Sharif Digital Repository

Conventional wastewater treatment processes are not completely effective in removing vancomycin. In this study, affecting parameters on vancomycin degradation, such as pH, catalyst, initial vancomycin concentration, temperature, and reaction time were investigated simultaneously during a removal process based on titanium dioxide with ultraviolet irradiation in an aqueous solution. Titanium dioxide was synthesized and characterized using X-ray diffraction and scanning electron microscopy. The average size of the synthesized crystals was 4.7 (± 0.2) nm. Design of experiments was done by a central composite design based on the response surface methodology and multiple linear regression was... 

Investigations have shown the traces of antibiotics in surface water, groundwater, wastewater treatment plants, and drinking water. However, conventional wastewater treatment is not entirely effective for vancomycin degradation. Advanced oxidation is one of the most widespread methods of antibiotic degradation in aqueous media. Vancomycin was quantified by high-performance liquid chromatography. The Response Surface Methodology (RSM) based on Central Composite Design (CCD) was used to explore and optimise the effect of the independent variables on vancomycin degradation. Independent variables were as follows: pH (3–11), vancomycin concentration (15–75 mg/L), TiO2–clinoptilolite (25–125 mg in... 

This paper deals with the determination of free vibration characteristics and instability conditions of flexible spinning cylinders partially filled with fluid. Using the linearized Navier-Stokes equations for the incompressible, inviscid flow, a 2D model is developed for fluid motion at each section of the cylinder. The forces exerted on the cylinder wall as a result of the fluid motion are calculated as functions of lateral acceleration of the cylinder axis in the Laplace domain. Applying the Hamilton principle, the governing equations of flexural motion of the cylinder are derived and then combined with the equations describing the fluid forces to obtain the coupled field equations of the... 

An analytic method to predict the oscillation amplitude and supply current values of a differential CMOS LC oscillator is discussed. The phase noise performance for this kind of oscillator is predicted by using a simplified model. This method enables us to design an optimized oscillator in terms of minimum phase noise and power consumption. The validity of the presented method is demonstrated by designing an LC CMOS oscillator in a 0.24μm CMOS technology. The predictions obtained from the derived expressions are in good agreement with simulation results over a wide range of the supply voltage. © 2004 IEEE  

Non Line of Sight (NLOS) propagation is a challenging issue which the performance of network based wireless localization is limited by errors primarily caused by NLOS corruption. NLOS is inherently a dominant source of errors in metropolitan area wireless networks, like cellular one, so in this paper we discuss our proposed algorithm within cellular network terminology. This paper contributes two novel algorithms. The first one is to extract the NLOS state of base station (BS) and the second one is a correction algorithm to enhance the measurements accuracy. Our proposed algorithm discuses a novel localization technique to estimate true mobile terminal (MT) location from a set of possibly... 

Non Line of Sight (NLOS) propagation is a challenging issue which cause large errors in wireless localization systems. NLOS is especially a dominant source of errors in metropolitan area wireless networks like cellular ones. We discuss our algorithms within cellular network terminology. This paper contributes two novel algorithms. The first algorithm is to extract the NLOS state of base stations and the second one is a correction algorithm to enhance the measurements accuracy. Our introduced algorithms can easily operate with other wireless localization algorithms and reduced NLOS error. These algorithms are proposed for network-based localization because of the amount of calculation  

This paper presents the application of reduced order modeling technique for investigation of liquid sloshing in three-dimensional tanks. The governing equations of sloshing are written using a boundary element formulation for incompressible potential flow. Then, the governing equations are reduced to a more efficient form that is represented only in terms of the velocity potential on the liquid free surface. This particular form is employed for eigen-analysis of fluid motion and the sloshing frequencies and mode shapes are determined. Then, the sloshing frequencies and the corresponding right- and left-eigenvectors are used along the modal analysis technique to find a reduced order model... 

In the present work, an artificial neural network (ANN) model was developed for predicting the effect of thermo-mechanical processing on the forming limit diagram (FLD) of low carbon steels. The model introduced here considers the content of carbon, the hot finishing temperature, the degree of cold work, the work hardening exponent, the initial yield stress and the ASTM grain size as inputs; while, the predicted FLDs are presented as outputs. The results show that the predicted FLDs by the ANN model are very accurate exhibiting the maximum error of 9% over the whole strain region. The model predicted that with increasing the degree of cold rolling before annealing, the drawability is... 

Nonlinear dynamics of an extensible cantilevered pipe conveying pulsating flow is considered in this paper. The fluid flow fluctuates harmonically and exhausts via a nozzle attached to the end of the pipe. Taking into account the extensibility assumption, the coupled nonlinear lateral–longitudinal equations of motion are derived using Hamilton's principle and discretized via Galerkin's method. The adaptive time step Adams algorithm is applied to extract the time response, and then the bifurcation, power spectral density and phase plane maps are plotted for some case studies. Effects of some geometrical parameters such as flow mass, pulsating flow frequency, gravity, nozzle mass and nozzle... 

In our previous work, a distributed moisture sensor based on the induced long-period fiber grating in the presence of moisture is proposed. The proposed structure is analyzed numerically (Opt Laser Technol 117:126–133, 2019). In this article, due to the axial symmetry and periodic structure of the proposed sensor, the Love’s potential and Fourier series are employed to obtain an analytical solution for the refractive index variation along the sensor versus moisture density. The analytical method reduces the computation time relative to our numerical calculation drastically. The analytical results are in good agreement with those that are obtained by numerical calculations. The analytical... 

This paper aims to revisit the effect of sloshing on the flutter characteristics of a partially liquid-filled cylinder. A computational fluid-structure interaction model within the framework of the finite element method is developed to capture fluid-structure interactions arising from the sloshing of the internal fluid and the flexibility of its containing structure exposed to an external supersonic airflow. The internal liquid sloshing is represented by a more sophisticated model, referred to as the liquid sloshing model, and the shell structure is modeled by Sanders' shell theory. The aerodynamic pressure loading is approximated by the first-order piston theory. The initial geometric... 

In the present study a new, fast, precise algorithm for studying hydroelastic stability of a typical section with two degrees of freedom (2DOF) is proposed based on the finite element method (FEM), while the partial sheet cavitation effects are considered. For this means, the steady cavity boundary is calculated by some conventional iterative procedures, developed based on the potential flow simulation. Thereafter, assuming that the amplitude and the frequency of the body oscillations are altered so that the cavity length in unsteady flow remains unchanged, the simulation of the unsteady hydrodynamic flow is performed by imposing some velocity fluctuations over the rigid cavity boundary. For... 

The design of a fully-integrated ΔΣ -controlled fractional-N frequency synthesizer is described. Using a dual modulus 64/72 prescaler based on injection locking technique and a novel third order digital ΔΣ modulator, we achieved an extremely low power synthesizer in 2.5GHz band.. Total power dissipation of the frequency synthesizer is less than 6mW at a 1.5V supply. The loop bandwidth is optimized to achieve a -123dBc/Hz phase noise at 3MHz offset frequency. The locking time of the loop is less than 30μs  

A cyclic forward-backward extrusion (CFBE) process was used as a severe plastic deformation (SPD) technique to produce ultrafine-grained aluminum rods. Yield strength and tensile strength of the specimens increased by increasing the number of CFBE cycles, while elongation to break decreased due to an increase in the grain refinement and microhardness. According to transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) results, the average grain size was reduced from 120 μm to 315 nm after only 3 cycles of CFBE  

This article presents a process of numerically predicting and experimentally verifying the dispersion quality and penetration level of fuel particles entering and moving in various directions relative to vortex engine walls. If the length scale of particles considered in this study is not comparable to the chamber length and, furthermore, the density is ignored, the effect of the particle on the flow field can be neglected and a one-way solution will be viable for the problem. The solutions in each case are carried out to estimate the particle trajectory and parameters affecting it. The governing equations are converted to a set of nonlinear, coupled, ordinary differential equations (ODEs)... 

Particle dispersion in the vortex flow has been one of the most interesting subjects in recent years. Bidirectional vortex flow field is an industrial sample of the rotating flow which is used to obtain advantages of better mixing and combustion. In this work penetration and dispersion quality of the particles which are entering from various positions on the vortex engine walls have been numerically predicted. Head side, end side, and sidewall are considered as the entering positions. The particle has been assumed to be a rigid sphere. Initial velocity, diameter, and density of entering the particles are assumed to be known. If the particle length scale is considered not to be comparable... 

this research chamber effective length, which is the minimum chamber length required for complete combustion, for a dilute monopropellant spray, constant area, one dimensional and fixed volume engine is analytically predicted. A new evaporation rate in the form of dk +1 relation, instead of d 2 law, is introduced. In case of controlling the vaporization by radiative heat transfer, k is equal to zero, and when molecular processes control the vaporization, k will be equal to unity and in some cases the vaporization data need the value of k greater than one to fit properly to related equation. Development of this approach can be used in design of combustion chambers with optimum length and with... 

In spite of the development of different experimental methods and theoretical models devoted to understand and predict the asphaltene behavior in dead/model oils, the asphaltene aggregation phenomena in live oil systems at high pressure-high temperature conditions has been grossly missing in the available literature. In this study, a population balance model with geometric scaling approach is proposed to simulate the asphaltene aggregates growth in time for live oil systems. Appropriate collision kernels are incorporated to describe the aggregation mechanisms taking into account the effect of pressure, temperature and oil characteristics. In modeling of the asphaltene aggregation phenomena... 

Asphaltene precipitation and deposition is a serious issue in all facets of petroleum production and processing. Despite the numerous experimental efforts concerning asphaltenes, the effect of temperature on asphaltene precipitation and aggregation in live oils remains an elusive and controversial subject in the available literature. In this work, a series of high pressure-high temperature depressurization experiments were designed to assess the effect of temperature on asphaltene precipitation and aggregation in light live oils. Asphaltene related experiments were performed using a high pressure microscope and high pressure-high temperature filtration setup on a light live oil with a low... 

The thorough knowledge of the asphaltene aggregation phenomena and pressure/temperature related kinetics is helpful for accurate prediction/control of the asphaltene issues in all facets of petroleum production/processing. However, characterizing the asphaltene aggregation phenomena in live oils at high pressure-high temperature conditions is not well discussed in the available literature. In this work, the asphaltene aggregation phenomena as well as the kinetics of aggregation at different levels of pressure and temperature are investigated in light and heavy live oils using high pressure microscope. The results are presented and discussed in terms of asphaltene onset pressure, aggregates...