Sharif Digital Repository

In this study the ability of artificial neural network (ANN) in forecasting the daily NASDAQ stock exchange rate was investigated. Several feed forward ANNs that were trained by the back propagation algorithm have been assessed. The methodology used in this study considered the short-term historical stock prices as well as the day of week as inputs. Daily stock exchange rates of NASDAQ from January 28, 2015 to 18 June, 2015 are used to develop a robust model. First 70 days (January 28 to March 7) are selected as training dataset and the last 29 days are used for testing the model prediction ability. Networks for NASDAQ index prediction for two type of input dataset (four prior days and nine... 

In this work the effects of backwash pressure, duration of acid and sodium hydroxide backwashing, sodium hydroxide concentration, and the duration of forward washing on performance of permeate flux recovery (PFR) were investigated. A two-level fractional factorial design (FFD) was used to design the experiments. The ability of back propagation neural network (BPNN) and radial basis function neural network (RBFNN) in predicting the performance of cleaning-in-place (CIP) of hydrophilic polyethersulfone (PES) membrane were investigated. It is found that BPNN has better ability in predicting the PFR performance than RBFNN. The best architecture of BPNN was a network consisting of 1 hidden layer... 

Physical separation methods, especially membrane technology, can be a good substitute for biological wastewater treatment, due to its simple constructions and operations. There are many papers and patents in this field. Membranes need to be cleaned periodically to be able to operate economically, and need to be replaced after a while. Several factors can influence the membrane cleaning procedure, including pressure of backwash, acid and base concentration, duration of forward washing, and duration of acid-base backwashing. In this study the effect of these parameters was investigated to find an optimum condition which could result in a good polyethersulphone (PES) membrane cleaning with less... 

In this work, the process of starch removal from starchy wastewater using a hydrophilic polyethersulfone membrane was investigated. The pore size of the membrane was 0.65 μm and the pattern of stream in plate and frame handmade membrane module was cross-flow. To design the layout of the experiments, response surface methodology was applied. The performance of the filtration process was evaluated by calculating the (chemical oxygen demand) COD removal percentage (rejection factor) and permeate flux. In this study, five operative parameters were investigated, including trans-membrane pressure, flow rate and temperature of feed, pH, and the COD concentration of starch wastewater. Two models... 

As a primary step of establishment of an extensive air shower array consisting 20 scintillation detectors we optimized an individual detector. Square shaped scintillators are placed under a metal pyramid Light Enclosure with a photomultiplier tube (PMT) at the vertex of it. A set of experiments are performed to optimize the height of light enclosures by comparing 4 different heights 0.1, 0.2, 0.3 and 0.4 m. These experiments are supported by a Monte Carlo simulation of detection process. In this article, by considering experimental and simulation results we concluded that 20 cm is an optimum height for light enclosures  

The unique properties of modified Hermite pulses is utilized to develop a novel pulse technique for Ultra Wideband (UWB) communications. The proposed method increases the bandwidth of the pulse up to 10 GHz and overcomes the coexistence problem of UWB and vulnerable narrowband systems through suppressing narrowband interference. Consequently it improves the range of UWB communications by increasing the power, without disturbing the narrowband systems. The pulse technique is implemented in high frequency pulse generation circuits and could be fully integrated in BiCMOS process. The nulls of the frequency response are tuned to be located in a definite narrowband system with the number of the... 

Purpose - A numerical method is developed to capture the interaction of solid object with two-phase flow with high density ratios. The current computational tool would be the first step of accurate modeling of wave energy converters in which the immense energy of the ocean can be extracted at low cost. Design/methodology/approach - The full two-dimensional Navier-Stokes equations are discretized on a regular structured grid, and the two-step projection method along with multi-processing (OpenMP) is used to efficiently solve the flow equations. The level set and the immersed boundary methods are used to capture the free surface of a fluid and a solid object, respectively. The full... 

A computational tool is developed to capture the interaction of solid object with two-phase flow. The full two-dimensional Navier–Stokes equations are solved on a regular structured grid to resolve the flow field. The level set and the immersed boundary methods are used to capture the free surface of a fluid and a solid object, respectively. A two-step projection method along with Multi-Processing (OpenMP) is employed to solve the flow equations. The computational tool is verified based on numerical and experimental data with three scenarios: a cylinder falling into a rectangular domain due to gravity, transient vertical oscillation of a cylinder by releasing above its equilibrium position,... 

In this paper a new IR-UWB pulse generator circuit is proposed which is capable of solving the coexistence problem of narrowband and ultra wideband communication systems. This is done by creating a notch in the PSD of the generated UWB signal and adjusting its center frequency at the frequency of the narrowband interference. Using a triangular pulse generator, a triangular signal is generated and applied to the proposed circuit which consists of three main function blocks including quadratic, exponential and differentiator circuits. A differential pair MOS transistors in sub threshold region is utilized in order to realize the exponential block. The circuit is designed using a 0.18-μm RF... 

An assessment study of two different shunt FACTS devices for compensating disturbances due to voltage variation in power systems is presented in this paper. Namely, Static Compensator (STATCOM) and Static Var Compensator (SVC) are Considered in this study. Eigen Value analysis and nonlinear time domain simulations for starting motor, motor in load varying state and short circuit on motor terminals show that STATCOM DC Voltage regulation has a better performance Compared to that of SVC. The result that will be presented in the paper will prove the superiorly of STATCOM over SVC in increasing motor speeding up and improving system voltage profile particularly at starting. © 2005 IEEE  

This paper introduces a straightforward technique for parameters estimation of the RC equivalent circuit model of a battery cell with the main aim of its implementation in real-time digital simulator frameworks. The RC model parameters are precisely estimated by the analysis of the battery cell voltage curve during relaxation time using the pulse current test. In this regard, Least-squares fitting is used to mitigate the error of the battery cell voltage response, which leads to a precise estimation of the RC model parameters as a function of the state-of-charge. Exponential and Gaussian functions are utilized to define the resistances and the capacitances in the RC model respectively based... 

This paper presents an evaluation of two distinct techniques to improve energy absorption capability of an accordion cellular structure with close-to-zero Poisson's ratio. For this purpose, fiber-reinforcement and foam-filling methods were employed to address the material enhancement and to obtain light and tough structures with high specific energy absorption. Employing an innovated additive manufacturing based on material extrusion process, specimens of glass fiber-reinforced PLA were produced in both in-plane directions to compare with the un-reinforced counterpart. In continue, some of the 3D printed samples were strengthened by means of polyurethane foam in their hollow structure. The... 

Clay liners are widely used as porous membrane barriers to control solute transport and to prevent the leakage of leachate both in horizontal and vertical flow scenarios, such as the isolated base and ramps of sanitary landfills. Despite the primary importance of saturated hydraulic conductivity in a reliable simulation of fluid flow through clay barriers, there is no model to predict hydraulic conductivity of clayey soils permeated with saline aqueous solutions because most of the current models were developed for pure water. Therefore, the main motivation behind this study is to derive semi-empirical models for simulating the hydraulic conductivity of clayey soils in the presence of... 

There are many steel structures in Iran with semi-rigid saddle connections. It has been observed that, during a strong earthquake, this type of connection can experience a premature fracture, which will endanger the stability of the structure. The present study endeavored to improve the mechanical characteristics including the initial stiffness, yield moment, maximum moment, crack rotation, and load transfer mechanisms of the conventional saddle connections using retrofitting methods. An experimental study was conducted on six full-scale specimens to study the effect of the retrofitting methods on the stiffness, yield moment, and maximum moment of the connection and for the prevention of... 

Saddle connections are semi-rigid connections that are widely used in Iran. Many existing buildings contain this type of connection. The present study conducted full-scale experiments and used extensive numerical modeling to study the mechanical characteristics of saddle connections. The mechanical characteristics examined were the moment-transfer mechanism, initial stiffness, yield moment, maximum moment, and fracture rotation. The configuration and dimensions of the experimental and numerical specimens were chosen to be similar to those of saddle connections in existing buildings. A parametric study was conducted to determine the factors affecting the mechanical characteristics of these... 

Analysis of an extensive air shower (EAS) detected by surface arrays highly depends on the determination of core locations. Here we present a new method to find the core location of an EAS that, unlike the common methods, does not depend on the lateral distribution function and uses arrival times of secondary particles. This method improves the accuracy of finding the core location of a low-energy EAS in the internal parts of an array, in comparison with common methods  

The most important goal of studying an extensive air shower is to find the energy, mass and arrival direction of its primary cosmic ray. In order to find these parameters, the core position and arrival direction of the shower should be determined. In this paper, a new method for finding core location has been introduced that utilizes trigger time information of particle detectors. We have also developed a simple technique to reconstruct the arrival direction. Our method is not based upon density-sensitive detectors which are sensitive to the number of crossing particles and is also independent of lateral distribution models. This model has been developed and examined by the analysis of... 

Introduction: Therapeutic exercises are regarded as one of most important therapeutic interventions for patients with chronic low back pain. Stabilization exercises are among the most practical ones for these patients. Effects of these exercises on psychological factors associated with pain and consequential functional disabilities are still remained unknown. The purpose of this study was to assess the effect of stabilization exercises on fear of pain, movement and disability in patients with low back pain. Materials and Methods: Twenty one patients with recurrent non-specific low back pain (14 in experimental, 7 in control group) were participated in this study. The scores for fear of pain,...