Sharif Digital Repository

This Regular evaluation and analysis of river quality helps accurate management to reach acceptable quality. In this study, water quality indices (WQI) method applied to evaluate quality of Jajrood River which is one of the main sources of Tehran drinking water. It helps to subsidize management actions in Jajrood watershed. Sampling carried out for 9 years during 2001-2010 in 10 stations along the river in wet and dry stations to identify water quality and the main source of pollution. Results show water quality in all stations classifies as medium according to National Sanitation Foundation (NSF) and water quality index in wet season is better than the corresponding value in dry seasons.... 

Movements of the wheel loads and their sequential entry onto the bridges are known as the two root causes for the vibrations of the railway bridges. It is possible to reduce the levels of the unwanted bridge deck oscillations by introducing one or more size adjusted wagon(s) in the train configuration. The added wagon(s) are of different size(s) compared with the other cars in the train configuration. This can disturb the periodicity in the wheel loading. Consequently, it can interfere with the resonance phenomena and prevent the bridge from excessive vibrations. The purpose of this research is to calculate proper sizes for the anti-resonance rail vehicles. Such vehicles need to fulfil the... 

This paper presents the stability analysis for a single-phase phase-locked loop (PLL) for power systems applications. The dynamical equations of a previously presented single-phase PLL are systematically derived and linearized for design and stability analysis purposes. Based on the linearized model of the PLL, parameters of the loop filter and the PI controller are accurately determined. The main advantages of the PI controller are discussed as well as its design procedure. Moreover, it is shown that, unlike the conventional single-phase PLLs, the mentioned PLL does not suffer from double-frequency ripples. Simulations carried out in MATLAB and SIMULINK verify the performance of the PLL... 

In the present paper, the seismic response of an arch dam subjected to spatial variation of ground motions along the interface with its foundations is investigated. Recorded ground accelerations at the dam foundation interface of an arch dam were used for the purpose of this investigation. Topographic amplification between various points of the interface was studied by obtaining ratios of the response spectral displacement and spectral pseudo acceleration. Time shift and amplification between stations show the nonuniform nature of ground motions for large structures like dams. Recorded ground accelerations were interpolated for different nodes of the finite element model. The seismic... 

In this paper, a novel decentralized adaptive control scheme for multiagent formation control is proposed based on an integration of artificial potential functions with robust control techniques. Fully actuated mobile agents with partially unknown models are considered, where an adaptive fuzzy logic system is used to approximate the unknown system dynamics. The robust performance criterion is used to attenuate the adaptive fuzzy approximation error and external disturbances to a prescribed level. The advantages of the proposed controller can be listed as robustness to input nonlinearity, external disturbances, and model uncertainties, and applicability on a large diversity of autonomous... 

This paper is concerned with the disturbance attenuation problem of fuzzy large-scale systems which consist of N interconnected subsystems which are represented by Takagi-Sugeno fuzzy models. Using Lyapunov function and linear matrix inequalities (LMIs), a criterion is proposed to have a prescribed level of disturbance attenuation. A numerical example is given to illustrate the control design procedure and its effectiveness  

The desire to decrease electrical loading by using energy efficient lighting has resulted in a high level of attention to replacing conventional incandescent lamps with compact fluorescent lamps (CFL). In Iran from energy management point of view, people are encouraged by ministry of power to use CFLs. Also after elimination of subsidies, the substantial increase in electric energy price resulted in a high level of penetration of CFLs in electricity grid. CFL is a nonlinear load, therefore it injects harmonic to the network. In past, due to lower application of CFL, these harmonics were ignored, however today by the widespread application of CFLs; these small sources are combined and have... 

In this paper we present a method of localizing multiple wideband acoustic sources based on both signal attenuation pattern and delays in the reception of the signal. Moreover, an additional order of flexibility is added to the problem by considering the attenuation model as an unknown function with reasonable prior assumptions about its functional space. Such approach is capable of enhancing the localization performance compared to when only the signal attenuation data or the time delays are used. A cost function is then formed in terms of the sources locations and the attenuation model parameters. Having different types of unknowns in the cost function, convergence concerns, and the... 

One of the miscellaneous units that are frequently used in water and wastewater systems is flush tank. Flush tank increases the self cleaning velocity in the conduit, and helps to clear the conduits from deposits and contaminations. While these units have been used for many years, there is not enough information about the hydraulic performance of these units in respect to the discharge, distance from the tank and the pipe hydraulics. In this paper the experimental results from observed hydrographs at different distances from the flush tank in a pipe has been presented. The variables include; volume of releasing water (or inlet hydrograph), upstream head, pipe diameter (3 cm), pipe length and... 

In this paper, we introduce and investigate a cellular underwater wireless optical code division multiple-access (OCDMA) network based on optical orthogonal codes (OOC). The structures, principles, and performance of the underwater wireless OCDMA network in various water types are presented. Since underwater wireless optical links are considered for high-bandwidth underwater communications at short ranges, we will place a set of optical base transceiver stations (OBTS) each in the center of a hexagonal cell to cover a larger underwater area. The OBTSs are connected via fiber optic to an optical network controller (ONC) which operates as the core of the network. An integral expression for... 

Objective: Improving signal to noise ratio (SNR) and qualified images by the various methods is very important for detecting the abnormalities at the body organs. Scatter and attenuation of photons by the organs lead to errors in radiopharmaceutical estimation as well as degradation of images. The choice of suitable energy window and the radionuclide have a key role in nuclear medicine which appearing the lowest scatter fraction as well as having a nearly constant linear attenuation coefficient as a function of phantom thickness. Methods: The energy windows of symmetrical window (SW), asymmetric window (ASW), high window (WH) and low window (WL) using Tc-99m and Sm-153 radionuclide with...