29 resultados para 1463

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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This paper provides a numerical approach on achieving the limit equilibrium method for 3D slope stability analysis proposed in the theoretical part of the previous paper. Some programming techniques are presented to ensure the maneuverability of the method. Three examples are introduced to illustrate the use of this method. The results are given in detail such as the local factor of safety and local potential sliding direction for a slope. As the method is an extension of 2D Janbu's generalized procedure of slices (GPS), the results obtained by GPS for the longitudinal sections of a slope are also given for comparison with the 3D results. A practical landslide in Yunyang, the Three Gorges, of China, is also analyzed by the present method. Moreover, the proposed method has the advantages and disadvantages of GPS. The problem frequently encountered in calculation process is still about the convergency, especially in analyzing the stability of a cutting corner. Some advice on discretization is given to ensure convergence when the present method is used. However, the problem about convergency still needs to be further explored based on the rigorous theoretical background.

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采用了新型的转捩预测模式,将间歇因子耦合到湍流脉动输运方程中去,计及流体转捩的内在因素,因而能够反映转捩的具体发展过程.以二维不可压平板边界层和二维NACA0012翼型为例,研究了该转捩模式在预测不可压转捩流动时的作用,得到与实验值符合良好的计算结果.同时也研究了该转捩模式在不同网格分辨率下的计算能力和对近壁面网格分辨率的要求.

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The Yb:Y3Al5O12/Y3Al5O12 (Yb:YAG/YAG) composite crystals were prepared by thermal bonding method with different technological parameters. The bonding interface of the composite crystals were observed by optical microscope, scanning electron microscope, and atom force microscope. The light scattering experiments for bonding interface of the composite crystals were measured by the laser and transmission spectra. All experiments show that high-quality Yb:YAG/YAG composite crystals without space transition layer and light scattering on the bonding interface can be obtained by thermal bonding method under appropriate technological parameters.

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在研究阶段离子束辅助制备方式对薄膜性质影响的基础上,采用电子枪蒸发及离子束辅助沉积制备了氧化铪及氧化硅单层膜,采用阶段离子束辅助沉积及全程非离子束辅助沉积制备了基频减反膜。测量了所有样品的弱吸收、残余应力和激光损伤阈值。结果发现,相对电子枪热蒸发制备的样品,离子束辅助沉积的单层膜具有大的弱吸收、低的激光损伤阈值,且张应力减小,压应力增加;阶段离子束辅助沉积制备的减反膜剩余应力变小,弱吸收稍微增加,激光损伤阈值从10.91 J/cm^2增加到18 J/cm^2。分析表明,离子束辅助沉积在引入提高样品激光损伤

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巴山冷杉主要分布于秦巴山地,是湖北神农架地区暗针叶林的建群种,构成了当地的优势群落,对神农架地区的植被景观具有决定意义。研究巴山冷杉的结实特性,种子雨时空格局,种子萌发能力和活力劣变过程,有利于进一步认识和分析这一物种的生活史特征,群落组成结构和更新动态。对这一重要物种的合理保护和有效利用具有促进作用。 在湖北神农架自然保护区选择巴山冷杉-箭竹、巴山冷杉-茵芋和巴山冷杉-陕甘花楸群落设置样地,通过布设种子收集器结合室内实验分析,对巴山冷杉种子雨的时空格局进行研究。待巴山冷杉球果成熟时,人工采集球果和种子,测量和比较巴山冷杉的结实特征,利用发芽实验研究巴山冷杉的萌发特性,并通过人工加速老化实验探讨巴山冷杉种子的劣变过程。 巴山冷杉种子雨始于10月初,持续超过2个月,不同类型的巴山冷杉种群表现出不同的种子雨时空格局。巴山冷杉-箭竹群落中巴山冷杉种子雨平均强度167.93±111.14粒/m2,有活力种子比例占22.31%,落种高峰期集中于10月27日到11月2日间,种子雨在种群中呈现聚集分布。巴山冷杉-茵芋群落种子雨强度在三个样地中最小,只有16.41±14.41粒/m2,有活力种子仅占3.05%。巴山冷杉-陕甘花楸群落,种子雨落种高峰为10月15日至10月21日,林冠内种子雨数量占到了收集总数的87.95%。扩散的种子数量与离开中心母树的距离间的关系近似正态分布。 对巴山冷杉的结实特性的分析结果表明,巴山冷杉球果近圆柱形,球果平均长5.37±0.75cm;平均宽3.01±0.32cm;重量介于5.9g~41.3g。巴山冷杉种子长1.08~8.68mm,种子宽1.16~6.42mm,种子厚0.66~3.48mm,种子千粒重7.30g。球果单果出种量在不同种群的频数分布格局不同,巴山冷杉球果和种子的各项指标在种群间和种群内存在显著差异。球果大小、出种量及单粒种子的质量间存在着极显著的正相关关系。此外,种子生活力水平在母树间差异较大,不同母树的种子发芽率和发芽势不等且随时间的萌发进程也不相同,相同种源的巴山冷杉种子在不同的培养条件下萌发能力不同,室温条件下具有最高的发芽率但在25℃,8h光照,恒温培养时的萌发最为整齐。 高温高湿条件能够加速巴山冷杉种子的老化进程,使巴山冷杉种子的含水量发生变化,种子的活力水平随着老化时间的延长而降低,40℃,100% 相对湿度处理6天后种子基本丧失活力。

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目的探讨p53基固在乳腺癌发生早期的作用及早期诊断乳晾瘟的分子病理指标。方法用PCR—sso 法检测36例乳腺单纯性增生、31例不典型增生、14例原位癌和16例程润癌中p53基因第7外显子突变,井用叭A 直接测序技术确定突变的碱基及其所在的密码子。结果乳腺单纯性增生、不典型增生、原位癌、浸润癌中|】53基 因第7外显于的突变率分别为0%、6 5%(2/31)、21 4%(3/14)、18.8%(3/16)。8例突变中,3例发生于251密码 子,4例发生手248密码子,I例发生于236密码子。表现为碱基替换(5例)、缺失(2例)、插入(J例)共二种突变方 式。并在I例原位瘟中首次发现了251密码子的同义突变(ATC斗ATr,异亮氨酸一异亮氮酸)。结论乳腺癌不典 型增生中存在053基因第7外显子突变,该突变可能在乳腺不典型增生发展到乳腺癌的过程中起霞要作用,可作为 早期诊断乳腺癌的辅助指标。

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目的观察纯化的云南眼镜蛇毒因子(Y-CVF)对预致敏大鼠同种心脏移植急性体液排斥反应的作用。方法BN大鼠到Lewis大鼠连续3次皮肤移植预致敏后行颈部异位心脏移植。将15对大鼠用随机数字法分成2组,实验组(n=8)于心脏移植前24h静脉给予Y-CVF80μg/kg;对照组(n=7)不用Y-CVF。观察移植心的生存时间,移植心停跳后病理学检查排斥类型,免疫组织化学染色观察移植心IgG和补体C3的沉积。结果Lewis大鼠预致敏后抗BN大鼠抗体滴度由0升高至1∶1028~1∶2056。对照组移植心存活时间为12·71h±13·94h,实验组移植心存活时间为99·50h±38·72h,与对照组比较差异有统计学意义(t=5·599,P<0·01)。病理检查结果证实,实验组均未发生急性体液排斥,仅见以大量单核淋巴细胞浸润为特征的急性细胞排斥反应。对照组则见以小血管内血栓形成为特征的急性体液排斥反应。免疫组织化学IgG染色实验组和对照组均为阳性,C3染色对照组为阳性,而实验组为阴性。结论使用Y-CVF可克服预致敏大鼠同种心脏移植急性体液排斥反应的发生。

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<正> 青海省青海湖是我国最大的內陆湖,湖水的化学性貭,过去仅有俄国科学院的Schmidt以在1872年和1880年先后在青海湖南部采得的水样进行过分析,測定湖水中总盐量为11.1463—13.5937%,其中含氯量为4.2889—5.4029%。作者等于1956年8月間在青海湖調查时,曾进行了湖的东、南、西三部分湖水的理化性貭观察和分析,其結果如表所列。青海湖面积将近4,000平方公里,湖床平坦,湖水平均深度在25米以上,最深处有31.4米。湖水在

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1. We studied driving forces shaping phytoplankton assemblages in two subtropical plateau lakes with contrasting trophic status, the oligotrophic deep Lake Fuxian and the eutrophic shallow Lake Xingyun. 2. Phytoplankton samples were taken monthly for a year and phytoplankton species were sorted into the main taxonomic groups and associations proposed by Reynolds. A canonical correspondence analysis (CCA) was used to test the occurrence of these classification schemes and to determine their discriminatory power. 3. The results suggest that the major driving forces in Lake Fuxian were physical variables, and particularly the underwater light climate, whereas, nutrients were the important driving force in Lake Xingyun. 4. Top-down control through zooplankton grazing in Lake Fuxian was hardly ever a significant determinant itself, because of the scarcity of zooplankton and their low grazing efficiency of predation while a dominance of inedible cyanobacteria throughout the year rendered top-down controls ineffective failing in Lake Xingyun. Hence phytoplankton communities in both lakes appear to be regulated primarily by bottom-up controls.

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The nematode Camallanus hypophthalmichthys Dogel and Akhmerov, 1959 is redescribed from specimens collected from the intestine of the bighead carp Aristichthys nobilis, from Liangzihu Lake (Yangtze River basin), Hubei Province, central China. The light and scanning electron microscopical examination made it possible to study in detail the morphology of this so far little-known species and to confirm its validity. The main specific features of C. hypophthalmichthys distinguishing it from the most similar Camallanus spp. is the presence of 3 small caudal processes on the male tail tip, 13-16 longitudinal ridges on the inner surface of the valve of the buccal capsule, and the arrangement of preanal and postanal genital papillae in the male. This finding represents a new host record, the first record of this parasite in the Yangtze River basin, and the first documented record of C. hypophthalmichthys from China. Camallanus hypophthalmichthys is considered a specific intestinal parasite of fishes of the cyprinid Hypophthalmichthyinae.

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A new device of two parallel distributed feedback (DFB) lasers integrated monolithically with Y-branch waveguide coupler was fabricated by means of quantum well intermixing. Optical microwave signal was generated in the Y-branch waveguide coupler through frequency beating of the two laser modes coming from two DFB laser in parallel, which had a small difference in frequency. Continuous rapid tuning of optical microwave signal from 13 to 42 GHz were realized by adjusting independently the driving currents injected into the two DFB lasers.