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21.
科技创新是时代发展的永恒主题 总被引:2,自引:0,他引:2
王勤 《科技情报开发与经济》2004,14(6):192-193
从科技创新的基本特征、类型分析入手,总结介绍了国际科技创新的发展经验与启示,并结合我国国情,提出现阶段我国科技创新的战略框架和基本对策。 相似文献
22.
1 Introduction
Over the past several years, the preparation and characterization ofnanoscale magnetic materials, especially one-dimensional (1D) nanostructure, have attracted much attention as the nanomaterials would allow investigating the fundamental aspects of magnetic-ordering phenomena in magnetic materials with reduced dimensions and could lead to new potential applications such as data storage technology[1-6]. 相似文献
23.
As a newly developed precision technology, casting-forging complex near net forming process is utilized to produce complex components with a short lead time, low cost and high precision, thus to accelerate the response speed of the market and enhance the competitive power of products. In this paper, the casting-forging complex near net forming process of alternator claw pole was developed and investigated with a combination of experimental and numerical simulation method. Qualified near net workpiece was manufactured, mechanical parameter and relative field information during the forming process was also obtained. While the alternator claw-pole is processed with this technology, the forming force is small, the process is short and the quality of forgings is perfect. Therefore, the complex casting-forging near net forming process of claw-pole is an energy and material saving technology, which will have a vast developing and application prospect in the future. 相似文献
24.
Fracture toughness is very important when applying Damage Tolerance Design and Assessment Techniques. The traditional testing approach for obtaining fracture toughness values is costly and time consuming. In order to estimate the fracture toughness of ductile metals, the fracture mechanics theory, materials plastic deformation theory and materials constructive relationships are employed here. A series of formulae and a theoretical approach are presented to calculate fracture toughness values of different materials in the plane stress and plane strain conditions. Compared with test results, evaluated values have a good agreement. 相似文献
25.
Selective functionalization of mesoporous silica nanospheres (MSNs) is crucial for nanoengineering of MSNs.
Herein, we have combined “surface-protected etching strategy” and “cationic surfactant assisted etching
strategy” to prepare functionalized MSNs with externally attached amino groups. The externally attached NH2
groups endow the catalysts with excellent catalytic performance for nitroaldol reaction between nitromethane
and benzaldehyde. In addition, those NH2-MSNs can also be used to support gold nanoparticles, which display
very good catalytic performance for reduction of 4-nitrophenol. It can be envisioned that the synthesis protocol
developed in this work could also be extended to nanoengineered MSNs, which provides opportunities for nanoreactors
design. 相似文献
26.
27.
随着民办高校的发展,民办高校党建工作在逐渐步入正轨的同时面临许多发展难题,其中最核心的是民办高校党组织与董事会的关系问题。从理论来看,二者之间的关系为决策与参与决策、监督与被监督、引导与被引导、分工协作,但在实践中却出现分权不清、失衡、权力运作失范、制度缺失严重、机制运作失调等问题,因此,只有转变观念,准确定位,建立框架科学、细节完备的制度体系,打造良性互动的科学机制,夯实基础、循序渐进才能处理好二者的关系,推进民办高校健康发展。 相似文献
28.
在Borodin和Salminen(2002)文献中有关带漂移布朗运动占位时的Laplace变换结果的基础上,运用Li等(2014)计算局部时的方法,推出了带漂移布朗运动在独立指数时间e_q前,及停留在0处的局部时的Laplace变换表达式Ee~(-λl(e_q,0))=lima→0I(λ/a;0,a,e_q)=((2q+μ~2)~(1/2))/(λ+(2q+μ~2)~(1/2))。当μ=0时,本文结果与标准布朗运动的结果吻合。 相似文献
29.
Resolving early silicate differentiation timescales is crucial for understanding the chemical evolution and thermal histories of terrestrial planets. Planetary-scale magma oceans are thought to have formed during early stages of differentiation, but the longevity of such magma oceans is poorly constrained. In Mars, the absence of vigorous convection and plate tectonics has limited the scale of compositional mixing within its interior, thus preserving the early stages of planetary differentiation. The SNC (Shergotty-Nakhla-Chassigny) meteorites from Mars retain 'memory' of these events. Here we apply the short-lived 146Sm-142Nd and the long-lived 147Sm-143Nd chronometers to a suite of shergottites to unravel the history of early silicate differentiation in Mars. Our data are best explained by progressive crystallization of a magma ocean with a duration of approximately 100 million years after core formation. This prolonged solidification requires the existence of a primitive thick atmosphere on Mars that reduces the cooling rate of the interior. 相似文献
30.