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Regional　and　Synoptic-scale　Features　Associated　with　Inactive　Periods　of　the　Summer　Monsoon　over　South　China

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Advances in Atmospheric Sciences 1997年第2期14卷 100-107页

作者： This research is supported by the Research Grants Council of the university Grants Committee of Hong Kong Grant 9040074. C. H. So and Johnny C. l. Chan Department of Physics and Materials Science, City university of Hong Kong Department of Physics and Materials Science City University of Hong Kong

This paper presents an observational study of the physical processes responsible for the inactive period (break) of the summer monsoon over South China (SC). The break of the monsoon is defined by using the rainfall data over Hong Kong Meteorological parameters provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) for the period 1985-1990 are examined. Daily values of each parameter for the six years are then composited each day for the period of 5 days before to 1 day after the break. It is found that several days before the break, changes opposite to those occurred during the onset and active periods begin to take place. This suggests that a feedback mechanism is present which tends to restore the atmosphere to a more stable state. This mechanism may be initiated by the formation of convective clouds during the onset and active periods. These clouds then reduce the solar radiation to the ground, leading to a gradual drop in the temperature. This drop, together with the cooling of the atmosphere due to the large amounts of rainfall, causes the pressure over the SC region to become higher, which in turn induces a westward extension of the subtropical ridge. The decrease in temperature over SC may also shift the location of the heat source to the west, which leads to a concomitant westward shift of the convergence of the southerlies and results in less moisture-laden air reaching the SC region. The atmosphere then becomes unfavourable for heavy convection and therefore a break starts.

关键词： Inactive period Summer monsoon South China subtropical high

黄土高原水土流失区生态退耕对粮食安全的影响

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山地学报 2006年第1期24卷 7-12页

作者：刘贤赵宿庆烟台师范大学地理与资源管理学院烟台师范大学图书馆山东烟台264025 中国科学院水土保持研究所陕西杨陵712100

退耕还林是黄土高原水土流失区改善生态环境的一种有效途径,但在一定程度上必然会影响到区域的粮食安全,其中最直接最主要的影响便是退耕带来耕地面积减少,引发粮食总产量的降低。根据黄土高原水土流失区的生态退耕规划,对退耕还林还草... 详细信息

退耕还林是黄土高原水土流失区改善生态环境的一种有效途径,但在一定程度上必然会影响到区域的粮食安全,其中最直接最主要的影响便是退耕带来耕地面积减少,引发粮食总产量的降低。根据黄土高原水土流失区的生态退耕规划,对退耕还林还草可能对当地造成的粮食生产影响进行分析。利用具有显著科学性和可操作性的最小人均耕地面积和耕地压力指数模型,对该区各亚区进行了粮食安全评价,并以此为基础提出了黄土高原水土流失区各亚区退耕还林还草与粮食安全的协调途径。

关键词：黄土高原水土流失区生态退耕粮食安全调控途径

Melt Infiltration Ability and Microstructural Evolution of Fe40Al/TiC Composites System

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Melt Infiltration Ability and Microstructural Evolution of F...

EXCURSIONS AND lVY SYSTEM OF BOUNDARY PROCESS

第十届国际制造工程与管理会议

作者： Mingxia Gao, F J Oliveira, Yi Pan, J l Baptista, J M Vieira (1. Department of Materials Science and Engineering, Zhejiang university, Hangzhou 310027, China-, 2. Department of Ceramics and Glass Engineering/CICECO, university of Aveiro, Portugal)

Pressureless melt infiltration is an economic route for preparation of high-density ceramic/melt composites. In this study, the Fe40Al iron aluminide intermetallic, a low cost material of excellent oxidation and corrosion resistance, was used as binder for fabricating Fe40Al/TiC composites by pressureless melt infiltration. The wetting ability of liquid Fe40Al in porous TiC preform was studied by in-situ monitoring the melting and infiltration process. The infiltration ability was investigated by observing the distance of liquid Fe40Al intrusion in porous TiC pre-forms at different infiltration temperatures and times by using optical microscope. Porous TiC per-forms with density of 60% - 88%TD (theoretical density), prepared under pre-defined sintering temperature cycles, were used for fabricating Fe40Al/TiC composites in the range of 12% - 40% metal content by volume. Almost full dense Fe40Al/TiC composites were successfully fabricated by this technique. liquid Fe40Al exhibited excellent infiltration ability, the distance of complete intrusion of liquid Fe40Al in the TiC sintered pre-form with density of 88%TD was over 7 mm after 5 min at the infiltration temperature of 1 450 ℃.Microstructural observation by SEM and TEM also showed that liquid Fe40Al filled the very narrow gaps among TiC particles, the interfaces of TiC particles and Fe40Al plastic ligaments being metallurgical bonded. TEM revealed that high density of dislocations formed in Fe40Al ligaments during solidification, which favor the mechanical properties. Ti decomposed from TiC particles and dissolved into Fe40Al during infiltration. According to the compositional analysis of TEM-EDS, the concentration of Ti in Fe40Al ranges at 1at% - 4at% depending on composite fabricating conditions and the distance from the measuring point to the closest TiC particles. XRD analysis indicated that the composites were composed of two phases, the original TiC and Fe0.4Al0.6 intermetallic. No new phase formed during in

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Chinese Annals of Mathematics,Series B 2003年第4期24卷 491-500页

作者： HE PING YING JIANGANG Institute of Mathematics, Fudan Univeraity, Shanghai 200433, China. Institute of Mathematics, Fudan university, Shanghai 200433, China.

In this paper, the authors investigate the joint distribution of end points of excursion awayfrom a closed set straddling on a fixed time and use this result to compute the levy systemand the Dirichlet form of the bou... 详细信息

关键词： Markov process Excursions levy system Dirichlet form Boundary process

Effects of glutamic acid on spontaneous discharges of arcuate nucleus in hypothalamic slice from normal and inflamed rats

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Effects of glutamic acid on spontaneous discharges of arcuat...

Flow-injection Chemiluminescence Sensor for Hydrogen Peroxide with Immobilized Reagents

中国神经科学学会第四次会员代表大会暨第七届全国学术会议

作者： Jian-Ming PENG,Qi ZHU,Xing-Hong JIANG Department of Neurobiology,laboratory of Aging and Nervous Diseases,School of Medicine,Soochow university, Suzhou 215123,China

＜正＞To study the influence of glutamic acid（Glu） on the electric activities of arcuate nucleus（ARC） neurons in the normal rats and inflamed rats which were induced by complete Freund’s adjuvant（CFA）.The experiment was performed on isolated mediobasal hypothalamus slice to observe the effect of Glu on unit discharges of ARC *** NMDA receptor agonist NMDA,NMDA receptor antagonist MK-801 and non-NMDA receptor antagonist CNQX were used to analyze the receptor mechanism of *** unit discharges were recorded *** immunohistochemistry was imployed to observe the expression of NMDAR 1 in the ARC neurons of normal rats and the CFA *** experimental results indicated that:（1） Three types of spontaneous discharge（regular firing,irregular firing,firing in bursts） were observed in ARC neurons.（2） Glu（200μmol/l） can enhance the electric activities of ARC *** effects can be mimicried by NMDA（25 umol/l） and blocked by MK-801（100 umol/l）.（3） The spontaneous discharge frequency of ARC neurons in CFA rats was higher than those in normal rats.（4） The excitatory effects of Glu and NMDA in the ARC neurons of CFA rats were more *** spontaneous discharge frequency of ARC neurons incresed significantly,the latency of drug action was shortened and the duration was *** excitatory response of ARC neurons to Glu and NMDA couldn’t be blocked by CNQX but could be partly blocked by MK-801.（5） The results of immunohistochemistry indicated an up-regulation of the expression of NMDAR 1 in the ARC neurons of the CFA *** results suggested that glutamate mechanism（mediated by NMDA receptor） is involved in the modulation of the electric activities of ARC *** response of ARC neurons to glutamic acid is sensitized in CFA-inflamed rats.

关键词： glutamic acid(Glu) NMDA receptor MK-801 arcuate nucleus(ARC) brain slice inflammation central sensitization

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Chinese Chemical letters 1998年第5期9卷 471-472页

作者： Bao Xin lI Wei QIN Zhu Jun ZHANG (Department of Chemistry, Shaanxi Normal university, Xi’an 710062) Shaanxi Normal Univ Dept Chem Xian 710062 Peoples R China

A novel chemiluminescence (Cl) sensor for H2O2 combined with flow injection analysis is described in this paper. H2O2 is sensed by the Cl reaction with luminol and Co2+ bleeding from the ion exchange column with immobilized reagents by hydrolysis. The calibration graph is linear and falls between the range of 4x10(-8) to 1x10(-5) mol/l. A complete analysis could be performed in 1 min. The system was reused for over 50 hours.

关键词： chemiluminescence H2O2 analysis luminol Co(II)

High mechanical strengths and ductility of stainless steel 304l fabricated using selective laser melting

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Journal of Materials Science & Technology 2019年第2期35卷 388-394页

作者： Q.B.Nguyen Z.Zhu F.l.Ng B.W.Chua S.M.l.Nai J.Wei Singapore Institute of Manufacturing Technology Institute of Research and Development Duy Tan University

Achieving not only high mechanical strengths but also high ductility is recently established using an additive manufacturing technique called selective laser melting. In the present study, stainless steel 304 l fully dense samples were successfully printed using the 3 D systems – ProX 300 printing machine. The ductility and tensile yield strength were almost two and three times higher compared to those of ASTM cast's alloy. Honey comb like nano-cellular structure with different orientation was observed in the fine grains(~4μm) due to fast cooling rate. In addition, the formation of martensite phase in random grains is also a contributor to the strengths. Furthermore, negative residual stresses in the build and horizontal directions were detected and assisted further increase in the tensile strength. Fractography revealed the ductile feature of plastic deformation and the crack openings at unmelted particles or pores.

关键词： Additive manufacturing Stainless steel Powder Selective laser melting

FINITE ElEMENT ANAlYSIS TO THE FATIGUE STRENGTH OF SYNCHRONOUS BElT TEETH

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Acta Metallurgica Sinica(English letters) 1999年第5期12卷 917-920页

作者： T.l Guo, Y. Qi and Y.H. Cheng Scientific Research Department, Shenyang university, Shenyang 110044,China

By means of finite element analysis methods calculated the stress, strainand displacement of the belt teeth and analysisied the factors such as load distribution,specific property coefficient of material and tempe... 详细信息

关键词： finite element analysis fatigue strength synchronous belt teeth

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生物质燃料颗粒热压成型过程分析

煤炭学报 2024年第2期49卷 1123-1137页

作者：张守玉黄健添郎森张邢佳陈旭阳梁宁吕邦勇杨楚轲胡南吴玉新吕俊复上海理工大学能源与动力工程学院上海200093 怀柔实验室山西研究院山西太原030032 长春工程学院吉林长春130012 清华大学能源与动力工程系北京100084

“双碳”战略下,生物质因其可再生、低污染和“零”碳排等优点而备受关注。生物质成型制备燃料颗粒能有效地解决其结构松散、能量密度低等问题,可用作化石燃料的替代品,对于新型能源体系的建设具有重要意义。笔者概述了生物质热压成型... 详细信息

“双碳”战略下,生物质因其可再生、低污染和“零”碳排等优点而备受关注。生物质成型制备燃料颗粒能有效地解决其结构松散、能量密度低等问题,可用作化石燃料的替代品,对于新型能源体系的建设具有重要意义。笔者概述了生物质热压成型过程的影响因素,分析并探讨了热压成型过程中生物质颗粒的演变行为和结合机制。生物质成型工艺主要包括冷压成型和热压成型。与冷压成型相比,热压成型能耗较低,制得成型燃料品质较高。生物质含水率(4%~15%)对其成型燃料密度影响较大,成型温度(70~150℃)影响较小,成型压力(60~130 MPa)和原料粒度(2.5 mm)对其成型燃料密度的影响因生物质种类不同而存在较大差异。生物质热压成型过程中纤维素主要起骨架支撑作用,半纤维素、木质素则起到黏结剂作用。在热压成型的微观过程中,生物质颗粒经惯性移动后黏弹塑性变形,形成机械互锁。脆性颗粒破碎后释放出天然黏性成分,在水分、温度和压力的共同作用下形成颗粒间桥接。机械互锁和桥接缩小了生物质分子间的距离,促进了分子间作用力的产生。在对生物质热压成型机制认识的基础上,利用不同生物质掺混或水热等预处理手段对生物质组分进行调控可提高燃料颗粒的品质。利用分子动力学手段对生物质成型过程进行仿真模拟,可获得生物质组分分子间的键合机制,有利于进一步探究生物质热压成型机制,对生物质成型燃料乃至成型材料的制备有着重要的指导意义。

关键词：生物质成型分子间作用力机械互锁桥接