Sharif Digital Repository

In the light of the novel physical-chemical properties of supercritical water as a green reaction medium, we studied the synthesis of deuterated benzene in supercritical heavy water, in the presence of sodium deutroxide, as a catalyst. The effects of operational parameters including temperature, time, pressure (density), catalyst amount and benzene/D2O volumetric ratio on the degree of deuteriation (D%) and deuterated benzene yield were investigated extensively and the conditions for the highest degree of deuteration and product yield, were optimized. Furthermore, because of the importance of the pressure of solution inside the reaction medium on the H/D exchange process as well as the... 

Heavy metals belong to a group of lethal environmental pollutants. Ongoing efforts targeted at safeguarding public health have led to considerable attention being focused on methods that allow efficient extraction of these toxic substances. Polymer nanocomposites (PNCs) with their special characteristics are a class of adsorbents that demonstrate high potential for use in heavy metal extraction. As this process of removal is predominantly governed by adsorption, various parameters in PNCs’ chemical structure, as well as the metal solutions, can have a significant effect on the adsorption process. Herein, this review undertakes a survey of recently developed PNCs and their metal adsorption... 

The development of density or turbidity currents causes serious problems for environmental hydraulics in reservoirs. The stream entered to a reservoir can carry sediments, nutrients and chemicals as density or turbidity currents. The fate of sediment and other substances transported by the current depends on the characteristics of the turbidity current itself, i.e. the velocity of fluid, the amount of mixing with reservoir water and the rates of sediment deposition and resuspension. These are important factors for water quality in reservoirs. A two-dimensional, depth-averaged, finite-volume numerical model is developed to study density currents, driven by non-cohesive sediments. The model... 

As a part of the ongoing debate about competition in the electricity industry, regulators are increasingly considering performance-based regulation (PBR) as an alternative to improve the service quality. The fundamental principle behind PBR is that good performance should lead to higher profits, and poor performance should result in lower profits. A penalty-reward structure (PRS) in a PBR mechanism can enhance utility performance to align utility interests with customer's interests. During the implementation of PBR, regulators should spend or receive money to reward good performed utilities or penalised poor performed utilities, respectively. A technique is proposed, in this study, to not... 

As a part of the ongoing debate about competition in the electricity industry, regulators are increasingly considering performance-based regulation (PBR) as an alternative to improve the service quality. The fundamental principle behind PBR is that good performance should lead to higher profits, and poor performance should result in lower profits. A penalty-reward structure (PRS) in a PBR mechanism can enhance utility performance to align utility interests with customer's interests. During the implementation of PBR, regulators should spend or receive money to reward good performed utilities or penalised poor performed utilities, respectively. A technique is proposed, in this study, to not... 

Numerical simulation of dam-foundation-fault system, considering the earthquake source, propagation path, and local site effects, was carried out for realistic and reasonable seismic safety analysis of concrete dams. The Domain Reduction Method (DRM) was used for seismic analysis of Dam-Foundation-Fault (DFF) system, in which a modular two-step methodology for reducing the computational costs in large domain analysis was introduced. In this method, seismic excitation is directly applied to the computational domain such that assigning artificial boundary to the finite element models is more comfortable. In order to verify the implementation of the DRM in Finite Element Method (FEM), a simple... 

One of the main concerns in using commercial software for finite element analyses of dam-foundation-reservoir systems is that the simplifying assumptions of the massless foundation are unreliable. In this study, an appropriate direct finite element method is introduced for simulating the mass, radiation damping and wave propagation effect in foundations of dam-foundation-reservoir systems using commercial software ABAQUS. The free-field boundary condition is used for modeling the semi-infinite foundation and radiation damping, which is not a built-in boundary condition in most of the available commercial software for finite element analysis of structures such as ANSYS or ABAQUS and thus... 

Concrete dams are one of the most important infrastructures in every country and the seismic safety assessment of them is a major task in dam engineering field. Dam–foundation–reservoir system analysis is a complex interaction problem because this system consists of three domains with different behaviors. For accurate analysis of this system, some important factors should be considered such as foundation mass and earthquake input mechanism. In this paper, the effect of foundation mass and earthquake input mechanism on seismic response of concrete gravity dam is investigated. For this purpose, two different methods are introduced for modeling of massed semi-infinite foundation in finite... 

Seismic analysis of complex structures such as concrete dams has been the subject of numerous studies. One of the challenges in seismic analysis of such systems is proper modelling of massed foundation. Since concrete dams’ foundations are usually layered, this makes the homogenous half-space assumption relatively unrealistic. In this paper, the effects of massed layered foundation on seismic response of concrete gravity dams in dam-reservoir-foundation systems are investigated. Seismic finite element analysis of the system carried out using domain reduction method. This approach is compared with another available method named, free-field column. First set of analysis considers the effect of... 

Numerical simulation of dam-foundation-fault system, considering the earthquake source, propagation path, and local site effects, was carried out for realistic and reasonable seismic safety analysis of concrete dams. The Domain Reduction Method (DRM) was used for seismic analysis of Dam-Foundation-Fault (DFF) system, in which a modular two-step methodology for reducing the computational costs in large domain analysis was introduced. In this method, seismic excitation is directly applied to the computational domain such that assigning artificial boundary to the finite element models is more comfortable. In order to verify the implementation of the DRM in Finite Element Method (FEM), a simple... 

Seismic analysis of complex structures such as concrete dams has been the subject of numerous studies. One of the challenges in seismic analysis of such systems is proper modelling of massed foundation. Since concrete dams’ foundations are usually layered, this makes the homogenous half-space assumption relatively unrealistic. In this paper, the effects of massed layered foundation on seismic response of concrete gravity dams in dam-reservoir-foundation systems are investigated. Seismic finite element analysis of the system carried out using domain reduction method. This approach is compared with another available method named, free-field column. First set of analysis considers the effect of... 

Preparation and evaluation of chitosan-coated eggshell (CTS-ES) particles as a biosorbent for removal of Cu(II) ions from aqueous media was considered in this research. For this purpose, chitosan was coated on eggshell (ES) particles through precipitation procedure. The coated particles were characterized by Fourier transform infrared, thermogravimetric analysis, and field emission scanning electron microscopy analysis. Kinetic studies showed that coating of chitosan on ES particles improved their Cu(II) adsorption capacity. The removal of Cu(II) ions by either ES or CTS-ES particles followed the pseudo-second-order kinetics, indicating that chemical sorption is the rate-limiting step for... 

Preparation and evaluation of chitosan-coated eggshell (CTS-ES) particles as a biosorbent for removal of Cu(II) ions from aqueous media was considered in this research. For this purpose, chitosan was coated on eggshell (ES) particles through precipitation procedure. The coated particles were characterized by Fourier transform infrared, thermogravimetric analysis, and field emission scanning electron microscopy analysis. Kinetic studies showed that coating of chitosan on ES particles improved their Cu(II) adsorption capacity. The removal of Cu(II) ions by either ES or CTS-ES particles followed the pseudo-second-order kinetics, indicating that chemical sorption is the rate-limiting step for... 

This study proposes an approach for improving service reliability in the distribution network based on establishing competition among electric distribution utilities. The idea behind this approach is to categorise the utilities and compare the performance of utilities located in one cluster with the other members of the same cluster. The reward/penalty mechanism (RPM) as a quality regulating instrument is designed for each cluster and used to penalise the utilities with a performance worse than the benchmark and to reward them for providing a performance better than the benchmark. Based on the RPM, utilities located in one cluster compete to make more profit by serving customers in better... 

This study proposes an approach for improving service reliability in the distribution network based on establishing competition among electric distribution utilities. The idea behind this approach is to categorise the utilities and compare the performance of utilities located in one cluster with the other members of the same cluster. The reward/penalty mechanism (RPM) as a quality regulating instrument is designed for each cluster and used to penalise the utilities with a performance worse than the benchmark and to reward them for providing a performance better than the benchmark. Based on the RPM, utilities located in one cluster compete to make more profit by serving customers in better... 

The concerns of regulatory authority for the cost efficiency and service quality of distribution utilities has led them to implement monetary schemes, such as penalty/reward mechanism (PRM). PRM provides explicit financial incentives for distribution system operators (DSO) to maintain or improve their efficiency and quality of service. Although the effectiveness of the PRM is proven, analytical tools that can handle the complex decision-making process faced by decision makers to respond to PRM are scarce. This paper presents an approach for distribution system maintenance management in the presence of the PRM. The proposed approach tailors the maintenance plans by taking into account the... 

This paper investigates the effects of service quality regulation on investing in distribution automation. Among different regulatory instruments for quality regulation, the Reward-Penalty Scheme (RPS) has been selected to evaluate the effect of monetary incentive on behavior of Electric Distribution Utility (EDU) for service reliability. By implementing different automation strategies, the value of enhancing reliability indices and consequently the value of rewards and penalties are calculated for each strategy. For achieving to more realistic outcome, ten years horizon is considered. Furthermore, in the calculation of reliability indices, the time varying failure rate of components is... 

This paper investigates the effects of service quality regulation on investing in distribution automation. Among different regulatory instruments for quality regulation, the Reward-Penalty Scheme (RPS) has been selected to evaluate the effect of monetary incentive on behavior of Electric Distribution Utility (EDU) for service reliability. By implementing different automation strategies, the value of enhancing reliability indices and consequently the value of rewards and penalties are calculated for each strategy. For achieving to more realistic outcome, ten years horizon is considered. Furthermore, in the calculation of reliability indices, the time varying failure rate of components is...