检索结果-南通市图书馆

Reinforcement learning based adaptive control for uncertain mechanical systems with asymptotic tracking

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第4期34卷 19-28页

作者： Xiang-long Liang Zhi-kai yao yao-wen Ge jian-yong yao School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing210094China College of Automation&College of Artificial Intelligence Nanjing University of Post and TelecommunicationNanjing210023China

This paper mainly focuses on the development of a learning-based controller for a class of uncertain mechanical systems modeled by the Euler-Lagrange formulation.The considered system can depict the behavior of a large class of engineering systems,such as vehicular systems,robot manipulators and satellites.All these systems are often characterized by highly nonlinear characteristics,heavy modeling uncertainties and unknown perturbations,therefore,accurate-model-based nonlinear control approaches become unavailable.Motivated by the challenge,a reinforcement learning(RL)adaptive control methodology based on the actor-critic framework is investigated to compensate the uncertain mechanical dynamics.The approximation inaccuracies caused by RL and the exogenous unknown disturbances are circumvented via a continuous robust integral of the sign of the error(RISE)control approach.Different from a classical RISE control law,a tanh(·)function is utilized instead of a sign(·)function to acquire a more smooth control signal.The developed controller requires very little prior knowledge of the dynamic model,is robust to unknown dynamics and exogenous disturbances,and can achieve asymptotic output tracking.Eventually,co-simulations through ADAMS and MATLAB/Simulink on a three degrees-of-freedom(3-DOF)manipulator and experiments on a real-time electromechanical servo system are performed to verify the performance of the proposed approach.

关键词： Adaptive control Reinforcement learning Uncertain mechanical systems Asymptotic tracking

Synergistic silver-mediated and palladium-catalyzed nondirected olefination of aryl C–H bond: quick access to multi-substituted aryl olefins

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第3期67卷 882-889页

作者： jian yao Lili Shao Xiaohong Huo Xiaoming Wang Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs Frontiers Science Center for Transformative MoleculesSchool of Chemistry and Chemical EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Organometallic Chemistry Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 20032China School of Chemistry and Materials Science Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China

Transition metal-catalyzed olefination of aryl C-H bond is a powerful tool for the synthesis of alkenes. While the Pd-catalyzed oxidative C-H olefination of arenes, also known as Fujiwara-Moritani reaction, has been established as one of the most efficient methods, the substrates are largely limited to terminal olefins with electron-withdrawing group(s). Herein, we report a synergistic silver-mediated and palladium-catalyzed non-directed C-H olefination of arenes with vinyl(pseudo)halides, which offers a complementary strategy to the typical Fujiwara-Moritani reaction. The reactions proceeded well for a variety of halogenated arenes, heteroarenes, and olefin substrates, providing an efficient access to various multi-substituted aryl olefins, including trisubstituted/tetrasubstituted olefins and several complex olefins derived from medicines or natural products. Mechanistic studies indicated a bimetallic Pd/Ag cooperation is operative in the catalysis, i.e., the reaction is initiated by aryl C-H bond cleavage via ligation with phosphine/Ag species, followed by transferring of the aryl moiety to a vinyl palladium intermediate,which is in turn formed by oxidative addition of vinyl(pseudo)halide to a Pd complex. This method enables the synthesis of a wide range of challenging multi-substituted vinyl products from simple arenes(directing-group free) in a streamlined and controllable fashion.

关键词： direct C–H olefination multi-substituted aryl alkenes bimetallic Pd/Ag cooperation C–H functionalization

Uniqueness on Difference Operators of Meromorphic Functions of Infinite Order

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2024年第2期40卷 511-527页

作者： Hui LI ming Liang FANG Xiao yao School of Science China University of Mining and TechnologyBeijing 100083P.R.China Institute of Mathematics Academy of Mathematics and System SciencesChinese Academy of SciencesBeijing 100190P.R.China School of Sciences Hangzhou Dianzi UniversityHangzhou 310012P.R.China School of Mathematical sciences and LPMC Nankai UniversityTianjin 300071P.R.China

We investigate the uniqueness problems of meromorphic functions and their difference operators by using a new method.It is proved that if a non-constant meromorphic function f shares a non-zero constant and ∞ counting multiplicities with its difference operators Δcf(z) and Δ_(c)^(2)f(z), thenΔcf(z)≡Δ_(c)^(2)f(z).In particular,we give a difference analogue of a result of Jank-Mues-Volkmann.Our method has two distinct features:(ⅰ) It converts the relations between functions into the corresponding vectors.This makes it possible to deal with the uniqueness problem by linear algebra and combinatorics.(ⅱ) It circumvents the obstacle of the difference logarithmic derivative lemma for meromorphic functions of infinite order,since this method does not depend on the growth of the functions.Furthermore,the idea in this paper can also be applied to the case for several variables.

关键词： Uniqueness meromorphic functions difference operators infinite order

Sparse Modal Decomposition Method Addressing Underdetermined Vortex-Induced Vibration Reconstruction Problem for Marine Risers

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2024年第2期38卷 285-296页

作者： DU Zun-feng ZHU Hai-ming YU jian-xing State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation School of Civil EngineeringTianjin UniversityTianjin 300350China

When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.

关键词： motion reconstruction vortex-induced vibration(VIV) marine riser modal decomposition method compressed sensing

Danhongqing formula alleviates cholestatic liver fibrosis by downregulating long non-coding RNA H19 derived from cholangiocytes and inhibiting hepatic stellate cell activation

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Medicine 2024年第2期22卷 188-198页

作者： Meng Li Yang Zhou Hui Zhu Lie-ming Xu jian Ping Institute of Liver Diseases Shuguang HospitalShanghai University of Traditional Chinese MedicineShanghai 201203China Preventive Treatment Center Yueyang Hospital of Integrated Traditional Chinese and Western MedicineShanghai University of Traditional Chinese MedicineShanghai 200437 China Department of Gastroenterology Suzhou Traditional Chinese Medicine HospitalSuzhou 215000Jiangsu ProvinceChina Shanghai Key Laboratory of Traditional Chinese Medicine Shanghai 201203China Key Laboratory of Liver and Kidney Diseases(Ministry of Education) Shanghai 201203China

Objective:This study explores the mechanism of action of Danhongqing formula(DHQ),a compoundbased Chinese medicine formula,in the treatment of cholestatic liver fibrosis.Methods:In vivo experiments were conducted using 8-week-old multidrug resistance protein 2 knockout(Mdr2-/-)mice as an animal model of cholestatic liver fibrosis.DHQ was administered orally for 8 weeks,and its impact on cholestatic liver fibrosis was evaluated by assessing liver function,liver histopathology,and the expression of liver fibrosis-related proteins.Real-time polymerase chain reaction,Western blot,immunohistochemistry and other methods were used to observe the effects of DHQ on long non-coding RNA H19(H19)and signal transducer and activator of transcription 3(STAT3)phosphorylation in the liver tissue of Mdr2-/-mice.In addition,cholangiocytes and hepatic stellate cells(HSCs)were cultured in vitro to measure the effects of bile acids on cholangiocyte injury and H19 expression.Cholangiocytes overexpressing H19 were constructed,and a conditioned medium containing H19 was collected to measure its effects on STAT3 protein expression and cell activation.The intervention effect of DHQ on these processes was also investigated.HSCs overexpressing H19 were constructed to measure the impact of H19 on cell activation and assess the intervention effect of DHQ.Results:DHQ alleviated liver injury,ductular reaction,and fibrosis in Mdr2-/-mice,and inhibited H19expression,STAT3 expression and STAT3 phosphorylation.This formula also reduced hydrophobic bile acid-induced cholangiocyte injury and the upregulation of H19,inhibited the activation of HSCs induced by cholangiocyte-derived conditioned medium,and decreased the expression of activation markers in HSCs.The overexpression of H19 in a human HSC line confirmed that H19 promoted STAT3 phosphorylation and HSC activation,and DHQ was able to successfully inhibit these effects.Conclusion:DHQ effectively alleviated spontaneous cholestatic liver fibrosis in Mdr2-/-mice by inhibiting H19 upregulation in chol

关键词： Liver cirrhosis biliary Long non-coding RNA H19 Danhongqing formula Cholangiocyte Hepatic stellate cells STAT3 transcription factor

Skin Microbiota and the Skin Barrier

在线全文

学校读者我要写书评

暂无评论

International Journal of Dermatology And Venereology 2024年第1期07卷 18-26页

作者： Wu ming-Yang yao Xu Department of Allergy and Rheumatology jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs Hospital for Skin Diseases (Institute of Dermatology) Chinese Academy of Medical Sciences and Peking Union Medical College Nanjing jiangsu 210042 China

The skin constitutes the primary barrier between the human body and the external environment. The skin microbiome plays an important role in the microecosystem on the skin surface and mediates multiple facets of the skin barrier function, including physical, chemical, microbial, and immune barriers. In this review, we discuss the host–microbiota interactions in barrier maintenance and disruption, implications for skin disorders such as atopic dermatitis, psoriasis, and rosacea, and the latest strategies for targeting the skin microbiota to improve the skin barrier.

关键词： skin barrier microbiota immune atopic dermatitis Staphylococcus aureus

A symmetric substructuring method for analyzing the natural frequenciesof conical origami structures

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Theoretical & Applied Mechanics Letters 2024年第3期14卷 203-210页

作者： Chenhao Lu yao Chen Weiying Fan jian Feng Pooya Sareh Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education and National Prestress Engineering Research CenterSoutheast UniversityNanjing 211189China School of Engineering University of LiverpoolLiverpool L693BXUnited Kingdom Creative Design Engineering Lab(Cdel) School of EngineeringNewcastle UniversityNewcastle upon Tyne NE17RUUnited Kingdom Escuela Técnica Superior de Ingeniería y Diseño Industrial Universidad Politécnica de Madrid(UPM)Madrid 28012Spain

Conical origami structures are characterized by their substantial out-of-plane stiffness and energy-absorptioncapacity.Previous investigations have commonly focused on the static characteristics of these lightweight struc-tures.However,the efficient analysis of the natural vibrations of these structures is pivotal for designing conicalorigami structures with programmable stiffness and mass.In this paper,we propose a novel method to analyzethe natural vibrations of such structures by combining a symmetric substructuring method(SSM)and a gener-alized eigenvalue analysis.SSM exploits the inherent symmetry of the structure to decompose it into a finiteset of repetitive substructures.In doing so,we reduce the dimensions of matrices and improve computationalefficiency by adopting the stiffness and mass matrices of the substructures in the generalized eigenvalue analysis.Finite element simulations of pin-jointed models are used to validate the computational results of the proposedapproach.Moreover,the parametric analysis of the structures demonstrates the influences of the number of seg-ments along the circumference and the radius of the cone on the structural mass and natural frequencies of thestructures.Furthermore,we present a comparison between six-fold and four-fold conical origami structures anddiscuss the influence of various geometric parameters on their natural frequencies.This study provides a strategyfor efficiently analyzing the natural vibration of symmetric origami structures and has the potential to contributeto the efficient design and customization of origami metastructures with programmable stiffness.

关键词： Natural structural vibration Origami design Group theory Symmetric substructuring method(SSM) Generalized eigenvalue analysis

Synergistic integration of self-supported 1T/2H-WS_(2) and nitrogendoped rGO on carbon cloth for pH-universal electrocatalytic hydrogen evolution

在线全文

学校读者我要写书评

暂无评论

Nano Research 2024年第3期17卷 1267-1280页

作者： Feng ming Yap jian Yiing Loh Wee-Jun Ong School of Energy and Chemical Engineering Xiamen University MalaysiaSelangor Darul Ehsan 43900Malaysia Center of Excellence for NaNo Energy&Catalysis Technology(CONNECT) Xiamen University MalaysiaSelangor Darul Ehsan 43900Malaysia State Key Laboratory of Physical Chemistry of Solid Surfaces College of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China Gulei Innovation Institute Xiamen UniversityZhangzhou 363200China Shenzhen Research Institute of Xiamen University Shenzhen 518057China

Hydrogen economy based on electrochemical water splitting exemplified one of the most promising means for overcoming the rapid consumption of fossil fuels and the serious deterioration of global climate.The development of earth-abundant,efficient,and durable electrocatalysts for hydrogen evolution reaction(HER)plays a vital role in the commercialization of water electrolysis.Regard,the self-supported electrode with unique nitrogen-doped reduced graphene oxide(N-rGO)nanoflakes and WS_(2) hierarchical nanoflower that were grown directly on carbon cloth(CC)substrate(WS_(2)/N-rGO/CC)was successfully synthesized using a facile dual-step hydrothermal approach.The as-synthesized 50%1T/2H-WS_(2)/N-rGO/CC(WGC),which possessed high metallic 1T phase of 57%not only efficiently exposed more active sites and accelerated mass/charge diffusion,but also endowed excellent structural lustiness,robust stability,and durability at a high current density.As a result,the 50%WGC exhibited lower overpotentials and Tafel slopes of 21.13 mV(29.55 mV∙dec^(-1))and 80.35 mV(137.02 mV∙dec^(-1))as compared to 20%Pt-C/CC,respectively for catalyzing acidic and alkaline hydrogen evolution reactions.Pivotally,the as-synthesized 50%WGC also depicted long-term stability for more than 8 h in the high-current-density regions(100 and 220 mA∙cm^(-2)).In brief,this work reveals a self-supported electrode as an extraordinary alternative to Pt-based catalysts for HER in a wide pH range,while paving a facile strategy to develop advanced electrocatalysts with abundant heterointerfaces for practical applications in energy-saving hydrogen production.

关键词： self-supported electrocatalyst carbon-based substrate phase engineering pH-universal water splitting

Variability Analysis for a Two-station Queueing Network in Heavy Traffic with Arrival Processes Driven by Queues

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2024年第2期40卷 445-466页

作者： jian CAO Yong-jiang GUO Kai-ming YANG School of Science Beijing University of Posts and TelecommunicationsBeijing 100876China

The law of the iterated logarithm(LIL)for the performance measures of a two-station queueing network with arrivals modulated by independent queues is developed by a strong approximation method.For convenience,two arrival processes modulated by queues comprise the external system,all others are belong to the internal system.It is well known that the exogenous arrival has a great influence on the asymptotic variability of performance measures in queues.For the considered queueing network in heavy traffic,we get all the LILs for the queue length,workload,busy time,idle time and departure processes,and present them by some simple functions of the primitive data.The LILs tell us some interesting insights,such as,the LILs of busy and idle times are zero and they reflect a small variability around their fluid approximations,the LIL of departure has nothing to do with the arrival process,both of the two phenomena well explain the service station’s situation of being busy all the time.The external system shows us a distinguishing effect on the performance measures:an underloaded(overloaded,critically loaded)external system affects the internal system through its arrival(departure,arrival and departure together).In addition,we also get the strong approximation of the network as an auxiliary result.

关键词： two-station queueing network the law of the iterated logarithm(LIL) strong approximation fluid approximation