Friction Factor Evaluation Using Experimental and Finite Element Methods for Al-4%Cu Preforms

In this study, ring compression tests and finite element (FE) simulations have been utilized to evaluate the friction factor, m, under different lubricating conditions for powder metallurgical (P/M) Al-4%Cu preforms. A series of ring compression tests were carried out to obtain friction factor (m) for a number of lubricating conditions, including zinc stearate, graphite, molybdenum disulfide powder, and unlubricated condition. FE simulations were used to analyze materials deformation, densification, and geometric changes, and to derive the friction calibration curves. The friction factor has been determined for various initial relative densities and different lubricating conditions, and a proper lubricant for cold forging of P/M Al-4%Cu preforms is found. Studies show that the use of lubricants has reduced the friction. However, increase in the number of pores in the preforms leads to excessive friction. The FE simulation results demonstrate a shift in the neutral plane distance from the axis of ring specimen, which occurred due to variations in the frictional conditions and initial relative densities. The load requirement for deformation, effective stress, and effective strain induced, and bulging phenomena obtained by FE simulations have a good agreement with the experimental data.     

Recycling of cotton and polyester fibers to produce nonwoven fabric for functional sound absorption material

Recycled fibers are commonly used in dissimilar applications and one of the most important applications is sound absorption. Recycled fiber nonwovens currently are in greater demands in industries because of their advantages such as low cost, biodegradability, acceptable mechanical and physical properties, and so on. Sound absorption materials, renewable, and eco-friendly nonwovens have been developed using recycled cotton and polyester fibers. This research provides a contribution to the body of knowledge on the sound absorption properties of nonwovens using recycled fibers which contain cotton and polyester by means of spun-laid technique and provides a better understanding of the effects of a number of manufacturing processes on nonwovens noise control performance and also contributes to the wider adoption of nonwovens as sound absorbers. The sound absorption coefficients were measured according to ASTM E 1050 by an impedance tube method. The results revealed that the average of the sound absorption coefficients increased with the thickness of the nonwovens, but decreased with the nonwoven fabric density.     

Household's willingness to pay for improved water service: a case study in Shebedino District,Southern Ethiopia

Willingness to pay for basic water services is often high if the services are appropriate and affordable. This study was aimed at assessing the household's willingness to pay for improved water service in Shebedino District, Southern Ethiopia. The survey was administered to 635 participants from March 29 to April 26, 2008. Findings revealed that the majority of respondents (83.62%) were willing to pay 10 cents for 25 L of water. The average monthly expense of water was 2.36% of their average monthly income. Willingness of households to pay for improved water services was found to be better than the current expenditure.     

Transparent electrodes based on conducting polymers for display applications

The materials science and engineering related to the fabrication of conducting polymer thin films and the progress in the development of devices integrated with organic transparent electrodes based on conducting polymers for display applications are reviewed. Transparent electrodes are essential components for many display modules. With the evolution of display technologies, conducting polymers are recently emerging as important alternative materials for the fabrication of transparent electrodes. Conducting polymers offer some advantages, such as light weight, low cost, mechanical flexibility and excellent compatibility with plastic substrates for the development of next-generation display technologies and, in particular, are expected to play an important role in the development of flexible display technologies.     

Application of ANN-Based Streamflow Forecasting Model for Agricultural Water Management in the Awash River Basin,Ethiopia

This paper presents the application of a long-term streamflow forecasting model developed using artificial neural networks at a stream gauging station in the Awash River Basin, Ethiopia. The gauging station is located above the headworks of a large irrigation scheme called the Middle Awash Agricultural Development Enterprise (MAADE). Based on the forecasted streamflow time series and water requirements for irrigation and environmental purposes, appropriate agricultural water management strategies have been proposed for the irrigation scheme (MAADE). The water management strategies which were evaluated in this study are based on different scenarios of abstraction demands. These demands were formulated based on a range of options for agricultural development and change in MAADE. The scenarios evaluated were based on such factors as the existing planting patterns, changing planting dates, changing crop varieties and reducing the area under cultivation. An appropriate scenario of agricultural development was decided on the basis of the modified flows in the river vis-à-vis the trigger/threshold value established at the Melka Sedi stream gauging station. Considering all the scenarios, it is suggested that a 1–24% reduction in the area currently irrigated in the scheme will ensure a reliable supply of water to the scheme throughout the growing season and will provide sustainable environmental flow in the river.     

Farmers' Perception of Water Management under Drought Conditions in the Upper Awash Basin,Ethiopia

A survey was conducted in the Upper Awash River Basin, Ethiopia, to assess agricultural water management practices adopted by the farmers under drought conditions. The results show that on average drought prevails in the area once every two years and causes damage to both crops and livestock. Consequently, under such drought conditions, the farming communities have adopted various coping strategies and important among them are the sale of labour and sale of livestock and their products. The survey results also reveal that farmers in the rainfed agriculture areas practise mainly contour bunding to mitigate drought impacts.     

Multifunctional Carbon for Electrochemical Double‐Layer Capacitors

Multifunctional carbon materials are prepared for application as an active electrode material in an electrochemical capacitor displaying both charge storage and binder properties. The synthesis of the materials involves the functionalization of high surface area Black Pearls 2000 carbon black by a covalent attachment of polyacrylic acid. The polyacrylic acid polymer is formed by atom transfer radical polymerization using 1‐(bromoethyl)benzene groups initially bonded to the carbon by spontaneous grafting from the corresponding diazonium ions. The grafting of 1‐(bromoethyl)benzene and polyacrylic acid is confirmed by thermogravimetric analysis, Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, and nitrogen gas adsorption isotherm. The composite electrode films prepared from the modified carbon are more hydrophilic and have better wettability in an aqueous electrolyte than the one prepared with the unmodified carbon. The modified electrodes also show a higher specific capacitance (≈140 F g^?1), a wider working potential window (1.5 V) and excellent specific capacitance retention upon cycling (99.9% after 5000 cycles) in an aqueous 0.65 m K₂SO₄ electrolyte. Moreover, a relatively high specific capacitance (≈90 F g^?1) is maintained at a scan rate of 1000 mV s^?1 with the polyacrylic‐acid‐modified carbon electrode.     

Drought Analysis in the Awash River Basin,Ethiopia

This study analyzes drought characteristics in the Awash River Basin of Ethiopia based on meteorological and hydrological variables. Standardized precipitation index is used for temporal and spatial analyses of meteorological drought and the theory of runs is used to define hydrological drought by considering streamflow as the drought indicator. Drought severity maps are generated using Arc View/GIS by summarizing the percentage of occurrence of droughts in areas within the study basin. Extreme drought category on 12-month time scale indicated that extreme events occur most frequently in the Upper and Middle Awash Basin. However, while considering the overall categories of drought, the most frequent droughts occurred in the Middle and Lower Awash Basin during the period of analysis. Similarly, results based on hydrological drought analysis shows that the severest drought events occurred in the Middle Awash Basin during May 1988 to June 1988 and April 1998 to May 1998. Analysis of the relationship between meteorological and hydrological drought indices in the basin shows that occurrence of hydrological drought event at Melka Sedi stream gauging station lags meteorological drought event in the Upper Awash on average by 7 months with a variation of 3 to 13 months.