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Robust interface and excellent as-built mechanical properties of Ti–6Al–4V fabricated through laser-aided additive manufacturing with powder and wire

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International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 154-168页

作者： Fei Weng Guijun Bi Youxiang Chew Shang Sui Chaolin Tan Zhenglin Du Jinlong Su Fern Lan ng Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationShandong Engineering&Technology Research Center for Superhard MaterialSchool of Materials Science and EngineeringShandong UniversityJinan 250061China Institute of Intelligent Manufacturing Guangdong Academy of SciencesGuangzhou 510095China Singapore Institute of Manufacturing Technology 5 Cleantech Loop636732Singapore

The feasibility of manufacturing Ti-6Al-4V samples through a combination of laser-aided additive manufacturing with powder(LAAM_(p))and wire(LAAM_(w))was explored.A process study was first conducted to successfully circumvent defects in Ti-6Al-4V deposits for LAAM_(p) and LAAM_(w),*** the optimized process parameters,robust interfaces were achieved between powder/wire deposits and the forged substrate,as well as between powder and wire *** characterization results revealed the epitaxial prior β grains in the deposited Ti-6Al-4V,wherein the powder deposit was dominated by a finerα′microstructure and the wire deposit was characterized by lamellar α *** mechanisms of microstructure formation and correlation with mechanical behavior were analyzed and *** mechanical properties of the interfacial samples can meet the requirements of the relevant Aerospace Material Specifications(AMS 6932)even without post heat *** fracture occurred within the interfacial area,further suggesting the robust *** findings of this study highlighted the feasibility of combining LAAM_(p) and LAAM_(w) in the direct manufacturing of Ti-6Al-4V parts in accordance with the required dimensional resolution and deposition rate,together with sound strength and ductility balance in the as-built condition.

关键词： laser-aided additive manufacturing powder deposition wire deposition interfacial characteristic mechanical behavior

Simultaneous optimization of phononic and electronic transport in two-dimensional Bi2O2Se by defect engineering

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Science China(Information Sciences) 2023年第6期66卷 87-93页

作者： Fang YAng Hong Kuan ng Jing WU Yunshan ZHAO Junpeng lu School of Physics Southeast University Institute of Materials Research and Engineering Agency for ScienceTechnology and Research NNU-SULI Thermal Energy Research Center (NSTER) & Center for Quantum Transport and Thermal Energy Science (CQTES) School of Physics and TechnologyNanjing Normal University

Defect engineering represents one degree of freedom to tune the physical and chemical properties of two-dimensional (2D)***,we demonstrate that the thermal and electronic properties of 2D Bi2O2Se can be optimized simultaneously by introducing oxygen defects.2D Bi2O2Se and its oxygendeficient counterpart (Bi2Ox Se,xng oxygen defects,the thermal conductivity of 2D Bi2O2Se is reduced by nearly three times,achieving an extremely low thermal conductivity of 0.68±0.06 W/mK at room temperature via the thermal bridge *** low thermal conductivity is enabled by the scattering of phonons by targeting of high-,mid-,and low-frequency phonons due to oxygen defects,strong anharmonicity,and nanostructure boundaries,***,the mobility is also improved to 260–500 cm2·V-1·s-1and the usual polar optical phonon scattering in 2D Bi2O2Se is weakened owing to the introduction of oxygen *** results promise potential applications for thermoelectric design,nanoelectronics,and thermal barrier coating devices based on emerging 2D materials.

关键词： 2D Bi$_2$O$_2$Se thermal conductivity oxygens defects phonon scattering mobility

Markov branching processes with killing and resurrection

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Science China Mathematics 2016年第3期59卷 573-588页

作者： CHEN An Yue lu Ying ng Kai Wang ZHAng Han Jun Department of Financial Mathematics and Financial Engineering South University of Science and Technology of China Department of Mathematical Sciences University of Liverpool Department of Statistics and Actuarial Science University of Hong Kong School of Mathematics and Computational Science Xiangtan University

In this paper, we consider Markov branching processes with killing and resurrection. We first show that the Markov branching process with killing and stable resurrection is just the Feller minimum process which is honest and thus unique. We then further show that this honest Feller minimum process is not only positive recurrent but also strongly ergodic. The generating function of the important stationary distribution is explicitly expressed. For the interest of comparison and completeness, the results of the Markov branching processes with killing and instantaneous resurrection are also briefly stated. A new result regarding strong ergodicity of this difficult case is presented. The birth and death process with killing and resurrection together with another example is also analyzed.

关键词： Markov branching processes killing stable and instantaneous resurrections uniqueness existence limiting and stationary distributions ergodicity strong ergodicity

Propagating characteristics of waves on a thin layer of mud

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Journal of Hydrodynamics 2021年第5期33卷 1078-1088页

作者： Hai-jue Xu Jin-sen Wu Yu-chuan Bai Dong-qiang lu Chiu-On ng State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China Department of Mechanical Engineering The University of Hong KongHong KongChina

The propagating characteristics of the water and muddy waves are one of the concerns of theoretical studies because of the following facts:(1)With the development of the economy in the estuaries,local residents and government paid increasing attention to the ecological environment of the estuarine beaches The propagating characteristics of the water and muddy waves are closely related to the ecological environment,the concern of the government and the residents.(2)The propagating characteristics of the mud are the bottleneck of the study of the coastal and beach dynamics because of the complicated constitutive relation of the *** different constitutive models may lead to different explanations of its ***,the proper selection of the model is one of the keys to reveal the true kinematic properties of the mud in the *** paper first establishes a power law model of the constitutive relation of the *** on this model,a gravity wave theory is *** to the mechanism of the mud wave transportation,the coupled mud-water wave field can be divided into two *** upper layer is described as the viscous Newtonian fluid,whereas the lower high-concentration mud layer is described as the power law ***,the equations of the proposed model are discretized and the calculations are made by using the difference ***,the propagating characteristics are discussed,and the dispersion relations of the water and mud waves are analyzed in detail.

关键词： Estuary two-layer fluid model power law model gravity wave Introduction

Prediction of fracture initiation in cohesive soils based on data mining modelling and large-scale laboratory verification

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Underground Space 2024年第6期19卷 279-300页

作者： Weiping luo Dajun Yuan Yannick Choy Hing ng Dalong Jin Ping lu Teng Wang Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China Key Laboratory of the Ministry of Education for Urban Underground Engineering Beijing Jiaotong UniversityBeijing 100044China Department of Civil and Environmental Engineering National University of SingaporeSingapore 119077Singapore

Many empirical and analytical methods have been proposed to predict fracturing pressure in cohesive *** of them take into account three to four specific influencing factors and rely on the assumption of a failure *** this study,a novel data-mining approach based on the XGBoost algorithm is investigated for predicting fracture initiation in cohesive *** has the advantage of handling multiple influencing factors simultaneously,without pre-determining a failure mode.A dataset of 416 samples consisting of 14 distinct features was herein collected from past studies,and used for developing a regressor and a classifier model for fracturing pressure prediction and failure mode classification *** results show that the intrinsic characteristics of the soil govern the failure mode while the fracturing pressure is more sensitive to the stress *** XGBoost-based model was also tested against conventional approaches,as well as a similar machine learning algorithm namely random forest ***,several large-scale triaxial fracturing tests and an in-situ case study were carried out to further verify the generalization ability and applicability of the proposed data mining approach,and the results indicate a superior performance of the XGBoost model.

关键词： Fracturing pressure Failure mode Cohesive soil Data-mining Large-scale tests

Fabrication and Characterization of Ca-Mg-P Containing Coating on Pure Magnesium

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Journal of Materials Science & Technology 2012年第7期28卷 636-641页

作者： Yanjin lu Lili Tan Honglia. ng Xiang Bingchun Zhang Ke Yang Yangde Li Institute of Metal Researchl Chinese Academy of Sciences -Shenyang 110016 China School of Mechanical Engineering and Automation Fuzhou University ~zhou 350108 China Dongguan EONTEC Co. Ltd. Dongguan 523662 China

A biodegradable Ca-P coating mainly consisting of β-tricalcium phosphate （β-TCP） was fabricated on pure magnesium via the chemical deposition in a simulated Hank’s solution. The method significantly accelerated the coating formation on magnesium. Moreover, the morphology, phase/chemical composition, the coating formation mechanism as well as degradation behavior in phosphate buffered saline （PBS） solution were in- vestigated. Scanning electron microscopy （SEM） images showed that the coating had three layers and X-ray diffraction （XRD） patterns showed that the coating mainly contained Ca3（PO4）2 and （Ca,Mg）3（PO4）2. Elec- trochemical test showed that the corrosion current density （Icorr） of the coated Mg was decreased by about one order of magnitude as compared to that of pure magnesium. The immersion test indicated that the coating could obviously reduce the degradation rate.

关键词： Magnesium β-tricalcium phosphate (β-TCP) Biodegradation Chemicaldeposition

Visualization of Wormlike Micelle Fluid Flow in a Mixing Tank

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Transactions of Tianjin University 2018年第4期24卷 308-317页

作者： Hongyuan Wei Jieliang lu Chong Gu Kate Xu Boonho ng Leping Dang School of Chemical Engineering and Technology Tianjin UniversityTianjin 300350China Procter&Gamble Technology(Beijing)Co. LtdBeijing 101312China

In this study,particle image velocimetry was applied to investigate flow fields of wormlike micelle(WLM) fluids in a mixing tank equipped with a four-blade,down-pumping,pitched blade turbine. First,the rheology of WLM fluids was investigated,and the Carreau model was utilized to describe their apparent viscosity. Then,the effects of the rotation speeds and rheological properties on the flow fields were studied using different WLM fluids at different rotation speeds. The results revealed that with increasing Reynolds number,the discharge angle decreases and the carven size increases. Furthermore,elastic effects of WLM fluids lead to a more curved flow and a smaller carven.

关键词： Wormlike micelle PIV Mixing Flow fi eld

NUMERICAL SIMULATION OF THE DISPERSION IN OSCILLATIng FLOWS WITH REVERSIBLE AND IRREVERSIBLE WALL REACTIONS

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Journal of Hydrodynamics 2009年第4期21卷 482-490页

作者： ZHAng Dao-xiang lu Zhi-ming LIU Yu-lu ng Chiu-On Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China College of Mathematics and Computer Science Anhui Normal University Wuhu 241000 China Department of Mechanical Engineering The University of Hong Kong Hong Kong China

This is a study on the mass transport of a solute or contaminant in oscillating flows through a circular tube with a reactive wall layer. The reaction consists of a reversible component due to phase exchange between the flowing fluid and the wall layer, and an irreversible component due to absorption into the wall. The short-time dispersion characteristics are numerically investigated, incorporating the coupling effects between the flow oscillation, sorption kinetics, and retardation due to phase partitioning. The effects of various dimensionless parameters e.g., Da （the Damkoehler number）, α （phase partitioning number）, F （dimensionless absorption number）, and δ （dimensionless Stokes boundary layer number） on dispersion are discussed. In particular, it is found that there exist trinal peaks of the breakthrough curves in some cases.

关键词： dispersion flow oscillation wall reactions

Tree pruning for MIMO sphere detection based on MMSE detection

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The Journal of China Universities of Posts and Telecommunications 2012年第4期19卷 64-72页

作者： WAng Shi-liang SUN Song-lin J1ng Xiao-jun lu Yue-ming School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China Key Laboratory of Trustworthy Distributed Computing and Service Ministry of EducationBeijing University of Posts and TelecommunicationsBeijing 100876China

Tree pruning is an effective algorithm to reduce the complexity of sphere detection （SD） for multiple-input multiple-output （MIMO） communication systems. How to determine the tree pruning rule, as well as by what the tradeoff between the performance and the complexity can be achieved, is still an open problem. In this paper, a tree pruning algorithm is proposed based on minimum mean square error （MMSE） detection. The proposed algorithm first preforms MMSE detection since the complexity of MMSE detection is very low. Then the pruning constraints will be set according to the scaled path metrics of the MMSE solution. The choice of the scale factors and their influences on the complexity and performance are also discussed. Through analysis and simulations, it is shown that the complexity is reduced significantly with negligible performance degradation and additional computations.

关键词： MIMO sphere detection tree pruning MMSE detection