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This paper aims to study tuning effects on thick film microstripline due to ferrite thick film overlay.

The possibility of obtaining tuning characteristics in the Ku band microwave region in the absence of external magnetic field by a simple process of using Ni_xZn_1−xFe₂O₄ thick film and bulk as in‐touch overlay over Ag thick film microstripline was investigated. The microstripline is basically a non‐resonant component with high‐transmission at a large microwave frequency band. The ferrite was synthesized by precursor method and the thick films were deposited by screen printing.

It was found that tuning characteristics were observed and composition, thickness and precursor dependent changes occurred. The changes with composition are more prominent in the 14.5‐16.5 GHz range. Also, the ferrite thick film overlay produces a deep notch at 15.7 GHz. It is observed that the pellet overlay also makes the microstripline very dispersive with a high‐insertion loss in the 16‐17 GHz range. The presence of permeability‐related effects interfering with the normal propagation of the microstrip circuits might be causing the changes in the circuits.

Owing to the Ni_xZn_1−xFe₂O₄ overlay the simple microstripline can be tuned to have narrow band filter type of characteristics. Thick film Ni_xZn_1−xFe₂O₄ overlay gives the added advantage of planer configuration along with cost‐effectiveness in the absence of magnetic field.

The purpose of this paper is to report the effect of bismuth oxide thick films of various thicknesses on the X band (8‐12 GHz) response of Ag thick film microstrip rectangular patch antenna.

The effect of bismuth oxide thick film overlay of different thickness on Ag thick film microstrip rectangular patch antenna was investigated in the X band (8‐12 GHz). The change in the resonance frequency, amplitude, band width, quality factor, and input impedance of the antenna were studied. Using the resonance frequency the permittivity and conductivity of bismuth oxide thick film was measured.

Thickness of Bi₂O₃ thick film overlay dependent changes in the patch antenna characteristics is obtained. The resonance frequency shifts to higher frequency end due to overlay. The input impedance decreases due to the overlay. The dielectric constant of bismuth oxide thick film calculated from shift in resonance frequency shows thickness dependent values.

The microwave permittivity and conductivity of Bi₂O₃ thick film have been reported for the first time using overlay on thick film patch antenna. Thickness of overlay dependent tuning of the antenna has been achieved.

The purpose of this paper is to study thickness dependent variation in microwave properties of the Mg_xMn_(0.9−x)Al_0.1Zn_0.8Fe_1.2O₄ (x=0.8, 0.9) thick films and enhancement of power efficiency of Ag thick film EMC patch antenna.

X‐band microwave properties of the Mg_xMn_(0.9−x)Al_0.1Zn_0.8Fe_1.2O₄ (x=0.8, 0.9) thick films were measured by superstrate technique using Ag thick film EMC patch antenna as the resonant element. The complex permittivity and permeability of these thick films were also measured by this technique. The microwave response of the EMC patch, complex permeability and permittivity of Mg_0.8Mn_0.1Al_0.1Zn_0.8Fe_1.2O₄ and Mg_0.9Al_0.1Zn_0.8Fe_1.2O₄ thick films and their thickness dependency were investigated.

The XRD patterns reveal the cubic spinel crystal system was obtained for both compositions. The crystallite size obtained was 134.68 nm for Mg_0.8Mn_0.1Al_0.1Zn_0.8Fe_1.2O₄ and 155.99 nm for Mg_0.9Al_0.1Zn_0.8Fe_1.2O₄ The superstrate technique has been used successfully to evaluate the complex permittivity and permeability of the ferrite thick films in the X band. The EMC patch also show thickness and composition dependent frequency agility and enhancement of power efficiency.

The complex permeability of Mg_xMn_(0.9−x)Al_0.1Zn_0.8Fe_1.2O₄ (x=0.8, 0.9) thick films measured by superstrate technique is reported in this paper. The superstrate of Mg_xMn_(0.9−x)Al_0.1Zn_0.8Fe_1.2O₄ (x=0.8, 0.9) thick films makes the Ag thick film EMC patch antenna frequency agile and power amplification is obtained.

The purpose of this paper is to study properties of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films for application in tuned devices.

The effect of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films overlay of different thickness on Ag thick film microstrip rectangular patch antenna was investigated in the X band (8‐12 GHz). Using Ag thick film microstrip rectangular patch antenna the thick and mixed thick films was characterized by microwave properties such as resonance frequency, amplitude, bandwidth, quality factor and input impedance. Using the resonance frequency the permittivity of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films was measured.

Cubic structure of single magnesium oxide and monoclinic structure of bismuth oxide was present in mixed thick film. Also the morphology of single thick films was maintained in mixed thick film of magnesium oxide‐bismuth oxide. Due to overlay magnesium oxide and magnesium oxide‐bismuth oxide mixed thick films, change in resonance frequency shifts towards high frequency end was observed. Dielectric constant of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick film calculated from resonance frequency decreased with increase in thickness.

The microwave properties using Ag thick film microstrip patch antenna due to overlay of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films have been reported for the first time. Thickness of overlay dependent tuning of the antenna has been achieved.

The purpose of this paper is to report on the Ku band microwave characteristics of moisture laden soya seeds using overlay technique.

Ku band (13‐18 GHz) moisture dependent microwave permittivity, conductivity, penetration depth of moisture laden soybean (Glycine Max) using overlay on Ag thick film equilateral triangular patch antenna are studied. The change in the frequency response of the patch antenna due to change in moisture content of the soybean overlay has been used to obtain the various microwave properties.

The permittivities obtained are in the range expected of moisture laden soybean. As moisture content increases microwave dielectric constant, dielectric loss, and conductivity of soybean increases. Only the amplitude data have been used here.

Ku band characterization of soybean has been done using overlay technique. The thick film patch antenna is sensitive even to ∼4 percent moisture content in the overlay material. This can be used for even moisture sensing at low moisture levels. This paper is believed to be an original research report.

The purpose of this paper was to determine the complex permittivity of bismuth strontium manganites (Bi_1−xSr_xMnO₃) in the 8‐12 GHz range by using perturbation of Ag thick film microstrip ring resonator (MSRR) due to superstrate of both bulk and thick film.

The BSM ceramics were synthesized by simple low cost solid state reaction method and their fritless thick films were fabricated by screen printing technique on alumina substrate. A comparison has been made between the X band response of Ag thick film microstrip ring resonator due to perturbation of bulk and thick film Bi_1−xSr_xMnO₃ ceramic.

The bulk and thick film superstrate decreases the resonance frequency of MSRR. In this technique even minor change in the properties of superstrate material changes the MSRR response. Variation of strontium content also influences microwave conductivity and penetration depth of bulk and thick films.

The microwave complex permittivity decreases with increase in Sr content in bismuth manganite and it is higher for bulk as compared to its thick films. The superstrate on Ag thick film microstrip ring resonator is an efficient tool capable of detecting the composition dependent changes in microwave properties of ceramic bulk and thick films.

The aim of this paper is to investigate microwave Ku band absorbance, complex permittivity, and permeability of SrFe₁₂O₁₉ thick films by a simple and novel waveguide technique.

The glass frit free or fritless strontium hexaferrite thick films were formulated on alumina by screen printing technique from the powder synthesized by chemical co precipitation method for pH 11 adjusted during the reaction. The 13‐18 GHz frequency band microwave absorbance of the SrFe₁₂O₁₉ thick films by a simple waveguide method. The complex permittivity and permeability of strontium hexaferrite thick films was measured by voltage standing wave ratio technique.

SrFe₁₂O₁₉ thick films show high ∼80 percent absorbance in the whole 13‐18 GHz frequency band. The thickness dependant microwave properties of strontium hexaferrite thick films were observed. The real permittivity ε′ lies in between eight and 35 with the variation in thickness of the thick film SrFe₁₂O₁₉. The real microwave permeability μ′ of strontium hexaferrite thick films lies in the range 1.12‐6.41. The resonance type behavior was observed at frequency 14.3 GHz. The SrFe₁₂O₁₉ thick film of thickness 30 μm could be a wide band (∼5,000 MHz) absorber with absorbance ∼87 percent for the whole 13‐18 GHz frequency band.

The complex permeability of strontium hexaferrite thick films was measured by simple novel waveguide method. The high absorbance (∼87 percent) of thick film SrFe₁₂O₁₉ over a broad band ∼5,000 MHz will be useful in achieving RAM coatings required for 13‐18 GHz frequency band.

The purpose of this paper is to describe the use of copper‐substituted nickel manganite thick film and bulk ceramic superstrate on Ag thick film microstrip straight resonator (MSR), to modify its response and measure complex permittivity as a function of copper.

The glass frit free (fritless) copper‐substituted nickel manganite thick films were formulated on alumina substrate by screen printing technique from the powder synthesized by oxalic precursor method. A comparison has been made between the X band response of Ag thick film MSR due to perturbation of bulk and thick film Ni_(1−x)Cu_xMn₂O₄ (0≤x≤1) ceramic. The shift has been used to measure the permittivity of the ceramic. The dielectric constants obtained by superstrate technique on Ag thick film microstrip component are comparable to those obtained from theoretical calculations.

The resonance frequency of MSR shifts towards lower frequency due to the presence of Ni_(1−x)Cu_xMn₂O₄ (0≤x≤1) ceramic as superstrate. The dielectric constant of bulk and thick film match well with the theoretical values. The dielectric constant increases with copper concentration and shows reduction of power gain of MSR. The peak output (power gain) of MSR due to thick film NiMn₂O₄ increases by 10.19 per cent with decrease in bandwidth and increase in the quality factor with copper concentration.

The superstrate on Ag thick film straight resonator is an efficient tool capable of detecting the composition‐dependent changes in microwave properties of ceramic thick films. These Ni_(1−x)Cu_xMn₂O₄ ceramic being thermistor materials apart from modifying the response can also be used as power sensors providing cost‐effective miniaturization.

The purpose of this paper is to employ analytical and numerical techniques to generate modal displacement data of damaged beams containing very small crack-like surface flaws or slots and to use the data in the development of damage detection methodology. The detection method involves the use of double differentiation of the modal data for identification of the flaw location and magnitude.

The modal displacements of damaged beams are simulated analytically using the Bernoulli-Euler theory and numerically using the finite element method. The principle used in the analytical approach is based on changes in the transverse displacement due to the localized reduction of the flexural rigidity of the beam. Curvature analysis is employed to identify and locate the structural flaws from the modal data. The curvature mode shapes are calculated using a central difference approximation. The effects of random noise on the detectability of the structural flaws are also computed.

The analytical approach is much more robust in simulating modal displacement data for beams with crack-like surface flaws or slots than the finite element analysis (FEA) approach especially for crack-like surface flaws or slots of very small depths. The structural flaws are detectable in the presence of random noise of up to 5 per cent.

Simulating the effects of small crack-like surface flaws is important because it is essential to develop techniques to detect cracks at an early stage of their development. The FEA approach can only simulate the effects of crack-like surface flaws or slots with depth ratio greater than 10 per cent. On the other hand, the analytical approach using the Bernoulli-Euler theory can simulate the effects of crack-like surface flaws or slots with depth ratio as small as 2 per cent.

The purpose of this study is to evaluate the effect of the addition of dried lemongrass leaves (DLGL) powder, at different levels, on phenolics content, antioxidant activities, consumer acceptance and the inhibition of lipid peroxidation of roasted coffee (RC).

DLGL powder was incorporated at the levels of 0%, 2.5%, 5.0%, 7.5% and 10% of RC weight. The total flavonoids (TF), total phenolics (TP) and antioxidant activity measured using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and reducing power assay of RC, DLGL and binary mixture of them determined. The oxidative indices of coffee oil samples during storage were investigated. In addition, the sensory characteristics of RC fortified with different levels of DLGL powder were evaluated.

The TP content of DLGL powder was 1,100.32 mg/100 g DWb, nearly 1.2 times higher than found in RC beans. The TF content of RC enriched with 2.5%, 5.0%, 7.5% and 10% DLGL were found to be around 1.05, 1.10, 1.15 and 1.20 times higher than that in the control coffee samples. RC supplemented with various levels of DLGL powder showed higher DPPH radical scavenging and reducing power activities. At the end of the storage period (six months), the acid, peroxide, P-Anisidine and total oxidation value values of RC supplemented with 10% DLGL powder were about 1.94, 2.52, 2.60 and 2.59 times as low as in the control sample without any addition of DLGL powder, respectively. RC containing 2.5% and 5.0% DLGL powder had significantly (p < 0.05) the highest sensory scores. Consequently, the addition of DLGL in coffee at up to a 5% ratio may have potential health benefits.

RC containing 2.5% and 5.0% DLGL powder had significantly (p = 0.05) the highest sensory scores.

Consequently, the addition of DLGL in coffee at up to a 5% ratio may have potential health benefits.