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Distributed stress and temperature measurements along the active fiber of operating laser is a new dimension of laser systems analysis. Thermal loading of the active fiber can lead to the switching of the laser operation mode [1] , gain spectrum changing, and modes instability appearance. To realize distributed temperature measurements one can use external thermal camera (thermograph) or optical backscatter reflectometer. The first one measures the temperature of the fiber surface, and the second one measures temperature directly in the fiber core. By using optical backscatter reflectometry spatial resolutions down to ~10 microns and temperature resolution of ~0.1 °C are achieved [2] , which allows high-performance analysis of fiber-optic schemes. In [3] distributed temperature measurement in the active medium of a high-power ytterbium-doped fiber laser is demonstrated using this approach. On the other hand, a similar or greater temperature difference can be measured in fibers doped with active ions and pumped with a large quantum defect. Holmium (Ho 3+ ) can become the most attractive ion because it can be pumped at 1.125–1.15 µm, while emitting wavelength is around 2 µm. In this work, we study the temperature distribution in Ho-doped DBR fiber lasers pumped at a wavelength of 1.125 µm. We use LUNA OBR 4600 reflectometer with down to 1 mm spatial resolution [2] and the IR-thermograph IRTIS-2000 ME to measure temperature distribution along a fiber specimen.

The article analyzes industrial networking ecosystems that have added intelligence to manufacturing equipment, processes, and control. The features of the development of Functional Networking Components (FNC) are presented. FNC have the ability to receive and process information (the presence of a computer with network ports), have a physical nature (including hardware and software resources) and can affect the environment,. The structure of the FNC, which determines the function of these devices, and its main elements are considered. The article analyzes cybersecurity problems and ways to solve it. The use of digital matrices (FPGA) as part of the FNC hybrid calculator makes it possible to solve some security problems successfully. An example of the development and simulation of the FNC functional module, a combined generator of powerful ultrasonic vibrations, is considered. The network capabilities of FNC for switching and routing information packets are noted. FNC can be used as an element of a telecommunications network.

This article describes the behaviour of DASH adaptive streaming technology (which provides the ability to deliver streaming media content over the Internet using HTTP) in a closed network environment that can be replicated across the network. The experiment can be divided into two steps: at first, we set up a web server that hosts DASH files in the Google Cloud Virtual Machine. In the second step, we perform client-side network bandwidth (Regular 2G, Good 2G, Regular 3G, Good 3G, Regular 4G/LTE) changes and analyse the behaviour of the protocol: how Video Buffer, Video Bitrate and Video Latency are changing over time. As a result, based on the analysis and the data obtained, the advantages and disadvantages of DASH technology were identified, as well as which kind of im-pact has a 5% packets drop rate on the protocol in the short term.

This paper presents a cognitive search strategy that enables new possibilities to study autonomous search for an emitting source in an urban environment through the efficient gathering of location information at temporal and spatial granularities not possible with classical search methods. In this study, we develop an online unmanned aerial vehicle (UAV) path-planning strategy for autonomous search and localisation of emitting source. The UAV is equipped with Receiver Signal Strength (RSS) sensors to localise stationary radio frequency (RF) emitter. A high fidelity non-linear measurement model of RF propagation in urban environment is adopted for this purpose. Source localisation is carried out using a particle filtering method, while a partially observable Markov decision process is applied for dynamic path planning. This approach allows autonomous navigation of a UAV in a direction of maximum information gain to locate the emitter and reduce exploration time. We also employ the concept of search termination criteria to maximise the accuracy of the source localisation and validate the effectiveness of the proposed online approach through extensive simulations. The numerical results show the feasibility of the proposed approach.

In this paper we present various configurations of erbium DBR lasers based on seven-core fiber. By using femtosecond writing technique, it is possible to fabricate fiber Bragg gratings (FBGs) in selected cores of multicore fibers (MCF) at a certain transverse and longitudinal locations in a fiber, thus allowing for fabrication of advanced reflecting elements. Different schemes of tunable lasers are presented based on both uniform and chirped FBGs.

We consider the problem of estimating unknown input forces on structural systems using only noisy acceleration measurement data. This is an important task for condition monitoring, for example, to predict fatigue damage in a structure's body or to reduce transmission of vibrations in marine vessels. In this paper, we propose a new idea to estimate an input force with a sinusoidal form by formulating a force identification problem without a direct feed-through system. Consequently, the minimum variance unbiased (MVU) filter can be implemented coupled with a fast Fourier transform algorithm to estimate unknown input forces accurately in real-time. Moreover, when the input force is completely unknown, the ensemble sampling method combined with an augmented Kalman filter can be formulated to significantly reduce computation time. Experimental results confirm the effectiveness of our proposed methods and show that the formulations investigated outperform other state-of-the-art methods in term of computational cost whilst not compromising estimation performance.

The effectiveness of low-frequency ultrasound depends primarily on the type of ultrasonic cavitation. The paper deals with criterion based on shock waves pressure due to cavitation bubble collapse. It is shown that shock wave pressure can be used as a criterion for the erosive activity of cavitation. Frequency dependence of erosive activity is investigated. The results prove significant influence of frequency for erosion activity at constant emitter oscillation amplitude and weak influence of frequency for erosion activity at constant sound pressure amplitude.

The paper is devoted to the numerical modeling of light scattering in the cavitation region and the study of the possibility of using the amplitudes of subharmonic components of cavitation noise for indirect determination of cavitation intensity. The results of numerical simulation of light scattering in the cavitation area and their comparison with the results of erosion tests showed that the amplitudes of subharmonics at frequencies 1/2 and 1/3 of the ultrasound frequency can be used as feedback signals to maintain the maximum cavitation intensity in real time.

In this paper the digital antenna array based radar Ku-band receiver design results were represented. The radar system calculation results were used to generate receiver requirements. It was decided to design 160-channel receiver antenna array to obtain the required radar range. Each receiver channel is independent superheterodyne receiver with common heterodyne signal. The presented device consists of two parts: RF-frontend and digital signal processing core. Digital antenna array based radar ranging and direction-finding precision depends on receiver sensitivity. The receiver sensitivity depends on noise factor and effective number of bits of analog-to-digital converter.

Decision-making is one of the essential functions of any manager. The means of visualization play a crucial role in supporting the manager in the decision-making process. This paper discusses the visualisation of information risks based on integral indicators. It provides a description of a mathematical model of the method of dynamic meta-anamorphosis and an example of its practical implementation. The advantages of using a hybrid approach to the development of dynamic meta-anamorphosis are discussed.

An analysis of the methods for calculating the dependence of the deflection of multilayer round membranes on the applied overpressure was carried out. To compare theoretical calculations with experimental data, as an example, we considered a round membrane based on the structure Al/SiO2/Al with a total thickness of 2.5 μm. Using the COMSOL Multiphysics and ANSYS software packages, we calculated the stress distribution in the radial and tangential directions, the distribution of equivalent von Mises stresses over the membrane area, and also compared the obtained numerical values of mechanical stresses with the corresponding analytical estimates. We compared the deflection of the membrane depending on the applied overpressure obtained using software packages, analytical estimates and records obtained experimentally using an optical profilometer. It was shown that, when studying the deflection of membranes, which significantly exceeds the thickness of the membranes, to predict the deformations expected in the experiment, analytical relations obtained taking into account the presence of tensile forces, radial displacement, and elongation of the median plane should be used.