Proton exchange membrane (PEM) fuel cell stack requires gaskets and seals in each cell to keep the reactant gases within their respective regions. Gasket performance is integral to the successful long-term operation of a fuel cell stack. This review focuses on properties, performance and degradation mechanisms of the different polymer gasket materials used in PEM fuel cell under normal operating conditions. The different degradation mechanisms and their corresponding representative mitigation strategies are also presented here. Summary of various properties of elastomers and their advantages and disadvantages in fuel cell'environment are presented. By considering the level of chemical degradation, mechanical properties and cost effectiveness, it can be proposed that EPDM is one of the best choices for gasket material in PEM fuel cell. Finally, the challenges that remain in using rubber component as in PEM fuel cell, as well as the prospects for exploiting them in the future are discussed.
Dielectric elastomers (DEs) have been suggested as generators to harvest electrical energy from natural mechanical energy sources, such as human movements and ocean waves. In this study, a donut-shaped DE generator (DEG) has been fabricated and its performance is characterized depending on the stretch deformation. A simple new stretchable electrode system using multi-walled carbon nanotubes has been suggested. Measurements on the resistance, capacitance, and electrical power generation are made depending on the area expansion. The capacitance and harvested energy are parabolically increased with increased area expansions. The theoretical prediction of energy harvesting is in good agreement with measured values of capacitance changes with stretching. FE analysis is also applied for calculation of strains for the DEG to figure out the distribution of strains. It is suggested that the DEG has promising applications in the field of designing an energy harvesting device depending on the type of energy available. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40076.
We report an adaptive-focus lens using two immiscible liquids. The two liquids have a spherical interface and their border is confined by an iris diaphragm (ID). Using a bubble actuator to vary the aperture of the ID, the surface profile of the two liquid is changed, which in turn leads to a tunable focal length. In this paper, the liquid lens structure is depicted and the operation mechanism of the bubble actuator is introduced. For the liquid lens, the refractive index (n 1 ) of the convex liquid is smaller than that of the concave (or surrounded) liquid (n 2 , n 2 -n 1 ∼ 0.2), so the lens is a diverging lens. As the aperture of the diaphragm is changed from ∼5 to ∼7.5 mm by the actuator, the focal length (f) of the lens could be tuned in the range of -168 mm ≤ f ≤ -55 mm. For the bubble actuator, it has the advantages of voltage control, large actuation pressure, reasonable speed, and low power consumption. Driven by the bubble actuator, our liquid lens can present a large aperture change, reasonable dynamic response, and precise focus control.[2012-0345]
Zinc methacrylate (ZMA) and carbon black (CB) are incorporated into natural rubber/butadiene rubber matrix by direct mixing in a Banbury mixer. Tensile and tear tests showed that CB has a great reinforcing effect on rubber matrix. The results show that the amount of ZMA also plays an important role in mechanical properties. The addition of ZMA resulted in a significant increase of the optimum cure time even at lower loading. Incorporation of ZMA improved mechanical properties, such as tensile modulus and cure reinforcing parameter. The extraordinary improvement in properties is due to the formation of covalent and ionic crosslink. The composite containing only CB shows higher elongation at break, superior tensile strength, and tear strength than ZMA‐filled composites. Reinforcing effect of different composites has also been evaluated using different theoretical model. It has been observed that blowout time became slower and blowout temperature became higher as the ZMA content of the specimen increased. This represents multiple interactions between ZMA and rubber matrix. On the basis of the experimental results, possible mechanisms for reinforcement and microstructure of ZMA/rubber composites have been proposed. Both ZMA and CB provide better thermal stability especially for the composites, where the highest reinforcement effect is observed by mechanical analysis. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
There are various ICT technologies continuously being developed to reduce damage by industrial accidents. And research is being conducted to minimize damage in case of industrial accidents by utilizing sensors, IoT, big data, machine learning and artificial intelligence. In this paper, we propose a design method for a smart device capable of multilateral communication between devices and smart repeater in the communication shaded Areas such as closed areas of industrial sites, mountains, oceans, and coal mines. The proposed device collects worker’s information such as worker location and movement speed, and environmental information such as terrain, wind direction, temperature, and humidity, and secures a safe distance between workers to warn in case of a dangerous situation and is designed to be attached to a helmet. For this, we proposed functional requirements for smart devices and design methods for implementing each requirement using sensors and modules in smart device. And we derived evaluation items for performance evaluation of the smart device and proposed an evaluation environment for performance evaluation in mountainous area.
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