共查询到19条相似文献,搜索用时 156 毫秒
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采用随机四参数法对非均质砂质砾岩孔隙结构进行重构, 基于改进的SC-LBM(Shan-Chen格子玻尔兹曼)模型研究润湿流体在多孔介质中的渗吸行为。结果表明: 初始阶段的界面动力学与孔隙骨架的排列有很大关系, 会形成以基质为主的渗吸界面; 流体流经孔喉部分时, 流动断面瞬间缩小, 导致压力梯度和流动阻力迅速增加, 孔吼压力的存在导致流动断面瞬间缩小, 提高了流动阻力, 说明孔隙半径变化对渗吸速率影响较大; 后期阶段, 润湿流体会形成优势渗吸通道, 降低了波及面积, 大幅度降低了渗吸驱油速率。研究结果有助于理解流体在非均质孔隙中的自发渗吸规律, 对发挥裂缝性致密油藏渗吸驱油作用具有重要意义。 相似文献
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报道了圆芯边孔光纤(CSF)中应力分布和双折射的研究结果。用有限元法建立了求解圆芯边孔光纤横截面应力和双折射的计算模型,分析了圆芯边孔光纤横截面应力和应力双折射的分布形态,给出了详尽的物理解释。计算结果表明圆芯边孔光纤的横截面上出现应力分量的拉应力区和压应力区,应力区在纤芯附近对称分布,且不同应力区中应力双折射取向不同。应力分量和应力双折射在圆芯边孔光纤横截面上积分为零。圆芯边孔光纤的几何双折射随波长增加而增大,短波长处几何双折射为零,模式双折射等于应力双折射,随着波长增加,模式双折射逐渐偏离纤芯中心处应力双折射而靠近几何双折射,到长波长处模式双折射主要是几何双折射。对于不同材料组成和结构尺寸的圆芯边孔光纤,模式双折射的数值在10-5量级,随波长增加模式双折射先减小后增加。 相似文献
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通过衬底材料和外延材料的交替生长方式制备出多层排列的自组装量子点超晶格结构.这些埋置量子点的应力/应变场影响着它们的光电性能、压电性能以及力学稳定性.基于各向异性弹性理论的有限元方法,研究了埋置金字塔形应变自组织Ge/Si半导体量子点的应力/应变分布以及流体静应变和双轴应变分布,并与非埋置量子点的应力/应变分布做了比较,指出了它们之间的异同以及覆盖层对量子点应力/应变分布的影响.
关键词:
量子点
应力分布
应变分布 相似文献
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测井是石油勘探和开发过程中的一项重要技术工作,它的根本任务是确定油井中油、气、水的分布情况.测井的方法是利用各种物理参数对油、气、水的依赖关系制成各种测井仪器.物理学是测井技术的理论基础.从1973年开始,我校物理系原子核物理教研室、理论物理教研室的十几名教师先后到大庆油田参加石油测井的技术协作,持续六、七年之久,完成了几项测井方法的理论与实验研究.原子核物理教研室和大庆油田生产测井研究所共同研制的放射性含水率-密度计还获得了国家发明奖.下面从几年的协作实践谈谈物理人才在工业技术部门的一些作用. 一、促进新技术… 相似文献
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功能梯度泡沫金属因其密度连续变化,在轴向受压时可提供稳定增长的反馈载荷。然而当前研究多局限于其纵向压缩力学响应,考虑到实际应用中可能出现的横向冲击,基于低速冲击实验,考察梯度泡沫铝轴向和横向压缩力学响应的异同,并采用数字图像相关技术和数值模拟方法研究其宏细观压溃机制。结果表明:(1)在力学性能上,相比于纵向压缩加载的梯度泡沫铝,横向压缩加载下具有更高的抗压强度,而平台应力、致密化应变和能量吸收效果低于纵向压缩;(2)在失效变形模式上,纵向压缩变形模式为变形带渐进式压缩,而横向压缩变形模式的变形带则随机出现在试样的各个位置;(3)横向压缩下梯度泡沫铝致密化应变和比吸能的减小是由高孔隙率区的胞孔利用率降低导致的;(4)构建的弹性-塑性硬化-刚性模型能够较准确地描述梯度泡沫铝的纵向压缩力学行为。研究结果可为梯度泡沫金属在爆炸冲击结构防护工程中的设计提供理论参考。 相似文献
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高温超导体具有较高的临界温度、高载流能力和低能耗特性,在电力领域得到了广泛的应用,其在通有承载电流情况下的力学特性得到了广泛的关注.研究了承载电流情形下圆柱状超导结构内的磁通钉扎力学响应.考虑临界电流密度沿径向非均匀分布,基于临界态Bean模型,获得了圆柱状超导结构内的感应磁场及电流的分布规律.结合平面应变方法,给出了结构内磁通钉扎力、应力及磁致伸缩的解析表达式.结果表明:临界电流密度非均匀分布时,超导结构内的应力变化趋势与均匀分布时一致,然而临界电流密度的非均匀分布将导致超导结构内的应力和磁致伸缩的极值增大,并引起结构内局部径向应力大小发生改变以及环向应力分布不连续.本研究表明临界电流密度非均匀性对超导结构力学性能的影响是显著的,可为超导体的设计和实际应用提供参考依据. 相似文献
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基于嵌入式离散裂缝模型, 提出一种可在三维空间中考虑应力状态影响的裂缝动态闭合表征方法。将任意方向裂缝的开度和渗透率考虑为作用在裂缝平面法向有效应力的函数, 同时用裂缝传导率变化表征支撑剂充填的水力压裂缝与被开启的天然裂缝由于油藏开发过程中地层流体压力下降而发生的动态闭合行为。研究表明: 致密油藏开发以缝控储量为主。对压裂水平井进行产能评价时, 裂缝动态闭合会导致产能的部分损失, 其影响不可忽略; 水力压裂缝的支撑剂材料属性及天然裂缝的刚度是其中的主控因素。因此需要增大支撑剂的浓度、粒径大小并改善支撑剂的性质, 在最大程度上降低裂缝闭合对生产的不利影响。 相似文献
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选取2002年11月25日至2010年9月24日的国际原油期货价格和中国大庆原油现货价格作为样本数据,用于研究原油市场中期货价格和现货价格之间的联动变化规律. 将期货与现货价格的联动性关系转换为由{Y,O,N}组成的联动性符号序列,用符号序列映射为联动性的波动状态;该波动状态由5个符号组成的滑动窗来表示,由此构成177种联动性波动模态. 将该模态作为网络节点,模态之间的转换作为边,构建期货与现货价格加权联动性复杂网络. 对联动性复杂网络的点强度、强度分布、加权集聚系数、平均最短路径、介数集中性和小团体性等 相似文献
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NVH and reliability analyses of the engine with different interaction models between the crankshaft and bearing 总被引:1,自引:0,他引:1
Zhenpeng He Wenqin Gong Weisong Xie Junhong Zhang Guichang Zhang Zhenyu Hong 《Applied Acoustics》2016
The precision of the interaction model is very important to predict NVH and the reliability of an internal combustion engine. The interaction model between the crankshaft and the bearing is hard to be established precisely due to its complex interaction relationship and dynamic characteristic. In this paper, the elasto-hydrodynamic lubrication model with cavitation theory is built to couple with multi-body dynamic theory to analyze the noise and reliability of the engine, the results were compared with nonlinear spring model and hydrodynamic lubrication model based on a typical in-line six cylinder engines, such as load carrying capacity of the bearing, velocity level of the engine surface, noise level of engine surface and stress of the crankshaft. The results showed that the vibration, noise and stress prediction difference is due to the exciting of the oil film pressure distribution, rigid and flexible body that is used to build the dynamic model will lead the load capacity of the bearing to be great different. Nonlinear spring model and hydrodynamic lubrication model are precise enough to predict the vibration or noise. The All the analysis will provide the guidance for the engine NVH optimization and structural reliability design. 相似文献
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Crude oil price shocks have led to a fluctuation in commodity prices through the industrial chain and supply–demand relationships, which can substantially influence a country’s economy. In this paper, we propose a transmission model of oil price shocks to Chinese price levels and explore the direct and indirect impacts of crude oil price shocks on various Chinese price indices, combining the Granger causality test, impulse response function, and network analysis method. The empirical data are the Brent, WTI, Dubai, and Daqing spot crude oil prices and eight categories of Chinese price indices from January 2011 to March 2020. We found the following results: (1) Consumer price index (CPI) and the price index for means of agricultural production (MAPPI) cannot be directly impacted by crude oil price fluctuations, while they could be indirectly affected. (2) The duration and degree of the impacts of oil prices on each price index vary, and the export price index (EPI) is the most significantly affected. (3) The proportion of the indirect impact in the total impact of crude oil price shocks ranges from 0.03% to 100.00%. Thus, indirect influence cannot be ignored when analyzing the influence of crude oil price fluctuation on Chinese price level. 相似文献
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A theoretical study of harmonic generation in a short period AlGaN/GaN superlattice induced by a terahertz field 下载免费PDF全文
Based on an improved energy dispersion relation, the
terahertz field induced nonlinear transport of miniband electrons in
a short period AlGaN/GaN superlattice is theoretically studied in
this paper with a semiclassical theory. To a short period
superlattice, it is not precise enough to calculate the energy
dispersion relation by just using the nearest wells in tight binding
method: the next to nearest wells should be considered. The results
show that the electron drift velocity is 30% lower under a dc
field but 10% higher under an ac field than the traditional
simple cosine model obtained from the tight binding method. The
influence of the terahertz field strength and frequency on the
harmonic amplitude, phase and power efficiency is calculated. The
relative power efficiency of the third harmonic reaches the peak
value when the dc field strength equals about three times the
critical field strength and the ac field strength equals about four
times the critical field strength. These results show that the
AlGaN/GaN superlattice is a promising candidate to convert radiation
of frequency ω to radiation of frequency 3ω or even
higher. 相似文献
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The yield stress of our newly developed electrorheological (ER)
fluids consisting of dielectric nano-particles suspended in silicone oil
reaches hundreds of kPa, which is orders of magnitude higher than that of
conventional ones. We found that the polar molecules adsorbed on the
particles play a decisive role in such new ER fluids. To explain this polar
molecule dominated ER (PM-ER) effect a model is proposed based on the
interaction of polar molecule-charge between the particles, where the local
electric field is significantly enhanced and results in the polar molecules
aligning in the direction of the electric field. The model can well explain
the giant ER effect and a near-linear dependence of the yield stress on the
electric field. The main effective factors for achieving high-performance
PM-ER fluids are discussed. The PM-ER fluids with the yield stress higher
than one MPa can be expected. 相似文献