Sharif Digital Repository

High-sulphur and medium-sulphur diesel fuels are still used in several countries. Although diesel particulate filter technology for on-road diesel engines has existed since 1989, the availability of high-sulphur and medium-sulphur diesel fuels in the market causes delays in the use of catalysed filter technologies. However, the situation in places such as Tehran is considered unhealthy because of particles and black carbon, and full distribution of ultra-low-sulphur diesel is awaited eagerly. The purpose of this study is to investigate the effect of the sulphur content in fuels on the gaseous and solid exhaust emissions of a 220 kW Euro II engine equipped with a sintered metal active-passive... 

In this study, the hydrodynamics and noise behaviour of marine propellers are examined through finite volume method under various operational conditions. The hydrodynamics of these propellers are studied both numerically and experimentally, and the characteristic curves are produced. Sheet cavitation inception and development conditions are also considered in order to understand the impact of different rotational speeds on propeller noise. Ffowcs Williams and Hawkings equations are used to extract the total sound pressure levels under non-cavitating and sheet cavitating conditions. Finally, the impact of cavitation on increasing the propeller noise is thoroughly explored and the results are... 

Nickel nanoparticles supported on MgO-Al2O3 and Al2O3 were synthesized by an impregnation method using dinitrobisethylenediamine nickel and nickel nitrate hexahydrate as precursors and were used as catalysts for CO methanation. Different MgO contents (1.5-11.25 wt %) were employed for the preparation of supports, and NiO loadings were in the range of 10-40 wt %. The optimum catalyst prepared from proper amounts of MgO (∼2 wt %) and NiO loading (20 wt %) with [Ni(en)2(H2O)2](NO3)2 as precursor and a mesoporous support with a wide range of mesopores resulted in highly dispersed nickel nanoparticles that exhibited moderate metal-support interactions, lower acidic surface sites, and enhanced... 

An experimental investigation was conducted on the oxidative desulfurization of model sulfur compounds such as dibenzothiophene and benzothiophene in toluene as a simulated light fuel oil with a mixture of hydrogen peroxide as the oxidant and various acids as the catalyst. The influences of various parameters including reaction temperature (T), acid to sulfur molar ratio (Acid/S), oxidant to sulfur molar ratio (O/S), type of acid, and the presence of sodium tungstate and commercial activated carbon as a co-catalyst on the fractional conversion of the model sulfur compounds were investigated. The experimental data obtained were used to determine the reaction rate constant of the model sulfur... 

Minimizing Hydrogen waste into fuel gas within the H2 network in a refinery is the objective function of an optimization problem in this paper. The superstructure obtained for a refinery wide concept, is first solved and validated for literature cases, then is reduced by heuristic rules, based on engineering judgment. The reduced superstructure contains all simulation procedures of pseudo-components definitions, fine tunings of all unit operations to reach actual operating conditions, reactions characterization, linear and nonlinear equalities and inequalities as system constraints. The set of governing equations are solved with Genetic Algorithm. Based on this optimization, in an Iranian... 

Mobile ad hoc networks allow to create very dynamic communication systems, which are independent from any fixed infrastructure. One of the most important issues regarding the management of an ad hoc network is the configuration of the system according to the way users move. Since a centralized control structure does not exist, we need to determine how the IP addresses must be assigned to the nodes in the network. In this paper we add a security mechanism to VASM protocol based on zero knowledge approach. A hash function has very low running time. So this so this scheme is very light-weight. The VASM protocol uses coordinate value of point in main address sheet for generating addresses. The... 

A new Zinc phosphating bath, which produces coatings at relatively lower temperatures within a reasonable time by using of chemical accelerators has been devised. Improvement of the bath performance by the addition of divalent cations like calcium, nickel has been studied. Bath formulation and operating conditions have been optimized by coating weight determinations. Stable samples of phosphating formulations with and without calcium and nickel salts were prepared and the structure and morphology of the phosphate coatings were determined by using X-ray diffraction (XRD) techniques, scanning electron microscopy. ASTMB117 salt spray test and electrochemical impedance spectroscopy (EIS) were... 

TiO2 nanoparticles were prepared by the sol - gel process using 2-hydroxylethy- lammonium formate as an ionic liquid. Nanoparticles were crystallized at various temperatures (300-700°C). The products were characterized using X-ray diffraction (XRD), nitrogen adsorption - desorption isotherms and scanning electron microscopy (SEM) techniques. It was found that the resulting TiO2 nanoparticles had good thermal stability either to resist collapse or the anatase-to-rutile phase transformation during heat treatment. The photocatalytic activity of the nanocrystalline TiO2 was evaluated by the degradation of Acid Blue 92 (AB92) which is commonly used as a textile dye. The results showed that the... 

This article presents a method for determination of meshing force distribution on contact region of spur gear teeth. In this method it is assumed that there are inter-connected springs on the teeth profile. These springs treat as capacitive fields. The compliance matrices of these fields are determined from the results of finite element analysis done on 3-D model of a gear. The tooth compliance matrix is used as a reference data to determine the tooth deformations for any meshing situation. The meshing force distribution is calculated using this reference data and Hertz theory for contacting bodies. The results of this analysis help in stress analysis under real operation conditions and more... 

A conic body packed bed reactor, internally irradiated with a UV-C lamp and equipped with circulating upflow stream was employed to investigate the decomposition of a widely used azo dye, direct red 16, in water. The synthesized nanostructure TiO 2 photocatalyst particles were immobilized on the surface of transparent Raschig ring packings. Solutions with initial concentration of 30 mg L -1 of dye, within the range of typical concentration in textile waste waters, were treated under the mild operating conditions of natural pH of 6.75 and temperature of 25 °C. Investigations on the active species showed that hydroxyl radicals play the major role in the process, providing a perfect degradation... 

This article addresses a combined approach of sliding mode control (SMC) with generalized predictive control (GPC) to achieve fluid temperature control in the evaporator of a heat recovery steam generator. The evaporator is modelled as a first-order plus dead time process. The model is developed using the experimental data obtained at an actual power plant. An output error identification algorithm is used to minimize the error between the model and the experiments in different operating conditions. A GPC method is exploited to optimize the sliding surface and the coefficients of the switching functions used in SMC. The proposed control schemes are evaluated by thorough simulation for... 

In this paper, the performance of a turbocharger twin-entry radial inflow turbine is investigated analytically and experimentally under steady state, full and partial admission conditions. In this modeling, the mass flow rate, pressure ratio and efficiency of the turbine are assumed unknown. The turbine geometry and the inlet total pressure and temperature are known, hence, the turbine performance characteristics can be obtained. In the turbocharger laboratory, performance characteristics of the turbine are determined, measuring the main parameters for various operating conditions. Comparing the model and experimental results shows good agreement. Also, considering the effect of test... 

The effect of the bath chemistry and operating conditions on the chemical composition, microstructure and properties of NiWmdashB alloys deposited from tartrate baths on working electrode was studied for the first time by the pulsed current method. The investigations included the measurement of the current efficiencies and determination of the tungsten content in the electrodeposits. UV spectrometry was used for characterisation of complex formation. The grain size of deposits was determined by XRD. Also, the morphology of the deposits was studied by SEM. Amorphous NimdashWB alloys were successfully obtained by electrodeposition from the tartrate bath. The corrosion behaviour of NiWmdashB... 

The effect of particle size on the catalytic activity of H-ZSM-5 zeolite in the methanol to propylene (MTP) reaction was investigated in a fixed-bed flow reactor under the operating conditions of T = 460 °C, P = 1 atm, and WHSV = 1 h-1. Nano and micro size H-ZSM-5 were prepared by reflux and hydrothermal crystallization methods, respectively. The nano and micro H-ZSM-5 were characterized using XRD, NH3-TPD, BET area, SEM and ICP-AES analytical techniques. Nano size H-ZSM-5 showed higher activity and stability compared to the micro size H-ZSM-5. Nano H-ZSM-5 was also found to have higher selectivity to propylene than the micro size H-ZSM-5. © 2009 Elsevier B.V. All rights reserved  

This work considers the problem of designing a fault tolerant system for IPMS motor drive subject to current sensor fault. To achieve this goal, two control strategies are considered. The first is based on field oriented control and a developed adaptive backstepping observer which simultaneously are used in the case of fault-free. The second approach proposed is concerned with fault tolerant strategy based on observer for faulty conditions. Stator resistance as possible source of system uncertainty is taken into account under different operating conditions. Current sensors failures are detected and observer based on adaptive backstepping approach is used to estimate currents and stator...