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Two possible mechanisms for vortex self-organization

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Science china Earth Sciences 2006年第2期49卷 202-211页

作者： LUO Zhexian2, ZHOU Xiuji1 & GAO Shouting3.1. Chinese Academy of Meteorological Sciences, beijing 100081, china 2. department of Space Information Science, Nanjing University of Information Science and Technology, Nanjing 210044, china 3. Institute of Atmospheric physics, Chinese Academy of Sciences, beijing 100029, china 2. department of Environmental Science Nanjing University of Information Science and Technology Nanjing 210044 China 1. Chinese Academy of Meteorological Sciences Beijing 100081 China 3. Institute of Atmospheric physics Chinese Academy of Sciences Beijing 100029 China

The vortex self-organization is investigated in this paper by four groups of numerical experiments within the framework of quasi-geostrophic model, and based on the experimental results two types of possible mechanisms for vortex self-organization are suggested. The meso-scale to-pography may enable separated vortices to merge into a larger scale vortex; and the interaction of meso-γ and meso-β scale systems may make separated vortices to self organize a typhoon-like vor-tex circulation.

关键词： vortex, self-organization, meso-scale topography, interaction of different scales.

Recommendation Method for Contrastive Enhancement of Neighborhood Information

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Computers, Materials & Continua 2024年第1期78卷 453-472页

作者： Hairong Wang beijing Zhou Lisi Zhang He Ma School of Computer Science and Engineering North Minzu UniversityNingxia750021China

Knowledge graph can assist in improving recommendation performance and is widely applied in various person-alized recommendation ***,existing knowledge-aware recommendation methods face challenges such as weak user-item interaction supervisory signals and noise in the knowledge *** tackle these issues,this paper proposes a neighbor information contrast-enhanced recommendation method by adding subtle noise to construct contrast views and employing contrastive learning to strengthen supervisory signals and reduce knowledge ***,first,this paper adopts heterogeneous propagation and knowledge-aware attention networks to obtain multi-order neighbor embedding of users and items,mining the high-order neighbor informa-tion of users and ***,in the neighbor information,this paper introduces weak noise following a uniform distribution to construct neighbor contrast views,effectively reducing the time overhead of view *** paper then performs contrastive learning between neighbor views to promote the uniformity of view information,adjusting the neighbor structure,and achieving the goal of reducing the knowledge noise in the knowledge ***,this paper introduces multi-task learning to mitigate the problem of weak supervisory *** validate the effectiveness of our method,experiments are conducted on theMovieLens-1M,MovieLens-20M,Book-Crossing,and Last-FM *** results showthat compared to the best baselines,our method shows significant improvements in AUC and F1.

关键词： Contrastive learning knowledge graph recommendation method

Evaluation of Surface Cracks Using Magnetic Flux LeakageTesting

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Journal of Materials Science & Technology 2002年第4期18卷 319-321页

作者： Luming LI, Songling HUANG, Peng ZHENG and Keren SHINUT Center, Mechanical Engineering department, tsinghua University, beijing 100084, {3. NDT Cent. Mech. Eng. Dept. Tsinghua Univ. Beijing 100084 China

The magnetic field distribution characteristics of surface cracks with various widths are discussed based on finite element (FEM) results. The crack depth was 0.20 mm, the width range was from 0.02 to 1.00 mm. The results showed that crack width and lift-off (the distance between surface and sensor) will influence signals. Discussed in this paper is the influence of various lift-off parameters on the peak to peak values of the normal component in magnetic flux leakage testing. The effects can be applied to evaluate surface breaking cracks of different widths and depths. An idea is presented to smooth narrow, sharp crack tips using alternating current (AC) field magnetization.

关键词： Magnetic flux leakage testing (MFL) Slot width Finite element method (FKM)

The application of event-tree based approach in long-term crude oil scheduling

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Science china Chemistry 2010年第6期53卷 1445-1452页

作者： ZOU LaiXi,LI ChuFu,ZHANG Ming & HE XiaoRong department of Chemical Engineering,tsinghua University,beijing 100084,{3. 1. department of Chemical Engineering Tsinghua University Beijing 100084 China

This paper addresses the problem of optimal operation in long-term crude oil scheduling,which involves unloading crude oil from vessels,transferring it to charging tanks and feeding it to the distillation *** application of a new approach for modeling and optimization of long-term crude oil scheduling is presented and the event-tree based modeling method that is very different from mathematical programming is *** approach is developed on the basis of natural language modeling and continuous time *** triggered rules,decomposition strategy,depth-first search algorithm and pruning strategy are adopted to improve the efficiency of searching the optimum *** approach is successfully applied to an industrial-size problem over a horizon of 4 weeks,involving 7 vessels,6 storage tanks,6 charging tanks,2 crude oil distillation units,and 6 crude oil *** CPU (AMD 3.00+,2.0GHz) solving time is less than 70 seconds.

关键词： crude oil scheduling modeling and optimization event-tree based depth-first search algorithm

Interannual variability of Antarctic Oscillation and its influence on East Asian climate during boreal winter and spring

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Science china Earth Sciences 2006年第5期49卷 554-560页

作者： FAN Ke1,2,3.& WANG Huijun2 1. Nansen-Zhu International Research Center, Institute of Atmospheric physics, Chinese Academy of Sciences, beijing 100029, china 2. {3. of Atmospheric Science, Yunnan University, Kunming 650091, china 3. Graduate University of the Chinese Academy of Sciences, beijing 100049, china 1. Nansen-Zhu International Research Center Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China 2. department of Atmospheric Science Yunnan University Kunming 650091 China 3. Graduate University of the Chinese Academy of Sciences Beijing 100049 China

The interannual variability of Antarctic Oscillation (AAO) and its influence on East Asian climate during both boreal winter and spring are addressed. The results show that the positive AAO anomaly decreases the cold activity over East Asia during both boreal winter and spring. AAO-related barotropic meridional teleconnection from Antarctic to Arctic is found through analysis of mean me- ridional circulations. This meridional teleconnection is remarkable over Eurasia during boreal winter and over the Pacific Ocean during boreal spring. The results also show that zonal mean zonal wind at high latitudes in Southern Hemisphere has well positive correlation with that of Eurasia during boreal winter and has negative correlation with Pacific North American teleconnection (PNA) during boreal spring, which again display the meridional teleconnection. Thus, local meridional teleconnection is a possible linkage for interaction of circulations at mid-high latitudes between both hemispheres.

关键词： Antarctic Oscillation, Eurasian west wind, meridional teleconnection, mean meridional circulation.

Non-linear Identification Based on the Method of Gauss Functions

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Communications in Nonlinear Science and Numerical Simulation 1997年第3期2卷 39-44页

作者： Qing ZHANG & Chongde LU (department of Thermal Engineering, tsinghua University ,beijing, {3.) department of Thermal Engineering Tsinghua University Beijing 100084 China

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关键词： identification the method of gauss functions whole optimization

Study on Bonding of Steel-mushy Al-7graphite

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Journal of University of Science and Technology beijing 2001年第4期8卷 283-285页

作者： Peng Zhang, Yunhui Du, Daben Zeng department of Mechanical Engineering tsinghua University. beijing 100084, {3. Tsing Hua Univ Dept Mech Engn Beijing 100084 Peoples R China

The bonding of steel-mushy Al-7graphite was studied. The relationship between interfacial shear strength of bonding plate and solid fraction of Al-7graphite mushy was obtained, and the interfacial structure of bonding plate was determined. The results showed that: under the condition of 500 degreesC for preheat temperature of steel plate and 10 mm/s for rolling speed, the largest interfacial shear strength of bonding plate was 70.1 MPa when solid fraction of Al-7graphite mushy was 3..6%.

关键词： interfacial shear strength solid fraction interfacial structure

Study on near-wall turbulence structures with local Reynolds stress

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Communications in Nonlinear Science and Numerical Simulation 2000年第3期5卷 105-117页

作者： Li LI Chunxiao XU Guixiang CUI and Zhaoshun ZHANG(department of Engineering Mechanics, tsinghua University, beijing 100084, {3.) department of Engineering Mechanics Tsinghua University Beijing 100084 China

The direct- numerical- simulated ch annel turbulence is analyzed with two-dimensional wavelet transform. Considering the relation between turbulence coherent structure and Reynolds stress in near wall region, the local Reynolds stress (LRS) is defined.A new method for extracting coherent signals from turbulence based on the LRS is developed. Velocity fiuctuations are decomposed to coherent signals and background signals. It is found that the scaling exponents of coherent signals have a considerable deviation from the Kolmogorov scaling law q/3.(K41 theory), while that of background signals is very close to q/3. It is confirmed that coherent signals are mainly responsible for the anomalous *** characterized by the positive peaks of LRS, the typical structures in near wall region are obtained by conditional statistical averaging. It is shown that the local character of near-wall turbulence structures can be effectively described with LRS.

关键词： wavelet channel turbulence the local Reynolds stress

Research on Resonance Mechanism of Arc-ultrasonic

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Journal of Materials Science & Technology 2000年第5期16卷 525-528页

作者： Chunlei ZHANG+, Minsheng WU, Honpei HAO and Zandong HAN (department of Mechanical Engineering, tsinghua Universitys beijing 100084, {3.) department of Mechanical Engineering Tsinghua University Beijing 100084 China

As a transmission medium, welding arc can be modulated to emit ultrasonic energy by exerting high-frequency electric current. The frequency of exciting electric current has notable influence on the signals recorded by the sensors and the metallographic structures of the welds. The resonance phenomenon of arc-uitrasonic has been found in the experiment. Both the resonance mechanism and the distribution of resonance frequency are discussed by the bui|t vibration equation.

关键词： Research on Resonance Mechanism of Arc-ultrasonic Arc