Dielectric nanoresonator for enhancement of 2D material photoluminescence

Nowadays the volume of transmitted information exponentially grows and requires the development of new telecommunication systems. Dielectric nanoresonators can be considered as a basic part of such systems to control the emission of the nanoscale source. Here we numerically investigated resonant dielectric nanoresonators for emission enhancements of 2D nanomaterials. We show that the radiative Purcell factor can achieve the value of up to 21 and 12 for the magnetic quadrupole and dipole responses, respectively. Also, we compare the directivity patterns for magnetic dipole and quadrupole resonances. The results obtained in this work can be applied in the development of optical chips and interfaces.

beamshapes : a Python package to generate directivity patterns for various sound sources

beamshapes is an open-source Python package that implements various directivity patternsfor sound sources. While there is an abundance of published directivity patterns in the literature- their computational implementations often remain as in-house scripts in proprietarylanguages. beamshapes overcomes this gap, and provides acousticians and bioacousticianseasily accessible implementations of sound source directivities.

3D shape optimization of loudspeakers

Improving the performance of loudspeaker units and cabinet designs traditionally relies on a combination of trial and error, sometimes based on a lumped parameter modelling approach. During the last decades, however, large-scale numerical simulations are playing a growing role as a means of improving performance of complex engineering devices such as loudspeakers. However, a numerical model still relies on the experience of the operating engineer to make the appropriate design changes. This can be a difficult task. The use of numerical simulations combined with optimization has a huge potential for further guiding the design process of advanced industrial products where intuition alone is not sufficient. Nevertheless, broadband acoustic simulations are still very time consuming. In this work, we explore the efficiency of a newly proposed semi-analytical adjoint sensitivity approach based on the boundary element method in combination with a lumped parameter model. The sensitivity analysis is used to shape optimize the cabinet of a loudspeaker using free form deformation. The objective of the optimization is to improve frequency responses and directivity patterns.

Directivity of sound propagation from an commercial supersonic engine inlet

The effects of mean flow variations on sound propagation from an axisymmetric commercial supersonic engine inlet were studied using numerical methods. A finite element model of the inlet was constructed in Ansys Fluent and used to solve for flow fields given by different initial conditions. Results from this model were fed into the aeroacoustic solver, Actran, and used to calculate far field radiated noise as well as the directivity of that noise. The acoustic source of this noise was a plane wave of a known strength placed at the fan face. In addition to assessing the effects of mean flow on the radiated noise transfer functions, the duct modes of the model were compared across different flow regimes. Relationships between mean flow parameters and the directivity of duct modes are developed. The results of this study will be used in further studies to gain a deeper understanding of how the underlying physics which govern the system create favorable or unfavorable directivity patterns.

An Inverse Microphone Array Method for the Estimation of a Rotating Source Directivity

Microphone arrays methods are useful for determining the location and magnitude of rotating acoustic sources. This work presents an approach to calculating a discrete directivity pattern of a rotating sound source using inverse microphone array methods. The proposed method is divided into three consecutive steps. Firstly, a virtual rotating array method that compensates for motion of the source is employed in order to calculate the cross-spectral matrix. Secondly, the source locations are determined by a covariance matrix fitting approach. Finally, the sound source directivity is calculated using the inverse method SODIX on a reduced focus grid. Experimental validation and synthetic data from a simulation are used for the verification of the method. For this purpose, a rotating parametric loudspeaker array with a controllable steering pattern is designed. Five different directivity patterns of the rotating source are compared. The proposed method compensates for source motion and is able to reconstruct the location as well the directivity pattern of the rotating beam source.

IMPROVING THE VARIOUS PROPERTIES OF THE UDA-YAGI ANTENNA

Рассматривается антенна Уда-Яги, которая предназначена для приема сигнала наземного телевещания в 57 частотном канале. Самыми важными характеристиками для антенны Уда-Яги являются коэффициент направленного действия, передне-заднее отношение (коэффициент защитного действия), при этом данные характеристики сильно зависят от числа директоров, применяемых в конструкции антенны. На основе произведенного электродинамического моделирования было определено, как изменятся характеристики диаграмм направленности антенны на частоте 762 МГц при применении различного числа директоров - от 1 (3-элементная антенна Уда-Яги) до 12 (14-элементная антенна Уда-Яги), при этом определено оптимальное количество директоров для ситуации, когда требуется достижение максимальной помехозащищенности (максимальное значение передне-заднего отношения). Приводятся диаграммы направленности при различном числе директоров на частоте 762 МГц, графики коэффициентов защитного действия (ПЗО) от числа директоров и от частоты, таблицы со сравнительными характеристиками диаграмм направленности. Моделирование производилось с использованием метода моментов, так как при его применении достигаются высокая скорость расчетов, а также высокая точность результатов. При моделировании антенна имела один рефлектор и активный элемент в виде полуволнового диполя The article considers the Uda-Yagi antenna, which is designed to receive a terrestrial television signal in a 57-frequency channel. The most important characteristics for an Uda-Yagi antenna are directivity, front-to-back ratio, and these characteristics are highly dependent on the number of directors used in the antenna design. On the basis of the electrodynamic simulation, we determined how the characteristics of the antenna directivity patterns at a frequency of 762 MHz will change when using a different number of directors - from 1 (3-element Uda-Yagi antenna) to 12 (14-element Uda-Yagi antenna), at the same time, we determined the optimal number of directors for the situation when the achievement of maximum noise immunity is required (the maximum value of the front-to-back ratio). The article gives directivity patterns for different numbers of directors at a frequency of 762 MHz, dependencies of directivity coefficients on the number of directors and on the frequency, tables with comparative characteristics of directivity patterns. We carried out the simulation using the method of moments, since it achieves a high speed of calculations, as well as high accuracy of results. During simulation, the antenna had one reflector and an active element in the form of a half-wave dipole

Acoustic scattering reduction in elastic materials with Bat optimization algorithm

A scattering-cancelation method is followed in this analysis. The opportunity to reduce the scattering effect in rigid cylinder with elastic cloaking material is investigated in the paper. The rigid cylinder with elastic cloaking and without elastic cloaking is analyzed for regular planes waves to test the scattering effect of the rigid cylinder. The energy due to reflected and travelled waves is presented mathematically. The parameter of the elastic cloaking such as thickness, density and Poisson ratio are optimized using BAT algorithm. Pressure filed of the rigid cylinder and directivity patterns scatter pressures in the cylinder are analyzed. The results revealed that, bat algorithm optimization provide the better results for elastic cloaking in the cylinder to reduce scattering effect.