Design of a High-performance Flat Reflector Antenna Based on Conformal Transformation Optics

In this paper, we design an implementable high-performance flat reflector based on conformal transformation optics. In the proposed 2-dimensional device, the rescaling refractive index approach is applied to overcome the sub-unit refractive index issue, resulting in an all-dielectric isotropic graded-index medium that is physically implementable. Rotating the permeability profile around the antenna axis yields the 3-dimensional profile of the flat reflector construction. The dielectric with continuous refractive index profile is split into eleven layers with a constant refractive index. The proposed antenna requires only dielectric layers with the permittivity of 1.1 to 3.8, making it realizable. Simulation results show that the proposed flat reflector can operate in wide frequency bandwidth. The simulated antenna gain is about 25.27 to 29.55 dBi in the 13-30 GHz frequency range with the side-lobe level below -15 dB. Design and simulation of the proposed antenna are done using COMSOL Multiphysics, and simulation results are validated with CST Studio Suite.

Reliability-based topology optimization of piezoelectric smart structures with voltage uncertainty

Currently, most of the piezoelectric structures are designed under deterministic conditions, where the influence of uncertain factors on the output motion accuracy is ignored. In this work, a probabilistic reliability-based topology optimization method for piezoelectric structure is proposed to deal with the working voltage uncertainty. A nested double-loop optimization algorithm of minimizing the total volume while satisfying the reliability requirement of the displacement performance is established, where the PEMAP-P (piezoelectric material with penalization and polarization) model is used for parameterization of stiffness matrix, piezoelectric coupling matrix, and polarization direction. This strategy consists of an inner loop for reliability analysis and an outer loop for topology optimization. The reliability index approach based on most probable point (MPP) is used for realizing the evaluation of reliability constraint in reliability analysis. The sensitivities of reliability constraint with respect to the random variables and design variables are detailed using the adjoint variable method. Typical examples are performed to illustrate the effectiveness of the proposed RBTO method. A comparison of the optimization results for different reliability indexes, standard deviations of the voltage, spring stiffnesses, and displacement limits are conducted, as well as the deterministic topology optimization results.

Fabrication, characterization, and optimization selection of ceramic particulate reinforced dental restorative composite materials

The objective of the article is to explore the fabrication of dental restorative composite materials and the ranking order using the preference selection index (PSI) as a multi criteria decision making (MCDM) technique under a set of conflict performance defining criteria (PDCs). The polymer matrix of the dental restorative composite was prepared using bisphenol a-glycidyl methacrylate (55 wt.%), triethylene glycol dimethacrylate (44 wt.%), camphorquinone (0.3 wt.%), and ethyl 4-(dimethylamino) benzoate (0.7 wt.%). Five different dental restorative composite material compositions were fabricated using hybrid nSiO2-TiO2 particulates with a variation of nSiO2 (0, 2, 4, 6, 8 wt.%) while TiO2 is constant (15 wt.%). The results revealed that an increasing trend has been found in compressive strength, flexural strength, Vickers hardness, etc., while a decreasing trend has been shown in depth of cure, polymerization shrinkage, degree of conversion etc. The performance analysis of five dental composite formulations via the PSI method shows the following ranking order: nS4 > nS6 > nS2 > nS0 > nS8. The obtained experimental results are associated with the ranking order of the different sets of dental composite formulations. Hence, the preference selection index approach is one of the best techniques among MCDM techniques for ranking under different PDCs.

Corporate Governance and Leverage Mechanisms on Integrity of Financial Report: Conservatism Index Approach in BUMN

The integrity of financial statements is related to one of the characteristics required by IFRS, namely faithful representation. The financial statements that are presented must contain information that is relevant and reliable so that it has high integrity and can be used by stakeholders in making decisions. In reality, realizing the integrity of financial statements is a difficult thing. There have been several cases that cast doubt on the level of integrity of financial statements. One of them happened to PT Jiwasraya (Persero) recently. This research is aimed to examine the effect of corporate governance mechanisms proxied by (institutional ownership, proportion of independent commissioners, and audit committee meetings) and leverage on the integrity of financial statements using a conservatism index approach in the market book value. Firm size as a control variable. The population is BUMN listed on the Indonesia Stock Exchange from 2016 to 2018 with a sample of 22 companies. The data analysis method used is panel data regression. The results of the common effect model test that only the audit committee meeting variable has a significant influence on the integrity of the financial statements, while the variable institutional ownership, the proportion of independent commissioners and leverage has an effect but is not significant on the integrity of the financial statement

PERFORMANCE OF CZECH FOOTBALL CLUBS: MALMQUIST INDEX APPROACH

Sport has become an important part of our lives in the modern times and sporting sites contribute significantly to the image and texture of modern cities. Regarding the popularity of sport, and football in particular, it has become an important modern place where specific types of economic and social interaction take place. The aim of this article is to propose a method for evaluating the performance of football clubs based on DEA and Malmquist index. Professional Czech football clubs playing in the Czech football competition Fortuna:Liga were selected for empirical analysis. To analyze the relative efficiency of football clubs, BCC and CCR models were employed. The study was conducted on a sample of 20 clubs through 2 inputs and 1 output collected during the 2015/16 – 2019/20 seasons. For some clubs the values of the Malmquist index were calculated. With help of MI it was possible to quantify the total productivity change factor and to decompose it to technological change and technical efficiency change. The results show that Czech football clubs achieved a relatively high level of efficiency in the period monitored and that traditional clubs achieved the highest efficiency score. These results could help club managers improve the performance of their teams.

A New Method (MINDED-BA) for Automatic Detection of Burned Areas Using Remote Sensing

This work presents a change detection method (MINDED-BA) for determining burned extents from multispectral remote sensing imagery. It consists of a development of a previous model (MINDED), originally created to estimate flood extents, combining a multi-index image-differencing approach and the analysis of magnitudes of the image-differencing statistics. The method was implemented, using Landsat and Sentinel-2 data, to estimate yearly burn extents within a study area located in northwest central Portugal, from 2000–2019. The modelling workflow includes several innovations, such as preprocessing steps to address some of the most important sources of error mentioned in the literature, and an optimal bin number selection procedure, the latter being the basis for the threshold selection for the classification of burn-related changes. The results of the model have been compared to an official yearly-burn-extent database and allow verifying the significant improvements introduced by both the pre-processing procedures and the multi-index approach. The high overall accuracies of the model (ca. 97%) and its levels of automatization (through open-source software) indicate potential for being a reliable method for systematic unsupervised classification of burned areas.