Raman amplification and pulsed lasing in cladding-pumped germanosilicate fiber

We report for the first time Raman amplification in a cladding-pumped fiber. The double-clad germanosilicate fiber was pumped by a Q-switched Er-Yb co-doped fiber laser at 1570 nm. The power conversion efficiency was up to 36%, with a slope of 64%

Rechargeable metal-metal alkaline batteries : Recent advances, current issues and future research strategies

Over the past few decades, remarkable advancement has been attained in the field of rechargeable metal–metal alkaline batteries (RABs). In terms of safety, energy density, charge-discharge capacity, and long-term storage capability, metal-metal RABs (e.g., Ni–Zn, Ni–Fe, Ni–Bi, Ni–MH, Ag–Zn, Co–Zn, Cu–Zn, and Bi–Zn systems) are contemplated as the promising energy storage devices for the applications in electric vehicles (EVs), hybrid EVs, grid-scale energy storage, as well as various implantable and wearable electronic devices. Especially, Ni-MH batteries become competitive with Li-ion batteries for EVs and hybrid EVs applications due to their high tolerance against mechanical abuse, stability under wide temperature ranges, and considerable charge/discharge capacity. Meanwhile, earlier works reviewed only specific topics, so, as a rapidly growing research topic, providing a deep understanding on metal–metal RABs is timely and worthwhile. So, in this work, we discuss the electrochemistry of all metal-metal RABs, then full cell designing with their performance will be discussed thoroughly. Further, issues associated with the existing metal–metal RABs and corresponding impro

Optimization of production conditions for activated carbons from Tamarind wood by zinc chloride using response surface methodology

The low-cost activated carbon was prepared from Tamarind wood an agricultural waste material, by chemical activation with zinc chloride. Activated carbon adsorption is an effective means for reducing organic chemicals, chlorine, heavy metals and unpleasant tastes and odours in effluent or colored substances from gas or liquid streams. Central composite design (CCD) was applied to study the influence of activation temperature, chemical ratio of zinc chloride to Tamarind wood and activation time on the chemical activation process of Tamarind wood. Two quadratic models were developed for yield of activated carbon and adsorption of malachite green oxalate using Design-Expert software. The models were used to calculate the optimum operating conditions for production of activated carbon providing a compromise between yield and adsorption of the process. The yield (45.26 wt.%) and adsorption (99.9%) of the activated carbon produced at these operating conditions showed an excellent agreement with the amounts predicted by the models. (C) 2009 Elsevier Ltd. All rights reserved

Optimization for the production of ammonia from urea in a semi-batch reactor for safe feedstock in power plants: Experimental and statistical studies

Urea hydrolysis for production of ammonia, in different application areas require safe use of ammonia, for removal of the NO(x) contaminates contained in a flue gas stream and increase in the efficiency of an electrostatic precipitator for the removal of fly ash from the flue gas stream. The single and combined effects of operating parameters such as initial feed concentrations, temperatures, reaction times, and stirring speeds on the production of ammonia from urea were analyzed using response surface methodology (RSM). Analysis of variance (ANOVA) showed a high coefficient of determination value (R(2) = 0.967) and satisfactory prediction second order regression model was derived. The optimum production conditions determined for semi-batch reactor were temperature 178 degrees C, initial feed concentration 22.24 wt% of urea, time of reaction 43.2 min and stirring speed 1045 rpm. At optimum conversion conditions, the conversion of urea for production of ammonia was found to be >= 13%

Experimental and theoretical investigation of parametric sensitivity and dynamics of a continuous stirred tank reactor for acid catalyzed hydrolysis of acetic anhydride

The continuous stirred tank reactor is a dynamic system exhibiting nonlinear behavior such as multiplicity and oscillations and, in certain range of operating conditions, may exhibit a parametric sensitivity where small changes in one or more of the input parameters lead to large changes in the output variable. In the present work, hydrolysis of acetic anhydride reaction system was used to demonstrate the existence of parametric sensitivity with respect to the input parameter, the cooling water flow rate. The applications of parametric sensitivity analysis were used for detection of parametric sensitivity in a continuous stirred tank reactor using catalyses hydrolysis of acetic anhydride reaction system. Also, theoretical investigation revealed that the effect of wall capacitance has definite influence on the dynamics of continuous stirred tank reactor. The continuous stirred tank reactor showed parametric sensitivity both in the regions of uniqueness and multiplicity, and a mathematical model was developed for the reactor. The numerically simulated results are in satisfactory agreement with the experimental data

Effect of temperature on dielectric properties and penetration depth of oil palm shell (OPS) and OPS char synthesized by microwave pyrolysis of OPS

Microwave-assisted pyrolysis is a promising technique for thermochemical treatment of various feedstocks mainly due to its efficient heating by 'conversion of electromagnetic energy into heat'. Microwave heating largely depends upon the dielectric properties of the material to be exposed to microwave radiation. Temperature dependence of dielectric properties along with penetration depth of oil palm shell (OPS) and OPS char have been investigated in the temperature range from 30°C to 600°C at 915 MHz and 2450 MHz frequencies. Measurement is made by HP 85070B open-ended coaxial probe attached to computer controlled HP 8722D Vector Network Analyzer (VNA). At room temperature, dielectric constant of OPS is higher than that of OPS char for both the frequencies. Dielectric constant and dielectric loss of both these materials decrease with the increase in the temperature. At room temperature, penetration depth corresponding to 2450 MHz is found to be lower as compared to that at 915 MHz frequency for both the materials, which makes 2450 MHz frequency to be more appropriate for microwave heating applications. Rise in temperature is seen to produce an increase of the penetration depth for both the materials. High dielectric constant and low penetration depth of OPS as compared to OPS char makes OPS to be more suitable for microwave heating. Experimental results of dielectric constant for both the materials are fitted to Boltzmann and Gauss models. Gauss model fits the experimental data of OPS more accurately while Boltzmann model is more suitable for OPS char

An overview of cathode material and catalysts suitable for generating hydrogen in microbial electrolysis cell

Bio-electrohydrogenesis through Microbial Electrolysis Cell (MEC) is one of the promising technologies for generating hydrogen from wastewater through degradation of organic waste by microbes. While microbial activity occurs at anode, hydrogen gas is evolved at the cathode. Identifying a highly efficient and low cost cathode is very important for practical implication of MEC. In this review, we have summarized the efforts of different research groups to develop different types of efficient and low cost cathodes or cathode catalysts for hydrogen generation. Among all the materials used, stainless steel, Ni alloys Pd nanoparticle decorated cathode are worth mentioning and have very good efficiency. Industrial application of MEC should consider a balance of availability and efficiency of the cathode material

Statistical modelling and optimization of hydrolysis of urea to generate ammonia for flue gas conditioning

The present study is concerned with the technique of producing a relatively small quantity of ammonia which can be used safely in a coal-fired thermal power plant to improve the efficiency of electrostatic precipitator by removing the suspended particulate material mostly fly ash, from the flue gas. In this work hydrolysis of urea has been conducted in a batch reactor at atmospheric pressure to study the different reaction variables such as reaction temperature, initial concentration and stirring speed on the conversion by using design expert software. A 2(3) full factorial central composite design (CCD) has been employed and a quadratic model equation has been developed. The study reveals that conversion increases exponentially with an increase in temperature, stirring speed and feed concentration. However the stirring speed has the greatest effect on the conversion with concentration and temperature exerting least and moderate effect respectively. The values of equilibrium conversion obtained through the developed models are found to agree well with their corresponding experimental counterparts with a satisfactory correlation coefficient of 93%. The developed quadratic model was optimized using quadratic programming to maximize conversion of urea within experimental range studied. The optimum production condition has been found to be at the temperature of 130 degrees C, feed concentration of 4.16 mol/l and stirring speed of 400 rpm and the corresponding conversion, 63.242%. (C) 2010 Elsevier B.V. All rights reserved