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A novel high-precision model of a custom-made coaxial chamber used for broadband measurement of the relative complex permittivity at microwave frequencies is presented. The model is based on a surface integral-equation formulation of the method of moments tailored for bodies of revolution. All singular integrals encountered in the numerical analysis are calculated in a unified way with a novel integral transformation, which enables the precision of up to 12 significant digits using the 64-bit representation of real numbers. The dielectric parameters are estimated from the reflection-coefficient measurement of the chamber with a disk-shaped dielectric sample by comparison of the measured data with the high-precision numerical analysis of the chamber. The complete measurement procedure is illustrated and verified using samples of known dielectric properties. This is the peer-reviewed version of the paper: Petrović, J.G., Olćan, D.I., Obradović, N.N., Djordjević, A.R., 2022. High-Precision Method of Moments Applied to Measurement of Dielectric Parameters at Microwave Frequencies. IEEE Transactions on Microwave Theory and Techniques, 70, 2, 970-979. [https://doi.org/10.1109/TMTT.2021.3136294]

An approach to singularity cancelation by a variable transformation of Green’s function in 2-D case, having log( $R$ ) singularity, is outlined. It is intended for the method of moments analysis of 2-D structures of both curvilinear and flat cross sections. If the transformation is used with Legendre or Chebyshev polynomials as entire-domain basis functions, all involved integrals can be calculated with high precision using Gauss–Legendre quadrature. The optimal parameter of the transformation, having the minimal number of integration samples needed to reach 14-digit precision, is provided. Error estimations are presented for calculated current distributions on strips up to 400 wavelengths wide, analyzed with up to 1500 entire-domain basis functions.

Nonuniform helical antennas have many degrees of freedom, which makes the search space for the optimal design very challenging. The objective of this paper is to systematically analyze nonuniform helical antennas with linearly varying geometrical parameters and to provide analytical equations that approximate the optimal design and the gain of the designed antennas. Using various optimization algorithms, we made a large database of the optimal nonuniform helical antennas with linearly varying geometrical parameters. Based on these results, we made analytical equations that approximate the optimal design and the gain of the designed antennas. These equations allow for a fast design procedure yielding all necessary parameters needed for the design and fabrication of nonuniform helical antennas that meet specified characteristics. Special attention is devoted to antenna losses. Antennas designed following the presented procedure achieve around 2.5 dB higher gain than uniform helical antennas of the same axial length, while maintaining the bandwidth and axial ratio. As a verification of the proposed design procedure, a helical antenna with the central operating frequency of 1 GHz was designed, simulated, fabricated, and measured. The comparison between measured and simulated results confirms the validity of the presented design procedure.

Sintering of pure cordierite 2MgO:2Al2O3:5SiO2, and cordierite with the addition of 5 mass % TeO2 was studied. Green bodies were prepared from powder mixtures mechanically activated in a high-energy planetary mill, shaped by uniaxial (20 MPa) and cold isostatic pressing (1000 MPa). The pressure-less sintering of these specimens was performed at 1350°C for 1 h. High relative density over 95% of the theoretical value was obtained through solid-state reaction and pressure-less sintering of powder activated for 40 min, and for the first time reported in the literature. Phase composition and microstructures of sintered samples were determined by XRD and SEM, coupled with EDS mapping. The real part of the complex relative permittivity of the samples was measured at 200 MHz. The loss tangent of all samples was below the resolution of the measurement setup. A strong correlation between the relative permittivity and the density agrees with previously published data. This is the peer-reviewed version of the article: Obradović, N., Pavlović, Vera, Kachlik, M., Maca, K., Olćan, D., Đorđević, A., Tshantshapanyan, A., Vlahović, B., Pavlović, Vladimir, 2018. Processing and properties of dense cordierite ceramics obtained through solid-state reaction and pressure-less sintering. Advances in Applied Ceramics. [https://doi.org/10.1080/17436753.2018.1548150]

The aim of the research is to assess the influence of pszchosocial factors of the working environment on the working capacitz index of health workers in clinical and hospital activities. ...

Solid-state reaction between BaTiO3and Fe2O3was used to produce a multiferroic heterostructure composite. Commercial BaTiO3and Fe(NO3)3•9H2O were suspended in ethanol for 30 minutes in an ultrasound bath. The prepared mixture was thermally processed at 300°C for 6 h. Sintering at 1300 °C for 1 h resulted in a mixture of different phases, BaTiO3, BaFe12O19and Ba12Ti28Fe15O84, which were confirmed by x-ray powder diffraction. A dense microstructure with a small volume fraction of closed porosity was indicated by the scanning electron microscopy, while a homogeneous distribution of Fe ions over BaTiO3phase was visible from energy dispersive spectroscopy mapping. Doping of BaTiO3with Fe2O3resulted in formation of magnetic hexaferrite phases, as confirmed by dielectric measurements that showed a broadened maximum of the permittivity measured as a function of temperature. © 2021 Authors. Published by association for ETRAN Society.

We propose a design approach for band-pass microwave filters based on optimization of discrete-valued parameters of filters using an implementation of (1 + (l, l)) genetic algorithm. If the filter is made of SMD components then only discrete values are allowed. The proposed design approach yields a solution with feasible components values in the end, without further need for tuning and adjustments of component values that is needed in the case when real numbers are used during optimization. The optimization setup is run for 20 times and obtained (suboptimal) solutions are presented. One of the best optimized solutions of a band-pass filter is chosen for further analysis. The found filter design is verified using a circuit solver including the yield analysis, 3D electromagnetic simulations and by measurements of the manufactured prototype. The presented results as well as the optimization run-time show that the proposed approach based on discrete optimization can be used to design microwave filters.

Machine learning is used to determine the polynomial regression of the coefficients of surface currents approximation for a curvilinear 2-D scatterer. The training data are obtained using method of moments with higher order basis functions and Galerkin testing procedure. The effect of polynomial regression order to the accuracy of calcualted radar cross-section is explored.

We present results for comparison of gain of the optimal uniform and nonuniform helical antennas taking into the account conductor losses. Critical conductivities are observed, for the given operating frequency and the helix axial length. Above the critical conductivity, the gain of the nonuniform helical antennas with linearly varying geometrical parameters is up to 2 dB higher than the gain of the optimal uniform antennas. However, below the critical conductivity, the difference between the gain of the nonuniform and uniform helical antennas is reduced, and the gain of those antennas becomes comparable. Data for the normalized critical conductivities are presented.

На сьогодні бухгалтерська звітність є одним з найбільш динамічних елементів методу обліку. Перш за все, це пов’язано з відповідністю його предметa вимогам різних користувачів, які бажають дізнатися, що економічні умови в реальності швидко змінюються. Тому, застосовуючи методи економічного аналізу на основі даних бухгалтерського обліку, можна розрахувати діапазон цифр, що дають можливість оцінити як фінансовий стан, так і економічний потенціал підприємства в майбутньому і минулому. Тому для обчислення таких цифр у справах бухгалтерського обліку повинна бути інформація про надзвичайні наслідки, що впливають на виробничі процеси, вартість продукції і фінансові результати підприємства. Ця умова дозволить оцінити їхній вплив на фінансові показники та економічний потенціал підприємства. Сформульовано напрями розширення фінансової звітності за змістом і формою. Фінансова звітність удосконалюється з метою відображення інформації про надзвичайні наслідки за рахунок розширення факторів у наявних главах (як частина інших витрат) і формування нової глави V «Зовнішні та внутрішні ризики впливу на навколишнє середовище», що містить інформацію про відокремлення надзвичайних наслідків від витрати на діяльність. Фрагменти приміток до річної фінансової звітності розроблено, що дає можливість оцінити вплив надзвичайних наслідків на необоротні та оборотні активи і виробничий процес. Побудова конкретної інформації для внутрішнього використання про надзвичайні наслідки здійснюється на основі обґрунтованих напрямів формування внутрішньої звітності та розроблення шляхів і механізмів формування їхніх факторів. Це дозволило підвищити якість інформаційного простору управління діловою діяльністю в надзвичайних умовах. Використання пропозицій на практиці сприяло підвищенню якості інформаційного простору при ухваленні рішень користувачами і розробленні комплексу заходів щодо запобігання надзвичайним наслідкам та їх ліквідації . У свою чергу, аналітичні заходи, розраховані на основі їхніх фактів, ураховуватимуть низку факторів, що дозволяють повністю оцінити фінансовий стан та економічний потенціал., На сегодня бухгалтерская отчетность является одним из наиболее динамичных элементов бухгалтерского учета. Прежде всего, это связано с соответствием его предмета требованиям различных пользователей, желающих узнать, что экономические условия в реальности быстро меняются.Поэтому, применяя методы экономического анализа на основе данных бухгалтерского учета, можно рассчитать диапазон цифр, которые дают возможность оценить как финансовое состояние, так и экономический потенциал предприятия в будущем и прошлом. Построение конкретной информации для внутреннего использования о чрезвычайных последствия осуществляется на основе обоснованных направлений формирования внутренней отчетности и разработки путей и механизмов формирования их факторов. Использование предложений на практике способствовало повышению качества информационного пространства при принятии решений пользователями и разработке комплекса мероприятий по предотвращению и ликвидации чрезвычайных последствий., Nowadays accounting statements is one of the most dynamic accounting method elements. First and foremost it is related to the correspondence of its subject-matter to the demands of different users willing to know economic conditions in reality changing rapidly. Thus, applying methods of economic analysis on the basis of accounting data it is possible to calculate a range of figures giving an opportunity to estimate both financial condition and economic potential of the enterprise in the future and the past. That is why to calculate such figures in the copes of accounting there should be information about emergency consequences cases affecting the production processes, product cost and further the enterprise’s financial results. This condition will allow estimate their influence on the financial figures and economic potential of the enterprise. The directions of financial statement’s expanding in content and form are articulated. Financial statement is improved in order to reflect information about emergency consequences through expanding factors in already existing chapters (as a part of other costs) and formation of the new chapter V «External and internal risks environmental impact» containing information about separation of emergency consequences from activity costs. Fragments of notes to the annual financial statement are developed giving an opportunity to estimate the impact of emergency consequences on noncurrent and current assets and the production process. Building specific information for internal use about emergency consequences is performed on the basis of justified directions of internal reporting formation and development of ways and mechanisms of their factors formation. It allowed to increase quality of information space of business activity management in emergency conditions. The use of suggestions in practice contributed to increasing the information space quality in users’ decision-making and developing a complex of measures to prevent and address the emergency consequences. In its turn analytical measures calculated on the basis of their facts will take into account a number of factors allowing to fully estimate the financial condition and economic potential.