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Fast-Converging and Asymptotic-Preserving Simulation of Frequency Domain Thermoreflectance

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Communications in Computational Physics 2023年第6期33卷 65-93页

作者： Jia Liu Lei Wu Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen 518055P.R.China

The heat conduction under fast external excitation exists in many experiments measuring the thermal conductivity in solids,which is described by the phonon Boltzmann equation,i.e.,the Callaway’s model with dual relaxation times.Such a kinetic system has two spatial Knudsen numbers related to the resistive and normal scatterings,and one temporal Knudsen number determined by the external oscillation frequency.Thus,it is a challenge to develop an efficient numerical method.Here we first propose the general synthetic iterative scheme(GSIS)to solve the phonon Boltzmann equation,with the fast-converging and asymptotic-preserving properties:(i)the solution can be found within dozens of iterations for a wide range of Knudsen numbers and frequencies,and(ii)the solution is accurate when the spatial cell size in the bulk region is much larger than the phonon mean free path.Then,we investigate how the heating frequency affects the heat conduction in different transport regimes.

关键词： Frequency domain thermoreflectance phonon Boltzmann equation general synthetic iterative scheme

Recent progress in MOFs-based nanozymes for biosensing

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Nano Research 2024年第1期17卷 39-64页

作者： Imamdin Chandio Yongjian Ai Lei Wu Qionglin Liang MOE Key Laboratory of Bioorganic Phosphorus Chemistry&Chemical Biology Department of ChemistryLaboratory of Flexible Electronics TechnologyCenter for Synthetic and Systems BiologyTsinghua University-Peking University Joint Centre for Life SciencesTsinghua UniversityBeijing 100084China

Nanozymes are nanomaterials with enzyme-mimicking catalytic activity.Compared to natural enzymes,nanozymes show various properties such as easy to manufacture,stable,adjustable,and inexpensive.Nanozymes play key roles in biosensing,biocatalysis,and disease treatment.As an important kind of nanozymes,metal-organic framework(MOF)-based nanozymes are receiving a lot of attention due to their structural properties and composition.Rationally developing MOF with enzymes-like catalytic properties has opened new perspectives in biosensing.This review summarizes the up-to-date developments in synthesizing two-dimensional and three-dimensional MOF-based nanozymes and their applications in biosensing.Firstly,classification of nanozymes obtained by MOFs is categorized,and different properties of MOF-based nanozymes are described.Then,the distinctive applications of MOF-based nanozymes in identifying various analytes are thoroughly summarized.Finally,the recent challenges and progressive directions in this area are highlighted.

关键词： metal-organic frameworks nanozymes metal-organic framework (MOF)-based nanozymes biosensing analytes

Artificial neural network-based one-equation model for simulation of laminar-turbulent transitional flow

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Theoretical & Applied Mechanics Letters 2023年第1期13卷 50-57页

作者： Lei Wu Bing Cui Zuoli Xiao State Key Laboratory for Turbulence and Complex Systems College of EngineeringPeking UniversityBeijing 100871China Inspur Electronic Information Industry Co. LtdBeijing 100085China HEDPS and Center for Applied Physics and Technology College of EngineeringPeking UniversityBeijing 100871China Nanchang Innovation Institute Peking UniversityNanchang 330008China

A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network(ANN),which replaces the governing equation of the intermittency factor in transition-predictive Spalart-Allmaras(SA)-γmodel.By taking SA-γmodel as the benchmark,the present ANN model is trained at two airfoils with various angles of attack,Mach numbers and Reynolds numbers,and tested with unseen airfoils in different flow states.The a posteriori tests manifest that the mean pressure coefficient,skin friction coefficient,size of laminar separation bubble,mean streamwise velocity,Reynolds shear stress and lift/drag/moment coefficient from the present two-way coupling ANN model almost coincide with those from the benchmark SA-γmodel.Furthermore,the ANN model proves to exhibit a higher calculation efficiency and better convergence quality than traditional SA-γmodel.

关键词： Transition Turbulence Eddy-viscosity model Artificial neural network Intermittency factor

Ligand-Controlled Palladium-Catalyzed Regiodivergent Defluorinative Allylation of gem-Difluorocyclopropanes viaσ-Bond Activation

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Chinese Journal of Chemistry 2022年第19期40卷 2345-2355页

作者： Lei Wu Minyan Wang Yong Liang Zhuangzhi Shi State Key Laboratory of Coordination Chemistry School of Chemistry and Chemical EngineeringNanjing UniversityNanjingJiangsu210093 China School of Chemistry and Chemical Engineering Henan Normal UniversityXinxiangHenan453007 China

Monofluoroalkenes are important and versatile privileged components in pharmacologically relevant molecules.Here,we report a method for the selective construction of these compounds in a diversity-oriented fashion through regiodivergent cross-coupling of gem-difluorocyclopropanes with allylboronates by employing a palladium catalyst with two different ligands,in which gem-difluorocyclopropanes were used as allyl electrophiles by C—C and C—F bond activation.In the presence of 2-biphenylyl(diphenyl)phosphine as ligand,the linear-selective allyl–allyl bond formation is highly obtained,while utilizing the sterically hindered BrettPhos(dicyclohexyl[3,6-dimethoxy-2',4',6'-tris(1-methylethyl)[1,1'-biphenyl]-2-yl]phosphine)as the ligand favors the generation of the branched-selective product.Experimental and computational studies investigated the key steps of the cross-coupling reactions,revealing the origin of the ligand-controlled regiodivergence.

关键词： Allylation C-C activation Cross-coupling gem-Difluorocyclopropanes Defluorination

General Synthetic Iterative Scheme for Unsteady Rarefied Gas Flows

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Communications in Computational Physics 2023年第6期33卷 173-207页

作者： Jianan Zeng Wei Su Lei Wu Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen 518055China Division of Emerging Interdisciplinary Areas The Hong Kong University of Science and TechnologyClear Water BayHong KongChina Department ofMathematics The Hong Kong University of Science and TechnologyClear Water BayHong KongChina Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications Southern University of Science and TechnologyShenzhen 518055China

In rarefied gas flows,the spatial grid size could vary by several orders of magnitude in a single flow configuration(e.g.,inside the Knudsen layer it is at the order of mean free path of gas molecules,while in the bulk region it is at a much larger hydrodynamic scale).Therefore,efficient implicit numerical method is urgently needed for time-dependent problems.However,the integro-differential nature of gas kinetic equations poses a grand challenge,as the gain part of the collision operator is non-invertible.Hence an iterative solver is required in each time step,which usually takes a lot of iterations in the(near)continuum flow regime where the Knudsen number is small;worse still,the solution does not asymptotically preserve the fluid dynamic limit when the spatial cell size is not refined enough.Based on the general synthetic iteration scheme for steady-state solution of the Boltzmann equation,we propose two numerical schemes to push the multiscale simulation of unsteady rarefied gas flows to a new boundary,that is,the numerical solution not only converges within dozens of iterations in each time step,but also asymptotically preserves the Navier-Stokes-Fourier limit in the continuum flow regime,when the spatial grid is coarse,and the time step is large(e.g.,in simulating the extreme slow decay of two-dimensional Taylor vortex,the time step is even at the order of vortex decay time).The properties of fast convergence and asymptotic preserving of the proposed schemes are not only rigorously proven by the Fourier stability analysis for simplified gas kinetic models,but also demonstrated by several numerical examples for the gas kinetic models and the Boltzmann equation.

关键词： Unsteady rarefied gas flow general synthetic iterative scheme fast convergence asymptotic Navier-Stokes preserving

A Data-driven Variable Reduction Approach for Transmission-constrained Unit Commitment of Large-scale Systems

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Journal of Modern Power Systems and Clean Energy 2023年第1期11卷 254-266页

作者： Yuzhou Zhou Qiaozhu Zhai Lei Wu Moammad Shahidehpour Systems Engineering Institute MOEKLINNS LabXi’an Jiaotong UniversityXi’an 710049China Electrical and Computer Engineering Department Stevens Institute of TechnologyHobokenU.S. Electrical and Computer Engineering Department Illinois Institute of TechnologyChicagoU.S. IEEE

This paper presents a data-driven variable reduction approach to accelerate the computation of large-scale transmission-constrained unit commitment(TCUC).Lagrangian relaxation(LR)and mixed-integer linear programming(MILP)are popular approaches to solving TCUC.However,with many binary unit commitment variables,LR suffers from slow convergence and MILP presents heavy computation burden.The proposed data-driven variable reduction approach consists of offline and online calculations to accelerate computational performance of the MILP-based large-scale TCUC problems.A database including multiple nodal net load intervals and the corresponding TCUC solutions is first built offline via the data-driven and all-scenario-feasible(ASF)approaches,which is then leveraged to efficiently solve new TCUC instances online.On/off statuses of considerable units can be fixed in the online calculation according to the database,which would reduce the computation burden while guaranteeing good solution quality for new TCUC instances.A feasibility proposition is proposed to promptly check the feasibility of the new TCUC instances with fixed binary variables,which can be used to dynamically tune parameters of binary variable fixing strategies and guarantee the existence of feasible UC solutions even when system structure changes.Numerical tests illustrate the efficiency of the proposed approach.

关键词： Unit commitment accelerated algorithm data driven variable reduction

Distributionally Robust Economic Dispatch Using IDM for Integrated Electricity-heat-gas Microgrid Considering Wind Power

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CSEE Journal of Power and Energy Systems 2023年第3期9卷 1182-1192页

作者： Yang Liu Xianbang Chen Lei Wu Yanli Ye College of Electrical Engineering Sichuan UniversityChengdu 610065China Department Stevens Institute of TechnologyHobokenNJ 07030 USA

Multi-energy microgrids,such as integrated electricity-heat-gas microgrids(IEHS-MG),have been widely recognized as one of the most convenient ways to connect wind power(WP).However,the inherent intermittency and uncertainty of WP still render serious power curtailment in the operation.To this end,this paper presents an IEHS-MG model equipped with power-to-gas technology,thermal storage,electricity storage,and an electrical boiler for improving WP utilization efficiency.Moreover,a two-stage distributionally robust economic dispatch model is constructed for the IEHSMG,with the objective of minimizing total operational costs.The first stage determines the day-ahead decisions including on/off state and set-point decisions.The second stage adjusts the day-ahead decision according to real-time WP realization.Furthermore,WP uncertainty is characterized through an Imprecise Dirichlet model(IDM)based ambiguity set.Finally,Column-and-Constraints Generation method is utilized to solve the model,which provides a day-ahead economic dispatch strategy that immunizes against the worst-case WP distributions.Case studies demonstrate the presented IEHS-MG model outperforms traditional IEHS-MG model in terms of WP utilization and dispatch economics,and that distributionally robust optimization can handle uncertainty effectively.

关键词： Data-driven day-ahead economic dispatch distributionally robust optimization imprecise dirichlet model integrated electricity-heat-gas microgrid wind power

Calculation Model and Allocation Strategy of Network Usage Charge for Peer-to-peer and Community-based Energy Transaction Market

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Journal of Modern Power Systems and Clean Energy 2023年第1期11卷 144-155页

作者： Dong Han Lei Wu Xijun Ren Shiwei Xia Electrical Engineering Department University of Shanghai for Science and TechnologyShanghai 200093China State Grid Anhui Electric Power Economic Research Institute Hefei 230022China Electrical Engineering Department North China Electric Power UniversityBeijing 102206China

The emergence of prosumers in distribution systems has enabled competitive electricity markets to transition from traditional hierarchical structures to more decentralized models such as peer-to-peer(P2P)and community-based(CB)energy transaction markets.However,the network usage charge(NUC)that prosumers pay to the electric power utility for network services is not adjusted to suit these energy transactions,which causes a reduction in revenue streams of the utility.In this study,we propose an NUC calculation method for P2P and CB transactions to address holistically economic and technical issues in transactive energy markets and distribution system operations,respectively.Based on the Nash bargaining(NB)theory,we formulate an NB problem for P2P and CB transactions to solve the conflicts of interest among prosumers,where the problem is further decomposed into two convex subproblems of social welfare maximization and payment bargaining.We then build the NUC calculation model by coupling the NB model and AC optimal power flow model.We also employ the Shapley value to allocate the NUC to consumers fairly for the NUC model of CB transactions.Finally,numerical studies on IEEE 15-bus and 123-bus distribution systems demonstrate the effectiveness of the proposed NUC calculation method for P2P and CB transactions.

关键词： Electricity market network usage charge distribution locational marginal prices Shapley value Nash bargaining transactive energy peer-to-peer transaction community-based transaction

A Two-stage Peer-to-peer Energy Trading Model for Distribution Systems with Participation of Utility

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CSEE Journal of Power and Energy Systems 2021年第5期7卷 893-902页

作者： Yikui Liu Lei Wu Jie Li ECE Department Stevens Institute of Technology.HobokenNJ07030 USA ECE Department Rowan UniversityGlassboroNJ08028 USA

With the growing penetration of distributed energy resources(DER)in distribution systems,the traditional utility dominated tariff-based business model may no longer meet the need for further development.As a result,the transformation from the traditional tariff-based business model to the emerging peer-to-peer energy trading model has been acknowledged by researchers and policy makers.In this paper,a two-stage peer-to-peer energy trading model is proposed while considering the role of the utility.Specifically,energy transactions between buyers and sellers are optimized in the first stage;the cleared transactions are submitted to the utility for approval in the second stage,which solves a transaction approval model to verify the transactions from the perspective of secure system operations.Indeed,certain transactions mav be disapproved to ensure that all network constraints,such as voltage and line flow limitations,are satisfied.In addition,a comprehensive trading tariff is designed to recover the hidden costs of the utility,such as those associated with network usage,system losses,and ancillary service provision.A modified 33-bus distribution system is adopted to verify the proposed model.

关键词： Terms-Distributed energy resources distribution system energy market peer-to-peer energy trading.