Dynamics of polymer electrolyte fuel cells undergoing load changes

Numerical simulations are carried out for a single-channel polymer electrolyte fuel cell (PEFC) undergoing a step increase in current density. The objective is to elucidate profound interactions between the cell voltage response and water transport dynamics occurring in a low-humidity PEFC where the membrane hydration and hence resistance hinges upon the product water. Detailed results are presented to show that a step increase in the current density leads to anode dryout due to electroosmotic drag, while it takes several seconds for water back-diffusion and anode humidified gas to re-wet the anode side of the polymer membrane. The water redistribution process is controlled by water production, membrane hydration, electroosmotic drag, and water diffusion in the membrane. The anode dryout results in a substantial drop in cell voltage and hence temporary power loss. Under extreme situations such as dry anode feed, large step increase in the current density, and/or lower temperatures, the cell voltage may even reverse, resulting in not only power loss but also cell degradation. Finally, the dynamics of current distribution after a step change in gas humidification is numerically examined.     

聚合物在离子选择电极上的应用

本文概述了聚合物膜离子选择电极的发展,制备、应用等方面的研究情况;将聚合物膜离子选择电极分为固态膜类和液态膜类,分别对其优缺点和发展前景加以分析;并讨论了聚合物在敏感膜中的作用,以及聚合物结构对敏感膜性能的可能影响。     

高分子功能材料及在传感器中的应用一高分子功能材料种类和功能(连载一)

简要介绍了高分子功能材料种类及信息转换功能，并对其导电性、光电性、压电性和热电性进行了论述。     

A review of modeling approaches for oriented semi-crystalline polymers

Modeling changes in the physical properties of oriented semi-crystalline polymer films is beneficial for understanding the fundamentals associated with structure property relationships and could be used for developing new polymer films with significantly enhanced physical properties. Relating the molecular changes observed in oriented polymer films to inherent polymer characteristics provides valuable insight for the development of new polymers which exhibit enhanced physical properties upon orientation. Modeling efforts will be reviewed that have attempted to use fiber composite theory to explain the transitions seen during the orientation process.     

In Vitro hydrodynamic evaluation of prosthetic polymer heart valves in steady flow

Hydrodynamic comparison of two polymer valves with two mechanical valves is presented. The valves were perfused in a steady flow system, and comparisons between the valves were made on the transvalvular pressure distribution and drop, opening area, and leakage volume. Particular emphasis was placed on a slit-type bileaflet polymer valve which was newly designed and fabricated in our research group. The results showed that the functional characteristics of a slit-type bileaflet polymer valve compared favorably with that of mechanical valves. This valve may be a viable and inexpensive alternative, especially for short-term use in TAH or VAD systems.     

Preparation and structure of fluorinated/non-fluorinated polyacrylate gradient emulsion blend film

The emulsion blend method, which is environmentally friendly and energy saving, was used to prepare a compositional gradient film of fluorinated/non-fluorinated polyacrylate in this paper. The size and glass-transition temperature (T_g) of the emulsion particles were designed to enhance the driving force of their selective congregation and promote the formation of gradient structure. The structures and surface properties of the obtained films were characterized. The results showed that when the fluorinated components have much smaller particle size and higher T_g than those of fluorine-free polyacrylate components, the gradient structures formed in the direction across the film thickness of the films. The concentration of the fluorinated component increased gradually from film-glass interface to film-air interface in the blend film, making the surface free energies of the two sides of the gradient film distinctively different.     

聚合物与水气交替联驱提高采收率试验研究

采用三种不同沉积韵律平面模型试验研究水驱后聚合物与水气交替联驱提高原油采收率的驱替特征。结果表明,聚合物与水气交替联驱对正韵律油藏提高采收率效果很好;对反韵律油藏和复合韵律油藏也有不同程度提高采收率效果。通过分析两种不同韵律砂岩油藏水气交替提高采收率矿场试验成功实例,认为聚合物与水气交替联驱法可综合发挥两种方法的优势,在类似油藏中比单一方法有更好的提高采收率效果。     

青西凹陷窟窿山构造青2-50井钻井液技术

青2-50井地层十分复杂,如泥页岩易发生水化坍塌,硬脆性页岩易垮,层理裂缝发育,易漏,地层倾角大,井眼应力不均衡等,因此为保证井壁稳定,需把钻井液配方的优选和适时有效地转化作为钻井施工的重点.在柳沟庄组以上地层,采用了加生石灰的阳离子钻井液,通过保持较高矿化度,满足了地层和工程的需要.在钻至深部地层以后,转化为阳离子聚磺钻井液,提高了原体系的抗温能力,并解决了深井阶段的裂隙封堵、地层垮塌、润滑防卡和油层保护等难题.青2-50井的顺利完钻为提高该区块的钻探开发速度积累了经验,并建议选用复合金属离子(或两性离子)聚合物(防塌)钻井液替代阳离子钻井液.