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

Enhanced Pt@Ni catalysts obtained by galvanic displacement method for successful methanol electrooxidation

The successful development of catalysts for the electrooxidation of small organic molecules, such as methanol, requires finding an optimal balance between the catalyst's cost and its activity/stability. Thus far, platinum (Pt) remains one of the best choice for methanol electrooxidation, despite its high costs, limited supply and tendency to poison with carbon monoxide (CO). In this work, the synergistic effect of the supporting material and annealing temperature in different atmospheres on the performance of the Pt@Ni catalyst was examined. The thin film Pt@Ni catalyst was obtained through spontaneous galvanic displacement by placing a drop of hexachloroplatinic acid onto the Ni support. To mitigate platinum susceptibility to poisoning species such as CO and enhance the catalytic efficiency of Pt@Ni at low potentials in methanol oxidation, the as-prepared catalyst was modified using controlled thermal treatment in a reductive atmosphere containing 5 % H2 and in an inert atmosphere (N2). The activity of the catalysts was tested in the methanol oxidation reaction, while the influence of thermal treatment on the surface morphology was monitored using atomic force microscopy (AFM). Preliminary results have indicated that the galvanic displacement method produces ultra-thin film Pt@Ni catalysts, which were further enhanced through controlled thermal treatment. The catalysts annealed in the inert atmosphere demonstrated superior activity compared to the as prepared and catalyst annealed in the reducing atmosphere

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

The design of advanced thin-film catalysts for electrooxidation of formic acid

Successful development of catalysts for electrochemical formic acid oxidation (FAO) requires finding an optimal balance between catalytic performance (activity/stability/selectivity) and the catalyst cost. While platinum is one of the most active catalyst materials for FAO, it suffers from performance loss at low overpotentials due to poisoning with CO, which is one of the intermediates formed in the so-called indirect path of FAO. In this work, we explored the synergistic effects of the supporting material and annealing temperature on the performance of Pt thin films over Cr support for FAO in acidic media. In an attempt to reduce the proneness of Pt to poisoning species i.e. CO and improve the catalytic performance of Pt/Cr at low potentials in the formic oxidation reaction, the as-prepared catalyst was modified using controlled thermal treatment. The influence of thermal treatment on the surface morphology was monitored using atomic force microscopy (AFM). The catalyst was electrochemically characterized with cyclic voltammetry and oxidation of CO monolayer, while the performance of the catalyst was tested in formic acid oxidation reaction. Based on the obtained results it was concluded that the improved activity on the annealed Pt/Cr system is a consequence of surface reconstruction of Pt film with predominant (111) orientation. Compared to other facets, the (111) facet selectively favors the oxidation of HCOOH via the direct path, avoiding the formation of COad at low potentials. Moreover, the Pt (111) facets offer improved stability of the catalyst compared to the as-prepared polycrystalline film. Finally, the Cr substrate also experiences improved stability after annealing, presumably due to the formation of a protective oxide layer. Thus, with the successful choice of the supporting material and annealing temperature, we were able to create a thin film catalyst with improved activity, selectivity, and stability, challenging conventional trade-offs in electrocatalysis