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01 June 2019, Volume 24 Issue 3 Previous Issue    Next Issue

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Effect of Header Configuration on Refrigerant Distribution in Parallel Flow Microchannel Evaporators YU Dengjia (俞登佳), LIU Jinwei (刘金伟), Lü Hongbin (吕鸿斌), SHI Junye (施骏业), YOU Dian (游典), CHEN Jiangping* (陈江平) 2019, 24 (3):  273-280.  doi: 10.1007/s12204-019-2068-4 Abstract ( 485 )   PDF (3161KB) ( 143 )   The refrigerant flow distribution in the parallel flow microchannel evaporators is experimentally investigated to study the effect of header configuration. Six different configurations are tested in the same evaporator by installing insertion device and partition plate in the header to ensure the consistency of the other structure parameters. The results show that the uniformity of refrigerant flow distribution and the heat transfer rate are greatly improved by reducing the sectional area of header. The heat transfer rate can increase by 67.93% by reducing the sectional area of both inlet and outlet headers. The uniformity of refrigerant flow distribution and the heat transfer rate become worse after installing the partition plate in the insertion devices and changing the inner structure of the header further. References | Related Articles | Metrics

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Efficient Design and Optimization Method for Distributed Amplifiers ZHANG Ying* (张瑛), LI Zeyou (李泽有), LI Xin (李鑫), YANG Hua (杨华) 2019, 24 (3):  281-286.  doi: 10.1007/s12204-019-2069-3 Abstract ( 454 )   PDF (1821KB) ( 122 )   A novel design and optimization method for distributed amplifiers (DAs) is proposed to make the circuit design more convenient and efficient. This method combines artificial intelligence (AI) optimization with manual design by two loops, i.e., outer manual loop and inner AI loop. The layout design is followed by AI optimization to take more influencing factors such as parasitic effect into account for the practicability. A DA with three gain cells is designed and optimized in a standard 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology to verify the proposed method. With a chip area of only 0.55mm2, the DA provides 9.8 dB average forward gain from 1 to 15.2GHz. The output power at 1 dB output compression point is more than 7.7 dBm in the 2—14GHz frequency band and the peak power-added efficiency (PAE) is 10.6%. The measurement results validate the proposed method as a robust DA design procedure for improving circuit performance and design efficiency. References | Related Articles | Metrics

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Numerical Study on Groundwater Drawdown and Deformation Responses of Multi-Layer Strata to Pumping in a Confined Aquifer WANG Dafa (王大发), LI Mingguang *(李明广), CHEN Jinjian (陈锦剑), XIA Xiaohe (夏小和), ZHANG Yangqing (张扬清) 2019, 24 (3):  287-293.  doi: 10.1007/s12204-019-2070-x Abstract ( 588 )   PDF (424KB) ( 130 )   Pumping artesian water from porous media inevitably reduces the groundwater head and promotes soil consolidation, which may result in regional land subsidence. In this study, a fluid-mechanical coupled numerical model is developed to investigate the dewatering-induced groundwater drawdown and deformation responses for multi-layer strata. The relation between the stratum deformation and groundwater drawdown is discussed. The results show that the pumping process can be divided into four stages. The development of vertical deformation is inconsistent with the change of the pore pressure for the strata except for the confined aquifer at the early stage of pumping. The strata expand while the pore pressures reduce. This inconsistency may be due to the large unloading in the confined aquifer at the early stage of pumping. Soil arch comes into being owing to the constraint of the surrounding soils when the large unloading occurs in the confined aquifer; this can reduce the stratum compression and cause the expansion of the layers. It can be concluded that as the pumping continues, the decrease of the pore pressure dominates the vertical deformation and results in the soil compression in all strata. References | Related Articles | Metrics

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Genetic Algorithm Based Tikhonov Regularization Method for Displacement Reconstruction PENG Zhen (彭真), YANG Zhilong (杨枝龙), TU Jiahuang* (涂佳黄) 2019, 24 (3):  294-298.  doi: 10.1007/s12204-019-2060-z Abstract ( 560 )   PDF (304KB) ( 128 )   In this paper, a genetic algorithm based Tikhonov regularization method is proposed for determination of globally optimal regularization factor in displacement reconstruction. Optimization mathematic models are built by using the generalized cross-validation (GCV) criterion, L-curve criterion and Engl’s error minimization (EEM) criterion as the objective functions to prevent the regularization factor sinking into the locally optimal solution. The validity of the proposed algorithm is demonstrated through a numerical study of the frame structure model. Additionally, the influence of the noise level and the number of sampling points on the optimal regularization factor is analyzed. The results show that the proposed algorithm improves the robustness of the algorithm effectively, and reconstructs the displacement accurately. References | Related Articles | Metrics

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Hydraulic Geometry Relation for Navigable Canals Considering Ship Speed MAO Lilei (毛礼磊), CHEN Yimei *(陈一梅) 2019, 24 (3):  299-304.  doi: 10.1007/s12204-019-2048-8 Abstract ( 510 )   PDF (10099KB) ( 123 )   Definition of hydraulic geometry of navigable canals and its expression are studied in this paper. The hydrodynamic and morphologic characteristics of navigable canals are analyzed on the basis of the data collected from field surveys conducted at two segments of the Grand Canal in Jiangsu Province, China. The channel morphologic factor and the ship hydrodynamic factor are adopted to describe the hydraulic geometry relation of navigable canals. The correlation analysis shows that the ship hydrodynamics can be a dominant factor influencing the channel evolution with larger determination coefficient. Furthermore, the undetermined index in the proposed hydraulic geometry relation is also discussed, which indicates that the index related to the intensity of water flow (qualitatively reflected by the integrated ship flow intensity) is within a range of 0.5 to 1.0. References | Related Articles | Metrics

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Wave Forces and Moments on a Gravity Pier Foundation WEI Chengxun *(韦承勋), ZHOU Daocheng (周道成), OU Jinping (欧进萍) 2019, 24 (3):  305-312.  doi: 10.1007/s12204-019-2063-9 Abstract ( 346 )   PDF (4986KB) ( 133 )   In order to understand the wave forces and moments on a gravity pier foundation which consists of an upper column and a bottom gravity base, a model experiment with a scale of 1 : 60 has been conducted in a laboratory flume. A corresponding numerical calculation by using the boundary element method has been carried out to provide a comparative analysis. It is shown by the comparisons that the numerical wave forces and moments agree well with the experimental results. It is proved that the wave forces and moments acting on the foundation are completely in their inertia dominative areas for wave loads. With the diffraction effects considered into the inertia item, appropriate inertia coefficients are assessed by the experimental results for the inertia item of the Morison equation. The formula of the inertia item can be used to estimate wave forces and moments on such gravity foundations. References | Related Articles | Metrics

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Research on the Lightweight Design of Body-Side Structure Based on Crashworthiness Requirements ZHUANG Weimin (庄蔚敏), SHI Hongda* (施宏达), XIE Dongxuan (解东旋), CHEN Yanhong (陈延红), YANG Changhai (杨昌海) 2019, 24 (3):  313-322.  doi: 10.1007/s12204-019-2066-6 Abstract ( 542 )   PDF (9257KB) ( 138 )   Crashworthiness is the most significant variable during lightweight design of vehicle structures. However, crashworthiness studies using the single substructure-based method are limited due to the negligence of interactions among substructures. Thus, a whole structure-based study was conducted for the lightweight design of a body-side structure. In this study, a full finite element model was firstly created and then modified into a simplified model for structural improvements, where the major load-carrying subassemblies were improved from the perspectives of crashworthiness and manufacturing costs. Finally, sensitivity analyses were conducted to further optimize the strength distribution, based on which an adaptive response surface method was employed for thickness optimization of the structure. It is found that through the structural improvements and optimizations, the weight of the structure was significantly reduced even when its crashworthiness was improved. This indicates that the whole structure-based method is effective for lightweight design of vehicle structures. References | Related Articles | Metrics

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Analyzing the Influence of Aggregate Properties on Stopping Distance on Truck Escape Ramps QIN Pinpin *(覃频频), CHEN Chuice (陈垂策), GUO Huanliang (郭焕亮), HAN Yaqi (韩亚奇), MENG Qiang (孟强) 2019, 24 (3):  323-327.  doi: 10.1007/s12204-019-2062-x Abstract ( 404 )   PDF (266KB) ( 109 )   Although there are many studies involving influence of runaway truck entry speed and longitudinal grade on stopping distance, focusing on aggregate properties is scarce. This paper investigates the influence of the aggregate properties such as types of aggregate and river gravel radius on stopping distance through numerical analysis of particle flow code in two dimensions (PFC2D). The software is used to generate stopping distance data for two aggregate types and four group gravel radii under various approaching speeds and grades. The generated data are compared with the testing results of full-scale arrester bed. The simulated finding of this paper implies that types of aggregates and river gravel radii have a significant impact on the stopping distance for runaway truck on escape ramps. References | Related Articles | Metrics

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Signal Detection Algorithm Design Based on Stochastic Resonance Technology Under Low Signal-to-Noise Ratio JIANG Xiaolin* (江晓林), DIAO Ming (刁鸣), QU Susu (渠苏苏) 2019, 24 (3):  328-334.  doi: 10.1007/s12204-019-2071-9 Abstract ( 421 )   PDF (265KB) ( 112 )   In the current 4th generation (4G) communication network, the base station with the same frequency transmission makes a serious interference among adjacent cells, and information transmission is susceptible to interference such as channel multipath fading and occlusion effect. Detecting effectively spectrum signal under low signal-to-noise ratio (SNR), directly affects the whole performance of the wireless communication network system. This paper designs an energy signal detection algorithm based on stochastic resonance technology which transforms noise’s signal energy into useful signal energy, and improves output SNR. The energy signal detection algorithm realizes the function of providing effective detection of signal under low SNR, and promotes the performance of the whole communication system. References | Related Articles | Metrics

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High Performance SAR ADC with Mismatch Correction Latch and Improved Comparator Clock LIAN Pengfei *(廉鹏飞), WU Bin (吴斌), WANG Han (王晗), PU Yilin (蒲钇霖), CHEN Chengying (陈铖颖) 2019, 24 (3):  335-340.  doi: 10.1007/s12204-019-2065-7 Abstract ( 443 )   PDF (1214KB) ( 118 )   We propose a high performance 10-bit 100-MS/s (million samples per second) successive approximation register (SAR) analog-to-digital converter (ADC) with mismatch correction latch and improved comparator clock. Using a high-low supply voltage technology, the bias output impedance of the preamplifier of the comparator is increased. Therefore, the common mode rejection ratio (CMRR) of the comparator is improved, and further diminishing the signal-dependent offset caused by the input common-mode voltage variation. A digital-to-analog converter (DAC) control signal correction latch is proposed to correct the control signal error resulted from process mismatch. The 30-point Monte Carlo mismatch simulated results demonstrate that the minimum spurious-free dynamic range (SFDR) of the ADC is improved by 2 dB with this correction latch. To ensure sufficient high bit switching time of the DAC and sufficient low bit comparison time of the comparator, a data selector used in the comparator clock is presented. The optimized time distribution improves the performance of the SAR ADC. This prototype was fabricated using a one-poly-eight-metal (1P8M) 55 nm complementary metal oxide semiconductor (CMOS) technology. With measured results at 1.3V/1.5V supply and 100-MS/s, the ADC achieves a signalto- noise and distortion ratio (SNDR) of 59.4 dB and consumes 2.1mW, resulting in a figure of merit (FOM) of 31 fJ/conversion-step. In addition, the active area of the ADC is 0.018 8mm2. References | Related Articles | Metrics

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Analysis of Thermal-Fluid-Structure Coupling and Resonance Forecast for Link Butterfly Valve Under Small Opening LI Shuxun *(李树勋), ZHU Lu (朱禄), WANG Weibo (王伟波), XIAO Kuijun (肖奎军), XU Xiaogang (徐晓刚), ZHANG Baosheng (张宝生) 2019, 24 (3):  341-350.  doi: 10.1007/s12204-019-2061-y Abstract ( 437 )   PDF (7847KB) ( 122 )   When the link butterfly valve operates at a small opening degree in high temperature working conditions, it is prone to the problem that the valve is stuck, the strength is insufficient and the butterfly plate is violently vibrating. This paper shows simulation experiments of both thermal-fluid-structure coupling and resonance forecast about DN600 link butterfly valve in the working conditions of 250?C and 0.5MPa by ANSYS software. The medium is mixed with compressed air and flue gas. Flow field characteristics of the valve and stress deformation, modal and flow-induced vibration of butterfly plate are analyzed when the valve opening is less than 30%. The results indicate that, when the valve opening is less than 30%, fluid flow is relatively smooth in front of butterfly plate, a large number of vortexes are found behind the butterfly plate, and fluid flow is greatly chaotic in this position. The equivalent maximum stress and deformation of butterfly plate are relatively large when the valve locates in openings between 10% and 30%; the intensity of the butterfly plate is enough; the axial deformation does not impact opening and closing of the valve. The butterfly plate is likely resonant when the valve opening is less than 10%. The research of this paper provides a crucial reference for flow field characteristics of link butterfly valve, an analysis of intensity and rigidity of butterfly plate, and a resonance forecast of butterfly plate when the valve works in small opening. References | Related Articles | Metrics

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Degradation Reliability Analysis Based on TOPSIS Model Selection Method GU Yingkui *(古莹奎), SHEN Yanjun (沈延军), YU Dongping (余东平) 2019, 24 (3):  351-356.  doi: 10.1007/s12204-019-2067-5 Abstract ( 511 )   PDF (249KB) ( 110 )   It is necessary to determine the degradation path model of products at first when using the method based on degradation path model to evaluate the degradation reliability of products. At present, the degradation path model is mainly determined by scatter plots of degradation data. However, this method has strong subjectivity and is liable to cause the evaluation results to be inconsistent with the actual situation. In this paper, a degradation reliability analysis method based on TOPSIS (technique for order preference by similarity to an ideal solution) model selection is proposed, and its implementation process is given. The optimal degradation path model is selected according to the calculated proximity. With the help of TOPSIS method, various degradation path models can be selected and quantified, and the original degradation path method can be improved to avoid the risk of errors in product reliability evaluation caused by inaccurate subjective hypothesis, so as to ensure the objectivity and accuracy in the process of model determination. The validity and practicability of the proposed method are verified by the degradation analysis of the injector of a certain type of diesel engine. References | Related Articles | Metrics

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Comparison Between Different Finite Element Analyses of Unbonded Flexible Pipe via Different Modeling Patterns PANG Guoliang (庞国良), CHEN Chaohe* (陈超核), SHEN Yijun (沈义俊), LIU Fuyong (刘夫永) 2019, 24 (3):  357-363.  doi: 10.1007/s12204-019-2064-8 Abstract ( 475 )   PDF (8560KB) ( 114 )   Three kinds of models based on the same flexible pipe with 8 layers have been separately created to investigate the effects of different modeling approaches on numerical simulation results of finite element (FE) models for unbonded flexible pipes. Then the mechanical property of the unbonded flexible pipe under tension, torsion and bending load has been analyzed and compared via ABAQUS software on the basis of three created models. The research shows that different modeling methods of flexible pipes make a great difference in the results. Especially, modeling simplifications of the carcass and pressure armor have a great impact on the accuracy of the results. Model 3, in which the carcass is simulated by spiral isotropic shell and other layers are simulated by solid element, possesses good adaptability, which has been proved by comparing the experiment data and other models. This paper can offer a reference for the FE modeling methods’ selection and mechanical property analysis of unbonded flexible pipe. References | Related Articles | Metrics

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Research on Weibo Hotspot Finding Based on Self-Adaptive Incremental Clustering SONG Huilin (宋慧琳), PENG Diyun (彭迪云), HUANG Xin *(黄欣), FENG Jun (冯俊) 2019, 24 (3):  364-371.  doi: 10.1007/s12204-019-2072-8 Abstract ( 468 )   PDF (354KB) ( 109 )   Weibo, also known as micro-blog, with its extremely low threshold of information release and interactive communication mode, has become the primary source and communication form of Internet hotspots. However, characterized as a kind of short text, the sparsity in semantic features, plus its colloquial and diversified expressions makes clustering analysis more difficult. In order to solve the above problems, we use the Biterm topic model (BTM) to extract features from the corpus and use vector space model (VSM) to strengthen the features to reduce the vector dimension and highlight the main features. Then, an improved Weibo feature-incorporated incremental clustering algorithm and the Weibo buzz calculation formula are proposed to describe the buzz of Weibo, and then the discovery of hotspots can be reasonably made. The experimental results show that the incremental clustering algorithm presented in this paper can effectively improve the accuracy of clustering in different dimensions. Meanwhile, the calculation formula of Weibo buzz reasonably describes the evolution process of Weibo buzz from a qualitative point of view, which can help discover the hotspots effectively. References | Related Articles | Metrics

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Dynamic Measurement of Task Scheduling Algorithm in Multi-Processor System XIE Ying *(谢盈), WU Jinzhao (吴尽昭), CHEN Jianying (陈建英), CUI Mengtian (崔梦天) 2019, 24 (3):  372-380.  doi: 10.1007/s12204-019-2073-7 Abstract ( 425 )   PDF (286KB) ( 103 )   It is important to evaluate function behaviors and performance features of task scheduling algorithm in the multi-processor system. A novel dynamic measurement method (DMM) was proposed to measure the task scheduling algorithm’s correctness and dependability. In a multi-processor system, task scheduling problem is represented by a combinatorial evaluation model, interactive Markov chain (IMC), and solution space of the algorithm with time and probability metrics is described by action-based continuous stochastic logic (aCSL). DMM derives a path by logging runtime scheduling actions and corresponding times. Through judging whether the derived path can be received by task scheduling IMC model, DMM analyses the correctness of algorithm. Through judging whether the actual values satisfy label function of the initial state, DMM analyses the dependability of algorithm. The simulation shows that DMM can effectively characterize the function behaviors and performance features of task scheduling algorithm. References | Related Articles | Metrics

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Energy Separation and Explicit Dynamic Analysis of Low Temperature Impact Toughness of Transmission Tower Material Q420B YU Xingxue (余兴学), ZHANG Yinghua (张映华), ZHANG Xiaomin (张晓敏), JIANG Yu* (蒋渝) 2019, 24 (3):  381-387.  doi: 10.1007/s12204-018-1963-4 Abstract ( 444 )   PDF (12243KB) ( 111 )   To determine the physical significance of the impact toughness parameters and accurately characterize the low temperature impact toughness of transmission tower material Q420B, the finite element model of Charpy impact test is established on the basis of experiment. The simulation and test results are verified, and the specimen fracture is analyzed by scanning electron microscope. The formation and growth mechanism of the crack are dynamically analyzed. On this basis, energy separation method is used to investigate the effect of low temperature on impact toughness. The results show that the simulation and test results are in good agreement, and the ductile-brittle transition temperature of Q420B is about ?50 ?C. The breaking process of the specimen is divided into the crack formation and propagation. When temperature drops from 20 to ?60 ?C, the crack propagation energy decreases from 51.0 to 11.9 J, the crack formation energy reduces from 39.9 to 15.8 J, and the fracture time of the material drops from 1.8 to 0.6ms. References | Related Articles | Metrics

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Comparative Study on Cutting Performance of Chaser and Triangle-Shaped Inserts in Inconel 718 Turning LEI Xuelin *(雷学林), SHI Yukai (史玉凯), HE Yun (何云) 2019, 24 (3):  388-394.  doi: 10.1007/s12204-019-2074-6 Abstract ( 352 )   PDF (4372KB) ( 109 )   The effect of cutting teeth number on the cutting force, surface roughness, tool wear rate and the cutting chip shape characteristics is systematically evaluated. A novel five teeth chaser insert (C tool) which could turn the workpiece at five cutting points simultaneously is involved in comparison with the standard triangle shaped insert (T tool), in the purpose of solving the problems of cutting heat concentration and rapid tool failures in the Inconel 718 machining process. Comparative orthogonal cutting experiments of the C tool and T tool show that the cutting depth is the significant influencing factor of the cutting forces. Meanwhile, the five cutting teeth of the C tool show the effectiveness of dispersing the cutting forces as well as improving the cutting efficiency. The feed rate is the significant factor to affect the root-mean-square surface roughness (Ra) of workpiece machined by the T tool, while the significant influencing variable of Ra for the C tool is the cutting depth due to its unique tool geometry (0 ?rake angle) in the axial feeding process. Moreover, due to the dispersing effect, the cutting edges on the C tool exhibits lower tool wear rate than that of the T tool under the same axial feed. The chips are regular continuous long chips for the T tool, while the irregular continuous chips with the characteristic of saw-toothed profile are obtained due to its unique 0?rake angle. The C tool shows the valid potential for effectively dispersing the cutting heat and slowing down the tool wear rate in the Inconel 718 machining process. References | Related Articles | Metrics

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Effect of Deposition Time on Thickness and Corrosion Behavior of Zn-Fe Coating LIU Li (刘丽), YU Sirong* (于思荣) 2019, 24 (3):  395-401.  doi: 10.1007/s12204-019-2075-5 Abstract ( 414 )   PDF (8564KB) ( 113 )   Zn-Fe coatings on Q235 steel are prepared by pack cementation process at 390 ?C for 2, 4, 6, 8 and 10 h to investigate the effects of the deposition time on the thickness and corrosion behavior of the Zn-Fe coatings. The thickness of the coating increases with the increase of the deposition time. The coating is composed of a thick outer layer and a thin inner layer. The formation of the coating depends on the inward diffusion of Zn atoms and the outward diffusion of Fe atoms. The outer layer is composed of Fe11Zn40 and FeZn10 phases. The corrosion behavior of the Zn-Fe coatings is evaluated by immersion test and polarization test. The results show that the Zn-Fe coatings can effectively prevent the Q235 steel from corrosion. The corrosion resistance of the coating is proportional to the deposition time. References | Related Articles | Metrics

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Parametric Geometric Model and Shape Optimization of Airfoils of a Biomimetic Manta Ray Underwater Vehicle LUO Yang (罗扬), PAN Guang* (潘光), HUANG Qiaogao (黄桥高), SHI Yao (施瑶), LAI Hui (赖慧) 2019, 24 (3):  402-408.  doi: 10.1007/s12204-019-2076-4 Abstract ( 523 )   PDF (1372KB) ( 120 )   As a new kind of autonomous underwater vehicle, bionic submersible has many merits such as high efficiency and low costs. In order to obtain such advantages, it is a good way to simulate the shapes of marine animals and apply them to the design of artificial underwater vehicle. In this paper, an optimization system of airfoils is proposed by the improved class-shape-transformation (CST) parameterization method and genetic algorithm (GA). The appearance of a manta-ray-inspired underwater vehicle is rebuilt using the optimal sectional airfoils obtained by the proposed optimization system. Computational simulations are carried out to investigate the hydrodynamic performance of the submersible using the commercial computational fluid dynamics (CFD) code Fluent. The results demonstrate that the maximum thickness of the vehicle increases by 9%, which means the loading capacity is increased. Moreover, the underwater vehicle shows better hydrodynamic performance, and the lift-drag ratio of initial design is increased by more than 10% using the presented optimization system of airfoils. References | Related Articles | Metrics