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991.
Under the special background of China, the cooperative innovation between different government-industry-university-research institutes plays an increasingly important role in the agricultural field. However, the existing literature has paid little attention to it. Considering the cooperation patents, published in the agriculture field stemming from the Full-text Database of China Patents as the study object, the spatial and institutional attribute of the authors as the data source, and by combining the social network and spatial econometrics analysis, this paper analyzes the structure evolution characteristics of cooperative innovation networks of agricultural government-industry-university-research institute in the city level of China in 1985–2014, based on the triple helix theory, with the influence factors discussed. This shows that, 1) since 1985, China's agricultural innovation level has been substantially increased, but the development degree of the cooperative innovation network is low, and the patent cooperation mainly relies on authors in the same unit; 2) enterprises play a leading role in the agricultural cooperative innovation. The effect of the government and hybrid organizations driven by the government is not obvious; 3) the cooperative innovation in the province and city dominates, and a multi-pole pattern has been formed. The cooperative innovation network structure evolves from a single helix empty core and double helix multi core to a double helix hierarchical network; 4) the city's science, education funding and personnel investment are key factors determining the agricultural cooperative innovation, while the agricultural development of the city presents slight negative impacts on it. The spatial mismatch of supply and demand is present in the technical cooperative innovation of China's agriculture. Therefore, the science enhancement and education investment to big agricultural provinces should be promptly implemented. 相似文献
992.
Understanding streamflow changes in terms of trends and periodicities and relevant causes is the first step into scientific management of water resources in a changing environment. In this study, monthly streamflow variations were analyzed using Modified Mann-Kendall(MM-K) trend test and Continuous Wavelet Transform(CWT) methods at 9 hydrological stations in the Huaihe River Basin. It was found that: 1) streamflow mainly occurs during May to September, accounting for 70.4% of the annual total streamflowamount with Cv values between 0.16–0.85 and extremum ratio values between 1.70–23.90; 2) decreased streamflow can be observed in the Huaihe River Basin and significant decreased streamflow can be detected during April and May, which should be the results of precipitation change and increased irrigation demand; 3) significant periods of 2–4 yr were detected during the 1960 s, the 1980 s and the 2000 s. Different periods were found at stations concentrated within certain regions implying periods of streamflow were caused by different influencing factors for specific regions; 4) Pacific Decadal Oscillation(PDO) has the most significant impacts on monthly streamflow mainly during June. Besides, Southern Oscillation Index(SOI), North Atlantic Oscillation(NAO) and the Ni?o3.4 Sea Surface Temperature(Ni?o3.4) have impacts on monthly streamflow with three months lags, and was less significant in time lag of six months. Identification of critical climatic factors having impacts on streamflow changes can help to predict monthly streamflow changes using climatic factors as explanatory variables. These findings were well corroborated by results concerning impacts of El Nino-Southern Oscillation(ENSO) regimes on precipitation events across the Huaihe River Basin. The results of this study can provide theoretical background for basin-scale management of water resources and agricultural irrigation. 相似文献
993.
ZnO压敏陶瓷冲击老化的电子陷阱过程研究 总被引：1，自引：0，他引：1
使用8/20 μs脉冲电流发生器对普通商用ZnO陶瓷压敏电阻片进行了最多5000次的冲击试验.测量了冲击前后试样的电气性能和介电特性,分析了冲击后小电流区的U-I特性和损耗角正切值tanδ随脉冲大电流的不断作用而发生的变化.实验发现压敏电压U1mA随冲击次数的增加经历增大—稳定—减小三个过程.认为正反偏Schottky势垒的中性费米能级的变化是影响样品小电流区的最根本原因.本文提出用试样的非线性系数α作为老化特征参数比传统的U 相似文献
994.
995.
利用Monte Carlo (MC)模拟技术研究了非均一的吸附原子与基底相互作用能在一定的生长条件下对超薄膜生长过程的影响.非均一相互作用能是由基底表面原子在垂直和水平方向上实际位置与理想晶格原子位置的偏差所造成.本文用高斯分布来表示这种非均一相互作用能.模拟结果表明:非均一相互作用能对超薄膜的生长过程及薄膜的形貌有显著的影响.这种影响同时受到生长条件的限制,在中等温度时相互作用能的非均一性对岛的个数、平均大小的影响最显著;温度的增加在一定程度上可抵御相互作用能的非均一性对薄膜生长的影响. 相似文献
996.
997.
Using a double resonant KTiOPO4 (KTP) intracavity optical parametric oscillator operating at degenerated point of 2 μm, we demonstrate a unique mid-infrared source based on difference frequency generation in GaSe crystal. The output tuning range is 8.42-19.52 μm, and a peak power of 834 W for type-I phase matching scheme and 730 W for type-II phase matching scheme are achieved. Experimental results show that this oscillator is a good alternative to the generator of a compact and tabletop mid-infrared radiation with a widely tunable range. 相似文献
998.
Jian Cao Zhijun Jin Wenxuan Hu Yijie Zhang Suping Yao Xulong Wang Yueqian Zhang Yong Tang 《Marine and Petroleum Geology》2010
Calcite veins and cements occur widely in Carboniferous and Permian reservoirs of the Hongche fault zone, northwestern Junggar Basin in northwest China. The calcites were investigated by fluid inclusion and trace-element analyses, providing an improved understanding of the petroleum migration history. It is indicated that the Hongche fault behaved as a migration pathway before the Early Cretaceous, allowing two oil charges to migrate into the hanging-wall, fault-core and footwall reservoirs across the fault. Since the Late Cretaceous, the Hongche fault has been sealed. As a consequence, meteoric water flowed down only into the hanging-wall and fault-core reservoirs. The meteoric-water incursion is likely an important cause for degradation of reservoir oils. In contrast, the footwall reservoirs received gas charge (the third hydrocarbon event) following the Late Cretaceous. This helps explain the distribution of petroleum across the fault. This study provides an example of how a fault may evolve as pathway and seal over time, and how reservoir diagenetic minerals can provide clues to complex petroleum migration histories. 相似文献
999.
We conducted studies of phytoplankton and hydrological variables in a semi-enclosed bay in northern China to understand the spatial–temporal variability and relationship between these variables. Samples were collected during seven cruises in Jiaozhou Bay from November 2003 to October 2004, and were analyzed for temperature, nutrients and phytoplankton pigments. Pigments from eight possible phytoplankton classes (Diatoms, Dinoflagellates, Chlorophyceae, Prasinophyceae, Chrysophyceae, Haptophyceae, Cryptophyceae and Caynophyceae) were detected in surface water by high performance liquid chromatography (HPLC). Phytoplankton pigment and nutrient concentrations in Jiaozhou Bay were spatially and temporally variable, and most of them were highest in the northern and eastern parts of the sampling regions in spring (May) and summer (August), close to areas of shellfish culturing, river estuaries, dense population and high industrialization, reflecting human activities. Chlorophyll a was recorded in all samples, with an annual mean concentration of 1.892 μg L−1, and fucoxanthin was the most abundant accessory pigment, with a mean concentration of 0.791 μg L−1. The highest concentrations of chlorophyll a (15.299 μg L−1) and fucoxanthin (9.417 μg L−1) were observed in May 2004 at the station close to the Qingdao Xiaogang Ferry, indicating a spring bloom of Diatoms in this area. Although chlorophyll a and other biomarker pigments showed significant correlations, none of them showed strong correlations with temperature and nutrients, suggesting an apparent de-coupling between the pigments and these hydrological variables. The nutrient composition and phytoplankton community composition of Jiaozhou Bay have changed significantly in the past several decades, reflecting the increasing nutrient concentrations and decline of phytoplankton cell abundance. The unchanged total chlorophyll a levels indicated that smaller species have filled the niche vacated by the larger species in Jiaozhou Bay, as revealed by our biomarker pigment analysis. 相似文献
1000.
海洋青鳉鱼专用型基因芯片的设计及其在生态毒理学上的应用研究 总被引：3，自引：0，他引：3
以生物芯片技术为核心,结合生态毒理学与功能基因组学的方法,制备了海洋青鳉鱼专用型生物芯片,包含180个与细胞分裂、解毒反应、缺氧反应、氧化应激反应、凋亡、生长和发育、性别决定和性腺分化以及生殖激素分泌等功能相关的基因.我们提取了雌性海洋青鳉鱼成体在正常培养和缺氧处理12周后的肝脏和卵巢组织总RNA,利用自制的基因芯片进行了基因表达谱分析,结果显示海洋青鳉鱼在缺氧压力环境下,肝脏和卵巢组织的差异性表达基因分别检测出9个和6个,表明应用此类自制良好的芯片可有效获得海洋青鳉鱼的组织特异性基因表达图谱,也将加强对海洋缺氧状态、氧化应激等反应的分子生物学机制的理解.本研究对于识别异常环境状态下的基因表达模式和组织特异性标志物,进一步开展监测海洋生态毒理因素的研究奠定良好的基础. 相似文献