Sharif Digital Repository

Palladium nanoparticles immobilized on a cross-linked imidazolium-containing polymer were evaluated as a catalyst for Suzuki carbon-carbon cross-coupling reactions using water as the solvent. The nanocatalysts show good catalytic activities for aryl iodides and aryl bromides and moderate activity with aryl chloride substrates. Coupling of sterically hindered substrates could also be achieved in reasonable yields. The heterogeneous catalyst is stable, can be stored without precautions to exclude air or moisture, and can be easily recycled and reused  

Objective(s): Multiple sclerosis (MS) is considered as a chronic type of an inflammatory disease characterized by loss of myelin of CNS. Recent evidence indicates that Interleukin 17 (IL-17)-producing T helper cells (Th17 cells) population are increased and regulatory T cells (Treg cells) are decreased in MS. Despite extensive research in understanding the mechanism of Th17 and Treg differentiation, the role of microRNAs in MS is not completely understood. Thereby, as a step closer, we analyzed the expression profile of miR-9-5p and miR-106a-5p, and protein level of retinoic acid receptor (RAR)-related orphan receptor C (RORC; Th17 master transcription factor) as direct target of miR-106a-5p... 

Job scheduling in MapReduce plays a vital role in Hadoop performance. In recent years, many researchers have presented job scheduler algorithms to improve Hadoop performance. Designing a job scheduler that minimizes job execution time with maximum resource utilization is not a straightforward task. The primary purpose of this paper is to investigate agents affecting job scheduler efficiency and present a novel classification for job schedulers based on these factors. We provide a comprehensive overview of existing job schedulers in each group, evaluating their approaches, their effects on Hadoop performance, and comparing their advantages and disadvantages. Finally, we provide... 

Three newly synthesized room temperature ionic liquids containing molybdate anion, [DMIm][MoO 2(NCS) 4], [RPy][MoO 2(NCS) 4] (R = butyl or decyl), and previously reported [BMIm][MoO 2(NCS) 4] were used as catalysts for the reduction of sulfoxides. For facilitating the recyclability of the catalysts, the ionic liquids [RMIm][PF 6] and [RPy][PF 6] (RMIm = 1-n-alkyl-3-methylimidazolium, RPy = 1-n-alkylpyridinium) were applied as ionic solvents and toluene is used as solvent for the organic phase. Molybdenum salts immobilized in RTILs constituted a reusable and efficient heterogeneous catalyst system. A maximum conversion (>99%) was achieved for reduction of diphenyl sulfoxide to diphenyl... 

Two room temperature liquid salts containing molybdenum(VI), [BMIM] 2[MoO2(NCS)4] (1) and [DMIM] 2[MoO2(NCS)4] (2), were immobilized on ionic liquid-modified silica leading to materials which showed notable catalytic activity for the reduction of sulfoxides into sulfides with triphenylphosphine (PPh3). The molybdenum liquid salts immobilized on the supported ionic liquid phase could be reused at least for three catalytic cycles without significant loss of activity  

Some cis-dioxomolybdenum (VI) complexes with tridentate Schiff base ligands derived from salicylaldehyde and aminophenols, aminoalcohol or o-aminobenzenethiol were examined as catalysts for epoxidation of different aliphatic and aromatic olefins, with tert-butyl hydroperoxide as oxidant. All complexes exhibited high activity and selectivity for epoxidation of aliphatic substrates during a short time period (95% conversion of cyclooctene after 30 min). The epoxide yield increased with the nucleophilic character of olefin. The catalysts activation strongly depends on the reaction temperature and nature of the solvent. Epoxidation of olefins by these catalysts is inhibited by ligands or... 

A series of cross-linked ionic polymers based on styrene-functionalized imidazolium salts with chloride, hexafluorophosphate, or tetrafluoroborate counter anions have been prepared and characterized using a range of analytical and spectroscopic techniques and electron microscopy. The polymer with the chloride anion is an efficient catalyst for the cycloaddition of carbon dioxide with epoxides to afford cyclic carbonates. The cross-linked polymer is insoluble in organic solvents and is highly stable and therefore can be easily recycled and reused  

This paper simulates Al2O3-water nanofluid flow and forced convection around a rotating circular cylinder. The governing parameters are Reynolds number (1 ≤ Re ≤ 100), solid volume fraction of nanoparticles (0 ≤ φ ≤ 0.05) and non-dimensional rotation rate (0 ≤ α ≤ 3). The simulations are performed to study the effects of mentioned parameters on the heat transfer rate and fluid flow characteristics. The governing equations including the continuity, momentum, and energy equations are solved with a finite volume method. It is observed that the reduction of heat transfer with increase in rotation rate is in the vicinity of 6.9% and 32% for Re = 5 and 100, respectively at φ = 0.05. Furthermore,... 

In this paper vehicle path-following in the presence of rollover risk is investigated. Vehicles with high centre of mass are prone to roll instability. Untripped rollover risk is increased in high centre of gravity vehicles and high-friction road condition. Researches introduce strategies to handle the short-duration rollover condition. In these researches, however, trajectory tracking is affected and not thoroughly investigated. This paper puts stress on tracking error from rollover prevention. A lower level model predictive front steering controller is adopted to deal with rollover and tracking error as a priority sequence. A brake control is included in lower level controller which... 

High center of mass vehicles are likely to rollover in extreme maneuvers. Available works present control strategies to prevent rollover. In these works, however, other important parameters such as path trajectory tracking are not a main concern. In this paper conflicts between rollover prevention and trajectory tracking is investigated. Model predictive control (MPC) is adopted to predict and avoid rollover while tracking desired trajectory. For this regard a model based future error estimation is introduced. The control framework predicts both rollover and trajectory error simultaneously. It avoids rollover while tries to track the trajectory. Simulation results for two controllers with... 

In this paper, a study is conducted to determine the influences of perforated anchors on heat transfer intensification of turbulence nanofluid flow in a pipe. Six different turbulence models are used, and the results obtained by these models are benchmarked with the existing theoretical data to select the best turbulence model. The outputs showed that the k–ε–RNG–scalable wall function model has higher accuracy and so it is selected to simulate this problem. The influences of various parameters including the addition of perforation on the anchors, the perforation diameter (in the range of 1–5 mm), the Re number (in the range of 5000–25,000), and the volumetric concentration of nanoparticles... 

There are various cases in physics and engineering sciences (especially communications) where one requires the envelope probability density function (pdf) of the sum of several random sinusoidal signals. According to the correspondence between a random sinusoidal signal and a random vector, the sum of random vectors can be considered as an abstract mathematical model for the above sum. Now it is desired to obtain the pdf of the length of the resulting vector. Considering the common and reasonable assumption of uniform distributions for the angles of vectors, many researchers have obtained the pdf of the length of the resulting vector only for special cases. However in this paper, the pdf is... 

We proposed a Primal-Dual Interior Point Method (PDIPM) to solve a combined Environmental and Economic Power Dispatch (EEPD) problem. The EEPD problem is a multiobjective problem with competing and non-commensurable objectives. The PDIPM produces a set of nondominated Pareto optimal solutions for the problem. Fuzzy set theory is employed to extract a compromise nondominated solution. The proposed algorithm is applied to the standard IEEE 30 bus six-generator test system. Comparison of our PDIPM results with the various algorithms reported in the literature shows that the solutions of the proposed algorithm are very accurate for the EEPD problem  

As the ordinary least squares (OLS) method is very sensitive to outliers as well as to correlated responses, a robust coefficient estimation method is proposed in this paper for multi-response surfaces in multistage processes based on M-estimators. In this approach, experimental designs are used in which the intermediate response variables may act as covariates in the next stages. The performances of both the ordinary multivariate OLS and the proposed robust multi-response surface approach are analyzed and compared through extensive simulation experiments. Sum of the squared errors in estimating the regression coefficients reveals the efficiency of the proposed robust approach. © 2018 Taylor... 

As the ordinary least squares (OLS) method is very sensitive to outliers as well as to correlated responses, a robust coefficient estimation method is proposed in this paper for multi-response surfaces in multistage processes based on M-estimators. In this approach, experimental designs are used in which the intermediate response variables may act as covariates in the next stages. The performances of both the ordinary multivariate OLS and the proposed robust multi-response surface approach are analyzed and compared through extensive simulation experiments. Sum of the squared errors in estimating the regression coefficients reveals the efficiency of the proposed robust approach. © 2017 Taylor... 

Nowadays, many manufacturing and service systems provide products and services to their customers in several consecutive stages of operations, in each of which one or more quality characteristics of interest are monitored. In these environments, the final quality in the last stage not only depends on the quality of the task performed in that stage but also is dependent on the quality of the products and services in intermediate stages as well as the design parameters in each stage. In this paper, a novel methodology based on the posterior preference approach is proposed to robustly optimize these multistage processes. In this methodology, a multi-response surface optimization problem is... 

The local oscillator phase noise can severely affect the performance of OFDM systems. In this paper a new method is presented for compensation of this phase noise. The method is based on the fact that the scattered pilots, which are used for channel estimation, are subject to the same phase error as the OFDM symbols. Least square approach is used to exploit the phase noise information that exists in the scattered pilots and compensate the phase noise on the OFDM symbols. Simulation results show that the method is very effective, especially in high SNR  

Following Gorokhovsky and Lott and using an extension of the b-pseudodifferential calculus of Melrose, we give a formula for the Chern character of the Dirac index class of a longitudinal Dirac type operators on a foliated manifold with boundary. For this purpose we use the Bismut local index formula in the context of noncommutative geometry. This paper uses heavily the methods and technical results developed by E. Leichtnam and P. Piazza