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Surface roughness and removal rate in magnetorheological finishing of a subsurface damage free surface

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Progress in Natural science:Materials International 2005年第6期15卷 538-544页

作者： CHENG Haobo1*, WANG Yingwei2. FENG Zhijing1 and CHENG Kai3.1. State Key Laboratory of Tribiology, Tsinghua university, Beijing 100084, china 2. {2. of Material sciences, Changchun university of science and Technology, Changchun 13.02., china 3. Faculty of information and Engineering Systems, City Campus, Leeds LS1 3.E, UK) State Key Laboratory of Tribiology Tsinghua University Beijing 100084 China department of Material sciences Changchun University of Science and Technology Changchun 130021 China Faculty of information and Engineering Systems City Campus Leeds LS1 3HE UK

Based on computer-controlled optical surfacing, a new technique called magnetorheological finishing (MRF), is presented. The new technique combines the features of conventional loose abrasive machining with a wheel shaped polishing tool. The tool incorporates a host of features and has unprecedented fabricating versatility. The pre-polishing and fine polishing processes can be performed only by adjusting different parameters. The material removal function is studied theoretically and the results of simulation present a Gaussian distribution feature. Based on the established theoretical model, material removal rate experiments involving a parabolic mirror are designed and carried out to determine the effect of controllable parameters on size of the gap between the workpiece and the polishing wheel, rotating speed of the polishing wheel, concentration of volume fraction of non-magnetic particles and polishing time. Further experiments are carried out on the surface microstructure of the workpiece, the final surface roughness with an initial value of 10.98 nm reaches 1.2. nm root mean square (RMS) after 2. min of polishing. The subsurface damage experiment and the atomic force microscopy (AFM) measurement on the polished surface can also verify the feasibility of the MRF technique.

关键词： magnetorheological finishing surface roughness computer controlled optical surfacing subsurface damage removal function.

Asymptotic SEP of MIMO beamforming in two-hop AF relaying systems

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science china({2. sciences) 2012年第2期55卷 377-383页

作者： FU YouHua1,HAN YuJie2.YANG LvXi2.ZHU WeiPing3.& LIU Chen1 1School of Electronic science and Engineering,{3. {2. of Posts and Telecommunications,{3. 2.0003.china 2.chool of information science and Engineering,Southeast {2.,{3. 2.0096,china 3.15} of Electrical and Computer Engineering,Concordia {2.,Montreal H3. 1M8,Canada 1. School of Electronic science and Engineering Nanjing University of Posts and Telecommunications Nanjing 210003 China2. School of Information Science and Engineering Southeast University Nanjing 210096 China3. Department of Electrical and Computer Engineering Concordia University Montreal H3G 1M8 Canada

This paper derives an asymptotic average symbol error probability(SEP)expression for multiple-input multiple-output(MIMO)two-hop amplify-and-forward(AF)relay systems with optimal *** analysis at high signal-to-noise ratio(SNR)quantifies the diversity order and array gain,which are valid for any antenna numbers of the terminals and arbitrary channel fading *** is also proved that the system performance is dominated by the relatively degraded one of the two-hop *** results based on the simple expressions provide valuable insights into the performance and practical design considerations of MIMO AF networks.

关键词： MIMO relay networks optimal beamforming symbol error probability(SEP) diversity order

Color image enhancement based on HVS and PCNN

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science china({2. sciences) 2010年第10期53卷 1963-1976页

作者： ZHANG YuDong, WU LeNan , WANG ShuiHua & WEI Geng School of information science & Engineering, Southeast {2., {3. 2.0096, china 1. School of information science & Engineering Southeast University Nanjing 210096 China

To enhance color images more effectively, a novel strategy is presented in this paper. We firstly translate the image to be enhanced from RGB space into HIS space, secondly keep its H component unchanged, and thirdly stretch its S component exponentially, and at last process its I component in the following manner: couple both the gray value and the spatial {2. into an inner activity item of corresponding neuron, integrate the human visual system into a dynamic component of corresponding neuron, and compare the inner activity item with dynamic component to obtain the enhanced image. Experiments demonstrate the effectiveness and validity of our strategy.

关键词： image enhancement human visual system (HVS) pulse coupled neural network (PCNN) color image

Discovery and analysis of ultra-micro grinding grain texture in slipping lamellae of ductile-brittle zone

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science china Earth sciences 2004年第3期47卷 265-271页

作者： GE Heping1, SUN Yan1, LU Xiancai1, ZHU Wenbin1, GUO Jichun1, LIU Deliang2.& Chi-yuen Wang3.1. department of Earth sciences, {2. university, State Key Laboratory of Mineral Deposit, {2. 2.0093. china 2. department of Earth and space sciences, university of science and Technology of china, Hefei 2.002., china 3. department of Geology and Geophysics, university of California, Berkeley, CA 9472., USA nanjing Univ Dept Earth Sci State Key Lab Mineral Deposit Nanjing 210093 Peoples R China Univ Sci & Technol china Dept Earth & Space Sci Hefei 230026 Peoples R China Univ Calif Berkeley Dept Geol & Geophys Berkeley CA 94720 USA

Based on the observation of the deep bore cores sampled from the State of Cali-fornia, USA, preferred arranged particulate concentration belts were found in the ultra-slipping lamellae. And the same phenomenon was found again later in the bore cores from the petroleum basin in the Northern Shaanxi Province. It may be the product of the dynamic processes involv-ing tumbling, grinding and compresso-shearing functions, so the spherical particulates with ul-tra-size of nm and mm are called grinding grain. The formation of the grinding grains is related with the ductile-brittle deformation, the lateral pressure of the slipping, and the very low grade of dynamic metamorphism of the rocks. Based on the systematic analysis, it is indicated that some elements like Nb and Ta are enriched in the grinding grains in the granitic rocks because of the chemical differentiation, and that the slipping lamellae bearing grinding grains in mudstone with smear efficiency prove a perfect seal for oil and gas reservoirs. Meanwhile, the paper provides bases for the studies on the fast stick-slip movement and shear paradigm.

关键词： slipping lamellae, grinding grain texture, ductile-brittle deformation, smear efficiency.

Optimal MAC based cooperative spectrum sensing in cognitive radio networks

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science china({2. sciences) 2012年第6期55卷 1388-1396页

作者： CHEN Zhong 1,ZHANG XianDa 1 & YANG LanJuan 2.1 State Key Laboratory of Intelligent Technology and Systems,Tsinghua National Laboratory for information science and Technology,{2. of Automation,Tsinghua university,Beijing 100084,china 2.Institute of Command Automation,PLA university of science and Technology,nanjing 2.0007,china 1. State Key Laboratory of Intelligent Technology and Systems Tsinghua National Laboratory for Information Science and Technology Department of Automation Tsinghua University Beijing 100084 China2. Institute of Command Automation PLA University of Science and Technology Nanjing 210007 China

This paper considers a cognitive radio (CR) system in non-ideal fading wireless channels and pro-poses cooperative spectrum sensing schemes based on coherent multiple access channels (MAC),serving as an alternative way to improve the cooperative spectrum sensing performance and provide space diversity for spec-trum *** statistics are transmitted using a common channel from the secondary users (SUs) to a fusion center (FC) where the global decision is *** optimal scaling factors of the proposed schemes are obtained by maximizing the detection probability under a target false alarm probability and a transmit power *** the proposed optimal MAC scheme has high computational complexity,a sub-optimal solu-tion based on maximization of the deflection coefficient (DC) is also *** results show that the proposed algorithms can significantly improve the spectrum sensing performance and approach the detection baseline.

关键词： cognitive radio (CR) spectrum sensing multiple access channel (MAC) deflection coefficient optimization

A new measure to characterize multifractality of sleep electroencephalogram

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science Bulletin 2006年第24期51卷 3059-3064页

作者： MA Qianli1,2.NING Xinbao1,WANG Jun2.& BIAN Chunhua1 1. State Key Laboratory of Modern Acoustics,department of Electronics {3. and Engineering,Institute for Biomedical Electronic Engi-neering,{2. university,{2. 2.0093.china 2. Province Key Laboratory of Image Processing & Image Communica-tion,College of Telecommunications and information Engineering,{2. university of Posts & Telecommunications,{2. 2.0003.china State Key Laboratory of Modern Acoustics Department of Electronics Science and Engineering Institute for Biomedical Electronic Engineering Nanjing University Nanjing 210093 China Province Key Laboratory of Image Processing & Image Communication College of Telecommunications and Information Engineering Nanjing University of Posts & Telecommunications Nanjing 210003 China

Traditional methods for nonlinear dy-namic analysis,such as correlation dimension,Lyapunov exponent,approximate entropy,detrended fluctuation analysis,using a single parameter,cannot fully describe the extremely sophisticated behavior of electroencephalogram (EEG). The multifractal for-malism reveals more “hidden” information of EEG by using singularity spectrum to characterize its nonlin-ear dynamics. In this paper,the zero-crossing time intervals of sleep EEG were studied using multifractal analysis. A new multifractal measure Δasα was pro-posed to describe the asymmetry of singularity spec-trum,and compared with the singularity strength range Δα that was normally used as a degree indi-cator of multifractality. One-way analysis of variance and multiple comparison tests showed that the new measure we proposed gave better discrimination of sleep stages,especially in the discrimination be-tween sleep and awake,and between sleep stages 3.and 4.

关键词： sleep electroencephalogram multifractality.

Effects of abnormally high heat stress on petroleum in reservoir——An example from the Tazhong 18 Well in the Tarim Basin

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science china Earth sciences 2008年第4期51卷 515-527页

作者： ZHU DongYa1, JIN ZhiJun1, HU WenXuan2.& ZHANG XueFeng3.1 Petroleum Exploration and Production Institute, china Petroleum & Chemical Corporation, Beijing 100083. china 2.{2. of Earth sciences, nanjing university, nanjing 2.0093. china 3.School of Resource and information, china university of Petroleum, Beijing 102.49, china Petroleum Exploration and Production Institute China Petroleum & Chemical Corporation Beijing China department of Earth sciences Nanjing University Nanjing China School of Resource and information China University of Petroleum Beijing China

An igneous intrusion of 94m thick was discovered intruding into the Silurian sandstone from Tazhong 18 Well. The petroleum previously preserved in the Silurian sandstone reservoir was altered into black carbonaceous bitumen by abnormally high heat stress induced by the igneous intrusion. The reflec-tance of the carbonaceous bitumen reaches as high as 3.54%, indicating that the bitumen had evolved into a high thermal evolution level. Similar to the Silurian samples from the neighboring Tazhong 11, Tazhong 12. Tazhong 45 and Tazhong 47 wells, the distribution of C2., C2. and C2. steranes of the car-bonaceous bitumen is still "V" -shaped and can still be employed as an efficient parameter in oil source correlation. The "V" -shaped distribution indicates that the hydrocarbons from the Tazhong 18 and the neighboring wells were all generated from the Middle-Upper Ordovician hydrocarbon source rocks. However, the oil source correlation parameters associated with and terpanes had been changed greatly by the high heat stress and can no longer be used in oil source correlation. The δ 13. values of the pe-troleum from the neighboring wells are between -3.0}53. and -3..3.‰, coincident with those of the Paleozoic marine petroleum in the Tarim Basin. However, the δ 13. values of the carbonaceous bitumen from the Tazhong 18 Well are between -2..18‰ and -2..2.‰, isotopically much heavier than the pe-troleum from the neighboring wells. The content of light hydrocarbons (nC14-nC2.) of the saturated hydrocarbon fraction in the carbonaceous bitumen is extremely higher than the content of heavy hy-drocarbons. The light/heavy hydrocarbon ratios (ΣnC2.-/ΣnC2.+) are between 4.56 and 3..17. In the saturated fraction, the even numbered hydrocarbons are predominant to the odd numbered, and the OEP (Odd to Even Predominance) values are between 0.2. and 0.49. However, the content of light hy-drocarbons in the petroleum from the neighboring wells is relatively low and the content of the even numb

关键词： Tarim Basin igneous intrusive abnormally high heat stress bitumen carbon isotope PAH

Extraction of the spectral information of terahertz signals using superconducting Josephson junction

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science china(Technological sciences) 2010年第5期53卷 1247-1251页

作者： XU WeiWei,CHEN Jian,KANG Lin & WU PeiHeng department of Electronic science & Engineering,{2. {3.,{2. 2.0093.china 1. department of Electronic science & Engineering Nanjing University Nanjing 210093 China

Using YBa2.u3.7-δ/MgO bicrystal Josephson junction,we have developed a setup for spectrum analyses of terahertz signals,up to 2.5 THz,with a frequency resolution of 3.*** junction works at liquid nitrogen temperature when the signal frequencies are low while for signals at 1.6 THz and 2.5 THz the junction is cooled to 6 *** signal processing(DSP) chips are made use of to build a data acquisition and processing system so that it can be compact,fast,and *** the completion of the relevant hardwares and softwares,the measurements are now automated.

关键词： Josephson junction THz wave spectrum detection DSP technology

Interhemispheric atmospheric mass oscillation and its relation to interannual variations of the Asian monsoon in boreal summer

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science china Earth sciences 2010年第9期53卷 1343-1350页

作者： LU ChuHan, GUAN ZhaoYong & CAI JiaXi Key Laboratory of Meteorological Disaster of Ministry of Education and College of Atmospheric sciences, nanjing {2. of {3. science & Technology, nanjing 2.0044, china 1. Key Laboratory of Meteorological Disaster of Ministry of Education and College of Atmospheric sciences Nanjing University of Information Science & Technology Nanjing 210044 China

Using NCEP/NCAR reanalysis and precipitation records of Chinese stations, we have investigated the relationship of interhemispheric oscillation of air mass (IHO) with global lower-level circulation and monsoon anomalies in boreal summer. Our results show that the summer IHO explains a greater portion of variance in the abnormal distribution of atmospheric mass over 3.°S-60°N as well as the Antarctic. The IHO strongly correlates to the variations of sea level pressure (SLP) in these regions. It is shown that IHO has some influences on both atmospheric mass transports and water vapor fluxes over 3.°S-60°N in association with three anomalous cyclonic circulations over land areas of the eastern hemisphere, which is in close relation to the changes in summer monsoon intensity in eastern Asia and western Africa. Composites of summer rainfall anomalies in china for high and low IHO-index years indicate that the eastern Asian summer monsoon is more intense, with positive precipitation anomaly centers in northern and northeastern parts of china, as opposed to the negative center over the mid-lower reaches of the Yangtze River (MLRYR) in stronger IHO years. In weak IHO years, a feeble summer monsoon appears in eastern Asia, leading to positive center of precipitation anomalies displaced into the MLRYR. Furthermore, a teleconnection in wind fields between the western African and eastern Asian monsoon regions was observed in the middle and higher troposphere in the scenario of IHO. The anomalous cyclonic (anticyclonic) circulations along the path of this Africa-East Asia teleconnection were found to be just over the diabatic heating (cooling) centers, suggesting that diabatic forcings are responsible for the formation of this Africa-East Asia teleconnection.

关键词： interhemispheric oscillation Asian monsoon precipitation china boreal summer