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A study of the effect of local scour on the flow field near the spur dike

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Theoretical & Applied Mechanics Letters 2024年第2期14卷 98-105页

作者： Yu-tian Li Jie-Min Zhan Wing-hong Onyx Wai Department of Industrial Design School of Industrial Design and Ceramic ArtFoshan UniversityFoshan 528000China Department of Applied Mechanics and Engineering Shenzhen Campus of Sun Yat-sen UniversityShenzhen 518107China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China

The flow field near a spur dike such as down flow and horseshoe vortex system(HVS)are susceptible to the topographic changes in the local scouring process,resulting in variation of the sediment transport with *** this study,large eddy simulations with fixed-bed at different scouring stages were conducted to investigate the changes in flow *** results imply that the bed deformation leads to an increase in flow rate per unit area,which represent the capability of sediment transportation by water,in the scour ***,the intensity of turbulent kinetic energy and bimodal motion near the sand bed induced by the HVS were also ***,the peak moments between the two sediment transport mechanisms were ***,understanding the complex feedback mechanism between topography and flow field is essential for the local scour problem.

关键词： Spur dike Local scour Large eddy simulation Down flow Horseshoe vortex system

Protective effects of baffles with different positions,row spacings,heights on debris flow impact

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Journal of Mountain Science 2024年第7期21卷 2352-2367页

作者： SUN Xinpo CHEN Min BI Yuzhang ZHENG Lu CHE chi XU Ao tian Zijian JIANG Zheyuan College of Civil Engineering Sichuan University of Science and EngineeringZigong 643000China College of Resources and Environment Fujian Agriculture and Forestry UniversityFuzhou 350002China School of Civil Engineering Fuzhou UniversityFuzhou 350108China Jiangsu Key Laboratory of Urban Underground Engineering&Environmental Safety Institute of Geotechnical EngineeringSoutheast UniversityNanjing 210096China Beijing Urban Construction Science Technology Promoting Association Beijing 100055China SUSE-BZ Geoenvironmental Engineering Joint Laboratory Sichuan University of Science and EngineeringZigong 643000China

The baffle effectively slowed down debris flow velocity,reduced its kinetic energy,and significantly shortened the distance of debris flow ***,they are widely used for protection against natural hazards such as landslides and *** study,based on the threedimensional DEM(Discrete Element Method),investigated the impact of different baffle positions on debris flow *** flow velocity and kinetic energy variations were studied through single-factor *** baffle positions were preliminarily selected by analyzing the influence of the first-row baffle position on the impact force and accumulation mass of debris ***,based on the selected baffle positions and four factors influencing the effectiveness of baffle protection(baffle position(P),baffle height(h),row spacing(S_(r)),and angle of transit area(α)),an orthogonal design was employed to further explore the optimal arrangement of *** research results indicate that the use of a baffle structure could effectively slow down the motion velocity of debris flows and dissipate their *** the baffle is placed in the transit area,the impact force on the first-row baffle is greater than that when the baffle is placed in the deposition ***,when the baffle is placed in the transit area,the obstruction effect on debris flow mass is also greater than that when the baffle is placed in the deposition *** orthogonal experimental range analysis,when the impact on the first row of baffles is used as the evaluation criterion,the importance of each influencing factor is ranked asα>P>S_(r)>*** the mass of debris flow behind the baffle is regarded as the evaluation criterion,the rank is changed to P>α>S_(r)>*** experimental simulation results show that the optimal baffle arrangement is:P_(5),S_(r)=16,α=35°,h=9.

关键词： Debris flow Baffle Protective effect Discrete element

High-throughput calculations combining machine learning to investigate the corrosion properties of binary Mg alloys

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Journal of Magnesium and Alloys 2024年第4期12卷 1406-1418页

作者： Yaowei Wang tian Xie Qingli Tang Mingxu Wang Tao Ying hong Zhu Xiaoqin Zeng University of Michigan-Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong University200240ShanghaiChina State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai200240China

Magnesium(Mg)alloys have shown great prospects as both structural and biomedical materials,while poor corrosion resistance limits their further *** this work,to avoid the time-consuming and laborious experiment trial,a high-throughput computational strategy based on first-principles calculations is designed for screening corrosion-resistant binary Mg alloy with intermetallics,from both the thermodynamic and kinetic *** stable binary Mg intermetallics with low equilibrium potential difference with respect to the Mg matrix are firstly ***,the hydrogen adsorption energies on the surfaces of these Mg intermetallics are calculated,and the corrosion exchange current density is further calculated by a hydrogen evolution reaction(HER)kinetic *** intermetallics,e.g.Y_(3)Mg,Y_(2)Mg and La_(5)Mg,are identified to be promising intermetallics which might effectively hinder the cathodic ***,machine learning(ML)models are developed to predict Mg intermetallics with proper hydrogen adsorption energy employing work function(W_(f))and weighted first ionization energy(WFIE).The generalization of the ML models is tested on five new binary Mg intermetallics with the average root mean square error(RMSE)of 0.11 *** study not only predicts some promising binary Mg intermetallics which may suppress the galvanic corrosion,but also provides a high-throughput screening strategy and ML models for the design of corrosion-resistant alloy,which can be extended to ternary Mg alloys or other alloy systems.

关键词： Mg intermetallics Corrosion property High-throughput Density functional theory Machine learning

Enhancing personalized exercise recommendation with student and exercise portraits

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Journal of Electronic Science and Technology 2024年第2期22卷 91-109页

作者： Wei-Wei Gao Hui-Fang Ma Yan Zhao Jing Wang Quan-hong tian College of Computer Science and Engineering Northwest Normal UniversityLanzhou730070China Computer Center of Gansu Province Lanzhou730070China

The exercise recommendation system is emerging as a promising application in online learning scenarios,providing personalized recommendations to assist students with explicit learning *** solutions generally follow a collaborative filtering paradigm,while the implicit connections between students(exercises)have been largely *** this study,we aim to propose an exercise recommendation paradigm that can reveal the latent connections between student-student(exercise-exercise).Specifically,a new framework was proposed,namely personalized exercise recommendation with student and exercise portraits(PERP).It consists of three sequential and interdependent modules:Collaborative student exercise graph(CSEG)construction,joint random walk,and recommendation list ***,CSEG is created as a unified heterogeneous graph with students’response behaviors and student(exercise)***,a joint random walk to take full advantage of the spectral properties of nearly uncoupled Markov chains is performed on CSEG,which allows for full exploration of both similar exercises that students have finished and connections between students(exercises)with similar ***,we propose to optimize the recommendation list to obtain different exercise *** analyses of two public datasets,the results demonstrated that PERP can satisfy novelty,accuracy,and diversity.

关键词： Educational data mining Exercise recommend Joint random walk Nearly uncoupled Markov chains Optimization Personalized learning

An aqueous magnesium-ion hybrid supercapacitor operated at-50℃

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Green Energy & Environment 2024年第4期9卷 702-712页

作者： Guoshen Yang Gangrui Qu chi Fang Jie Deng Xianqi Xu Yinghao Xie tian Sun Yachao Zhu Jiaxin Zheng Hang Zhou School of Electronic and Computer Engineering Peking University Shenzhen Graduate SchoolShenzhen518055China School of Advanced Materials Peking University Shenzhen Graduate SchoolShenzhenChina College of Food and Biological Engineering Chengdu UniversityChengdu610106China Institute Charles Gerhardt Montpellier UMR 5253Universitae MontpellierMontpellierCC 1502France

The recent advances in aqueous magnesium-ion hybrid supercapacitor(MHSC)have attracted great attention as it brings together the benefits of high energy density,high power density,and synchronously addresses cost and safety ***,the freeze of aqueous electrolytes discourages aqueous MHSC from operating at low-temperature ***,a low-concentration aqueous solution of 4 mol L^(-1) Mg(ClO_(4))_(2) is devised for its low freezing point(-67℃)and ultra-high ionic conductivity(3.37 mS cm^(-1) at-50℃).Both physical characterizations and computational simulations revealed that the Mg(ClO_(4))_(2) can effectively disrupt the original hydrogen bond network among water molecules via transmuting the electrolyte structure,thus yielding a low freezing ***,the Mg(ClO_(4))_(2) electrolytes endue aqueous MHSC with a wider temperature operation range(-50℃–25℃)and a higher energy density of 103.9 Wh kg^(-1) at 3.68 kW kg^(-1) over commonly used magnesium salts(i.e.,MgSO_(4) and Mg(NO_(3))_(2))***,a quasi-solid-state MHSC based on polyacrylamide-based hydrogel electrolyte holds superior low-temperature performance,excellentﬂexibility,and high *** work pioneers a convenient,cheap,and eco-friendly tactic to procure low-temperature aqueous magnesium-ion energy storage device.

关键词： Low-concentration aqueous electrolyte Anti-freezing property Magnesium-ion hybrid supercapacitor High energy density

Orientational growth behavior and mechanism of delta(δ)phase precipitation in cold-rolled Inconel 718 alloy during heat treatment

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Journal of Iron and Steel Research International 2024年第1期31卷 264-274页

作者： Neng-yong Ye Guang-liang Zhang tian-yue Huang Ming Cheng Shi-hong Zhang Lei Wang School of Materials Science&Engineering Taizhou UniversityTaizhou318000ZhejiangChina Institute of Metal Research Chinese Academy of SciencesShenyang110016LiaoningChina

Due to the important role ofδphase's quantity and morphology in the mechanical and fatigue properties of Inconel 718 alloy and its components,it is necessary to renew insights into the effect of cold deformation on theδphase precipitation,especially on the morphology ***,the nucleation and growth behavior ofδphase in cold-rolled Inconel 718 alloy during aging were *** results show that the precipitation rate and volume fraction ofδphase increase with increasing the cold rolling reduction from 10%to 50%.The volume fraction ofδphase reaches equilibrium after 5 h,remaining at 5.98%,6.52%,and 6.79%under different rolling reductions(10%,30%,and 50%),*** nucleation ofδphase mainly occurs on different sites(grain boundaries,new twin boundaries and old twin boundaries)under 10%rolling reduction,whileδphase mainly nucleates on the new grain boundaries of static recrystallization due to 50%rolling *** the growth ofδphase undergoes a process of alternate orientation growth from spherical(nucleation)→short rod(longitudinal orientation growth)→short rod(radial orientation growth)→dynamic *** 10%rolling reduction,δphase tends to grow into the matrix,while under 50%rolling reduction,the orientation grows faster and is easily affected by the grain boundary curvature.

关键词： Inconel 718 alloy Cold rolling δphase Orientation growth Morphology evolution

Harmonic State Space Based Impedance Modeling and Virtual Impedance Based Stability Enhancement Control for LCC-HVDC Systems

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 287-298页

作者： Yifeng Liu Xiaoping Zhou Quan Chen Hanhang Yin Lerong hong Hao tian Ying Chen Siyuan Li the College of Electrical and Information Engineering Hunan UniversityChangsha 410082China the Zhejiang Magtron Intelligent Technology Limited Cooperation Jiaxing 314000China the State Grid Qianjiang Electric Power Company Qianjiang 433100China

Line commutated converter based high-voltage direct-current(LCC-HVDC)transmissions are prone to harmonic oscillation under weak *** modeling is an effective method for assessing interaction ***,this paper proposes an improved calculation method for the DC voltage and AC currents of commutation stations to address the complex linearization of the commutation process and constructs an overall harmonic state-space(HSS)model of an *** on the HSS model,the closed-loop AC impedances on the LCC-HVDC sending and receiving ends are then derived and *** impedance characteristics of the LCC-HVDC are then analyzed to provide a physical explanation for the harmonic oscillation of the *** effects of the grid strength and control parameters on system stability are also *** improve the impedance characteristics and operating stability of the LCC-HVDC system,a virtual impedance based stability enhancement control is proposed,and a parameter design method is considered to ensure satisfactory phase margins at both the sending and receiving ***,simulation results are presented to verify the validity of the impedance model and virtual impedance based stability enhancement control.

关键词： Line commutated converter based high-voltage direct-current(LCC-HVDC)transmission harmonic state space stability analysis harmonic oscillation virtual impedance

W^(m,p(t,x))-Estimate for a Class of Higher-Order Parabolic Equations with Partially BMO Coefficients

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Journal of Partial Differential Equations 2024年第2期37卷 198-234页

作者： tian hong HAO Shuai ZHENG Shenzhou College of Science Tianjin University of TechnologyTianjin 300384China Department of Mathematics Beijing Jiaotong UniversityBeijing 100044China

We prove a global estimate in the Sobolev spaces with variable exponents to the solution of a class of higher-order divergence parabolic equations with measurable coefficients over the non-smooth ***,it is mainly assumed that the coefficients are allowed to be merely measurable in one of the spatial variables and have a small BMO quasi-norm in the other variables at a sufficiently small scale,while the boundary of the underlying domain belongs to the so-called Reifenberg *** is a natural outgrowth of Dong-Kim-Zhang’s papers[1,2]from the W^(m,p)-regularity to the W^(m,p(t,x))-regularity for such higher-order parabolic equations with merely measurable coefficients with Reifenberg flat domain which is beyond the Lipschitz domain with small Lipschitz constant.

关键词： A higher-order parabolic equation Sobolev spaces with variable exponents partially BMO quasi-norm Reifenberg flat domains log-Hölder continuity

A Review of Type 1 and Type 2 Intraductal Papillary Neoplasms of the Bile Duct

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Current Medical Science 2024年第3期44卷 485-493页

作者： Xia-hui HUANG tian-xiang CHEN hong-liang LIU Ming-wen HUANG Department of General Surgery The Second Affiliated Hospital of Nanchang UniversityNanchang330006China

Intraductal papillary neoplasm of the bile duct(IPNB)is a heterogeneous disease similar to intraductal papillary mucinous neoplasm of the *** lesions have been recognized as one of the three major precancerous lesions in the biliary tract since *** 2018,Japanese and Korean pathologists reached a consensus,classifying IPNBs into type l and type 2 *** are more prevalent in male patients in East Asia and are closely related to diseases such as cholelithiasis and *** a molecular genetic perspective,IPNBs exhibit early genetic variations,and different molecular pathways may be involved in the tumorigenesis of type 1 and type 2 *** histological subtypes of IPNBs include gastric,intestinal,pancreaticobiliary,or oncocytic subtypes,but type 1 IPNBs typically exhibit more regular and well-organized histological features than type 2 IPNBs and are more commonly found in the intrahepatic bile ducts with abundant *** to the rarity of these lesions and the absence of specific clinical and laboratory features,imaging is crucial for the preoperative diagnosis of IPNB,with local bile duct dilation and growth along the bile ducts being the main imaging *** resection remains the optimal treatment for IPNBs,but negative bile duct margins and the removal of lymph nodes in the hepatic hilum significantly improve the postoperative survival rates for patients with IPNBs.

关键词： intraductal papillary neoplasm of the bile duct subclassification neoplasms precancerous tissue prognosis