bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the properties changes observed for plastic samples made by fused deposition modelling under radiation exposure
Authors: Bulavskaya A A , Cherepennikov Yu M , Grigorieva A A , Miloichikova I A , Toropkov N E , Stuchebrov S G
Published: January 2021

This work shows investigation of the transmission dynamics of polymer samples made of PLA plastic (polylactide) by fused deposition modelling for electron beam. Besides, results of tests for mechanical destruction (compression) of plastic samples with radiation exposure and without are shown. Article demonstrates that properties of plastic samples are stable up to 1.5 kGy, that proves the suitability of this material for sample production intended for depth dose distributions of electron beams.
Aircraft landing gear with electromagnetic damper
Authors: Zagidulin A R , Podruzhin E G
Published: January 2021

The article describes the design and computation of the aircraft landing gear with an electromagnetic-gas shock absorber. A numerical simulation of the landing impact was carried out at different values of the initial vertical velocity. The dependence of the optimal electric current in the winding of the shock absorber electromagnet on the vertical speed is obtained.
The influence of the method of an arc discharge initiation on the product of plasma dynamic synthesis in the W-C system
Authors: Sivkov A A , Nikitin D S , Shanenkov I I , Nassyrbayev A , Rakhmatullin I A
Published: January 2021

Cubic tungsten carbide WC1−x is distinguished by the difficulty of obtaining in a dispersed and bulk form. The article attempts to plasma dynamic synthesis of cubic tungsten carbide in powder form. The method is based on the use of a coaxial magnetoplasma accelerator for the generating a supersonic plasma jet, which is then rapidly cooled. The possibility of obtaining a powder with a predominant content of WC1−x (up to 95%) is shown. Studying the influence of the method of an arc discharge initiation allowed to reveal the efficiency of using graphitization in comparison with carbon fibers.
A computational fluid dynamic approach to validate the wind effect in air pollution of Ulaanbaatar city
Authors: Bulgansaikhan B , Ulziibayar V , Munkherdene Ts
Published: January 2021

In the past two decades, inhabitants of Ulaanbaatar city have been increased more than three times. The Air and soil of Ulaanbaatar city contaminated seriously due to the densely populated behavior. We proposed to develop a massive computational model for pollution, which cares about contamination factors. This paper is a part of the purpose. We consider the filtered equation express conservation of mass and momentum in a Newtonian incompressible flow in a computational fluid dynamic model for Ulaanbaatar’s wind field. The terrain around the city has been built for numerical computation. The finite element method was used for numerical analysis, from the results, we can characterize the wind field.
Novel DC arc plasma method for super dispersed metal carbides synthesis
Authors: Pak A Ya , Mamontov G Ya , Vassilyeva Yu Z
Published: January 2021

This paper presents the experimental results of metal carbides synthesis by DC arc discharge plasma in ambient air. The results indicate that the synthesis takes place in the atmosphere of CO and CO2, which are generated during the DC arcing process on graphite electrodes and that mixture of CO and CO2 prevents the reaction zone from air oxygen. The paper introduces experimentally substantiated arguments about the possibility of obtaining metal carbides by the developed arc discharge method. By the moment, the authors have already obtained silicon carbide and titanium carbide in this way.
The approach to construction and discretization of complex 3D models of geological media in software for airborne geophysical surveys maintenance
Authors: Soloveichik Y G , Persova M G , Kiselev D S , Trubacheva O S , Kondratyeva N S , Grif A
Published: January 2021

The paper presents a new approach to construction of complex geological models and generation of finite element meshes in order to perform 3D modeling and multidimensional processing of airborne geophysical data. The main principles of geological models construction are considered. They are based on defining geological models in terms of the subject field and take into account their main specifics: complex background media, curvilinear Earth surface relief and borders between the geological layers, complex shape of target objects, etc. We consider the necessary data structures and specifics of finite element mesh generation. The example of generation of the finite element mesh for a geological model typical of airborne geophysical surveys is shown.
Prospects for the use of wireless reading of prosthetic control signals and methods for generating commands
Authors: Malakhov D , Zhmud V , Avrmachuk V , Gryaznov D , Nosek J , Dimitrov L
Published: January 2021

The paper provides a rationale for the use of low-power wireless communication to create non-invasive bionic limb prostheses. The need for such a connection is dictated, on the one hand, by the expediency of using sensors located in various parts of the body, often very remote from each other, on the other hand, by the desire to free the disabled person’s body from the wires that would envelop it like a spider web. For each of these positions, arguments are given.
Generalization of data on heat exchange within a gas mixture with a small value of Prandtl numbers in channels of different forms
Authors: Elistratov S L , Slesareva E Yu
Published: January 2021

The article presents an analysis of data on heat transfer in the channels of a round and triangular shape with a flow of a gas mixture with a small Prandtl number. It is shown that for the Reynolds number in the interval from 9500 to 49000 the heat-transfer coefficient depends from the length a heat exchange section in tube. Using the dependence of the Nusselt number Nu(Ψ) from a dimensionless parameter Ψ=1/Pe×x/D

h
, we can describe the experimental data for the input region of the round and triangular channels, taking into account the channel length and the distances from the input. The adequacy of the model was checked by comparing the proposed dependence with the experimental data of various authors.
Study on interfacial tension of surfactant and its oil displacement performance
Authors: Na Risu , Erofeev V I
Published: January 2021

Tuha oil field is located at the Turpan basin in China. Currently, the water content of the main reservoir of the section Y-6 of the Tuha oil field is more than 93% and the recovery rate is less than 20%. At present, an efficient oil displacing agent must be selected for this oil field, which can be used in reservoirs with a high degree of mineralization. Based on the results of experiments measuring the interfacial tension of the surfactant solution and oil, a non-ionic surfactant was selected. Non-ionic surfactant can reduce interfacial tension to the ultra-low level (10−3 mN/m), and when the amount of adsorption by oil sand is 3, interfacial tension also can maintain at the level of 10−2 mN/m, so the solution of non-ionic surfactant has good anti-adsorption ability. The results of the oil displacement experiments show that the solution of a non-ionic surfactant can increase the efficiency of oil displacement. But under condition of high water cut, the dominant flow channel in the core is formed, and the surfactant solution flows into the main channel preferentially and reduces the residual oil saturation in the main channel, which leads to a decrease in the resistance coefficient and injection pressure. Therefore, after water flooding, take measures to control the fluid profiles firstly so that the following surfactant solutions change direction in areas not exposed to water in order to achieve the best effect of the increase in oil recovery.
Wettability inversion of aluminum-magnesium alloy surfaces
Authors: Islamova A , Orlova E
Published: January 2021

The paper presents the experimental results on the use of low-temperature heating to reduce time of wetting inversion (from superhydrophilicity to hydrophobicity) of aluminum-magnesium alloy surfaces textured by laser radiation. Stable growth of the contact angle to 137.3–144.2° after heating surfaces (wettability properties deteriorate) was recorded. Wetting inversion from superhydrophilicity to hydrophobicity occurs in 2–3 hours of low-temperature heating of textured samples. The wettability inversion time depends on the type of texture. A significant increase in carbon content of elemental composition of the near-surface layer of samples after their low-temperature heating was registered.
Automation of the monitoring system for surface contamination with α-active radionuclides
Authors: Khan V A , Myshkin V F , Khorokhorin D M , Izhoykin D A , Kuznetsov M S , Panamaryova A N , Rakhimzhanova L A
Published: January 2021

The paper presents research on radiation control at nuclear enterprises working with α-active radionuclides. The focus of the research is on the registration of 239Pu radionuclides on hands surface. The experimental results show the possibility to create a turnstile for automatic monitoring the presence of α-active radionuclides on hands. Such a device can be used with a minimum helium consumption of 66 liters per hour in a measuring chamber with an open bottom of 5.4 liters.
Study of enzymatic hydrolysis parameters for reducing anti-nutritional properties of flour
Authors: Ashirova N , Bychkova E , Gurova D
Published: January 2021

The paper addresses the problem of production of foodstuffs for people suffering from diagnosed celiacia. There are no ways of pharmacological treatment of this group of people. The only possibility to maintain their optimal living standards is a life-long gluten-free diet. Grain-based proteins (wheat gliadins, rye secalines, barley hordeins, and oat avenines) and products of their processing are the disease triggers. Most often one generally accepted term “wheat gluten” is used instead of all these species. Celiacia is one of the urgent social problems in many countries which can be explained by its wide morbidity rate, difficulties in its diagnostics and a lack of experience of its prophylaxes and treatment. Strict requirements to the chemical composition of gluten-free flour-based foodstuffs dictate their high retail prices. Market analysis has shown that gluten-free flour-based products on average are 240% more expensive than usual flour-based products. So crackers, butter biscuits, pizzas and pasta made from gluten-free flour are the most expensive products. However the market of gluten-free flour-based products is one of the most fast growing markets. In this connection there is a need to provide people suffering from diagnosed celiacia with inexpensive domestic gluten-free products of high quality including products suited for public catering facilities such as pre-school, school and higher education institutions, military army facilities, canteens and sanatorium-and-spa resorts. Developing specialized foodstuffs based on nontoxic raw materials having a positive effect on human organisms and able to decrease risks of disease recurrence is a challenge to the scientific community.
Application of the probabilistic technologies to power plant design
Authors: Krivova L V , Shmoilov A V
Published: January 2021

In the report the developed approach for choice and substantiation of power equipment, current-carrying parts and switching devices using existing and proposed probabilistic method of borders selection of input and output data (SBID) is presented. SBID method allows to receive complete probabilistic characteristics or probability distribution laws (PDL) of output data as functional dependence from the arguments (input data) by probabilistic characteristics of arguments. Any task, including electrical values in operating modes and transient conditions in power system can be exposed as dependence on input or output data. Due to SBID method, the PDL of input data processing results of these dependencies may be received. PDL allows to calculate risks of overload of the power components in the operating modes and destruction, also power equipment parameters, current-carrying parts and switching devices are going to be selected on the basis of the minimum specified risks.
Research of the operation voltage limiter in pulsed mode
Authors: Krasniy I , Akimov S
Published: January 2021

This paper presents the results of investigations on the matter of withstanding power and switch-on time of the voltage limiter operating in a pulsed mode. The voltage limiter is based on a silicon p
+−n−n
+ structure obtained using the «batch» method of simultaneous two-way diffusion of boron and phosphorus out of solid phase.
Studying the influence of supply pulse duration on the phase composition of iron oxides obtained by the plasma-dynamic method
Authors: Shanenkov I I , Sivkov A A , Ivashutenko A S , Gukov M I , Shanenkova Y L
Published: January 2021

Magnetic materials and in particular iron oxides are of a great practical interest. The magnetite phase and the unique epsilon phase of iron oxide can be especially pointed out. The main difficulty in the synthesis of the epsilon phase is connected with the fact that it can exist only in a nanoscale state and is extremely difficult to obtain. We used the method of direct plasma dynamic synthesis, which allows obtaining multiphase powders of iron oxides containing both the epsilon phase and magnetite. It was found that by varying the initial parameters of the power system, namely the pulse duration by increasing the capacitance of the capacitive energy storage, it is possible to influence the phase composition of the obtained products and to achieve the preferential output of the epsilon phase. In addition, in the mode with the maximum pulse duration, when the best product is obtained from the point of the epsilon phase output, the system efficiency of converting the stored energy into released energy significantly increases. In general, it has been established that such a regime is most favorable for the system operation for the purpose of the iron oxides synthesis.
The high-level overview of social media content search engine
Authors: Savelev A O , Karpova A Yu , Chaykovskiy D V , Vilnin A D , Kaida A Yu , Kuznetsov S A , Igumnov L O , Maksimova N G
Published: January 2021

An increasing amount of social networks users-generated data is the most remarkable research challenge nowadays. Despite the progress in the field of semistructured data processing algorithms creation, even initial data collection could not be treated as issues that have been optimally solved. The paper covers a high-level overview of the automated social media content search system. The proposed structure enables to implement instruments for multisource content extraction tasks as well as supporting of identification processes of new patterns, which describe a certain type of content. Issues of Search engine organization, logically unified extracted data repository and possible content classification techniques with the appropriate knowledge base’s application are considered. Under the work, existing approaches and automated web-data extraction methods have been analyzed; social media API’s functions and limits, as well as ways of semistructured data storage system organization, have been studied. The planned result’s application area is automation and informational support of sociological research based on the social media content analysis techniques namely a content propagation simulation in interconnected groups; social and personal anomy study; clarification of the weak linkage’s strength concept.
An investigation of novel active phased array components
Authors: Alekseytsev S A , Gorbachev A P , Parshin Y N
Published: January 2021

This paper deals with a novel approach for designing dual-band dipole radiators. The brief explanation of the basic antenna characteristics obtained is given in the paper. The approach proposed is based on the exact analytical solution for the overall input impedance of a system which consists of two ends-fed dipoles. Then, based on this solution the comparison of the analytical and the simulated results is derived and shown in the paper. In the printed model of the system proposed we compensate huge capacitance occurring in the input impedance of a stand-alone ends-fed dipole by decreasing the gap between the dipoles and the ground plane. Besides, the mathematical model of the phase shifter for phased antenna arrays designing, which is designed for improving the linearity of the phase shifting performance is presented below. Thirdly, the crossed dipole-like antenna fed by rectangular waveguide is also proposed in the paper.
System for automated environmental monitoring using remote sensing data of the Earth from open data sources
Authors: Maslov K A , Tokareva O S
Published: January 2021

Environmental monitoring using remote sensing data requires an analyst to perform a large amount of routine work related to downloading, processing and analyzing data, especially in cases when the study area is covered with a large number of satellite imagery. The paper presents the results of the design and software implementation of the system that automates downloading and processing of remotely sensed data according to developed scenarios and, thus, greatly simplifies the processing of satellite imagery. It provides the description of tools for accessing data from the archive of the United States Geological Survey (USGS) and describes the data flow in the system. The paper gives an analysis of results obtained using the developed system on the example of monitoring the state of Siberian pine forests of the Tomsk region.
Adaptive frequency islanding system for distributed generation energy districts
Authors: Abeuov R B , Aryutina E A , Vassilyeva Yu Z
Published: January 2021

This paper presents the developed Adaptive frequency islanding system for distributed generation energy districts. The research is initiated due to the changes of power system structure, increasing the share of distributed generation. At the same time the existing islanding systems have a number of disadvantages, which leads to generation-shedding of distributed generation objects while allocating them for isolated operation. This is primarily due to the low speed of existing islanding systems. The solution to this problem can be an Adaptive frequency islanding system, which is high-speed and evens out the power balance in the distributed generation energy districts at the time of its allocation to isolated operation. The operating principle of this system is to determine the amount of control actions and their issuance at the substation of distributed generation energy districts based on the assessment of the electric power system mode and energy district real-time parameters.
Resilient satellite navigation empowers modern science, economy, and society
Authors: Filjar R , Damas M C , Iliev T B
Published: January 2021

Established on the exact mathematical principles, understanding of radio-wave propagation, and statistical signal processing and information theory, satellite navigation has become an essential cornerstone of modern civilisation, and an indispensable component of the national infrastructure. The increasing number of both navigation and non-navigation applications of the Global Navigations Satellite System (GNSS) utilise its Positioning, Navigation, and Timing (PNT) service for technology and business development, daily operation of technology and socio-economic systems, and improvement of the quality of life. The inherent shortcomings and limitations of GNSS ask for a transition towards the GNSS resilient to natural and artificial detrimental effects, which degrade the GNSS positioning performance. Here a systematic overview of the causes of the GNSS positioning performance degradation is outlined. Recent developments in mathematics and computer science are discussed as fundamental in the GNSS resilience development. Formulation of the Satellite-Positioning-as-a-Service (SPaaS) is outlined, as the new fundamental paradigm for resilient GNSS. Finally, the effects of the SpaaS on the wide range of GNSS applications in science, economy, and society are discussed. The contributions to SPaaS concept and the related developments through the application of statistical learning, mathematical methods and models development, and applications discussed result from the author’s involvement in numerous international strategic, technology, regulatory, standardisation, business, and academic education development and collaboration activities.
Performance of free-space optical systems in the presence of receiver imperfections
Authors: Djordjevic G T , Milic D N , Radojkovic I D
Published: January 2021

We present a review of papers considering the subcarrier intensity modulation free-space optical (FSO) communication systems in the presence of phase noise. This phase noise is a consequence of imperfect reference signal extraction in electrical domain after photodetector. We illustrate the effects of this phenomenon on the system symbol-error rate performance. The examples show that receiver imperfections, presented through phase noise, can degrade the FSO system performance to a large extent.
Deployment of mesh network in an indoor scenario for application in IoT communications
Authors: Angelov K K , Sadinov S M , Kogias P
Published: January 2021

The need for digital transformation in the industry and the related development of the Internet of Things (IoT) has led to the rapid development of various communication technologies and approaches for the implementation of flexible and intelligent communication networks. The main direction is wireless technologies, which make it possible to accelerate the wide range of new applications and services related to smart cities, industry, e-government and others. The possibilities are wide - use of different licensed or unlicensed frequency bands, channel bandwidths, modulation formats, power efficiency, reliability and security. Different network topologies could be applied for the access and collection of data from the sensor networks - star topology, mesh topology, tree topology, each of which has different advantages and disadvantages. This paper discusses the possibilities for deploying low-power mesh networks in an indoor scenario based on IQRF technology. Important communication parameters, approach advantages, and technological limitations will be highlighted. As an example, a study of network behaviour and efficiency in an indoor scenario will be considered.
Security of the sensory data in the cloud
Authors: Tsvetanov F A , Pandurski M N
Published: January 2021

The integration between the clouds and the sensor networks makes it possible to solve the problem of the limited computing power and the limited capacity of the sensor networks, as well as for the storage and processing of the collected data, without unnecessarily increasing the cost of the sensor networks. A significant challenge is the security of the data transmission connection between the sensors and the cloud. An algorithm has been proposed that ensures security in the transmission of data from the sensor network to the cloud via the DLS security protocol. The algorithm is implemented through the ThingSpeak cloud, and the connection between the sensor network and the cloud is implemented through the MQTT protocol, creating the flow that will gather sensor data, using Node-RED and Generate a self-signed certificate with OpenSSL. The algorithm was tested with Wireshark software, which confirmed that the data packets sent from the sensor network to ThingSpeak use the MQTT data transfer protocol and connect to communication port 8883, which is protected/encrypted via TLS / SSL protocol.
Voice control and management in smart home system by artificial intelligence
Authors: Balabanova I S , Kostadinova S S , Markova V I , Sadinov S M , Georgiev G I
Published: January 2021

The paper provides a 3D architectural model of Smart Home system. An information data sets of parameters in sound analysis of test voice commands were collected. The following analyzed indicators are included, respectively LZE, LZeq, LZF, LZS, LZI, LAE, LAeq, LAF, LAS, LAI, LCE, LCeq, LCF, LCS, LCI and LEX8h. Backpropagation and Hybrid algorithms based Artificial intelligence (AI) and Adaptive neuro-fuzzy interface system (ANFIS) were synthesized. Selected architectures are integrated in intelligent automated voice control system for human access control, power switching and lighting, air conditioning systems and home appliances. In the process of synthesis, different criteria for network performance in the analysis of activation type in the output layers in AI and input layer in ANFIS are applied. About all considered voice categories for functional control an accuracy of 100.0% was established. Verification procedures concerning reliability of the achieved results were performed for correct confirmation.
Storing data from sensors networks
Authors: Tsvetanov F A
Published: January 2021

Sensor networks generate a massive amount of heterogeneous and multidimensional data with specific characteristics, for the storage, processing and visualisation of generated sensor data most often used specially designed databases for sensory data, which can integrate into cloud structures. This paper presents a diagram of the integration of data from sensor networks in the cloud, which solves essential issues about the cost of sensor networks and the possibilities for storing sensor data in specialised cloud databases. The peculiarities of the sensory data and the specific requirements for their storage and processing are analysed. Through which approaches and models in the storage are identified, as well as the possibilities for their application. TSBD time-series database and cloud databases suitable for storage of sensor data are systematised, and recommendations for the selection made.
Study the influence of intermodulation products on navigation signals
Authors: Iliev T B , Stoyanov I S , Mihaylov G Y , Ivanova E P
Published: January 2021

The work examines terrestrial radio broadcasting using frequency modulation (FM), which interferes with the ILS (Instrument Landing System), VOR (VHF Omnial Radio range) and VHF communications systems, which is a widespread problem among aircraft users. In the case of ground/air communication receivers, this interference problem involves disturbing of audio communications and distorted reception of signals from the RV range. In aircraft ILS locators and VOR receivers, the interference problem is associated with interference of audio communications and errors related to course deviation and flag modes of control. Interference in these navigation receivers is considered as a more serious problem than errors in course deviation or impaired communication, especially in the approach and landing phases.
An industrial IoT edge node for buffer level detection in a cardboard production line
Authors: Avramidis G , Karampatzakis D
Published: January 2021

Computer Science and Internet have evolved rapidly the last decades and equally impressive is the evolution of the Industrial Internet of Things technology into factories’ shop floors. Among other technologies: modern CPU Architectures, Edge Computing, Deep Learning, Computer Vision, and Low Power Wide Area Networks, are playing a key role in this new competitive environment. In this paper, we present an Industrial IoT Edge Node for level detection on an overhead bridge conveyor (buffer) which is part of a 5-ply corrugated cardboard production line. We focused on the Edge Node and the development of the system was accomplished by using state of the art technologies from disciplines of computer vision and deep learning. We present two implementations using contour detection and CNN techniques. Finally, we implemented a LoRaWAN solution in the IIoT node to send alert messages to the control room. Experimental results are presented for the proposed system implementations.
On numerical method for modeling oil filtration problems in piecewise-inhomogeneous porous medium
Authors: Nematov A , Nazirova E Sh , Sadikov R T
Published: January 2021

Oil and gas fields in natural conditions are rarely of homogeneous nature. Given the chaotic nature of changes in rock mass permeability within a single layer, its significant parts (areas) can be considered uniform in permeability. If significant in sizes homogeneous zones (regions) are distinguished within the formation, the parameters of such a macro-inhomogeneous formation significantly affect the characteristics of the filtration flows. The area of zonal inhomogeneity consists of the parts of different permeability. Within the same zone, the permeability is on average the same, but differs from the permeability of adjacent zones.
Comparative analysis of prototypes for two-touch finger interfaces of smartwatch
Authors: Dimitrov Y N , Aleksieva V P , Valchanov H G
Published: January 2021

Two factors are important when the Smartwatch interfaces are developing - the small size of the display and the limited area for input control. The proposed by the authors prototype take them into account and aim to solve the “fat finger” problem and the difficult observation that affects the usability of the touch screen. It propose two fingers touch interface for smartwatch. The paper presents a comparison study of it for with two other prototypes. The results of complex evaluation of prototypes are given.
Technique for storing and automated processing of weather station data in cloud platforms
Authors: Sokolov S , Vlaev S , Chalashkanov M
Published: January 2021

In this paper we present an approach for design of cloud-based systems for storing and processing of sensor data from weather stations. In recent years there are abundant IoT devices that are capable of fairly precise data acquisition of local atmospheric parameters and reliable transmission over wireless network. The used dataset is acquired from a modern weather station model from a superior European manufacturer. 17 parameters are used for training neural network based LSTM model. In our research we have also compared several models and approaches for modeling this type of data. We propose a design of container based system for automated processing of the received data, visualization and cloud storage technique. We are comparing two types of open-source container technologies for implementing data processing. We have evaluated the performance and provide the set of criteria for choosing a container platform. Storing the data in the cloud is an important part and we provide our consideration for implementing a particular open source platform that could reduce costs fulfil the requirements for weather data storage. The designed system is expected to be cloud-provider agnostic. The proposed features make the system especially suitable for purposes such as local weather forecast; disaster prediction: hurricane, severe storms, floods, tornadoes, etc.; severe droughts with fire dangers; prediction of landslides. Depending on the availability of additional sensors the future development of the system may be extended with parameters of the soil. Training the model on a freely available data set is in our future plans for system development.
Analysis of the energy recovery possibilities of energy from lavender straws after a steam distillation process
Authors: Chakyrova D , Doseva N
Published: January 2021

In recent years, the area sown with lavender has increased in Bulgaria, which is then processed to essential oils by steam distillation. Plant residues after the steam distillation process are a major environmental problem and, at the same time, a valuable source of biofuels. Thus, the processing of lavender waste solves the problem of environmental pollution and generates energy that can be used for various purposes. This paper analyzes the possibilities for obtaining energy from lavender biomass. The processes of direct combustion and pyrolysis with their advantages and disadvantages are analysed and the yields of the obtained products are predicted by analytical calculations. For the purposes of this study, an experiment was conducted to determine the pyrolysis products of lavender straws and their quantitative ratios, which were compared with analytical calculations. The results show that the energy obtained can ensure the implementation of the steam distillation process and the residual energy can be used for other purposes.
Bin weather data of Varna and their influence on the seasonal efficiency of heat pumps with energy source outdoor air
Authors: Chakyrova D , Doseva N , Kalcheva N
Published: January 2021

The seasonal transformation coefficient (SCOP) of a heat pump with a heat source outside air as a function of the temperature of the latter is studied. The bin method was used to determine the climatic data for the city of Varna. Outdoor air temperature data were used and statistical analysis of the data was performed. The average frequency and cumulative distribution of temperature bins values in the period from 2005 to 2019 in the city of Varna is calculated. The results are presented using graphs and tables. In the data stability assessment report, the standard deviation and coefficient of variation were used. The SCOP of a heat pump heating installation operating in Varna has been calculated. All results were compared with those of other studies of the authors under different conditions and with reference data.
Achievement of maximum energy efficiency through vector control of induction motor electric drive
Authors: Rachev S , Ivanova G
Published: January 2021

Electric motors are the predominant driving devices globally, consuming electricity. For this reason, research aimed at minimizing their energy consumption is very relevant. The paper concerns an applied energy-saving method - vector control of an induction motor. With regard to this, a necessary condition for achieving maximum efficiency is to choose the optimal value of the magnetizing current. If the magnetizing current is not controlled properly, the result may be higher electricity consumption from a frequency-controlled motor than that of a direct-on-line power supply. In this case, a specific electric drive with certain parameters is analyzed. The research is based on a mathematical model, representing a system of differential equations, which is transformed and solved by appropriate software. The aim is to look for a minimum of electrical power losses. The physical side of the topic is treated exclusively without analyzing the economic benefits of the introduction of energy saving measures.
Influence of buoyancy forces in multi-storey buildings on the efficiency of a regenerative air handling unit with heat recovery
Authors: Penev A , Tsokov L
Published: January 2021

Various solutions are currently being offered to modernize the ventilation in old residential buildings. In small apartments, it is very appropriate to use decentralized ventilation units - for example with regenerative heat exchangers. Theoretical and experimental studies of such devices show a significant impact of the operational mode of regenerators (determined by the environment) on their efficiency. The aim of this article is to demonstrate the impact of the buoyancy forces in multi-storey buildings on the efficiency of a regenerative air handling unit for decentralized residential ventilation with heat recovery. Numerical solutions are presented for close to the real operating modes, airflow rates and air temperatures of the supply and the exit air, and the temperature ratio.
Hydraulic power take off system for wave energy utilization
Authors: Velichkova R , Pushkarov M , Angelova R A , Simova I , Markov D , Denev I , Stankov P
Published: January 2021

Wave energy from seas and oceans is among the most promising and abundant energy sources on the Earth. There are different designs of conversion systems for the utilization of the wave energy, resulting from the different ways of the wave energy absorption, and depending on the location characteristics. The paper proposes a new hydraulic power take-off system (PTOS) that can be used in various types of wave energy conversion systems.
Experimental investigation of the refrigeration cycle of water-to-water heat pump
Authors: Kolev Z D , Mushakov P G , Kadirova S Y
Published: January 2021

The refrigeration cycle of a reversible water-to-water heat pump has been investigated at different operation parameters of a laboratory installation. The investigation has been accomplished in cooling working conditions. The real operation cycles of the pump have been plotted in “logp-h” diagram by determination of definite thermodynamic parameters of the refrigerant. For this purpose, COOL PACK software has been used. The investigated refrigeration cycles are characterized by different switch off temperature of the heat pump. Based on the obtained results, the following parameters characterizing the heat pump’s efficiency have been determined: specific heat of vaporization, specific compression work, specific heat of condensation, and coefficient of performance.
Methodology for assessing the residual resource during the operation of high-temperature units
Authors: Nikiforov A , Prikhodko E , Kinzhibekova A , Karmanov A
Published: January 2021

The article analyses the main methods for determining the residual resource of these aggregates. Considering the imperfection of the above methods for estimating the residual resource, a method was developed for determining the residual resource of the linings of high-temperature units. The main parameters, which influence the residual resource of the lining, were determined during the operation of the units. In order to take into consideration the influence of temperature stresses on the residual resource of the sintering furnace, we examined a schedule for heating the furnace after an overhaul and calculated the temperature stresses that occur during heating and compared them with the acceptable values. Considering the temperature of the working medium, which exceeded the calculated one – was made according to the records of the operation logs. In general, the obtained result reflects a picture of the actual operation of the sintering furnace between its repairs. For its implementation into real operation, it is necessary to combine a number of measuring processes into a single information complex: a continuous measurement of the lining temperatures during heating; a burner performance (from the position of the torch profile and fuel oil spills); the quality of the resulting technological cakes, etc.
Modeling the influence of the characteristics of renewable organic materials on the energy performance of the boiler
Authors: Nikiforov A , Prikhodko E , Kinzhibekova A , Nurkina Sh
Published: January 2021

The object of the modeling is the process of burning organic waste, depending on the nature of the origin of the fuel, its chemical and fractional composition, density and lower calorific value. Processing the results of experimental study using analysis of variance will allow to estimate the variance caused by each factor individually and determine the level of influence of the factors on the output parameters of the process. It is necessary to obtain not only the form of this dependence, relying on the experimental data, but also to assess the influence of each factor on the lower calorific value. The analysis of the obtained dependence shows that the airflow speed and the fractional composition of this fuel have the greatest influence on the efficiency of the boiler plant. Checking the significance of the coefficients showed that all the coefficients of this model are significant. The regression dependencies were obtained that estimate the lower calorific value and the efficiency of the boiler which burns briquettes from organic matter; the analysis of the obtained dependencies was carried out, the significance of the coefficients included in the model was checked; the composition factor has the greatest influence on the lower calorific value.
Modeling the basis power in the systems for continuous transport of fluids and bulk materials
Authors: Dinolov O , Ilieva K
Published: January 2021

This paper presents a novel developed model for calculating the totally useful power in the systems for continuous transport of fluids and bulk cargoes, allowing deeper and more functional analysis of the energy efficiency of this systems by physically based decomposition of the electricity consumption of a useful and unhelpful ingredient. The model consists of nine mathematical expressions by which, after determining the type of system, the physically required minimum possible power consumption can be calculated and compared with the total consumption. A pumping system for the transport of condensate water from a deaerator to the drum of a steam generator of a thermal power plant has been selected as the subject of the model demonstration experiment. In the investigation carried out, the basis power of the pumping system was 606.6 kW and the total losses were about 302 kW. Other energy efficiency indices have also been identified. The researches should be continued in the direction of algorithmization of the model and its justification mainly for the Type II systems.
Development of innovative methods of thermal waste processing in modular waste burners with a high degree capture of harmful emissions
Authors: Orumbayev R K , Kibarin A A , Iliev I K , Torgayev A A , Kumargazina M B
Published: January 2021

Innovative methods have been developed for the thermal processing of solid waste in modular waste incineration plants with mechanical furnaces of boilers from 1.16 MW with gas afterburning over the layer and with a high degree of capture of harmful emissions in compact emulsifiers and activated carbon filters.
Wind energy assessment for low complex terrain using reference meteorological mast
Authors: Terziev A K , Panteleev Y , Ivanov M
Published: January 2021

The wind flow distribution over semi-complex terrains is evaluated by the roughness factor of the topography and the terrain peculiarities. The energy yield from the turbines in the park is based on the wind parameters extrapolated from the on-site measurement point to wind turbine hug height. For the lower zones of the terrain, the wind shear is influenced by the boundary layer, which can hardly be modeled using only tall tower data and a linear numerical model. The implementation of a second mast (reference), however, gives enough reliable data about the wind parameters at the lower part of the location and is used to adjust the flow and directional behavior from the main mast. The current study shows that for the low complex terrains using the proposed methodology an improvement of the assessed energy yield from the farm with 3% might be anticipated. Furthermore, for more complex terrains where the effect of the orography on the wind shear is more significant the expected improvement should be higher.
Estimation of wind speed and energy potential by atmospheric model for day-ahead market and wind power plants in Turkey
Authors: Devrim M A , Sakalli A
Published: January 2021

The requirement for energy has expanded day by day due to excessive consumption, developing technology, and population growth, especially after the Industrial Revolution. Since the investments for promoting renewable energy sources, The Turkish energy sector has been progressing in the way of renewable energy. This inevitable change in the energy sector and variable power generation values in wind energy directly affect the energy markets. Accompanying with the structural transformation of the energy sector, Turkey had launched the Day-Ahead electricity marketing system in December 2011. The price per megawatt-hour is determined on the open market by the supply and demand. Hatay province was selected in this study because of its highest wind potential. Temperature and wind speed values, observed in Hatay Samandağı for October 2019, were determined. The data was configured with The Weather Research and Forecasting Model. The results indicate that the wind speed at high altitudes could reach above 7 meters per second on Turkey’s eastern Mediterranean coast, Hatay. The results were compared with the real-time data, and the error rates were determined. In the selected region, the electrical energy values generated using the model results were calculated the day before.
Utilization of the energy potential of waste meal and creating of “green” workplaces
Authors: Mladenov M K , Yaneva S A
Published: January 2021

The issue of finding a suitable eco-technological approach for the utilization of waste meals generated in the production of vegetable oil is extremely relevant in terms of achieving a high “non-waste” degree in modern oil production. In practice, the direction related to the application of the meal as a material resource in animal husbandry is widely known – mainly for feeding of farm animals. At the same time, there are alternative areas related to other economic sectors, such as composting, biodiesel production, heat treatment and others, whose economic efficiency is still not sufficiently substantiated. Along with the topic of waste recovery, the measures for prevention of workers and ensuring safe and healthy working conditions are considered. The creation of “green” jobs, which directly or indirectly contribute significantly to the protection and restoration of the environment and to the reduction of the consumption of energy and raw materials, is extremely relevant in this direction.
Change point detection in recent hydropower generation in Romania
Authors: Neagoe A , Tică E-I , Popa F , Popa B
Published: January 2021

In Romania, about thirty percent of the installed capacity in National Power Grid and a third of the electricity generation is in hydropower plants. Thus, any aspect related to this form of renewable energy source is very valuable. Chronological records of yearly hydropower generation in Romania represent a time series that can be statistically analysed. The aim of this work is to determine the trend of this time series and, also, to locate the change points, where the time series has significant change. The period analysed is from 1980 to the present. To determine the change point of this time series, the Pettitt method was applied.
Plexiglass glove box for organic solar cells
Authors: Szolga L A , Stan C A
Published: January 2021

The term Glove Box probably creates an image of a glass box with black gloves, but Glove Boxes are as varied as the applications in which they are used. It is a hermetically sealed, watertight box, built for the purpose of sensitive applications. In this paper we present the design, the implementation and the testing of a Glove Box using plexiglass of 6mm thickness. The entire control of the system is flashed on an ATmega328 microcontroller. The sensors inside the box include oxygen sensor, gas sensor, humidity and temperature sensor. The plexiglass used provides robustness for the system but being lightweight it can be easily moved in different places in a research laboratory, compared with the steel Glove Boxes which are difficult to handle. The Glove Box was tested, by filling it up with Argon (inert gas) and introducing bulk heterojunction organic solar cells (BHJ OSC) and leaving them inside for 12hours. The measurement of the OSCs after 12h revealed that their efficiency decreased with only 20% compared to those left outside of the Glove Box which had an efficiency decrease of more than 70% from their initial value.