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Seasonal thermal energy storage using natural structures:GIS-based potential assessment for northern China

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Building Simulation 2024年第4期17卷 561-574页

作者： Yichi zhang Jianjun Xia Midea HVAC Heating&Ventilation Equipment Co. LtdFoshan528311China Building Energy Research Center Tsinghua UniversityBeijing100084China

Seasonal thermal energy storage(STES)allows storing heat for long-term and thus promotes the shifting of waste heat resources from summer to winter to decarbonize the district heating(dH)*** being a promising solution for sustainable energy system,large-scale STES for urban regions is lacking due to the relatively high initial investment and extensive land *** close the gap,this study assesses the potentials of using two naturally available structures for STES,namely valley and ground pit *** on geographical information system(GIS)methods,the available locations are searched.f.om digital elevation model and selected considering several criteria from land uses and construction *** costs of dams to impound the reservoir and the yielded storage capacities are then quantified to guide the choice of suitable *** assessment is conducted.f.r the northern China where dH systems and significant seasonal d.f.erences of energy demand *** total,2,273 valley sites and 75 ground pit sites are finally identified with the energy storage capacity of 15.2 billion GJ,which is much larger than the existing dH demand in northern *** results also prove that 682 valley sites can be achieved with a dam cost lower than 20 CNY/m^(3).By conducting sensitivity analysis on the design dam wall height and elevations,the choices of available natural structures are expanded but practical issues about water pressures and constructions are also ***,the identified sites are geographically mapped with nearest urban regions to reveal their roles in the dH *** general,560 urban regions are found with potential STES units and most of them have STES storage capacities larger than their own dH *** novel planning methodology of this study and publicly available datasets create possibilities for the implementations of large-scale STES in urban dH systems.

关键词： seasonal thermal energy storage geographical information system district heating water reservoir

A SIMPLE ITERATIVE ALGORITHM fOR MAXCUT

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Journal of Computational Mathematics 2024年第5期42卷 1277-1304页

作者： Sihong Shao dong zhang Weixi zhang CAPT LMAM and School of Mathematical SciencesPeking UniversityBeijing 100871China LMAM and School of Mathematical Sciences Peking UniversityBeijing 100871China

We propose a simple iterative(SI)algorithm for the maxcut problem through fully using an equivalent continuous *** does not need rounding at all and has advantages that all subproblems have explicit analytic solutions,the cut values are monotonically updated and the iteration points converge to a local optima in finite steps via an appropriate subgradient *** experiments on G-set demonstrate the *** particular,the ratios between the best cut values achieved by SI and those by some advanced combinatorial algorithms in[***.,248(2017),365-403]are at least 0.986 and can be further improved to at least 0.997 by a preliminary attempt to break out of local optima.

关键词： Maxcut Iterative algorithm Exact solution Subgradient selection fractional programming

Enhanced charge separation by incomplete calcination mod.f.ed co-doped TiO_(2)nanoparticle for isothiazolinone photocatalytic degradation

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Nano Research 2024年第6期17卷 4834-4843页

作者： Zhiren Guo Xiao zhang Xinyuan Li Chang Cui Zilei zhang Hansheng Li dongxiang zhang Jinying Li Xiyan Xu Jiatao zhang School of Chemistry and Chemical Engineering Beijing Institute of TechnologyBeijing 102488China department of Chemistry MSU-BIT UniversityShenzhen 517182Chin

Photocatalytic oxidation techniques are promising for degradation of the highly ecotoxic and refractory isothiazolinone bactericides in relevant industrial ***,low charge separation and directional transport efficiency under solar light radiation restrain their practical ***,we report a nanostructured photocatalyst doped with Gd and B in TiO_(2)with carbon incorporation and d.f.ct formation through incomplete *** specific surface area,grain size,and hydrophilicity of TiO_(2)are improved,which is beneficial for the interfacial reaction between the photocatalyst and *** reduction of the bandgap,the broadening of the photo-absorption range,and the retarded electron-hole recombination promote the photocatalytic performance due to the improved oxygen vacancies based on the electron distribution *** d.f.erence in partial density of states(ΔPdOS)between the current catalyst and raw TiO_(2)indicates that the co-doping of Gd and B with incomplete calcination changes the electronic hybridization of conduction band and valence band near the fermi level,and affects the band gap *** improved charge separation and directional transport efficiency and benefited the formation of main active species,including•OH and O_(2)•−,for the pollutant *** rate of photocatalytic removal of benzisothiazolinone(BIT)by the current photocatalyst reaches 1.25 h^(−1),being 4.31 times that of TiO_(2).The current work offers a constructive approach to the design and synthesis of nanostructured photocatalysts for the photocatalytic degradation of refractory organic pollutants.

关键词： TiO_(2)nanoparticle charge separation oxygen vacancies electron distribution mod.f.cation photocatalytic degradation

THE SUPERCLOSENESS Of THE fINITE ELEMENT METHOd.f.R A SINGULARLY PERTURBEd CONVECTION-d.f.USION PROBLEM ON A BAKHVALOV-TYPE MESH IN 2d

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Acta Mathematica Scientia 2024年第4期44卷 1572-1593页

作者： Chunxiao zhang Jin zhang School of Mathematics and Statistics Shandong Normal UniversityJinan 250014China

for singularly perturbed convection-d.f.usion problems,supercloseness analysis of the finite element method is still open on Bakhvalov-type meshes,especially in the case of *** d.f.iculties arise from the width of the mesh in the layer adjacent to the transition point,resulting in a suboptimal estimate for *** analysis techniques cannot handle these d.f.iculties *** fill this gap,here a novel interpolation is designed delicately for the smooth part of the solution,bringing about the optimal supercloseness result of almost order 2 under an energy norm for the finite element *** theoretical result is uniform in the singular perturbation parameterεand is supported by the numerical experiments.

关键词： singularly perturbed convection-d.f.usion finite element method supercloseness Bakhvalov-type mesh

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Electronic origin of structural degradation in Li-rich transition metal oxides:The case of Li_(2)MnO_(3)and Li_(2)RuO_(3)

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Journal of Semiconductors 2024年第4期45卷 82-86页

作者： Peng zhang Key Laboratory of Optoelectronic devices and Systems of Ministry of Education and Guangdong Province College of Physics andOp toelec-tronic EngineeringShenzhen UniversityShenzhen 518060China

Li_(2)MnO_(3)and Li_(2)RuO_(3)represent two prototype Li-rich transition metal(TM)oxides as high-capacity cathodes for Li-ion batteries,which have similar crystal structures but show quite d.f.erent cycling ***,based on the first-princi-ples calculations,we systematically studied the electronic structures and d.f.ct properties of these two Li-rich cathodes,in order to get more understanding on the structural degradation mechanism in Li-rich TM *** calculations indicated that the structural and cycling stability of Li_(2)MnO_(3)and Li_(2)RuO_(3)depend closely on their electronic structures,especially the energy of their highest occupied electronic states(HOS),as it largely determines the d.f.ct properties of these *** Li_(2)MnO_(3)with low-energy HOS,we found that,due to the d.f.ct charge transfer mechanism,various d.f.cts can form spontaneously in its host structure as Li ions are extracted upon delithiation,which seriously deteriorates its structural and cycling *** for Li_(2)RuO_(3),on the other hand,we identified that the high-energy HOS prevents it from the d.f.ct formation upon delithi-ation and thus preserve its cycling *** studies thus illustrated an electronic origin of the structural degradation in Li-rich TM oxides and implied that it is possible to improve their cycling performances by carefully adjusting their TM compo-nents.

关键词： d.f.cts Li-ion batteries first-principles calculations

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Near-surface wind.f.eld characteristics of the desert-oasis transition zone in dunhuang,China

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Journal of Arid Land 2024年第5期16卷 654-667页

作者： PAN Jiapeng zhang Kecun AN Zhishan zhang Yu Key Laboratory of desert and desertification&dunhuang Gobi and desert Ecology and Environment Research Station Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

The desert-oasis transition zone(dOTZ)serves as a buffer area between the desert and *** its wind.f.eld characteristics is of great significance for the prevention and control of aeolian disasters in the *** this study,we used meteorological data during 2013–2019 from the portable meteorological stations at five sites(site A on the edge of the oasis,sites B,C,and d in the dOTZ,and site O in the desert)in dunhuang,China to analyze the near-surface wind.f.eld characteristics and their causes,as well as to reveal the key role of the dOTZ in oasis *** results showed that the mean wind speed.f.equency of sand-driving wind,and directional variability of wind decreased.f.om west to east within the dOTZ,and wind speed was significantly affected by air *** terrain influenced the prevailing winds in the region,mainly from northeast and *** some areas adjacent to the oasis were controlled by southeasterly *** indicated that the near-surface wind.f.eld characteristics of the dOTZ were caused by the combined effects of local terrain and surface hydrothermal *** site d,the annual drift potential(dP)was 24.95 vector units(VU),indicating a low wind energy environment,and the resultant drift direction(Rdd)showed obvious seasonal ***,the dOTZ played an important buffering role between the desert and *** with the desert,the mean wind speed in the oasis decreased by 64.98%,and the prevailing wind direction was more *** results of this study will be useful in interpreting the aeolian activity of the dOTZ in dunhuang.

关键词： desert-oasis transition zone near-surface wind.f.eld hydrothermal d.f.erence sand-driving wind aeolian environment dunhuang

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Localized-states quantum confinement induced by roughness in CdMnTe/CdTe heterostructures grown on Si(111) substrates

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Journal of Semiconductors 2024年第9期45卷 28-35页

作者： Leonarde N.Rodrigues Wesley f.Inoch Marcos L.f.Gomes Odilon d.d.Couto Jr. Bráulio S.Archanjo Sukarno O.ferreira Physics department Federal University of ViçosaViçosa36570-900Minas GeraisBrazil Instituto de física Gleb Wataghin Universidade Estadual de CampinasCampinas13083-859São PauloBrazil National Institute of Metrology Quality and Technology(Inmetro) Materials Metrology Division(DIMAT)Xerém2525-020Rio de JaneiroBrazil

This work shows that despite a lattice mismatch of almost 20%, CdMnTe/CdTe/CdMnTe heterostructures grown directly on Si(111) have surprisingly good optical emission properties. The investigated structures were grown by molecular beam epitaxy and characterized by scanning transmission electron microscopy, macro-and micro-photoluminescence. Low temperature macro-photoluminescence experiments indicate three emission bands which depend on the CdTe layer thickness and have d.f.erent confinement characteristics. Temperature measurements reveal that the lower energy emission band (at 1.48 eV)is associated to d.f.cts and bound exciton states, while the main emission at 1.61 eV has a weak 2d character and the higher energy one at 1.71 eV has a well-d.f.ned (zero-dimensional, 0d) 0d nature. Micro-photoluminescence measurements show the existence of sharp and strongly circularly polarized (up to 40%) emission lines which can be related to the presence of Mn in the heterostructure. This result opens the possibility of producing photon sources with the typical spin control of the diluted magnetic semiconductors using the low-cost silicon technology.

关键词： CdMnTe/CdTe/CdMnTe heterostructure CdTe/CdMnTe quantum emitters quantum dot-like emission silicon(111)substrate

Toughening additive manufactured Zr-based bulk metallic glass composites by martensite phase transformation

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Journal of Materials Science & Technology 2024年第3期170卷 95-102页

作者： Pengcheng zhang Cheng zhang Jie Pan di Ouyang Lin Liu State Key Laboratory of Materials Processing and die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Additive manufacturing technology based on laser powder bed.f.sion(LPBf)offers a novel approach for fabricating bulk metallic glass(BMG)products without restriction in size and ***,the BMGs prepared by LPBf usually suffered.f.om less plasticity and poorer fracture toughness as compared to their cast counterparts due to partial crystallization in heat-affected zones(HAZs).Since crystallization in HAZs is hard to avoid completely in LPBf BMGs,it is desirable to design a suitable alloy system,in which only ductile crystalline phase,instead of brittle intermetallics,is formed in *** unique structure could effectively increase the toughness/plasticity of the LPBf *** achieve this goal,a quaternary BMG system with a composition of Zr_(47.5)Cu_(45.5)Al_(5)Co_(2)is adopted and subjected to *** is found that nearly a single phase of B_(2)-ZrCu is precipitated in HAZs,while a fully amorphous phase is formed in molten pools(MPs).This B_(2)phase reinforced BMG composite exhibits excellent mechanical properties with enhanced plasticity and ***,it is easy to modulate the mechanical properties by altering the amount of the B_(2)phase via adjusting the laser energy ***,the best combination of strength,plasticity,and notch toughness is obtained in the BMG composite containing 27.4%B_(2)phase and 72.6%amorphous phase,which exhibits yield strength(σ_(s))of 1423 MPa,plastic strain(ε_(p))of 4.65%,and notch toughness(K_(q))of 53.9 MPa m 1/***,a notable strain-hardening is also *** improvement of plasticity/toughness and appearance of strain-hardening behavior are mainly due to the martensite phase transformation from the B_(2)phase to the Cm phase during plastic d.f.rmation(i.e.,the phase transformation-induced plasticity effect).The current work provides a guide for making advanced BMGs and BMG composites by additive manufacturing.

关键词： Laser powder bed.f.sion Bulk metallic glass composites Phase transformation-induced plasticity d.f.rmation mechanism

A novel graph oversampling framework for node classification in class-imbalanced graphs

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Science China(Information Sciences) 2024年第6期67卷 214-229页

作者： Riting XIA Chunxu zhang Yan zhang Xueyan LIU Bo YANG Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University College of Artificial Intelligence Jilin University College of Computer Science and Technology Jilin University College of Communication Engineering Jilin University

Graph neural network(GNN) is a promising method to analyze graphs. Most existing GNNs adopt the class-balanced assumption, which cannot deal with class-imbalanced graphs well. The oversampling technique is effective in alleviating class-imbalanced problems. However, most graph oversampling methods generate synthetic minority nodes and their edges after applying GNNs. They ignore the problem that the representations of the original and synthetic minority nodes are dominated by majority nodes caused by aggregating neighbor information through GNN before oversampling. In this paper, we propose a novel graph oversampling framework, termed distribution alignment-based oversampling for node classification in classimbalanced graphs(named Graph-dAO). Our framework generates synthetic minority nodes before GNN to avoid the dominance of majority nodes caused by message passing in GNNs. Additionally, we introduce a distribution alignment method based on the sum-product network to learn more information about minority nodes. To our best knowledge, it is the first to use the sum-product network to solve the class-imbalanced problem in node classification. A large number of experiments on four real datasets show that our method achieves the optimal results on the node classification task for class-imbalanced graphs.

关键词： graph neural network class-imbalanced graphs sum-product network oversampling node classification