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Relative Permittivity (relative + permittivity)
Selected AbstractsPreparation and evaluation of composite electromagnetic wave absorbers made of aluminum fine particles dispersed in polystyrene mediumELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 1 2010Norizumi Asano Abstract We developed composite electromagnetic wave absorbers consisting of dispersed aluminum fine particles in a polystyrene medium and evaluated their properties in order to realize single-layer electromagnetic wave absorbers with good absorption in the gigahertz region. Polystyrene particles with two diameters (approximately 200 ,m and 1 ,m) and fine aluminum particles were mixed by mechanical milling. The mixture was heated above the melting point of polystyrene and then cooled naturally in air. The frequency characteristics of the complex relative permeability and the complex relative permittivity were calculated from the values of the scattering parameters of a coaxial line loaded with a sample of a toroidal-core shape. Both the diamagnetism and the magnetic loss increased in proportion to the volume mixing ratios of aluminum particles up to approximately 34 vol for samples made of polystyrene particles with approximately 200 ,m or 1,m diameter. The diamagnetism was almost frequency-independent and the magnetic loss decreased with increasing frequency for all samples. These results were in agreement with qualitative theoretical prediction. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 93(1): 30, 40, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10169 [source] An electromagnetic modelling tool for the detection of hydrocarbons in the subsoilGEOPHYSICAL PROSPECTING, Issue 2 2000Carcione Electromagnetic geophysical methods, such as ground-penetrating radar (GPR), have proved to be optimal tools for detecting and mapping near-surface contaminants. GPR has the capability of mapping the location of hydrocarbon pools on the basis of contrasts in the effective permittivity and conductivity of the subsoil. At radar frequencies (50 MHz to 1 GHz), hydrocarbons have a relative permittivity ranging from 2 to 30, compared with a permittivity for water of 80. Moreover, their conductivity ranges from zero to 10 mS/m, against values of 200 mS/m and more for salt water. These differences indicate that water/hydrocarbon interfaces in a porous medium are electromagnetically ,visible'. In order to quantify the hydrocarbon saturation we developed a model for the electromagnetic properties of a subsoil composed of sand and clay/silt, and partially saturated with air, water and hydrocarbon. A self-similar theory is used for the sandy component and a transversely isotropic constitutive equation for the shaly component, which is assumed to possess a laminated structure. The model is first verified with experimental data and then used to obtain the properties of soils partially saturated with methanol and aviation gasoline. Finally, a GPR forward-modelling method computes the radargrams of a typical hydrocarbon spill, illustrating the sensitivity of the technique to the type of pore-fluid. The model and the simulation algorithm provide an interpretation methodology to distinguish different pore-fluids and to quantify their degree of saturation. [source] Tape Casting and Dielectric Properties of Zn2Te3O8 -Based Ceramics with an Ultra-Low Sintering TemperatureINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2009Johanna Honkamo The suitability of dielectric ceramics made of zinc tellurate (Zn2Te3O8) and titanium dioxide (TiO2) with an ultra-low sintering temperature (650°C) for tape casting and thus for the multimodule technique with Al electrodes was investigated. The properties of the tape before and after sintering as well as the amount of organic additives for the casting process and a thermal analysis of the tape up to 1000°C are reported. In addition, electrodes on a multilayer module made on stacked tapes were prepared using Al paste and postfiring, followed by relative permittivity and loss tangent measurements to verify the electrical performance of the whole structure. The dielectric properties of the stacked module without any electrodes were also measured. The results show that the composition is well suited for the tape process but extra care should be taken especially with the proper sintering temperature for optimized electrical performance. [source] Solvent hydrogen bonding and structural effects on nucleophilic substitution reactions: Part 3.INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2007Reaction of benzenesulfonyl chloride with anilines in benzene/propan-2-ol mixtures Substitution reactions of 13 para- and meta-substituted anilines with benzenesulfonyl chloride in varying mole fractions of benzene in propan-2-ol have been investigated conductometrically. The second-order rate constants correlate well with pKa values of anilines and with the Hammett's equation. The negative Hammett reaction constant indicates the formation of an electron-deficient transition state. The rate data correlate satisfactorily with macroscopic solvent parameters such as relative permittivity, ,r, and polarity, ETN. Correlation of rate data with Kamlet,Taft solvatochromic parameters (,, ,, ,*) suggests that both the specific and nonspecific solute,solvent interactions influence the reactivity. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 657,663, 2007 [source] Kinetics and mechanism of oxidation of antimony(III) by keggin-type 12-tungstocobaltate(III) in aqueous hydrochloric acid mediumINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2003B. D. Bhosale The reaction between Sb(III) and [CoIIIW12O40]5, proceeds with two, one-electron steps; formation of unstable Sb(IV) is the slow first step followed by its reaction with another oxidant in a fast step. The reaction rate is unaffected by the [H+] as there are no protonation equlibria involved with both the reactants, whereas the accelerating effect of chloride ion is due to the formation of an active chlorocomplex of the reductant, SbCl63,. Increase in the ionic strength and decrease in the relative permittivity of the medium increases the rate of the reaction, which is attributed to the formation of an outer-sphere complex between the reactants. The activation parameters were also determined and these values support the proposed mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 9,14, 2003 [source] Accurate closed-form model for computation of conductor loss of coplanar waveguideINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2010Payal Majumdar Abstract This study estimates the accuracy of HFSS and Sonnet and other models against the experimental results from three sources. A closed-form model for experiment based stopping distance is developed to calculate accurately conductor loss of CPW. The present improved Holloway and Kuester (IHK) model has an average accuracy of 3.7% against the experimental results from different sources in the frequency range 1,120 GHz with conductor thickness of 0.25,1.58 ,m. The original Holloway and Kuester model has an average accuracy of 13.7% and model of Ponchak et al. 17.1 % against same set of experimental results. HFSS and Sonnet have average accuracy of 7.86% and 10.33% against same set of experimental data. The accuracy of IHK model is also examined against HFSS and Sonnet for the conductor thickness up to 9 ,m and substrate relative permittivity in the range of 3.8,20. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010. [source] Circular dichroism spectroscopic study of non-covalent interactions of poly- L -glutamic acid with a porphyrin derivative in aqueous solutionsJOURNAL OF PEPTIDE SCIENCE, Issue 9 2005Palivec Abstract The interactions of poly- L -glutamic acid and a cationic porphyrin derivative in aqueous solutions were studied by the combination of vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopies. It was found that non-covalent interactions between both agents influence the structure of the polymeric matrix and the guest porphyrins and vice versa, but the physico-chemical properties of the solutions, especially the pH and the relative permittivity of the solvent, play a key role in the structure of the polypeptide part of the formed complexes. It was shown that the interaction with porphyrins prevents the precipitation of poly- L -glutamic acid in aqueous solution at acidic pH. In special conditions, the porphyrins attached to the polypeptide probably possess face-to-face interaction as demonstrated by the enhancement of the characteristic ECD signal and the appearance of sidebands on its short and long wavelength sides. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source] Bilayered BiFe0.95Mn0.05O3/Bi0.90La0.10FeO3 Thin Films with Low Ferroelectric Coercivity and Large Remanent PolarizationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010Jiagang Wu Bilayered thin films consisting of (Bi0.90La0.10)FeO3 and Bi(Fe0.95Mn0.05)O3, i.e., Bi(Fe0.95Mn0.05)O3/(Bi0.90La0.10)FeO3, were deposited on SrRuO3 buffered SrTiO3(111) substrates by off-axis radio frequency magnetic sputtering, where (111)-oriented bilayered thin films were obtained. The bilayered Bi(Fe0.95Mn0.05)O3/(Bi0.90La0.10)FeO3 thin film possesses a lower coercive field (2Ec,335.6 kV/cm) and a larger remanent polarization (2Pr,155.2 ,C/cm2) at room temperature, and a higher relative permittivity as compared with those of single-layer (Bi0.90La0.10)FeO3 and Bi(Fe0.95Mn0.05)O3 thin films, together with an improvement of the magnetic properties (2Ms,31.2 emu/cm3). The bottom (Bi0.90La0.10)FeO3 nanolayer promotes the growth of the Bi(Fe0.95Mn0.05)O3 layer, which are largely responsible for the multiferroic behavior observed. [source] Microwave Dielectric Properties of SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Sherin Thomas The apatite type SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) ceramics have been prepared by the conventional solid-state ceramic route. The phase purity and surface morphology of the sintered ceramics were studied using X-ray diffraction and scanning electron microscopy methods. These materials showed poor sinterability and was improved by the addition of a small weight percentage of zinc borosilicate glass. The microwave dielectric properties of these materials were studied for the first time. SrRE4Si3O13 ceramics have a low relative permittivity (,r) in the range 9,16, a Q-factor (Qu×f) upto 26 000 GHz and a low temperature coefficient of resonant frequency (,f). The SrLa4Si3O13 ceramics possessed a high Qu×f of nearly 26 000 GHz but with a high negative ,f of ,46 ppm/°C. The ,f of SrLa4Si3O13 ceramics was tuned by the addition of suitable amount of TiO2. [source] Effect of BiScO3 and LiNbO3 on the Piezoelectric Properties of (Na0.5K0.5)NbO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Xueyi Sun Lead-free potassium sodium niobate-based piezoelectric ceramics (1,y)(Na0.5,0.5xK0.5,0.5xLix)NbO3,yBiScO3 ( y=0.01, x=0,0.06) have been prepared by an ordinary sintering process. The XRD analysis showed that the structure changes from orthorhombic to tetragonal with the increase of x (at y=0.01, abbreviated as KNNBSL100x). At room temperature, the polymorphic phase transition from the orthorhombic to the tetragonal phase was identified at approximately 0.02,x,0.04. The piezoelectric and ferroelectric properties were significantly enhanced. The temperature dependences of the relative permittivity revealed that the Curie temperature was increased with the addition of LiNbO3. These solid solution ceramics are promising as potential lead-free candidate materials. [source] Effect of Filler Content on the Dielectric Properties of PTFE/ZnAl2O4,TiO2 CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Sherin Thomas ZnAl2O4,TiO2 (ZAT)/polytetrafluoroethylene (PTFE) composites were prepared by powder processing method. The structure and microstructure of the composites were analyzed using X-ray diffraction and scanning electron microscopic techniques. The effect of different volume fraction of ZAT (0,0.6) on the dielectric properties of the composites was investigated at 1 MHz and at the microwave frequency of 7 GHz. The dielectric properties (relative permittivity and dielectric loss) were found to increase with the ZAT content. The samples with 60 vol.% of ZAT filler showed a relative permittivity of 3.9 and dielectric loss of 0.009, respectively, at 7 GHz. The variation of relative permittivity and dielectric loss showed only a very small variation with temperature in the range 25°,70°C for various ZAT/PTFE composites. The relative permittivity obtained experimentally were compared with that of the theoretical values predicted using modified Lichtenecker, Jayasundere,Smith, and Series mixing formulae. They were found to agree well with the predicted values for low filler content. [source] A-Site and B-Site Order in (Na1/2La1/2)(Mg1/3Nb2/3)O3 PerovskiteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2004Rachel Tarvin (Na1/2La1/2)(Mg1/3Nb2/3)O3 undergoes a series of phase transitions that involve cation order on the A- and B-sites of the parent perovskite structure. At high temperatures both sites contain a random distribution of cations; below 1275°C a ,111, layering of Mg and Nb leads to the formation of a 1:2 ordered structure with a monoclinic supercell. A second transition was observed at 925°C, where the Na and La cations order onto alternate A-site positions along the ,001, direction of the parent subcell. By quenching samples from above 1275°C to preserve the disorder on the B-site, a fourth variant of this compound was obtained by inducing A-site order through a subsequent anneal at 900°C. Although the changes in structure do not produce significant alterations in the relative permittivity (,r, 35), they do have a significant effect on the value of the temperature coefficient of the capacitance. [source] Rapid Prototyping of Piezoelectric Ceramics via Selective Laser Sintering and GelcastingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004Dong Guo This article presents a new lost mold rapid prototyping method which combines selective laser sintering (SLS) and gelcasting techniques for fabricating piezoelectric ceramics. SLS was used to fabricate sacrificial molds of the desired structure of the ceramic part. Then aqueous PZT (lead zirconate titanate) suspension was cast in the mold and solidified in situ through formation of a three-dimensional network gel. Because the polymer mold can be easily removed at the initial stage of sintering and the gelcast PZT body has a high green strength, the desired geometry of the PZT part can be completely retained after sintering of the ceramics. Complex-shaped PZT parts were successfully fabricated after using concentrated PZT suspension with low viscosity. Densities and electrical properties, such as the d33, the relative permittivity ,, the dielectric loss tg, and the electromechanical coupling factor Kp of the gelcast PZT parts were also compared with those of the die-pressed PZT samples. The results indicated that the gel-forming process did not deteriorate the electrical properties of the samples, if proper dispersant was selected in developing concentrated ceramic slurry. [source] Broadband planar DTV antenna in the portable media player held by the user's handsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2007Wei-Yu Li Abstract Effects of the user's hands on the broadband planar DTV antenna in the portable media player (PMP) are studied. The antenna has a wide operating bandwidth covering the 470,806 MHz band for DTV signal reception and a one-layer equivalent simulation hand model including the user's forearm with a relative permittivity of 33.5 and a conductivity of 0.47 S/m is used for the simulation study. Three different conditions of the user's hands (right hand only, left hand only, and both hands) holding the PMP are studied, and their effects on the return loss, radiation efficiency, and radiation patterns of the studied DTV antenna are analyzed. In addition, effects of the user's hands holding the PMP at different positions relative to the studied DTV antenna are analyzed. Results have shown that, for the worst case, the radiation efficiency of the studied DTV antenna is still larger than 60% over the operating band, making the antenna very promising for practical applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1841,1844, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22639 [source] A conical-pattern annular-ring microstrip antenna with a photonic bandgap ground planeMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2001Shun-Yun Lin Abstract A probe-fed annular-ring microstrip antenna with a photonic bandgap (PBG) ground plane operating in the higher order mode of TM21 for conical-pattern radiation is experimentally demonstrated. The antenna studied is printed on a thin FR4 substrate (relative permittivity 4.4) and, owing to the PBG ground plane used, significant improvements in the antenna performances are observed. The obtained impedance bandwidth is doubled, and the antenna gain is enhanced by about 7 dBi. Details of the experimental results are presented and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 159,161, 2001. [source] Influence of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3-, filler on the microwave dielectric properties of polyethylene and polystyrene for microelectronic applicationsPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Sumesh George Ceramic reinforced polyethylene and polystyrene composites were prepared by melt mixing and hot molding techniques. Temperature stable low-loss Ca[(Li1/3Nb2/3)0.8Ti0.2]O3-, (CLNT) ceramic was used as the filler to improve the dielectric properties of the polymers. The relative permittivity and dielectric loss in the microwave frequency range were increased with increase in the ceramic loading. As the filler content increased from 0 to 0.50 volume fraction, the relative permittivity increased from 2.3 to 9 and dielectric loss tangent from 0.0006 to 0.005 for polyethylene-CLNT composite. In the case of polystyrene-CLNT composite, the relative permittivity and dielectric loss tangent increased from 2.1 to 10.5 and 0.0005 to 0.0032 respectively with increase in filler content from 0 to 0.50 volume fractions. The thermal stability of the relative permittivity of polymer ceramic composites was also investigated. The experimentally observed relative permittivity was compared with theoretical models. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Ground-penetrating radar survey over bronze age circular monuments on a sandy soil, complemented with electromagnetic induction and fluxgate gradiometer dataARCHAEOLOGICAL PROSPECTION, Issue 3 2009L. Verdonck Abstract This paper presents a ground-penetrating radar (GPR) survey over two circular structures originally surrounding Bronze Age burial mounds at the site of Koekelare (western Belgium). The region is characterized by sandy soils. Their low water storage capacity and the consequent moisture contrasts in dry summers played an important role in the detection of over 1000 Bronze Age funeral monuments through aerial archaeology in the past few decades. At Koekelare, low attenuation of GPR waves resulted in the detection of a double and single circular ditch. A fluxgate gradiometer survey and electromagnetic induction (EMI) measurements did not clearly reveal the ditches. For the GPR wave velocity analysis, constant velocity migration tests were combined with time-domain reflectometry (TDR). The TDR measurements were made at different depths within the ditches and in the adjacent undisturbed soil, so that the differences in the physical soil parameters could be assessed. At a depth of approximately 0.45 to 0.8,m, the relatively homogeneous ditch fill produces few GPR reflections compared with the undisturbed soil, and is visible as a weak negative anomaly on the horizontal slices. At this depth, the grey or brownish black ditch fill was found in augering samples, clearly distinguishable from the yellowish brown sandy soil outside the ditches. The transition between the ditch and the underlying soil caused a gradual reflection of radar energy at a depth of approximately 0.8 to 1.2,m, although TDR showed no marked differences in relative permittivity between the ditches and the surrounding soil, and no clear steps as a function of depth. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||