The article investigated the optical-frequency gas flow meter based on a transistor structure with negative differential resistance (NDR). A schematic diagram and design of an optical-frequency gas flow transducer that operates in the microwave range (0.85 to 1.5 GHz), which consists of a bipolar and field-effect transistor with a Schottky barrier, is proposed as a photosensitive element using a photoresistor. A mathematical model of an optical-frequency gas flow meter based on a transistor structure with negative differential resistance has been developed, which allows one to obtain the main characteristics of the transducer in a wide frequency range. Theoretically and experimentally, the possibility of controlling both the reactive component and the negative differential resistance from changes in control voltage and power is shown, it extends the functionality of optical transducers and allows linearization of the conversion function within (0.1 - 0.2)%. Experimental studies have shown that the greatest sensitivity and linearity of the conversion function of an opticalfrequency gas flow transducer lies in the range from 3 V to 3.5 V. The sensitivity of the developed optical-frequency gas flow transducer based on a transistor structure with NDR is 146 kHz/liter/hour, and the measurement error is ± 1.5%.
(Ga0.4In0.6)2Se3 thin films were deposited by thermal evaporation technique. Refractive index and extinction coefficient dispersions were obtained from the spectral ellipsometry measurements. The dispersion of refractive index is described in the framework of Wemple-DiDomenico model. The energy pseudogap and Urbach energy were determined from the optical absorption spectrum of (Ga0.4In0.6)2Se3 thin film. Optical parameters of (Ga0.4In0.6)2Se3 thin film and single crystal were compared.
At present, web-application is the most popular type of distributed systems. However, the problem of web-system optimization is still important. This paper considers the basic principles of high-loaded web-systems running and analyzes the main ways of its optimization. The methods of optimization on different levels are defined: client, server, and network. Experimental research has been conducted to explore the effectiveness of the proposed approaches. The experiments confirmed the improvement of the system characteristics. As the implementation of the optimization technique needs some resources, a research has been conducted to analyze the complexity of implementing approaches. Also the neural network has been developed that allowed to predict the results of web systems optimization.