检索结果-南通市图书馆

Effect of Ce on the cleanliness, microstructure and mechanical properties of high strength low alloy steel Q690E in industrial production process

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2019年第11期26卷 1372-1384页

作者： Hao Wang Yan-ping Bao Ming Zhao Min Wang Xiao-ming Yuan Shuai Gao State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China Technical Center of Inner Mongolia Baotou Steel Union Co. Ltd.Baotou 014010China The Rare Earth Steel Plates Plant of Baotou Iron and Steel Co. Ltd.Baotou 014010China

In order to improve the strength and toughness of Q690 E steel sheets,the effect of rare earth element Ce on the strength and toughness of Q690 E steel was studied by means of transmission electron microscopy,scanning electron microscopy,and metallographic *** results showed that the addition of Ce in steel limited the combination of S with Mn and Ca,transformed Al2O3 inclusion into spherical CeAlO3 inclusion,and modified the precipitate form of some composite inclusions of TiN and sulfide oxides into TiN precipitation *** inclusions were *** size of inclusions was decreased from 3–5μm to 1–2μm,and the distribution was *** played a role in purifying molten steel through desulphurization and ***,the addition of Ce in steel effectively increased the nucleation particles in the liquid phase,improved the nucleation rate,enlarged the equiaxed grain refinement area,and limited the development of columnar *** average grain size of slab decreased from 45.76 to 35.25μm,and the proportion of large grain size(>50μm)decreased from 40.41%to 23.74%.The macrostructural examination of slab was improved from B0.5 to C2.0,which realized the refinement of the solidified structure and reduced the banded structure of hot rolled *** addition,due to the inheritance of refined structure in the upstream,the recrystallization of deformed austenite and the growth of grain after recrystallization were restrained,and a refined tempered sorbite structure was *** rare earth element Ce was added,the width of the martensite lath bundle was narrowed from about 500 nm to about 200 nm,which realized a remarkable grain refinement strengthening and toughening *** properties such as tensile,yield,and low-temperature impact toughness were significantly improved.

关键词： rare earth HSLA steel inclusion structure grain refinement strengthening

Joint optimization of time and frequency synchronization based on polynomial sequences for OFDM systems

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2009年第3期16卷 19-23页

作者： ZHANG Yan-yan ZHANG Jian-hua HUANG Jiang-chun ZHANG ping Key Laboratory of Universal Wireless Communication Beijing University of Posts and Telecommunications Ministry of Education Beijing 100876 China Wireless Technology Innovation Institute Beijing University of Posts and Telecommunications Beijing 100876 China

In orthogonal frequency division multiplexing （OFDM） systems, time and frequency synchronization are two critical elements for guaranteeing the orthogonality of OFDM subcarriers. Conventionally, with the employment of pseudo-noise （PN） sequences in preamble design, the preamble information is not fully utilized in both symbol timing offset acquisition and carrier frequency offset estimation. In this article, a new synchronization algorithm is proposed for jointly optimizing the time and frequency synchronization. This algorithm uses polynomial sequences as synchronization preamble instead of PN sequences. Theoretical analysis and simulation results indicate that the proposed algorithm is much more accurate and reliable than other existing methods.

关键词： frequency synchronization joint optimization OFDM polynomial sequences timing synchronization

Classification of different walnut varieties using low-field nuclear magnetic resonance technology and cluster analysis

在线全文

学校读者我要写书评

暂无评论

International Journal of Agricultural and Biological Engineering 2019年第6期12卷 116-121页

作者： ping Song He Gao Baojun Zhao Aiguo Zhang Feng Liu College of Information and Electrical Engineering Shenyang Agricultural UniversityShenyang 110866China Service Center of Liaoning Forestry Development Shenyang 110036China Liaoning Institute of Economic Forestry Dalian 116031China

To classify different walnut varieties based on water and oil content of walnut,and determine their storage conditions,the low-field nuclear magnetic resonance(LFNMR)technology was used to obtain the NMR transverse relaxation time(T 2)of the samples based on the physical and chemical indicators of the walnut *** relationship between the relaxation time and phase state of the internal material of the sample was investigated,and the characteristic parameters of the NMR spectrum signals were statistically analyzed using cluster analysis to determine the different walnut varieties,and three different components,as well as their contents,were detected by a LFNMR spectrometer:firmly bound water,weakly bound water,and weakly bound *** results indicated that the oil peak was dominant in the overall signal intensity compared to the water peaks,in which the firmly bound water phase contributed more to the overall water signal between the water *** the analytic hierarchy process of cluster analysis,21 walnut samples were classified into three different classes,based on the characteristic parameters of the water-content and oil-content spectrum *** first class contains four walnut varieties characterized by least water and highest oil contents;the third class contains two walnut varieties,with the highest water content and least oil content;whereas,the second class contains 15 walnut varieties,with both water and oil contents at medium *** results showed that LFNMR led to a rapid detection of moisture and oil contents in walnuts,while cluster analysis classified different walnuts varieties based on these *** study also provided the basis for optimizing the storage methods and storage conditions of walnuts.

关键词： low-field nuclear magnetic resonance technology transverse relaxation time walnut cluster analysis decay curves

Positive Interactions： Crucial Organizers in a Plant Community

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Integrative Plant Biology 2006年第2期48卷 128-136页

作者： Dong-Liang Cheng Gen-Xuan Wang Bao-Ming Chen Xiao-ping Wei Key Laboratory of Arid and Grassland Agroecology at Lanzhou University Ministry of Education Lanzhou 730000 China College of Life Sciences Zhejiang University Hangzhou 310027 China

For more than a century, ecologists have concentrated on competition as a crucial process for community organization. However, more recent experimental investigations have uncovered the striking Influence of positive Interactions on the organization of plant communities. Complex combinations of competition and positive interactions operating simultaneously among plant species seem to be widespread In nature. In the present paper, we reviewed the mechanism and ecological importance of positive Interactions In plant communities, emphasizing the certainties and uncertainties that have made It an attractive area of research. Positive Interactions, or facilitation, occur when one species enhances the survival, growth, or richness of another. The Importance of facilitation in plant organization increases with ablotlc stress and the relative Importance of competition decreases. Only by combining plant interactions and the many fields of biology can we fully understand how and when the positive Interactions occur.

关键词： competition environmental gradient facilitation plant community plant-plant communications positive interactions.

Preparation and Electrochemical Properties of xLi2MnO3·（1-x）LiMn2O4 Composites

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2013年第2期29卷 307-310页

作者： YAO Su-mei ZHANG Jing-wen GUO Xun QIU Xin-ping Key Laboratory of Organic Optoelectronics and Molecular Engineering Department of Chemistry Tsinghua University Beo'ing 100084 P. R. China

Li2MnO3-doped spinel LiMn2O4 composites were synthesized by sol-gel method to improve the electro- chemical performance of LiMn2O4. The microstructures, morphologies and electrochemical performance of the obtained xLi2MnO3.（1-x）LiMnEO4 composites were characterized by X-ray diffraction（XRD）, scan electron microsco- py（SEM） and a galvanostatic charge-discharge process. It was found that both Li2MnO3 and LiMn2O4 components exist in xLi2MnO3·（1-x）LiMn204（O〈x〈1） composites. The 0.3Li2MnO3·0.7LiMnEO4 composite shows the optimized electrochemical performance, including discharge capacity and cycle stability. It was demonstrated that LiEMnO3-doped spinel LiMn204 cathode material can work at wide potential window with quite good capacity reten- tion and considerably larger reversible capacity compared to single-phase LiMn204 component.

关键词： Spinel Composite Electrochemical performance

Annealing effect on structural and magnetic properties of Tb and Cr co-implanted AIGaN

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Materials Science 2012年第4期6卷 366-370页

作者： Chun-Hai YIN Chao LIU Dong-Yan TAO Yi-ping ZENG Key Laboratory of Semiconductor Materials Science Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China

Unintentionally doped AIGaN layers, which were *** with 400 keV Tb＋ ions and 200keV Cr＋ ions at doses of 1.5×1015cm-2, have been rapid thermally annealed at 800℃ and 900℃ for 5 min in flowing N2, Compared with Tb implanted AIGaN sample, the Tb and Cr co-implanted sample revesls a larger magnetic signal. In this work, the annealing effect on the structural and magnetic properties of Tb and Cr co-implanted AIGaN thin films have been studied. XRD and raman scattering results indicate that no second phase presents in thetin films and mast of the implantation induced defects can be removed by post-implantation annealing. Superconducting quantum interference device （SQUID） measurements show clear room temperature ferromagnetic behavior and an increase in the saturation magnetization as a result of annealing. The saturation magnetization of the 900℃ annealed sample is about 15 times higher than that of the 800℃ annealed sample.

关键词： diluted magnetic semiconductor (DMS). room temperature ferromagne-tism ion implantation ltl-ride thin film

The influence of dihydropyridines calcium antagonists on 5-HT-induced intracellular calcium signal

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2007年第4期50卷 562-567页

作者： WANG ShuMin GUAN HuaShi FANG Yi MA ping SUN JianZi LIU LiHong Marine Drug and Food Institute Ocean University of ChinaQingdao 266003China Beijing Tongren Hospital Capital University of Medical SciencesBeijing 100730China Chinese PLA General Hospital Beijing 100853China Chinese PLA General Hospital of Rocket Forces Beijing 100088China

Confocal laser scanning microscopy (CLSM) was applied to detect the intracellular [Ca2+] variety of fluorescent intension, with Fluo-3/AM fluorescence loaded in SFSMC. The results show that 10 μmol/L Lacidipine can reduce the frequence which 10 μmol/L 5-HT induced [Ca2+] spark in SFSMC of calcium over loading to 50%, and amplitude to 50% or so. We can draw a conclusion that dihydropyridines cal-cium antagonists lacidipine can antagonize the release of intracellular [Ca2+] which 5-HT-induced in dose dependent manner.

关键词： lacidipine calcium sparks stomach fundus smooth muscle cells confocal laser scanning microscopy

Molecular cloning and functional identification of a cDNA encoding 4-hydroxy-3-methylbut-2-enyl diphosphate reductase from Tripterygium wilfordii

在线全文

学校读者我要写书评

暂无评论

Acta Pharmaceutica Sinica B 2017年第2期7卷 208-214页

作者： Qiqing Cheng Yuru Tong Zihao Wang ping Su Wei Gao Luqi Huang School of Traditional Chinese Medicine Capital Medical University National Resource Center for Chinese Materia Medica Academy of Chinese Medical Sciences State Key Laboratory of Quality Research in Chinese Medicines Macao University of Science and Technology

The 4-hydroxy-3-methylbut-2-enyl diphosphate reductase(HDR) is the last step key enzyme of the methylerythritol phosphate(MEP) pathway,synthesizing isopentenyl diphosphate and its allyl isomer dimethylallyl diphosphate,which is important for regulation of isoprenoid *** the full-length cDNA of HDR,designated TwHDR(GenBank Accession ***933412.1),was isolated from Tripterygium wilfordii for the first *** has an open reading frame(ORF) of 1386 bp encoding461 amino *** exhibits high homology with HDRs of other plants,with an N-terminal conserved domain and three conserved cysteine *** cDNA was cloned into an expression vector and transformed into an Escherichia coli hdr *** loss-of-function *** hdr mutant is lethal,the result showed that transformation of TwHDR cDNA rescued the *** hdr *** complementation assay suggests that the TwHDR cDNA encodes a functional HDR *** expression of TwHDR was induced by methyl-jasmonate(MJ) in *** suspension *** expression of TwHDR reached the highest level after 1 h of MJ *** results indicate that we have identified a functional TwHDR enzyme,which may play a pivotal role in the biosynthesis of diterpenoid triptolide in ***.

关键词： Tripterygium wilfordii Triptolide 4-Hydroxy-3-methylbut-2-enyl diphosphate reductase Complementation Gene expression

A New Statistical Downscaling Scheme for Predicting Winter Precipitation in China

在线全文

学校读者我要写书评

暂无评论

Atmospheric and Oceanic Science Letters 2013年第5期6卷 332-336页

作者： LIU Ying FAN Ke YAN Yu-ping Laboratory for Climate Studies National Climate Center China Meteorological Administration Institute of Atmospheric Physics Chinese Academy of Sciences Institute of Atmospheric Physics Chinese Academy of Sciences

An effective statistical downscaling scheme was developed on the basis of singular value decomposition to predict boreal winter(December-January-February)precipitation over *** variable geopotential height at 500 hPa(GH5)over East Asia,which was obtained from National Centers for Environmental Prediction’s Coupled Forecast System(NCEP CFS),was used as one predictor for the *** preceding sea ice concentration(SIC)signal obtained from observed data over high latitudes of the Northern Hemisphere was chosen as an additional *** downscaling scheme showed significantly improvement in predictability over the original CFS general circulation model(GCM)output in cross *** multi-year average spatial anomaly correlation coefficient increased from–0.03 to 0.31,and the downscaling temporal root-mean-square-error(RMSE)decreased significantly over that of the original CFS GCM for most China ***,large precipitation anomaly centers were reproduced with greater accuracy in the downscaling scheme than those in the original CFS GCM,and the anomaly correlation coefficient between the observation and downscaling results reached～0.6 in the winter of 2008.

关键词： statistical downscaling winter precipitation China Coupled Forecast System