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排序方式: 共有451条查询结果,搜索用时 15 毫秒
291.
292.
GAN Hong WANG Lin CAO YinBai YOU JinJun GAN ZhiGuo QIN ChangHai HE Shan XU Kai 《科学通报(英文版)》2013,58(27):3320-3339
In this study, a multi-dimensional critical regulatory criteria and decision-making mechanism based on the scientific cognition of multi-dimensional attributes and characteristics of the water cycle was proposed. This system was functioned by deeply discriminating the nature-society binary characteristics of the five-dimensional characteristics of the water cycle system of the Haihe River Basin (water resources, economy, society, ecology, and environment) under the influence of high-intensity human activities and hydrological changes and by analyzing the organic interactive relationships between the five dimensions and their overall effect on the water cycle. A GDP calculation model was constructed in this study by adjusting the water environment for water resources, after which five-dimensional normalization objective functions were established for multi-objective analysis to carry out trade-off analysis of multi-dimensional regulatory indexes. In addition, synergetic theory, entropy theory and dissipation structure theory were introduced to construct an evaluation model for multi-dimensional regulatory schemes. A water cycle multi-dimensional critical overall regulatory model system was also established. This system consisted of a multi-objective macroeconomic model (DAMOS), water resource allocation model based on rules (ROWAS), evaluation model for WEDP (EMW) and multi-dimensional regulatory scheme evaluation model (SEAMUR) as the main body. To address the national demands faced by the Haihe River Basin as a result of combinatorial schemes for different hydrological series and water amounts diverted by the south-to-north water diversion project, this study adopted a hierarchy progression method to set up the technologies, investigated multi-dimensional overall regulatory methods, proposed an overall regulation threshold value for the water cycle of the Haihe River Basin, and recommended corresponding five-dimensional regulatory schemes. 相似文献
293.
In this paper, the Au nanoparticles and rare-earth (RE) upconversion nanoparticles (NPs) were respectively synthesized by using polyelectrolyte as the capping agents. Since the synthesized Au NPs and RE NPs had the similar size and surface conditions, Their mixture were employed in a pH sensing application. Benefited from the good spectral overlap between the RE upconversion emission bands and pH-tunable surface plasmon bands of the Au NPs, the pH-induced manipulation of green-to-red emission intensity ratio of the upconversion fluorescence was achieved in the Au-RE mixture. The results demonstrate a rapid ratiometric approach for pH sensing, which is more efficient than traditional sensing methods that depend on single intensity-based responses to analytes. 相似文献
294.
HE Hong XU Baowen 《武汉大学学报:自然科学英文版》2006,11(5):1320-1324
Many high performance database servers are becoming idle with the tax data being integrated to country tax data centers. We make use of the idle servers to set up a provincial tax Grid based on open Grid service architecture (OGSA). We put forward practical methods to integrate databases, to define and create basic modular Grid services and apply agent to manage Grid services. This technical innovation scheme is of a service-oriented architecture (SOA) and succeeds in averting resources waste. Tests proved that it greatly improves the quality of tax services. 相似文献
295.
Janzen V Forkert R Fleming HE Saito Y Waring MT Dombkowski DM Cheng T DePinho RA Sharpless NE Scadden DT 《Nature》2006,443(7110):421-426
Stem-cell ageing is thought to contribute to altered tissue maintenance and repair. Older humans experience increased bone marrow failure and poorer haematologic tolerance of cytotoxic injury. Haematopoietic stem cells (HSCs) in older mice have decreased per-cell repopulating activity, self-renewal and homing abilities, myeloid skewing of differentiation, and increased apoptosis with stress. Here we report that the cyclin-dependent kinase inhibitor p16INK4a, the level of which was previously noted to increase in other cell types with age, accumulates and modulates specific age-associated HSC functions. Notably, in the absence of p16INK4a, HSC repopulating defects and apoptosis were mitigated, improving the stress tolerance of cells and the survival of animals in successive transplants, a stem-cell-autonomous tissue regeneration model. Inhibition of p16INK4a may ameliorate the physiological impact of ageing on stem cells and thereby improve injury repair in aged tissue. 相似文献
296.
粘弹性HTI介质中地震波的传播特征 总被引:1,自引:1,他引:0
为了提高地质勘探的精度,本文主要通过理论推导和数值模型计算研究了粘弹性HTI介质中地震波的传播特征,其参数包括相速度、慢度、偏振向量等,并基于依据传播方向定义的慢度向量和分量定义的慢度向量,通过求解Christoffel方程推导出粘弹性HTI介质中均匀波的相速度、偏振向量、慢度、群速度的精确计算公式,经过对比分析得出:特殊分量法在给定传播方向 的情况下提供了一种更为简单的求取无约束粘弹性各向异性介质中均匀、非均匀波波动参数的方法。采用特殊分量法,推导了粘弹性HTI介质中非均匀波的二维、三维波动参数表达式,并采用数值模型计算,研究了粘弹性HTI介质中非均匀SH波的相速度随非均匀系数D及弹性参数虚部k值的变化规律,结果表明D影响了地震波的相速度大小,但对其方位特性无影响,可见在粘弹性HTI介质中相速度随方位角变化的规律可指明介质的对称轴方向,k值的大小也对相速度的各向异性产生影响,但沿对称轴方向速度大小不变。 相似文献
297.
Cookson WO Ubhi B Lawrence R Abecasis GR Walley AJ Cox HE Coleman R Leaves NI Trembath RC Moffatt MF Harper JI 《Nature genetics》2001,27(4):372-373
We have carried out a genome screen for atopic dermatitis (AD) and have identified linkage to AD on chromosomes 1q21, 17q25 and 20p. These regions correspond closely with known psoriasis loci, as does a previously identified AD locus on chromosome 3q21. The results indicate that AD is influenced by genes with general effects on dermal inflammation and immunity. 相似文献
298.
Honeybee dances communicate distances measured by optic flow 总被引:5,自引:0,他引:5
In honeybees, employed foragers recruit unemployed hive mates to food sources by dances from which a human observer can read the distance and direction of the food source. When foragers collect food in a short, narrow tunnel, they dance as if the food source were much farther away. Dancers gauge distance by retinal image flow on the way to their destination. Their visually driven odometer misreads distance because the close tunnel walls increase optic flow. We examined how hive mates interpret these dances. Here we show that recruited bees search outside in the direction of the tunnel at exaggerated distances and not inside the tunnel where the foragers come from. Thus, dances must convey information about the direction of the food source and the total amount of image motion en route to the food source, but they do not convey information about absolute distances. We also found that perceived distances on various outdoor routes from the same hive could be considerably different. Navigational errors are avoided as recruits and dancers tend to fly in the same direction. Reported racial differences in honeybee dances could have arisen merely from differences in the environments in which these bees flew. 相似文献
299.
300.
Katz HE Lovinger AJ Johnson J Kloc C Siegrist T Li W Lin YY Dodabalapur A 《Nature》2000,404(6777):478-481
Electronic devices based on organic semiconductors offer an attractive alternative to conventional inorganic devices due to potentially lower costs, simpler packaging and compatibility with flexible substrates. As is the case for silicon-based microelectronics, the use of complementary logic elements-requiring n- and p-type semiconductors whose majority charge carriers are electrons and holes, respectively-is expected to be crucial to achieving low-power, high-speed performance. Similarly, the electron-segregating domains of photovoltaic assemblies require both n- and p-type semiconductors. Stable organic p-type semiconductors are known, but practically useful n-type semiconductor materials have proved difficult to develop, reflecting the unfavourable electrochemical properties of known, electron-demanding polymers. Although high electron mobilities have been obtained for organic materials, these values are usually obtained for single crystals at low temperatures, whereas practically useful field-effect transistors (FETs) will have to be made of polycrystalline films that remain functional at room temperature. A few organic n-type semiconductors that can be used in FETs are known, but these suffer from low electron mobility, poor stability in air and/or demanding processing conditions. Here we report a crystallographically engineered naphthalenetetracarboxylic diimide derivative that allows us to fabricate solution-cast n-channel FETs with promising performance at ambient conditions. By integrating our n-channel FETs with solution-deposited p-channel FETs, we are able to produce a complementary inverter circuit whose active layers are deposited entirely from the liquid phase. We expect that other complementary circuit designs can be realized by this approach as well. 相似文献