Relative permittivity

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Seasonal Variation and Age-related Changes in the Relative Permittivity of Concrete Bridge Decks on Korea Expressways

Seasonal Variation and Age-related Changes in the Relative Permittivity of Concrete Bridge Decks on Korea Expressways

permittivity value than that of solid concrete in wet or dry, respectively, condition. For comparison, a concrete condition map based on the depth-corrected attenuation of GPR signals reflected from the upper layer of rebar is shown in Fig. 14c. In the sound concrete, the attenuation of radar waves is generally pro- portional to the depth of the rebar, detailing the two way travel time. For JB-3N and 3S, it was assumed that 50% of the concrete was sound and the critical value of the depth corrected attenuation was - 3 dB (Rhee et al. 2016). Table 4 summarizes the estimated damaged areas of each of the spans based on the condition maps obtained from the three different GPR analysis methods (i.e., single- and dual cut-off relative permittivity and depth-corrected attenuation criteria). In addition, the damaged areas of each span were calculated according to the ‘Inspection manual for the bridge (Minister of Land Infrastructure and Transport, Korea Infrastructure Safety and Technology Corporation 2012)’. Figure 14 shows some disagreements between the attenua- tion and relative permittivity analyses. The discrepancy stems from the fact that the relative permittivity value
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An extended mode-matching model for improved relative permittivity measurements using a split-cylinder resonator

An extended mode-matching model for improved relative permittivity measurements using a split-cylinder resonator

(2004) by improving mode identification and enabling dis- tortion analysis of resonant modes due to coupling and over- lapping. Additionally a better frequency range coverage for relative permittivity estimation has been reached. The new model was verified by analyzing measured spectra of several substrate materials. Although our model does not consider the fringing fields in the gap region a comparison of relative permittivity estimation results for the T E 0np modes showed

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Material-Loaded High Q-Factor Slot Resonator and Measurement of Relative Permittivity

Material-Loaded High Q-Factor Slot Resonator and Measurement of Relative Permittivity

The simulated resonance frequency is 4 GHz; while the measured one is 4.016 GHz. The measured relative permittivity is calculated from Equation (3). The manufacturer’s relative permittivity is 3.38; whereas the measured one is 3.34. The uncertainty of measurement of the dielectric constant is only 0.04 which gives an error of only 1.18%. It is in same range as provided by other complex measurement methods [11]. It is worth to mention that the resonator should be ready to characterize any other complex structure as long as it is embedded between the two metallic plates to form a simple capacitor. However, in order to improve the accuracy of the device, we have to fabricate the resonator carefully and the material inside the resonator has be placed carefully.
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Estimation of Relative Permittivity of Shallow Soils by Using the Ground Penetrating Radar Response from Different Buried Targets

Estimation of Relative Permittivity of Shallow Soils by Using the Ground Penetrating Radar Response from Different Buried Targets

The estimation of time of flight (TOF) has been done according to an electromagnetic model of the experiment. In a first approximation we can assume the radar operates in a monostatic mode at height h from the surface of the soil and the target as a point-like reflector. The ray path descriptions for the time-of flight calculations are shown in Figure 1. As the soil relative permittivity is unknown, the point y B

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Evaluation of the Depth of Deteriorations in Concrete Bridge Decks with Asphalt Overlays Using Air-Coupled GPR: A Case Study from a Pilot Bridge on Korean Expressway

Evaluation of the Depth of Deteriorations in Concrete Bridge Decks with Asphalt Overlays Using Air-Coupled GPR: A Case Study from a Pilot Bridge on Korean Expressway

Figure  15 illustrates the relationship of the depth-cor- rected attenuation of concrete cover against the relative permittivity of concrete on the top surface of the bridge decks. Overall, the depth-corrected attenuation tends to increase as the relative permittivity of concrete increases. However, numerous data points are far from the best- fit line of the two GPR parameters, which is shown as a red solid line in Fig.  15. This deviation is due to the two GPR parameters that are based on different fundamental principles, physical significance, and properties (Table 5). Relative permittivity is computed by the amplitude of the received EM wave reflected from the interface of a medium. The EM wave is emitted and is mainly a factor to indicate the water content ratio at the concrete surface in a bridge deck (A/C interface). On the other hand, the depth-corrected attenuation is computed by excluding the attenuation due to distance (geometric and dielectric loss) from the attenuation (loss) of the EM wave trans- mitted to a medium. This is a factor to evaluate the con- ductivity of the chloride ion in the concrete cover. It has been demonstrated from the 20 years experience of GPR field applications in KEC that the single-parameter-based (the relative permittivity or depth corrected attenuation) GPR survey is not enough to evaluate the deteriorated depth of concrete on the basis of accuracy.
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Effect of pore conformation on dielectric anisotropy of oven-dry wood evaluated using terahertz time-domain spectroscopy and eigenvalue problems for two-dimensional photonic crystals

Effect of pore conformation on dielectric anisotropy of oven-dry wood evaluated using terahertz time-domain spectroscopy and eigenvalue problems for two-dimensional photonic crystals

This study was performed to clarify the effect of pore conformation on the dielectric anisotropy of wood. The relative permittivity along the longitudinal and tangential axes of oven-dry flat-sawn specimens prepared from 12 different wood species was measured at a frequency of 0.15 THz using a transmission measurement system for terahertz time-domain spectroscopy (THz-TDS). Addi- tionally, the relative permittivity was calculated by solving the eigenvalue problems for wood specimens by regarding them as 2D photonic crystals. Ultimately, the dielectric anisotropy of wood was obtained from the measured and calculated relative permittivities. The relations of two kinds of anisotropy to wood density were compared and analyzed based on the pore arrangement observed using a scanning electron microscope (SEM).
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Dielectric properties of deformed early potatoes

Dielectric properties of deformed early potatoes

The resultant irreversible effect of the deforma- tion cycle was determined by the relative difference of the calculated quantities in both maxima (left and right). The effects are plotted in Figure 7: the real part of the relative permittivity in Figure 7a, the imaginary part of the relative permittivity in Fi- gure 7 b, and the loss angle in Figure 7c. The results are very variable even if they differ by less than only few percent. The results do not have the same sign, thus positive and negative values were observed in different parts of the spectrum. Most data for “the effect” in the real part of the real permittivity are negative, but also in this case some positive values were observed at higher frequencies, especially in the case of the early potatoes. Figure 7a indicates that the real part of permittivity decreased a little in most cases (especially in the late varieties), but this decrease is not the same over the whole fre- quency range and in some cases, especially at high frequencies, the real part of permittivity increased. Figure 7b indicates that the imaginary part of per- mittivity increased during the loading/unloading test at lower frequencies (lower than approximately 10 kHz) whereas at higher frequencies it rather de- crease. The loss angle rather increased during the loading/unloading test, especially at the medium frequencies of 1–100 kHz. Outside this frequency range, the effect was either very low and/or oppo- site. The effect of variety is visible in this case but it is not yet clear.
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Applicability of effective medium theory to wood density measurements using terahertz time-domain spectroscopy

Applicability of effective medium theory to wood density measurements using terahertz time-domain spectroscopy

To examine the applicability of an effective medium theory to the evaluation of wood density in the terahertz frequency range, the complex permittivity along the longitudinal axis of flat-sawn oven-dry specimens of 11 wood species was measured in a frequency range of 0.15–1.2 THz using a transmission measurement system for THz-TDS. The effective medium theory explained the density dependence of relative permittivity for the entire frequency range, but did not explain that of the dielectric loss for a higher fre- quency range. This indicates that the terahertz waves are more scattered at higher frequencies. It was concluded from the dielectric loss spectrum of wood substance that a fre- quency of approximately 0.23 THz is preferable for the NDE, since a high gain of the detected signals was obtained. A quantitative evaluation of the effect of the scattering on the dielectric loss should be examined in the future. Acknowledgments The authors would like to express their grati- tude to Motoki Imamura and Akiyoshi Irisawa (Advantest Corpora- tion, Japan) for their technical support.
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Wave Interaction With Epsilon-znd-Mu-Near-Zero (emnz) Platforms and Nonreciprocal Metastructures

Wave Interaction With Epsilon-znd-Mu-Near-Zero (emnz) Platforms and Nonreciprocal Metastructures

TE wave. It is shown that for that polarization we get a non-zero scattering only for the n = 0 component of the scattered field when the relative permittivity and permeability are near zero (but not strictly zero), as expected. Moreover, the interesting property of PEC objects introducing no scattering being illuminated by a TM wave when embedded in an EMNZ medium still holds regardless of how arbitrarily shaped the EMNZ region and the conducting object are, owing to the ability of EMNZ media to open up the space as discussed before. This is depicted clearly in Fig. 2(c), where a physically large-cross- section 2D PEC cylinder of an arbitrary shape is embedded into the EMNZ bounded region with another arbitrary shape connected to two air-filled parallel-plate waveguides, shown in Fig. 1(b), providing no scattering at all, with unity transmission and almost no phase progression as the wave traverses the EMNZ region containing this cylinder. (As in Fig. 1, the external boundary (except for the input and output ports) is made of PEC wall. The two parallel-plate waveguides connected to the 2D EMNZ region are filled with air). The numerical results shown in Figs. 1 and 2 were achieved using the RF module of the finite-element-method commercial software COMSOL Multiphysics®, using triangular meshing of maximum element size λ 0 / 30 , where λ 0 is the operating wavelength in free
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Characterization of an In-house Built 50 Hz Single Dielectric Barrier Discharge System Having Asymmetric Electrodes

Characterization of an In-house Built 50 Hz Single Dielectric Barrier Discharge System Having Asymmetric Electrodes

The variational trend of both discharge power and transported charge with a rise in applied voltage and dielectric barrier thickness is shown in Fig. 4 & 5. The inter electrode gap was kept constant at 1mm and corresponding response of discharge power and transported charge is observed. For all cases in Fig. 4a & 4b, it can be noted that both plasma parameters have proportional relation with rising ac input voltage which is in good agreement with the results reported by Kim and Abdel-Salam [15, 16]. Where in Fig. 5a & 5b, there is an inverse but non-linear relationship between the discharge plasma parameters and dielectric barrier thickness. It means, thicker the dielectric barrier is, lower will be the discharge power and transported charge. Furthermore, it is found that discharge power and transported charge for glass as dielectric barrier are higher than those for quartz due to higher relative permittivity and capacitance as shown in Table I.
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Temperature-stable dielectric properties from -20°C to 430°C in the system BaTiO3-Bi(Mg0.5Zr0.5)O3

Temperature-stable dielectric properties from -20°C to 430°C in the system BaTiO3-Bi(Mg0.5Zr0.5)O3

suppression of thermally induced changes to the total volume of polar regions as a consequence of the highly defective crystal lattice. These temperature stable relaxor dielectrics are of interest for new types of high volumetric efficiency capacitors operating at > 200 ºC for use in electronic systems for aviation, automotive and deep-well drilling applications [12]. Temperature stability, defined here as a variation in relative permittivity of within ±15% (consistent with the EIA classification system ‘R’) , occurs at higher temperatures than for traditional BaTiO 3 based dielectrics such as X7R which is specified at
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Suspended Rectangular Microstrip Antenna with Rectangular Slit

Suspended Rectangular Microstrip Antenna with Rectangular Slit

ABSTRACT: A major disadvantage of the micro strip-patch antenna is its inherently narrow impedance bandwidth of only a couple of per cent. Intensive research is going on to develop bandwidth-enhancement techniques by keeping its size as small as possible. In this paper a suspended rectangular microstrip antenna with rectangular slit (SRMSARS) is presented. Obtained bandwidth is 15.71% & 50.50% respectively with respect to center frequency. The substrate material of FR-4 with relative permittivity 4.4 and loss tangent of 0.0245 is used in this proposed antenna. The return loss and radiation pattern have been measured by using Vector Network Analyser.
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ASSESSMENT OF WATER CONTENT FOR SUB-PAVEMENT LAYERS USING GPR.

ASSESSMENT OF WATER CONTENT FOR SUB-PAVEMENT LAYERS USING GPR.

The relative permittivity of base and sub-base layers in each section were estimated by calculating the electromagnetic wave velocity between the surface and the buried reflectors (steel plates). The velocity from the surface to the buried reflectors was calculated by measuring the two way time. The two way time is the interval in which energy travels vertically from the ground surface to the buried reflector and back, and it occurs when the GPR apparatus is directly over the center of the reflector (Grote el at., 2002). After measuring the two way time (twt), the electromagnetic waves velocity was calculated by using the following formula:
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ESTIMATION AND CHARACTERISTIC OF THE EFFECTIVE DIELECTRIC CONSTANT OF MICROSTRIP LINE USING QUASI STATIC ANALYSIS

ESTIMATION AND CHARACTERISTIC OF THE EFFECTIVE DIELECTRIC CONSTANT OF MICROSTRIP LINE USING QUASI STATIC ANALYSIS

Form the above mention formula, the condition arises R × C = L × G for distortion less transmission line. Since there is no wires or long conducting element L and G cannot be changed so it is very evident from the above condition that only R and C can be inversely proportional to each other as C is dependent on relative permittivity and R can be treated as characteristic impedance it can be knuckled with the fact that whenever C Increases R decreases.

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Dielectric properties of papaya seeds from 75 kHz to 5 MHz

Dielectric properties of papaya seeds from 75 kHz to 5 MHz

Moura et al. (2013) emphasized the importance of the on-line moisture content sensors installed in the storage environment that would function as a method of quality control of the product in storage, without the need to destroy the samples, as is the case with the oven drying method. The on-line moisture content meters of granular agricultu- ral materials are classified as indirect measurement meth- ods because they are based on physical properties that can be correlated with the volumetric concentration of water in the seed sample. Currently, meters that use dielectric properties as parameters for estimating the moisture con- tent are the most widely studied. According to Trabelsi et al. (2013), it is necessary to analyse in detail the relative permittivity (ε’) and the loss factor (ε”) as a function of frequency, along with bulk density (ρ) and the temperature of seed samples contained inside the capacitive sensors to correlate dielectric properties with the seed moisture con- tent. This procedure predicts which frequencies and ranges of the moisture content and bulk density may integrate dielectric models that shall be incorporated into electronic measurement systems. Therefore, in order to determine the moisture content with accuracy, the effects of both bulk density and temperature must be made explicit through additional measurements and compensation, or eliminat- ed by the identification of functions that are independent of bulk density and insensitive to temperature variations (Trabelsi et al., 2013).
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Dielectric Behaviour of Pure and Dye Doped Nematic Liquid Crystal BKS/B07

Dielectric Behaviour of Pure and Dye Doped Nematic Liquid Crystal BKS/B07

The variation of real and imaginary parts of relative per- mittivity, that is dielectric constant () and dielectric loss () for pure nematic sample BKS/B07 and two dye mixed samples with log of frequency are shown in Fig- ures 3 and 4 respectively. The variation of real and imaginary parts of relative permittivity that is dielectric constant () and dielectric loss () for pure nematic sample BKS/B07 and with two dyes anthraquinone (mixture 1) and rhodamine B (mixture 2) with tempera- ture are shown in figures 5 and 6 respectively. Figure 7 shows the variation of percentage optical transmittance with temperature for pure nematic sample BKS/B07 and two dye mixed samples (mixture 1 and 2). Textures of the nematic sample BKS/B07 along with its two guest-host mixtures in crystalline and nematic phases have been presented in Figures 8 to 9.
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Effective complex permittivity of a weakly ionized vegetation litter fire at microwave frequencies

Effective complex permittivity of a weakly ionized vegetation litter fire at microwave frequencies

Mphale et al [19] have carried out a microwave propagation test in a moderate intensity pine litter fire using a network analyser. Using attenuation coefficients determined from S-parameters [19], graphically deduced momentum transfer electron-neutral particle collision frequency and electron density in the fire combustion. The method used to determine the electromagnetic constitutive parameters for the fire was rather crude. However, a slightly more accurate method would be to determine these parameters from network analyser measured complex relative dielectric permittivity for the combustion zone. Collision frequency and electron density are then determined from the real and imaginary parts of complex relative permittivity. Another advantage of the current method is that other flame constitutive parameters such as conductivity could be determined from these components. In the current work, microwave propagation coefficients for a vegetation (eucalyptus) fire are determined from real and imaginary components of complex relative dielectric permittivity measured by the network analyser. Average momentum transfer electron–neutral collision frequency and electron density in the vegetation fire are then calculated from the measured real and imaginary parts of complex relative dielectric permittivity.
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Electromagnetic and Microwave Absorption Properties of Carbonyl Iron/Fe91Si9 Composites in Gigahertz Range

Electromagnetic and Microwave Absorption Properties of Carbonyl Iron/Fe91Si9 Composites in Gigahertz Range

It is clear that the frequency band of RL < –20 dB gets broader and the thickness gets thinner with increasing FSP content in the frequency range of 2 - 7 GHz. The improvement in microwave absorption of the composites with the addition of FSP is suggested to originate from the efficient combination of CIP and FSP. Generally, excellent EM-wave absorption results from efficient complementarities between the relative permittivity and permeability in materials. Either only the magnetic loss or only the dielectric loss may result in weak EM-wave absorption properties due to the imbalance of the EM impedance match [11]. The introduction of FSP to CIP weakens the dielectric loss, but has not weakened the magnetic loss too much. Thus, a better EM impedance match could be established due to the combination of the reduced dielectric loss and nearly invariable magnetic loss, resulting in the enhanced microwave absorption [6]. Figure 5 shows the distribution of FSP and CIP in the paraffin matrix. the FSP acts not only as a magnetic ma- terial, increasing the permeability of the composites powder, but also as an insulating matrix distributed among the gaps between carbonyl-iron particles, which could reduce the eddy current loss through increasing electric resistivity as an important reason bringing about the excellent microwave absorption [20].
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A PIN-Loaded Microstrip Patch Antenna with the Ability to Suppress Surface Wave Excitation

A PIN-Loaded Microstrip Patch Antenna with the Ability to Suppress Surface Wave Excitation

The radius of the circular patch was chosen according to the reduced surface wave condition in Eq. (2), which in this case is equal to 55.8 mm. Using these parameters, we obtained ka= 2.2249 from the data in Fig. 2. By substituting ka in Eq. (5), the relative permittivity r was calculated to be 1.46, which is the exact value that makes the pin-loaded patch resonate at the required frequency. For practical reasons, however, we used the common Rogers RT/Duroid 5880, which has r = 2 . 2 as a substrate for this design. In order to reduce the effective permittivity under the patch to 1.46, hence having a resonance frequency at 1.575 GHz, a 1-mm thick portion of the substrate out of the 1.6 mm total thickness was removed with a milling machine, as shown in Fig. 3. The inner radius of the removed portion is 34 mm and the outer radius is equal to the radius of the patch. These dimensions were obtained through simulations using ANSYS HFSS to obtain the desired resonance frequency. The structure sits on 140 mm by 140 mm ground plane and is excited by a coaxial feed port located at a radial distance from the center equal to 29 mm. It is important to note here that the back of the antenna is covered with another ground plane to substitute for the metallic part that was removed with the dielectric.
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PREPARATION AND CHARACTERIZATION OF NANOCRYSTALLINE Ba(Ti0.96SnxZr0.04-x)O3 CERAMIC

PREPARATION AND CHARACTERIZATION OF NANOCRYSTALLINE Ba(Ti0.96SnxZr0.04-x)O3 CERAMIC

The real (ε') part of relative permittivity and tan δ within the frequency range of 40 Hz - 1 MHz of BT, BTSZ1, BTSZ2 and BTSZ3 ceramics at room temperature are shown in Fig. 4 and 5 respectively. The value of dielectric constant is higher at lower frequency and decreases with increase in frequency due to the dielectric relaxation, which is a characteristic feature of the ferroelectric materials irrespective of composition of the specimens (Lines et al., 1979). The values of real dielectric constant and loss tangent for BT and BTSZ1, BTSZ2 and BTSZ3 are shown in table 3.
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