Current density measurements in direct methanol fuel cells

The current density in the fuel cell is the direct consequence of reactions taking place over the active surface area. Thus, measurement of its distribution will lead to identification of the location and nature of reactions and will give opportunity to improve the overall efficiency of fuel cells. Within this study, the current density distribution in a direct methanol fuel cell was analyzed by segmenting the current collector into nine sections. Besides, the effect of the different operating parameters such as molarity, flow rate and reactant gas on the current density distribution was analyzed.     

Synthesis and Photodiode Characterization of Novel Twisted Carbazole Derivatives with 1,3,5-Benzene Core

In this study, considering the information given in the literature the Ullman and Suzuki-Miyaura coupling reactions were carried out using carbazole, 1,3,5 tribromo benzene and aryl boronic acid. The synthesized novel carbazole derivative (CPF4) were characterized by 1H NMR and 13C NMR. The photophysical and thermal properties of the synthesized novel carbazole derivatives CPF4 were investigated Graphene oxide (GO) doped CPF4/p-Si photodiodes were fabricated. The electrical properties of these photodiodes were characterized by current–voltage (I?V) and capacitance–voltage (C?V) measurements. The photocurrent properties of the diode were studied under various illumination intensities. The photoresponse properties of the diodes increased with GO content. The results indicate that CPF4:GO/p-Si heterojunctions can be used as a photodetector for optoelectronic applications.     

Fuel cell and ultra-capacitor hybridization: A prototype test bench based analysis of different energy management strategies for vehicular applications

An energy storage system with sufficient power capacity should be incorporated with fuel cells (FCs) to compensate the slow dynamics of FCs. Ultra-capacitors (UCs) are potential candidates for a solution in this aspect. A test bench of such an FC/UC hybrid configuration that can emulate the dynamics of vehicular systems is presented in this paper. Namely, the test bench performance verification of wavelet transform and fuzzy logic based energy management strategy that was discussed in earlier simulation-based studies of the authors is investigated. Of equal importance is the comparison of the cascade wavelet-fuzzy logic based strategy with the case of using only fuzzy logic in the energy management is presented. Experimental results with small-scale devices, a PEMFC (5 kW, 48 V) manufactured by Plug Power^® Company, and a UC bank composed of 430 F, 16 V and 165 F, 48 V UC modules manufactured by Maxwell Technologies^® Company, illustrate the successful performance analysis of employed energy management schemes during similar motor cycles.     

Analysis of some comfort and structural properties of cotton/spandex plain and 1×1 rib knitted fabrics

Spandex is increasingly used in either every course or alternating courses of knitted fabrics to impart a greater level of stretch and form stability than that can be achieved with cotton alone. The incorporation of spandex to the fabric structure effects many of the fabric properties. In this study, 100% cotton, half-plated and full-plated, plain and rib fabrics which are very commonly used in underwear and outerwear clothing are investigated for physical, dimensional, geometrical, and some comfort properties and compared to each other. Several conclusions could be obtained such as the wicking heights of the plain fabrics were higher than those of the 1×1 rib fabrics. Transfer wicking ratios of the half-plated fabrics were the highest, whereas the transfer wicking ratios of the full-plated fabrics were the lowest. Extension under constant load and residual deformation ratios decreased with the addition of spandex and the increase in spandex content. Plain fabrics generally performed better than 1×1 rib fabrics in terms of residual deformation ratios.     

Ultrasonic testing to measure the stress statement of steel parts

This paper presents an efficient method for stress measurement propagation. Pulse-echo method are used as stress measurement method on railway wheels. Hard service conditions and brake failures can lead to dangerous stress on the railway wheels. Stress measurements so important for wheels. Especially wheel expose to severe drag braking conditions in freight service. Residual stresses can significantly reduce the engineering properties and fatigue life of materials such as railway components. The paper presents results of stress state investigation of ER7 steel. Finally, the article briefly discusses how to adopt the pulse-echo method to railway wheels. Reducing cost of residual stress measurement investigated.

     

A fuzzy logic based supervisory controller for an FC/UC hybrid vehicular power system

Depending on growing concerns on energy crises and environmental issues, fuel cell (FC) powered electrical vehicles are favored for possible substitute to conventional internal combustion engine (ICE) based vehicular systems. However, the typical power profile of an automobile motor consisting of transients is not suitable for the use of a sole FC system for vehicle propulsion. This shortcoming could be partly overcome by hybridization. Two potential benefits of combining an FC system with an energy storage unit, ultra-capacitor (UC) has been presented in this study. Firstly, the durability of the FC system could be improved because the additional energy source can fulfill the transient power demand fluctuations. Secondly, the ability of the energy storage source to recover braking energy enhances the fuel economy greatly. An important aspect in designing a hybrid power structure is to find a suitable control strategy that can manage the active power sharing and take advantage of the inherent scalability and robustness benefits of the hybrid system. An integrated procedure for mathematical modeling and power control strategy design for an FC/UC hybrid vehicle is presented in this paper. A fuzzy logic supervisory controller based power management strategy that secures the power balance in hybrid structure, enhances the FC performance and minimizes the power losses is proposed. The main contribution of this paper apart from the previous studies of the authors is the modeling of the complete FC power system with air supply compressor and the integration of the control of the FC system internal dynamics (especially the oxygen excess ratio) into the overall supervisory control structure to maximize the efficiency and durability. To demonstrate the effectiveness of the proposed power management scheme, simulation studies were performed using MATLAB^®, Simulink^® and SimPowerSystems^® environments by integrating the detailed mathematical and electrical models of the hybrid vehicular system.     

Production and characterization of particleboards from cork-rich <Emphasis Type="Italic">Quercus cerris</Emphasis> bark

Single-layered particleboards were produced from granulated Quercus cerris bark containing cork and phloem granules using standard hot-press equipment and phenol–formaldehyde resin. The experimental boards were tested for thickness swelling, mechanical strength and thermal properties. Scanning electron microscopy observations were carried out to analyze the panel structure. The results showed that Q. cerris bark particleboards had low thickness swelling in water, high resistance to thermal degradation and high calorific values but their mechanical strength was below that of commercial wood particleboards. The produced Q. cerris bark particleboards were adequate for exterior applications where mechanical strength is not the key factor. Potential for process and feedstock optimization was acknowledged.