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Local search yields a PTAS for fixed-dimensional k-means problem with penalties

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Journal of the Operations Research Society of china 2024年第2期12卷 351-362页

作者： Fan Yuan Da-Chuan Xu Dong-Lei Du Dong-mei zhang beijing Institute for Scientific and Engineering Computing Beijing University of TechnologyBeijing 100124China Faculty of Management University of New BrunswickFrederictonNB E3B 9Y2Canada school of Computer Science and Technology Shandong Jianzhu UniversityJinan 250101ShandongChina

We study a problem called the k-means problem with penalties(k-MPWP),which is a natural generalization of the typical k-means *** this problem,we have a set D of client points in R^(d),a set F of possible centers in R^(d),and a penalty cost Pj>O for each point j∈*** are also given an integer k which is the size of the center point *** want to find a center point set S■F with size k,choose a penalized subset of clients P■D,and assign every client in D\P to its open *** goal is to minimize the sum of the squared distances between every point in D\P to its assigned centre point and the sum of the penalty costs for all clients in *** using the multi-swap local search technique and under the fixed-dimensional Euclidean space setting,we present a polynomial-time approximation scheme(PTAS)for the k-MPWP.

关键词： Approximation algorithm k-means Local search Penalty

Robust multiuser MIMO scheduling algorithms with imperfect CSI

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Science china(Information sciences) 2012年第4期55卷 815-826页

作者： MAO JunLing 1,3.GAO JinChun 1,3.LIU YuanAn 1,3.XIE Gang 2,3.& zhang Jian 1,3.1 school of Electronic Engineering,beijing {3. of Posts and Telecommunications,beijing 100876,china 2 school of Information and Communication Engineering,beijing {3. of Posts and Telecommunications,beijing 100876,china 3.Key Lab of Universal Wireless Communications,Ministry of Education,beijing {3. of Posts and Telecommunications,beijing 100876,china 1. school of Electronic Engineering Beijing University of Posts and Telecommunications Beijing 100876 China3. Key Lab of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China2. School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

Robust multiuser multiple-input-multiple-output (MIMO) scheduling algorithms are proposed in this *** imperfect channel state information (CSI),traditional scheduling algorithms for the multiuser MIMO system based on the zero forcing precoding scheme will lose some performance due to the multi-user interference (MUI).In order to improve the system average throughput,we study the robust multiuser MIMO scheduling problem with imperfect *** the average capacity formula,we derive a robust factor which can transform the robust multiuser MIMO scheduling problem into the traditional one,thus most existing non-robust scheduling algorithms can be robust if this factor is *** results show that compared with the traditional algorithms,the proposed robust algorithms can improve the system average throughput significantly under the CSI error environment.

关键词： multiuser MIMO (MU-MIMO) scheduling robust imperfect CSI

SEM in-situ Fatigue Observation on Crack Initiation and Growth from Inclusion in P/M Rene95 Superalloy

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Journal of university of Science and Technology beijing 2001年第3期8卷 195-197页

作者： Lina zhang, Jianxin Dong, Xishan Xie Material Science and Engineering school, university of Science and Technology {3., {3. 100083. china Univ Sci & Technol beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China

A special designed experiment was conducted for observing crack initiation and growth in P/M Rene95 superalloy under tension-tension loading by self-made SEM in-situ fatigue loading stag. Several alumina inclusion particles exposed at the specimen surface were observed carefully. During fatigue test inclusions led to cracks initiation. The cracks can be formed by two mechanisms. Generally, the cracks nucleated at the interface between inclusion and matrix. Sometimes, cracks were also formed inside the inclusion. As the increase of cycles, some cracks at the interface between inclusion and matrix broadened and propagated along the direction about 45 degrees to the loading axis. On the other hand, the cracks inside the inclusion propagated in the inclusion and towards matrix.

关键词： inclusion P/M superalloy LCF SEM in-situ fatigue

Fuzzy Pattern Recognition in Atlas and Images of the Unevenness of Carbide in Tool Steel

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Journal of university of Science and Technology beijing 2001年第3期8卷 234-236页

作者： Hui zhang, Angui Li, Zhigang zhang, Li Jiang Applied Science school, {3. of Science and Technology beijing, beijing 100083. china Univ Sci & Technol beijing App Sci Sch Beijing 100083 Peoples R China

Fuzzy pattern recognition has been employed to identify some atlas and images of the unevenness of carbide in tool steel. Three models have been constructed. These models were based on fuzzy mathematics theory, as well as fuzzy pattern recognition method. Distribution rule of the unevenness of eutectic carbide in ledeburite steel is proposed in these models respectively.

关键词： fuzzy mathematics fuzzy and pattern recognition characteristic specimen

Fabrication of pure copper rods containing continuous columnar crystals by continuous unidirectional solidification technology

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Journal of university of Science and Technology beijing 2004年第3期11卷 240-244页

作者： Hong zhang Jianxin Xie Zidong Wang Materials Science and Engineering school, university of Science and Technology {3., {3. 100083. china Mat. Sci. and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

Pure copper rods containing continuous columnar crystals were fabricatedusing the downward CUS (Continuous Unidirectional Solidification) equipment. When the technologicalparameters were set as the ranges of mould temperature 1100-13.0℃, cooling distance (the distancefrom the exit of the cast mould to the start point of cooling) 10-20 mm, casting speed 0.2-2.5 mm/s,cooling water (20-25℃) volume 1000-13.0 L/h, and when these parameters matched reasonably, the CUSprocess was performed stably, and pure copper rods containing continuous columnar crystals withbright and smooth surface were produced. The dendritic arm spacing of the crystals in copper rodsdecreased with increasing the casting speed. The results of the texture by X-ray diffractionanalysis showed that the rods has strong fiber texture.

关键词： copper continuous unidirectional solidification mould temperature castingspeed microstructure texture

The onset and advance of the Asian summer monsoon

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Science Bulletin 2006年第1期51卷 80-88页

作者： Lü Junmei1,2,4, zhang Qingyun1, TAO Shiyan1 & JU Jianhua3.1. State Key Laboratory of Numerical Modeling for Atmospheric Sci- ences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of sciences, {3. 100029, china 2. Department of Atmospheric sciences, Yunnan university, Kunming 650091, china 3. china Meteorological Administration Training Centre, {3. 100081, china 4. Graduate school of Chinese Academy of sciences, {3. 10003., china State Key Laboratory of Numerical Modeling for Atmospheric sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Department of Atmospheric sciences Yunnan University Kunming 650091 China Graduate school of Chinese Academy of sciences Beijing 100039 China china Meteorological Administration Training Centre Beijing 100081 China

Based on the daily outgoing longwave radiation (OLR) data from National Oceanic and At- mospheric Administration (NOAA) satellites, the Cli- mate Prediction Center’s merged analysis of pre- cipitation (CMAP) data and the National Centers for Environmental Prediction/National Center for At- mospheric Research (NCEP/NCAR) reanalysis dataset, the mean intraseasonal variability of the Asian summer monsoon (ASM) is investigated by using power spectrum analysis, band-pass filter, and diagnostic analyses. The processes of the onset and advance of monsoon over the southern part of Indo- china Peninsula, the east coast of Bay of Bengal, the South china Sea and the Indian subcontinent are explored. It is found that there is an abrupt change in OLR, precipitation and zonal wind during the onset and advance of the ASM. It is also indicated that the southern part of Indochina Peninsula and the adja- cent Andaman Sea is the region where the earliest onset of the ASM occurs in the 2nd pentad of May.

关键词： Asian summer monsoon intraseasonal variability onset advance.

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面向图像拼接检测的自适应残差算法

中国图象图形学报 2024年第2期29卷 419-429页

作者：张玲穆文鹏陈北京南京信息工程大学数字取证教育部工程研究中心南京210044 南京信息工程大学江苏省大气环境与装备技术协同创新中心南京210044 南京信息工程大学计算机学院南京210044

目的恶意的图像拼接篡改给名誉、法律、政治等带来一系列的挑战,而现有的图像拼接检测算法通常采用参数固定的高通滤波器提取滤波特征进行预处理,没有考虑图像之间的差异。方法本文设计自适应残差模块(adaptive residuals module, ARM... 详细信息

目的恶意的图像拼接篡改给名誉、法律、政治等带来一系列的挑战,而现有的图像拼接检测算法通常采用参数固定的高通滤波器提取滤波特征进行预处理,没有考虑图像之间的差异。方法本文设计自适应残差模块(adaptive residuals module, ARM)凸显拼接篡改痕迹,将卷积运算后的残差多次拼接,且每次拼接后再利用注意力机制实现通道间的非线性交互。然后,使用通道注意力SE(squeeze and excitation)模块以减少由ARM提取残差特征产生的通道之间信息冗余,并以在图像分类领域获得卓越性能的EfficientNet(high-efficiency network)为骨干网络,提出一种新的图像拼接检测算法。结果实验结果表明,所提算法在CASIA I(CASIA image tampering detection evaluation database),CASIA II,COLUMBIA COLOR,NIST16(NIST special database 16)和FaceForensic++这5个公开数据集上分别取得98.95%,98.88%,100%,100%,88.20%的检测准确率,获得比现有算法更高的准确率。提出的ARM将骨干网络EfficientNet在CASIA II数据集的准确率提高了3.94%以上。结论提出的基于自适应残差的图像拼接检测算法充分考虑图像之间的差异,凸显篡改区域与未篡改区域之间的区别,并获得更好的拼接检测结果。

关键词：图像取证深度神经网络图像拼接检测自适应残差 EfficientNet

The crustal structure under Sanjiang and its dynamic implications:Revealed by seismic reflection/refraction profile between Zhefang and Binchuan,Yunnan

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Science china Earth sciences 2005年第9期48卷 1329-1336页

作者： zhang Zhongjie1, BAI Zhiming1, WANG Chunyong2, TENG Jiwen1, Lü Qingtian3. LI Jiliang1, LIU Yifeng1 & LIU Zhenkuan4 1. Institute of Geology and Geophysics, Chinese Academy of sciences, beijing 100029,{3. 2. Institute of Geophysics,{3. Seismological Bureau, beijing 100085,{3. 3. Institute of Deposition Resource, Chinese Academy of Geosciences, beijing 10003.,{3. 4. school of Exploration and Information,{3. university of Geosciences, beijing 100083.{3. 1. Institute of Geology and Geophysics Chinese Academy of Sciences 100029 Beijing China 2. Institute of Geophysics China Seismological Bureau 100085 Beijing China 3. Institute of Deposition Resource Chinese Academy of Geosciences 100037 Beijing China 4. school of Exploration and Information China University of Geosciences 100083 Beijing China

The fault belts in Sanjiang mainly include Jinshajiang-Honghe fault, Lancangjiang fault and Nujiang fault (called Sanjiang faults) in western Yunnan Province, china. By interpreting the wide-angle seismic reflection/refraction profile between Zhefang and Binchuan, which crosses Tengchong and Baoshan blocks in Dianxi (western Yunnan) tectonic zone, we recon- struct the crustal structure with seismic traveltime tomography for crustal P-wave velocity and the seismic scattering image for crustal seismic reflection structure. In this paper, we firstly present the crustal structure images of P-wave velocity and seismic reflection under the wide-angle seismic profile. These results demonstrate that, the crustal velocity structure and seismic reflec- tion structure along the profile can be divided into 3.segments, and there is an obvious difference of crustal structure among the eastern, the western and the middle segment. Generally, crustal P-wave velocities in the Baoshan segment are 0.1―0.2 km/s slower and seismic reflection am- plitudes from Moho discontinuity are stronger than the other 2 segments. In the studied area, crustal thickness is about 40 km, and shows the thickening tendency from west to east along the profile. Additionally, it can be seen that there is one strong-amplitude seismic reflection event as bright points at the depths of 8―10 km, along the segment of 80―115 km of the profile (south- ward of Tengchong); and seismic reflection wave-field from Moho discontinuity varies obviously along the lateral direction. Finally, we make some discussions on the crustal thickening pattern in the Sanjiang fault belt, structural environment of earthquake development and the contact rela- tionship between the Tengchong block, Banshan block and Luxi trough.

关键词： Sanjiang area wide-angle seismic profile crustal structure.

The deteriorated degradation resistance of Mg alloy microtubes for vascular stent under the coupling effect of radial compressive stress and dynamic medium

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Journal of Magnesium and Alloys 2024年第2期12卷 573-585页

作者： Mengyao Liu Yabo zhang Qingyuan zhang Yan Wang Di mei Yufeng Sun Liguo Wang Shijie Zhu Shaokang Guan school of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China Henan Key Laboratory of Advanced Magnesium Alloys Zhengzhou 450002China Key Laboratory of Advanced Materials Processing&Mold Ministry of Education Zhengzhou 450002China

The degradation of Mg alloys relates to the service performance of Mg alloy biodegradable *** order to investigate the degradation behavior of Mg alloys as vascular stent materials in the near service environment,the hot-extruded fine-grained Mg-Zn-Y-Nd alloy microtubes,which are employed to manufacture vascular stents,were tested under radial compressive stress in the dynamic Hanks'Balanced Salt Solution(HBSS).The results revealed that the high flow rate accelerates the degradation of Mg alloy microtubes and its degradation is sensitive to radial compressive *** results contribute to understanding the service performance of Mg alloys as vascular stent materials.

关键词： Mg alloy Microtubes Degradation behavior Radial compressive stress Dynamic conditions