检索结果-南通市图书馆

Particle Distribution Informed by Chain Rigidity in Diblock Copolymer Melts: The Effect of Entropy

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第3期42卷 388-399,I0009页

作者： Yuguo Chen Shuanhu Qi ying jiang School of Chemistry Beihang UniversityBeijing 100191China

We study the effect of chain rigidity on tailoring the nanoparticle locations for neutral and selective particles embedded in the lamellar morphology formed by semiflexible diblock copolymer chains using self-consistent field calculations. The nanoparticles are modeled through a cavity function, and the semiflexible chains are represented by the continuous Kratsky-Porod chain model. In general situation, the nanoparticles prefer to stay at the interface in order to reduce the interface areas and thus the system free energy. However, the particle distribution at the domain center is subtle, and the underlying physics is intrinsically different depending on the polymer flexibility. In the case of flexible chains, the entropy just contributes a constant shift to the free energy when the nanoparticles move around the domain center indicating that the local metastable state if appears at the domain center is wholly attributed to the local minimum in the enthalpy. If the polymers are rigid, the variation of the particle distribution at the domain center has a close relation with the polymer rigidity and nanoparticle size. In the case of strongly rigid polymers with small nanoparticles, a nearly uniform particle distribution at the domain center is observed, while in other cases, a local enhancement of particle distribution there is found. In contrast to the case of flexible chains, further analysis reveals the crucial role of entropy in controlling the shape of particle distributions at the phase domain. Specifically, the local metastable state appears in the domain center is determined by the large entropy there which arises from the weak coupling of bond orientations that allows the polymer chains to be relatively relaxed. When the particle becomes selective, its distribution in the phase domain exhibits a shift almost uniformly rather than changes its profile, and the underlying physics still holds. In all, our study establishes a strong coupling between the chain rigi

关键词： Semiflexible diblock copolymer Nanoparticle distribution Self-consistent field theory Entropic effect

Ultrafast optical investigation of carrier and spin dynamics in low-dimensional perovskites

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2024年第1期67卷 2-18页

作者： FU JinYue jiang ying FANG HongHua Key Laboratory for Micro-Nano Physics and Technology of Hunan Province School of Physics and ElectronicsHunan UniversityChangsha 410012China State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentTsinghua UniversityBeijing 100084China

Low-dimensional perovskite(PVK)materials have attracted significant research interest,because of their quantum-confined effect,tunable band gap structures,and higher stability than that of three-dimensional(3D)*** semiconductor optoelectronic devices,high speed and small size are closely *** development of high-speed devices requires researchers to fully understand the properties of materials,especially the dynamic processes such as carrier recombination,separation,and transport,which often play a crucial role in the performance of *** an indispensable part of dynamic research,spin relaxation is also of great significance in studying the properties of materials and explore possible *** halide PVK materials have strong spin-orbit coupling(SOC),which provides a basis for information storage and processing by using spin degrees of ***,studying the carrier and spin dynamics of low-dimensional PVKs is an effective way to understand the internal properties of low-dimensional PVKs *** paper summarizes the latest research progress on the ultrafast carrier and spin dynamics in low-dimensional PVKs,to comprehensively understand their carrier and spin behaviors and present an outlook for relevant studies in this area.

关键词： low-dimensional perovskites carrier dynamics spin dynamics optoelectronic devices

Heterointerface engineering of rhombic Rh nanosheets confined on MXene for efficient methanol oxidation

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2024年第6期93卷 419-428,I0011页

作者： Qi Zhang Quanguo jiang Xiang Yang Chi Zhang jian Zhang Lu Yang Haiyan He Guobing ying Huajie Huang College of Materials Science and Engineering Hohai UniversityNanjing 210098JiangsuChina New Energy Technology Engineering Lab of jiangsu Province College of ScienceNanjing University of Posts&Telecommunications(NUPT)Nanjing 210023JiangsuChina School of Materials Science and Engineering Southeast UniversityNanjing 211100JiangsuChina

Although metallic rhodium(Rh)is regarded as a promising platinum-alternative anode catalyst of direct methanol fuel cell(DMFC),the conventional"particle-to-face"contact model between Rh and matrix largely limits the overall electrocatalytic performance due to their insufficient cooperative ***,we report a controllable and robust heterointerface engineering strategy for the bottom-up fabrication of rhombic Rh nanosheets in situ confined on Ti_3C_(2)T_x MXene nanolamellas(Rh NS/MXene)via a convenient stereoassembly *** unique design concept gives the resulting 2D/2D Rh NS/MXene heterostructure intriguing textural features,including large accessible surface areas,strong"face-toface"interfacial interactions,homogeneous Rh nanosheet distribution,ameliorative electronic structure,and high electronic *** a consequence,the as-prepared Rh NS/MXene nanoarchitectures exhibit exceptional electrocatalytic methanol oxidation properties in terms of a large electrochemically active surface area of 126.2 m~2 g_(Rh)~(-1),a high mass activity of 1056.9 mA mg_(Rh)-~1,and a long service life,which significantly outperform those of conventional particle-shaped Rh catalysts supported by carbon black,carbon nanotubes,reduced graphene oxide,and MXene matrixes as well as the commercial Pt nanoparticle/carbon black and Pd nanoparticle/carbon black catalysts with the same noble metal loading *** functional theory calculations further demonstrate that the direct electronic interaction at the well-contacted 2D/2D heterointerfaces effectively enhances the adsorption energy of Rh nanosheets and induces a left shift of the d-band center,thereby making the Rh NS/MXene configuration suffer less from CO *** work highlights the importance of rational heterointerface design in the construction of advanced noble metal/MXene electrocatalysts,which may provide new avenues for developing the next-generation DMFC devices.

关键词： Rhodium nanosheet Ti_(3)C_(2)T_(x)MXene Heterointerface Electrocatalyst Fuel cell

Physical neural networks with self-learning capabilities

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2024年第8期67卷 23-42页

作者： Weichao Yu Hangwen Guo jiang Xiao jian Shen State Key Laboratory of Surface Physics and Institute for Nanoelectronic Devices and Quantum Computing Fudan UniversityShanghai 200433China Zhangjiang Fudan International Innovation Center Fudan UniversityShanghai 201210China Department of Physics Fudan UniversityShanghai 200433China Shanghai Research Center for Quantum Sciences Shanghai 201315China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093China

Physical neural networks are artificial neural networks that mimic synapses and neurons using physical systems or *** networks harness the distinctive characteristics of physical systems to carry out computations effectively,potentially surpassing the constraints of conventional digital neural networks.A recent advancement known as“physical self-learning”aims to achieve learning through intrinsic physical processes rather than relying on external *** article offers a comprehensive review of the progress made in implementing physical self-learning across various physical *** learning strategies that contribute to the realization of physical self-learning are *** challenges in understanding the fundamental mechanism of learning,this work highlights the progress towards constructing intelligent hardware from the ground up,incorporating embedded self-organizing and self-adaptive dynamics in physical systems.

关键词： self-learning physical neural networks neuromorphic computing physical learning

同方期刊数据库

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

在线全文

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 *** convenience,two arrival processes modulated by queues comprise the external system,all others are belong to the internal *** is well known that the exogenous arrival has a great influence on the asymptotic variability of performance measures in *** 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 *** 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 *** 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

Relaxed Stability Criteria for Time-Delay Systems:A Novel Quadratic Function Convex Approximation Approach

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 996-1006页

作者： Shenquan Wang Wenchengyu Ji Yulian jiang Yanzheng Zhu jian Sun College of Electrical and Electronic Engineering Changchun University of TechnologyChangchun 130012China the College of Electrical Engineering and Automation Shandong University of Science and TechnologyQingdao 266590China Key Laboratory of Complex Systems Intelligent Control and Decision Beijing Institute of TechnologyBeijing 100081China

This paper develops a quadratic function convex approximation approach to deal with the negative definite problem of the quadratic function induced by stability analysis of linear systems with time-varying *** introducing two adjustable parameters and two free variables,a novel convex function greater than or equal to the quadratic function is constructed,regardless of the sign of the coefficient in the quadratic *** developed lemma can also be degenerated into the existing quadratic function negative-determination(QFND)lemma and relaxed QFND lemma respectively,by setting two adjustable parameters and two free variables as some particular ***,for a linear system with time-varying delays,a relaxed stability criterion is established via our developed lemma,together with the quivalent reciprocal combination technique and the Bessel-Legendre *** a result,the conservatism can be reduced via the proposed approach in the context of constructing Lyapunov-Krasovskii functionals for the stability analysis of linear time-varying delay ***,the superiority of our results is illustrated through three numerical examples.

关键词： Equivalent reciprocal combination technique quadratic function convex approximation approach stability timevarying delay

Echo State Network Based on Improved Knowledge Distillation for Edge Intelligence

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2024年第1期33卷 101-111页

作者： jian ZHOU Yuwen jiang Lijie XU Lu ZHAO Fu XIAO College of Computer Nanjing University of Posts and Telecommunications jiangsu High Technology Research Key Laboratory for Wireless Sensor Networks

Echo state network(ESN) as a novel artificial neural network has drawn much attention from time series prediction in edge intelligence. ESN is slightly insufficient in long-term memory, thereby impacting the prediction performance. It suffers from a higher computational overhead when deploying on edge devices. We firstly introduce the knowledge distillation into the reservoir structure optimization, and then propose the echo state network based on improved knowledge distillation(ESN-IKD) for edge intelligence to improve the prediction performance and reduce the computational overhead. The model of ESN-IKD is constructed with the classic ESN as a student network, the long and short-term memory network as a teacher network, and the ESN with double loop reservoir structure as an assistant network. The student network learns the long-term memory capability of the teacher network with the help of the assistant network. The training algorithm of ESN-IKD is proposed to correct the learning direction through the assistant network and eliminate the redundant knowledge through the iterative pruning. It can solve the problems of error learning and redundant learning in the traditional knowledge distillation process. Extensive experimental simulation shows that ESN-IKD has a good time series prediction performance in both long-term and short-term memory, and achieves a lower computational overhead.

关键词： Knowledge engineering Training Performance evaluation Computational modeling Time series analysis Artificial neural networks Reservoirs

同方期刊数据库

MXene Key Composites:A New Arena for Gas Sensors

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2024年第10期16卷 350-391页

作者： Yitong Wang Yuhua Wang Min jian Qinting jiang Xifei Li Hubei Province Key Laboratory of Systems Science in Metallurgical Process Wuhan University of Science and TechnologyWuhan 430081People's Republic of China Key Materials and Components of Electrical Vehicles for Overseas Expertise Introduction Center for Discipline Innovation Institute of Advanced Electrochemical Energy and School of Materials Science and EngineeringXi'an University of TechnologyXi'an 710048People's Republic of China College of Materials Science and Engineering Fuzhou UniversityFuzhou 350108FujianPeople's Republic of China

With the development of science and technology,the scale of industrial production continues to grow,and the types and quantities of gas raw materials used in industrial production and produced during the production process are also constantly *** gases include flammable and explosive gases,and even contain toxic ***,it is very important and necessary for gas sensors to detect and monitor these gases quickly and *** recent years,a new two-dimensional material called MXene has attracted widespread attention in various *** abundant surface functional groups and sites,excellent current conductivity,tunable surface chemistry,and outstanding stability make them promising for gas sensor *** the birth of MXene materials,researchers have utilized the efficient and convenient solution etching preparation,high flexibility,and easily functionalize MXene with other materials to pre-pare composites for gas *** has opened a new chapter in high-performance gas sensing materials and provided a new approach for advanced sensor ***,previous reviews on MXene-based composite materials in gas sensing only focused on the performance of gas sensing,without systematically explaining the gas sensing mechanisms generated by different gases,as well as summarizing and predicting the advantages and disadvantages of MXene-based composite *** article reviews the latest progress in the application of MXene-based composite materials in gas ***,a brief summary was given of the commonly used methods for preparing gas sens-ing device structures,followed by an introduction to the key attributes of MXene related to gas sensing *** article focuses on the performance of MXene-based composite materials used for gas sensing,such as MXene/graphene,MXene/Metal oxide,MXene/Transition metal sulfides(TMDs),MXene/Metal-organic framework(MOF),MXene/*** summarizes the advantages and disad

关键词： MXene Compound material Gas sensor Gas sensitive preparation Gas sensitivity performance

Fatigue Crack Propagation Law of Corroded Steel Box Girders in Long Span Bridges

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2024年第7期140卷 201-227页

作者： ying Wang Longxiao Chao Jun Chen Songbai jiang Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education School of Civil EngineeringSoutheast UniversityNanjing211189China jiangsu Provincial Engineering Construction Standard Station Nanjing210036China

In order to investigate the fatigue performance of orthotropic anisotropic steel bridge decks,this study realizes the simulation of the welding process through elastic-plastic finite element theory,thermal-structural sequential coupling,and the birth-death element *** simulated welding residual stresses are introduced into the multiscale finite element model of the bridge as the initial ***,the study explores the impact of residual stress on crack propagation in the fatigue-vulnerable components of the corroded steel box *** results indicate that fatigue cracks at the weld toe of the top deck,the weld root of the top deck,and the opening of the transverse diaphragm will not propagate under the action of a standard vehicle ***,the inclusion of residual stress leads to the propagation of these *** considering residual stress,the fatigue crack propagation paths at the weld toe of the transverse diaphragm and the U-rib weld toe align with those observed in actual *** the absence of residual stress,the cracks at the toe of the transverse diaphragm with a 15%mass loss rate are categorized as type I ***,when residual stress is considered,these cracks become I-II composite *** stress significantly alters the cumulative energy release rate of the three ***,incorporating the influence of residual stress is essential when assessing the fatigue performance of corroded steel box girders in long-span bridges.

关键词： Residual stress crack propagation corroded steel box girder cumulative energy release rate