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网络电信 2006年第12期8卷 17-20页

作者： G．Baker T．Kama G．Marciano z.shen

移动运营商在高速增长的市场中的关键挑战和机遇是如何服务当前没有享受或正在享受服务的用户，并从中获取收益。

关键词：移动业务创新移动运营商商业模型服务市场收益

Stability Investigation and Improvement for DC Cascade Systems with Simplified Impedance-based Stability Criterion

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1044-1052页

作者： Junbin Fang zhikang Shuai Yang Li zhibing Wang Xiangyang Wu Xia shen z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410082China Renewable Energy Department of China Electric Power Research Institute Beijing 100192China Department of Electrical and Computer Engineering Illinois Institute of TechnologyChicagoIL 60616USA IEEE

In DC distributed power systems(DPSs),the complex impedance interactions possibly lead to DC bus voltage oscillation or collapse.In previous research,the stability analysis of DPSs is implemented based on mathematical analysis in control theory.The specific mechanisms of the instability of the cascade system have not been intuitively clarified.In this paper,the stability analysis of DPSs based on the traditional Nyquist criterion is simplified to the resonance analysis of the seriesconnected port impedance(z=R+jX)of source and load converters.It reveals that the essential reason for impedance instability of a DC cascade system is that the negative damping characteristic(Rzero-crossing frequency.The simplified stability criterion for DC cascade systems can be concluded as:in the negative damping frequency ranges(Rzero-crossing point of the reactance component(i.e.,X=0).According to the proposed stability criterion,the oscillation modes of cascade systems are classified.A typical one is the internal impedance instability excited by the negative damping,and the other one is that the external disturbance amplified by negativity in a low stability margin.Thus,the impedance reshaping method for stability improvement of the system can be further specified.The validity of the simplified criterion is verified theoretically and experimentally by a positive damping reshaping method.

关键词： DC cascaded system,impedance model impedance reconstruction stability criterion

Asymmetrical Fault Current Calculation Method and Influencing Factors Analysis of Droop-Controlled Inverters

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 562-573页

作者： Huimin zhao zhikang Shuai Jun Ge An Luo Weimin Wu z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410006China Electrical Engineering Department Shanghai Maritime UniversityShanghai 201306China Department of Electrical and Computer Engineering Ilinois Institute of TechnologyChicagoIL 60616 USA

Since the fault dynamic of droop-controlled inverter is different from synchronous generators (SGs), protection devices may become invalid, and the fault overcurrent may damage power electronic devices and threaten the safety of the microgrid. Therefore, it is imperative to conduct a comprehensive fault analysis of the inverter to guide the design of protection schemes. However, due to the complexity of droop control strategy, existing literatures have simplified asymmetric fault analysis of droop-controlled inverters to varying degrees. Therefore, accurate fault analysis of a droop-controlled inverter is needed. In this paper, by analyzing the control system, an accurate fault model is established. Based on this, a calculation method for instantaneous asymmetrical fault current is proposed. In addition, the current components and current characteristics are analyzed. It was determined that fault currents are affected by control loops, fault types, fault distance and nonlinear limiters. In particular, the influences of limiters on the fault model, fault current calculation and fault current characteristics were analyzed. Through detailed analysis, it was found that dynamics of the control loop cannot be ignored, the fault type and fault distance determine fault current level, and part of the limiters will totally change the fault current trend. Finally, calculation and experimental results verify the correctness of the proposed method.

关键词： Asymmetrical fault analysis droop control fault current calculation method limiter transient fault characteristics

Post-layout simulation driven analog circuit sizing

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Science China(Information Sciences) 2024年第4期67卷 289-300页

作者： Xiaohan GAO Haoyi zHANG Siyuan YE Mingjie LIU David z.PAN Linxiao shen Runsheng WANG Yibo LIN Ru HUANG School of Integrated Circuits Peking University School of Computer Science Peking University Department of Electrical and Computer Engineering University of Texas at Austin Institute of Electronic Design Automation Peking University

Post-layout simulation provides accurate guidance for analog circuit design, but post-layout performance is hard to be directly optimized at early design stages. Prior work on analog circuit sizing often utilizes pre-layout simulation results as the optimization objective. In this work, we propose a post-layoutsimulation-driven(post-simulation-driven for short) analog circuit sizing framework that directly optimizes the post-layout simulation performance. The framework integrates automated layout generation into the optimization loop of transistor sizing and leverages a coupled Bayesian optimization algorithm to search for the best post-simulation performance. Experimental results demonstrate that our framework can achieve over 20% better post-layout performance in competitive time than manual design and the method that only considers pre-layout optimization.

关键词： analog EDA transistor sizing Bayesian optimization post-layout simulation

Rational Solutions of First Order Algebraic Ordinary Differential Equations

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Journal of Systems Science & Complexity 2024年第2期37卷 567-580页

作者： FENG Shuang shen Liyong School of Physical and Mathematical Sciences Nanjing Tech UniversityNanjing 211816China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China

Let f(t,y,y')=∑ _(i=0)^(n )a_(i)(t,y)y'^(i)=0 be an irreducible first order ordinary differential equation with polynomial coefficients.Eremenko in 1998 proved that there exists a constant C such that every rational solution of f(t,y,y')=0 is of degree not greater than C.Examples show that this degree bound C depends not only on the degrees of f in t,y,y' but also on the coefficients of f viewed as the polynomial in t,y,y'.In this paper,the authors show that if f satisfies deg(f,y)0,then the degree bound C only depends on the degrees of f in t,y,y',and furthermore we present an explicit expression for C in terms of the degrees of f in t,y,y'.

关键词： Degree bound first order AODE height rational solution

Solid-state Circuit Breaker Based on Cascaded Normally-on SiC JFETs for Medium-voltage DC Distribution Networks

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Protection and Control of Modern Power Systems 2024年第2期9卷 32-46页

作者： Dong He Haohui zhou zheng Lan Wei Wang Jinhui zeng Xueping Yu z.John shen Chongqing University of Posts and Telecommunications ChongqingChina Henan Polytechnic University JiaozuoChina College of Electrical and Information Engineering Hunan University of TechnologyZhuzhou 412007China Hunan University ChangshaChina College of Electrical and Information Engineering Hunan UniversityChangshaChina College of Electrical Engineering Three Gorges University Rensselaer Polytechnic Institute TroyNYUSA

Solid-state circuit breakers(SSCBs)are critical components in the protection of medium-voltage DC distribution networks to facilitate arc-free,fast and reliable isolation of DC faults.However,limited by the capacity of a single semiconductor device,using semi-conductor-based SSCBs at high voltage is challenging.This study presents the details of a 1.5 kV,63 A medi-um-voltage SSCB,composed primarily of a solid-state switch based on three cascaded normally-on silicon car-bide(SiC)junction field-effect transistors(JFETs)and a low-cost programmable gate drive circuit.Dynamic and static voltage sharing among the cascaded SiC JFETs of the SSCB during fault isolation is realized using the pro-posed gate drive circuit.The selection conditions for the key parameters of the SSCB gate driver are also analyzed.Additionally,an improved pulse-width modulation cur-rent-limiting protection solution is proposed to identify the permanent overcurrent and transient inrush current associated with capacitive load startup in a DC distribu-tion network.Using the developed SSCB prototype and the fault test system,experimental results are obtained to validate the fault response performance of the SSCB.Index Terms—Solid-state circuit breaker,DC distribu-tion network,SiC JFET,voltage balancing,inrush current.

关键词： Solid-state circuit breaker DC distribu-tion network SiC JFET voltage balancing inrush current

Advances in MET tyrosine kinase inhibitors in gastric cancer

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Cancer Biology & Medicine 2024年第6期21卷 484-498页

作者： Yifan zhang Lin shen zhi Peng Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education) Department of Gastrointestinal Oncology Peking University Cancer Hospital & Institute State Key Laboratory of Holistic Integrative Management of Gastrointestinal Cancers Beijing Key Laboratory of Carcinogenesis and Translational Research Department of Gastrointestinal Oncology Peking University Cancer Hospital & Institute

Gastric cancer is among the most frequently occurring cancers and a leading cause of cancer-related deaths globally. Because gastric cancer is highly heterogenous and comprised of different subtypes with distinct molecular and clinical characteristics, the management of gastric cancer calls for better-defined, biomarker-guided, molecular-based treatment strategies. MET is a receptor tyrosine kinase mediating important physiologic processes, such as embryogenesis, tissue regeneration, and wound healing. However, mounting evidence suggests that aberrant MET pathway activation contributes to tumour proliferation and metastasis in multiple cancer types, including gastric cancer, and is associated with poor patient outcomes. As such, MET-targeting therapies are being actively developed and promising progress has been demonstrated, especially with MET tyrosine kinase inhibitors. This review aims to briefly introduce the role of MET alterations in gastric cancer and summarize in detail the current progress of MET tyrosine kinase inhibitors in this disease area with a focus on savolitinib, tepotinib, capmatinib, and crizotinib. Building on current knowledge, this review further discusses existing challenges in MET alterations testing, possible resistance mechanisms to MET inhibitors, and future directions of MET-targeting therapies.

关键词： Gastric cancer MET alterations MET testing MET tyrosine kinase inhibitors savolitinib

Biotic and abiotic stresses on honeybee health

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Integrative zoology 2024年第3期19卷 442-457页

作者： zheguang LIN Siyi shen Kang WANG Ting JI Apicultural Research Institute College of Animal Science and TechnologyYangzhou UniversityYangzhouChina

Honeybees are the most critical pollinators providing key ecosystem services that underpin crop production and sustainable agriculture.Amidst a backdrop of rapid global change,this eusocial insect encounters a succession of stressors during nesting,foraging,and pollination.Ectoparasitic mites,together with vectored viruses,have been recognized as central biotic threats to honeybee health,while the spread of invasive giant hornets and small hive beetles also increasingly threatens colonies worldwide.Cocktails of agrochemicals,including acaricides used for mite treatment,and other pollutants of the environment have been widely documented to affect bee health in various ways.Additionally,expanding urbanization,climate change,and agricultural intensification often result in the destruction or fragmentation of flower-rich bee habitats.The anthropogenic pressures exerted by beekeeping management practices affect the natural selection and evolution of honeybees,and colony translocations facilitate alien species invasion and disease transmission.In this review,the multiple biotic and abiotic threats and their interactions that potentially undermine bee colony health are discussed,while taking into consideration the sensitivity,large foraging area,dense network among related nestmates,and social behaviors of honeybees.

关键词： abiotic stressor Apis biotic stressor colony losses interaction effect pollinator decline

Improving surface integrity of micro-holes in ECDM using ultrahigh-speed rotary of tool cathode and non-water-based electrolyte

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Chinese Journal of Aeronautics 2024年第5期37卷 506-519页

作者： Jiwen shen Weijing KONG zhengyang XU Yongbin zENG Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The surface integrity of metal micro-hole structures produced by electrochemical discharge machining is unsatisfactory owing to the insufficient reaction area and strength of electrolysis action.A novel ultrahigh-speed Rotary Electrochemical Discharge Machining(R-ECDM)using non-water-based electrolyte is proposed to improve surface integrity by changing the breakdown medium of spark discharge and increasing the reaction area and strength of electrolysis.A mathematical model was developed to establish the relationship between rotational speed and forces acting on the bubble.Based on the magnitude of forces,controlling rotational speed changed the behavior and departure radius of bubbles on the cathode surface.High-speed photographs validate that,in the mathematical model,the number and departure radius of bubbles on the cathode surface gradually decrease with the increase of rotational speed.The experimental results show that the roughness(Ra)of the micro-hole sidewall decreases from 2.54μm to 0.20μm when the rotational speed increases from 500 r/min to 40000 r/min.The length loss and wear ratio of the cathode are only 9.75μm and 6.5%,respectively.Finally,the micro-holes array with recast-free and surface roughness of 0.20μm is fabricated,demonstrating that the proposed approach contributes to improving surface integrity of metal micro-holes.

关键词： Electrochemical discharge machining Micro-holes Recast layer Ultrahigh-speed rotary Bubbles Force analysis Non-water-based solution

Microglia regulate RVLM-projecting PVN neuronal activity

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Microglia regulate RVLM-projecting PVN neuronal activity