bluuebunny/crossref_metadata_2025 huggingface dataset:
News from the BIPM laboratories—2020
Authors: Wielgosz Robert , Tavella Patrizia , Judge Steven , Stock Michael , Milton Martin
Published: January 2021

In order to fulfil its mission to ensure and promote the global comparability of measurements, the BIPM operates laboratories in the fields of physical metrology, time, ionizing radiation and chemistry. These laboratories act as centres for scientific and technical collaboration between member states providing capabilities for international measurement comparisons on a shared cost basis. They coordinate international comparisons of national measurement standards agreed to be of the highest priority, and they establish and maintain appropriate reference standards for use as the basis of key international comparisons at the highest level and provide selected calibrations from them. The BIPM sustained all of its key activities throughout the periods of confinement resulting from the global pandemic in 2020 including: the publication of Circular T each month, the annual World Metrology Day celebrations and the launch of the new key comparison database (KCDB 2.0). Several activities were brought forward in the work programme including the automation of data handling in the International Reference System (SIR) for radionuclide metrology and on-line technical exchanges and capacity building initiatives. The BIPM has also worked to understand how best to support the National Metrology Institutes (NMIs) as a ‘new normal’ emerges. As a first step, the NMI ‘COVID action’ repository was implemented and two pilot studies were launched by the CCQM on the measurement of SARS-CoV-2 and SARS-CoV-2 antibodies. New ways have been developed to support the International Committee for Weights and Measures (CIPM) consultative committees on-line. For example, during 2020 a total of 70 video meetings were held for the CCQM, with similar trends for other CCs. In the following sections, we provide highlights of the work the laboratories have undertaken during 2020.
Axial forces in multistage back-to-back pumps
Authors: Kovtun O M , Tverdokhleb I B , Lugova S O , Makivskii O S , Lugovii O L
Published: January 2021

Since the pressure of the pumps for the oil and gas industry and feed water pumps for the thermal and nuclear power plants are increasing and at the same time the production costs need to be reduced, the demands for development of the modern multistage centrifugal pumps are increased. An enlargement of stage numbers results in an increase in the distance between the bearings and as a result the shaft deflection increases. Also, a large number of stages leads to occurrence of a significant axial force acting on the pump rotor. These issues are solved by applying a back-to-back design with a throttling bush between the groups of stages. An arrangement with such throttling bush results in an additional axial force due to the different directions of leakage in the channels (side wall gaps) between the main disks of the last impellers of both stage groups and stator elements. Therefore, the design of a throttling bush with special balancing holes was proposed. This paper examines the processes occurring in the throttling bush and compares the operating parameters for two design options-with special balancing holes, and without them.
Numerical study of the centrifugal contra rotating blade system
Authors: Kulikov A A , Ratushnyi A V , Kovaliov I A , Mandryka A S , Ignatiev A S
Published: January 2021

The manuscript presents the results of a numerical study of a centrifugal contra rotating blade system based on a low-speed impeller (ns = 65). They were carried out to assess the possibility of using a contra rotating blade mesh operating in conjunction with a standard centrifugal impeller as a method of intensifying the transmission of energy to a fluid. The designs of the systems under consideration and their pressure and energy characteristics are presented.
Creation a universal technique of predicting performance curves for small-sized centrifugal stages of well oil pump units
Authors: Antonenko S , Sapozhnikov S , Kondus V , Chernobrova A , Mandryka A
Published: January 2021

The work provided is a continuation the development of research work on the process of pumping high-viscosity liquids and is aimed at creating a universal technique of recalculating the performance curves of dynamic small-sized pumps from water to high-viscosity liquid. The practical need to develop such a technique became relevant after obtaining different results when using existing methods of predicting performance curves for hydrodynamic oil well pumps. The expediency of carrying out studies aimed at clarifying the scope of the technique for calculating the work parameters of a well oil centrifugal pump, which is being developed, is substantiated, and more thorough analysis of the structure of conversion coefficients taking into account the scale factor and flow regime in the hydraulic flow parts of the studied pumps.
The ways to increase the efficiency of the stage of low specific speed
Authors: Puzik R V , Kovalyov I O , Ratushnyi O V , Dzafarov T V , Petrenko S S
Published: January 2021

The paper raises the question of the possibility of reducing the energy loss of the stage of the centrifugal pump on the disk friction, the relative value of which for the stages of low and ultralow speed can be a significant proportion (up to 40%) of all losses. This is seen as one of the effective ways to increase the efficiency of such stages of centrifugal pumps.
The influence of a pipe impeller external shape on the pump parameters
Authors: Skrzypacz J , Szulc P
Published: January 2021

Multi-piped impellers (name proposed by the authors) represent an innovative approach to the design of rotodynamic pumps operating at the specific speed of nq<10. In such a construction the energy increase is caused by the flow of liquid through the internal impeller passages as well as by an external flow around the passages, and sensible designing of such a construction is extremely difficult. The study investigates the flow phenomena and impact of the external shape of a multi–pipe impeller on the efficiency of the process of energy transfer into liquid. The main research method involves computational fluid dynamics (CFD) simulations.
Cyclic deformation of separating tape in electromagnetic rolling pump
Authors: Prokopenko D , Shatskyi I , Vorobiov M , Ropyak L
Published: January 2021

The purpose of the paper is to justify a substantiation of the possibilities of trouble-free operation of de-axial pump based on the Rolamite mechanism with rolling bodies. The use of an electromagnet as a drive makes it possible to transfer the rotation into a closed space as well as abandon bearings and seals. The flexible tape allows reducing the slip friction and getting separate cameras with the possibilities to pump two substances at a time. The structure of the strain cycle of combined stretching and bending during rotation is investigated in details for the separating tape. The thickness of the tape which provides the specified durability of operation is determined.
Thrust bearing with fluid pivot
Authors: Martsynkovskyy V , Liubchenko K , Prokopenko A , Lazarenko A
Published: January 2021

This article describes the conditions arising from the operation of compressor and pumping equipment using traditional thrust bearings with mechanical support and leveling linkage system, which negatively affect the operation of dynamic machines in general and the thrust bearing in particular. The possibility of using the hydrodynamic pressure of an oil wedge for hydrostatic support in a thrust bearing was considered, and what positive effects could arise. The working design of a thrust bearing with fluid pivot and a calculation model are shown, allowing to take into account the hydrostatic oil film when determining the characteristics of the bearing. The results of the first tests of the bearing on the stand allow us to evaluate the performance of the design and determine further improvement and optimization of the design of the bearing with fluid pivot.
Effect of pump duty on natural frequencies and modes of its rotor vibration
Authors: Yashchenko A , Verbovyi A , Rudenko A
Published: January 2021

This article deals with the development of more accurate models of high-performance pump units which work in a wide range of capacities. The pump operating range can sometimes reach from 20% Qr up to 130% Qr (Qr is the rated capacity). With changes of the pump duty, pressure difference between gap seals is changing as well. This leads to changes of hydrodynamic characteristics of gap seals. In particular, changes in radial stiffness of gap seals have an effect on the rotor dynamics. The task of creating the model has been performed in Modal Analysis subprogram of the ANSYS Workbench multifunctional software complex. Developed model demonstrates a dependence between pump duty and dynamics of the rotor. The nature and extent of influence of pump feed mode on the rotor dynamics has been determined. Data charts of this dependence have been obtained.
Changes in the dynamics of the output characteristics of mechatronic systems with planetary hydraulic motors
Authors: Voloshina A , Panchenko A , Titova O , Panchenko I
Published: January 2021

A structural-functional diagram of a dynamic model of a mechatronic system with a planetary hydraulic motor is proposed. The initial conditions for the simulation of transients occurring in a mechatronic system with a planetary hydraulic motor are substantiated. The design parameters of the distribution system, which determine the unevenness of the output characteristics of the planetary hydraulic motor, are also substantiated. The influence of the design features of a serial and modernized hydraulic motors on the dynamic processes of the mechatronic system is investigated. It is established that fluctuations in the flow area of the distribution system of a serial hydraulic motor cause pulsations of torque on the hydraulic motor shaft and pressure in the discharge line of the mechatronic system. At the time of acceleration, significant pulsations of the flow of working fluid through the safety valve are observed, and as a result, pulsations of the flow of working fluid through the hydraulic motor. Elimination of fluctuations in the flow area of the distribution system of the upgraded hydraulic motor allows you to stabilize the values of pressure, torque and flow rate of the working fluid throughout the study of the acceleration process. Under steady-state operation, fluctuations in the area of the passage section of the distribution system do not affect the nature of the change in the shaft speed, either of the modernized or serial hydraulic motors.
Vibration resistance of HST 90 hydrostatic transmission
Authors: Ivanov M , Pereyaslavskyy O , Shargorodskiy S , Hrechko R , Mazurenko V , Holovko S
Published: January 2021

Hydrostatic transmissions, which are usually used in the drives of mobile machines, have recently been actively used in drives of other working bodies of machines. For example, in drives of mixers of concrete carriers, drives of working bodies of agricultural machines - straw cutters, etc. This area of use of hydrostatic transmissions is actively developing. The successful solution of this problem is prevented by the occurrence of vibrational operating modes while reducing inertial and technological loads, and in some cases leads to significant disturbances in the operation of machines. Using computer simulation of the hydrostatic transmission, the influence of the inertial and technological loads, as well as the parameters of the hydraulic system, the conditions for the occurrence of vibrational modes of its operation are analyzed. Based on the results obtained, measures have been developed to improve the design of measures and shunt valves, which allow to exclude vibrational modes of operation with a significant expansion of the range of variation of inertial and technological loads.

The results of a bench simulation of hydrostatic transmissions with advanced valves, conducted in the laboratories of PJSC Gidrosila APM (Kropyvnytskyi), confirmed the effectiveness of the proposed measures. The enterprise has begun mass production of hydrostatic transmissions of an improved design.
Long-term exposures to ambient PM1 and NO2 pollution in relation to mild cognitive impairment of male veterans in China
Authors: Chen Gongbo , Tan Jiping , Yan Lailai , Li Nan , Wang Luning , Li Na , Mai Lei , Zhao Yiming , Li Shanshan , Guo Yuming
Published: January 2021

Mild cognitive impairment (MCI) is an intermediate stage of cognitive decline between normal ageing and dementia or Alzheimer’s disease in the elderly. However, evidence is very limited in China for the association between air pollution and MCI. This study aims to examine the associations of long-term exposure to air pollution and MCI, using data from the Chinese Veteran Clinical Research Platform. A national investigation on mental health of veterans was conducted in 277 veteran communities in 18 cities across China. In total, 1,861 MCI cases and 3,188 controls were randomly selected using a stratified cluster sampling strategy from December 2009 to December 2011. Participants’ cognitive function was first assessed using the Mini Mental State Examination and the Montreal Cognitive Assessment in the Chinese version, and then further confirmed by clinical examination. Participants’ mean exposures to PM1 (particulate matter with aerodynamic diameter ⩽1 μm) and NO2 (nitrogen dioxide) during the 3 years before the investigation were estimated using satellite remote sensing data, meteorological variables and land use information. The association between historical exposure to air pollution and MCI was examined using Logistic regression. After controlling for individual-level and regional-level confounders, we found historical exposures to PM1 and NO2 significantly increased the risk of MCI. The odds ratios (ORs associated with per 10 µg m−3 increase in air pollution) and 95% confidence intervals for PM1 and NO2 were 1.08 (1.04, 1.13) and 1.07 (1.02, 1.13), respectively. In the multi-pollutant models, higher OR for PM1 while lower OR for NO2 were observed compared to single-pollutant models. High levels of PM1 and NO2 pollution significantly increased the risk of cognitive decline among male veterans in China. Given the causal air pollution-MCI relationship, good air quality may help to reduce the burden of mental disorders among elderly veterans in China.
Temporal correlation beyond quantum bounds in non-Hermitian PT- symmetric dynamics of a two level system
Authors: Varma Anant V , Mohanty Ipsika , Das Sourin
Published: January 2021

We study the dynamics of a non-Hermitian PT- symmetric Hamiltonian of a two level system (TLS) which has real eigenvalues. Within the framework of Hermitian quantum mechanics, it is known that maximal violation of Leggett–Garg inequality (LGI) is bounded by K
3 = 3/2 (Luder’s bound). We show that this absolute bound can be evaded when dynamics is governed by non-Hermitian PT- symmetric Hamiltonians with real eigenvalues. Moreover, the extent of violation can be optimized to asymptotically approach the algebraic maximum of

K

3

max

=
3

, which is otherwise observed for Hermitian Hamiltonian with infinite dimensional Hilbert space. The extreme violation of LGI is shown to be directly related to the two basic ingredients: (i) the Bloch equation for the TLS having a non-linear terms which allow for accelerated dynamics of states on the Bloch sphere exceeding all known quantum speed limits of state evolution; and (ii) quantum trajectory of states lie on a great circle (geodesic path) on the Bloch sphere at all times. We demonstrate that such extreme temporal correlation of TLS can be simulated in realistic system by embedding the TLS into a higher dimensional Hilbert space such that the composite system obeys unitary dynamics. Specifically we show that a four dimensional embedding of non-Hermitian PT- symmetric TLS is enough to host K
3 → 3 limit. We also discuss the effect of random noise on our results. Finally we conclude with a comparative study of our results with existing experimental realization of embedding.
A geometric approach to the generalized Noether theorem
Authors: Bravetti Alessandro , Garcia-Chung Angel
Published: January 2021

We provide a geometric extension of the generalized Noether theorem for scaling symmetries recently presented by Zhang P-M et al (2020 Eur. Phys. J. Plus
135 223). Our version of the generalized Noether theorem has several positive features: it is constructed in the most natural extension of the phase space, allowing for the symmetries to be vector fields on such manifold and for the associated invariants to be first integrals of motion; it has a direct geometrical proof, paralleling the proof of the standard phase space version of Noether’s theorem; it automatically yields an inverse Noether theorem; it applies also to a large class of dissipative systems; and finally, it allows for a much larger class of symmetries than just scaling transformations which form a Lie algebra, and are thus amenable to algebraic treatments.
Application of software testing methodology based on quality criteria and expert assessments to mobile applications
Authors: Galimova E Y
Published: January 2021

In this paper, we propose a technique for choosing between a manual, automated and semi- automated approaches to software testing. The great desire of each person to achieve maximum comfort in each of the spheres of life has also affected the international web. The user, wanting to always stay online, uses the phone as a communicator. This led to the emergence of mobile Internet. When staying away from home or during travel and business trips, you can connect using a tablet or mobile phone instead of a laptop. The efficiency and functionality of “mini” computers would not be brought to such a high level without specialized applications. Properly chosen testing methodology improves the quality of mobile applications.
Transverse profile forming for high energy electron beams using 3D-printed plastic samples
Authors: Bulavskaya A A , Cherepennikov Yu M , Grigorieva A A , Gavrikov B M , Loginova A A , Miloichikova I A , Toropkov N E , Stuchebrov S G
Published: January 2021

The work presents application of previously proposed approach for transverse profile forming of high energy electron beams with plastic samples made using 3D printing technology. The collimator made of PLA (polylactide) plastic is designed and produced in a frame of this work. The results of transverse profile forming for 6 MeV electron beam of clinical linear accelerator Elekta Synergy using designed collimator is presented. Obtained results comparison with data from XiO dosimetry planning system shows good agreement of calculated and experimentally formed by plastic collimator electron beam dose fields.
The influence of load distribution along a line on power and place of connection of a photovoltaic system
Authors: Bogdan A V , Bogdan V A , Garkavyi K A , Netrebko D S
Published: January 2021

Distributed generation in the electrical network causes a redistribution of power and leads to a reduction in technological losses and a decrease in voltage deviations for consumers. The installation of additional generators of electric energy based on the use of wind generators and photovoltaic systems has become widespread in the world energy industry, and has now received development in the Russian Federation. It is shown that the connection of an additional source based on photovoltaic systems can reduce losses in a supply line. According to results of the analysis of a possible location of the connection of an additional power supply on a line with a uniformly decreasing or increasing load, it is proved that the greatest reduction in the level of losses in a line is achieved when additional power supply is connected to it in the case of increase in the load from the beginning to the end. Analytical expressions for determination of economically expedient capacities and a place of connection of an additional source for linearly decreasing or increasing specific load of a supply line are presented. There was determined the optimal power of an additional power source in the form of a photovoltaic system and the optimal point of its connection on a line to reduce power losses during power transmission.
The analysis of power system steady-state aperiodic stability with electronic generation
Authors: Fishov A , Murashkina I , Marchenko A , Enkhsaikhan E , Ivkin E
Published: January 2021

One of the main directions of electric power industry development all over the world is the use of distributed small generation, both based on carbon fuel resources with synchronous communication between sources when they are connected to electric networks, and renewable energy sources working in the electric network through frequency-converting devices (electronic generation). The latter leads to the inevitable mass use of inverters in existing AC electric networks. The objectives of this investigation are to study the impact of electronic generation on the modes and stability of existing electric networks and power systems, the formation of requirements for the characteristics of electronic generation control, which minimize the coordination of relay protection and automation with electronic generation in the electric network, as well as increase the reliability of the general electrical mode. The article presents the results study of the steady-state aperiodic stability of the power system with electronic generation, the requirements for their steady-state characteristics and control in the power system.
The Location estimation of seismic wave propagation layer velocities
Authors: Rabinovich E V , Filipenko N Y , Shefel G S
Published: January 2021

On the basis of the original location-based technology developed by the authors for constructing seismic images of the deep structure of the earth’s interiora method is proposed for estimating the seismic wave propagation layer velocities. The technology ensures the unambiguity and stability of seismic imaging by successively solving direct kinematic problems for all reflecting boundaries. It consists in locating the reflection pulse’s sources from the boundaries of the deep section’s layers and restoring the kinematic parameters of the layers through them. To assess the next layer velocity, information is used on the parameters of the preceding boundaries and the direct kinematic problem’s solution with the additional equality’s condition of local velocities at the reflection’s points from the underlying boundary.
AREIOM: adaptive research multicopter platform
Authors: Harradi R , Battseren B , Heller A , Hardt W
Published: January 2021

The applications of unmanned aerial systems have dramatically increased in the late days, in particular within dull, dirty and dangerous missions, where it has been clearly shown that unmanned systems are better suited than manned aircrafts. The reduction of human involvements leads to an increasing demand for autonomous and operationally adaptive airborne systems. In addition, unmanned aerial systems share similar limitations with most computer embedded systems, e.g., limited space and power resources, and increasing computation requirements and complexity of the applications running onboard. To fulfill these requirements and achieve the fundamental features of autonomy and adaptability, the AREIOM—Adaptive Research Multicopter Platform—along with its layered modular architecture and the specific details of its underlying hardware and software components are presented.
Study of the laws of oxidation of biodiesel
Authors: Yudaev S A , Ivashkina E N , Sapunov V N , Voronov M C
Published: January 2021

The paper discusses in detail the first stage of the catalytic oxidation of fatty acid methyl esters with atmospheric oxygen. According to the data obtained as a result of processing the kinetic data, it was concluded that the reactivity of the components of biodiesel. It is established that polyunsaturated and monounsaturated compounds have different reactivity from each other. The kinetic pattern of consumption of unsaturated components of biodiesel was set up and kinetic constants were calculated, which are equal to: oxidation of C18/1 k1 = 0.106 ± 0.008 h−1, and oxidation of C18/2 k2 = 0.269 ± 0.005 h−1, respectively
High-resolution phonocardiogram parameters
Authors: Zemlyakov I Yu , Zdanov D S , Kosteley Y V , Golobokova E V , Dikman E Yu , Bureev A Sh
Published: January 2021

The article describes the results of studying and analyzing phonocardiograms (PCGs) obtained during a physiological experiment with Blu-ray standard equipment. It provides the findings of a spectral and spectral-time analysis for signals with a sampling frequency of 10, 44.1 and 192 kHz. It shows that the differences in the PCG spectra of identical signals are unreliable. The article specifies the onset and disappearance moments of the harmonic components of heart sounds. It also provides recommendations on the sampling frequency and bit resolution of digitized PCG signals for telemetric systems.
A system-inno-diversified approach to the development of technologies for the effective transformation of organizations of the agro-industrial complex into a digital economy
Authors: Chernyakov M K , Chernyakova M M
Published: January 2021

The paper examines the most important trends and concepts of the modern stage of digitalization and the end-to-end technologies offered by the “Digital Economy” program. The necessity of creating a technology of regulation by the agro-industrial complex as an important component of the modern digital economy is substantiated. The aim of the research is to develop technologies for the effective transformation of the organizations of the agro-industrial complex into a digital economy. According to the definition of the digital economy proposed in the work, it should be built as an in-diversified, self-developing system. The concept of technology for regulating the digital economy of the agro-industrial complex should be formed on the basis of a systematic approach and have a hierarchical 5-tier network structure. The possibility of implementing the structure using the mathematical apparatus of the theory of Petri nets is substantiated. It has been established that model design of technology is the most optimal, if not the only possible way to improve the structure of production systems and technological processes of organizations of the agro-industrial complex, as well as to manage its structures.
Application of neural networks in problems of determining geometrical properties of objects placed in geophysical elastic media
Authors: Morozov A E , Yakimenko A A , Karavaev D A
Published: January 2021

The use of a neural network approach is associated with high requirements for software implementation. The main criteria is a high degree of accuracy in the recovery of the desired geological-physical model of the environment (GPME) and processing speed. The paper presents a description of the developed neural network architecture for solving the inverse problem of geophysics for determining the geometric properties of GPME objects. The performance of a single neural network and an ensemble of neural networks (NN) has been evaluated. The results are presented comparing the operating time of the NN when restoring models on various computing devices: CPU and GPU. The results of experiments on the restoration of various GPME using the developed NN based on the LSTM layer and the U-Net architecture are presented. This work was supported by the RFBR grant No. 19-07-00170.
Application of standard ZET-algorithm for gaps filling in wide area measurement system data assets
Authors: Batseva N L , Foos J A
Published: January 2021

This article explores the application of Standard ZET-algorithm for gaps filling in Synchronized Phasor Measurement data assets received from Wide Area Measurement Systems. In spite of Synchronized Phasor Measurement data assets apparent advantages, they have gaps affecting the accuracy of solving power engineering tasks. Authors analysed the reasons of gap occurrence in data assets, provided experiments with voltage and current data assets and collected the key points about application of Standard ZET-algorithm.
Numerical 3D simulation of enhanced oil recovery methods for high-viscosity oil field
Authors: Persova M G , Soloveichik Y G , Ovchinnikova A S , Patrushev I I , Nasybullin A V , Orekhov E V
Published: January 2021

The paper is devoted to the numerical simulation of oil recovery process using the technologies of polymer flooding and surfactants. The simulation is performed on the basis of the finite element method as well as the special scheme of flow balancing and phase flows between the cells, which along with high accuracy of pressure approximation, ensures the conservation of mass of filtering mixture components. The possibilities of simulation of different mechanisms of interaction of injected compositions with a medium are presented. The results of numerical simulation of different reservoir stimulations are shown using the digital model of the high-viscosity oil field in Tatarstan. It is shown that the application of polymer flooding and surfactant-polymer solutions makes it possible to increase the oil fraction in the produced fluid and, consequently, enhance the oil recovery.
Prospects for the development of functional expansion of individual low-cost prosthetic limbs for people with disabilities with intelligent sensors
Authors: Gryaznov D , Zhmud V , Avrmachuk V , Malakhov D , Nosek J , Dimitrov L
Published: January 2021

Despite the development of medicine, as well as robotics aimed at helping people with disabilities, most disabled people with missing limbs cannot hope for a full life with the help of bionic prostheses, since these products are made strictly individually, and their control requires expensive surgeries to implant sensors. In addition, such prostheses themselves are very expensive. An alternative solution is to reduce the cost of such prostheses as much as possible and abandon the implantable sensors of signals of the human nervous system. The paper proposes a method for solving such a problem using a variety of sensors that remove signals from the skin surface without invasive surgery.
Critical technologies in the cluster of virtual and augmented reality
Authors: Zhmud V , Liapidevskiy A , Avrmachuk V , Sayapin V , Sedinkin J N , Hardt W
Published: January 2021

The program “Digital Economy of the Russian Federation”, launched in 2019, contains virtual and augmented reality technologies in its list. Each such technology consists of many assistive technologies called sub-technologies. These assistive technologies make up a large list, while failure to obtain the required results in at least one of these technologies may lead to the fact that the integral technology will not be created. This article discusses a list of only critical assistive technologies, that is, precisely those technologies whose creation is a critical factor for creating a generalized (integral) technology. It is on these technologies that the main emphasis should be placed not only in financing their development, but also in the thorough planning of goals and objectives, in the selection of performers and in the acceptance of research results.
InAlN/GaN and AlGaN/GaN HEMT technologies comparison for microwave applications
Authors: Velikovskiy L E , Sim P E , Demchenko O I , Kurbanova N E , Filippov I A , Sakharov A V , Lundin W V , Zavarin E E , Zakheim D A , Arteev D S , Yagovkina M A , Tsatsulnikov A F
Published: January 2021

High electron mobility transistors (HEMTs) technologies based on AlGaN/GaN and InAlN/GaN heterostructures have been developed. The research focused on influence of epitaxial growth conditions and buffer doping profiles on electrical properties HEMTs. An output power density of 4W/mm at 17 GHz was demonstrated for InAlN/GaN HEMTs and 7W/mm at 10 GHz for AlGaN/GaN HEMTs.
Implementation of vibration signals receiving unit on Raspberry single-board computers
Authors: Faerman V A , Tsavnin A V , Andreev S A
Published: January 2021

The paper dedicated to vibration measurement system development on the Raspberry Pi basis. Main features of the solution are low-cost, easy access to components and functionality and flexibility provided by Raspberry Pi usage. Circuit solution and configuring procedures are presented and described. In particular, block diagram of the vibration measurement system with piezo-electric sensors. Two variants of the vibration measurement system, on the Raspberry Pi B+ and Raspberry Pi 3B correspondingly, were implemented and tested as well. In addition, two variants of impedance-matching device were implemented. Conducted and described experiments confirm performance both separate components and the whole solution. Presented results are applicable for correlation leak detectors new algorithmic solutions and in educational process.
Compatibility of the dimensions of polymer molecular aggregates to the pore throat of a reservoir
Authors: Na Risu , Erofeev V I
Published: January 2021

The compatibility of the dimensions of the polymer molecular aggregates and the pore throat of the reservoir were studied. The W section of Tuha oilfield was the study area and polymers produced by Daqing Refining and Chemical Company were used. The permeability limit of the polymer molecules with different molecular masses and concentrations, matching relationship between the dimension of polymer molecular aggregates and pore throat were obtained by experiments. The results of the research are important for the development and implementation of a polymer flooding technical scheme in the middle and late stages of the operation of the Tuha oilfield.
Modelling and performance analysis of DWDM passive optical network
Authors: Sadinov S M , Angelov K K , Kogias P
Published: January 2021

Passive optical networks are emerging as the main technology for building access networks. The current metropolitan optical communication networks operate at 1Gbps, which appears to be insufficient for the future development and exponential growth of traffic from IP services. The existing various traffic-intensive services and the growing interest in 4K video content and streaming services require the introduction of new solutions within passive optical networks (PON). A promising option is the combination of 10 Gbps and above high-speed data transmission with spectral multiplexing. DWDM will provide the required high spectral efficiency, but in contrast will require the use of a proper modulation scheme to achieve a longer distance. In this paper a model for performance analysis and solving optimization problems for DWDM-PON networks is developed. Different signal modulations are considered and a comparative analysis is performed. The behaviour of the system at different input parameters is modelled. Performance analysis is performed by evaluating the spectral characteristics and values of BER and Q-factor.
Experimental study and analysis of hydraulic characteristics of diaphragm (chamber) gas flow meter
Authors: Tsankov P G , Georgeva NA , Delcheva S G
Published: January 2021

In the conditions of life, the most common household gas flow meters are diaphragm (chamber) flow meters. From a technical point of view, hydraulic and durability characteristics are important A basic requirement that must be met by measuring instruments used for industrial or domestic applications is to be as accurate as possible. The diaphragm flow meter type BK G2.5T was experimentally studied in the work. The hydraulic (resistance) characteristic Δp = f (Q) of this type of flow meters is obtained and it is derived the analytical dependence of this characteristic - square parabola and means pressure drop at a nominal flow rate – Δpm = 0,4 mbar. The established pulsation character of the operation of the diaphragm flow meter is analyzed by the introduced one the characteristic of the pressure pulsations δp = pmax - pmin = f (Q), as for the specific flow meter the pulsations are δp = 0,1…0,2 mbar. The original results from obtained researches will be useful for constructors for optimization of the design of the gas systems.
Fly ash zeolites as a dual system for simultaneous CO2 capture and its utilization in the production of synthetic gas
Authors: Zgureva D M , Boycheva S V , Filipov K B
Published: January 2021

The deepening of global environmental problems caused by carbon emissions (CO2) generated by various industries requires the development of technological solutions to limit their emitting into the atmosphere. Electrical power plants that use organic fuels as a primary energy source are serious emitter of CO2. The current legislation prerequisites the implementation of technologies for carbon capture and utilization (CCU - Carbon Capture and Utilization) situated at the plant site. In our previous studies, we successfully applied the zeolites synthesized from fly ash obtained from combustion of lignite coal as solid adsorbents for selective capture of CO2 in equilibrium and dynamic conditions. The aim of this study is upgrading of the fly ash zeolite utilization in a dual system for simultaneous carbon capture and CO2 utilization for production of synthetic gas. Experiments were performed in a stainless steel laboratory reactor Büchiglasuster Miniclave 100 in equilibrium conditions at CO2 pressure of 0.25 MPa with different duration. The solid samples saturated with CO2 and reaction products were extracted from the reactor and subjected to gravimetric analyses and Furier-transform infrared spectroscopy (FTIR). The characteristic vibrations of C2H2n+2 molecules were observed onto FTIR spectra of the samples after their exposure for long time.
Studies on the thermochemical energy storage in the coal ash zeolite/water system
Authors: Boycheva S V , Zgureva D M , Marinov I K , Miteva S , Yankov I , Ivanov A , Asenov A N
Published: January 2021

Deterioration of the air quality and the greenhouse effect requires replacement of the conventional fuels with renewable energy sources (RES). The main disadvantage of RES is the intermittent production of energy during the day and the different seasons. This requires efficient energy storage solutions. Affordable technologies applicable to household-scale heating are thermochemical energy storage systems (TES). TES are usually applied for concentration and storage of solar energy. TES based on zeolites as heat storage media use the exothermic effect of water adsorption. The preferred storage medium is commercial zeolite 13X, which is characterized by high porosity and a large specific surface area. In these systems, the charging is carried out at 130-180 °C and the energy storage efficiency is over 90 %. In the present study, storage media of zeolite X synthesized by the alkaline conversion of coal fly ash was studied in a laboratory assembled TES as a possible substitute of zeolite 13X. The results revealed a micro-mesoporous structure for coal fly ash zeolites (CFAZ) in contrast to the microporous 13X. The charge of TES with CFAZ can be carried out at lower temperatures, while its discharge is enough exothermic. The utilization of coal ash as raw materials for synthesis of heat storage media contribute to many environmental benefits.
Automatic detection of characteristic segments of a recorded ECG signal with noise handling methods
Authors: Glushica B , Aleksovski B , Kuhar A
Published: January 2021

Depolarization and repolarization of the myocard results in specific wave shapes that are recognizable in an ECG signal and are characterized by their length, rise time and amplitude. Changes in these characteristics usually indicate anomalies in the function of the heart. Automatic detection of characteristic segments of the ECG signal is of crucial importance for fast and reliable recognition of artefacts that are further analyzed as a means for setting a diagnosis. In this paper a contribution has been made towards efficient automatic segment detection of real ECG signals recorded in arbitrary conditions in the presence of noise from various sources. The method of accumulated differential and a technique for tracing the wave shapes of the ECG signal using their local extrema have been implemented in the developed algorithm. The implementation of these methods yields an advanced way of handling the noise present in the ECG signal resulting with high precision segment detection and low computational power requirement. The high accuracy of the algorithm has been verified using real signals recorded on 2 lead ambulatory electrocardiograph. Another benefit of the developed algorithm is its speed – it is able to process a 5 minute long recorded ECG signal in 9 seconds.
Lactobionic acid-chitosan functionalised gold-coated poly(lactide-co-glycolide) nanoparticles for hepatocyte targeted gene delivery
Authors: Akinyelu Jude , Oladimeji Olakunle , Singh Moganavelli
Published: January 2021

Nanoscale non-viral gene delivery vectors are attractive systems for the efficient and safe delivery of therapeutic genes. This study explored the potential of surface tailored poly(lactide-co-glycolide) (PLGA) systems for targeted gene delivery to human hepatocellular carcinoma (HepG2) cells overexpressing the asialoglycoprotein receptor (ASGPR). Chitosan (CS) functionalised gold (G) PLGA nanoparticles (NPs) were synthesised with and without the targeting ligand, lactobionic acid (LA), and bound to pCMV-Luc-DNA (pDNA) to form nanocomplexes. NPs were physicochemically characterised, and pDNA binding and protection by the NPs were investigated using mobility shift, dye displacement and nuclease digestion assays. MTT and luciferase assays served to evaluate cytotoxicity and transgene expressionin vitro. Nanocomplexes of 20–40 nm in size effectively protected the DNA from nuclease digestion and exhibited low cytotoxicity (>90% cell viability). Targeted transgene expression was significantly greater than the untargeted expression, confirming ASPGR uptake. Our results highlight the potential of these hybrid CS-PLGA based nano-platforms for targeted gene therapy, warranting further development, especially for liver-directed gene therapy.
SuperPlotsOfData—a web app for the transparent display and quantitative comparison of continuous data from different conditions
Authors: Goedhart Joachim
Published: January 2021

SuperPlotsOfData is a web tool for the transparent display and quantitative comparison of continuous data from different conditions. It offers easy and open access to state-of-the-art data visualization. In addition, it incorporates recent innovations in data visualization and analysis, including raincloud plots and estimation statistics.
Molecular mechanisms underlying cellular effects of human MEK1 mutations
Authors: Marmion Robert A. , Yang Liu , Goyal Yogesh , Jindal Granton A. , Wetzel Joshua L. , Singh Mona , Schüpbach Trudi , Shvartsman Stanislav Y.
Published: January 2021

Genetics and quantitative imaging studies in Drosophila provide insights into molecular and network-level effects caused by pathogenic mutations affecting a core cell signaling kinase.
Urgent care for older people
Authors: Conroy Simon , Thomas Matt
Published: January 2021

Geriatric medicine is the clinical specialty that focuses upon the care of older people—especially those with frailty (a state of increased vulnerability). In hospital, older people living with frailty are at high risk of developing a range of unpleasant outcomes such as delirium, falls, fractures, pressure sores and death. Comprehensive geriatric assessment is a form of holistic care that incorporates a specific set of clinical competencies that are able to reduce these adverse outcomes. Over the years, geriatric medicine has moved from being more of a community-based service towards a more acute specialty—encroaching now upon emergency department care. The challenge now is to work out how best to deliver geriatric care across the whole hospital (older people with frailty are not just cared for in geriatric wards!). The themed collection published on the Age & Ageing journal website outlines key articles that are attempting to develop solutions to this challenging conundrum. We hope that you enjoy reading them.
Verifying Clinically Derived Reference Intervals for Daily Excretion Rates of Fractionated Metanephrines Using Modern Indirect Reference Interval Models
Authors: Doyle Kelly , Frank Elizabeth L
Published: January 2021

Objectives

Biochemical testing of urinary metanephrines is useful in the diagnosis and monitoring of pheochromocytoma and paragangliomas. We investigated the feasibility of mixture decomposition (ie, indirect) methods in verifying clinically derived reference intervals for urinary deconjugated metanephrine metabolites.

Methods

Urinary 24-hour metanephrine and normetanephrine excretion results were extracted from our data warehouse and intervals were estimated by the modern variant of the Hoffmann method, maximum likelihood estimation (MLE), and gamma mixture model using R software.

Results

Hoffmann, MLE, and gamma mixture models provided metanephrine and normetanephrine intervals that closely matched those derived from clinical studies. However, three-component MLE and gamma models were required for normetanephrine in adult women because the Hoffmann method was not suitable. Some data transformations caused blending of the mixed distributions and subsequent widening of the reference interval estimation, emphasizing the importance of careful data transformation for Hoffmann and MLE analyses. Gamma mixture models gave overall good agreement without the need for data transformation.

Conclusions

Indirect methods have utility in verifying reference intervals in 24-hour urine specimens collected by patients. We emphasize the benefits of applying multiple decomposition methods to corroborate findings and careful application of data transformation when using Gaussian-based models.
A proposed antioxidation mechanism of ergothioneine based on the chemically derived oxidation product hercynine and further decomposition products
Authors: Ando Chika , Morimitsu Yasujiro
Published: January 2021

Ergothioneine (ERGO), a thiohistidine betaine, exists in various fungi, plants, and animals. Humans take in ERGO from their diet. ERGO is a strong biological antioxidant, but there are only a limited number of reports about its redox mechanism. The purpose of this study was to clarify the oxidation mechanism of ERGO. Reactions of ERGO with chemical oxidants were performed. The oxidation products of ERGO were analyzed by nuclear magnetic resonance and liquid chromatography-mass spectrometry (LC-MS). The major product of oxidation of ERGO by hydrogen peroxide in physiological conditions was identified as hercynine (histidine betaine). One molecule of ERGO was able to reduce 2 molecules of hydrogen peroxide. Hercynine was found to react with the more potent oxidant hypochlorite. One unstable decomposition product was detected by LC-MS. As a result, a mechanism of oxidation of ERGO, and hence its physiological antioxidant activity, was developed.