Sharif Digital Repository

Over past decades, extensive research has been performed on the measurement of land subsidence as a result of compaction of aquifer. This paper describes results from a new field-monitoring system to evaluate changes in matric suction and temperature profiles in soil layers over an extended time period. The monitoring system used in this study consists of inserting dielectric sensors into a 105 m borehole, drilled in a site in Ardabil Plain, The monitoring results from the site were used to calibrate predictions from HYDRUS-1D. The physical and hydraulic properties of the soil materials in different layers were obtained through performing some soil characteristics and filter paper tests... 

The local electric field distorsion induced by a dielectric particle leads to particle–particle interactions and assembly which is very interesting for their useful applications on microfluidic devices. Particles behavior becomes more complicated if several particles interact at the same time. This paper presents a comprehensive numerical analysis of the assembly and particle–particle interactions for two similar and dissimilar dielectric particles immersed in a dielectric fluid using the immersed interface method based on two-dimensional direct-current dielectrophoresis. The immersed interface method is a finite-difference (or finite element) based numerical method which its key advantage... 

Plasma actuator is a flow control device to improve the aerodynamic performance of wind turbine blades at low airspeeds. One of the most robust numerical models for simulation of plasma actuator interaction with the fluid flow is the electrostatic model. This model is improved recently and is extensively verified by the authors. Due to the high cost of performing experimental optimizations, the optimized geometrical dimensions and materials of a plasma actuator may be sought by this numerical model. The aim of the present study is the aerodynamic enhancement of a DU21 wind turbine blade airfoil in which the effect of geometric parameters and the dielectric material is examined separately.... 

The mixed nano-ferrites materials Cu0.6Zn0.4HoxFe2−xO4 (0.00 ≤ x ≤ 0.12) were prepared via the sol–gel auto combustion technique. The TGA curve established the annealing temperature (500 °C) for phase formation. The single exothermic peak on the DSC plot occurred at 341 °C temperature. XRD patterns of these nano ferrites verified single phase formation of the FCC cubic structure. The lattice constant a was increased from 8.4244 to 8.4419 Å and then its value decreased to 8.4319 Å. Crystallite size was found in the range of 7 to 16 nm. The surface morphology of the samples was observed from the scanning electron microscope (SEM) images. The grain size was found within the range of 90 nm to... 

The mixed nano-ferrites materials Cu0.6Zn0.4HoxFe2−xO4 (0.00 ≤ x ≤ 0.12) were prepared via the sol–gel auto combustion technique. The TGA curve established the annealing temperature (500 °C) for phase formation. The single exothermic peak on the DSC plot occurred at 341 °C temperature. XRD patterns of these nano ferrites verified single phase formation of the FCC cubic structure. The lattice constant a was increased from 8.4244 to 8.4419 Å and then its value decreased to 8.4319 Å. Crystallite size was found in the range of 7 to 16 nm. The surface morphology of the samples was observed from the scanning electron microscope (SEM) images. The grain size was found within the range of 90 nm to... 

The influence of indium on the properties of Cu0.5Zn0.5Fe2O4 nano ferrites synthesized by sol–gel auto-combustion technique was studied. X-ray diffraction (XRD) analysis demonstrated that pure and substituted ferrites possessed cubic spinel structure. The lattice parameter increases with the inclusion of In3+ for x ≤ 0.16 and decreases subsequently. A linear decrease in crystallite size was found as concentration of indium increased. X-ray density, strain, and dislocation density were increased as indium content increases. Hopping lengths as well as radii of A and B sites revealed increasing behavior up to x = 0.16 and decreased thereafter. The spectral bands indicated the formation of... 

The influence of indium on the properties of Cu0.5Zn0.5Fe2O4 nano ferrites synthesized by sol–gel auto-combustion technique was studied. X-ray diffraction (XRD) analysis demonstrated that pure and substituted ferrites possessed cubic spinel structure. The lattice parameter increases with the inclusion of In3+ for x ≤ 0.16 and decreases subsequently. A linear decrease in crystallite size was found as concentration of indium increased. X-ray density, strain, and dislocation density were increased as indium content increases. Hopping lengths as well as radii of A and B sites revealed increasing behavior up to x = 0.16 and decreased thereafter. The spectral bands indicated the formation of... 

Gupta et al. [J. Opt. Soc. Am. B. 24, No. 5 (2007)] have introduced a localized upward plasma density ramp to overcome the defocusing of a laser beam. We report that there are fundamental mistakes in their work. First, the density profile formula that they have introduced is dimensionally incorrect. Second, the calculated dielectric constant is wrong as well, which renders their main spot size equation and the quantitative results unacceptable, and it seriously falters the results of the self-focusing. We correctly derived a new equation of the spot size, and the computational curves are also presented  

In this paper, we investigate the impact of the electromagnetic scattering caused by other objects in nonfree space on the time-averaged force exerted upon a Rayleigh particle, which is conventionally referred to as the backaction effect. We show that backaction modifies the gradient force, radiation pressure, and spin curl force exerted upon Rayleigh particles, and gives rise to an additional force term which stems from the gradient of the backaction field in nonfree space. As a numerical example, we look into the trapping of a dielectric nanoparticle at the center of curvature of a spherical mirror, and study how it is affected by the backaction effect. We show that backaction can enhance... 

Feedback vibration is a standard feature in almost every home video game console controller to vibrate in selected circumstances, such as when the user's character kick the ball or hit the opponent, to immerse the player in the game. In the handheld game consoles this feature causes the handheld game consoles to vibrate. But the handheld game consoles are different than home video game consoles. In this paper we examine the suitability of using feedback vibration in the handheld game consoles. We evaluated feedback vibration popularity among the users. We used Nintendo DS handheld game consoles for this evaluation  

By rapid growth of technology in recent years, many services are provided for disabled people. Using wireless devices such as mobile phones in healthcare is a new idea which is gained attracted by some developers in recent years. On the other hand, nowadays game consoles are not only for playing games, but also have more functions such as using for education. Considering the above mentioned facts, this paper proposes a method to aid speech-impaired children using Nintendo DS Game console. This method helps the speech-impaired children which are not capable of using sign language well to communicate with others until they learn sign language well. Because the Nintendo DS is the most popular... 

In this paper a new empirical-physical method for calculation of path loss in the fixed wireless access in suburban areas is proposed. It is shown that this method has a relatively good accuracy for high transmitter antennas. Since in fixed wireless access, high transmitter antennas are used, we can use this method for this kind of communications and in special case for systems based on IEEE 802.16a. In this method a new empirical model for calculation of path loss exponent is used which is based on measurements reported in various papers and in contrast to other models, the effect of receiver antenna height in the path loss exponent is considered. The first step of this method is the... 

A hybrid method is introduced for analysis of the H-plane waveguide discontinuities. It combines multimode contour integral and mode matching techniques. The process is based on dividing the circuit structure into key building blocks and finding the multimode scattering matrix of each block individually. The multimode scattering matrix of the whole structure can be found by cascading these blocks. Also contour integral method is developed for analysis of multi-media circuits. Therefore, it is possible to analyze H-plane waveguide filters with dielectric resonators using this method. The accuracy and run time of the purposed method is compared with those reported in literatures and/or Ansoft... 

The remarkable properties of graphene nanoribbons (GNRs) make them attractive for nano-scale devices applications, especially for transistor and interconnect. Furthermore, for reduction interconnects signal delay, low dielectric constant materials are being introduced to replace conventional dielectrics in next generation IC technologies. With these regards, studding the effect of varying dielectric constant (e{open}r) on relative stability of graphene nanoribbons interconnect is an important viewpoint in performance evaluation of system. In this paper, Nyquist stability analysis based on transmission line modeling (TLM) for graphene nanoribbon interconnects is investigated. In this... 

An improved phenomenological model is presented for numerical simulation of a Dielectric Barrier Discharge (DBD) plasma actuator for separation control of high angle of attack flow over a wind turbine airfoil. Based on existing numerical models and experimental measurements, a new model is proposed for prediction of the length of a plasma extent which is more consistent with previous observations. The electrical and hydrodynamic solvers used in the present study are validated against published experimental data. Then the applicability of a DBD actuator, mounted on a DU 91-W2-250 airfoil is extensively analyzed for a wide range of operating voltages and frequencies. The analysis is completely... 

In radio channels modelings, the phases and amplitudes of the rays undergo some modifications when they are reflected from or transmitted through a particular material. These reflection and transmission coefficients make use of the electrical properties of the materials, thus, it is essential to know the values of the relative dielectric constant and of the conductivity or the loss tangent of the materials that appear in the propagation environments. In this paper, a theoretical model based on the inter-molecule interactions, has been developed and used to estimate the dielectric parameters of glass. ©2009 IEEE  

The present study numerically investigates the feasibility of using multiple dielectric barrier discharge (multi-DBD) plasma actuators as a novel approach for active flow control over a large horizontal axis wind turbine rotor. The National Renewable Energy Laboratory 5 MW offshore wind turbine is used as the baseline case. This turbine uses pitch control system to adjust the generated power above its rated wind speeds, but at lower speeds, this system remains inactive. In this paper, the operational condition speed is considered lower than the rated wind speed. The mathematical electro-static model is implemented to simulate the effects of plasma actuator on the external flow and the... 

This paper investigates the stall control over an airfoil employing dual excitation of separated shear layers with dielectric barrier discharge plasma actuators. This novel approach is studied experimentally on the NACA 0015 airfoil at the angle of attack and Reynolds number of 14° and 0.3×106, respectively. To analyze the baseline flow, Time-averaged pressure distributions on the airfoil surfaces are evaluated with 40 pressure taps. Further, the dominant natural frequencies associated with flow structures in the airfoil wake are examined utilizing a hot-wire anemometer. Two plasma actuators, one on the suction side just upstream the separation point and the other on the pressure side at the...