Transition to turbulence in the floating half zone convection

The transition process to turbulence is studied experimentally in thermocapillary convection of floating half zone. The onset of temperature oscillations in the liquid bridge of floating half zone and further transitions of the temporal convective behaviour are detected by temperature measurements in the liquid bridge. The fast Fourier transform (FFT) reveals the frequency and amplitude characteristics of the flow transition. The experimental results indicate the existence of a sequence of period-doubling bifurcations that culminates in turbulence. The measured Feigenbaum numbers are δ2 = 4.69 and δ4 = 4.6. Both results can be compared with the theoretical asymptotic value δ = 4.669

Aspect-ratio dependent oscillatory thermocapillary convection in the floating half zone

The dependency of the critical Marangoni number on the geometrical aspect ratio of the floating half zone is essential to predict the onset of oscillatory thermocapillary convection. The experimental studies in the microgravity conditions on floating half zones of several centimeters in diameter have predicted that the critical Marangoni number increases with the increasing aspect ratio, and the terrestrial experimental studies have predicted the contradictory conclusion for floating half zones of several millimeters in diameter. In the present work, terrestrial experimental studies were conducted on the floating half zones of 5 Centistokes (cSt) silicon oil and 10 cSt silicon oil. The experimental results show that the critical Marangoni number generally increases with the increasing aspect ratio of the floating half zone and then decreases. Moreover, a further increase of the critical Marangoni number with the increasing aspect ratio occurs for the slender floating half zones

N-(2-羟基乙基)芥酰胺对高脂血症金黄地鼠的降脂及保肝作用

高脂血症是诱发心血管疾病的主要危险因素之一,控制血脂的升高对于预防心血管疾病具有十分重要的意义。对于多数患者来说,单纯通过改善饮食结构来严格控制血脂水平是比较困难的,通常需要借助药物进行治疗。目前临床上广泛使用的降血脂药物主要包括HMG-COA还原酶抑制剂、贝特类等。研究表明,过氧化物酶体增殖激活受体α(PPARα)激动剂具有调血脂功能,其合成配体贝特类已成为治疗高脂血症的一线药物,但长期应用易引起肝

利用PIV方法测量半浮区液桥热毛细对流的速度场

本文利用PIV法对硅油液桥热毛细对流的定常的速度场进行了实时测量。为了便于测量,液桥上桥端面采取了铜环中嵌透明材料的方法,从液桥的顶部进行观测。当液桥上下桥有温差时,热毛细对流出现;本实验对于不同上下桥的温差,对液桥横剖面内的速度场分别进行了测量,研究外加温差对于流场速度分布的影响;并且在液桥中取了几个典型横截面进行测量,以期对大Pr数液桥的定常速度场有比较全面的定量的量测。此外,实验结果也可做为数值模拟计算结果的验证

The measurement of velocity field for thermocapillary convection in liquid bridge of floating half zone by PIV

利用PIV法对硅油液桥热毛细对流的定常速度场进行了实时测量。为了便于测量，液桥上桥端面采取了铜环中嵌透明材料的方法，从液桥的顶部进行观测。当液桥上下桥有温差时，热毛细对流出现；本实验对于不同上下桥的温差，对液桥横剖面内的速度场分别进行了测量，研究外加温差对于流场速度分布的影响；并且在液桥中取了几个典型横截面进行测量，以期对大Pr数液桥的定常速度场有比较全面的定量测量。此外，实验结果也可作为数值模拟计算结果的验证

A study on flow patterns of oscillatory thermocapillary convection in floating half zone by PIV

The velocity fields of oscillatory convection have been measured using the techniques of Particle Image Velocimetry (PIV) in a liquid bridge of half floating zone with small typical scales of a few millimeters for emphasizing the thermocapillary effect in comparison with the effect of buoyancy. The flow patterns of the oscillatory flow have been studied experimentally in a liquid bridge. The flow patterns in the liquid bridge are classified with mode numbers according to oscillatory flow characteristics. Results of the experiment show that the mode depends on the aspect ratio as well as the volume ratio of the liquid bridge. The experimental results are helpful for studying the structure of flow at the onset of oscillatory thermocapillary convection in a liquid bridge

半浮区液桥热毛细振荡流

采用非定常、三维直接数值模拟方法研究大Pr半浮区液桥热毛细对流从定常流向振荡流的过渡过程。文中详细描述了热毛细振荡流的起振和振荡特征，给出了液桥横截面上振荡流的流场和温度分布

思想政治教育前沿性问题的探析———基于主体性向主体间性转向的研讨

主体间性思想政治教育作为思想政治教育的前沿性问题之一，是现代哲学在思想政治教育中的具体运用，是解决当前思想政治教育中存在的问题和局限性的新途径。对思想政治教育主体性向主体间性转向的深入研讨，将有助于增强思想政治课程教育的实效性，有助于思想政治教育学科的科学化和现代化。</jats:p

流体力学半径对估算胶体微球聚集速率常数的影响

胶体粒子聚集速率常数实验值远低于理论值一直是被普遍关注的问题.聚集速率常数的理论推导是基于粒子的几何半径来考虑的,但决定粒子扩散速率及聚集速率的应该是粒子的流体力学半径（大于几何半径）,因而它是使聚集速率常数实验值低于理论值的因素之一.影响流体力学半径的因素很多,其中,带电粒子在溶液中因表面存在双电层,会明显增大流体力学半径,造成聚集速率减慢.而双电层的厚度又随溶液中离子强度的不同而改变.本工作在聚集速率的公式中引入了修正因子,即几何半径与其流体力学半径之比,以修正由于用几何半径代替流体力学半径带来的误差.其中几何半径和流体力学半径可以分别用扫描电镜（SEM）和动态光散射（DLS）来测定.以两种粒径的聚苯乙烯带电微球为例,考察了在不同离子强度下,该误差的大小.结果发现,对于半径为30 nm的微球,用流体力学半径计算的慢聚集速率常数比理论值偏低约8%.该误差随离子强度增加而减少.对于快聚集情况,流体力学半径对聚集速率基本没有影响

一种用于长工作距干涉显微镜的棱镜驱动装置

本实用新型公开了一种用于驱动长工作距干涉显微镜的棱镜驱动装置，包括：显微镜支架、高精度步进电机和支座，渥拉斯顿棱镜固定在该支座上，该支座可滑动安装在所述显微镜支架上，所述高精度步进电机设置在所述支座旁边，所述支座通过所述高精度步进电机可沿水平方向左右移动。本实用新型通过采用高精度步进电机驱动渥拉斯顿棱镜在水平方向左右移动，因此可以精确地调节干涉图像的成像效果，使干涉图达到最佳状态