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Search Results: 1 - 10 of 125219 matches for " 杨大勇 "
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英国工业革命融资及对中国经济建设的启示
Financing of Great Britain′s Industrial Revolution and Its Inspirations on Economic Construction in China

大勇
- , 2016, DOI: 10.15896/j.xjtuskxb.201604003
Abstract: 英国通过工业革命成为世界第一个工业化国家,与大规模资本投入紧密相关。私人资本市场和银行贷款市场为制造业提供了资本,运河、铁路等行业主要获得公共资本市场的支持,地方资本市场与贷款市场对工业革命的支持十分显著,工业革命融资呈现区域化特点。这一时期,政府的政策导向从“重商主义”向“自由经济理论”转变,为工业革命的顺利推进创造了条件。英国工业革命融资为中国当前经济建设提供了三点启示:一是要大力发展区域资本市场;二是要继续发展地方中小银行等金融机构;三是要继续理顺和优化政府与市场的关系。
Britain became the first industrialized country across the world after Industrial Revolution, which was closely related to large scale of capital inputs. More specifically, private capital market and bank credit market provided capital for manufacturing industry, and the canal and railway industries were funded by public capital market. The Industrial Revolution was significantly supported by local capital market and credit market, and its financing was regionalized. During this time, government policies have transferred from commerce-oriented to free economy theory, which helped to the advancement of Industrial Revolution. The inspirations that current economic construction in our country can draw from Great Britain′s Industrial Revolution are concluded as follows. First, regional capital market should be actively supported. Second, financial institutions such as local medium-sized and small banks should be further developed. Third, the relationship between government and market should be further rationalized and optimized
粗糙表面微通道电渗流的数值模拟
大勇,刘莹
化工学报 , 2008,
Abstract: 电渗流(EOF)广泛应用于微流控芯片中的流体的传输与混合。针对带有粗糙表面的平行板微通道,建立了描述EOF的控制方程,基于有限元分析方法对具有不同粗糙度和EDL厚度的微通道内的EOF进行了数值模拟。结果表明,当EDL厚度接近0.3倍粗糙度大小时,粗糙度对EDL的影响较大,EOF受到粗糙度的阻力作用较为明显,而当EDL厚度相对粗糙度较大和较小时,EOF速度受到粗糙度的影响相对较小;粗糙表面微通道中部EOF速度与相对EDL厚度的关系呈“V”型曲线,EOF平均速度呈“L”型曲线。研究结论对于微通道表面的优化设计以及微流控芯片中流体的精确操控具有一定的参考意义。
基于最小耗能原理的岩块损伤演变研究
大勇, 高玮
金属矿山 , 2008,
Abstract: 以岩块的各向同性弹性损伤为例,提出了一种基于最小耗能原理建立损伤演变方程的新思路,并推导得到了岩块在单向压缩下的损伤演变方程及临界损伤值。
磁控溅射微晶和非晶不锈钢薄膜的耐点蚀性能
大勇,德钧
腐蚀科学与防护技术 , 1991,
Abstract: 用磁控溅射法获得微晶和非晶不锈钢薄膜,考察了它们的耐点蚀性能,并用X-射线和电子衍射分析了薄臆的结构。结果表明,薄膜的抗点蚀能力远优于普通321不锈钢;当晶粒尺寸小于7.7nm时,微晶态不锈钢薄膜的点蚀电位高于非晶态薄膜。
磁控溅射微晶和非晶不锈钢薄膜的耐点蚀性能
大勇,德钧
腐蚀科学与防护技术 , 1991,
Abstract: 用磁控溅射法获得微晶和非晶不锈钢薄膜,考察了它们的耐点蚀性能,并用X-射线和电子衍射分析了薄臆的结构。结果表明,薄膜的抗点蚀能力远优于普通321不锈钢;当晶粒尺寸小于7.7nm时,微晶态不锈钢薄膜的点蚀电位高于非晶态薄膜。
非牛顿幂律流体电渗微混合的数值模拟
大勇,徐涛,李鸣
科学通报 , 2015, DOI: 10.1360/N972015-00088
Abstract: 微混合是芯片实验室中实现快速反应、分析和检测的一个重要前提.为了研究非牛顿幂律流体的微混合特性,应用有限元法对壁面存在异构zeta电势的平板微通道内流动进行了数值模拟.研究结果表明,幂律流体表观黏度的差异对动电现象具有不同的效果,对混合效率有显著的影响.流体的剪切变稀特性有增强动电现象的趋势,剪切变稠特性则相反.当流体幂律指数减小时,可以获得更好的混合效果.相对牛顿流体和膨胀性流体而言,假塑性流体采用电渗微混合具有更高的效率和实用性.通过对外加电场和zeta电势的调控可以改善混合性能,假塑性流体比牛顿流体和膨胀性流体对参数更敏感.
松嫩草地植物群落物种多度–分布关系及其解释
大勇,允菲*
生物多样性 , 2014,
Abstract: ?物种多度–分布关系是生物多样性科学的关键问题之一,但目前对其解释尚未有统一的观点,生态幅假说和集合种群动态理论是其中两个有代表性的假说。作者以松嫩平原羊草(leymuschinensis)草甸的代表性群落羊草–杂类草群落斑块为研究对象,分别于2007年和2008年调查了其植物生长型组成和斑块距离,来检验上述两个假说对物种多度–分布关系的解释能力。作者提出以生长型适应指数(growth-formadaptionindex,gai)作为生态幅的衡量指标,以最小斑块距离来反映植物的扩散和定居过程。结果表明:在生境尺度上,物种的多度和分布成显著正相关,且多度–分布关系在年际间相对稳定。物种的多度和分布均与植物生长型密切相关,分布广、多度高的物种以根茎型、直立型或分枝型为主,分布窄、多度低的物种以莲座型或刷状根型为主。gai与物种的多度和分布均成显著线性正相关,少数物种的分布广,多数物种的分布窄,直接支持了生态幅假说。最近斑块距离与物种的多度和分布均成显著幂函数负相关,而群落相似性与斑块距离无显著相关性,因此本结果并未直接支持集合种群动态理论,但扩散过程可能是影响羊草草甸植物群落种多度–分布关系的重要潜在机制之一。
直微通道中的电黏性效应
Electroviscous Effects of Power-law Fluids in Microchannels

罗艳,李鸣,大勇
- , 2017,
Abstract: 为了研究直微通道中幂律流体的电黏性效应,建立了压力驱动微通道内流体流动的数学模型,其中双电层电势分布、流体流动及流动粒子输运特性分别由Poisson-Boltzmann(P-B)方程、Navier-Stokes(N-S)方程及Nernst-Plank(N-P)方程描述。讨论了微通道中有电黏性效应时溶液浓度;幂律指数对微通道内流体的速度分布、流动电场强度的影响。结果表明:对于n<1的剪切变稀流体,流体的黏度和流动速度随着n的增大而减小,变化非常明显;而对于n>1的剪切变稠流体,黏度和流动速度几乎不受n的影响,在实际应用中可以忽略不计。
This paper aims to investigate the power-law fluid flow in microchannel with eletrokinetic effects. In the entire analysis, the electric double layer (EDL) potential is described by the Poisson equation. The flow and transport of the power-law fluid is characterized by the Navier-Stokes equation and the Nernst-Plank equation. Numerical simulation is carried out for all values of the flow behavior index from 0.4 to 1.2. The effects of the flow behavior index, ionic concentration and channel dimension on fluid velocity distribution, streaming potential and apparent viscosity are discussed. The results show that the eletroviscous effect on the flow depends significantly on the flow behavior index. For the shear thinning fluid of the flow behavior index n<1, the fluid viscosity and velocity increase with the value of n increase. For the shear thickening fluid of n>1, the influence of the flow behavior index on the velocity and streaming potential can be neglected in practical application
PNP模型的正弦粗糙微通道幂律流体电渗流研究
Investigating Effects of Sinusoidal Surface Roughness on Power-law Fluid Electroosmotic Flow in Microchannels using PNP Model

肖水云,李鸣,大勇
- , 2017,
Abstract: 针对正弦表面粗糙元对微通道内幂律流体电渗流(EOF)流动特性的影响,建立了二维平板粗糙微通道内幂律流体EOF的Poisson-Nernst-Planck(PNP)数学模型,采用有限元法耦合求解双电层(EDL)电势的Poisson方程、离子输运的Nernst-Planck方程、幂律流体流动的Cauchy动量方程以及本构方程。在对PNP模型验证之后,研究了正弦粗糙元高度、频率对幂律流体壁面EDL电势分布以及EOF流量的影响。模拟结果表明:正弦粗糙元对近壁面EDL电势、外加电场电势、EOF速度矢量分布有较大影响;粗糙元波谷处EDL电势随着粗糙元相对高度或频率的增加而增大,波峰处反之;幂律流体EOF流量随着粗糙元相对高度的增加而单调减小,随粗糙元频率的增加先减小后增大,且在粗糙元频率为2.2时EOF流量最小;特别地,流体幂律指数越小,其受粗糙元高度或频率的影响越大。
To investigate the effects of sinusoidal surface roughness on power-law fluids electroosmotic flow (EOF) flow characteristics in microchannels, the Poisson-Nernst-Planck (PNP) mathematical model of power-law fluid EOF in two-dimensional parallel-plate rough microchannels was established. The Poisson equation for electric double layers (EDL) potential, the Nernst-Planck equation for the ion concentration, the Cauchy momentum equation and the constitutive equation for flows of power-law fluid electrolyte solution were solved using the finite element method. After the PNP model of power-law fluid EOF is verified, the effects of sinusoidal surface roughness relative height and frequency on the EDL potential and EOF flow of power-law fluid were investigated. The computer simulation results show that the sinusoidal surface roughness greatly affects the distribution of externally applied electric potential, the EDL potential and velocity vectors of EOF near the roughness surface. The EDL potential at the wave trough area increases with the roughness relative height and frequency, while an opposite trend occurs at the wave crest region. The flow of power-law fluid decreases with the increase of the roughness relative height only, but with the increase of the roughness frequency, it first decreases to the lowest value, where the roughness frequency equals to 2.2 and then increases. Particularly, with the decrease of power-law index, the effects of sinusoidal surface roughness on the fluid increase
若尔盖高原退化沼泽群落植物多样性及种间相关性沿排水梯度的变化
大勇, 永兴,
植物生态学报 植物生态学报 , 2012, DOI: 10.3724/SP.J.1258.2012.00411
Abstract: ?植物多样性与种间相关性是植物群落生态学和生物多样性研究的核心问题,然而有关二者之间关系的综合研究尚不多见。该文以若尔盖高原排水干扰下不同退化阶段的沼泽湿地植被为研究对象,应用Spearman秩相关、回归分析等方法,分析了沼泽植物群落物种多样性和种间相关性的变化及二者相互关系。结果表明:沿排水梯度,从相对原生沼泽至极度退化沼泽,不同植物种群均有其特定的生态分布范围;群落总种数、样方物种丰富度、Shannon-Wiener指数和Whittaker指数均单调增加;植物种间相关强度增加;正相关种对比例呈逐渐增加的趋势,以极重度和极度退化阶段的较高,相对原生沼泽和轻度退化阶段的较低,负相关种对比例的变化趋势与之相反;Shannon-Wiener指数与正负相关种对比例均具有显著线性关系(p<0.05),Whittaker指数均无显著关系(p>0.05)。人为排水作用通过提高群落生境异质性,促进正相关种对的共存,增加沼泽群落植物多样性。
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