bluuebunny/crossref_metadata_2025_split huggingface dataset:
A regularized shallow-water waves system with slip-wall boundary conditions in a basin: theory and numerical analysis
Authors: Israwi Samer , Kalisch Henrik , Katsaounis Theodoros , Mitsotakis Dimitrios 
Published: December 2021

Abstract
The simulation of long, nonlinear dispersive waves in bounded domains usually requires the use of slip-wall boundary conditions. Boussinesq systems appearing in the literature are generally not well-posed when such boundary conditions are imposed, or if they are well-posed it is very cumbersome to implement the boundary conditions in numerical approximations. In the present paper a new Boussinesq system is proposed for the study of long waves of small amplitude in a basin when slip-wall boundary conditions are required. The new system is derived using asymptotic techniques under the assumption of small bathymetric variations, and a mathematical proof of well-posedness for the new system is developed. The new system is also solved numerically using a Galerkin finite-element method, where the boundary conditions are imposed with the help of Nitsche’s method. Convergence of the numerical method is analysed, and precise error estimates are provided. The method is then implemented, and the convergence is verified using numerical experiments. Numerical simulations for solitary waves shoaling on a plane slope are also presented. The results are compared to experimental data, and excellent agreement is found.
Theoretical studies of low-frequency Alfvén modes in tokamak plasmas
Authors: Ma Ruirui , Chen Liu , Zonca Fulvio , Li Yueyan , Qiu Zhiyong 
Published: December 2021

Abstract
The linear wave properties of the low-frequency Alfvén modes (LFAMs) observed in the DIII-D tokamak experiments with reversed magnetic shear (Heidbrink et al 2021 Nucl. Fusion
61 016029) are theoretically studied and delineated based on the general fishbone-like dispersion relation. By adopting representative experimental equilibrium parameters, it is found that, in the absence of energetic ions, the LFAM is a reactive-type kinetic ballooning mode instability with a dominant Alfvénic polarization. More specifically, due to diamagnetic and trapped particle effects, the LFAM can be coupled with the beta-induced Alfvén-acoustic mode in the low-frequency region (frequency much less than the thermal-ion transit and/or bounce frequency) or with the beta-induced Alfvén eigenmode in the high-frequency region (frequency higher than or comparable to the thermal-ion transit frequency), resulting in reactive-type instabilities. Moreover, the ‘Christmas light’ and ‘mountain peak’ spectral patterns of LFAMs as well as the dependence of instability drive on the electron temperature observed in the experiments can be theoretically interpreted by varying the relevant physical parameters. Conditions for when dissipative-type instabilities may set in are also discussed.
Geometry effects in topologically confined bilayer graphene loops
Authors: Benchtaber Nassima , Sánchez David , Serra Llorenç 
Published: December 2021

Abstract
We investigate the electronic confinement in bilayer graphene by topological loops of different shapes. These loops are created by lateral gates acting via gap inversion on the two graphene sheets. For large-area loops the spectrum is well described by a quantization rule depending only on the loop perimeter. For small sizes, the spectrum depends on the loop shape. We find that zero-energy states exhibit a characteristic pattern that strongly depends on the spatial symmetry. We show this by considering loops of higher to lower symmetry (circle, square, rectangle and irregular polygon). Interestingly, magnetic field causes valley splittings of the states, an asymmetry between energy reversal states, flux periodicities and the emergence of persistent currents.
Probing the Purcell effect without radiative decay: lessons in the frequency and time domains
Authors: Lindel Frieder , Settembrini Francesca Fabiana , Bennett Robert , Buhmann Stefan Yoshi 
Published: December 2021

Abstract
The effect of cavities or plates upon the electromagnetic quantum vacuum are considered in the context of electro-optic sampling (EOS), revealing how they can be directly studied. These modifications are at the heart of e.g. the Casimir force or the Purcell effect such that a link between EOS of the quantum vacuum and environment-induced vacuum effects is forged. Furthermore, we discuss the microscopic processes underlying EOS of quantum-vacuum fluctuations, leading to an interpretation of these experiments in terms of exchange of virtual photons. With this in mind it is shown how one can reveal the dynamics of vacuum fluctuations by resolving them in the frequency and time domains using EOS experiments.
Development of flow control methods in free and impinging jets
Authors: Shevchenko A K , Yakovenko S N 
Published: December 2021

Abstract
Submerged and impinging jets with harmonic perturbations added to the inlet velocity profile and with nozzle vibrations are simulated numerically at different Reynolds (Re) and Strouhal (St) numbers by solving the Navier–Stokes equations. The effects of Re, St and forcing amplitudes on flow behavior and jet splitting phenomena are studied.
Computational and experimental evaluation of heat transfer intensity in channels of complex configuration for gas flow with different levels of turbulence
Authors: Plotnikov L V , Zhilkin B P , Brodov Yu M , Osipov L E 
Published: December 2021

Abstract
Disclosure of the physical mechanism of the influence of the turbulence intensity of gas flows on the heat transfer level in pipes of different configurations is an urgent task in the field of heat and power engineering. A brief overview of the literature on this topic is given in the article. A description of the boundary conditions for modeling is presented. The main characteristics of the experimental stand and measuring instruments are described. The purpose of this study is to study the effect of the initial turbulence level of a stationary gas flow on the heat transfer intensity in long pipes with different cross sections. The study is carried out using numerical simulation. The simulation results are qualitatively confirmed using experimental data. The values of the local heat transfer coefficient are shown to increase from 5 to 17% with increasing turbulence intensity (from 2 to 10%) in pipes with different cross sections. The heat transfer intensity in a triangular pipe is found to increase up to 30% compared to a round pipe. It is revealed that there is an up to 15% suppression of heat transfer in a square pipe compared to a round pipe. The data obtained may be useful for the design of flow paths and gas exchange systems for power machines and installations.
Investigation of the influence of controls on the flow around the UAV model
Authors: Alpatskiy N S , Pavlenko A M , Bykov A V , Zanin B Y 
Published: December 2021

Abstract
Studies of the flow structure were performed on a trapezoidal UAV model. The experiments were carried out in a wind tunnel at subsonic speeds. The method of soot-oil visualization was used to obtain a picture of the flow around the model. The experiments were made at different angles of attack, as well as at different deflections of the ailerons on the model. The peculiarity of the work is that the experiments were conducted at full-scale (flight) Reynolds numbers.
The effect of microtexture on the liquid flow over the sheets
Authors: Perepelitsa B V 
Published: December 2021

Abstract
This work considers the method of the corrugated sheet arrangement near the column wall with the aim to limit liquid fall on the wall and increase liquid concentration in the near-wall area. Experiments were carried out at the corrugated Koch 1Y packing sheets for various liquid flow rates. This report presents experimental results on the character of liquid flow near the edge of corrugated sheets and the effect of the middle sheet shift from the edge of the packing. The ribs of this sheet are directed downward to the edge of the packing. Test was performed for two positions of the middle sheet: to study the effect of microtexture orientation at the sheet, whose ribs are directed downward to the packing edge, on liquid distribution under the packing. Experiments were carried out for liquid flow rates of 1-12 ml/s.
Control of flow separation over a circular cylinder using synthetic jet
Authors: Lebedev A. S. , Sorokin M. I. , Markovich D. M. 
Published: December 2021

Abstract
The development of methods of active separation flow control is of great applied importance for many technical and engineering applications. Understanding the conditions for the flow separation from the surface of a bluff body is essential for the design of aircrafts, cars, hydro and gas turbines, bridges and buildings. Drag, acoustic noise, vibrations and active flow mixing depend drastically on the parameters of the vortex separation process. We investigated the possibility of reducing the longitudinal length of a reverse-flow region using the method of «synthetic jet» active separation flow control. The experiment was carried out on a compact straight-through wind channel with a 1-m long test section of a cross-section of 125x125 mm. The jet was placed at the rear stagnation point of a circular cylinder. The Reynolds number, based on the cylinder diameter and the free-stream velocity, was 5000 and the von Kármán street shedding frequency without the synthetic jet was equal to 64.8 Hz. For the first time, for such a set of parameters, we applied high speed PIV to demonstrate that the injection of the synthetic jet into the cylinder wake region leads to a significant reduction in the longitudinal length of the reverse-flow region.
Ultra-dispersed particles of water-soluble and water-insoluble substances formed from gas-droplet flows
Authors: Prikhodko V G , Yarygin V N , Yarygin I V 
Published: December 2021

Abstract
The work is devoted to the experimental study of the ultra dispersed particles formation process, which is essentially a fundamental problem of heat and mass transfer in gas-droplet flows under phase transformation conditions. Various methods of generating and controlling the gas-droplet flow parameters are considered. The description of the created equipment and diagnostic methods for studying gas-droplet flows is given. The particle size distribution functions are obtained using an aerosol particle spectrometer. The possibility of controlling the parameters of ultrafine particles of water-soluble and water-insoluble substances (medications) formed under evaporation of microdroplets of solutions and suspensions is shown experimentally. An attempt to reconstruct the distribution functions of microdroplets and their average dimension from measurements of the parameters of ultrafine particles formed after complete evaporation of the droplets is made.
Numerical study of cutting transport using aerated drilling fluids
Authors: Zhigarev V A , Zazulya S O , Minakov A V , Neverov A L 
Published: December 2021

Abstract
The paper deals with drilling fluid flow in a horizontal well during its drilling. As part of this work, rheological parameters of water-based drilling fluid with the addition of polymers and a foaming agent were used. Cuttings transport was studied at different degrees of foam aeration. Besides, the paper presents the study of the effects of drilling fluid flow, as well as the rotation of drill pipes on the cuttings transport.
Analysis of different factors on the features of thermal destruction of a fuel pin
Authors: Usov E V , Saikina T A , Chuhno V I 
Published: December 2021

Abstract
The presented work studies the influence of various factors that affect the specific features of fuel pins melting. For this purpose, fuel pins with different geometries and energy release are considered. Numerical simulation of melting is carried out using a program module for calculating the destruction of fuel rods. Comparison with theoretical calculations is made. The analysis of the convergence of calculations with respect to the time step value and the number of calculated cells along the radius and height is carried out. As a result of work with the use of numerical methods, the characteristic times of destruction of fuel elements during an accident with a loss of coolant flow rate (an accident of the ULOF type) and the dependence of weight loss on time are obtained under various conditions.
Measurement and study of thermophysical properties of nanofluids with carbon nanotubes
Authors: Rudyak V Ya , Dashapilov G R , Shupik A A 
Published: December 2021

Abstract
This article is devoted to the study of the thermophysical properties of nanofluids with single-walled and multi-walled carbon nanotubes (CNT). Their weight concentration varied from 0.05 to 0.2%. Nanofluids, based on ethylene glycol and water, were studied. Dispersants were also used. The diffusion of CNT had been systematically investigated by the method of dynamic light scattering and their effective hydrodynamic dimensions were determined. The rheology and viscosity of all nanofluids were studied. It is shown that nanofluids are either pseu-doplastic or viscoplastic. Their rheology changes with increasing CNT concentration and temperature. However, in all cases, the viscosity of nanofluids with single-walled CNTs is signifi-cantly higher than that of nanofluids with multi-walled CNTs. In the last part, the electrical conductivity of all these nanofluids and the dispersants effect on it are investigated.
Degradation processes in tungsten filaments at high temperatures
Authors: Zakharov Y A , Ghots S S , Sharipov T I , Bakhtizin R Z 
Published: December 2021

Abstract
Degradation processes in tungsten filaments of lighting lamps under normal operating conditions are experimentally studied. The duration of each measurement in continuous mode is about 18 hours. To increase the measurement accuracy, subtraction (compensation) of the constant component of the voltage is used. To compensate for the constant component of the voltage, a low noise reference DC voltage source is used. Using this scheme allowed decreasing the influence of the inherent noise of power supplies without suppressing degradation processes. It is shown that the relative change in resistance during the measurement does not exceed 2.8·10−3. It is also shown that the joint influence of voltage fluctuations of power supplies and low noise reference voltage source on the measurement results corresponds to a relative change in a resistance equal to 2.8·10−4. The study of degradation processes can be used to assess the reliability (and durability) of products in electrical engineering and radio electronics.
Numerical study of a case of the free discharge of water through the turbine with a braked runner
Authors: Platonov D V , Minakov A V , Sentyabov A V 
Published: December 2021

Abstract
The paper presents a numerical study of the free discharge of water through the turbine with a braked runner. The simulation was carried out for a unit of a full-scale Francis turbine. The finite volume method was employed for unstructured meshes using the DES method. The simulation results show the flow structures, integral characteristics, and pressure pulsations in the flow path. The analysis of the applicability of this approach to real conditions is carried out.
1D modelling and PID control of helicopter Diesel engine rotational speed in torque changes
Authors: Magryta P 
Published: December 2021

Abstract
The article discusses the results of simulation tests concerning the operation of a diesel engine for a light helicopter. The tests were carried out in the AVL Boost software which is used to analyze dynamic phenomena in internal combustion engines. The research object was a newly designed diesel engine of a V8 structure and a power of 330 kW. This engine was designed to be used in the construction of a light class helicopter. The created one-dimensional simulation model included all the main engine components as well as the connection to the helicopter main transmission and the helicopter rotor. The tests consisted in selecting the P value in the PID controller used to control the amount of fuel injected into the engine. The change in the P value indirectly influenced the reaction of the engine to a change in power and torque during horizontal flight of a helicopter. These changes were introduced by changing thrust torque in the helicopter rotor. The fuel injection regulator was designed to maintain a constant engine rotational speed. The maximum speed deviations from the nominal speed of the engine operation due to both increasing and decreasing speed were analyzed. Additionally, the sum of the deviation values was analyzed until the rotational speed of the tested object stabilized. The results showed that the change of the P parameter affects all the analyzed parameters of the engine operation; however, the minimum deviation values for each parameter occur at non-equal PID settings, which makes it difficult to clearly indicate the appropriate value of the P element.
Internet of Things as an element of the frost protection system in orchards
Authors: Awtoniuk M , Nowakowski T , Chlebowski J , Świętochowski A , Dąbrowska M , Klonowski J , Sypuła M , Strużyk A , Wrona D , Kowalczyk W , Bąk K 
Published: December 2021

Abstract
Frosts cause serious damage to fruit and vegetable crops. In Poland, temperature decreases, and the occurrence of inflow (advective) frosts most often fall during the flowering period, i.e., in a phase extremely important for the development of the plant. For orchards, this causes the inflorescences of early flowering trees (cherries, plums and certain varieties of apple and pear trees) to freeze. A modern idea for reducing frost losses in orchards is to heat the air with mobile heaters. Protection by these machines consists of passing using an agricultural tractor in rows of trees or shrubs and heating and mixing the air. The problem that farmers may encounter during frosts is the awareness of when exactly such a weather condition occurs in their orchard. Weather forecasts are not detailed and usually apply to the entire region. Dangerous temperature declines below the critical minimum can occur locally and are also conditioned by geographical location and terrain diversity. The aim of the article is to present a measuring system that allows the construction of an individualised temperature model taking into account the unique shape of the orchard surface. The system is made in Internet of Things technology using long-range radio communication protocol LoRaWAN. Data from distributed measurement sensors are processed on a network server and displayed as a final application. The task of the system is to monitor the current situation in the orchard and to notify the farmer of the need to initiate a protective procedure. The operation of the system also supports the efficient use of mobile heating machines. The system facilitates the location of the areas in the orchard with the lowest temperature, as well as provides feedback on temperature changes inside the treetops caused by the passage of the mobile heater.
Finite element modeling of coupling characteristics of directional coupler for multiplexer and de-multiplexer application
Authors: Mohammed M 
Published: December 2021

Abstract
Numerical simulation of directional coupler that is based on the finite element method was conducted using the COMSOL Multiphysics software. The distributions of electric field and power flow of light propagates in two cores of directional coupler were analyzed. The results showed the dependencies of coupling length and maximum transfer power between cores on the cores separation and the wavelength, the characteristic of a subwavelength directional coupler can be used for photonic integrated circuits. Asymmetric directional coupler was also designed by changing in the device dimension, as the core width. The variation of coupling length with the core width were analysed. It was found that the power switching between cores is reduced when introducing a small difference in the one core width of directional coupler, followed by increased coupling length. At the same time, the coupling length can be decreased efficiently by increasing the difference in one core width; therefore, a directional coupler with large core width is more convenient to reduce the power switching between cores than the smaller core width. This study is useful for determining the coupling characteristics between the cores that may be used as a platform for future photonic integrated circuits in optical communication systems.
Water efficiency management systems for transport drinking water supply
Authors: Cvelihárová D , Pauliková A 
Published: December 2021

Abstract
The quantity of management systems standards (MSSs) is increasing every year. Standards are significantly associated with common requirements and differences for many providers of services as well as for manufactures. The drinking water supply management system is certainly one of the important services. The aim of this article is to introduce a basic application of management system (MS) using visual management. The standard applied in a model, defined as a complex solitaire or “singlet”, is the Water Efficiency Management Systems (WEMS) standard. Visualised model is built by creating clusters using a software program designated for Small World Networks. This phase is preceded by the compilation of Excel spreadsheets, where requirements are divided into common and specific ones. The resulting cluster of selected areas includes the context of organizations that provide services, considering the common and specific requirements of interesting parties, managing their leadership, planning, support, operation, performance evaluation and improvement. It could be very useful to extend the cluster by another standard depending on the needs of the drinking water supplier and the transport piping systems at the site. This approach to management systems intensively clarifies managerial decision-making processes related to the implementation of the WEMS.
Climate change, fires and their impact on safety
Authors: Heinzová Z , Kubrická K , Podkul M , Pokorný J 
Published: December 2021

AbstractOur planet is warming due to climate change. Along with this, the incidence of fires is increasing. Fires negatively affect the environment. Fire prevention is one of the safety priorities in the Czech Republic and in the world. One aspect of safety is the evacuation of people, animals and potentially property. The paper will present a case study of escape route ventilation.
Technical condition of sewer networks in the Czech Republic
Authors: Hlustik P , Singrova V 
Published: December 2021

Abstract
This article offers a comparison of the detected defects in sewerage systems operated by water companies and by self-operators, determines their quantity and classifies them into individual categories. The determination of the number of the defects at self-operators is evaluated on the basis of performed camera inspections and compared with data provided by the water company.
Use of vegetation for the removal of pollutants from wastewater as an alternative environmental technique for wastewater treatment
Authors: Junakova N , Junak J 
Published: December 2021

Abstract
The paper focuses on the evaluation of the use of vegetation for the removal of contaminants from wastewater through vegetation-based wastewater treatment plants. Subsequently, the specific efficiencies of wastewater treatment using a selected vegetation-based wastewater treatment plant are evaluated. The results show that vegetation-based wastewater treatment plants generally work at relatively high treatment efficiency, but one of the main factors influencing the treatment efficiency is the values of pollution indicators at the inflow to the wastewater treatment plant.