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Inverse-time Backup Protection Based on Unified Characteristic Equation for Distribution Networks with high Proportion of Distributed Generations

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 202-212页

作者： Nana chang Guobing Song Zhongxue chang Yuping Zheng Xingang Yang the School of Electrical Engineering Xi’an Jiaotong UniversityXi’anChina State Key Laboratory of Smart Grid Protection and Control NARI Group CorporationNanjingChina Electric Power Research Institute of State Grid Shanghai Electric Power Company ShanghaiChina

The setting work of backup protection using steady-state current is tedious,and mismatches occasionally occur due to the increased proportion of distributed generations(DGs)connected to the power grid.Thus,there is a practical need to study a backup protection technology that does not require step-by-step setting and can be adaptively coordinated.This paper proposes an action sequence adaptive to fault positions that uses only positive sequence fault component(PSFC)voltage.Considering the influence of DGs,the unified time dial setting can be obtained by selecting specific points.The protection performance is improved by using the adjacent upstream and downstream protections to meet the coordination time interval in the case of metallic faults at the near-and far-ends of the line.Finally,the expression and implementation scheme for inverse-time backup protection(ITBP)based on the unified characteristic equation is given.Simulation results show that this scheme can adapt to DG penetration scenarios and can realize the adaptive coordination of multi-level relays.

关键词： Inverse-time backup protection(ITBP) distributed generation(DG) positive sequence fault component(PSFC)voltage unified characteristic equation adaptive coordination

Cell replacement with stem cell-derived retinal ganglion cells from different protocols

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Neural Regeneration Research 2024年第4期19卷 807-810页

作者： Ziming Luo Kun-Che chang Spencer Center for Vision Research Byers Eye InstituteStanford University School of Medicine Department of Ophthalmology Louis J.Fox Center for Vision RestorationUniversity of Pittsburgh School of Medicine Department of Neurobiology Center of NeuroscienceUniversity of Pittsburgh School of Medicine

Glaucoma,characterized by a degenerative loss of retinal ganglion cells,is the second leading cause of blindness worldwide.There is currently no cure for vision loss in glaucoma because retinal ganglion cells do not regenerate and are not replaced after injury.human stem cell-derived retinal ganglion cell transplant is a potential therapeutic strategy for retinal ganglion cell degenerative diseases.In this review,we first discuss a 2D protocol for retinal ganglion cell differentiation from human stem cell culture,including a rapid protocol that can generate retinal ganglion cells in less than two weeks and focus on their transplantation outcomes.Next,we discuss using 3D retinal organoids for retinal ganglion cell transplantation,comparing cell suspensions and clusters.This review provides insight into current knowledge on human stem cell-derived retinal ganglion cell differentiation and transplantation,with an impact on the field of regenerative medicine and especially retinal ganglion cell degenerative diseases such as glaucoma and other optic neuropathies.

关键词： cell clumps cell suspension cell transplantation differentiation direct-induced protocol glaucoma optic neuropathy regenerative medicine retinal ganglion cell retinal organoids stem cells

Event-triggered h_(∞) consensus control for input-constrained multi-agent systems via reinforcement learning

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Control Theory and Technology 2024年第1期22卷 25-38页

作者： Jinxuan Zhang chang-E Ren College of Information Engineering Capital Normal UniversityBeijing100089China

This article presents an event-triggered h_(∞) consensus control scheme using reinforcement learning (RL) for nonlinear second-order multi-agent systems (MASs) with control constraints. First, considering control constraints, the constrained h_(∞) consensus problem is transformed into a multi-player zero-sum game with non-quadratic performance functions. Then, an event-triggered control method is presented to conserve communication resources and a new triggering condition is developed for each agent to make the triggering threshold independent of the disturbance attenuation level. To derive the optimal controller that can minimize the cost function in the case of worst disturbance, a constrained hamilton–Jacobi–Bellman (hJB) equation is defined. Since it is difficult to solve analytically due to its strongly non-linearity, reinforcement learning (RL) is implemented to obtain the optimal controller. In specific, the optimal performance function and the worst-case disturbance are approximated by a time-triggered critic network;meanwhile, the optimal controller is approximated by event-triggered actor network. After that, Lyapunov analysis is utilized to prove the uniformly ultimately bounded (UUB) stability of the system and that the network weight errors are UUB. Finally, a simulation example is utilized to demonstrate the effectiveness of the control strategy provided.

关键词： h_(∞)optimal control Input constrains Multi-agent systems(MASs) Reinforcement learning(RL)

Effect of heat treatment on microstructure and mechanical properties of selective laser-melted Ph13-8Mo stainless steel

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Journal of Iron and Steel Research(International) 2024年第4期31卷 945-955页

作者： Yuan Zhang Xiang Liu chang-jun Wang chang Liu School of Material Science and Engineering Kunming University of Science and TechnologyKunming 650093YunnanChina Central Iron&Steel Research Institute Co. Ltd.Beijing 100081China

Ph13-8Mo stainless steel powder with high sphericity and well fluidity was prepared by the plasma rotating electrode process.The formed parts with ultra-high purity were manufactured by selective laser melting.The tensile and impact mechanical properties of the printed parts under three heat treatment regimes were compared to those without heat treatment.The microstructure,grain orientation and phase composition were characterized by electron-backscatter diffraction,X-ray diffraction and transmission electron microscopy.The characterization results reveal that the addition of heat treatment makes the grains enlarge,and after different heat treatments,the average grain size from 1.51μm in the printed state increases to 2.78,3.09 and 2.06μm,respectively.The formed parts are mainly composed of martensite and retained austenite.Moreover,the NiAl and M23C precipitates form,which are the major strengthening phases of Ph13-8Mo stainless steel.The optimal heat treatment process is 925℃×1 h water cooling(WC)+0℃×2 h air cooling(AC)+540℃×4 h AC.Using this heat treatment process,Ph13-8Mo formed parts have the optimal comprehensive mechanical properties:the tensile strength,yield strength and impact energy KU2 are 1492 MPa,1432 MPa and 63 J,respectively.The strengthening and toughening via heat treatment are mainly attributed to dislocation strengthening,the formation of NiAl and M23Co precipitates and the change of volume fraction of the retained austenite.

关键词： high-strength stainless steel-Selective laser melting-heat treatment Microstructure Mechanical property

A toroidal SAW gyroscope with focused IDTs for sensitivity enhancement

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Microsystems & Nanoengineering 2024年第2期10卷 47-56页

作者： Lu Tian haitao Zhao Qiang Shen honglong chang Ministry of Education Key Laboratory of Micro and Nano Systems for Aerospace School of Mechanical EngineeringNorthwestern Polytechnical UniversityXi’an710072China

A surface acoustic wave(SAW)gyroscope measures the rate of rotational angular velocity by exploiting a phenomenon known as the SAW gyroscope effect.Such a gyroscope is a great candidate for application in harsh environments because of the simplification of the suspension vibration mechanism necessary for traditional microelectromechanical system(MEMS)gyroscopes.here,for the first time,we propose a novel toroidal standing-wave-mode SAW gyroscope using focused interdigitated transducers(FIDTs).Unlike traditional SAW gyroscopes that use linear IDTs to generate surface acoustic waves,which cause beam deflection and result in energy dissipation,this study uses FIDTs to concentrate the SAW energy based on structural features,resulting in better focusing performance and increased SAW amplitude.The experimental results reveal that the sensitivity of the structure is 1.51µV/(°/s),and the bias instability is 0.77°/s,which are improved by an order of magnitude compared to those of a traditional SAW gyroscope.Thus,the FIDT component can enhance the performance of the SAW gyroscope,demonstrating its superiority for angular velocity measurements.This work provides new insights into improving the sensitivity and performance of SAW gyroscopes.

关键词： angular deflection gyroscope

Generic Modeling and Control Framework for Power Systems Dominated by Power Converters Connected Through a Passive Transmission and Distribution Grid

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 292-301页

作者： Qing-chang Zhong Marcio Stefanello Department of Electrical and Computer Engineering Illinois Institute of TechnologyChicagoIL 60616USA Syndem LLC USA.M.Stefanello is with the Fundacao Universidade Federal do Pampa at AlegreteRS97546-550Brazil

In this paper,a compact mathematical model having an elegant structure,together with a generic control framework,are proposed for generic power systems dominated by power converters that are interconnected through a passive transmission and distribution(T&D)grid,by adopting the port-hamiltonian(ph)systems theory and the fundamental circuit theory.The models of generic T&D lines are developed and then the model of a generic T&D grid is established.With the proposed control framework,the controlled converters are proven to be passive and Input-to-State Stable(ISS).The compact mathematical model is scalable and can be applied to power systems with multiple power electronic converters with generic passive controllers,passive local loads,and different types of passive T&D lines connected in a meshed configuration without self-loops,so it is very generic.Moreover,the resulting power system is proven to be ISS as well.The analysis is carried out without assumptions on constant frequency/voltage,constant loads,and/or lossless networks,except the need of passivity for all parts involved,and without using the Clarke/Park transformations or the graph theory.To simplify the presentation,three-phase balanced systems are adopted but the results can be easily adapted for single-phase or unbalanced three-phase systems.

关键词： Input-to-State Stable(ISS) passivity,porthamiltonian(ph)systems Power electronic converters dominated power systems Synchronized and Democratized(SYNDEM)grid architecture

Turning point of organoid transplantation:first-in-human trial of iPSC-derived retinal organoid grafting in patients with retinitis pigmentosa

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Science China(Life Sciences) 2024年第5期67卷 1082-1084页

作者： chang-Jun Zhang Zi-Bing Jin Beijing Institute of Ophthalmology Beijing Tongren HospitalCapital Medical UniversityBeijing 100730China

The discovery of induced pluripotent stem cells(iPSCs)has revolutionized the field of disease research,providing a promising platform for studying various conditions.Over the last decade,significant progress has been made in combining iPSCs with other cutting-edge technologies to investigate disease mechanisms and develop potential treatments.

关键词： conditions patients retinitis

Use of artificial intelligence in the field of pain medicine

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World Journal of Clinical Cases 2024年第2期12卷 236-239页

作者： Min Cheol chang Department of Physical Medicine and Rehabilitation College of MedicineYeungnam UniversityDaegu 705-717South Korea

In this editorial we comment on the article“Potential and limitations of ChatGPT and generative artificial intelligence in medial safety education”published in the recent issue of the World Journal of Clinical Cases.This article described the usefulness of artificial intelligence(AI)in medial safety education.herein,we focus specifically on the use of AI in the field of pain medicine.AI technology has emerged as a powerful tool,and is expected to play an important role in the healthcare sector and significantly contribute to pain medicine as further developments are made.AI may have several applications in pain medicine.First,AI can assist in selecting testing methods to identify causes of pain and improve diagnostic accuracy.Entry of a patient’s symptoms into the algorithm can prompt it to suggest necessary tests and possible diagnoses.Based on the latest medical information and recent research results,AI can support doctors in making accurate diagnoses and setting up an effective treatment plan.Second,AI assists in interpreting medical images.For neural and musculoskeletal disorders,imaging tests are of vital importance.AI can analyze a variety of imaging data,including that from radiography,computed tomography,and magnetic resonance imaging,to identify specific patterns,allowing quick and accurate image interpretation.Third,AI can predict the outcomes of pain treatments,contributing to setting up the optimal treatment plan.By predicting individual patient responses to treatment,AI algorithms can assist doctors in establishing a treatment plan tailored to each patient,further enhancing treatment effectiveness.For efficient utilization of AI in the pain medicine field,it is crucial to enhance the accuracy of AI decision-making by using more medical data,while issues related to the protection of patient personal information and responsibility for AI decisions will have to be addressed.In the future,AI technology is expected to be innovatively applied in the field of pain medicine.The advancement of AI is anticipa

关键词： Artificial intelligence Pain medicine Diagnosis Prediction Image

Chronic venous insufficiency, could it be one of the missing pieces in the puzzle of treating pain?

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World Journal of Clinical Cases 2024年第1期12卷 232-235页

作者： Min Cheol chang Department of Physical Medicine and Rehabilitation Yeungnam University HospitalDaegu 705-717South Korea

Pain is a common complaint among patients seeking medical care.If left un-treated,pain can become chronic,significantly affecting patients’quality of life.An accurate diagnosis of the underlying cause of pain is crucial for effective treatment.Chronic venous insufficiency(CVI)is frequently overlooked by pain physicians.Moreover,many pain physicians lack sufficient knowledge about CVI.CVI is a common condition resulting from malfunctioning or damaged valves in lower limb veins.Symptoms of CVI,ranging from mild to severe,include pain,heaviness,fatigue,itching,swelling,skin color changes,and ulcers in the lower limbs.Recently,it has become more widely known that these symptoms can be attributed to CVI.Even slight or mild CVI can cause related symptoms.Pain physicians primarily consider neuromusculoskeletal disorders when assessing patients with leg pain,and often neglect the possibility of CVI.In clinical practice,when pain physicians encounter patients with unresolved leg pain,they must assess whether the patients exhibit symptoms of CVI and conduct tests to differ-entiate CVI from other potential causes.

关键词： Pain Chronic venous insufficiency Diagnosis Treatment Vein