Thermodynamics and kinetics of methane hydrate formation and dissociation in presence of calcium carbonate

Huge amount of gas hydrate deposits are identified in deep marine sediments, which may be considered as a future source of energy. Since carbonate is one of the major components of marine sediments, in the present study attention has been given to characterize methane hydrate formation and dissociation in presence of calcium carbonate. Experiments were performed with 0%, 2%, 4%, 6% and 10% by weight of calcium carbonate in distilled water. Extensive investigations have been done on pressure-temperature equilibrium behavior of hydrate formation and dissociation at varying concentrations of calcium carbonate. Hydrate formation rate was found to vary with concentration of calcium carbonate as the solubility of calcium carbonate in water is controlled by the presence of simultaneous chemical equilibria involving a high number of species like Ca²⁺, CO₃^2?, HCO₃^?, CO₂, etc. Induction time for hydrate formation has also been measured at different concentrations of carbonate. Nucleation point for the hydrate formation was observed to be slightly higher at higher concentration of calcium carbonate due to increased heat absorption. Dissociation enthalpy of hydrates was calculated by using Clausius-Clapeyron at different measured conditions. Moles consumption of methane gas during hydrate formation at different concentrations of carbonate was measured using real gas equation and found to be minimum at 10?wt%.     

Uniformly convergent non‐standard finite difference methods for singularly perturbed differential‐difference equations with delay and advance

A new class of fitted operator finite difference methods are constructed via non‐standard finite difference methods ((NSFDM)s) for the numerical solution of singularly perturbed differential difference equations having both delay and advance arguments. The main idea behind the construction of our method(s) is to replace the denominator function of the classical second‐order derivative with a positive function derived systematically in such a way that it captures significant properties of the governing differential equation and thus provides the reliable numerical results. Unlike other FOFDMs constructed in standard ways, the methods that we present in this paper are fairly simple to construct (and thus enrich the class of fitted operator methods by adding these new methods). These methods are shown to be ε‐uniformly convergent with order two which is the highest possible order of convergence obtained via any fitted operator method for the problems under consideration. This paper further clarifies several doubts, e.g. why a particular scheme is not suitable for the whole range of values of the associated parameters and what could be the possible remedies. Finally, we provide some numerical examples which illustrate the theoretical findings. Copyright © 2005 John Wiley & Sons, Ltd.     

Efficient design and implementation of a robust coplanar crossover and multilayer hybrid full adder–subtractor using QCA technology

The Journal of Supercomputing - Quantum dot cellular automaton (QCA) is a novel emerging nanometer-scale-based circuit design using nanocomputing technology, which overcomes the limitations of...     

Restructuring the Indian agro-fresh food supply chain network: a mathematical model formulation

Clean Technologies and Environmental Policy - In traditional Indian agro-fresh food supply chain (AFSC), authors identify the following four shortcomings through the literature survey: (1)...     

OFDM Link with a Better Performance Using Artificial Neural Network

In this paper, a scheme for reducing the peak-to-average power ratio (PAPR) primarily and bit error rate simultaneously in orthogonal frequency division multiplexing using feed forward artificial neural network is proposed and analyzed. The proposed scheme switches one or more null-carriers with data subcarriers to offer minimum PAPR and requires no channel side information during transmission. To reduce high computational complexity, a multilayer neural network with Levenberg–Marquardt training algorithm is used. The proposed scheme thus suits to supplement some of other PAPR-reduction methods with low rate hit and complexity.     

Determination of optical and electrical properties of ZnSe thin films

A thin film of zinc selenide (ZnSe) was deposited onto a clean glass substrate using a vacuum evaporation technique. This thin film was characterized through X-ray diffraction, which indicated that the film was polycrystalline in nature. Absorption and transmission spectra of this thin film were recorded using a spectrophotometer. The energy band gap, refractive index and extinction coefficient were determined using these spectra. It was found that the energy band gap of ZnSe film was 2.55 eV. It was also observed that the refractive index and extinction coefficient of the film decreased with the increase of wavelength. The conductivity of this thin film was determined by current–voltage measurement using an electrometer over the temperature range from room temperature to 413 K. It was observed that conductivity increased with increase in temperature. This is explained on the basis of structural changes occurring due to the change in grain size and the increase in carrier density.     

Heteropolyacid-clay nano-composite as a novel heterogeneous catalyst for the synthesis of 2,3-dihydroquinazolinones

The present research work is intended to synthesize a series of substituted 2,3-dihydro-2-phenylquinazolin-4(1H)-ones using clay-supported heteropolyacid as a novel heterogeneous, reusable and inexpensive catalyst. This catalyst afforded excellent yields in very short reaction times that shows high selectivity without affecting other functional groups, such as carbon–carbon double bond and heterocyclic moieties. The catalyst could be recycled at least six times and reused. The synthesis involves cyclo-condensation of anthranilamide with an aldehyde at room temperature in the presence of small amount of the catalyst. No column purification is required and products can be purified by simple crystallization.     

Development of novel strategies for designing sustainable Indian agri-fresh food supply chain

Traditional Indian agri-fresh food supply chain (AFSC) is unorganized and controlled by a large number of intermediaries, causing it to be unsustainable from the farmer (low profitability) to the customer (not getting quality product even after paying a high price). The purpose of this paper is to propose novel strategies for designing a sustainable Indian AFSC. Authors identify shortcomings as well as strengths, weaknesses, opportunities and threats (SWOT) of the Indian agriculture system through the literature survey. To improve overall performance of this chain, authors have developed eighty strategies by incorporating SWOT into TOWS (threat, opportunity, weakness and strength) matrix. They define four key objectives to mitigate the afore-mentioned problems. In this paper, twelve strategies are shortlisted from existing ones on the basis of fulfilling a maximum number of objectives. The shortlisting of strategies is further verified by evaluating strategies using performance measures (PMs) in sustainability dimensions, which revealed that the twelve chosen strategies dominate over other strategies. The shortlisted strategies are mainly focused on improving the economic dimension of AFSC by satisfying maximum number of objectives and PMs. The chosen strategies pledge for the optimum and most feasible ones to be recommended for managers/researchers towards redesigning the AFSC. The proposed viable strategies are expected to reform the conventional Indian AFSC by designing sustainable supply chain (SSC). The outcomes of this work will provide clear guidelines for researchers and policy makers to make sustainable agriculture.