239 resultados para 341.584


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该文依据英国南安普郭海洋中心气候学海面通量资料集,采用EOF及一般统计分析方法,分析和研究了中国近海热通量、淡水通量及由动量通量计算而得的风应力旋度场的气候平均和季节变化特征.并分别对日本海、渤黄东海及南海进行了讨论.结果显示,日本海与渤黄东海年平均海面净热通量为失热,日本海为-27Wm<'-2>,渤黄东海为-25Wm<'-2>.南海为海洋获得净热通量,量值为58Wm<'-2>.在黑潮流区存在最大的净热通量损失值区,在冬季12月份最大损失值可达-330Wm<'-2>.在日本海区对马暖流沿日本群岛西海岸在冬季12月也有最大损失值-270Wm<'-2>.日本海与东中国海净热通量变化趋势基本一致,而南海在4月达到净热通量的最大值.最后该文还对海表通量与海表温度场及风速场作了延迟相关分析.

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Matrix-bound phosphine was determined in the Jiaozhou Bay coastal sediment, in prawn-pond bottom soil, in the eutrophic lake Wulonglan, in the sewage sludge and in paddy soil as well. Results showed that matrix-bound phosphine levels in freshwater and coastal sediment, as well as in sewage sludge, are significantly higher than that in paddy soil. The correlation between matrix bound phosphine concentrations and organic phosphorus contents in sediment samples is discussed.

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Three new bromophenols C-N coupled with nucleoside base derivatives (1-3) and three new brominated 1,2,3,4-tetrahydroisoquinolines (5-7, together with a new brominated tyrosine derivative (4, have been isolated from polar fractions of an ethanolic extract of the red alga Rhodomela confervoides. By spectroscopic and chemical methods including HRMS and 2D NMR data, their structures were determined as 7-[3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]-3,7-dihydro-1H-purine-2,6-dione (1), 7-(2,3-dibromo-4,5-dihydroxybenzyl)-3,7-dihydro-1H-purine-2,6-dione (2, 9-[3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl]adenine (3), (-)-8S-(3-bromo-5-hydroxy-4-methoxy)phenylalanine (4), (-)-3S-8-bromo-6-hydroxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (5), methyl (-)-3S-8-bromo-6-hydroxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylate (6), and methyl (-)-3S-6-bromo-8-hydroxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylate (7). Compounds 5-7 were semisynthesized by using 4 as the starting material.

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Two different stocks (A and B) of the bay scallop Argopecten irradialls irradians (Lamarck, 1819) were used to test mass selection on growth. Stock A was a descending stock from the initial introduction from U.S.A. in 1982, which had been cultured in China for about 20 years. Stock B was the third generation from a recent introduction from U.S.A. in 1999. Truncation selection was conducted by selecting the largest 11% scallops in shell length from Stock A and the largest 12.7% scallops from Stock B as parents for the respective selected groups. Before the removal of parents for truncation selection, equal numbers of scallops were randomly chosen from Stock A and B to serve as parents for the control groups. Offspring from the four groups were reared under the same hatchery, nursery, and grow-out conditions. Values of response to selection and realized heritability at larvae, spat and grow-out stages for Stock B were all significantly (P < 0.001) higher than its counterpart for Stock A. For Stock A, no significant response to selection was observed (P > 0.05) at any stage, and the realized heritability for shell length was 0.015 +/- 0.024 for larvae, 0.040 +/- 0.027 for spat, and 0.080 +/- 0.009 for grow-out, respectively. For Stock B, however, significant (P < 0.05) response to selection was observed, and the realized heritability for shell length was 0.511 +/- 0.010 for larvae, 0.341 +/- 0.022 for spat, and 0.338 +/- 0.015 for grow-out. On average, responses to selection at the three stages for Stock B was 30 x, 7.1 x, and 3 x higher than its counterpart for Stock A, respectively. Accordingly, realized heritability at above stages for Stock B was 33 X, 7.5 x, and 3.2 X higher than its counterpart for Stock A, respectively. Differences in response to selection and realized heritability between the two stocks are presumably due to differences in genetic variability. As the 20th generation from the initial introduction consisted of only 26 scallops, Stock A is known to be highly inbred, while inbreeding in Stock B is negligible. (C) 2004 Elsevier B.V. All rights reserved.

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Three kinds of Schiff bases of carboxymethyl chitosan (CMCTS) were prepared, and their antifungal activities were assessed according to Jasso de Rodriguez's method. The results indicated that 2-(2-hydroxybenzylideneamino)-6-carboxymethylchitosan (HNCMCTS) and 2-(5-chloro-2-hydroxybenzylideneamino)-6-carboxymethylchitosan (HCCMCTS) had better inhibitory effects than those of chitosan or CMCTS against Fusarium oxysporium f. sp. vasinfectum, Alternaria solani, and Valsa mali. (c) 2005 Elsevier Ltd. All rights reserved.

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茄科的多数种类具有自交不亲和的特点,主要通过异花传粉结实;但是,一些物种或者物种内的部分种群或者个体却高度自交亲合,转变为自交的繁育系统.该科植物山莨菪(Anisodus tanguticus)主要分布在青藏高原,开花较早,比其他晚开花的植物种类更加缺少有效的异花传粉昆虫.我们选择了位于不同海拔高度的2个种群进行比较研究,主要目的是检验该物种的繁育系统是否在极端环境下由于传粉者的缺乏而发生了部分改变.研究发现,山莨菪的花不完全雌性先熟,柱头和花药间的平均距离随着花开放时间的延长而不断缩小,但两者在多数花的单花花期结束时并没有发生接触.因此,山莨菪花主要表现为适应异花传粉的雌雄异位特征.然而,少数花 (4.9%)的柱头和花药发生接触,为"自动自交"的传粉解除了空间隔离.2个种群的多数个体存在自交不亲和机制,应具有异花传粉的繁育系统;但是部分个体具有明显的自交亲和能力,为自交提供了生理基础.高海拔种群的传粉昆虫主要是厕蝇(Fannia sp.),它们在不同植株间的活动能够保证异花传粉结实;同时该种群的部分个体存在"自动自交".低海拔种群的主要访花昆虫是蚂蚁,它们在花内的活动导致花粉在同一朵花内传递,而引起"协助自交";而异花传粉昆虫厕蝇的访花频率则较高海拔种群低.两个种群的结实均由于异花传粉者不足而受到传粉限制.因此两种不同类型的自交机制为该早期开花植物异花访花昆虫的不足提供了一定程度上的繁殖补偿.

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对海北定位站分布的金露梅灌丛草甸、矮嵩草草甸、藏嵩草沼泽化草甸3种高寒植被类型群落结构、感热(H)和潜热(LE)通量比较观测表明,3种植被类型年地上净初级生产力表现出矮嵩草草甸(318.600 g/m~2)>藏嵩草沼泽化草甸(258.341 g/m~2)>金露梅灌丛草甸(217.6 g/m~2).植物种类组成有矮嵩草草甸(54种)>金露梅灌丛草甸(47种)>沼泽草甸(24种).3种植被类型区近地表大气能量交换过程中,LE和H的月际变化明显,而且随植被类型的不同月际变化差异显著.3种不同植被类型在年内均表现出H+L E>0,表明在青海海北高寒草甸地区,太阳辐射强烈,近地层湍流输送明显,地表为-热源.3类型高寒草甸植被的年地上净生产量基本与波文比(β)呈现正效应,与LE+H呈现明显的反效应.植物种类组成基本与LE+H有反效应,与β呈明显的正效应.

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为了解青海省春小麦收割后田间堆放期间产量和品质的变化,选择近年育成的春小麦品种“高原205”(白粒,易穗发芽)、“高原115”(紫黑色小麦)、“高原448”(红粒)和“高原314”(白粒)以及曾为青海省主栽品种的“青春533”(红粒)为材料,收割后以农民常用的田间堆放方式进行堆放,每隔9d对其进行采样,测定产量、SDS沉淀值和降落数值的变化。结果表明,随着堆放时间的延长,收获产量逐步下降,平均产量从第1次采样(Od)时的504g/m^2减少到63d后的384g/m^2,收获产量平均值与取样时间直线回归F值为20.91,大于F0.01(6.90);SDS沉淀值变化较小,F值为0.90,小于F0.05(2.13);降落数值在取样时间点上差异极显著.F值等于46,72,大于F0.01(2.87)。高原205的降落数值一直呈现下降趋势,而高原448、高原115、高原314和青春533的变化是在O~18d间上升,然后下降。总体而言,田间堆放对收获产量和品质不利。

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以青海省三角城种羊场地区典型的芨芨草草原为研究对象,采用相邻格子样方法取样,应用方差/均值比率法、负二项参数(K);扩散系数(C);Cassie指标(CA);丛生指标(I)和聚块性指标(m^*/m)等指标,比较了青海湖地区围栏内、外芨芨草群落主要种群的空间分布格局。结果表明,围栏内芨芨草群落优势种群的空间格局除多裂蒲公英为随机分布外,其余均为聚集分布;围栏外除西伯利亚蓼外,其余种群也全部为聚集分布,而且围栏外种群的聚集强度大于围栏内。物种的这种分布格局主要与物种本身的生态和生物学特性有关。

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广袤的草地、特有的高寒湿地以及丰富而有又独特的生物多样性是江河源区重要的自然生物资源.草地占江河源区总土地面积的84.53%,是源区畜牧业经济发展的基础,同时也是长江、黄河和澜沧江三大江河的源头区域,为江河中、下游地区生态环境稳定和经济持续发展提供无可替代的服务.江河源区是世界上海拔最高的高寒湿地主要分布区,湿地总面积达8 000 km2.江河源区独特的生态环境孕育了种类繁多的特有动、植物种类,源区约有哺乳动物、鸟类和鱼类133、249和219种,牧草植物、药用植物、食用植物和观赏植物约800、808、80和400种,是世界海拔最高的生物多样性集中分布区.然而,由于超载放牧、盲目采挖、盗猎等不合理的开发和利用以及气候变化等诸多因素的综合影响,江河源区草地生态系统退化、高寒湿地萎缩、生物多样性锐减等生态环境危机不断加剧.正确权衡江河源区自然生物资源的短期经济价值及其所拥有的巨大生态公益和潜在开发价值,科学决策,保护江河源区自然生物资源迫在眉睫.

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To characterize evapotranspiration (ET) over grasslands on the Qinghai-Tibetan Plateau, we examined ET and its relevant environmental variables in a Kobresia meadow from 2002 to 2004 using the eddy covariance method. The annual precipitation changed greatly, with 554, 706, and 666 mm a(-1) for the three consecutive calendar years. The annual ET varied correspondingly to the annual precipitation with 341, 407, and 426 mm a(-1). The annual ET was, however, constant at about 60% of the annual precipitation. About 85% annual ET occurred during the growing season from May to September, and the averaged ET for this period was 1.90, 2.23, and 2.22 mm/d, respectively for the three consecutive years. The averaged ET was, however, very low (< 0.40 mm/d) during the nongrowing season from October to April. The annual canopy conductance (gc) and the Priestley-Taylor coefficient (a) showed the lowest values in the year with the lowest precipitation. This study first demonstrates that the alpine meadow ecosystem is characterized by a low ratio of annual ET to precipitation and that the interannual variation of ET is determined by annual precipitation.

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图像匹配是指把一个图像区域从另一个可能在不同时间,不同视点位置或者由不同传感器所获得的图像区域中确定出来或找到它们之间对应关系的一种重要的图像分析与处理技术。 实验结果验证是图像匹配中的一个重要环节。传统的图像匹配实验验证一般是在真实环境中进行。这种验证方式基本都面临实验周期长、成本高、安全性低、不易重复实验、可控性差、受气候条件、实验场地限制等诸多缺陷。在传统实物验证前,我们迫切需要寻找一种新的实验平台。虚拟现实技术的发展为我们构建新的实验平台提供了很好的技术支持代替传统方法。虚拟现实是一种由计算机和电子技术创造的看似真实的虚拟环境。通过多种传感设备,用户可根据自身的感觉,使用人的自然技能对虚拟世界中的物体进行考察和操作,参与其中的事件;同时提供视、听、触等直观而又自然的实时感知,并使参与者“沉浸”于虚拟环境中。作为虚拟现实行业的引导者,由Multigen-Paradigm公司开发的Creator三维建模软件和Vega实时可视化三维视景仿真软件已经广泛应用各种行业。本文采用这两种软件作为我们实验平台的开发工具。结果表明利用虚拟现实技术构建的仿真实验平台能够提供图像和数据,保证图像匹配实验的进行。 基于特征的图像匹配方法是提取图像中的一些特征点,然后借助这些特征点进行匹配。它能够较好的克服基于区域图像匹配算法易受实时性、光照、几何畸变等影响的缺点。边缘特征作为图像的一种基本特征已经广泛应用于图像匹配算法之中。传统的边缘检测方法(如Sobel、Prewitt和Canny算法)对噪声很敏感。 小波变换具有检测局部突变的能力,并且对图像噪声鲁棒,因此是检测图像边缘的有效工具。本文利用小波变换作为图像边缘检测工具,首先对图像分别做两方向的小波变换,进而得到二维小波变换的幅值和梯度,然后利用非极大值抑制方法检测二维小波变换的模极值点作为图像的边缘点。最后利用边缘直方图描述符实现模板边缘与实时图像边缘之间的匹配。 本文完成的主要工作如下: 1、 利用虚拟现实技术进行视景生成,构建图像匹配实验平台。输出实时图像以及加干扰的摄像机拍摄时所对应的水平角、俯仰角、自旋角、高度等指令参数。 2、 根据实时图像及对应参数,利用几何变换将前视图像转换为下视图像。 3、 在图像匹配中,我们在分析传统的边缘检测算子如Sobel、Prewitt、Canny等对噪声敏感的基础上,提出一种基于小波变换的图像边缘检测算法。 本文的实验环境为Vega、VC6.0++、Matlab7.0 实验结果表明本文所提出算法的有效性。

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给出了一种超高压输电线路巡检机器人控制系统的设计与实现方法.根据机器人的作业任务,提出了基于传感器信息、约束信息以及动作反馈信息作为输入,产生式系统作为动作输出的越障控制方式.仿真结果表明此方法对于机器人的越障过程是有效的.

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提出了一种基于神经网络的逆控制的水下机器人解耦控制策略,解耦过程无需系统的精确数学模型,将变量间的耦合直接按照干扰处理,通过自适应逆控制中的扰动消除原理进行去祸设计。仿真结果表明,该算法原理简单、鲁棒性强、解耦效果良好。

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以产于四川龙门山地区泥盆系观雾山组的有铰纲腕足化石Independatrypa lemma Chen为研究对象,利用激光熔样等离子质谱(LA-ICP-MS)对其壳体棱柱层中Fe、Mg、Mn、Na、Ba和Sr六种微量元素进行了就位分析。它们在壳体横切面中的对称分布特征总体上与壳体增生方式和过程相一致,表明壳体的绝大部分未经成岩作用的改造。与常用的结构判据、阴极发光判据和微量元素含量判据相比较,微量元.