Structural design of a double-layered porous hydrogel for effective mass transport     

Hyejeong Kim  Hyeon Jeong Kim  Hyung Kyu Huh  Hyung Ju Hwang  Sang Joon Lee 《Biomicrofluidics》2015,9(2)

Mass transport in porous materials is universal in nature, and its worth attracts great attention in many engineering applications. Plant leaves, which work as natural hydraulic pumps for water uptake, have evolved to have the morphological structure for fast water transport to compensate large water loss by leaf transpiration. In this study, we tried to deduce the advantageous structural features of plant leaves for practical applications. Inspired by the tissue organization of the hydraulic pathways in plant leaves, analogous double-layered porous models were fabricated using agarose hydrogel. Solute transport through the hydrogel models with different thickness ratios of the two layers was experimentally observed. In addition, numerical simulation and theoretical analysis were carried out with varying porosity and thickness ratio to investigate the effect of structural factors on mass transport ability. A simple parametric study was also conducted to examine unveiled relations between structural factors. As a result, the porosity and thickness ratio of the two layers are found to govern the mass transport ability in double-layered porous materials. The hydrogel models with widely dispersed pores at a fixed porosity, i.e., close to a homogeneously porous structure, are mostly turned out to exhibit fast mass transport. The present results would provide a new framework for fundamental design of various porous structures for effective mass transport.  相似文献   

体验取样法在情绪研究中的应用优势     

邓欣媚  丁雪辰  桑标 《华东师范大学学报(教育科学版)》2015,33(1):77-83

情绪研究的难题在于其具有动态变化性、情境依存性和个体差异性三大特征,这亟需研究者在对情绪及其相关变量测查时做特别的考量,而传统的情绪研究方法在这些方面存在欠缺。在这种情况下,体验取样法在情绪研究中具有得天独厚的优势:首先,它可以在一定时间跨度内对情绪事件进行即时、连续、重复地测量,降低了潜在记忆偏差和个人偏好的影响;其次,它把情绪事件置于真实的社会环境中,增强了研究的生态效度;另外,它丰富庞大的数据采集量能够从多水平、多角度、多变量分析个体情绪的整个变化过程。随着情绪研究的不断深入,体验取样法将会得到越来越多的运用。  相似文献   

An unexpected particle oscillation for electrophoresis in viscoelastic fluids through a microchannel constriction     

Xinyu Lu  Saurin Patel  Meng Zhang  Sang Woo Joo  Shizhi Qian  Amod Ogale  Xiangchun Xuan 《Biomicrofluidics》2014,8(2)

Electrophoresis plays an important role in many applications, which, however, has so far been extensively studied in Newtonian fluids only. This work presents the first experimental investigation of particle electrophoresis in viscoelastic polyethylene oxide (PEO) solutions through a microchannel constriction under pure DC electric fields. An oscillatory particle motion is observed in the constriction region, which is distinctly different from the particle behavior in a polymer-free Newtonian fluid. This stream-wise particle oscillation continues until a sufficient number of particles form a chain to pass through the constriction completely. It is speculated that such an unexpected particle oscillating phenomenon is a consequence of the competition between electrokinetic force and viscoelastic force induced in the constriction. The electric field magnitude, particle size, and PEO concentration are all found to positively affect this viscoelasticity-related particle oscillation due to their respective influences on the two forces.  相似文献   

Study for optical manipulation of a surfactant-covered droplet using lattice Boltzmann method     

Se Bin Choi  Sasidhar Kondaraju  Joon Sang Lee 《Biomicrofluidics》2014,8(2)

In this study, we simulated deformation and surfactant distribution on the interface of a surfactant-covered droplet using optical tweezers as an external source. Two optical forces attracted a single droplet from the center to both sides. This resulted in an elliptical shape deformation. The droplet deformation was characterized as the change of the magnitudes of surface tension and optical force. In this process, a non-linear relationship among deformation, surface tension, and optical forces was observed. The change in the local surfactant concentration resulting from the application of optical forces was also analyzed and compared with the concentration of surfactants subjected to an extensional flow. Under the optical force influence, the surfactant molecules were concentrated at the droplet equator, which is totally opposite to the surfactants behavior under extensional flow, where the molecules were concentrated at the poles. Lastly, the quasi-equilibrium surfactant distribution was obtained by combining the effects of the optical forces with the extensional flow. All simulations were executed by the lattice Boltzmann method which is a powerful tool for solving micro-scale problems.  相似文献   

论体育资本运行机制的方向、战略和决策问题     

李彪 《广州体育学院学报》2014,(2):23-26

体育资本运行机制的方向和构想要正确地反映行业运行的客观要求和客观规律,是要通过体育资本市场运作来实现的。体育资本社会经济是自主性经济、社会经济、法制化经济和国际化经济,为此,对体育资本机制发展和提升问题,要有明确的构想,同时还要制定明确目标,体育资本运行战略,并制定与之相适应的决策。  相似文献   

基于转化医学模式下高等中医院校生物化学与分子生物学教学改革刍议     

刘长安  朱洁  黄金玲  蔡标  汪天明 《科教文汇》2014,(1):108-109

转化医学是近几年国际医学健康领域提出的新概念,注重基础研究的成果更快地向临床应用转化。本文针对当前高等中医药教育中存在的问题,探讨将转化医学的理念渗透到包括生物化学与分子生物学在内的医学基础课程中的必要性及可行性,总结了实施的具体方法与对策,以期进一步推动高等中医药教育的合理化发展和优秀高等中医药人才的培养。  相似文献   

江苏成年人体育生活部分情况的调查与分析   总被引：7，自引：1，他引：6  

孙飙  姜文凯  王志光  李利 《南京体育学院学报(社会科学版)》1999,(1)

为进一步了解我省成年人体育锻炼及其相关情况，１９９７年９月至１１月间，大规模地向全省五类成年人群（农民、工人、商业、科技与管理），发放了四万份七个方面问题的“问卷调查表”，最终回收３９１９７个样本量。运用ＳＰＳＳ统计软件，经Ｔ检验和Ｆ检验，各类人群与各年龄段回答的百分率，均具有显著性差异。调查结果为;;锻炼人群年龄的中间冷、两头热的现象十分明显，人们主要是在免费的体育场所、公路和街道上进行长跑、长走和做健身操舞为主的有氧运动，通常锻炼的形式是在业余时间自发进行，每月１０元以下进行小额体育消费人数较多，工作忙无时间锻炼是影响成年人参加锻炼的主要原因。根据调查结果，建议：①加大体育的社会舆论宣传、②加强体育场所（地）的基础建设和法制管理。③重视中青年人群的体育工作的体质状况。④引导群众进行健康投资。⑤加强科学健身的指导工作。  相似文献   

Study of fire-extinguishing performance of portable water-mist fire extinguisher in historical buildings     

Zhou Xiaomeng  Zhou Biao  Jin Xiang 《Journal of Cultural Heritage》2010,11(4):25-397

This paper describes both theoretical and experimental studies on the application of a portable water mist extinguisher in suppressing flammable liquid and wood crib fires. At first, the interaction between water mist and fire plume is studied by analyzing the instantaneous process of fire extinction. And then, the feasibility in extinguishing diesel oil, gasoline and wood crib fires is studied by a series of experiments. Theoretical analysis and experimental results show that the extinguishing mechanisms and process change with the difference of water mist characteristics (such as water flux density, droplet velocity and diameter), and the portable water mist fire extinguisher with appropriate characteristics was able to extinguish Class A and Class B fires. It is a potential fire protection means for historical buildings.  相似文献   

和声学课教学内容、方法的改进     

吴彪 《怀化学院学报》2008,27(12)

针对高校和声学课教学内容、方法普遍存在的问题，从实践和实用的观点出发，提出教学内容的拓展、教学方法的改进，通过改进使和声学课教学内容、方法更加完善，教学质量得以提高。  相似文献   

赵元任和胡适     

桑逢康 《文化交流》2009,(2):24-26

留美学友 1910年7月赵元任和胡适同时在北京报考第二批庚款官费留学美国，赵元任在榜上名列第二，胡适列第五十五名。这一年8月16日，包括胡适和赵元任在内的这一批青年学子共71人，从上海乘轮船赴大洋彼岸的美国。  相似文献