共查询到20条相似文献,搜索用时 140 毫秒
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科学家Boycott发现草酸化或去纤维化血球沉降在倾斜容器中比在垂直容器中更快,这就是所谓的Boycott效应.本文衍生探究不溶固体颗粒在装有蒸馏水倾斜容器中的沉降是否也会产生Boycott效应以及相关参数影响.利用PNK理论推导出颗粒沉降速率关系式,研究其中影响体系的3个变量,分别为竖直沉降速率、容器底部直径、容器倾斜角度.同时,通过实验探究改变单一变量对沉降速率的影响,与理论计算结果基本吻合.结果表明,不溶固体颗粒也会产生Boycott效应;随着容器倾斜角度增大,颗粒在其中沉降速率先加快后减慢;随着容器底部直径增大,沉降速率与之正相关;随着颗粒垂直沉降速率增大,倾斜沉降速率也与之呈正相关. 相似文献
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随着深度的增加竖直圆筒容器中的颗粒物质会把自己的重量逐渐转移到容器的侧墙壁上,使容器底部的压力出现不随筒中颗粒材料高度的增加而增加的饱和现象.但值得注意的是,圆筒中的颗粒柱体并不总是表现为这个称为粮仓效应的力学状态.例如当改变侧墙壁的力学环境使其无法承担颗粒的重量时,柱底部的压力显然将随其高度的增加而线性地增加.本文分析讨论了Janssen模型假设对这类处于静力平衡下,但违反粮仓效应的颗粒系统的行为预测.
关键词:
颗粒物质
粮仓
静摩擦
应力 相似文献
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实验研究了竖直振动情况下,窄容器中颗粒的运动模式.发现运动模式与颗粒床厚度及振动加速度有很强的依赖关系.实验表明横向尺寸较小的容器可以抑制对流卷及拱起现象.对于足够厚的颗粒床,即使振动加速度很大,颗粒床下部仍然存在着颗粒聚集态.出现聚集态时,颗粒床对容器底的冲击力是倍周期分岔的.实验表明倍周期分岔点与颗粒床厚度无关.对于较薄的颗粒床,颗粒可以是聚集态或对流卷,视颗粒尺寸而定.如果使用尺寸分布非常窄的球形颗粒,可以观察到颗粒的有序排列.出现同心的圆筒形“壳”结构,每个“壳”上的颗粒是二维六角密排列的.
关键词:
颗粒物质
倍周期分岔
颗粒聚集态
球堆积 相似文献
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为了便于从理论上探究粮仓效应产生的机理,处理筒仓中颗粒介质的应力分布等问题,将二维颗粒堆积简化为格点系统,并且以随机堆积为物理背景提出了一个由吸收系数p及侧向传递系数q决定的力传递模型.给出了矩阵形式的力传递方程,提出基于二阶差分方程的方法同时求解传递系数矩阵的特征值和特征向量,从理论上导出了一种典型情况下容器底部压力分布与顶部压力分布的关系式.对有效质量随总质量变化关系的理论分析表明,该模型可以给出与Janssen模型类似的结果.对无负载情况下的底部应力分布进行了理论计算,结果表明容器底部中央应力最大,离中央越远应力越小.运用数值计算讨论了p与q对容器底部压力随堆积高度变化曲线的影响. 相似文献
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利用红外光谱鉴别饱和脂肪酸及其盐 总被引:7,自引:0,他引:7
有人认为饱和脂肪酸及其盐是碳酸盐岩中的生烃母质,但将它们从天然沉积物中鉴别出来的方法尚不成熟,对分析评价它们在沉积物中的分布造成困难。文章对几种合成饱和脂肪酸及其盐进行红外光谱测试,获得它们的红外吸收光谱。对特征峰进行指认,分析了饱和脂肪酸及其盐红外光谱的区别。从基团推电子能力、分子折合质量、离子核外电子构型及碳链长度的角度,解释不同饱和脂肪酸以及不同阳离子形成的饱和脂肪酸盐的特征官能团吸收峰波数的变化规律。为地质体中此类物质的鉴别提供参考。 相似文献
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An experimental setup is developed to measure accurately and reproducibly the effective mass as well as its fluctuations at the bottom of the granular columns. It is found that the saturated mass Ms obeys a third power function of the diameter of the silos. The data obtained are in agreement with the modified Janssen model proposed by Vanel and Clement [L. Vanel, E. Clement, Eur. Phys. J. B 11 (1999) 525-533]. 相似文献
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Phonon-like excitations of an anti-instanton-instanton liquid that are due to adiabatic variations in the instanton dimension are considered on the basis of an approximate calculation of the relevant path integral, which is saturated by quasizero modes. The kinetic term and the effective Lagrangian are found for such excitations. The properties of their spectrum, which has a mass gap determined by ΛQCD, are discussed. 相似文献
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Approximate calculation of electronic energy levels of axially symmetric quantum dot and quantum ring by using energy dependent effective mass 下载免费PDF全文
Calculations of electronic structures about the semiconductor
quantum dot and the semiconductor quantum ring are presented in this
paper. To reduce the calculation costs, for the quantum dot and the
quantum ring, their simplified axially symmetric shapes are utilized
in our analysis. The energy dependent effective mass is taken into
account in solving the Schr?dinger equations in the single band
effective mass approximation. The calculated results show that the
energy dependent effective mass should be considered only for
relatively small volume quantum dots or small quantum rings. For
large size quantum materials, both the energy dependent effective
mass and the parabolic effective mass can give the same results. The
energy states and the effective masses of the quantum dot and the
quantum ring as a function of geometric parameters are also
discussed in detail. 相似文献
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Jacques RA dos Santos Freitas L Pérez VF Dariva C de Oliveira AP de Oliveira JV Caramão EB 《Ultrasonics sonochemistry》2007,14(1):6-12
The objective of this work is to discuss the main parameters that influence the sonication extraction of Ilex paraguariensis leaves. For this purpose, the extraction time, solvent polarity, solvent volume, sample mass and particle size were evaluated. Results showed that the main variable affecting the extraction process was the solvent polarity. Though in a less extent, temperature and extraction time also demonstrated to be important parameters, while the other variables did not present a significant influence on the extraction yield. The extracts at the optimized condition were compared with those obtained by maceration, in terms of mass yield and chemical composition. The major compounds identified in the extracts were caffeine and palmitic acid. Some saturated hydrocarbons such as fatty acids, fatty acid methyl esters, phytosterols, and theobromine were also identified in the fractions. 相似文献
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A novel microimaging method is described for measuring the effective diffusion coefficient (D∞) of water in saturated, microporous materials. A simple multicompartment computer simulation was used to show how the value of D∞, when combined with measurements of water proton relaxation times and pulsed field gradient spin-echo amplitudes, allows the pore size distribution and pore connectivity to be characterized. 相似文献
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A. N. Chakravarti K. P. Ghatak K. K. Ghosh S. Ghosh A. Dhar 《Zeitschrift für Physik B Condensed Matter》1982,47(2):149-153
An attempt is made to investigate the effects of size quantization on the effective mass in ultrathin films ofn-Cd3As2. It is found that the effective mass at the Fermi level depends on the size quantum number due to the effect of crystal-field splitting, resulting in different effective masses at the Fermi level corresponding to different electric subbands. It is also observed that the different effective masses closely approach each other, for a given film thickness, with increasing electron concentration and, for a given electron concentration, with increasing film thickness. 相似文献