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Error Estimate of Full-Discrete Numerical Scheme for the Nonlocal Allen-Cahn Model

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Journal of Mathematical Research with Applications 2024年第3期44卷 344-358页

作者： Jun zhang xiaohu YANG Fulin MEI Zhimei JI Yu zhang School of Mathematics and Statistics Guizhou University of Finance and Economics The Meteorological Disaster Prevention Center of Guizhou Province Xi'an Institute of Applied Optics Financial Department Guizhou University of Finance and Economics

In this work, we study the error estimates of the fully discrete Fourier pseudospectral numerical scheme for solving the nonlocal volume-conserved Allen-Cahn(AC) equation.The time marching method of the numerical scheme is based on the well-known Invariant Energy Quadratization(IEQ) method. We demonstrate that the proposed fully discrete numerical method is uniquely solvable, unconditionally energy stable, and obtain the optimal error estimate of the scheme for both space and time. Additionally, we conduct several numerical tests to verify the theoretical results.

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Risk-constrained Energy Management Strategy for a Commercial Campus Considering Comprehensive Reserves Against Islanding Conditions

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CSEE Journal of Power and Energy Systems 2023年第5期9卷 1797-1807页

作者： Zheming Liang Desong Bian xiaohu zhang Di Shi GEIRI North America San JoseCAUSA.Z.M.Liang is also with Huaneng Renewables Co.Ltd.Beijing 100036China

This paper proposes an optimal risk-constrained energy management strategy for commercial buildings in a commercial campus with islanding capabilities.The goal is to minimize the total operation and maintenance costs,while maximizing comprehensive comfort levels for the occupants.A two-stage riskconstrained,scenario-based stochastic optimization approach is adopted to handle various uncertainties associated with the energy management process,such as power generation of rooftop solar panels,arrival state-of-charges,and arrival/departure time of plug-in electric vehicles,intermittent load demand,and uncertain grid-connection conditions.A conditional-valueat-risk method is introduced to provide a risk-averse energy management strategy.To face the challenge of both reducing the computational burden and maintaining the accuracy of the stochastic programming,an advanced scenario reduction method is leveraged.Extensive simulation results validate the effectiveness of the proposed energy management strategy for minimizing total operating and maintenance costs of commercial buildings with islanding capabilities,while maximizing comprehensive comfort levels of the occupants.

关键词： Comprehensive comfort levels CVaR energy management islanding capability reserve stochastic programming uncertainty

A universal performance-enhancing method for Li-S batteries:the cathode material of Li_(2)S@Li_(2)S_(2)@Li_(2)S_(6) double-shell structure

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Science China Chemistry 2024年第4期67卷 1229-1241页

作者： Shunjin Yang Yujiang Sun Qiaran zhang xiaohu Hu Xing Chen Guoran Li Xiao Sun Yuzhe zhang Shijie Xu Xinyu Wang Yongan Yang Institute of Molecular Plus School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China College of Materials Science and Engineering Nankai UniversityTianjin 300350China Haihe Laboratory of Sustainable Chemical Transformations Tianjin 300192China Tianjin Key Laboratory of Advanced Carbon and Electrochemical Energy Storage Tianjin 300072China

Lithium sulfide(Li_(2)S)as a cathode material for lithium-sulfur(Li-S)batteries,one of the most promising advanced batteries in the future,has received tremendous attention in the past decades.However,developing the practical Li_(2)S cathode confronts challenges of low conductivity for Li-ions and electrons,high sensitivity to environmental moisture,big overpotential barrier to electrochemical activation,and poor cyclability due to the shuttle effect of intermediate species.This article herein reports a simple and effective strategy for making Li_(2)S@Li_(2)S_(2)@Li_(2)S_(6) double-shelled microparticles,which can significantly mitigate these problems.They are synthesized by dissolving Li2S together with S in dimethoxyethane,then drying off the solvent,and finally calcining the collected solid.Compared with pure Li_(2)S,such a double-shell material presents a 26.7% improvement in cycling capacity,0.5 V lower in activation overpotential,and prolonged tolerance in the ambient environment.The density functional theory calculation shows that the performance enhancement lies in the higher stability of Li2S6in contact with moisture and some autocatalytic effect of Li_(2)S_(2)@Li_(2)S_(6).Such a double-shell structure becomes a universal performanceenhancing approach when being combined with other means,such as cathodes composited with catalytic MoS_(2),separators modified with selenium-doped sulfurized-polyacrylonitrile/montmorillonite,electrolytes containing fluorenone additive,and Li anodes coated with a layer of Li_(3)N.The corresponding capacity retention shows up to 80%improvement compared with pure Li_(2)S.

关键词： lithium-sulfur batteries lithium sulfide lithium polysulfides cathode performance double shell structure

Unique double-layer solid electrolyte interphase formed with fluorinated ether-based electrolytes for high-voltage lithium metal batteries

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Journal of Energy Chemistry 2024年第1期88卷 532-542,I0012页

作者： Ruo Wang Jiawei Li Bing Han Qingrong Wang Ruohong Ke Tong zhang xiaohu Ao Guangzhao zhang Zhongbo Liu Yunxian Qian Fangfang Pan Iseult Lynch Jun Wang Yonghong Deng Department of Materials Science&Engineering School of Innovation and EntrepreneurshipSouthern University of Science and TechnologyShenzhen 518055GuangdongChina School of Geography Earth and Environmental SciencesUniversity of BirminghamEdgbastonBirmingham B152TTUK Key Laboratory of Marine Environmental Corrosion and Bio-Fouling Institute of OceanologyChinese Academy of SciencesQingdao 266071ShandongChina Shenzhen CAPCHEM Technology Co. Ltd.Shenzhen 518118GuangdongChina CALB Group Co. Ltd.Changzhou 213200JiangsuChina

Li metal batteries using high-voltage layered oxides cathodes are of particular interest due to their high energy density.However,they suffer from short lifespan and extreme safety concerns,which are attributed to the degradation of layered oxides and the decomposition of electrolyte at high voltage,as well as the high reactivity of metallic Li.The key is the development of stable electrolytes against both highvoltage cathodes and Li with the formation of robust interphase films on the surfaces.Herein,we report a highly fluorinated ether,1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy)methoxy]ethane(TTME),as a cosolvent,which not only functions as a diluent forming a localized high concentration electrolyte(LHCE),but also participates in the construction of the inner solvation structure.The TTME-based electrolyte is stable itself at high voltage and induces the formation of a unique double-layer solid electrolyte interphase(SEI)film,which is embodied as one layer rich in crystalline structural components for enhanced mechanical strength and another amorphous layer with a higher concentration of organic components for enhanced flexibility.The Li||Cu cells display a noticeably high Coulombic efficiency of 99.28%after 300 cycles and Li symmetric cells maintain stable cycling more than 3200 h at 0.5 mA/cm^(2) and 1.0m Ah/cm^(2).In addition,lithium metal cells using LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) and Li CoO_(2) cathodes(both loadings~3.0 m Ah/cm^(2))realize capacity retentions of>85%over 240 cycles with a charge cut-off voltage of 4.4 V and 90%for 170 cycles with a charge cut-off voltage of 4.5 V,respectively.This study offers a bifunctional ether-based electrolyte solvent beneficial for high-voltage Li metal batteries.

关键词： Lithium metal batteries High-voltage layered oxides Fluorinated ether-based electrolytes Solid electrolyte interphase Cathode electrolyte interphase

Direct catalytic nitrogen oxide removal using thermal, electrical or solar energy

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Chinese Chemical Letters 2022年第3期33卷 1117-1130页

作者： xiaohu zhang Lixiao Han Hao Chen Shengyao Wang College of Science Huazhong Agricultural UniversityWuhan 430070China

Considering the significant importance in both ecological and environmental fields, converting nitrogen oxide(NO_(x), especially NO) into value-added NH3or harmless N2lies in the core of research over the past decades. Exploring catalyst for related gas molecular activation and highly efficient reaction systems operated under low temperature or even mild conditions are the key issues. Enormous efforts have been devoted to NO removal by utilizing various driving forces, such as thermal, electrical or solar energy,which shine light on the way to achieve satisfying conversion efficiency. Herein, we will review the stateof-the-art catalysts for NO removal driven by the above-mentioned energies, including a comprehensive introduction and discussion on the pathway and mechanism of each reaction, and the recent achievements of catalysts on each aspect. Particularly, the progress of NO removal by environmentally friendly photocatalysis and electrocatalysis methods will be highlighted. The challenges and opportunities in the future research on the current topic will be discussed as well.

关键词： NO removal Photo-catalysis Electro-catalysis Thermo-catalysis Oxidation Reduction

A new insight into LPSO phase transformation and mechanical properties uniformity of large-scale Mg-Gd-Y-Zn-Zr alloy prepared by multi-pass friction stir processing

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Journal of Magnesium and Alloys 2024年第5期12卷 2041-2056页

作者： xiaohu Guan Wen Wang Ting zhang Pai Peng Qiang Liu Peng Han Ke Qiao Jun Cai Liqiang Wang Kuaishe Wang School of Metallurgical Engineering National and Local Joint Engineering Research Center for Functional Materials Processing Xi'an University of Architecture and Technology Xi'an Rare Metal Materials Institute Co.Ltd State Key Laboratory of Metal Matrix Composites School of Material Science and Engineering Shanghai Jiao Tong University

A large-scale fine-grained Mg-Gd-Y-Zn-Zr alloy plate with high strength and ductility was successfully prepared by multi-pass friction stir processing(MFSP) technology in this work. The structure of grains and long period stacking ordered(LPSO) phase were characterized,and the mechanical properties uniformity was investigated. Moreover, a quantitative relationship between the microstructure and tensile yield strength was established. The results showed that the grains in the processed zone(PZ) and interfacial zone(IZ) were refined from 50 μm to 3 μm and 4 μm, respectively, and numerous original LPSO phases were broken. In IZ, some block-shaped 18R LPSO phases were transformed into needle-like 14H LPSO phases due to stacking faults and the short-range diffusion of solute atoms. The severe shear deformation in the form of kinetic energy caused profuse stacking fault to be generated and move rapidly, greatly increasing the transformation rate of LPSO phase. After MFSP, the ultimate tensile strength, yield strength and elongation to failure of the large-scale plate were 367 MPa, 305 MPa and 18.0% respectively. Grain refinement and LPSO phase strengthening were the major strengthening mechanisms for the MFSP sample.In particularly, the strength of IZ was comparable to that of PZ because the strength contribution of the 14H LPSO phase offsets the lack of grain refinement strengthening in IZ. This result opposes the widely accepted notion that IZ is a weak region in MFSP-prepared large-scale fine-grained plate.

关键词： Friction stir processing Multi-pass Mg-Gd-Y-Zn-Zr alloy LPSO phase transformation Mechanical properties

Voltage Stability Constrained Optimal Power Flow for Unbalanced Distribution System Based on Semidefinite Programming

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Journal of Modern Power Systems and Clean Energy 2022年第6期10卷 1614-1624页

作者： Yanling Lin xiaohu zhang Jianhui Wang Di Shi Desong Bian GEIRI North America San JoseUSA Southern Methodist University DallasUSA

This paper proposes a voltage stability constrained optimal power flow(VSC-OPF)for an unbalanced distribution system with distributed generators(DGs)based on semidefinite programming(SDP).The AC optimal power flow(ACOPF)for unbalanced distribution systems is formulated as a chordal relaxation-based SDP model.The minimal singular value(MSV)of the power flow Jacobian matrix is adopted to indicate the voltage stability margin.The Jacobian matrix can be explicitly expressed by ACOPF state variables.The nonlinear constraint on the Jacobian MSV is then replaced with its maximal convex subset using linear matrix inequality(LMI),which can be incorporated in the SDP-based ACOPF formulation.A penalty technique is leveraged to improve the exactness of the SDP relaxation.Case studies performed on several IEEE test systems validate the effectiveness of the proposed method.

关键词： Voltage stability semidefinite programming Jacobian matrix optimal power flow

Energy Planning of Beijing Towards Low-carbon,Clean and Efficient Development in 2035

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 913-928页

作者： Chengzhou Li Ningling Wang xiaohu Shen Yumeng zhang Zhiping Yang Xiaofeng Tong François Maréchal Ligang Wang Yongping Yang Institute of Energy Power Innovation North China Electric Power UniversityBeijing 102206China School of Energy Power and Mechanical Engineering and National Research Center for Thermal Power Engineering and TechnologyNorth China Electric Power UniversityBeijing 102206China Industrial Process and Energy Systems Engineering Swiss Federal Institute of Technology in LausanneSionSwitzerland

Energy transition towards clean,efficient energy supply has been a common sense of the government and public in China.However,lacking reasonable planning will lead to undisciplined development,resource waste,and excessive investment.In this context,this paper investigates potential pathways of Beijing energy transition towards a high-level low-carbon,clean and efficient energy system in 2035 with an extended energysocpe model.Firstly,based on available data,future energy demands are predicted by a newly proposed hybrid forecasting method,which combines the traditional regression model,grey model,and support vector machine model with an entropy-based weighted factor.Secondly,the superstructure-based optimization model is employed to investigate the system configuration and operation strategy of the future Beijing energy system.Finally,the uncertainty impact of electricity price,natural gas price,hydrogen price,and the capital expenditures of electrolyzer and steam methane reforming for hydrogen applications are studied.The forecasting results show that all walks of life will witness a continuously increasing energy demand in multiple sectors of Beijing towards 2035.The planning results suggest that the imported electricity and natural gas will dominate the energy supply of Beijing in 2035 with a contribution of 86%of the energy resources consumption of 384 TWh.Moreover,the energy system presents a high end-use electrification level of 65%and high penetration of efficient technologies,which supply 119 TWh via combined heat and power,26 TWh via heat pump and 95 TWh via district heating network.The energy use of various sectors of energy resources,technologies and end-use are closely related.Hydrogen will have an increased penetration in the private mobility sector,but the locally generated hydrogen is mainly from steam methane reforming technology.

关键词： Energy transition energy planning carbonneutral demand forecasting energyscope

Valorization of Asparagus leafy by-product by ionic-liquid extraction and characterization of bioactive compounds in the extracts

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Food Bioscience 2022年第2期46卷 857-864页

作者： Bimal Chitrakar Min zhang Sakamon Devahastin Benu Adhikari xiaohu zhang State Key Laboratory of Food Science and Technology Jiangnan University214122WuxiJiangsuChina College of Food Science and Technology Hebei Agricultural UniversityBaoding071001HebeiChina Jiangsu Province International Joint Laboratory on Fresh Food Smart Processing and Quality Monitoring Jiangnan University214122WuxiJiangsuChina Advanced Food Processing Research Laboratory Department of Food EngineeringFaculty of EngineeringKing Mongkut’s University of Technology Thonburi126 Pracha u-tid RoadBangkok10140Thailand School of Science RMIT UniversityMelbourneVIC3083Australia Nantong Shuangyang Ecological Agriculture Technology Co. Ltd.NantongJiangsuChina

Asparagus(Asparagus officinalis)is a high-value low-calorie vegetable with array of bioactive compounds.Asparagus processing nevertheless generates substantial quantity of by-products;their valorization is of utmost importance for the sustainability of the industry.Here,feasibility of using four imidazolium-based ionic liquids and their combinations as well as water and methanol to extract bioactive compounds from asparagus leafy by-product was investigated.Effectiveness of ultrasound-microwave-assisted heating to augment extraction was also assessed.1-ethyl-3-methylimidazolium-bromide(EMIMBr)resulted in the highest extraction yield of rutin(25.7 mg/g),which is the most abundant compound in the by-product;such a yield was comparable to that achievable via methanol extraction.Ultrasound-microwave-assisted extraction did not show significant improvement in rutin yield when EMIMBr was used.Interestingly,although methanolic extract exhibited slightly higher content of rutin,it also contained the higher number of impurities;EMIMBr extract contained less impurities with higher relative content of rutin(70.9%)than that in methanolic extract(67.7%).This could be a milestone in extraction work for an efficient purification.

关键词： 1-Ethy-3-methylimidazolium bromide Ionic-liquid Methanol-extraction Rutin Ultrasound-microwave extraction