-pile interaction under cnoidal wave and pile rocking caused by wind and flow motion. The cnoidal wave model is governed by Navier-Stokes equations to generate cnodial wave motion. The seabed model is treated as an isotropic porous medium and the dynamic response of soil and pore water is simulated by Biot’s equations. The mono-pile is treated as deformable elastic body and pile rocking is simulated by cyclic horizontal displacement. Based on validation for simulation accuracy of present model, dynamic response of mono-pile displacement, pore water pressure and liquefaction in the vicinity of the mono-pile subject to cnoidal wave are analyzed. Furthermore, parametric studies are conducted to discuss the effect of wave and seabed characteristics. The results show that the pile rocking effect leads to local change of pore pressure at the top part of mono-pile, and slows down the rate of pore pressure decrease along seabed depth. In addition, the variations of wave and seabed parameters make obvious effects on pore pressure distribution. References | Related Articles | Metrics

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Analysis of Wave-Induced Liquefaction of Seabed with Variation in Permeability Anisotropy RONG Fu, LIAO Chencong, TONG Dagui, ZHOU Xianglian 2019, 53 (1):  93-99.  doi: 10.16183/j.cnki.jsjtu.2019.01.013 Abstract ( 1338 )   PDF (856KB) ( 348 )   Save In order to investigate the wave-induced seabed liquefaction with variation in permeability anisotropy, a two-dimensional integrated model for wave-seabed interactions was proposed in this paper. In the model the Reynolds-Averaged Navier-Stokes (RANS) equations and the Biot’s poro-elastic equations were taken as the governing equations for the wave model and seabed model respectively. The level set method (LSM) was used to track the free surface of water for modeling wave motion accurately. After the feasible of the present models were validated, the effects of wave parameters, soil saturation and permeability on the seabed liquefaction with variation in permeability anisotropy were further discussed. The analysis results indicated that both the wave parameters and soil saturation of seabed can significantly affect the wave-induced seabed liquefaction and the depth of maximum transient liquefaction of seabed increases with the increment of wave height, wave period and the decrement of degree of soil saturation. Maximum transient liquefaction of seabed depth is more sensitive to the variations of the permeability in vertical direction than the horizontal permeability. References | Related Articles | Metrics

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Analysis of the Effect of Pre-Hem Steel Stopping Position on Boundary Roll-in LI Dongwei, WANG Lei, ZHANG Cong, ZHAO Yixi 2019, 53 (1):  100-104.  doi: 10.16183/j.cnki.jsjtu.2019.01.014 Abstract ( 1136 )   PDF (984KB) ( 234 )   Save In order to study the effect of pre-hem steel stopping position on boundary roll-in, the hemming process of a front door was analyzed and modeled based on AutoForm. Relative stroke was defined to quantify the pre-hem steel stopping position. The analysis result was also verified by the experiments on the hemming machine, and a method of adjusting boundary roll-in was proposed based on the numerical and experimental analysis. The investigation shows that the boundary roll-in increases with the increase of the relative stroke, but the increasing process is non-linear. When the pre-hem steel has under stroke, the influence of the relative stroke on the boundary roll-in is relatively small. While a quadratic function fits the relation between boundary roll-in and relative stroke well when the pre-hem steel has over stroke. References | Related Articles | Metrics

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Formability of Flange Constraint Spinning for Aluminum Cup Part LIU Ruofan, YU Zhongqi, ZHAO Yixi, EVSYUKOV S A 2019, 53 (1):  105-110.  doi: 10.16183/j.cnki.jsjtu.2019.01.015 Abstract ( 993 )   PDF (1191KB) ( 176 )   Save In order to improve the spin-ability of AA2024-O, the limiting spinning ratios under the two different flange constraints (the single-side, the double-side) in a cup-shaped spinning were experimentally studied. In addition, the influence of the process parameters on the thickness of the spun part in single-side and double-side flange constraint spinning processes was analyzed by numerical simulation. The results show that the flange constraint method can increase the limiting spinning ratio compared with conventional spinning, and the double-side flange constraint method can increase more than the single-side flange constraint method; the thickness uniformity of the spun part in the double-side flange constraint forming is better than that in the single-side flange constraint spinning under the same conditions. At the same time, the friction coefficient at the blank-roller interfaces has little effect on thickness in the flange constraint methods, and the thickness first decreases and then stabilizes with increasing of the gap value between the blank and rollers in the double-side flange constraint spinning. References | Related Articles | Metrics

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Discharge Atomization Ablation Grinding Based on PID Pressure Servo Control QIU Mingbo, SHI Jingyun, YU Xiaochun, LIU Zhidong 2019, 53 (1):  111-117.  doi: 10.16183/j.cnki.jsjtu.2019.01.016 Abstract ( 864 )   PDF (1734KB) ( 185 )   Save To improve the efficiency of electrical discharge machining (EDM) ablation, this paper uses a sintered diamond electrode as the machining electrode, making use of grinding action of diamond particles, to achieve machining combined with high efficiency ablation and mechanical grinding. In the study, through gathering mechanical grinding force during machining, a control method based on force signal is proposed to ensure diamond particles grinding. In order to maintain the stability of pressure in the process, three control methods are proposed: inverse proportional control, fuzzy control and PID control. In addition, we use high strength steel as the workpiece and conduct three groups of machining efficiency comparative experiments. From these three groups of experiments, we conclude that the machining depth can reach to 14.5mm and the force range is less than 1.0N by using PID control method. PID control method has advantages over the other two in machining efficiency and stability. References | Related Articles | Metrics

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Reciprocating Dynamic Friction Characteristics of the Micro-Gap of the Valve Sleeve and the Valve Core of the Pneumatic Control Valve XU Jing, NI Jing, CHEN Yebo, JIN Yongtao, WU Can 2019, 53 (1):  118.  doi: 10.16183/j.cnki.jsjtu.2019.01.017 Abstract ( 966 )   PDF (1788KB) ( 213 )   Save Based on the equivalent principle of the influence of rounded punch and edge stress concentration theory, this paper proposed a dynamic friction characteristic model of single through hole that the shape of the contiguous border is changing precisely. Simultaneously, by means of introducing the coupling principle of multiple sets of through holes, the friction characteristic model was established when there were multiple through holes in the valve sleeve. By comparing the friction characteristic model with the experimental results, the micro-gap reciprocating dynamics frictional characteristic of the contact surface between the through hole of the valve sleeve and the valve body seal ring of the pneumatic valve were studied. The results showed that the friction characteristic model was feasible and effective. The edge stress concentration effect produced by the through holes has a great influence on the friction characteristics. The frictional force of the sleeve containing the through hole is higher than that of the non-perforated sleeve. Mass friction increases with the growing of length of the contact line of the through hole. The increase of the fillet radius can decrease the frictional force on the sealing surface of the through hole. The greater the fillet radius is, the more obvious the impact is. References | Related Articles | Metrics