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Review of Key Technologies for Developing Personalized Lower Limb Rehabilitative Exoskeleton Robots TAO Jing, (陶璟), ZHOU Zhenhuan (周振欢) J Shanghai Jiaotong Univ Sci    2024, 29 (1): 16-28.   DOI: 10.1007/s12204-022-2452-3 Abstract （266）      PDF（pc） （1179KB）（342）       Knowledge map    Save Rehabilitative training and assistance to daily living activities play critical roles in improving the life quality of lower limb dyskinesia patients and older people with motor function degeneration. Lower limb rehabilitative exoskeleton has a promising application prospect in support of the above population. In this paper, critical technologies for developing lower limb rehabilitative exoskeleton for individualized user needs are identi- fied and reviewed, including exoskeleton hardware modularization, bionic compliant driving, individualized gait planning and individual-oriented motion intention recognition. Inspired by the idea of servitization, potentials in exoskeleton product-service system design and its enabling technologies are then discussed. It is suggested that future research will focus on exoskeleton technology and exoskeleton-based service development oriented to an individual’s physical features and personalized requirements to realize better human-exoskeleton coordination in terms of technology, as well as accessible and high-quality rehabilitation and living assistance in terms of utility. Reference | Related Articles | Metrics | Comments（0）

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Medicine-Engineering Interdisciplinary Research Based on Bibliometric Analysis: A Case Study on Medicine-Engineering Institutional Cooperation of Shanghai Jiao Tong University WANG Qingwen (王庆稳)，CUI Tingting (崔婷婷)，DENG Peiwen* (邓珮雯) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 841-856.   DOI: 10.1007/s12204-022-2418-5 Abstract （81）      PDF（pc） （1829KB）（169）       Knowledge map    Save This article aims to provide reference for medicine-engineering interdisciplinary research. Targeted at the scientific literature and patent literature published by Shanghai Jiao Tong University, this article attempts to set up co-occurrence matrix of medicine-engineering institutional information which was extracted from address fields of the papers, so as to construct the medicine-engineering intersection datasets. The dataset of scientific literature was analyzed using bibliometrics and visualization methods from multiple dimensions, and the most active factors, such as trends of output, journal and subject distribution, were identified from the indicators of category normalized citation impact (CNCI), times cited, keywords, citation topics and the degree of medicineengineering interdisplinary. Research on hotspots and trends was discussed in detail. Analyses of the dataset of patent literature showed research themes and measured the degree for technology convergence of medicineengineering. Reference | Related Articles | Metrics | Comments（0）

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Review of Power-Assisted Lower Limb Exoskeleton Robot HE Guisong (贺贵松), HUANG Xuegong (黄学功), LI Feng (李峰), WANG Huixing (汪辉兴) J Shanghai Jiaotong Univ Sci    2024, 29 (1): 1-15.   DOI: 10.1007/s12204-022-2489-3 Abstract （436）      PDF（pc） （1195KB）（136）       Knowledge map    Save Power-assisted lower limb exoskeleton robot is a wearable intelligent robot system involving mechanics,materials, electronics, control, robotics, and many other fields. The system can use external energy to provide additional power to humans, enhance the function of the human body, and help the wearer to bear weight that is previously unbearable. At the same time, employing reasonable structure design and passive energy storage can also assist in specific actions. First, this paper introduces the research status of power-assisted lower limb exoskeleton robots at home and abroad, and analyzes several typical prototypes in detail. Then, the key technologies such as structure design, driving mode, sensing technology, control method, energy management, and human-machine coupling are summarized, and some common design methods of the exoskeleton robot are summarized and compared. Finally, the existing problems and possible solutions in the research of power-assisted lower limb exoskeleton robots are summarized, and the prospect of future development trend has been analyzed. Reference | Related Articles | Metrics | Comments（0）

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Entity Relationship Explanation via Conceptualization XIE Chenhao(谢晨昊), LIANG Jiaqing(梁家卿), XIA Yanghua(肖仰华), HWANG Seung-won J Shanghai Jiaotong Univ Sci    2023, 28 (6): 695-702.   DOI: 10.1007/s12204-021-2394-1 Abstract （180）      PDF（pc） （608KB）（109）       Knowledge map    Save Finding an attribute to explain the relationships between a given pair of entities is valuable in many applications. However, many direct solutions fail, owing to its low precision caused by heavy dependence on text and low recall by evidence scarcity. Thus, we propose a generalization-and-inference framework and implement it to build a system: entity-relationship finder (ERF). Our main idea is conceptualizing entity pairs into proper concept pairs, as intermediate random variables to form the explanation. Although entity conceptualization has been studied, it has new challenges of collective optimization for multiple relationship instances, joint optimization for both entities, and aggregation of diluted observations into the head concepts defining the relationship. We propose conceptualization solutions and validate them as well as the framework with extensive experiments. Reference | Related Articles | Metrics | Comments（0）

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Multi-Robot Task Allocation Using Multimodal Multi-Objective Evolutionary Algorithm Based on Deep Reinforcement Learning MIAO Zhenhua(苗镇华), HUANG Wentao(黄文焘), ZHANG Yilian(张依恋), FAN Qinqin(范勤勤) J Shanghai Jiaotong Univ Sci    2024, 29 (3): 377-387.   DOI: 10.1007/s12204-023-2679-7 Abstract （134）      PDF（pc） （975KB）（106）       Knowledge map    Save The overall performance of multi-robot collaborative systems is significantly affected by the multirobot task allocation. To improve the effectiveness, robustness, and safety of multi-robot collaborative systems,a multimodal multi-objective evolutionary algorithm based on deep reinforcement learning is proposed in this paper. The improved multimodal multi-objective evolutionary algorithm is used to solve multi-robot task allocation problems. Moreover, a deep reinforcement learning strategy is used in the last generation to provide a high-quality path for each assigned robot via an end-to-end manner. Comparisons with three popular multimodal multi-objective evolutionary algorithms on three different scenarios of multi-robot task allocation problems are carried out to verify the performance of the proposed algorithm. The experimental test results show that the proposed algorithm can generate sufficient equivalent schemes to improve the availability and robustness of multirobot collaborative systems in uncertain environments, and also produce the best scheme to improve the overall task execution efficiency of multi-robot collaborative systems. Reference | Related Articles | Metrics | Comments（0）

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Lateral Force Characteristics of Cartridge Valve Core HAN Heyong1(韩贺永),ZHANG Jianru1(张建茹), PAN Siji1(潘思意)，LI Yugui2*(李玉贵)，MA Lifeng1(马立峰),LIU Shirui3(刘实睿) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 604-610.   DOI: 10.1007/s12204-021-2402-5 Abstract （62）      PDF（pc） （978KB）（103）       Knowledge map    Save he valve core is readily subjected to a large lateral force which affects the dynamic response speed. Here, a new type of cartridge valve core structure is proposed to solve this problem. The numerical simulation method is applied to analyze the flow characteristics of clearance flow field on velocity distribution, pressure distribution, valve core motion speed, and leakage. The results using computational fluid dynamics (CFD) show that the guide groove is set on the surface of the cartridge valve core, increasing the connecting length of the valve core, forming a uniform radial pressure distribution and velocity distribution, effectively reducing the lateral force, and at the same time ensuring that the leak is not too big. These findings provide theoretical guidance and a basis for optimizing cartridge valve to reduce the occurrence of jamming and improve the response frequency. Reference | Related Articles | Metrics | Comments（0）

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Calibration Technology of Optical Fiber Strain Sensor CHEN Gang(陈刚), LIU Hongyue(刘宏月), GAO Ruiriang(高瑞翔) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 551-559.   DOI: 10.1007/s12204-022-2406-9 Abstract （216）      PDF（pc） （1122KB）（99）       Knowledge map    Save As one of the hotspots of sensing technology at present, optical fiber sensor has the characteristics of small size, anti-electromagnetic interference, and easy networking, which plays an irreplaceable role in multiphysics parameter monitoring of complex electromagnetic environments. The precise calibration of the optical fiber strain sensor has great practical value in prolonging the survival rate of the sensor, improving the measurement accuracy, and meeting the needs of long-term monitoring. By reviewing the research status of strain sensor calibration method and fiber optic strain sensor calibration method, the advantages and disadvantages of the main methods are analyzed separately from the static and dynamic perspectives, and the development prospect of the calibration technology of optic fiber strain sensor is summarized. Reference | Related Articles | Metrics | Comments（0）

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Fault Diagnosis for Rolling Element Bearing in Dataset Bias Scenario HOU Liangsheng(侯良生),ZHANG Jundong*(张均东) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 638-651.   DOI: 10.1007/s12204-021-2320-6 Abstract （47）      PDF（pc） （1575KB）（96）       Knowledge map    Save Recently, data-driven methods, especially deep learning, outperform other methods for rolling element bearing (REB) fault diagnosis. Nevertheless, most research work assumes that REB dataset is unbiased. In the real industry applications, the dataset bias exists with REB owing to varying REB working conditions and noise interference. Recently proposed adversarial discriminative domain adaptation (ADDA) is an increasingly popular incarnation to solve dataset bias problem. However, it mainly devotes to realizing domain alignments, and ignores class-level alignments; it can cause degradation of classification performance. In this study, we propose a new REB fault diagnosis model based on improved ADDA to address dataset bias. The proposed diagnosis model realizes domain- and class-level alignments in dataset bias scenario; it consists of two feature extractors, a domain discriminator, and two label classifiers. The feature extractors and domain discriminator are trained in an adversarial manner to minimize the domain difference in feature extractors. The domain discrepancy in label classifier is reduced by minimizing correlation alignment (CORAL) loss. We evaluate the proposed model on the Case Western Reserve University (CWRU) bearing dataset and Paderborn University bearing dataset. The proposed method yields better results than other methods and has good prospects for industrial applications. Reference | Related Articles | Metrics | Comments（0）

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Boosting Unsupervised Domain Adaptation with Soft Pseudo-Label and Curriculum Learning ZHANG Shengjia(张晟嘉), LIN Tiancheng(林天成), XU Yi(徐奕) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 703-716.   DOI: 10.1007/s12204-022-2487-5 Abstract （145）      PDF（pc） （963KB）（83）       Knowledge map    Save By leveraging data from a fully labeled source domain, unsupervised domain adaptation (UDA) improves classification performance on an unlabeled target domain through explicit discrepancy minimization of data distribution or adversarial learning. As an enhancement, category alignment is involved during adaptation to reinforce target feature discrimination by utilizing model prediction. However, there remain unexplored problems about pseudo-label inaccuracy incurred by wrong category predictions on target domain, and distribution deviation caused by overfitting on source domain. In this paper, we propose a model-agnostic two-stage learning framework, which greatly reduces flawed model predictions using soft pseudo-label strategy and avoids overfitting on source domain with a curriculum learning strategy. Theoretically, it successfully decreases the combined risk in the upper bound of expected error on the target domain. In the first stage, we train a model with distribution alignment-based UDA method to obtain soft semantic label on target domain with rather high confidence. To avoid overfitting on source domain, in the second stage, we propose a curriculum learning strategy to adaptively control the weighting between losses from the two domains so that the focus of the training stage is gradually shifted from source distribution to target distribution with prediction confidence boosted on the target domain. Extensive experiments on two well-known benchmark datasets validate the universal effectiveness of our proposed framework on promoting the performance of the top-ranked UDA algorithms and demonstrate its consistent superior performance. Reference | Related Articles | Metrics | Comments（0）

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High Curvature Stripe Profile Extraction Algorithm of Line Structured Light Measuring System SUN Hao (孙昊), DU Xuan (杜宣), LÜ Na(吕娜), CUI Bin(崔斌), ZHA Hui(赵辉) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 560-568.   DOI: 10.1007/s12204-022-2476-8 Abstract （118）      PDF（pc） （1375KB）（80）       Knowledge map    Save In the line structured light measuring system, the accuracy of the process of laser stripe directly affects the measurement results. Therefore, the extraction algorithm for the laser stripe, especially the surface with high reflection and high curvature, is very important. The imaging principle of line structured light, the light intensity distribution law of laser stripe and the extraction algorithm have been studied, and a stripe profile extraction method based on real light intensity distribution has been proposed. In this algorithm, fast region of interest extraction, stripe width estimation, and adaptive filtering on the striped image are performed. Then the energy center of the stripe at the sub-pixel level is extracted. Finally, the low-quality center points are eliminated, and the context information is used to recover the missing central points. Simulated images generated based on the imaging principle of line structured light and real experimental images were used to evaluate the accuracy and repeatability of the proposed method. The results show that the method behaves excellently at the edges of high-curvature stripes; the maximum error is only 1.6 pixels, which is 1/10 of the classic Steger algorithm; the experiment repeatability is only 8.8 μm, which is 2.7 times that of the Steger method. Therefore, the proposed method improves the accuracy of object contour extraction, and it is especially suitable for contour detection of objects with high curvature. Reference | Related Articles | Metrics | Comments（0）

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Review on Anti-Frost Technology Based on Microchannel Heat Exchanger YE Zhenhong(叶振鸿), WANG Wei(王炜), LI Xinhua(李新华), CHEN Jiangping(陈江平) J Shanghai Jiaotong Univ Sci    2024, 29 (2): 161-178.   DOI: 10.1007/s12204-022-2539-x Abstract （124）      PDF（pc） （4397KB）（80）       Knowledge map    Save Frosting is an inevitable adverse phenomenon in many fields such as industrial refrigeration, cryogenics, and heat pump air conditioning, which may influence the efficiency of the equipment and increase the energy consumption of the system. The complicated louvered-fin structure and fluid-channels arrangements of the microchannel heat exchanger (HEX) will affect the heat transfer performance and frosting characteristics. First, this article analyzes different factors such as refrigerant distribution, refrigerant flow pattern, and HEX surface temperature distribution. Further, combined with the features of the microchannel HEX, the existing anti-frosting technologies and various methods of surface treatment for anti-frosting are summarized. The review focuses on the preparation of superhydrophobic surfaces and their superior properties. Furthermore, the internal mechanism is analyzed in conjunction with the relevant research of our group. Superhydrophobic character has excellent anti-frosting performance and heat transfer performance, which is of great significance for improving energy-saving and system performance. Finally, the future development of superhydrophobic surface technology is analyzed and prospected. Reference | Related Articles | Metrics | Comments（0）

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CFD-Aided Investigation of Combined Flow Conditioners for Gas Ultrasonic Flow Meter YUAN Yaqi1(袁亚琦)，LI Shiyangl*(李世阳)，ZHENG Jia1(郑佳),LI Mingrui2(李明睿) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 611-620.   DOI: 10.1007/s12204-021-2378-1 Abstract （56）      PDF（pc） （3397KB）（76）       Knowledge map    Save Stable and fully developed gas flow field is crucial for realizing accurate measurement of gas ultrasonic flow meter. To reduce the flow field distortion, a flow conditioner is usually used. However, the traditional monotype flow conditioner can only improve the flow field distribution partly. The measurement accuracy of the transit time ultrasonic flow meter is still affected because of its serious flow field distortion in the complex pipeline conditions. In this paper, to further improve the flow field distribution, a combined conditioner is investigated. The combined flow conditioner is composed of fan-shaped section, turbulent mixing cavity, and honeycomb-shaped section. The effects of fan blade angle and cavity length on the flow field of the DN50 flow meter are studied using computational fluid dynamics (CFD) simulation. Simulation results indicate that compared with the monotype conditioner, the combined conditioner has better performance on effectively reducing the swirl and turbulence and providing more stable and repetitive velocity profiles. Experiments also validate the effectiveness of the combined conditioner. The flow meter with the combined conditioner has better repeatability of less than 0.2%, which is better than those of the monotype conditioners under the same conditions. This work is very useful for accurate measurement of gas ultrasonic flow meter, especially for the complex pipeline conditions. Reference | Related Articles | Metrics | Comments（0）

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Transfer Learning in Motor Imagery Brain Computer Interface: A Review LI Mingai1,2,3∗ (李明爱), XU Dongqin1 (许东芹) J Shanghai Jiaotong Univ Sci    2024, 29 (1): 37-59.   DOI: 10.1007/s12204-022-2488-4 Abstract （142）      PDF（pc） （1734KB）（75）       Knowledge map    Save Transfer learning, as a new machine learning methodology, may solve problems in related but different domains by using existing knowledge, and it is often applied to transfer training data from another domain for model training in the case of insufficient training data. In recent years, an increasing number of researchers who engage in brain-computer interface (BCI), have focused on using transfer learning to make most of the available electroencephalogram data from different subjects, effectively reducing the cost of expensive data acquisition and labeling as well as greatly improving the learning performance of the model. This paper surveys the development of transfer learning and reviews the transfer learning approaches in BCI. In addition, according to the “what to transfer” question in transfer learning, this review is organized into three contexts: instance-based transfer learning, parameter-based transfer learning, and feature-based transfer learning. Furthermore, the current transfer learning applications in BCI research are summarized in terms of the transfer learning methods, datasets, evaluation performance, etc. At the end of the paper, the questions to be solved in future research are put forward, laying the foundation for the popularization and in-depth research of transfer learning in BCI. Reference | Related Articles | Metrics | Comments（0）

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Parameter Optimization and Precision Enhancement of Dual-Coil Eddy Current Sensor ZHANG Zhenning1(张振宁)，LIU Qiang2(刘强), Lü Chunfeng3(吕春峰)，MAO Yimeil(毛义梅)，TAo Weil(陶卫),ZHAO Huil*(赵辉) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 596-603.   DOI: 10.1007/s12204-022-2511-9 Abstract （129）      PDF（pc） （948KB）（67）       Knowledge map    Save To enhance the measurement precision of eddy current sensor in particular environments such as extreme temperature changes and limited available space in aerospace, we optimized the structural parameters of the traditional dual-coil eddy current sensor probe by electromagnetic field analysis and finite element simulation modeling, and further presented the criteria for determining the optimal coil distance of the dual-coil probe. The simulation results are verified by setting up an experimental platform. For the extreme temperature environment, the displacement measurement error caused by the full range temperature variation of the dual-coil sensor under the optimal distance is less than 21.0% of that of the single-coil sensor. On this basis, we analyzed and verified the thermal stability of the structurally optimized dual-coil eddy current sensor. After temperature compensation, the displacement measurement accuracy can reach 14.9 times more accurate than that of the single-coil sensor. The method proposed in this paper can provide a design reference for the structural optimization of the axial dual-coil eddy current sensor probe. Reference | Related Articles | Metrics | Comments（0）

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Arc and Droplet Behaviors in Horizontal Short-Arc Pulsed Gas Metal Arc Welding of 9%Ni Steel with ERNiCrMo-3 Welding Wire LIU Yiwei1 (刘轶玮), HUA Xueming1* (华学明), WU Dongsheng1 (吴东升), LI Fang1 (李芳), CAI Yan1 (蔡艳), WANG Huan2 (王欢), YANG Xiurong3 (杨修荣) J Shanghai Jiaotong Univ Sci    2024, 29 (2): 361-376.   DOI: 10.1007/s12204-022-2548-9 Abstract （35）      PDF（pc） （5299KB）（57）       Knowledge map    Save Short-arc pulsed gas metal arc welding (P-GMAW) was used to solve the difficulties of molten pool spreading and droplet transfer of Ni-based welding wire. Suppression of short-circuit current was used to reduce spatter. Arc length stabilizer was used to acquire a proper and stable arc length maintained at the critical position where short circuit starts to occur. Short-arc P-GMAW with or without arc length stabilizer was compared. The droplet transfer, arc behaviors and weld bead profiles were investigated and compared based on the high-speed photography and observation of weld cross-section. When the arc length stabilizer was deactivated, the arc length was unstable and too short. The droplet transfer mode was mainly short circuit partial transfer, with only a small part of the droplet transferred into the molten pool, with the characteristics of no obvious necking, a few spatters, small droplet impact, long short circuit duration and high short-circuit current. There was also a small proportion of short circuit complete transfer with obvious necking, larger droplet impact, shorter short-circuit duration and lower short-circuit current. With arc length stabilizer, droplet transfer modes were short circuit complete transfer and spray transfer. The spray transfer had the largest droplet impact, no short circuit and no spatter. With the arc length stabilizer activated, a deep penetration, a high penetration ratio, a small reinforcement and a large reinforcement factor were acquired. This provides an innovative method to solve the difficulties of droplet transfer and molten pool spreading and eliminate the incomplete fusion in the GMAW of 9%Ni steel with nickel-based alloy welding wire. Reference | Related Articles | Metrics | Comments（0）

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High Curvature Stripe Profile Extraction Algorithm of Line Structured Light Measuring System CHEN Qiheng1(陈启恒),PENG Na2(彭娜)，Lü Na1(吕娜)，TAO Wei(陶卫)，ZHAO Huil*(赵辉) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 577-586.   DOI: 10.1007/s12204-022-2414-9 Abstract （101）      PDF（pc） （1586KB）（49）       Knowledge map    Save Non-uniformity of light sources is one of the inevitable error factors causing poor shape recovery accuracy of photometric stereo methods under close-range lighting with quasi point lights. Semi-calibrated photometric stereo methods are required to avoid repeated, tedious and impractical photometric calibration. In this paper, two simple, concise but effective mesh-based semi-calibrated photometric stereo methods are proposed. The proposed methods extend the traditional mesh-based photometric stereo methods and further allow joint and accurate estimation of normals and non-uniform light intensities by alternatively updating normals, depth maps and intensities. Extensive experiments are conducted to validate the effectiveness and robustness of the proposed algorithms. Even under extremely severe non-uniform lighting, the proposed methods can still suppress the error and improve the shape recovery accuracy by up to 65.6% in real-world experiments. Reference | Related Articles | Metrics | Comments（0）

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Multiple Detection Model Fusion Framework for Printed Circuit Board Defect Detection WU Xingl(武星), ZHANG Qingfeng(张庆丰), WANG Jianjia(王健嘉), YAO Junfeng(姚骏峰), Guo Yike.(郭毅可) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 717-727.   DOI: 10.1007/s12204-022-2471-0 Abstract （84）      PDF（pc） （1870KB）（49）       Knowledge map    Save The printed circuit board (PCB) is an indispensable component of electronic products, which determines the quality of these products. With the development and advancement of manufacturing technology, the layout and structure of PCB are getting complicated. However, there are few effective and accurate PCB defect detection methods. There are high requirements for the accuracy of PCB defect detection in the actual production environment, so we propose two PCB defect detection frameworks with multiple model fusion including the defect detection by multi-model voting method (DDMV) and the defect detection by multi-model learning method (DDML). With the purpose of reducing wrong and missing detection, the DDMV and DDML integrate multiple defect detection networks with different fusion strategies. The effectiveness and accuracy of the proposed framework are verified with extensive experiments on two open-source PCB datasets. The experimental results demonstrate that the proposed DDMV and DDML are better than any other individual state-of-the-art PCB defect detection model in F1-score, and the area under curve value of DDML is also higher than that of any other individual detection model. Furthermore, compared with DDMV, the DDML with an automatic machine learning method achieves the best performance in PCB defect detection, and the F1-score on the two datasets can reach 99.7% and 95.6% respectively. Reference | Related Articles | Metrics | Comments（0）

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Performance and Optimization of Air Source Heat Pump Water Heater with Cyclic Heating LI Fan(李凡), LU Gaofeng(陆高锋), DING Yunxiao(丁云霄), ZHENG Chunyuan(郑春元), LI Bin(李斌), ZHAI Xiaoqiang(翟晓强) J Shanghai Jiaotong Univ Sci    2024, 29 (2): 179-187.   DOI: 10.1007/s12204-022-2500-z Abstract （81）      PDF（pc） （1349KB）（47）       Knowledge map    Save A new type of microchannel condenser applied in the air source heat pump water heater (ASHPWH) with cyclic heating was proposed in this study. The operating performance of the ASHPWH was first tested. Then,the structure of the microchannel condenser was optimized with the implement of vortex generators. Finally, a numerical model of the ASHPWH was established and the optimized microchannel condenser was studied. The experimental results showed that the average coefficient of performance (COP) of the 1 HP (735 W) ASHPWH reached 3.48. In addition, the optimized microchannel condenser could be matched with a 3 HP (2 430 W) ASHPWH with an average heating capacity of 10.30 kW, and achieving an average COP of 4.24, 14.6% higher than the limit value in the national standard. Reference | Related Articles | Metrics | Comments（0）

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Time-Resolved Imaging in Short-Wave Infrared Region XU Yang (徐杨), LI Wanwan∗ (李万万) J Shanghai Jiaotong Univ Sci    2024, 29 (1): 29-36.   DOI: 10.1007/s12204-022-2547-x Abstract （101）      PDF（pc） （810KB）（44）       Knowledge map    Save Compared with the conventional first near-infrared (NIR-I, 700—900 nm) window, the short-wave infrared region (SWIR, 900—1 700 nm) possesses the merits of the increasing tissue penetration depths and the suppression of scattering background, leading to great potential for in vivo imaging. Based on the limitations of the common spectral domain, and the superiority of the time-dimension, time-resolved imaging eliminates the auto-fluorescence in the biological tissue, thus supporting higher signal-to-noise ratio and sensitivities. The imaging technique is not affected by the difference in tissue composition or thickness and has the practical value of quantitative in vivo detection. Almost all the relevant time-resolved imaging was carried out around lanthanide-doped upconversion nanomaterials, owing to the advantages of ultralong luminescence lifetime, excellent photostability, controllable morphology, easy surface modification and various strategies of regulating lifetime. Therefore, this review presents the research progress of SWIR time-resolved imaging technology based on nanomaterials doped with lanthanide ions as luminescence centers in recent years. Reference | Related Articles | Metrics | Comments（0）

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Unsupervised Oral Endoscope Image Stitching Algorithm HUANG Rong (黄荣), CHANG Qing∗ (常青), ZHANG Yang （张扬） J Shanghai Jiaotong Univ Sci    2024, 29 (1): 81-90.   DOI: 10.1007/s12204-022-2513-7 Abstract （69）      PDF（pc） （5774KB）（42）       Knowledge map    Save Oral endoscope image stitching algorithm is studied to obtain wide-field oral images through registration and stitching, which is of great significance for auxiliary diagnosis. Compared with natural images, oral images have lower textures and fewer features. However, traditional feature-based image stitching methods rely heavily on feature extraction quality, often showing an unsatisfactory performance when stitching images with few features. Moreover, due to the hand-held shooting, there are large depth and perspective disparities between the captured images, which also pose a challenge to image stitching. To overcome the above problems, we propose an unsupervised oral endoscope image stitching algorithm based on the extraction of overlapping regions and the loss of deep features. In the registration stage, we extract the overlapping region of the input images by sketching polygon intersection for feature points screening and estimate homography from coarse to fine on a three-layer feature pyramid structure. Moreover, we calculate loss using deep features instead of pixel values to emphasize the importance of depth disparities in homography estimation. Finally, we reconstruct the stitched images from feature to pixel, which can eliminate artifacts caused by large parallax. Our method is compared with both feature-based and previous deep-based methods on the UDIS-D dataset and our oral endoscopy image dataset. The experimental results show that our algorithm can achieve higher homography estimation accuracy, and better visual quality, and can be effectively applied to oral endoscope image stitching. Reference | Related Articles | Metrics | Comments（0）

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Cross-Modal Entity Resolution for Image and Text Integrating Global and Fine-Grained Joint Attention Mechanism ZENG Zhirian(曾志贤),CAO Jianjun*(曹建军),WENG Nianfeng(翁年凤)，YUAN Zhen(袁震)，YU Xu(余旭) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 728-737.   DOI: 10.1007/s12204-022-2465-y Abstract （82）      PDF（pc） （1951KB）（41）       Knowledge map    Save In order to solve the problem that the existing cross-modal entity resolution methods easily ignore the high-level semantic informational correlations between cross-modal data, we propose a novel cross-modal entity resolution for image and text integrating global and fine-grained joint attention mechanism method. First, we map the cross-modal data to a common embedding space utilizing a feature extraction network. Then, we integrate global joint attention mechanism and fine-grained joint attention mechanism, making the model have the ability to learn the global semantic characteristics and the local fine-grained semantic characteristics of the cross-modal data, which is used to fully exploit the cross-modal semantic correlation and boost the performance of cross-modal entity resolution. Moreover, experiments on Flickr-30K and MS-COCO datasets show that the overall performance of R@sum outperforms by 4.30% and 4.54% compared with 5 state-of-the-art methods, respectively, which can fully demonstrate the superiority of our proposed method. Reference | Related Articles | Metrics | Comments（0）

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Online Multi-Object Tracking Under Moving Unmanned Aerial Vehicle Platform Based on Object Detection and Feature Extraction Network LIU Zengmin (刘增敏), WANG Shentao(王申涛), YAO Lixiu(姚莉秀), CAI Yunze(蔡云泽) J Shanghai Jiaotong Univ Sci    2024, 29 (3): 388-399.   DOI: 10.1007/s12204-022-2540-4 Abstract （56）      PDF（pc） （1105KB）（39）       Knowledge map    Save In order to solve the problem of small object size and low detection accuracy under the unmanned aerial vehicle (UAV) platform, the object detection algorithm based on deep aggregation network and high-resolution fusion module is studied. Furthermore, a joint network of object detection and feature extraction is studied to construct a real-time multi-object tracking algorithm. For the problem of object association failure caused by UAV movement, image registration is applied to multi-object tracking and a camera motion discrimination model is proposed to improve the speed of the multi-object tracking algorithm. The simulation results show that the algorithm proposed in this study can improve the accuracy of multi-object tracking under the UAV platform, and effectively solve the problem of association failure caused by UAV movement. Reference | Related Articles | Metrics | Comments（0）

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Spectrum-Sensing Method for Arc Fault Detection in Direct Current System with Lithium Batteries HAN Zhengqian1(韩正谦)，LUO Liwenl*(罗利文)，YAo Wei2(姚伟)，YIN Shaowen2(尹邵文)，CHEN Wei2(陈伟),WANG Yinghui2(王营辉) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 630-637.   DOI: 10.1007/s12204-022-2482-x Abstract （81）      PDF（pc） （1296KB）（38）       Knowledge map    Save We mainly study the detection of arc faults in the direct current (DC) system of lithium battery energy storage power station. Lithium battery DC systems are widely used, but traditional DC protection devices are unable to achieve adequate protection of equipment and circuits. We build an experimental platform based on an energy storage power station with lithium batteries. Then, the data collection of normal current and arc-fault current is completed under multiple conditions, and the waveforms of obvious and weak signals as the arc occurs are presented. We analyze the principles and application range of several common spectrum-sensing methods and study the feasibility of applying them to the arc detection field. Finally, the covariance absolute value detection algorithm is selected, and the average value of the current is filtered out to make the algorithm adapt to the arc detection field. The result shows that the detection probability in 500 sets of experimental data has reached 98% Reference | Related Articles | Metrics | Comments（0）

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Medical Image Encryption Based on Josephus Traversing and Hyperchaotic Lorenz System YANG Na (杨娜), ZHANG Shuxia (张淑霞), BAI Mudan (白牡丹), LI Shanshan∗ (李珊珊) J Shanghai Jiaotong Univ Sci    2024, 29 (1): 91-108.   DOI: 10.1007/s12204-022-2555-x Abstract （49）      PDF（pc） （8082KB）（37）       Knowledge map    Save This study proposes a new medical image encryption scheme based on Josephus traversing and hyperchaotic Lorenz system. First, a chaotic sequence is generated through hyperchaotic system. This hyperchaotic sequence is used in the scrambling and diffusion stages of the algorithm. Second, in the scrambling process, the image is initially confused by Josephus scrambling, and then the image is further confused by Arnold map. Finally, generated hyperchaos sequence and exclusive OR operation is used for the image to carry on the positive and reverse diffusion to change the pixel value of the image and further hide the effective information of the image. In addition, the information of the plaintext image is used to generate keys used in the algorithm, which increases the ability of resisting plaintext attack. Experimental results and security analysis show that the scheme can effectively hide plaintext image information according to the characteristics of medical images, and is resistant to common types of attacks. In addition, this scheme performs well in the experiments of robustness, which shows that the scheme can solve the problem of image damage in telemedicine. It has a positive significance for the future research. Reference | Related Articles | Metrics | Comments（0）

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A Novel Cable-Driven Soft Robot for Surgery LI Ru1 (李茹), CHEN Fang2 (陈方), YU Wenwei3 (俞文伟), IGARASH Tatsuo3,4, SHU Xiongpeng1 (舒雄鹏), XIE Le1,5,6∗ (谢叻) J Shanghai Jiaotong Univ Sci    2024, 29 (1): 60-72.   DOI: 10.1007/s12204-022-2497-3 Abstract （80）      PDF（pc） （2939KB）（36）       Knowledge map    Save Robot-assisted laparoscopic radical prostatectomy (RARP) is widely used to treat prostate cancer. The rigid instruments primarily used in RARP cannot overcome the problem of blind areas in surgery and lead to more trauma such as more incision for the passage of the instrument and additional tissue damage caused by rigid instruments. Soft robots are relatively flexible and theoretically have infinite degrees of freedom which can overcome the problem of the rigid instrument. A soft robot system for single-port transvesical robot-assisted radical prostatectomy (STvRARP) is developed in this study. The soft manipulator with 10 mm in diameter and a maximum bending angle of 270? has good flexibility and dexterity. The design and mechanical structure of the soft robot are described. The kinematics of the soft manipulator is established and the inverse kinematics is compensated based on the characteristics of the designed soft manipulator. The master-slave control system of soft robot for surgery is built and the feasibility of the designed soft robot is verified. Reference | Related Articles | Metrics | Comments（0）

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Anti-Occlusion Object Tracking Algorithm Based on Filter Prediction CHEN Kun(陈坤), ZHAO Xu(赵旭), DONG Chunyu(董春玉), DI Zichao(邸子超), CHEN Zongzhi(陈宗枝) J Shanghai Jiaotong Univ Sci    2024, 29 (3): 400-413.   DOI: 10.1007/s12204-022-2484-8 Abstract （72）      PDF（pc） （5510KB）（36）       Knowledge map    Save Visual object tracking is an important issue that has received long-term attention in computer vision.The ability to effectively handle occlusion, especially severe occlusion, is an important aspect of evaluating theperformance of object tracking algorithms in long-term tracking, and is of great significance to improving therobustness of object tracking algorithms. However, most object tracking algorithms lack a processing mechanism specifically for occlusion. In the case of occlusion, due to the lack of target information, it is necessary to predict the target position based on the motion trajectory. Kalman filtering and particle filtering can effectively predict the target motion state based on the historical motion information. A single object tracking method, called probabilistic discriminative model prediction (PrDiMP), is based on the spatial attention mechanism in complex scenes and occlusions. In order to improve the performance of PrDiMP, Kalman filtering, particle filtering and linear filtering are introduced. First, for the occlusion situation, Kalman filtering and particle filtering are respectively introduced to predict the object position, thereby replacing the detection result of the original tracking algorithm and stopping recursion of target model. Second, for detection-jump problem of similar objects in complex scenes, a linear filtering window is added. The evaluation results on the three datasets, including GOT-10k, UAV123 and LaSOT, and the visualization results on several videos, show that our algorithms have improved tracking performance under occlusion and the detection-jump is effectively suppressed. Reference | Related Articles | Metrics | Comments（0）

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Dynamic Analysis and Optimal Parameter Design of Flexible Composite Structures via Absolute Nodal Coordinate Formulation YANG Dan(杨丹),YU Haidong*(余海东)，LIN Zhangpeng(林张鹏) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 621-629.   DOI: 10.1007/s12204-022-2419-4 Abstract （63）      PDF（pc） （2376KB）（35）       Knowledge map    Save The composite structure with the dielectric elastomer and soft materials is the main form of the actuators in soft robots. However, the theoretical model is hard to obtain due to the nonlinear large deformation of materials. In this paper, a new composite element model is established based on the absolute nodal coordinate formulation. The consistent deformation conditions at the contact interface between two thin plates are deduced. The hyperelastic constitutive model and the dielectric elastomer constitutive model are introduced for the two thin plates. Then the dynamic model is established to study the dynamic behaviors of the composite flexible structure with various parameters. The results show that the nonlinear deformation appears obviously when the flexible composite plate structure is driven by various voltages, and the warping deformation becomes more obvious with the increase of the voltage. The width and thickness of the driven thin plate influence the stability of the whole structure. With the decrease of the width or thickness, the deformation of the structure is more consistent with obvious periodicity, and the control performance is improved. Finally, the structural parameters of the composite structures are optimized to improve the control performance based on the dynamic performance. Additionally, smaller width and thickness parameters are preferred to obtain better performance in the design of flexible actuator of soft robot. Reference | Related Articles | Metrics | Comments（0）

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Measuring Transverse Relaxation Time of Xenon Atoms Based on Single Beam of Laser in Nuclear Magnetic Resonance Gyroscope ZHONG Guochen1(钟国宸),LIU Hual*(刘华), GUo Yang1(郭阳)，LI Shaoliang2(李绍良)，ZHAO Wanliang2(赵万良)，CHENG Yuxiang2(成宇翔) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 569-576.   DOI: 10.1007/s12204-022-2436-3 Abstract （79）      PDF（pc） （1758KB）（35）       Knowledge map    Save Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxation time (T2) of the xenon nuclear spin in the atomic cell of the NMRG directly affects the angular random walk of the gyro. Accurate and rapid measurement of T2 is conducive to further improvement of gyroscope. At present, for the measurement of T2, the schemes of two orthogonal lasers for pumping and detecting are usually used. By applying two fast-switching orthogonal static magnetic fields and a single beam of circularly polarized laser with corresponding wavelength to pump the atomic cell, the xenon nuclear macroscopic magnetic moment Larmor precession is generated. The cesium atoms parametric magnetometer in cell is formed to detect the free induction decay signal generated by nuclear spin precession of xenon atoms. The measurement of T2 by a single laser simplifies the measurement equipment compared with traditional method with two lasers. The experimental results show that the T2 of xenon atoms is more than 10 s, and the effects of temperature are studied, which lay the foundation for the subsequent improvement of gyro performance. Reference | Related Articles | Metrics | Comments（0）

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Optimization of Group Multiattribute Decision-Making Model in Commercial Space Investment ZHANG Yiming (张-鸣)，HOU Junjie1* (侯俊杰)，ZHONG Shaowen2 (钟少文) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 831-840.   DOI: 10.1007/s12204-021-2400-7 Abstract （62）      PDF（pc） （291KB）（33）       Knowledge map    Save A group multiattribute decision-making model was proposed by implementing prospect theory, multiattribute decision-making, group decision-making and entropy methods for the optimization in commercial space investment. First, the decision-making function was decided using prospect theory by the preference of each expert to reach the comprehensive prospect value based on different investment options; second, expert decision weights were reached according to entropy method; third, the expert group decision-making information was congregated according to the group decision-making congregation algorithm to reach the most optimized investment option; finally, an example was given to demonstrate the feasibility and effectiveness of the method. This model comprehensively takes the advantages of many methods to congregate experts’ experiences and avoid the subjective influences, thus providing a scientific decision-making approach for the commercial space investment. Reference | Related Articles | Metrics | Comments（0）

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CT Image Segmentation Method of Composite Material Based on Improved Watershed Algorithm and U-Net Neural Network Model XUE Yongboa (薛永波)，LIU Zhaob (刘钊)， LI Zeyanga (李泽阳)，ZHU Pinga* (朱平) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 783-792.   DOI: 10.1007/s12204-021-2385-2 Abstract （95）      PDF（pc） （1655KB）（31）       Knowledge map    Save In the study of the composite materials performance, X-ray computed tomography (XCT) scanning has always been one of the important measures to detect the internal structures. CT image segmentation technology will effectively improve the accuracy of the subsequent material feature extraction process, which is of great significance to the study of material performance. This study focuses on the low accuracy problem of image segmentation caused by fiber cross-section adhesion in composite CT images. In the core layer area, area validity is evaluated by morphological indicator and an iterative segmentation strategy is proposed based on the watershed algorithm. In the transition layer area, a U-net neural network model trained by using artificial labels is applied to the prediction of segmentation result. Furthermore, a CT image segmentation method for fiber composite materials based on the improved watershed algorithm and the U-net model is proposed. It is verified by experiments that the method has good adaptability and effectiveness to the CT image segmentation problem of composite materials, and the accuracy of segmentation is significantly improved in comparison with the original method, which ensures the accuracy and robustness of the subsequent fiber feature extraction process Reference | Related Articles | Metrics | Comments（0）

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Stagewise Training for Hybrid-Distorted Image Restoration HOU Shujuan* (侯舒娟)，ZHU Wenping (朱文萍)，LI Hai (李海) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 793-801.   DOI: 10.1007/s12204-022-2453-2 Abstract （83）      PDF（pc） （1221KB）（31）       Knowledge map    Save Image restoration is the problem of restoring a real degraded image. Previous studies mostly focused on single distortion. However, most of the real images experience multiple distortions, and single distortion image restoration algorithms can not effectively improve the image quality. Moreover, few existing hybrid distortion image restoration algorithms can not deal with single distortion. Therefore, an end-to-end pipeline network based on stagewise training is proposed in this paper. Specifically, the network selects three typical image restoration tasks: denoising, inpainting, and super resolution. The whole training process is divided into single distortion training, hybrid distortion training of two types, and hybrid distortion training of three types. The design of loss function draws on the idea of deep supervision. Experimental results prove that the proposed method is not only superior to other methods in hybrid-distorted image restoration, but also suitable for single distortion image restoration. Reference | Related Articles | Metrics | Comments（0）

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Working Fluid Distribution and Charge Regulation Control in Organic Rankine Cycle YE Zhenhong(叶振鸿), WANG Wei(王炜), LI Xinhua(李新华), CHEN Jiangping(陈江平) J Shanghai Jiaotong Univ Sci    2024, 29 (2): 188-201.   DOI: 10.1007/s12204-022-2538-y Abstract （73）      PDF（pc） （1116KB）（31）       Knowledge map    Save Charge-based studies, in particular investigations of mass distribution, are still almost absent, although the efficiency of the organic Rankine cycle (ORC) has attracted a great deal of scholarly attention. This paper aims to provide a new perspective on the intrinsic relationship among the mass distribution, phase-zone distribution in the heat exchanger (HEX), charge of working fluid (WF), rotation speed of the pump (RSP), and system performance. A comprehensive ORC simulation model is presented by linking each component’s sub-models, including the independent models for HEX, pump, and expander in an object-oriented fashion. The visualization study of mass distribution of the WF in the system is investigated under different working conditions. Furthermore, the volume and mass of the gas phase, two-phase and liquid phase of WF in the HEX and their variation rules are analyzed in-depth. Finally, the strategies of charge reduction considering HEX areas and pipe sizes are investigated. The results show that the model based on the interior-point method provides high levels of accuracy and robustness. The mass ratio of the WF is concentrated in the liquid receiver, especially in the regenerator, which is 32.9% and 21.9% of the total mass, respectively. Furthermore, 2.4 kg (6.9%) WF in the system gradually migrates to the hightemperature side as the RSP increases while 6.1 kg (17.4%) WF migrates to the low-temperature side, especially to the condenser, as the charge in the system increases. Output power and efficiency both decrease gradually after the peak due to changes in RSP and charge. Last, reducing heat transfer areas of the condenser and regenerator is the most effective way to reduce WF charge. Reference | Related Articles | Metrics | Comments（0）

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Enhanced Tribological Performance of Diamond Films by Utilizing DLC and DLC-H Top Layers LBI Xuelin*(雷学林), YAN Ying (严莹)，ZHANG Hang(张航),LI Zizruan (李子璇), HE Yun(何云) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 665-675.   DOI: 10.1007/s12204-021-2399-9 Abstract （53）      PDF（pc） （2267KB）（31）       Knowledge map    Save High-performance diamond films are highly demanded on tool surfaces for wire-drawing and mechanical sealing applications. Herein, this work aims at enhancing the tribological performance of chemical vapor deposition diamond films in water-lubricated conditions by utilizing non-hydrogenated and hydrogenated diamond-like carbon (DLC and DLC-H) top layers. The tribological properties of bilayer micro-crystalline diamond (MCD)/DLC, MCD/DLC-H, nano-crystalline diamond (NCD)/DLC and NCD/DLC-H films are evaluated, in terms of maximal and stable coefficients of friction (COFs), C—C bonds transformation, worn surface morphology and specific wear rates. The results show that DLC or DLC-H coated on diamond layer significantly suppresses the initial maximal COF peak and the wear of counterpart ball. Moreover, severe regular arranged sp2 C—C bonds transformation is detected on MCD film, in comparison to NCD; while inversely, the NCD/DLC bilayer exhibits severer C—C bonds transformation effect compared with the MCD/DLC. Furthermore, the DLC-H top layer shows a larger decreasing rate of maximal COFs and wear rates of counterpart balls, compared with the DLC coating, which is due to its superior self-lubricity. Among all the tested films, the NCD/DLC-H bilayer shows an optimized tribological performance. Reference | Related Articles | Metrics | Comments（0）

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Retinal Vessel Segmentation via Adversarial Learning and Iterative Refinement GU Wen (顾闻), XU Yi∗ (徐奕) J Shanghai Jiaotong Univ Sci    2024, 29 (1): 73-80.   DOI: 10.1007/s12204-022-2479-5 Abstract （67）      PDF（pc） （914KB）（31）       Knowledge map    Save Retinal vessel segmentation is a challenging medical task owing to small size of dataset, micro blood vessels and low image contrast. To address these issues, we introduce a novel convolutional neural network in this paper, which takes the advantage of both adversarial learning and recurrent neural network. An iterative design of network with recurrent unit is performed to refine the segmentation results from input retinal image gradually. Recurrent unit preserves high-level semantic information for feature reuse, so as to output a sufficiently refined segmentation map instead of a coarse mask. Moreover, an adversarial loss is imposing the integrity and connectivity constraints on the segmented vessel regions, thus greatly reducing topology errors of segmentation. The experimental results on the DRIVE dataset show that our method achieves area under curve and sensitivity of 98.17% and 80.64%, respectively. Our method achieves superior performance in retinal vessel segmentation compared with other existing state-of-the-art methods. Reference | Related Articles | Metrics | Comments（0）

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Numerical Investigation on Dynamic Response Characteristics of Fluid-Structure Interaction of Gas-Liquid Two-Phase Flow in Horizontal Pipe WANG Zhiwei(王志伟), HE Yanping(何炎平), LI Mingzhi（李铭志）, QIU Ming(仇明), HUANG Chao(黄超), LIU Yadong（亚东），WANG Zi(王梓) J Shanghai Jiaotong Univ Sci    2024, 29 (2): 237-244.   DOI: 10.1007/s12204-022-2469-7 Abstract （48）      PDF（pc） （1576KB）（29）       Knowledge map    Save Fluid-structure interaction (FSI) of gas-liquid two-phase flow in the horizontal pipe is investigated numerically in the present study. The volume of fluid model and standard k-ε turbulence model are integrated to simulate the typical gas-liquid two-phase flow patterns. First, validation of the numerical model is conducted and the typical flow patterns are consistent with the Baker chart. Then, the FSI framework is established to investigate the dynamic responses of the interaction between the horizontal pipe and gas-liquid two-phase flow. The results show that the dynamic response under stratified flow condition is relatively flat and the maximum pipe deformation and equivalent stress are 1.8 mm and 7.5 MPa respectively. Meanwhile, the dynamic responses induced by slug flow, wave flow and annular flow show obvious periodic fluctuations. Furthermore, the dynamic response characteristics under slug flow condition are maximum; the maximum pipe deformation and equivalent stress can reach 4 mm and 17.5 MPa, respectively. The principal direction of total deformation is different under various flow patterns. Therefore, the periodic equivalent stress will form the cyclic impact on the pipe wall and affect the fatigue life of the horizontal pipe. The present study may serve as a reference for FSI simulation under gas-liquid two-phase transport conditions. Reference | Related Articles | Metrics | Comments（0）

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Numerical Study on Comparison of Negative and Positive Surface Discharge in c-C4F8/CF3I/CO2 Gas Mixture FAN Binhai(范彬海), ZHOU Xiaoli(周小丽), QIAN Yong(钱勇), ZANG Yiming(臧奕茗) J Shanghai Jiaotong Univ Sci    2024, 29 (2): 202-215.   DOI: 10.1007/s12204-022-2562-y Abstract （48）      PDF（pc） （2362KB）（28）       Knowledge map    Save The dynamics of negative surface discharges in c-C4F8/CF3I/CO2 gas mixture is investigated here with a 2D fluid model. The distributions of ion concentration, electric field strength and photon flux during the propagation of the streamer are obtained by solving the drift-diffusion equations of particles and Poisson’s equation, and the photon flux variation function during the propagation is also fitted. It is found that the streamer branches occur when the streamer transitions from the upper surface of the insulator to the side surface, and then when the streamer approaches the plane electrode, the photon flux will increase significantly. On this basis, the positive and negative surface discharge models are compared in terms of streamer characteristics, particle characteristics and streamer branches. It is found that the streamer has a higher electron concentration and electric field in the positive model. The streamer develops “floating” in the positive surface discharge, while it is close to the surface of the insulator in the negative model. In addition, the negative streamer branch has a wider width and develops further. Reference | Related Articles | Metrics | Comments（0）

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Influence of Kinematic Viscosity of Base Oil on Magnetorheological Grease WANG Wenchao (王文超), ZHANG Guang (张广),WANG Huiaing (汪辉兴)，YEXudan(叶绪丹)，WANG Jiong*(王炅) J Shanghai Jiaotong Univ Sci    2023, 28 (5): 676-685.   DOI: 10.1007/s12204-022-2438-1 Abstract （45）      PDF（pc） （1125KB）（27）       Knowledge map    Save In order to explore the effect of kinematic viscosity of base oil on the rheological properties of magnetorheological (MR) grease, MR grease samples containing 70% (mass fraction) carbonyl iron powder and carrier liquid separately with kinematic viscosity of 10 mm2/s, 100 mm2/s, 350 mm2/s and 500 mm2/s were prepared. The influence of kinematic viscosity of carrier liquid on the settlement performance of MR grease was analyzed. The rheological properties of MR grease were tested and analyzed under steady-state shear and oscillatory shear modes. The results show that the kinematic viscosity of base oil has a significant effect on the settling stability of MR grease. The zero-field viscosity of MR grease increases with the increase of the kinematic viscosity of the base oil, and the sedimentation performance is better. The colloid stability of MR grease is poor after the kinematic viscosity of base oil is lower than a threshold, and static oil bleed will occur immediately. In addition, the shear stress of MR grease increases with the increase of magnetic induction. When the shear rate is less than 10 s?1, the shear stress increases rapidly with the increase of shear rate. When the shear rate further increases, the shear stress tends to a stable value. The reason is that the thickener fibers in MR grease are subjected to the shear stress between laminar flows, the entanglement occurs, which makes MR grease exhibit shear thinning, and its rheological properties conform to the Herschel-Bulkley constitutive model. In the process of preparation, some carbonyl iron powder will be embedded into the thickener fiber, which shows different magnetic saturation phenomena due to shear thinning under steady-state shear and oscillatory shear. Reference | Related Articles | Metrics | Comments（0）

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Receding Horizon Control-Based Stabilization of Singular Stochastic Systems with State Delay WANG Xiaojing(王晓静),LIU Xiaohua(刘晓华), GAO Rong（高荣） J Shanghai Jiaotong Univ Sci    2024, 29 (3): 436-449.   DOI: 10.1007/s12204-022-2550-2 Abstract （29）      PDF（pc） （435KB）（25）       Knowledge map    Save For a class of discrete-time singular stochastic systems with multi-state delay, the stabilization problem of receding horizon control (RHC) is concerned. Due to the difficulty in solving the proposed optimization problem, the RHC stabilization for such systems has not been solved. By adopting the forward and backward equation technique, the optimization problem is solved completely. A sufficient and necessary condition for the optimization controller to have a unique solution is given when the regularization and pulse-free conditions are satisfied. Based on this controller, an RHC stabilization condition is derived, which is in the form of linear matrix inequality. It is proved that the singular stochastic system with multi-state delay is stable in the mean-square sense under appropriate assumptions when the terminal weighting matrix satisfies the given inequality. Numerical examples show that the proposed RHC method is effective in stabilizing singular stochastic systems with multi-state delay. Reference | Related Articles | Metrics | Comments（0）

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Off-Grid Sparse Bayesian Inference with Biased Total Grids for Dense Time Delay Estimation WEI Shuang (魏爽)， LI Wenyao (李文瑶)，SU Ying* (苏颖)， LIU Rui (刘睿) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 763-771.   DOI: 10.1007/s12204-022-2464-z Abstract （73）      PDF（pc） （831KB）（24）       Knowledge map    Save For dense time delay estimation (TDE), when multiple time delays are located within a grid interval, it is difficult for the existing sparse Bayesian learning/inference (SBL/SBI) methods to obtain high estimation accuracy to meet the application requirements. To solve this problem, this paper proposes a method named off-grid sparse Bayesian inference - biased total grid (OGSBI-BTG), where a mesh evolution process is conducted to move the total grids iteratively based on the position of the off-grid between two grids. The proposed method updates the off-grid dictionary matrix by further reconstructing an optimum mesh and offsetting the off-grid vector. Experimental results demonstrate that the proposed approach performs better than other state-of-the-art SBI methods and multiple signal classification even when the grid interval is larger than the gap of true time delays. In this paper, the time domain model and frequency domain model of TDE are studied. Reference | Related Articles | Metrics | Comments（0）

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Tail-Bound Cost Analysis over Nondeterministic Probabilistic Programs WANG Peeixin(王培新) J Shanghai Jiaotong Univ Sci    2023, 28 (6): 772-782.   DOI: 10.1007/s12204-022-2456-z Abstract （55）      PDF（pc） （654KB）（24）       Knowledge map    Save For probabilistic programs, there is some work for qualitative and quantitative analysis about expectation or mean, such as expected termination time, and expected cost analysis. However, another non-trivial issue is about tail bounds (i.e., upper bounds of tail probabilities), which can provide high-probability guarantees to extreme events. In this work, we focus on the problem of tail-bound cost analysis over nondeterministic probabilistic programs, which aims to automatically obtain the tail bound of resource usages over such programs. To achieve this goal, we present a novel approach, combined with a suitable concentration inequality, to derive the tail bound of accumulated cost until program termination. Our approach can handle both positive and negative costs. Moreover, our approach enables an automated template-based synthesis of supermartingales and leads to an efficient polynomial-time algorithm. To show the effectiveness of our approach, we present experimental results on various programs and make a comparison with state-of-the-art tools. Reference | Related Articles | Metrics | Comments（0）