Current subsidies to residential water users in Oman are estimated at USD 314 million/y. This study estimates the demand function for residential water in Muscat, Oman, for households living in villas. A two-stage least squares econometric model with lagged average water price was used with socio-economic variables. Price elasticity for residential water in Muscat was estimated as –2.10. This high price elasticity is explained by the large proportion of water used for outdoor purposes. This study indicates that it may be possible to manage water demand in Muscat through modifying the price of water and reforming subsidies for residential water. 相似文献
A stochastic model was developed to simulate the polymerisation kinetics and the detailed microstructure of the resulting polymers made by the living radical polymerisation of styrene initiated by epoxide radical ring opening. The model was used to predict monomer conversion, average molecular weight, polydispersity index, and molecular weight distribution as a function of polymerisation time. Simulations were used to explore the effects of rate constant values on chain microstructures and polymer properties and validated with experimental data published in the literature. It was found that some parameters, such as the exchange rate constant, have no significant effect on the polymerisation kinetics, whereas major effects were observed when other rate constants, such as the reduction rate constant, were changed. 相似文献
Summary: A dynamic Monte Carlo model was developed to simulate atom‐transfer radical polymerization (ATRP). The algorithm used to describe the polymerization includes activation, deactivation, propagation, chain transfer, and termination by combination and disproportionation reactions. Model probabilities are calculated from polymerization kinetic parameters and reactor conditions. The model was used to predict monomer conversion, average molecular weight, polydispersity and the complete molecular weight distribution at any polymerization time or monomer conversion. The model was validated with experimental results for styrene polymerization and compared with simulation results from a mathematical model that uses population balances and the method of moments. The simulations agree well with experimental and theoretical results reported in the literature. We also investigated the control volume size and number of iterations to reduce computation time while keeping an acceptable noise level in the Monte Carlo results.
Comparison of the chain length distribution of polystyrene made with ATRP and conventional free radical (CFR) polymerization at 50% conversion. The initiator to monomer ratios are 1:100 (ATRP left peak), 1:500 (ATRP right peak), and 1:1000 (CFR). 相似文献
The engineering properties (physical and mechanical) of Wadi Al-Yamanyah natural aggregate were determined. In addition, correlations between these properties have been made. This Wadi is located in the central part of the western province of Saudi Arabia between Makkah and Taif. The aggregate along the Wadi was studied and five major rock units were identified namely granite, granodiorite, gneiss amphibole schist and andesite. These rocks were classified into three aggregate groups: basalt, granite and schist. Ninety aggregate samples were carefully collected and tested. The results of overall aggregate properties pointed out that Wadi Al-Yamanyah natural mixed aggregate is within the international and local specification limits and it is suitable for use in concrete. The estimated volume of natural aggregate in the Wadi is about 2 million m3. The engineering properties of individual aggregate groups were also determined. Basalt and schist groups, which represent about 65% of the Wadi natural aggregate, were of higher quality and low degree of alterations than the granite group. Direct and inverse relationships were found between some physical and mechanical properties for mixed natural aggregate of Wadi Al-Yamanyah with the exception of elongation index (IE). It is recommended to use the derived equations, representing the best fit between the aggregate properties, with care and for rough estimation only. 相似文献