In this paper, we investigate DIELECTRIC CONSTANT variation behavior in the Persian Gulf waters. We assumed average salinity of water is about 38 ppt and we studied static DIELECTRIC CONSTANT behavior versus temperature. Data collection is from ROPME (2001) cruise. Our studies show that in some stations we have strong perturbation in DIELECTRIC CONSTANT which allow us to know there is a water mass which has a different properties from around waters. Besides, in some coastal stations, this behavior is completely opposite.

A composite radome is a durable structure to protect telecommunication radar antennas against mechanical and environmental factors. Due to its placement in front of the antenna and the possibility of affecting the received and transmitted waves, in addition to the mechanical properties, the electromagnetic properties of this structure are very important. In this study, the mechanical properties (tensile strength in the direction of fibers) and the electromagnetic properties (DIELECTRIC CONSTANT at X-band frequency) for a GFRP composite radome has been studied and optimized. For this purpose, two types of glass fibers E and D series, and two types of epoxy resin and polyester resin have been used. In addition, three common methods of composite fabrication including hand layup, vacuum bag, and vacuum infusion have been used. Also, by using the Taguchi test design method and signal-to-noise analysis, the optimal composition was obtained for each of the properties, which for tensile strength of the combination of E series glass fibers and epoxy resin and vacuum bag fabrication method, the highest tensile strength was 320. 9 MPa and for the DIELECTRIC CONSTANT of D series glass fibers and epoxy resin and vacuum bag fabrication method with the lowest value of 2. 85 were determined. After determining the optimal composition for each of the properties, the optimum state was investigated by considering all the mechanical and electromagnetic properties factors together by using the multi-response optimization method (gray relation). Finally, a combination of D-series glass fibers, epoxy resin, and vacuum bag fabrication method was proposed.

Porous Silicon (PS) samples have been prepared by electrochemical anodization of p-type silicon wafer by varying HF concentrations in the electrolytic solution. The structural, surface morphological, optical and surface composition analysis of the prepared samples were done by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy studies respectively. The grain sizes of PS were determined by XRD study. The porosity of PS samples was estimated by using the parameters obtained from the SEM images by the geometrical method. The porosity of the samples was found to vary between 11% and 84% due to the variation in HF concentration in the electrolytic solution. The refractive index and DIELECTRIC CONSTANT values of PS as a function of porosity were determined by Effective Medium Approximation methods. Strong visible emission peak at 498 nm, with no apparent shift with respect to variation in etching parameter, is observed in Photoluminescence study. The surface bonding and their vibration modes of the PS were determined by transmission FTIR spectroscopy.

Time domain reflectometry (TDR) is a widely used method for measuring the DIELECTRIC CONSTANT (Ka) and bulk electrical conductivity (σa) in soils. The TDR- measured σa and Ka can be used to calculate the soil solution electrical conductivity, (σp). A theoretical model describing a linear relationship between bulk electrical conductivity, σa, and DIELECTRIC CONSTANT, Ka, in moist soil was already presented. By using this linear relationship, the pore water electrical conductivity, σp, can be estimated in a wide range of soil types without soil- specific calibration. The objective of this study was to evaluate the linear model presented previously for TDR. The previous study was on light texture soils but in this study we used clay, clay loam, loam, silty clay and silty clay loam textures. The results showed that the linear model performed well for light texture soils but not for heavy textures. Such poor result for heavy texture is mainly due to this fact that DIELECTRIC CONSTANT pore water was lower than 80 which was proposed as default by model. This study showed that for heavy texture soils DIELECTRIC CONSTANT of pore water is smaller than light textured soils.

A cluster model for active site of nanotube (C48) was presented and investigated the geometric structure and thermochemical parameters. Quantum-mechanical calculations were performed at the HF / STO-3G, 6-31G, 6-31G* and 6-31G** levels of theory in the gas phase and three solvents at four temperatures. Also, nuclear shielding parameters of the active site of nanotube have been taken into account using GIAO method at the HF / STO-3G, 6-31G, 6-31G* and 6-31G** levels of theory in the gas phase and in different solvents such as water, methanol, ethanol. The results were revealed that the NMR chemical shielding parameters are strongly affected by inducing different solvent media. According to these theoretical results of energy values, some important relationships have been found between the DIELECTRIC CONSTANT and structural stability of active site of nanotube.

Fused silica ceramics are widely used in electronics and aerospace industries. In the present study, 70 μ m of fused silica powder was milled to 10 μ m through fast milling. The appropriate slurry was prepared for slip casting with the powder-to-water ratio of 80: 20. After drying the specimens, the samples were sintered at different temperatures of 1100 ° C to 1400 ° C. The density increased upon increasing the temperature from 1. 79 to 1. 98 g/cm3. The phase transformation of the samples was investigated using XRD. The structure of the samples was analyzed using FTIR, and their microstructure was examined using a Field Emission Scanning Electron Microscope (FESEM). The bending strength of the samples was measured using the three-point method. According to the results, the cristobalite phase increased upon increasing the sintering temperature. The best flexural strength value (48. 7 MPa) was obtained for the sample sintered at 1300 ° C. The DIELECTRIC CONSTANTs of the fused silica ceramics were about 3-3. 8 in the frequency range of 8 to 12 GHz.

The autoprotolysis CONSTANTs (pKap) of water/ethanol mixtures containing 0-90 % v/v of ethanol have been determined at 25oC and 0.1 M Ionic strength using potentiometric method. Ionic strenght of each mixture was maintained by NaClO4 solution. The results indicate that water-ethanol mixtures are more basic media than pure water and the pKap value of this media increases with addition of ethanol. The influence of the DIELECTRIC CONSTANT of investigated mixture solvent on the autoprotolysis CONSTANT was described employing Yasuda-Shedlovsky procedure.

Time domain reflectometry (TDR) is used for determining soil water content nowadays. Amount and type of clay minerals in heavy soil can affect soil DIELECTRIC CONSTANT and cause the error in soil water content. The effect of the amount of clay minerals on soil water content was the subject of many researchers, but they did not work on the effect of the type of clay minerals. The aim of this research was the effect of type and amount of clay minerals on DIELECTRIC CONSTANT in heavy soils. For this purpose soil samples with different textures including clay, clay loam, loam, silty clay and sandy clay were taken. The results showed that with increasing the clay content, due to bound water and delay time, the soil DIELECTRIC CONSTANT decreased and consequently soil water content has been shown less than the real amount .The results also showed that Smectite group increased soil DIELECTRIC CONSTANT. Our results showed that the presented model with four phases including solid, air, bound water and free water in non saline soils presents acceptable results for volumetric water content. But in saline soil this model did not show accurate results. Consequently, soil salinity and clay type can affect on soil DIELECTRIC CONSTANT and water content.

Recently, due microelectronic technology developments, it is important to improve the electronic properties ceramic DIELECTRICs, for some applications e.g. capacitors. Accordingly, one of these advanced materials that has attracted much attention in recent research is NiO-based ceramics which shows an extraordinarily a range of high DIELECTRIC CONSTANT. In the present work, for the first time Li0.05Ni0.95O ceramic DIELECTRICs were prepared by mechanical alloying. The structure and microstructure of the milled powders were characterized by X-Ray diffraction (XRD) and Scanning Electron Microscopy (SEM) at different milling times. The quantitative analyses of the XRD results were done by the Rietveld refinement. According to the results, by milling operation, Nano crystallization and particles refinement were developed in which the crystallite and particles size of the powders reached to values of about 20 nm to 200 nm, after 24h of milling. In order to improve the DIELECTRIC properties, the 24h milled Li0.05Ni0.95O powders were mixed with iron oxide (Fe2O3) and after sintering process, the morphology of the Li0.05Fe0.02Ni0.93O sample studied by SEM. It revealed that the grains sizes remained in the submicron range. By measuring the DIELECTRIC properties of the Li0.05Fe0.02Ni0.93O sample using LCR meter at 120 Hz-200 kHz frequency range, high DIELECTRIC CONSTANT (about 5000) and relatively low loss (about 0.9) were obtained at 20 kHz which remained CONSTANT up to 200 kHz.

The microwave chamber disturbance method (CDM) is a commonly used procedure for determining the electromagnetic properties of materials in the microwave frequency range. This method is based on the change in the resonance frequency and the quality coefficient of a measurement chamber due to the penetration of the sample at the location of the maximum electric or magnetic field, depending on the nature of the parameter under study. The main limitation of the CDM is the requirement that the sample size must be small so as not to have a negligible effect on the geometry of the fields inside the chamber. In this paper, we propose an enhanced CDM for accurate measurement of DIELECTRIC CONSTANT and magnetic permeability of materials with very low error rates. The chamber consists of a rectangular waveguide with a cap that fits the location of the sample. This arrangement provides a suitable measuring device that minimizes the measuring errors, including the uncertainty in the perforated plate and use of liquid adhesive for sample-waveguide attachment. To validate the accuracy of the proposed method, the predicted values of DIELECTRIC CONSTANT and magnetic permeability of several sample materials are compared with their actual values and the error rate of this proposed method has finally reached less than 1. 5%.