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Hierarchical Control Strategy for Load Regulation Based on Stackelberg Game Theory Considering Randomness

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 929-941页

作者： Tingyu Jiang Ping Ju C.y.Chung yuzhong Gong College of Energy and Electrical Engineering Hohai UniversityNanjing 211100China Department of Electrical Engineering City University of Hong KongHong Kong CF624China Department of Electrical and Computer Engineering University of SaskatchewanSaskatoonSK S7N 5A9Canada CSEE IEEE

Demand response has been recognized as a valuable functionality of power systems for mitigating power *** paper proposes a hierarchical control strategy among the distribution system operator(DSO),load aggregators(LAs),and thermostatically controlled loads(TCLs);the strategy includes a scheduling layer and an executive layer to provide load *** the scheduling layer,the DSO(leader)offers compensation price(CP)strategies,and the LAs(followers)respond to CP strategies with available regulation power(ARP)*** of the DSO and LAs are modeled according to their behaviors during the load regulation *** game is adopted to capture interactions among the players and leader and to obtain the optimal strategy for each participant to achieve ***,considering inevitable random factors in practice,e.g.,renewable generation and behavior of users,two different stochastic models based on sample average approximation(SAA)and parameter modification are formulated with improved scheduling *** the executive layer,distributed TCLs are triggered based on strategies determined in the scheduling layer.A self-triggering method that does not violate user privacy is presented,where TCLs receive external signals from the LA and independently determine whether to alter their operation *** simulations are performed on the modified IEEE-24 bus system to verify effectiveness of the proposed strategy.

关键词： Demand response hierarchical control load regulation self-triggering method Stackelberg game

Data-driven Static Equivalence with Physics-informed Koopman Operators

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 432-438页

作者： Wei Lin Changhong Zhao Maosheng Gao C.y.Chung Department of Electrical Engineering The Hong Kong Polytechnic UniversityHong Kong SARChina Department of Information Engineering The Chinese University of Hong KongHong Kong SARChina School of Electrical Engineering Chongqing UniversityChongqing 400044China

With deployment of measurement units,fitting static equivalent models of distribution networks(DNs)by linear regression has been recognized as an effective method in power flow analysis of a transmission *** volatility of measurements caused by variable distributed renewable energy sources makes it more difficult to accurately fit such equivalent *** tackle this challenge,this letter proposes a novel data-driven method to improve equivalency accuracy of DNs with distributed energy *** letter provides a new perspective that an equivalent model can be regarded as a mapping from internal conditions and border voltages to border power *** mapping can be established through 1)Koopman operator theory,and 2)physical features of power flow equations at the root node of a *** of the proposed method is demonstrated on the IEEE 33-bus and IEEE 136-bus test systems connected to a 661-bus utility system.

关键词： Data-driven distribution network Koopman operator theory static equivalent model

Deep bed filtration model for cake filtration and erosion

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Applied Mathematics and Mechanics(English Edition) 2024年第2期45卷 355-372页

作者： L.I.KUZMINA y.V.OSIPOV A.R.PESTEREV Department of Applied Mathematics HSE UniversityMoscow 101000Russia Department of Computer Science and Applied Mathematics Moscow State University of Civil EngineeringMoscow 129337Russia

Many phenomena in nature and technology are associated with the filtration of suspensions and colloids in porous media. Two main types of particle deposition,namely, cake filtration at the inlet and deep bed filtration throughout the entire porous medium, are studied by different models. A unified approach for the transport and deposition of particles based on the deep bed filtration model is proposed. A variable suspension flow rate, proportional to the number of free pores at the inlet of the porous medium, is considered. To model cake filtration, this flow rate is introduced into the mass balance equation of deep bed filtration. For the cake filtration without deposit erosion,the suspension flow rate decreases to zero, and the suspension does not penetrate deep into the porous medium. In the case of the cake filtration with erosion, the suspension flow rate is nonzero, and the deposit is distributed throughout the entire porous medium. An exact solution is obtained for a constant filtration function. The method of characteristics is used to construct the asymptotics of the concentration front of suspended and retained particles for a filtration function in a general form. Explicit formulae are obtained for a linear filtration function. The properties of these solutions are studied in detail.

关键词： deep bed filtration cake filtration porous medium particle deposition and erosion analytical solution concentration front

Thermo-kinetic characteristics on stabilizing hetero-phase interface of metal matrix composites by crystal plasticity finite element method

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Journal of Materials Science & Technology 2024年第2期169卷 53-67页

作者： y.B.Zhang S.J.Song F.Liu State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Analytical&Testing Center Northwestern Polytechnical UniversityXi’an 710072China

Using dislocation-based constitutive modeling in three-dimension crystal plasticity finite element(3D CPFE)simulations,co-deformation and instability of hetero-phase interface in different material systems were herein studied for polycrystalline metal matrix composites(MMCs).Local stress and strain fields in two types of 3layer MMCs such as fcc/fcc Cu-Ag and fcc/bcc Cu-Nb have been predicted under simple compressive ***,more severe strain-induced interface instability can be observed in the fcc/bcc systems than in the fcc/fcc systems upon refining to metallic nanolayered composites(MNCs).By detailed analysis of stress and strain localization,it has been demonstrated that the interface instability is always accompanied by high-stress concentration,i.e.,thermodynamic characteristics,or high strain prevention i.e.,kinetic characteristics,at the hetero-phase *** then follows that the thermodynamic driving forceG and the kinetic energy barrier Q during dislocation and shear banding can be adopted to classify the deformation modes,following the so-called thermo-kinetic *** by inserting a high density of high-energy interfaces into the Cu-Nb composites,such thermo-kinetic integration at the hetero-phase interface allows a successful establishment of MMCs with the high△G-high Q deformation mode,which ensures high hardening and uniform strain distri-bution,thus efficiently suppressing the shear band,stabilizing the hetero-phase interface,and obtaining an exceptional combination in strength and *** hetero-phase interface chosen by a couple of thermodynamics and kinetics can be defined as breaking the thermo-kinetic correlation and has been proposed for artificially designing MNCs.

关键词： Thermodynamics and kinetics Physics-based constitutive modeling Hetero-phase interface Crystal plasticity finite element

Optimization of chemistry and process parameters for control of intermetallic formation in Mg sludges

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Journal of Magnesium and Alloys 2024年第4期12卷 1431-1448页

作者： y.Fu G.G.Wang A.Hu y.Li K.B.Thacker J.P.Weiler H.Hu Department of Mechanical Automotive and Materials EngineeringUniversity of Windsor401 Sunset AveWindsorOntario N9B 3P4Canada Global Technology Centre Meridian Lightweight Technologies25 MacNab AveStrathroyOntario N7G 4H6Canada

Intermetallic formation in sludge during magnesium(Mg)melting,holding and high pressure die casting practices is a very important ***,very often it is overlooked by academia,original equipment manufacturers(OEM),metal ingot producers and even die *** aim of this study was to minimize the intermetallic formation in Mg sludge via the optimization of the chemistry and process *** Al8Mn5 intermetallic particles were identified by the microstructure analysis based on the Al and Mn *** design of experiment(DOE)technique,Taguchi method,was employed to minimize the intermetallic formation in the sludge of Mg alloys with various chemical compositions of Al,Mn,Fe,and different process parameters,holding temperature and holding *** sludge yield(Sy)and intermetallic size(IS)was selected as two *** optimum combination of the levels in terms of minimizing the intermetallic formation were 9 wt.%Al,0.15 wt.%Mn,0.001 wt.%(10 ppm)Fe,690℃ for the holding temperature and holding at 30 mins for the holding time,*** best combination for smallest intermetallic size were 9 wt.%Al,0.15 wt.%Mn,0.001 wt.%(10 ppm)Fe,630℃ for the holding temperature and holding at 60 mins for the holding time,*** groups of sludge factors,Chemical Sludge(CSF),Physical Sludge(PSF)and Comprehensive Sludge Factors(and CPSF)were established for prediction of sludge yields and intermetallic sizes in Al-containing Mg *** CPSF with five independent variables including both chemical elements and process parameters gave high accuracy in prediction,as the prediction of the PSF with only the two processing parameters of the melt holding temperature and time showed a relatively large deviation from the experimental *** Chemical Sludge Factor was primarily designed for small ingot producers and die casters with a limited melting and holding capacity,of which process parameters could be fixed *** Physical Sludge Factor could be used f

关键词： Magnesium sludge Al-Mn intermetallic Optimization Taguchi method Sludge factor Chemical composition Process parameter

Mechanisms behind the environmental sensitivity of carbon fiber reinforced polytetrafluoroethylene(PTFE)

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Friction 2024年第5期12卷 997-1015页

作者： Pontus JOHANSSON P.MARKLUND M.BJORLING y.SHI Division of Machine Element LuleåUniversity of TechnologyLuleåSE-97187Sweden

Carbon fiber reinforced polytetrafluoroethylene (CF/PTFE) composites are known for their exceptional tribological performance when sliding against steel or cast iron in inert gas environments. Compared to experiments in humid air, about an order of magnitude lower wear rate and several times lower coefficient of friction have been reported for tests conducted in dry nitrogen and hydrogen. Moreover, trace moisture has been shown to affect the friction and wear significantly of this tribosystem, although a possible effect of oxygen cannot be ruled out due to uncertainties regarding the oxygen concentrations. While several studies have pointed out the environmental sensitivity of CF/PTFE, the understanding of the underlying mechanisms are very limited. The objective of this research is to investigate the individual and combined effect of oxygen and moisture on the tribological behavior of CF/PTFE sliding against steel. Additionally, this study aims to elucidate the underlying mechanisms that govern the environmental sensitivity of the system. Climate-controlled three-pin-on-disc experiments were conducted in nitrogen atmospheres at various concentrations of oxygen and moisture. The tribological results clearly demonstrate that both moisture and oxygen contribute to increased friction and wear. However, the adverse effect was much more pronounced for oxygen than moisture. A qualitative method was developed to estimate the tribofilm coverage on the CF/PTFE surface. Results showed strong correlation between high coverage of strongly adhered tribofilm and low wear rate. Moreover, a loosely adhered tribofilm was observed on top of the CF/PTFE surface in presence of moisture. FTIR analysis indicated that the loosely adhered tribofilm found in the moisture-enriched environment contained a significant amount of adsorbed water, which may explain the lower coefficient of friction in presence of moisture compared to oxygen. The adsorbed water in the loosely adhered tribofilm coul

关键词： polymer composite tribofilm tribochemistry atmosphere

Focal Nodular Hyperplasia: A Comprehensive Review with a Particular Focus on Pathogenesis and Complications

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Journal of Clinical and Translational Hepatology 2024年第2期12卷 182-190页

作者： Jaimy Villavicencio Kim George y.Wu Division of Gastroenterology-Hepatology University of Connecticut Health CenterFarmingtonCTUSA

Focal nodular hyperplasia is a benign tumor of the liver that is often found incidentally with *** purpose of this review is to discuss the pathophysiology,rare complications that can occur due to these lesions,and management options.A literature review was performed on clinical trials and case reports involving focal nodular hyperplasia complications and management of these,as well as the proposed pathogenesis underlying these *** exposure to oral contraceptive pills and endogenous hormones have been thought to play a role in the development of these lesions,this has not been *** recently,they are thought to arise as a consequence of a vascular anomaly causing alterations in the expression of angiopoietin *** are rare,but previous cases have reported associated pain,rupture and compression of nearby structures(hepatic vein,stomach,biliary system).Resection of focal nodular hyperplasia is not usually ***,if there is associated pain with no other identifiable cause or presence of a large or growing lesion with risk of causing a complication,then surgical resection,radiofrequency ablation or arterial embolization should be considered.

关键词： Focal nodular hyperplasia Oral contraceptives Liver lesion

Evaluation of Industrial IoT Service Providers with TOPSIS Based on Circular Intuitionistic Fuzzy Sets

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Computers, Materials & Continua 2024年第7期80卷 715-746页

作者： Elif Çalo˘glu Büyükselçuk Industrial Engineering Department Fenerbahçe University˙Istanbul34758Turkey

Industrial Internet of Things(IIoT)service providers have become increasingly important in the manufacturing industry due to their ability to gather and process vast amounts of data from connected devices,enabling manufacturers to improve operational efficiency,reduce costs,and enhance product *** platforms provide manufacturers with real-time visibility into their production processes and supply chains,allowing them to optimize operations and make informed *** addition,IIoT service providers can help manufacturers create new revenue streams through the development of innovative products and services and enable them to leverage the benefits of emerging technologies such as Artificial Intelligence(AI)and machine ***,the implementation of IIoT platforms in the manufacturing industry is crucial for companies seeking to remain competitive and meet the ever-increasing demands of customers in the digital *** this study,the evaluation criteria to be considered in the selection of IIoT service provider in small andmedium-sized(SME)manufacturing enterprises will be determined and IIoT service providers alternatives will be evaluated using the technique for order preference by similarity to an ideal solution(TOPSIS)method based on circular intuitionistic fuzzy *** on the assessments conducted in accordance with the literature review and expert consultations,a set of 8 selection criteria has been *** criteria encompass industry expertise,customer support,flexibility and scalability,security,cost-effectiveness,reliability,data analytics,as well as compatibility and *** evaluating these criteria,it was observed that the security criterion holds the highest significance,succeeded by cost-effectiveness,data analytics,flexibility and scalability,reliability,and customer support criteria,in descending order of *** the evaluation of seven distinct alternatives against these criteria,it was deduced tha

关键词： IIoT manufacturing TOPSIS circular intuitionistic fuzzy sets

Exponentially Convergent Multiscale Finite Element Method

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Communications on Applied Mathematics and Computation 2024年第2期6卷 862-878页

作者： yifan Chen Thomas y.Hou yixuan Wang Applied and Computational Mathematics CaltechPasadena 91106USA

We provide a concise review of the exponentially convergent multiscale finite element method(ExpMsFEM)for efficient model reduction of PDEs in heterogeneous media without scale separation and in high-frequency wave *** ExpMsFEM is built on the non-overlapped domain decomposition in the classical MsFEM while enriching the approximation space systematically to achieve a nearly exponential convergence rate regarding the number of basis *** most generalizations of the MsFEM in the literature,the ExpMsFEM does not rely on any partition of unity *** general,it is necessary to use function representations dependent on the right-hand side to break the algebraic Kolmogorov n-width barrier to achieve exponential ***,there are online and offline parts in the function representation provided by the *** online part depends on the right-hand side locally and can be computed in parallel *** offline part contains basis functions that are used in the Galerkin method to assemble the stiffness matrix;they are all independent of the right-hand side,so the stiffness matrix can be used repeatedly in multi-query scenarios.

关键词： Multiscale method Exponential convergence Helmholtz's equation Domain decomposition Nonlinear model reduction