955 resultados para 30-289_Site
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论文利用近30a中国756个气象站点日观测数据计算中国陆地表层潜在蒸散和湿润指数现状及变化趋势,然后划分湿润程度变化对不同自然地带生态系统脆弱性影响的等级,并应用于农田、林地和草地三大生态系统脆弱性变化分析,结果显示:近30a中国陆地表层平均年潜在蒸散为754mm,平均湿润指数为-5.6,湿润指数平均变化率为-4.4/10a,反映中国陆地表层湿润程度总体具有下降趋势。近30a中国陆地表层气候湿润程度变化导致生态系统脆弱性增加的面积约占中国陆地面积的43.7%,主要集中在东北地区西南部、华北地区、西北地区东部,以及青藏高原的西部、北部和东部。总体上,近30a中国陆地表层气候湿润程度变化对农田、林地和草地生态系统脆弱性具有不利影响。其中草地生态系统脆弱性增加的面积最大,约占草地生态系统总面积的63.2%;其次为农田生态系统,约占31.6%;林地生态系统脆弱性受影响面积最小,约占17.7%。
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We obtained four phases of land cover spatial data sets by interpreting MSS images of middle and late 1970s and three phases of TM images of late 1980s, 2004 and 2008 based on field investigation in Three Rivers' Source Region. We analyzed the temporal and spatial characteristics of land cover and macro ecological changes in Three Rivers' Source Region in Qinghai-Tibet plateau since middle and late 1970s. Indicated by land cover condition index change rate and land cover change index, land cover and macroscopical ecological condition degenerated (7090 period Zc -0.63, LCCI -0.58)-obviously degenerated (9004 period, Zc -0.94, LCCI -1.76)-slightly meliorated (0408 period, Zc 0.06, LCCI 0.33). This course was jointly driven by climate change, grassland stocking pressure and implement of ecological construction project.
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The structure and electrochemical characteristics of melted composite Ti0.10Zr0.15V0.35Cr0.10Ni0.30+x% LaNi5 (x=0, 1, 5 and 10) hydrogen storage alloys have been investigated systematically. XRD shows that the matrix phase structure of V-based solid solution phase with a BCC structure and C14 Laves phase with hexagonal structure is not changed after adding LaNi5 alloy. However, the amount of the secondary phase increases with increasing LaNi5 content. Field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS) shows that the C14 Laves phase contains more Zr and the white lard phase has a composition close to (Zr, Ti)(V, Cr, Ni, La)(2).
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Effect of La-Mg-based alloy (AB(5)) addition on Structure and electrochemical characteristics of Ti0.10Zr0.15V0.35Cr0.10Ni0.30 hydrogen storage alloy has been investigated systematically. XRD shows that the matrix phase structure is not changed after adding AB(5) alloy, however, the amount of the secondary phase increases with increasing AB(5) alloy content. The electrochemical measurements show that the plateau pressure Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + x% La0.85Mg0.25Ni4.5Co0.35Al0.15 (X = 0, 1, 5, 10, 20) hydrogen storage alloys increase with increasing x, and the width of the pressure plateau first increases when x increases from 0 to 5 and then decreases as x increases further, and the maximum discharge capacity changes in the same trend.
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The structure and electrochemical characteristics of melted composite Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + x% LaNi4Al0.4Mn0.3Co0.3 (x = 0, 1, 5) hydrogen storage alloys have been investigated systematically. XRD shows that though the main phase of the matrix alloy remains unchanged after LaNi4Al0.4Mn0.3Co0.3 alloy is added, a new specimen is formed. The amount of the new specimen increases with increasing x. SEM-EDS analysis indicates that the V-based solid solution phase is mainly composed of V, Cr and Ni; C14 Laves phase is mainly composed of Ni, Zr and V; the new specimen containing La is mainly composed of Zr, V and Ni. The electrochemical measurements suggest that the activation performance, the low temperature discharge ability, the high rate discharge ability and the cyclic stability of composite alloy electrodes increase greatly with the growth of x.
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The electrochemical properties of the Ti0.17Zr0.08V0.35Cr0.10Ni0.30 alloy electrode were investigated. This alloy has good cycle life at 303 K, 313 K, and even at 323 K, but the discharge capacity decreases gradually at 333 K with increasing cycle number. Both the charge-discharge efficiency and the charge-discharge voltage reduce. The electrochemical impendence spectra indicate that the charge-transfer resistance decreases while the exchange current density increases as temperature increases. The apparent activation energy of the charge-transfer reaction is about 50 kJ mol(-1), which is higher than that on the AB(5) type alloy electrode.
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The phase transition and transition kinetics of a liquid crystalline copoly(amide-imide) (PAI37), which was synthesized from 70 mol% pyromellitic dianhydride, 30 mol% terephthaloyl chloride, and 1,3-bis[4-(4'-aminophenoxy)cumyl]benzene, was characterized by differential scanning calorimetry, polarized light microscopy, X-ray diffraction, and rheology. PAI37 exhibits a glass transition temperature at 182 degreesC followed by multiple phase transitions. The crystalline phase starts to melt at similar to 220 degreesC and forms smectic C (S-C) phase. The Sc phase transforms into smectic A (S-A) phase when the temperature is above 237 degreesC. The S-C to S-A transition spans a broad temperature range in which the S-A phase vanishes and forms isotropic melt. The WARD fiber pattern of PAI37 pulled from the anisotropic melt revealed an anomalous chain orientation, which was characterized by its layer normal perpendicular to the fiber direction. The transition kinetics for the mesophase and crystalline phase formation was also studied.
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聚醚酰亚胺(YS-30)是一种可溶性的聚酰亚胺,本文对它的 ̄(13)CNMR谱, ̄1NNMR谱和COSY谱进行了研究.经过分析,对 ̄(13)CNMR和 ̄1HNMR谱作出了归属,确认了聚醚酰亚胺的链结构.
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A simple and sensitive high-performance liquid chromatographic (HPLC) method with fluorescence detection and mass spectrometric identification has been developed for analysis of 30 long-chain and short-chain free Fatty acids (FFAs). The fatty acids were derivatized to their esters with 1-[2-(p-toluenesulfonate)ethyl]-2-phenylimidazole-[4,5-f]-9,10-phenanthrene (TSPP) in N,N-dimethylformamide (DMF) at 90 degrees C with anhydrous K2CO3 as catalyst. A mixture Of C-1-C-30 fatty acids was completely separated within 60 min by gradient elution on a reversed-phase C-8 column. Qualitative identification of the acids was performed by atmospheric-pressure chemical ionization mass spectrometry (APCI-MS) in positive-ion mode. The fluorescence excitation and emission wavelengths were 260 and 380 nm, respectively. Quantitative determination of the 30 acids in two Tibetan medicines Gentiana straminea and G. dahurica was performed. The results indicated that the medicines contained many FFAs. Linear correlation coefficients for the FFA derivatives were > 0.9991. Relative standard deviations (RSDs, n = 6) for the fatty acid derivatives were < 3%. Detection limits (at a signal-to-noise ratio of 3:1) were 3.1-38 fmol. When the fatty acid derivatives were determined in the two real samples results were satisfactory and the sensitivity and reproducibility of the method were good.
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1972年刘东生院土撰文发表了“环境地质学的出现”。中国科学院地球化学研究所环境地球化学国家重点实验室于1992年正式成立,刘东生院士的环境地质学学术观点聚焦于:环境地质学发展的动力源于社会需要,地球环境系统的整体性及其与人类关系的相互依存性。30年来,地质环境的地球化学研究以区域环境质量和全球环境变化两大科学问题作了基本目标,经历了调查评价,区域综合和界面机理3个发展阶段,研究重点是典型区域环境演化的发生学原理,谱系特征以及健康和生态效应,云贵高原地质环境的特殊性显示出青藏隆起对周边现代环境的影响。环境地质学以“地质学与人类”为宗旨,将在21世纪为人类谋求更多的福利。
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2010
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2010
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2010
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A Embrapa Mandioca e Fruticultura Tropical instituiu há poucos anos atrás, os ?Dias dos Produtos? pesquisados pelo Centro. A data escolhida para a comemoração do ?Dia do Abacaxi? foi 04 de novembro. Isso porque foi nessa data que o navegador genovês, Cristóvão Colombo, em uma de suas históricas viagens, aportou na ilha de Guadalupe, e lá encontrou o abacaxi sendo cultivado pelos nativos. Impressionado pela beleza e forma da planta, pelo aroma e sabor do fruto, coletou alguns exemplares e os levou para a Europa, onde esse fruto teve grande aceitação. Em 2007, a comemoração do ?Dia do Abacaxi? foi adiada e ocorreu no dia 10/12/2007 à tarde, e também teve uma programação diferente, da qual constou, além da confraternização informal de praxe, uma sessão técnica composta de um painel. Nesse painel foram apresentadas quatro palestras referentes a alguns dos impactos e avanços obtidos pela Equipe Técnica de Abacaxi /ETA, da Unidade, ao longo de sua existência. Os temas das palestras versaram sobre o VI Simpósio Internacional de Abacaxi (pela primeira vez realizado no continente sulamericano e, mais especificamente, no Brasil); fitossanidade (fusariose) e produção integrada (com destaque para o Tocantins); melhoramento genético (híbridos resistentes e herança da resistência); usos alternativos do abacaxi (como ornamental, flor de corte, de vaso e de jardim); e aspectos econômicos e de mercado (peso médio do fruto brasileiro e posição do Brasil no mercado internacional). As palestras foram apresentadas, respectivamente, pelos pesquisadores Domingo Haroldo Reinhardt (coordenador do simpósio), Aristóteles Pires de Matos, José Renato Santos Cabral, Janay dos Santos-Serejo, Fernanda Vidigal Duarte Souza e Clóvis Oliveira de Almeida.