943 resultados para Terrestrial Locomotion


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The effects of gravity and crystal orientation on the dissolution of GaSb into InSb melt and the recrystallization of InGaSb were investigated under microgravity condition using a Chinese recoverable satellite and under normal gravity condition on earth. To investigate the effect of gravity on the solid/liquid interface and compositional profiles. a numerical simulation was carried out. The InSb crystal melted at 525 degrees C and then a part of GaSb dissolved into the InSb melt during heating to 706 degrees C and this process led to the formation of InGaSb solution. InGaSb solidified during the cooling process. The experimental and calculation results clearly show that the shape of the solid/liquid interface and compositional profiles in the solution were significantly affected by gravity. Under microgravity, as the Ga compositional profiles were uniform in the radial direction. the interfaces were almost parallel. On the contrary, for normal gravity condition, as large amounts of Ga moved up in the upper region due to buoyancy, the dissolved zone broadened towards gravitational direction. Also. during the cooling process, needle crystals of InGaSb started appearing and the value of x of InxGa1-xSb crystals increased with the decrease of temperature. The GaSb with the (111)B plane dissolved into the InSb melt much more than that of the (111)A plane. (C) 2000 Elsevier Science B.V. All rights reserved.

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In this paper, a wide-band low noise amplifier, two mixers and a VCO with its buffers implemented in 50GHz 0.35 mu m SiGe BiCMOS technology for dual-conversion digital TV tuner front-end is presented. The LNA and up-converting mixer utilizes current injection technology to achieve high linearity. Without using inductors, the LNA achieves 0.1-1GHz wide bandwidth and 18.8-dB gain with less than 1.4-dB gain variation. The noise figure of the LNA is less than 5dB and its 1dB compression point is -2 dBm. The IIP3 of two mixers is 25-dBm. The measurement results show that the VCO has -127.27-dBc/Hz phase noise at 1-MHz offset and a linear gain of 32.4-MHz/V between 990-MHz and 1.14-GHz. The whole chip consume 253mW power with 5-V supply.

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This paper presents the design of a wide-band low-noise amplifier (LNA) implemented in a 0.35 mu m SiGe BiCMOS technology for cable (DVB-C) and terrestrial (DVB-T) tuner applications. The LNA utilizes current injection to achieve high linearity. Without using inductors, the LNA achieves 0.1-1GHz wide bandwidth and 18.8-dB gain with less than 1.4-dB gain variation. The noise figure(NF) of the wideband LNA is 5dB, its 1-dB compression point is -2dBm and IIP3 is 8dBm. The LNA dissipates 120mW power with a 5-V supply.

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We present the design of a wide-band low-noise amplifier (LNA) implemented in 0.35μm SiGe BiCMOS technology for cable and terrestrial tuner applications. The LNA utilizes current injection to achieve high linearity. Without using inductors, the LNA achieves 0.1 ~ 1GHz wide bandwidth and 18. 8dB gain with less than 1.4dB of gain variation. The noise figure of the wideband LNA is 5dB, and its 1dB compression point is - 2dBm and IIP3 is 8dBm. The LNA dissipates 120mW of power with a 5V supply.

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本文考察了若尔盖高寒泥炭湿地公路对高原林蛙(Rana kukunoris)、倭蛙(Narorana pleskei)和岷山蟾蜍(Bufo minshanicus)的生态影响。分析了公路对两栖动物空间分布和栖息地利用的影响,并用IBM模型探讨其可能作用机制,考察了两栖动物公路死亡的季节差异及影响公路死亡空间分布的景观因素。最后通过对若尔盖高寒湿地两栖动物陆地核心栖息地的分析,为若尔盖路域栖息地的管理提供依据。 1. 对公路周边6个沼泽水凼群进行了调查,每个样地设置5条样线(距离公路10m、20m、50m、100m和150m)。调查表明,在繁殖季节(5月),距离公路距离对高原林蛙和倭蛙的相对数量都有显著作用,其效应明显大于其他各项栖息地环境参数。公路导致高原林蛙和倭蛙在公路周边种群密度降低,其相对数量从距离公路100m处到公路边缘一直呈现逐渐降低的趋势。在繁殖季节,若尔盖高寒湿地的公路生态影响域大约在100-150m之间,这一距离远远大于森林栖息地中公路对两栖类的生态影响域(35-40 m)。 在繁殖后期(9月),对公路周边16个草地样点的样线调查表明,公路对周边高原林蛙和倭蛙密度分布并未造成显著影响。 2. 二次模型的拟合表明繁殖季节高原林蛙和倭蛙在公路周边的密度分布符合钟型曲线。前人对森林公路两侧两栖类分布的研究也显示了类似的规律。我们通过基于个体的模型,模拟在了公路边缘100单位距离内的栖息地空间,栖息地环境质量呈梯度变化,动物个体在其中通过随机运动寻找适宜的栖息地。拟合结果表明,动物个体仅仅依照简单的运动规则寻找适宜栖息地,这种活动就可以导致公路周边栖息地中的动物分布曲线出现3个局部峰。公路周边两栖动物的钟型分布曲线可能仅仅是个体寻找适宜栖息地过程中出现的临时性群体分布模式。 3. 在若尔盖高寒湿地,公路交通造成了大量两栖类死亡。但是公路两栖类动物死亡的季节分布很不均匀:5月、8月和9月死亡数量很高,而7月和10月死亡数量却很低。这种季节性差异和两栖类各个生活史阶段的迁移运动有密切的关系。利用景观参数的逻辑斯蒂回归模型显示,距离公路1000-2000m范围内的湿草地比例对三种两栖类公路死亡概率均有很强的贡献。湿草地这一栖息地类型分类中有大量的沼泽水体,是两栖类重要的繁殖点和取食点。两栖类公路死亡概率湿草地的关系从一个侧面表明,要维持一个区域较高的两栖类种群数量,需要1000-2000m半径范围内存在大面积的湿草地。 4. 高原林蛙和岷山蟾蜍不同性别和年龄个体分布点的水体距离存在显著差异。不同种类、年龄的两栖类分布点距离水体距离的差异可能是由于对水体的依赖性造成的。而相同种类、年龄段的个体中,高原林蛙雌性、岷山蟾蜍亚成体和雌性的体重与分布点距水体距离有显著负相关,这可能是因为体重更大的个体对水体的依赖性更弱。考虑到过大的陆地核心栖息地面积在实际保护工作中存在操作上的困难,因此我们认为可以以水体周边90%个体的分布区为低限确定3种两栖类的最小陆地核心栖息地。但是,在同样的水体距离-两栖类密度分布格局下,水体的面积和分形参数对最小陆地核心栖息地半径的确定有一定影响。 Ecological effects of alpine wetland road on Rana kukunoris, Narorana pleskei, Bufo minshanicus was studied in Zoige wetland. The effects of road on distribution of amphibians and its possible underline mechanism was discussed based on empirical data and computer simulation. Road killed amphibians was surveyed in different season and those landscape factor which could have impact on road killing distribution was analyses. Core terrestrial habitat of amphibians in Zoige wetland was discussed in the consideration of conservation management. 1. Six pool groups was investigated in breeding season (May) of R. kukunoris, N. pleskei. Five transects at distance of 10m, 20m, 50m, 100m and 150m from road edge was surveyed in each pool groups. There was a significant effects of distance from road edge on relative counts of R. kukunoris, N. pleskei, which is much important than effects of other environmental factors. Road caused the density of R. kukunoris, N. pleskei decreased from distance of 100m from road to 10m from road. Road ecological effect zone of alpine wetland for amphibians is about 100-150m. It is much wider than those of forest roads, which is about 35-40m. However, studies on 16 grassland near road showed no significant effect of road on amphibians after breeding season (Sep.). 2. Quadratic model fit indicated that the distribution of R. kukunoris and N. Pleskei followed a hump like curve. Previous studies on forest road showed similar results. A 100×100 habitat with gradual environment besides road was simulated with a individual-based model, and animal seek for suitable habitat with stochastic locomotion in it. Simulation results indicated that 3 density peak of animal distribution can emergent followed a simply rules. The hump like density cure could be a temporal swarm pattern during the process of individual seeking for habitat. 3. Road traffic caused mass death of amphibians in Zoige wetland. There was much road killed amphibians in May, Aug and Sep than those in July and Oct. The fluctuation of road kill could be related with migration of amphibians between seasons. Logistic regression of landscape variables indicated that wet grassland in 1000-2000m is essential to predict the probability of road kill. Wet grassland is an important breeding and forage habitat for amphibians. It also indicated that mass wet grassland in 1000-2000m is essential for maintain a big amphibian population. 4. There was significant differences among distance from aquatic site of subadults, female and males of R. kukunoris and B. Minshanicus. Possibly, it was because of their dependence on water. There was a significant negative relationship between distance from aquatic site and individuals body mass. Estimates of core habitat that are too large may make it difficult to establish protective regulations. The smallest suitable terrestrial core habitats were defined as the terrestrial habitats used during migration to and from the wetlands, and for foraging by 90% of any life stage (adults, and subadults) in a season. However, even with the same amphibian distribution pattern along the distance from aquatic sites, the radii of smallest suitable terrestrial core habitats will be varied with the fractal parameters of aquatic site.

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In our screening for new antibiotics from bacteria, the streptomycete isolate M097 from Jiaozhou Bay in China was found to produce aloesaponarin II (1a) and 1,6-dihydroxy-8-hydroxymethyl-anthraquinone (2). Similarly, a terrestrial streptomycete GW24/1694 produced 1a and its methyl ether, the new compound 1-hydroxy-6-methoxy-8-methyl-anthraquinone (1b). All structures were derived by spectrochemical analysis and by comparison with reference data. The results showed that the marine streptomycete isolate M097 and the terrestrial streptomycete GW24/1694 could be a promising material for studying the biosynthetic pathway of polyketides.

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The Integrated Environmental Monitoring (IEM) project, part of the Asia-Pacific Environmental Innovation Strategy (APEIS) project, developed an integrated environmental monitoring system that can be used to detect, monitor, and assess environmental disasters, degradation, and their impacts in the Asia-Pacific region. The system primarily employs data from the moderate resolution imaging spectrometer (MODIS) sensor on the Earth Observation System- (EOS-) Terra/Aqua satellite,as well as those from ground observations at five sites in different ecological systems in China. From the preliminary data analysis on both annual and daily variations of water, heat and CO2 fluxes, we can confirm that this system basically has been working well. The results show that both latent flux and CO2 flux are much greater in the crop field than those in the grassland and the saline desert, whereas the sensible heat flux shows the opposite trend. Different data products from MODIS have very different correspondence, e.g. MODIS-derived land surface temperature has a close correlation with measured ones, but LAI and NPP are quite different from ground measurements, which suggests that the algorithms used to process MODIS data need to be revised by using the local dataset. We are now using the APEIS-FLUX data to develop an integrated model, which can simulate the regional water,heat, and carbon fluxes. Finally, we are expected to use this model to develop more precise high-order MODIS products in Asia-Pacific region.