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DIELECTRIC CONSTANT OBTAINED FROM TDR AND VOLUMETRIC MOISTURE OF SOILS IN SOUTHERN BRAZIL

DIELECTRIC CONSTANT OBTAINED FROM TDR AND VOLUMETRIC MOISTURE OF SOILS IN SOUTHERN BRAZIL

The result of the adjustments of the equations proposed by Topp et al. (1980) and Ledieu et al. (1986) considering the soils studied is presented in figure 2. Both equations overestimated the values of volumetric moisture for the Hapludox (Campos Novos – SC) and there was an underestimation of lower moisture values in the Hapludox (Passo Fundo – RS). Thus, these equations, which are considered universal and are used in the algorithms of the TDR devices, may not be generalized for all soil classes, especiallly for tropical soils that present a wide variation in their mineralogical composition (Tomaselli & Bacchi, 2001). Adjustment of the linear and polynomial models to the entire set of data did not lead to improvements in the soil moisture estimates from the dielectric constant measured by the TDR (Figure 3). The cubic polynomial model had the best adjustment (R 2 = 0.80),
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Microstrip antenna on a high dielectric constant substrate: BaTiO3 (BTO)CaCu3Ti4O12(CCTO) composite screenprinted thick films

Microstrip antenna on a high dielectric constant substrate: BaTiO3 (BTO)CaCu3Ti4O12(CCTO) composite screenprinted thick films

dielectric constants have been found showing a dielectric constant at 1 kHz of ;10,000 that is nearly constant from room temperature to 300°C. Oxides with the perovskite structure are well stabilized by their high dielectric constants (K), which lead this class of materials to be used in a large number of technological applications. 15 However, this behavior is generally associated with ferroelectric or relaxor properties. In these cases, the highest value of K is obtained during a phase transition (as a function of temperature) presented by the material.

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Retrieval of the thickness of undeformed sea ice from simulated C-band compact polarimetric SAR images

Retrieval of the thickness of undeformed sea ice from simulated C-band compact polarimetric SAR images

Abstract. In this paper we introduce a parameter for the re- trieval of the thickness of undeformed first-year sea ice that is specifically adapted to compact polarimetric (CP) syn- thetic aperture radar (SAR) images. The parameter is de- noted as the “CP ratio”. In model simulations we investigated the sensitivity of the CP ratio to the dielectric constant, ice thickness, ice surface roughness, and radar incidence angle. From the results of the simulations we deduced optimal sea ice conditions and radar incidence angles for the ice thick- ness retrieval. C-band SAR data acquired over the Labrador Sea in circular transmit and linear receive (CTLR) mode were generated from RADARSAT-2 quad-polarization im- ages. In comparison with results from helicopter-borne mea- surements, we tested different empirical equations for the re- trieval of ice thickness. An exponential fit between the CP ra- tio and ice thickness provides the most reliable results. Based on a validation using other compact polarimetric SAR im- ages from the same region, we found a root mean square (rms) error of 8 cm and a maximum correlation coefficient of 0.94 for the retrieval procedure when applying it to level ice between 0.1 and 0.8 m thick.
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Mat. Res.  vol.18 número5

Mat. Res. vol.18 número5

of the dielectric constant increases with an increase in the temperatures. The huge value of the dielectric constant at low frequencies can be attributed to the lower electrostatic binding strength, arising due to the space charge polarization near the grain boundary interfaces. Owing to the application of an electric ield, the space charges are stimulated and dipole moments are produced and are called space-charge polarization. This apart, these dipole moments are rotated by the ield applied ensuing in rotation polarization which also contributes to the high values. Whenever there is an increase in the temperature, more dipoles are produced and the value increases 26 . In the high frequency region, the charge
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STRUCTURAL AND DIELECTRIC STUDIES ON Sr0.5-3y/2LayBa0.5Nb2O6 CERAMIC SYSTEMS WITH VARIED SINTERING TIME AND La CONCENTRATION

STRUCTURAL AND DIELECTRIC STUDIES ON Sr0.5-3y/2LayBa0.5Nb2O6 CERAMIC SYSTEMS WITH VARIED SINTERING TIME AND La CONCENTRATION

The frequency and temperature dependence of the dielectric constant for La doped SBN from are shown in Figure 9a and b respectively. As the concentration of the La increased the dielectric constant increased except for 7 % (see Figure 9a). In fact, at 7 % doped La, the dielectric constant signiicantly decreased to lower than 1 % La doped dielectric constant value. The observation matches well with the XRD pattern where the intensity of the spectra decreased indicating the crystallinity of the 7 % La doped ceramic decreased. The solubility limit of La 3+ in the SBN solid solution seems to be at ~ 5 % La
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BRAZILIAN ARCHIVES OF BIOLOGY AND TECHNOLOGY

BRAZILIAN ARCHIVES OF BIOLOGY AND TECHNOLOGY

attracting molecules, r = distance of two attracting molecules. All solvents have its own dielectric constant, organic solvents posses lower dielectric constantthan inorganic solvents, so water possesses higher dielectric constant than organic solvents, therefore from the above theory it can be concluded that force of interaction between amylase and solvent may have increased due to lowered dielectric constant of the extracting solvent, glycerol. Though other organic solvent posses lower dielectric constant than glycerol they may have some inhibitory effect on enzyme activity
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Braz. J. Phys.  vol.34 número1

Braz. J. Phys. vol.34 número1

Before discussing the solvent effects on the conformational equilibrium of furfural, it is interesting to mention that this molecule may exist in two possible conformations: OO-cis and OO-trans (Fig. 1). The OO-trans form is known to be more stable in the vapour, whereas the OO-cis form is more stable in polar media [18]. Recently, Baldridge et al. [12] showed that the conformer with larger dipole moment, OO- cis, prevails in solvents with dielectric constants higher than 5. However, the stability between both conformers does not obey a simple relationship with the dielectric constant [28]. This, of course, indicates that the solvent effects are more complex than could be inferred by a simple reaction field. The solvent dependence of the activation barrier for the cis- trans interconversion of furfural is really an important topic in biophysical chemistry.
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Synthesis of Cerium Dioxide High-k Thin Films as a Gate Dielectric in MOS Capacitor

Synthesis of Cerium Dioxide High-k Thin Films as a Gate Dielectric in MOS Capacitor

high dielectric constant (high-k) oxides in order to over- come the gate delay and other related issues [1-3]. It is clear from the development of high-k materials that only replacing the gate insulator may not be sufficient for device scaling. Hence, the research is focused on developing the novel high-k / metal gate (HK/MG) stacks in order to enhance the performance of the de- vices. The poly depletion effects and the V t pinning at

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Cerâmica  vol.58 número345

Cerâmica vol.58 número345

Conventionally ferrites are used phase shifter in microwave-tuned circuits for the construction of phased array antennas. But these materials are costly and devices made from them are bulky. Therefore for the purpose of miniaturization as well as for making light weight devices with improved features a better dielectric material is needed. The material should be associated with relatively lower value of dielectric constant to minimize the overall impedance mismatch. Again to lower the insertion loss a low value of loss factor is also required for these materials.
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Mat. Res.  vol.20 número2

Mat. Res. vol.20 número2

the dielectric constant showed a decreasing tendency with doping content and with increasing frequency for pseudo- cubic nanometric barium titanate doped with gadolinium (Gd 3+ ) where[r]

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Study on Optical Constants and Refractive Index Dispersion of Neutral red Doped Polymer Film

Study on Optical Constants and Refractive Index Dispersion of Neutral red Doped Polymer Film

The investigation of the optical constants such as refractive index, extinction coefficient and dielectric constant of the 3- amino-7-dimethylamino-2-methyl phenazine doped polymer film are important for designing of new materials. Optical constants include the valuable information for technological applications. Furthermore, the changes in refractive index are important for controlling optical properties of thin polymer. Optical properties of any organic thin films are important for optical applications, because optical properties are directly related to their structural and electronic properties. The main aim of this study is to investigate the optical properties of polymer thin film
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A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils

A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils

The soil drying procedure consists on placing the structure shown in Figure 4 in the climate chamber, which was scheduled to reach 50 ± 1 °C for three hours and go back to 25 ± 1 °C for five hours, until the soil gets quite dry, and its weight practically stops changing. After this test, the soil moisture content by weight using a standard oven method for each measuring point is obtained. Finally, a correlation model between dielectric constant of the soil and the soil water content is fitted using linear regression.

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Electrical characterization of in situ polymerized polyaniline thin films

Electrical characterization of in situ polymerized polyaniline thin films

Dyre’s Eq.(1) supplemented by a doping level dependent contribution, Eq.(5), were used to explain our results in in situ doped polyaniline thin films. The increase in conductivity was explained by the increase of the hoping sites afforded by dop- ing. As results, it is obtained not only the dielectric constant as function of doping level, but also the activation energy for hop- ping carriers below and above the possible glass transition of the material around 227 K.

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art fnafreire DIELECTRIC

art fnafreire DIELECTRIC

and theoretical characteristics of the antenna like return loss, band- width, input impedance, and radiation patterns are in good agreement. Numerical validation is done, tacking into account the air gaps between the dielectric resonator and the metallic conductors. Frequency re- sponse bandwidth in the range of 6.6 –11.8% was obtained for fre- quency operation around 4 GHz. The CRFO-FCTO present a dielectric constant in the range of 8 –13 with loss around 10 ⫺3 . To summarize, the performance of a cylindrical DRA based in a new matrix CRFO/FCTO was examined. These measurements confirm the potential use of such materials for small DRA. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 409 – 413, 2007; Published online in Wiley Inter- Science (www.interscience.wiley.com). DOI 10.1002/mop.22160
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Dielectric and electrical properties of a mulliteglass composite from a kaolinite claymica-rich kaolin waste mixture (Propriedades dielétricas e elétricas de compósito mulitafase vítrea obtido a partir de uma mistura argila cauliníticaresíduo de caulim)

Dielectric and electrical properties of a mulliteglass composite from a kaolinite claymica-rich kaolin waste mixture (Propriedades dielétricas e elétricas de compósito mulitafase vítrea obtido a partir de uma mistura argila cauliníticaresíduo de caulim)

It was expected since at lower frequencies the dielectric pattern may be attributed to different types of polarization (ionic, electronic, atomic, interfacial, etc.), while at higher frequencies it only arises due to the contribution from electronic polarization [29, 30]. The measured dielectric constant at 1 MHz agreed with previous results for mullite-based ceramics [14, 15]. The energy dissipation in the dielectric system, which is well-known as dielectric loss (tanδ), also decreased with increasing frequency (Fig. 5b). The value of 0.024 found at 1 MHz was considered to be good for electronics-related applications (tanδ<0.04) [15]. A further investigation on the electrical and dielectric properties of mullite-based ceramics as a function of the kaolin waste content (from 0 to 100 wt%) is the topic of forthcoming work.
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art aflalmeida dielectric permittivity

art aflalmeida dielectric permittivity

ceramic were studied by X-ray powder diffraction, infrared and Raman scattering spectroscopy. After 30 h of milling the formation of CCTO was con®rmed by X- ray powder diffraction. The infrared and Raman scattering spectroscopy con®rm the formation of the CCTO phase as seen by X-ray diffraction analysis. For one experimentalprocedure one uses an organic binder in the process of shaping the samples. In the second procedure the samples were prepared without the presence of the organic phase. For the second situation we had higher dielectric constant e … r ˆ 7370 † with high loss …D ˆ 0.2† at 1 KHz. For the ®rst procedure one has the lower dielectric constant e … r ˆ 1530 † and lower loss …D ˆ 0.11† at 1 KHz. Rectangular antenna prototypes were also designed on substrate samples (C1, C2, P1 and P2). For the antennas (with P2, C1 and C2 as substrates), the bandwidth (BW) is 90 MHz (around 3%). The antenna with P1 substrate presented a surprisingly high BW of 270 MHz that corresponds to a 10% bandwidth at 3 GHz. Such value is in accordance with the require- ments for planar antennas for a variety of wireless communication systems such as WLAN, PCS, Wi±Fi and other protocols.
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art fnafreire chitosan

art fnafreire chitosan

With the increase of the frequency one has a strong decrease of the dielectric constant for all the composites. For frequencies around 1 MHz, all the composites present values of the dielectric constant below the value of the ceramic sample BITC (K ⫽ 159). The observed loss of the composite ferroelectric films could be useful for polarized bandages, promoting fast blood coagulation. In Fig. 8, the dielectric loss is shown as function of frequency. In Table 2, the BITC bulk dielectric constant is also presented for comparison.

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of dielectric properties of screenprinted MgTiO3–CaTiO3 composite thick films in the microwave frequency range

of dielectric properties of screenprinted MgTiO3–CaTiO3 composite thick films in the microwave frequency range

The dielectric properties of MTO, CTO and MTO(x)– CTO(1-x) composite screen-printed thick films at room temperature were measured in the frequency range from 50 MHz to 20 GHz using the coplanar waveguide (CPW) resonator method described in [12]. In this characterization technique, a CPW resonator coated with a deposited high dielectric constant film presents a displacement of the resonance frequency peaks towards lower frequencies when compared to an identical resonator without film (a reference resonator). Once the thickness of the film and the fundamental peak frequency of the film-coated resonator (measured with a network analyzer) are known, the film dielectric constant can be obtained through interpolation among a set of curves simulated for CPW resonators with the same dimensions and different values for film dielectric constant and thickness. The
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J. Microw. Optoelectron. Electromagn. Appl.  vol.16 número3

J. Microw. Optoelectron. Electromagn. Appl. vol.16 número3

The second step is the substrate characterization in order to get accurate values for dielectric constant and loss tangent. In this case we demonstrated that we can measure them by using only 1- port measurement and low cost equipment, while traditional methods uses 2 port measurements and VNAs. Finally, we designed a LDMOS power amplifier by using loadpull data, in a RF35 substrate previously characterized. By using symmetrical bias networks and lumped/discrete element combinations for the matching networks, we demonstrated that we can reach the appropriate impedances and satisfy the power and gain specs.
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Mat. Res.  vol.7 número4

Mat. Res. vol.7 número4

This work exploits the Newton’s Iterative Complex Method together with the Transmission/Reflection Method to measure the dielectric constant of a gypsum sample with 45% moisture on the L and C microwave ranges. The initial estimation to calculate the dielectric constant is different from the usual one described in the recent literature. This procedure was mentioned in a recent work by the authors of reference 6 . The technique applied is presented in the next

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