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Scale properties of turbulent transport and coherent structure in stably stratified flows

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Applied Mathematics and Mechanics(English Edition) 2016年第4期37卷 443-458页

作者： long zhu Xiang QIU Jianping LUO Yulu LIU School of Mechanical Engineering Shanghai Institute of Technology School of Science Shanghai Institute of Technology Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

The empirical mode decomposition （EMD） is used to study the scale properties of turbulent transport and coherent structures based on velocity and temperature time series in stably stratified turbulence. The analysis is focused on the scale properties of intermittency and coherent structures in different modes and the contributions of energy-contained coherent structures to turbulent scalar counter-gradient transport （CGT）. It is inferred that the velocity intermittency is scattered to more modes with the development of the stratified flow, and the intermittency is enhanced by the vertical stratification, especially in small scales. The anisotropy of the field is presented due to different time scales of coherent structures of streamwise and vertical velocities. There is global counter-gradient heat transport close to the turbulence-generated grid, and there is local counter-gradient heat transport at certain modes in different positions. Coherent structures play a principal role in the turbulent vertical transport of temperature.

关键词： stratified turbulence coherent structure counter-gradient transport (CGT),empirical mode decomposition (EMD)

Label fusion for segmentation via patch based on local weighted voting

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Frontiers of Information Technology & Electronic Engineering 2017年第5期18卷 680-688页

作者： Kai zhu Gang LIU long ZHAO Wan ZHANG School of Automation Engineering Shanghai University of Electrical Power Athinoula A.Martinos Center for Biomedical Imaging Massachusetts General HospitalHarvard Medical School

Label fusion is a powerful image segmentation strategy that is becoming increasingly popular in medical imaging. However, satisfying the requirements of higher accuracy and less running time is always a great challenge. In this paper we propose a novel patch-based segmentation method combining a local weighted voting strategy with Bayesian inference. Multiple atlases are registered to a target image by an advanced normalization tools(ANTs) algorithm. To obtain a segmentation of the target, labels of the atlas images are propagated to the target image. We first adopt intensity prior and label prior as two key metrics when implementing the local weighted voting scheme, and then compute the two priors at the patch level. Further, we analyze the label fusion procedure concerning the image background and take the image background as an isolated label when estimating the label prior. Finally, by taking the Dice score as a criterion to quantitatively assess the accuracy of segmentations, we compare the results with those of other methods, including joint fusion, majority voting, local weighted voting, majority voting based on patch, and the widely used Free Surfer whole-brain segmentation tool. It can be clearly seen that the proposed algorithm provides better results than the other methods. During the experiments, we make explorations about the influence of different parameters(including patch size, patch area, and the number of training subjects) on segmentation accuracy.

关键词： Label fusion Local weighted voting Patch-based Background analysis

Global Optimization Method Using SLE and Adaptive RBF Based on Fuzzy Clustering

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Chinese Journal of Mechanical Engineering 2012年第4期25卷 768-775页

作者： zhu Huaguang LIU Li long Teng ZHAO Junfeng School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China

High fidelity analysis models,which are beneficial to improving the design quality,have been more and more widely utilized in the modern engineering design optimization ***,the high fidelity analysis models are so computationally expensive that the time required in design optimization is usually *** order to improve the efficiency of optimization involving high fidelity analysis models,the optimization efficiency can be upgraded through applying surrogates to approximate the computationally expensive models,which can greately reduce the computation *** efficient heuristic global optimization method using adaptive radial basis function（RBF） based on fuzzy clustering（ARFC） is *** this method,a novel algorithm of maximin Latin hypercube design using successive local enumeration（SLE） is employed to obtain sample points with good performance in both space-filling and projective uniformity properties,which does a great deal of good to metamodels *** method is adopted for constructing the metamodels,and with the increasing the number of sample points the approximation accuracy of RBF is gradually *** fuzzy c-means clustering method is applied to identify the reduced attractive regions in the original design *** numerical benchmark examples are used for validating the performance of *** results demonstrates that for most application examples the global optima are effectively obtained and comparison with adaptive response surface method（ARSM） proves that the proposed method can intuitively capture promising design regions and can efficiently identify the global or near-global design *** method improves the efficiency and global convergence of the optimization problems,and gives a new optimization strategy for engineering design optimization problems involving computationally expensive models.

关键词： global optimization Latin hypercube design radial basis function fuzzy clustering adaptive response surface method

Effects of vertical excitation on the seismic performance of a seismically isolated bridge with sliding friction bearings

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Earthquake Engineering and Engineering Vibration 2016年第1期15卷 187-196页

作者： Wang Changfeng Zhao Jikang zhu long Bao Yijun School of Civil Engineering Yantai University School of Civil Engineering Lanzhou Jiaotong University

A finite element model is constructed for a sliding friction bearing in a seismically isolated bridge under vertical excitation with contact/friction elements. The effects of vertical excitation on the seismic performance of a seismically isolated bridge with sliding friction bearings and different bearing friction coefficients and different stiffness levels （pier diameter） are discussed using example calculations, and the effects of excitation direction for vertical excitation on the analysis results are explored. The analysis results shows that vertical excitation has a relatively large impact on seismic performance for a seismically isolated bridge with sliding friction bearings, which should be considered when designing a seismically isolated bridge with sliding friction bearings where vertical excitation dominates.

关键词： vertical excitation seismically isolated bridge sliding friction bearing seismic analysis

Electrochemical migration behavior of Ag-plated Cu-filled electrically conductive adhesives

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Rare Metals 2012年第1期31卷 64-70页

作者： zhu, Xiaoyun Liu, Yuanlong long, Jinming Liu, Xiaoli School of Materials Science and Engineering Kunming University of Science and Technology Kunming 650093 China Faculty of Metallurgy and Energy Engineering Kunming University of Science and Technology Kunming 650093 China

The electrochemical migration (ECM) behavior of the electrically conductive adhesives (ECAs) filled with pure Ag powder or Ag-plated Cu composite powder with varied Ag:Cu ratios was investigated under the condition of applying constant voltage and distilled water *** resistance was determined from the current-time *** microstructure and composition of ECM dendrite products were analyzed by SEM/EDS and *** was found that the ECM resistance of Ag-plated Cu composite powder-filled ECAs was evidently higher than that of pure Ag powder-filled *** Ag:Cu ratio of composite powder in ECAs had notable influence on ECM resistance,which was enhanced with the decrease of Ag:Cu *** composition of dendrites formed between cathode and anode during ECM process was not uniform for Ag-plated Cu-filled *** ECM inhibiting mechanism of Ag-plated Cu composite powder was proposed according to analysis of the electrochemical impedance spectroscopy,Tafel plot and dendrite composition.

关键词： composite material electrochemical migration Ag-plated Cu composite powder electrically conductive adhesives

Applications of magnetic nanoparticles in surface-enhanced Raman scattering(SERS)detection of environmental pollutants

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Journal of Environmental Sciences 2019年第6期31卷 14-34页

作者： Dan Song Rong Yang Feng long Anna zhu School of Environment and Natural Resources Renmin University of China Research Institute of Chemical Defense Academy of Military Sciences PLA China State Key Laboratory of NBC Protection FOR Civilian

Environmental pollution, a major problem worldwide, poses considerable threat to human health and ecological environment. Efficient and reliable detection technologies, which focus on the appearance of emerging environmental and trace pollutants, are urgently needed. Surface-enhanced Raman scattering(SERS) has become an attractive analytical tool for sensing trace targets in environmental field because of its inherent molecular fingerprint specificity and high sensitivity. In this review, we focused on the recent developments in the integration of magnetic nanoparticles(MNPs) with SERS for facilitating sensitive detection of environmental pollutants. An overview and classification of different types of MNPs for SERS detection were initially provided, enabling us to categorize the huge amount of literature that was available in the interdisciplinary research field of MNPs based SERS technology. Then, the basic working principles and applications of MNPs in SERS detection were presented. Subsequently, the detection technologies integrating MNPs with SERS that eventually were used for the detection of various environmental pollutions were reviewed. Finally, the advantages of MNP-basedSERS detection technology for environmental pollutants were concluded, and the current challenges and future outlook of this technology in practical applications were highlighted. The application of the MNPsbasedSERS techniques for environmental analysis will be significantly advanced with the great progresses of the nanotechnologies, optics, and materials.

关键词： Magnetic nanoparticles Surface-enhanced Raman scattering SERS substrates Environmental pollutant detection

Multi-UAV reconnaissance task allocation for heterogeneous targets using an opposition-based genetic algorithm with double-chromosome encoding

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Chinese Journal of Aeronautics 2018年第2期31卷 339-350页

作者： zhu WANG Li LIU Teng long Yonglu WENa School of Aerospace Engineering Beijing Institute of Technology Key Laboratory of Dynamics and Control of Flight Vehicle Ministry of Education

This paper presents a novel multiple Unmanned Aerial Vehicles（UAVs） reconnaissance task allocation model for heterogeneous targets and an effective genetic algorithm to optimize UAVs＇ task sequence. Heterogeneous targets are classified into point targets, line targets and area targets according to features of target geometry and sensor＇s field of view. Each UAV is regarded as a Dubins vehicle to consider the kinematic constraints. And the objective of task allocation is to minimize the task execution time and UAVs＇ total consumptions. Then, multi-UAV reconnaissance task allocation is formulated as an extended Multiple Dubins Travelling Salesmen Problem（MDTSP）, where visit paths to the heterogeneous targets must meet specific constraints due to the targets＇ feature. As a complex combinatorial optimization problem, the dimensions of MDTSP are further increased due to the heterogeneity of targets. To efficiently solve this computationally expensive problem, the Opposition-based Genetic Algorithm using Double-chromosomes Encoding and Multiple Mutation Operators（OGA-DEMMO） is developed to improve the population variety for enhancing the global exploration capability. The simulation results demonstrate that OGADEMMO outperforms the ordinary genetic algorithm, ant colony optimization and random search in terms of optimality of the allocation results, especially for large scale reconnaissance task allocation problems.

关键词： Unmanned aerial vehicles Task allocation Genetic algorithm Travelling salesman problems Dubins vehicles

Variable-K double trenches SOI LDMOS with high-concentration P-pillar

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Chinese Physics B 2020年第5期29卷 498-503页

作者： Lijuan Wu Lin zhu xing Chen The Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering School of Physics&Electronic ScienceChangsha University of Science&TechnologyChangsha 410114China

A variable-K trenches silicon-on-insulator(SOI)lateral diffused metal-oxide-semiconductor field-effect transistor(MOSFET)with a double conductive channel is proposed based on the enhancement of low dielectric constant media to electric *** device features variable-K dielectric double trenches and a P-pillar between the trenches(VK DT-P LDMOS).The low-K dielectric layer on the surface increases electric field of *** a variable-K material introduces a new electric field peak to the drift region,so as to optimize electric field inside the *** of the high-concentration vertical P-pillar between the two trenches effectively increases doping concentration of the drift region and maintains charge balance inside ***,breakdown voltage(BV)of the device is *** double conductive channels provide two current paths that significantly reduce specific on-resistance(Ron,sp).Simulation results demonstrate that a 17-μm-length device can achieve a BV of 554 V and a low on-resistance of 13.12 mΩ·cm^*** Ron,sp of VK DT-P LDMOS is reduced by 78.9%compared with the conventional structure.

关键词： variable-K(VK) trench technology specific on-resistance(Ron,sp) breakdown voltage(BV)

Verification of neutron-induced fission product yields evaluated by a tensor decompsition model in transport-burnup simulations

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Nuclear Science and Techniques 2023年第2期34卷 190-201页

作者： Qu‑Fei Song long zhu Hui Guo Jun Su School of Nuclear Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Sino‑French Institute of Nuclear Engineering and Technology Sun Yat-sen UniversityZhuhai 519082China

Neutron-induced fission is an important research object in basic ***,its product yield data are an indispensable nuclear data basis in nuclear engineering and *** fission yield tensor decomposition(FYTD)model has been developed and used to evaluate the independent fission product *** general,fission yield data are verified by the direct comparison of experimental and evaluated ***,such direct comparison cannot reflect the impact of the evaluated data on application scenarios,such as reactor transport-burnup ***,this study applies the evaluated fission yield data in transport-burnup simulation to verify their accuracy and possibility of ***,the evaluated yield data of235U and239Pu are applied in the transport-burnup simulation of a pressurized water reactor(PWR)and sodium-cooled fast reactor(SFR)for *** the reactor operation stage,the errors in pin-cell reactivity caused by the evaluated fission yield do not exceed 500 and 200 pcm for the PWR and SFR,*** errors in decay heat and135Xe and149Sm concentrations during the short-term shutdown of the PWR are all less than 1%;the errors in decay heat and activity of the spent fuel of the PWR and SFR during the temporary storage stage are all less than 2%.For the PWR,the errors in important nuclide concentrations in spent fuel,such as90Sr,137Cs,85Kr,and99Tc,are all less than 6%,and a larger error of 37%is observed *** the SFR,the concentration errors of ten important nuclides in spent fuel are all less than 16%.A comparison of various aspects reveals that the transport-burnup simulation results using the FYTD model evaluation have little difference compared with the reference results using ENDF/B-Ⅷ.0 *** proves that the evaluation of the FYTD model may have application value in reactor physical analysis.

关键词： Fission product yield Tensor decomposition Transport-burnup simulation Machine learning