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Acta Mechanica Sinica 2016年第2期32卷 244-251页

作者： Kun xu guo-qing xu Chun-Hua Zheng Shenzhen Institutes of Advanced Technology Chinese Academy of Sciencesand The Chinese University of Hong Kong Shenzhen College of Advanced Technology University of Chinese Academy of Sciences School of Electronics and Information Tongji University

The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy *** remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact *** research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion ***,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode *** proposed methodology achieves the optimal braking *** simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.

关键词： High speed electric multiple unit(EMU) train Regenerative braking Wheel-rail adhesion Optimal slip ratio

Seasonal occurrence of Aphis glycines and physiological responses of soybean plants to its feeding

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Insect Science 2014年第3期21卷 342-351页

作者： Xing-Ya Wang Li-Hong Zhou Biao xu Xing Xing guo-qing xu Accepted February 10 2014 Institute of Flower Research Liaoning Academy of Agricultural Sciences Shenyang Agricultural Technology Extension Center of Xiuyan Manchu Autonomous County Anshan Liaoning China

The soybean aphid Aphis glycines Matsumura （Hemiptera： Aphididae） is an important pest of soybean in China. To monitor and manage this pest effectively it is neces-sary to understand its population dynamics and demographics, as well as the physiological responses of soybean plants to its feeding. In this study, using field surveying and suction-trap monitoring, we investigated the population dynamics of the soybean aphid in Xiuyan County, Liaoning Province in northeastern China during 2009-2012. The results indicatedthat the population dynamics of the soybean aphid followed a unimodal curve distribution, with the insect generally colonizing soybean fields from the middle of June to early Julyand the population reaching a peak between early July and early August. On the whole, soybean aphids occurred in suction-traps at least 2 weeks earlier than they were foundin field surveys. A total of 72 alates were collected by suction-trapping over the 4 years, with the earliest alate captures occurring on 28 May in 2009, 2011, 2012 and 4 June in 2010. The life table parameters clearly showed that this aphid had a short doubling time （4.73 ± 0.21 days）, and 7.36± 0.98 nymphs were produced by a soybean aphid adult during its lifetime （13.57 ± 0.30 days）. Finally, biochemical assays indicated that the amount of malondialdehyde and the activities of four defense-related enzymes in soybean leavessignificantly changed between 0 day and 7 days of aphid infestation. Polyphenol oxidase （PPO） and catalase （CAT） activities increased more dramatically after 1 day of aphid feed-ing. In addition, significantly higher levels of superoxide dismutase and CAT were found after aphid feeding for 7 days, whereas there was no significant change in the activitiesof peroxidase and PPO. Consequently, this study will be beneficial in determining the seasonal occurrence of the soybean aphid and selecting insect-resistant soybean varieties,and thus in developing a theoretical framework for appropriate m

关键词： Aphis glycines defense-related enzymes life table population dynamics suction trap

Numerical simulation of hydraulic fracture propagation in tight oil reservoirs by volumetric fracturing

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Petroleum Science 2015年第4期12卷 674-682页

作者： Shi-Cheng Zhang Xin Lei Yu-Shi Zhou guo-qing xu College of Petroleum Engineering University of Petroleum

Volumetric fracturing is a primary stimulation technology for economical and effective exploitation of tight oil reservoirs. The main mechanism is to connect natural fractures to generate a fracture network system which can enhance the stimulated reservoir volume. By using the combined finite and discrete element method, a model was built to describe hydraulic fracture propagation in tight oil reservoirs. Considering the effect of horizontal stress difference, number and spacing of perforation clus- ters, injection rate, and the density of natural fractures on fracture propagation, we used this model to simulate the fracture propagation in a tight formation of a certain oil- field. Simulation results show that when the horizontal stress difference is lower than 5 MPa, it is beneficial to form a complex fracture network system. If the horizontal stress difference is higher than 6 MPa, it is easy to form a planar fracture system; with high horizontal stress differ- ence, increasing the number of perforation clusters is beneficial to open and connect more natural fractures, and to improve the complexity of fracture network and the stimulated reservoir volume （SRV）. As the injection rate increases, the effect of volumetric fracturing may be improved; the density of natural fractures may only have a great influence on the effect of volume stimulation in a low horizontal stress difference.

关键词： Tight oil reservoir Volumetric fracturingFracture propagation Horizontal stress difference Stimulated reservoir volume

Construction of a new regular LDPC code for optical transmission systems

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Optoelectronics Letters 2013年第3期9卷 204-207页

作者： YUAN Jian-guo TONG qing-zhen xu Liang HUANG Sheng Key Lab. of Optical Fiber Communications Technology Chongqing University of Posts and TelecommunicationsChongqing 400065 China

A novel construction method of the check matrix for the regular low density parity check （LDPC） code is proposed. The novel regular systematically constructed Gallager （SCG）-LDPC（3969,3720） code with the code rate of 93.7% and the redundancy of 6.69% is constructed. The simulation results show that the net coding gain （NCG） and the distance from the Shannon limit of the novel SCG-LDPC（3969,3720） code can respectively be improved by about 1.93 dB and 0.98 dB at the bit error rate （BER） of 10s, compared with those of the classic RS（255,239） code in ITU-T G.975 recommendation and the LDPC（32640,30592） code in ITU-T G.975.1 recommendation with the same code rate of 93.7% and the same redundancy of 6.69%. Therefore, the proposed novel regular SCG-LDPC（3969,3720） code has excellent performance, and is more suitable for high-speed long-haul optical transmission systems.

关键词：规则LDPC码光传输系统低密度奇偶校验 ITU-T 代码率校验矩阵正规系统仿真结果

Prescribed Performance Tracking Control of Time-Delay Nonlinear Systems With Output Constraints

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IEEE/CAA Journal of Automatica Sinica 2024年第7期11卷 1557-1565页

作者： Jin-Xi Zhang Kai-Di xu qing-guo Wang IEEE the State Key Laboratory of Synthetical Automation for Process Industries Northeastern UniversityShenyang 110819China Institute of Artificial Intelligence and Future Networks Beijing Normal UniversityZhuhai 519087 Guangdong Key Laboratory of Artificial Intelligence and Multi-Modal Data Processing Beijing Normal University-Hong Kong Baptist University United International CollegeZhuhai 519087

The problem of prescribed performance tracking control for unknown time-delay nonlinear systems subject to output constraints is dealt with in this paper. In contrast with related works, only the most fundamental requirements, i.e., boundedness and the local Lipschitz condition, are assumed for the allowable time delays. Moreover, we focus on the case where the reference is unknown beforehand, which renders the standard prescribed performance control designs under output constraints infeasible. To conquer these challenges, a novel robust prescribed performance control approach is put forward in this ***, a reverse tuning function is skillfully constructed and automatically generates a performance envelop for the tracking error. In addition, a unified performance analysis framework based on proof by contradiction and the barrier function is established to reveal the inherent robustness of the control system against the time delays. It turns out that the system output tracks the reference with a preassigned settling time and good accuracy,without constraint violations. A comparative simulation on a two-stage chemical reactor is carried out to illustrate the above theoretical findings.

关键词： Nonlinear systems output constraints prescribed performance reference tracking time delays

Sirolimus improves the prognosis of liver recipients with hepatocellular carcinoma:A single-center experience

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Hepatobiliary & Pancreatic Diseases International 2023年第1期22卷 34-40页

作者： Peng Liu Xin Wang Huan Liu Shu-Xian Wang qing-guo xu Lin Wang Xiao xu Jin-Zhen Cai Organ Transplantation Center The Affiliated Hospital of Qingdao UniversityQingdao 266100China Institute of Organ Donation and Transplantation Department of MedicineQingdao UniversityQingdao 266100China Department of Hepatobiliary and Pancreatic Surgery The Center for Integrated Oncology and Precision MedicineAffiliated Hangzhou First People’s HospitalZhejiang University School of MedicineHangzhou 310003China National Health Commission(NHC)Key Laboratory of Combined Multi-Organ Transplantation Hangzhou 310003China Institute of Organ Transplantation Zhejiang UniversityHangzhou 310003China

Background:Tumor recurrence after liver transplantation(LT)for selective patients diagnosed with hepatocellular carcinoma(HCC)in the setting of cirrhosis is the greatest challenge effecting the prognosis of these *** aim of this study was to evaluate the efficacy of sirolimus on the prognosis for these ***:The data from 193 consecutive HCC patients who had undergone LT from January 2015 to December 2019 were retrospectively *** patients were divided into the sirolimus group[patients took sirolimus combined with calcineurin inhibitors(CNIs)(n=125)]and non-sirolimus group[patients took CNI-based therapy without sirolimus(n=68)].Recurrence-free survival(RFS)and overall survival(OS)were compared between the two *** prognostic factors and independent risk factors for RFS and OS were further ***:Non-sirolimus was an independent risk factor for RFS(HR=2.990;95%CI:1.050-8.470;P=0.040)and OS(HR=3.100;95%CI:1.190-8.000;P=0.020).A higher proportion of patients beyond Hangzhou criteria was divided into the sirolimus group(69.6%vs.80.9%,P=0.030).Compared with the non-sirolimus group,the sirolimus group had significantly better RFS(P<0.001)and OS(P<0.001).Further subgroup analysis showed similar ***:This study demonstrated that sirolimus significantly decreased HCC recurrence and prolonged RFS and OS in LT patients with different stage of HCC.

关键词： Hepatocellular carcinoma Liver transplantation Sirolimus Tumor recurrence Recurrence-free survival Overall survival

Thermal conductive proppant with self-suspension ability

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Petroleum Science 2023年第3期20卷 1742-1749页

作者： guo-qing xu Xiu-Ping Lan Si-Si hao Kai-Yi Hu Si-Meng Qi Li-Dong Geng Quan xu Yang Zhou Sinopec Key Laboratory of Drilling Completion and Fracturing of Shale Oil and Gas SINOPEC Research Institute of Petroleum Engineering Co.LtdBejing102249China State Key Laboratory of Petroleum Resources and Prospecting Bejing Key Laboratoryof Biogas Upgrading UtilizationHarvard SEAS-CUPB Joint Laboratory on Petroleum ScienceChina University of Petroleum(Beijing)Beijing102249China

The in situ mining technology is applied to the exploitation of medium-and low-maturity shale oil,which can use heaters to warm up the oil shale formations and pyrolyze the *** to the low thermal conductivity of oil shale,electric heaters need extra equipment to improve heat transfer *** this study,a thermally conductive proppant is fabricated by coating epoxy-resin and graphite on ceramic proppants for the first time,which could support the fracturing crack and transfer *** thermal conduction property of epoxy-resin and graphite coated proppants(EGPs)is 245%higher than that of uncoated proppants,which can transfer more heat to the oil shale formation and accelerate the conversion of *** adhesive property of EGPs is improved by 47.9%under the load force of 1500 nN,which prolongs the time for the fracture to *** summary,this novel proppant is expected to assist in-situ mining technology in the production of medium and low-maturity shale oil.

关键词： Exploitation of shaleoil In situ mining Technology Thermally conductive proppant Heat transfer

Synthesis and paste properties of octenyl succinic anhydride modified early Indica rice starch

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2006年第10期7卷 800-805页

作者： SONG Xiao-yan CHEN Qi-he RUAN Hui HE guo-qing xu Qiong Department of Food Science and Nutrition Zhejiang University Hangzhou 310029 China

Octenyl succinic anhydride （OSA） modified early Indica rice starch was prepared in aqueous slurry systems using response surface methodology. The paste properties of the OSA starch were also investigated. Results indicated that the suitable parameters for the preparation of OSA starch from early Indica rice starch were as follows： reaction period 4 h, reaction temperature 33.4℃, pH of reaction system 8.4, concentration of starch slurry 36.8% （in proportion to water, w/w）, amount of OSA 3% （in proportion to starch, w/w）. The degree of substitution was 0.0188 and the reaction efficiency was 81.0%. The results of paste properties showed that with increased OSA modification, the starch derivatives had higher paste clarity, decreased retrogradation and better freeze-thaw stability.

关键词： Early Indica rice OSA starch Response surface methodology Paste properties

Flexible assistance strategy of lower limb rehabilitation exoskeleton based on admittance model

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Science China(Technological Sciences) 2024年第3期67卷 823-834页

作者： KOU JianGe WANG Yixuan CHEN ZhenLei SHI Yan guo qing xu Meng School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China School of Aeronautics and Astronautics University of Electronic Science and Technology of ChinaChengdu 611731China Department of Musculoskeletal Tumor Senior Department of Orthopedicsthe Fourth Medical Centerof PLA GeneralHospitalBeijing 100853China

Exercise training based on exoskeleton is an effective rehabilitation method for stroke patients. However, some rehabilitation exoskeletons still have poor wearable performance and obvious human-robot impedance during training, which easily cause secondary injuries to the patients. In this study, a variable admittance control strategy is proposed to improve the operator's wearable comfort, which can adapt to different operators by regulating admittance parameters. The admittance controller has two feedback loops: the position inner-loop and the admittance outer-loop. Meanwhile, the exoskeleton Lagrange model is constructed with unknown friction disturbance. By using Lyapunov technique and backstepping with state observer, the joint position error of exoskeleton is convergence into a zero neighborhood. The effectiveness of the proposed admittance controller is verified by both simulation and experiment. The tracking error of hip and knee joint is less than 4 degrees while the human-robot interaction torque is constrained in a tolerable range of the operator.

关键词： human-robot interaction exoskeleton backstepping admittance control

Hybrid bonding of GaAs and Si wafers at low temperature by Ar plasma activation

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Journal of Semiconductors 2024年第4期45卷 69-75页

作者： Rui Huang Zhiyong Wang Kai Wu Hao xu qing Wang Yecai guo School of Electronic and Information Engineering Wuxi UniversityWuxi 214105China Institute of Advanced Technology on Semiconductor Optics&Electronics Institute of Laser EngineeringBeijing University of TechnologyBeijing 100124China

High-quality bonding of 4-inch GaAs and Si is achieved using plasma-activated bonding *** influence of Ar plasma activation on surface morphology is *** the annealing temperature is 300℃,the bonding strength reaches a maximum of 6.2 *** addition,a thermal stress model for GaAs/Si wafers is established based on finite element analysis to obtain the distribution of equivalent stress and deformation variables at different *** shape varia-tion of the wafer is directly proportional to the annealing *** an annealing temperature of 400℃,the maximum protrusion of 4 inches GaAs/Si wafers is 3.6 *** interface of GaAs/Si wafers is observed to be dense and defect-free using a transmission electron *** characterization of interface elements by X-ray energy dispersion spectroscopy indi-cates that the elements at the interface undergo mutual diffusion,which is beneficial for improving the bonding strength of the *** is an amorphous transition layer with a thickness of about 5 nm at the bonding *** preparation of Si-based GaAs heterojunctions can enrich the types of materials required for the development of integrated circuits,improve the performance of materials and devices,and promote the development of microelectronics technology.

关键词： plasma-activated bonding bonding strength thermal stress model mutual diffusion