Resonant coaxial SMA microwave permittivity sensor

Resonant coaxial SMA microwave permittivity sensor is introduced. It is constructed using only commercially available SMA connectors. The sensor is tested in two different frequency ranges for two different dielectric constant ranges, from 1 to 10 and from 10 to 80. Presented sensor is designed, fabricated, simulated, and tested. Good agreement between simulations and measurements is shown. The sensor is also applicable for differential permittivity measurements

Laguerre-like methods for the simultaneous approximation of polynomial multiple zeros

Two new methods of the fourth order for the simultaneous determination of multiple zeros of a polynomial are proposed. The presented methods are based on the fixed point relation of Laguerre's type and realized in ordinary complex arithmetic as well as circular complex interval arithmetic. The derived iterative formulas are suitable for the construction of modified methods with improved convergence rate with negligible additional operations. Very fast convergence of the considered methods is illustrated by two numerical examples

A new higher-order family of inclusion zero-finding methods

AbstractStarting from a suitable fixed point relation, a new one-parameter family of iterative methods for the simultaneous inclusion of complex zeros in circular complex arithmetic is constructed. It is proved that the order of convergence of this family is four. The convergence analysis is performed under computationally verifiable initial conditions. An approach for the construction of accelerated methods with negligible number of additional operations is discussed. To demonstrate convergence properties of the proposed family of methods, two numerical examples results are given

The Ability to Minimize a New Type of Moderate-Bandwidth Microwave Filter

An example of minimizing the width of a microwave filter structure by bending the stubs and reducing the number of required via holes is presented in this paper. It is shown that the filter area can be reduced near 2 times after bending the stubs. EM model of minimized structure is presented and compared with common filter design

Strain field measurements of glass ionomer cement

Extensive evolution of glass ionomer cements (GIC) has marked a significant shift in the practice of luting indirect dental restorations limiting the use of zinc-phosphate and zinc-polycarboxylate cements to a few indications. GIC are now one of the materials of choice for cementation of all ceramics, fiber reinforced composite posts and veneers. GICs are determined by unique properties like chemical adhesion to tooth and base metals, low thermal expansion coefficients similar to dentin and minimal microleakage at the tooth-enamel interface due to low shrinkage. Shrinkage strain is identified as the cause, and the associated stress as the mechanism for the loss of marginal adaption and cohesive fracture within the material. The aim of this study is to measure the strain and displacement field in a conventional GIC (Riva Luting, SDI, Australia) related to different cement diameter, using 3D Digital Image Correlation (DIC) method. The experiment is done for samples with thickness of 1 mm combined with diameters of 4 mm (Group I) and 3 mm (Group II). The strain field is measured using 3D 11optical system Aramis 2M (GOM, Braunschweig, Germany). This study provides valuable data about strain behaviour and displacement as a possible failure factor in GIC, Riva Luting. Visible differences between Group I and Group II were observed

Strain field measurements of glass ionomer cement

Extensive evolution of glass ionomer cements (GIC) has marked a significant shift in the practice of luting indirect dental restorations limiting the use of zinc-phosphate and zinc-polycarboxylate cements to a few indications. GIC are now one of the materials of choice for cementation of all ceramics, fiber reinforced composite posts and veneers. GICs are determined by unique properties like chemical adhesion to tooth and base metals, low thermal expansion coefficients similar to dentin and minimal microleakage at the tooth-enamel interface due to low shrinkage. Shrinkage strain is identified as the cause, and the associated stress as the mechanism for the loss of marginal adaption and cohesive fracture within the material. The aim of this study is to measure the strain and displacement field in a conventional GIC (Riva Luting, SDI, Australia) related to different cement diameter, using 3D Digital Image Correlation (DIC) method. The experiment is done for samples with thickness of 1 mm combined with diameters of 4 mm (Group I) and 3 mm (Group II). The strain field is measured using 3D 11optical system Aramis 2M (GOM, Braunschweig, Germany). This study provides valuable data about strain behaviour and displacement as a possible failure factor in GIC, Riva Luting. Visible differences between Group I and Group II were observed

Ultra wideband bandpass filters with specified relative bandwidth

Algorithm for the realization of the broad range of values of wide relative bandwidth (RBW) bandpass filter is introduced. Algorithm is based on periodic ideal cells each with short-ended stub. Theory is developed for a symmetrical cell with proportional transmission lines, nonuniform or uniform, in term of characteristic impedance. The theory is applied for the uniform transmission lines. Simple equation of the ratio between characteristic impendence of the short-ended stub and the characteristic impendences of the main lines is given for the broad range of RBW. Realizable filters are for the very wide RBW up to over 1.5 (150%). Technology is chosen in microstrip with vias for the short ends. It is without coupling, without defected ground structure (DGS) and only with a single layer. The procedure is tested on the fabricated filters for very wide RBW of 1.5 (150%). Agreement between measurements and simulations is excellent

Synergistic Effects of the Supporting Material and Annealing Temperature on the Performance of Pt Thin Film Catalysts

The electrocatalytic oxidation of small organic molecules, such as methanol, ethanol and formic acid has been extensively studied due to their properties that make them suitable for use in fuel cells. Particularly, the electrochemical oxidation of formic acid has been comprehensively examined as the anodic reaction in direct formic acid fuel cell. The main goal in the development of the catalysts for formic acid oxidation (FAO) is to find the optimal balance between catalytic performance (activity/stability) and the catalyst cost, i.e. quantity of the noble metal used. In the work presented herein, we explored the synergistic effects of the supporting material and annealing temperature on the performance of Pt thin film catalysts for FAO in acidic media. Our results show that compared to the as-prepared Pt films, the annealed (500 oC) films show exceptional activity for FAO reaction on both Pt/Ni and Pt/Cr catalysts, with 5-fold and 15-fold improvement, respectively. The 500 oC annealed Pt/Cr catalyst was found to be the most active, the most selective and the most stable catalyst in our study. A catalyst with the best marks for all three characteristics is a very rare find in electrocatalysis in general.Lectur

New Data about the Lower and Middle Palaeolithic in the Western Morava valley

A relatively small number of Lower and Middle Palaeolithic open-air sites have been registered in southeast Europe. There are only two regions where sites from this period have been systematically surveyed, and where they have been encountered in considerable numbers: the valley of the Pineios river in Greece and northern Bosnia. Not a single site with significant concentration of finds has been found in Serbia and isolated artifacts ascribed to the Middle Palaeolithic were found at few sites. All this has changed dramatically in recent years when a large number of sites with finds from the Lower and Middle Palaeolithic have been recorded in the zone from Čačak to Kraljevo in the West Morava valley. The site surveying in the area has opened an entirely new perspective in the investigation of the Palaeolithic in this part of the Balkans