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On electro-acoustic characteristics of a marine broadband sparker for seismic exploration

Journal of Oceanology and Limnology 2024年第3期42卷 760-771页

作者： Jing LI Kai liu Liancheng ZHANg Chenguang.liu Yanliang PEI Baohua liu Key Laboratory of Marine geology and Metallogency First Institute of OceanographyMinistry of Natural ResourcesQingdao 266061China Laboratory of Marine geology Laoshan LaboratoryQingdao 266237China Key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech UniversityHangzhou 310018China Key Laboratory of Submarine Acoustic Investigation and Application of Qingdao(Preparatory) Qingdao 266061China Key Laboratory of Deep Sea Mineral Resources Development Shandong(Preparatory)Qingdao 266061China

The construction of major marine infrastructure projects and the exploration and development of deep-sea mineral resources require fine imaging of seabed strata and *** highresolution marine seismic exploration based on a high broadband sparker source is an important approach to reveal seabed stratum and reservoir structure,and identify *** optimize the performance of sparker seismic source,we investigated the electro-acoustic characteristics of spark discharge under conditions of different charging voltages and electrode *** show that the sound source level increased with the increase of the charging voltage,whereas the main frequency decreased when the charging voltage *** addition,it was found that the charging capacitance had more obvious influence on the main frequency than the sound source level *** the load energy decreased with increasing electrode number,the sound source level still increased but the main frequency ***,the primary to bubble(P/B)ratio increased with the increase of the electrode *** gain a deeper insight into the electro-acoustic characteristics,we investigate the relationship between sound source level and power peak,from which a good correlation was observed.A more practical statistical analysis on the rise rate of current was processed,and a perfect logarithmic function was ***,we found that the main frequency was most possibly subjected to the electrical energy,especially the charging energy per *** results indicate that the charging energy per electrode less than 10 J could increase the main frequency to above 300 *** last,the main frequency could be reduced to 20 Hz when the charging energy of a single-electrode discharge was enhanced to over 4 *** study shall be helpful in developing a sparker seismic source and improving the performance for marine engineering exploration and geohazard assessment.

关键词： high-resolution marine seismic exploration sparker seismic source sound source level main frequency electro-acoustic characteristics

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Exponential Time Differencing Method for a Reaction-Diffusion System with Free Boundary

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Communications on Applied Mathematics and Computation 2024年第1期6卷 354-371页

作者： Shuang.liu Xinfeng.liu Department of Mathematics University of CaliforniaSan Diego9500 Gilman DriveLa JollaCalifornia92093-0112USA Department of Mathematics University of South CarolinaColumbiaSouth Carolina29208USA

For reaction-diffusion equations in irregular domains with moving boundaries,the numerical stability constraints from the reaction and diffusion terms often require very restricted time step sizes,while complex geometries may lead to difficulties in the accuracy when discretizing the high-order derivatives on grid points near the *** is very challenging to design numerical methods that can efficiently and accurately handle both *** an implicit scheme may be able to remove the stability constraints on the time step,however,it usually requires solving a large global system of nonlinear equations for each time step,and the computational cost could be *** factor(IF)or exponential time differencing(ETD)methods are one of the popular methods for temporal partial differential equations(PDEs)among many other *** our paper,we couple ETD methods with an embedded boundary method to solve a system of reaction-diffusion equations with complex *** particular,we rewrite all ETD schemes into a linear combination of specificФ-functions and apply one state-of-the-art algorithm to compute the matrix-vector multiplications,which offers significant computational advantages with adaptive Krylov *** addition,we extend this method by incorporating the level set method to solve the free boundary *** accuracy,stability,and efficiency of the developed method are demonstrated by numerical examples.

关键词： Reaction diffusion equations Free boundary Integrating factor method Level set method

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Performance of composite foundations with different load transfer platforms and substratum stiffness over silty clay

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Journal of Mountain Science 2024年第5期21卷 1761-1774页

作者： ZHANg Shuming.liu Yan YUAN Shengyang.liu Xianfeng JIANg guanlu liu Junyan School of Civil Engineering and Architecture University of JinanJinan 250022China The Engineering Technology Research Center for Urban Underground Engineering Supporting and Risk Monitoring of Shandong Province Jinan 250022China School of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China Key Laboratory of High-speed Railway Engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu 610031China

The semi-rigid pile-supported composite foundation is widely used in highway projects due to its effectiveness in increasing the bearing capacity and stability of *** is crucial to understand the stress distribution across the embankment width and the behaviour of unreinforced ***,five centrifuge tests were conducted to examine the bearing and deformation behaviours of NPRS(Non-Connected Piled Raft Systems)and gRPS(geosyntheticReinforced Pile-Supported systems)with varying substratum stiffness,then a comparative analysis was conducted on embankment settlement,pressures underneath the embankments,and axial forces along the *** results indicated that greater substratum stiffness correlates with reduced settlement and deformation at various *** occurring 5 meters from the embankment toe includes settlement in NPRS and upward movement in *** potential sliding surface is primarily located within the embankment in NPRS,whereas it may extend through both the embankment and foundation in *** pile-soil stress ratio and efficiency in NPRS are higher than in gRPS across the *** axial force borne by end-bearing piles is significantly greater than that by floating *** the buried depth increases,the axial force in gRPS initially rises then declines,whereas in NPRS,it remains relatively constant within a certain range before *** study aids in assessing the applicability of composite foundations in complex railway environments and provides a reference for procedural measures under similar conditions.

关键词： Centrifuge modelling Composite foundation Failure mode Load transfer platform Substratum Stiffness Silty clay

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Atomistic study on the microscopic mechanism of grain boundary embrittlement induced by small dense helium bubbles in iron

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Nuclear Science and Techniques 2024年第3期35卷 84-95页

作者： Lei Peng Yong-Jie Sun Jing-Yi Shi Yi-Fei liu Shang-Ming Chen liu-liu Li State Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230027China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610213China

The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic steel,which is a candidate structural material for fusion *** order to elucidate the susceptibility of different grain boundaries(gBs)to helium-induced embrittlement,the tensile fracture processes of 10 types of gBs with and without helium bubbles in body-centered cubic(bcc)iron at the relevant service temperature of 600 K were investigated via molecular dynamics *** results indicate that in the absence of helium bubbles,the gBs studied here can be classified into two distinct categories:brittle gBs and ductile *** atomic scale analysis shows that the plastic deformation of ductile gB at high temperatures originates from complex plastic deformation mechanisms,including the Bain/Burgers path phase transition and deformation twinning,in which the Bain path phase transition is the most dominant plastic deformation ***,the presence of helium bubbles severely inhibits the plastic deformation channels of the gBs,resulting in a significant decrease in elongation at *** bubble-decorated gBs,the ultimate tensile strength increases with the increase in the misorientation ***,the coherent twin boundary∑3{112}was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.

关键词： Helium bubble grain boundary Embrittlement Reduced activation ferritic martensitic steel Molecular dynamics Bain path

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Atomically precise Ru-O-Ru clusters for enhanced water dissociation in alkaline hydrogen evolution

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Nano Research 2024年第8期17卷 6993-7000页

作者： Dong.liu Li Xu Sicheng Li Airong Xu Yuanhua Sun Tong.liu Mengyuan liu Huijuan Wang Xiaokang.liu Tao Yao Tao Ding Hefei National Research Center for Physical Sciences at the Microscale School of Nuclear Science and TechnologyKey Laboratory of Precision and Intelligent ChemistryNational Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei 230029China Experimental Center of Engineering and Materials Science University of Science and Technology of ChinaHefei 230026China

Atomic clusters typically exhibit distinctive electronic structures and physicochemical ***,as the size decreases,their ability to adsorb and dissociate water also diminishes,thereby affecting chemical reactions involving water *** the adsorption and dissociation capabilities of atomic clusters towards water molecules and elucidating the mechanisms underlying their performance enhancement have become important research ***,employing the carrier-anchored strategy,Ru-O-Ru atomic clusters were prepared and displayed excellent activity and durability in the hydrogen evolution ***,the Ru-O-Ru atomic clusters exhibited only 86 mV overpotential at 100 mA·cm−^(2)and superior membrane-electrode-assembly activity than commercial Ru/C *** radiation-based Fourier transform infrared spectroscopic measurements revealed that the modification of oxygen in Ru-O-Ru units promoted the reorientation of water molecules from a H-up orientation to H-down,therefore,enhanced the formation of strong hydrogen-bond network of interfacial water on the surface of Ru-O-Ru clusters,leading to enhanced adsorption and dissociation of water and accelerated Volmer *** findings provide a potential strategy and deep insights for the development of atomic clusters in electrocatalysts.

关键词： hydrogen evolution in-situ Fourier transform infrared(FTIR) Ru catalysts electrocatalysis atomic clusters

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Unlocking high-efficiency oxygen evolution reaction through Co-N coordination engineering in Co@N-doped porous carbon core–shell nanoparticles

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Nano Research 2024年第8期17卷 7068-7076页

作者： Shucheng.liu Yu Shuai Xiaosi Qi Zhao Ding Yi liu College of Big Data and Information Engineering Guizhou UniversityGuiyang 550025China College of Physics Guizhou Province Key Laboratory for Photoelectrics Technology and ApplicationGuizhou UniversityGuiyang 550025China

Modulation of metal sites coordination can significantly refine the electronic architecture of catalysts,thereby improving their catalytic *** work successfully developed a core–shell Co@N-doped porous carbon(Co@NC)catalyst by pyrolyzing the COF/MOF(IISERP-COF3/ZIF-67)composite in an inert *** Co@NC catalyst exhibited impressive oxygen evolution reaction(OER)performance,with a small overpotential of 304 mV and a modest Tafel slope of 88.6 mV·dec^(−1)in a 1 M KOH,alongside remarkable stability,maintaining 98.5%of its activity over 13 *** role of IISERP-COF3 was pivotal in preventing Co atom aggregation during the ZIF-67 pyrolysis,which facilitated the creation of mesopores for enhanced mass transport and ***,it effectively modulated the Co-N coordination to fine-tune the electronic structure,thereby optimizing the catalyst's capacity for adsorption of intermediates and boosting its intrinsic *** functional theory(DFT)studies corroborate that the exceptional OER efficiency of Co@NC can be linked to the enhanced Co-N coordination,optimizing the localized electronic structure at the Co active *** study not only proposes an innovative approach for optimizing COF/MOF as effective electrocatalysts but also clears the path for the emergence of affordable,high-performance alternatives to precious metal-based catalysts,marking a significant advancement in sustainable energy technologies.

关键词： covalent organic framework(COF) metal-organic framework(MOF) core-shell structure catalysts oxygen evolution reaction

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Contact engineering for temperature stability improvement of Bi-contacted MoS2 field effect transistors

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Science China(Information Sciences) 2024年第6期67卷 172-179页

作者： Zizheng.liu Qing ZHANg Xiaohe HUANg Chunsen liu Peng ZHOU State Key Laboratory of Integrated Chip and Systems School of MicroelectronicsZhangjiang Fudan International Innovation CenterFudan University Frontier Institute of Chip and System Shanghai Key Lab for Future Computing Hardware and SystemFudan University Shaoxin Laboratory

Semimetallic bismuth（Bi） is one of the most effective strategies for reducing the contact resistance of two-dimensional transition metal dichalcogenide field effect transistors（FETs）. However, the low melting point of Bi contact（271.5℃） limits its reliable applications. In this study, we demonstrated that the temperature stability of Bi-contacted electrodes could be improved by inserting a high-melting point semimetallic antimony（Sb） between the Bi contacting layer and the gold（Au） capping layer. The proposed Bi/Sb/Au contact electrodes tended to form a metal mixture with a continuous surface during the heating process（Voids appeared on the surface of the Bi/Au contact electrodes after heating at 120℃）. Because of the improved contacting layer formed by the semimetal Bi/Sb alloy, the fabricated Bi/Sb/Au-contacted molybdenum sulfide（MoS2） FETs with different gate lengths demonstrated higher on-state current stability after heating treatment than the Bi/Au contact. Because of the Bi/Sb/Au contact and poly（methyl methacrylate） package, the MoS2FETs demonstrated time stability of at least two months from the almost unchanged transfer characteristics. The electrical stability indicates that the insertion of semimetallic Sb is a promising technology for reliable Bi-based contact.

关键词： temperature stability semimetallic bismuth contact semimetallic antimony contact MoS$_{2}$ FETs time stability

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Improvement effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)on hydrogen storage performance of MgH_(2)

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Journal of Magnesium and Alloys 2024年第1期12卷 197-208页

作者： Yingyan Zhao Zhibing.liu Jiangchuan liu Yunfeng Zhu Jiguang Zhang Yana liu Xiaohui Hu Liquan Li College of Materials Science and Engineering Nanjing Tech University30 South Puzhu RoadNanjing211816PR China Jiangsu Collaborative Innovation Centre for Advanced Inorganic Function Composites Nanjing Tech UniversityNanjing211816PR China

The hydrogen absorption/desorption kinetic properties of MgH_(2)can be effectively enhanced by doping specific *** this work,MOFs-derived NiCu@C nanoparticles(~15 nm)with regular core-shell structure were successfully prepared and introduced into MgH_(2)(denoted as MgH_(2)-NiCu@C).The onset and peak temperatures of hydrogen desorption of MgH_(2)-11 wt.%NiCu@C are 175.0℃and282.2℃,*** apparent activation energy of dehydrogenated reaction is 77.2±4.5 kJ/mol for MgH_(2)-11 wt.%NiCu@C,which is lower than half of that of the as-milled MgH_(2).Moreover,MgH_(2)-11 wt.%NiCu@C displays great cyclic *** strengthening"hydrogen pumping"effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)is proposed to explain the remarkable improvement in hydrogen absorption/desorption kinetic properties of MgH_(2).This work offers a novel perspective for the design of bimetallic nanoparticles and beyond for application in hydrogen storage and other energy related fields.

关键词： Magnesium hydride Reversible solid solution Core-shell nanoparticles Hydrogen storage performance

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Design and performance investigation of modified dual reflector parabolic trough collector with double planar mirrors

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Science China(Technological Sciences) 2024年第3期67卷 902-918页

作者： LI Peijing.liu TaiXiu QIN YuanLong LI JiChao liu QiBin School of Energy Powerand Mechanical EngineeringNorth China Electric Power University Beijing 226China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Department of Thermal Science and Energy Engineering University of Science and Technology of ChinaHefei 230027China

In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber *** limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.

关键词： solar thermal energy parabolic trough collector secondary reflector solar flux distribution optical optimization

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Dynamic Simulation of Distribution Networks Using Multi-stage Discontinuous galerkin Method

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 185-196页

作者： Ruizhi Yu Wei gu Weiqi liu Peixin Li Wei liu School of Electrical Engineering Southeast UniversityNanjing 210096China. the School of Electrical Engineering Southeast UniversityNanjing 210096China School of Automation Nanjing University of Science and TechnologyNanjing 210094China

Dynamic simulation plays a fundamental role in security evaluation of distribution networks(DNs).However,the strong stiffness and non-linearity of distributed generation(Dg)models in DNs bring about burdensome computation and noteworthy instability on traditional methods which hampers the rapid response of simulation ***,a novel L-stable approximate analytical method with high accuracy is proposed to handle these *** method referred to as multistage discontinuous galerkin method(MDgM),first derives approximate analytical solutions(AASs)of state variables which are explicit symbolic expressions concerning system ***,in each time window,it substitutes values for symbolic variables and trajectories of state variables are obtained *** paper applies MDgM to Dg models to derive ***-truncation-error-based variable step size strategy is also developed to further improve simulation *** addition,this paper establishes detailed MDgM-based dynamic simulation *** case studies on a numerical problem,a modified 33-bus system and a practical large-scale DN,it can be seen that proposed method demonstrates fast and dependable performance compared with the traditional trapezoidal method.

关键词： Approximate analytical method distribution network distributed generation dynamic simulation multi-stage discontinuous galerkin method variable step size

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