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Том 59, № 2 (2016)
- Год: 2016
- Статей: 6
- URL: https://journals.rcsi.science/0735-2727/issue/view/10862
Article
Application of nanostructured silver film in multilayer contact system of Ti/Mo/Ag silicon photoconverters
Аннотация
In this article we have synthesized multilayer contact systems Ti/Ag and Ti/Mo/Ag with nanostructured silver films using two vacuum methods, namely the method of electron-beam evaporation and HF magnetron sputtering. Using the data of atomic force microscopy, X-ray diffraction and mass spectroscopy of the secondary neutrals in the paper we have investigated the influence of the application method and of the annealing conditions on the grain formation processes in silver thin films and mass transfer between the metal layers of the contact system. The decrease of surface resistivity of the developed contacts and, respectively, the increase of short-circuit current of the heterojunction silicon solar cells have been determined.
53-59
Active elements on a basis of ZnO nanorods for energy harvesting devices
Аннотация
It is represented the research of piezoelectric properties of nanorods and their application in energy harvesting devices. According to the simulation results with method of finite elements the value of electromechanic coupling coefficient of monolayer from ZnO nanorods is greater than one in compare to uniform film application. The sample manufacturing method consists of application of traditional microelectronic technique for shaping of top and bottom electrodes and also application of two-steps low-temperature chemical synthesis for ZnO nanorods. To provide acoustic perturbation of the sample the piezoceramic element is used in multilayer structure fixed on the glassceramic substrate. The results are obtained for two measurement modes, providing oscillations perturbation by rectangular pulses source and by harmonic generator. Obtained results demonstrate high efficiency of piezoelectric transformation for monolayer, which consists of ZnO nanorods that is possible to be used in different self-powered devices.
60-65
Electrothermal analysis of GaN power submicron field-effect heterotransistors
Аннотация
Physical processes and self-heating factors of in a power submicron field-effect heterotransistor have been considered. Mathematical models were proposed and the electrothermal analysis of heterotransistor parameters and characteristics was performed. The impact of thermal processes on parameters of the circuit model and the output frequency characteristics of submicron heterotransistor was shown on the basis of analysis of temperature fields. The relationship of the transistor thermal resistance as a function of its geometry and thermophysical parameters has been established.
66-73
Composites based on dielectric materials for microwave engineering
Аннотация
Composites provide possibilities to combine the properties of different materials in order to obtain materials with the necessary parameters (low loss, absorbing, reflective materials, etc.). According to their structure, composite materials are conventionally divided into the microtextures and macrotextures. In turn, these materials may be passive or active. The properties of passive composite materials are invariable, and the properties of active ones can be altered using different effects: electric, magnetic, thermal, etc. In this article we present the results of theoretical and experimental investigations of various microwave dielectric-based composite structures. Particular attention is given to high-Q microwave structures with electrical control.
74-82
Detection of COPD’s auscultative symptoms using higher order statistics in the analysis of respiratory sounds
Аннотация
In this paper we present the method for determination of the specific auscultatory diagnostic signs in patients with chronic obstructive pulmonary disease (COPD), which is based upon the utilization of the polyspectral analysis and the calculation of higher order statistics. The main stages of the method are the calculation and construction of the bicoherence function of the lung sound signal in order to find its maximal value. The visual and numerical estimations of the obtained maximum allow us to conclude the presence or absence in this lung’s audio signal of the artifact, which indicates the pathology. For more accurate results one needs to determine asymmetry coefficient and to perform the estimation of bifrequency corresponding to the maximal value of the bicoherence coefficient. The calculation of skewness and kurtosis coefficients of cross-correlation functions of lung sound signals, which were recorded simultaneously in four channels, allows us to reduce the sensitivity of the method to noise components. Therefore, by analyzing all proposed calculated characteristics and parameters one can conclude the presence or absence of the pathology in this audio signal.
83-88
Q-factor of tuned microstrip resonator
Аннотация
The paper presents research of quality factor in the micro-mechanically tunable microstrip resonator and its change in response to tuning. In the presented design unloaded quality factor increases about 10% during tuning due to reduction of dielectric loss in substrate’s medium and ohmic loss in metal electrodes. When total loss in the device is relatively small, loss mechanisms contribute additively, so complex effective permittivity can be used to account loss reduction and frequency tuning.
89-95