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.

In this work, the nanocomposites of chitosan containing carbon nanotubes (CNT) and maghemite nanoparticles have been prepared by solution casting method. Techniques such as Raman spectroscopy, SEM, TEM, DIELECTRIC relaxation spectroscopy, and VSM studies were made.  The incorporation of CNT in to the chitosan matrix and also the interaction between the CNT and the maghemite nanoparticles were studied using Raman spectroscopy. The DIELECTRIC CONSTANT of Chitosan-CNT composites turned from positive to negative at low frequency when CNT concentration increased from 10 to 20wt%. Interestingly, addition of 20wt% of maghemite nanoparticles into the Cs-CNT nanocomposites affected both the DIELECTRIC property and the conductivity of the composite. VSM measurement shows that the prepared maghemite nanoparticles and the Cs-CNT-maghemite nanocomposites are superparamagnetic materials. Observed DIELECTRIC characteristics and the electrical conductivity of the samples have been explained by using a model. Tuning of negative permittivity in the chitosan-CNT nanocomposites by using maghemite nanoparticles could be useful as metamaterials.

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.

Hypothesis: The technology of preparing materials with desired DIELECTRIC CONSTANTs is used in designing and manufacturing telecommunication equipment. Foaming of the polymers is an effective method to reduce their DIELECTRIC CONSTANT further, as the influence of the microstructural characteristics of the expanded polystyrene foams is important for their DIELECTRIC characteristics and mechanical properties. This article focuses on the effect of cell wall thickness of the expanded polystyrene foams on their DIELECTRIC CONSTANT, loss factor, hardness and resilience.Methods: Many samples of the expanded polystyrene foam with different porosity and overall thickness values were prepared using a specific thermal procedure in a programmable oven. At first, the physical properties such as density and porosity of the expanded polystyrene foams were measured. Next, their microstructural characteristics such as the average cell wall thickness of the expanded polystyrene foams were investigated using a scanning electron microscope. The DIELECTRIC CONSTANT and loss factor of the samples were assessed with a vector network analyzer with a lens horn antenna. The mechanical properties of the expanded polystyrene foams were evaluated according to Shore D hardness, and the value of mechanical energy stored in them was measured by a resilience tester.Findings: By increasing cell wall thickness in samples at equal overall thickness, the DIELECTRIC characteristics such as DIELECTRIC CONSTANT and DIELECTRIC loss factor increase by 12% and 53%, respectively. Moreover, the mechanical properties such as hardness and resilience reveal an increase of 40 and 42%, respectively, due to the increase of cell wall thickness in samples at the same overall thickness. While the DIELECTRIC CONSTANT and the DIELECTRIC loss factor decrease with the reduction of the overall thickness at the same cell wall thickness, the variation of the overall thickness depicts no effect on the hardness and resilience.

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.