Статті в журналах з теми "Uneven heat load"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Uneven heat load.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 статей у журналах для дослідження на тему "Uneven heat load".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте статті в журналах для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Antipov, YU A., P. R. Val'yekho Malbdonado, P. P. Oshchepkov, I. K. Shatalov, and I. I. Shatalova. "Efficiency of a cogeneration plant based on a diesel engine under uneven electrical load conditions." Traktory i sel'hozmashiny 1, no. 5 (2020): 13–17. http://dx.doi.org/10.31992/0321-4443-2020-5-13-17.
Повний текст джерелаАнотація:
A feature of electrical energy is that it must be produced at a given moment as much as the con-sumer needs. However, the graphs of energy consumption are very uneven over the time of day. In order to cover peak loads, the highly mobile equipment, which is often less economical, is used. This equipment is operated at partial power modes, where its efficiency is markedly reduced. One of the real ways to get out of this situation can be the use of heat pumps (HP) in circuits with cogeneration units (CU) based on heat engines. In this case, it becomes possible to use the heat engine in an economical mode throughout the day, and direct excess electricity at night to the heat pump drive. The paper considers two options for the operation of a cogeneration plant based on a diesel engine in power supply schemes for an individual consumer under conditions of an uneven electrical load schedule. Wartsila 12V32 is taken as an example of a CU. Such plants are operated in different regions of the Russian Federation. The main data of the CU in the design mode are given. Diesel generator: electric power - 6000 kW, hourly fuel consumption - 1080 kg / h, thermal power - 5240 kW, exhaust gas temperature - 485 ° C, effective efficiency - 0.46, fuel heat utilization factor 0.89. In the first version, the CU operates in a standard mode. This ensures the generation of electrical power in accordance with the schedule. In the second version, the CU is used in conjunction with the HP to obtain additional thermal power. Calculations have shown that by including a heat pump in a cogeneration unit operating in an uneven electrical load schedule mode, it is possible to ensure that the diesel engine operates at maximum efficiency during the whole day and to increase the fuel heat utilization rate by 17-20%.
2
Li, Ming Hai, and Ding Ding Dong. "Finite Element Analysis of the Cylinder Liner of a 280 Diesel Engine." Advanced Materials Research 616-618 (December 2012): 1745–50. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.1745.
Повний текст джерелаАнотація:
The Cylinder liner is one of the key components of diesel engine. Combustion chamber set is constituted by Piston, Cylinder head, Cylinder liner and other parts. Its structure and working environment is complex. Received the gas pressure, friction force from high-speed reciprocating motion of the piston and lateral force of the piston, it results in mechanical stress and mechanical deformation. High temperature combustion and high pressure gas make the piston temperature distribution uneven, which results in piston thermal stress and thermal deformation. Therefore, the element analysis of Cylinder liner in the heat load and mechanical load is significant, the finite element analysis shows the deformation and the stress distribution of the Cylinder liner. It is meaningful for improving Cylinder liner design and reliability.
3
Yakovlev, P. V., V. A. Lebedev, and V. M. Piskunov. "Thermal conditions of load-bearing elements of radioactive waste storage facilities." E3S Web of Conferences 220 (2020): 01079. http://dx.doi.org/10.1051/e3sconf/202022001079.
Повний текст джерелаАнотація:
Facilities for storing radioactive waste with residual heat differ from other facilities in high safety standards in all operating conditions. A feature of these structures is the presence of biological protection in the form of walls and ceilings made of reinforced concrete with a large thickness. The combination of heat dissipation and the large thickness of walls and floors create conditions for the appearance of significant thermal stresses. This feature should be taken into account in the strength calculations of these buildings, taking into account the summation of seismic effects, gravitational forces and thermal stresses caused by uneven temperature fields in concrete. The paper presents the results of calculations of the combined effects of thermal stresses and earthquakes on a building. The data obtained made it possible to determine the features of the deformation of concrete structures with a combination of loads.
4
Zhang, Jie, and Tieshan Zhang. "Research on the Influence of Piston Constraint on the Temperature Field of Multi-disc Clutch." MATEC Web of Conferences 256 (2019): 02006. http://dx.doi.org/10.1051/matecconf/201925602006.
Повний текст джерелаАнотація:
The two-dimensional finite element model of multi-disc clutch friction pair was established by Abaqus simulation software, and the contact pressure of the friction surface under different piston constraints was calculated and analyzed. Considering contact pressure as the main heat-generating factor, the two-dimensional heat conduction process was numerically discretized by the implicit difference method. Then the temperature model of the multi-disc clutch friction pair was programmed in Matlab. The bench test verified the correctness of the temperature model. It is found that the temperature field between components is different and shows uneven distribution under the actual constraint. The local temperature of the component near the concentrated load is the highest, in which the radial temperature difference is the largest. The arrangement in which the piston pressure is concentrated in middle diameter produces the lowest temperature and the smallest radial temperature difference, which can effectively avoid thermal deformation of the component due to uneven temperature distribution.
5
Mellalou, Abderrahman, Walid Riad, Salma Kaotar Hnawi, Abdelaziz Tchenka, Abdelaziz Bacaoui, and Abdelkader Outzourhit. "Experimental and CFD Investigation of a Modified Uneven-Span Greenhouse Solar Dryer in No-Load Conditions under Natural Convection Mode." International Journal of Photoenergy 2021 (July 29, 2021): 1–12. http://dx.doi.org/10.1155/2021/9918166.
Повний текст джерелаАнотація:
An uneven-span modified greenhouse dryer was constructed and tested in no-load conditions under natural convection mode under the weather conditions of Marrakech, Morocco, for two distinct days. Moreover, a CFD evaluation of the uneven-span greenhouse dryer was performed as tool to visualize the air temperature distribution inside the dryer. For validating the CFD model, the temperature variations along the hours of the day were compared to the experimental results. A good agreement is obtained between the computed and measured inside air temperature with a difference not exceeding 8.46°C, with a correlation coefficient ( r ) and root mean square percentage deviations ( e ) 0.94 and 8.17, respectively. Furthermore, the maximum inside air temperature was measured to be 56°C and 52°C while the minimum inside relative humidity was measured to be 17% and 12%, for day-1 and day-2, respectively. The benefice of using asphalt as a floor covering material was revealed as an efficient way to heat the inside air at low solar radiations. The performances of the dryer were evaluated by the percentage of net heat gain variation as a way to validate the effectiveness of the dryer. This latter is found to be equal to 46% and 48% for the two days, respectively.
6
Borodulin, Boris B. "Algorithm for automatic compensation of thermal deformations of thermally loaded load-bearing structures." Vestnik of Samara State Technical University. Technical Sciences Series 29, no. 4 (December 15, 2021): 6–19. http://dx.doi.org/10.14498/tech.2021.4.1.
Повний текст джерелаАнотація:
The paper considers a possible algorithm for the automatic control system of the thermal modes of load-bearing structures of the information-measuring system of autonomous objects. Thermo-deformation component of information-measuring error, which is the cause of distortion of operating and service information of an autonomous object, is reduced due to compensation of thermogradient by automatic control system of operation modes of distributed controlled heat sources. The system provides a significant reduction in the level of thermal deformation error of measurements, the cause of which is the deformation of supporting structures due to unstable and uneven heat release of information-measuring instruments placed on the structure. To compensate for thermal deformations, the system includes controlled heat sources that compensate for the thermal gradients of the supporting structure arising under the influence of the information-measuring system instruments and external thermal radiation on the structure. An effective rational control algorithm, providing compensation of the thermal gradient of the load-bearing structure to an acceptable level, is proposed. The control algorithm and the system structure are designed to be implemented by special software of the onboard computer.
7
Luo, Zixue, Zixuan Feng, Bo Wu, and Qiang Cheng. "Decoupling Investigation of Furnace Side and Evaporation System in a Pulverized-Coal Oxy-Fuel Combustion Boiler." Energies 15, no. 7 (March 23, 2022): 2354. http://dx.doi.org/10.3390/en15072354.
Повний текст джерелаАнотація:
A distributed parameter model was developed for an evaporation system in a 35 MW natural circulation pulverized-coal oxy-fuel combustion boiler, which was based on a computational fluid dynamic simulation and in situ operation monitoring. A mathematical model was used to consider the uneven distribution of working fluid properties and the heat load in a furnace to predict the heat flux of a water wall and the wall surface temperature corresponding to various working conditions. The results showed that the average heat flux near the burner area in the air-firing condition, the oxy-fuel combustion with dry flue gas recycling (FGR) condition, and the oxy-fuel combustion with wet flue-gas recycle condition were 168.18, 154.65, and 170.68 kW/m2 at a load of 80%. The temperature and the heat flux distributions in the air-firing and the oxy-fuel combustion with wet FGR were similar, but both were higher than those in the oxygen-enriched combustion conditions with the dry FGR under the same load. This study demonstrated that the average metal surface temperature in the front wall during the oxy-fuel combustion condition was 3.23 °C lower than that under the air-firing condition. The heat release rate from the furnace and the vaporization system should be coordinated at a low and middle load level. The superheating surfaces should be adjusted to match the rising temperature of the flue gas while shifting the operation from air to oxy-fuel combustion, where the distributed parameter analytical approach could then be applied to reveal the tendencies for these various combustion conditions. The research provided a type of guidance for the design and operation of the oxy-fuel combustion boiler.
8
Wei, De Jian, and Xin Gui Zhang. "The Heat Exchange and Stress Distributing of Expansive Soil in Site." Applied Mechanics and Materials 130-134 (October 2011): 1650–53. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.1650.
Повний текст джерелаАнотація:
Expansive soil is called as “problem soil”, which has a characteristic of swelling by absorbing water and shrinking by losing water. So buildings and sub-grade which are built on expansive soil, are easier to damage for lager deformation. Due to the large-scale urban construction, ground surface was covered in a wide range. For example, in tropics and subtropics areas, the water transfer in the expansive soil is influenced by the gradient of temperature, which is different between the central area under the road surface and road-side bare area. Because of the hysteresis of water transfer, the water content distributing is not uniform, which lead to the different swell-shrink performance in different zone, herewith will change some parameters of the expansive soil and finally affect its stress field and the displacement field. Take the road as the example: The road is a strip belt-shaped coverage. Both in dry and wet season, the thermodynamic field and water-flowing field is uneven between the central area under the road surface and road-side bare area, so the displacement field and the stress field on the cross-section under the road is uneven. Under the load of vehicle, the non-uniformity stress distributing in the soil is further aggravated, and the same to the displacement in the underlying sub-grade, which is a significant factor in aggravating the dehiscence of road surface. Comparing to general soil, expansive soil has a completely different distribution of temperate field and water-flowing condition because of its swell-shrink characteristic. By studying on the relationship between the thermodynamic field and the stress-strain in the expansive soil, it can find out how the climate affect the engineering expansive soil, and provide the theory basis for improving expansive soil.
9
Kalabin, D. A., A. Yu Lipovka, and Yu L. Lipovka. "Computer simulation and full-scale measurements of the load flow in a functioning heating network." Proceedings of Irkutsk State Technical University 25, no. 1 (March 20, 2021): 44–56. http://dx.doi.org/10.21285/1814-3520-2021-1-44-56.
Повний текст джерелаАнотація:
The article aims to identify patterns in the distribution of heating energy to consumers with a varying availability of regulation equipment under real conditions of a central heating network, as well as to compare the results of computer simulation with full-scale measurements. For computer simulation, well-known mathematical methods for calculating the load flow in hydraulic circuits were used. Experimental studies of the operation modes of heat supply systems were carried out using the data of the control and monitoring systems of thermal power plants using the Siemens Simatic PCS7 software, a Portaflow 300 ultrasonic flow meter, stationary electromagnetic flow transducers, verified and certified manometers and thermometers. The graphs of the actual hydrodynamic modes of the heating network under study were obtained at outdoor air temperatures from +8 to -37°C, as well as under abnormal conditions (temperature drop in the supply pipeline and pressure drop at the heating network input). It was proposed to use jointly the simulation by means of the JA_Net software and full-scale measurements of the thermohydraulic operating modes of a centralised heat supply system, whose consumers have a various degree of regulation equipment. It was shown that the proposed complex method of qualitative and quantitative assessment of the efficiency of district heating networks makes it possible to identify the features of control of their hydraulic modes when connecting new consumers with a varying degree of automation. According to the obtained characteristics of changes in the flow rate of the coolant in the consumers’ internal systems depending on the pressure drop at the tie-in point, the lack of response to emergency situations on part of the consumers whose heat supply systems are equipped with the means of qualitative and quantitative regulation of the heat load, is associated with the process of automatic adjustment of the degree of opening of flow controllers and control valves at individual points. In future work, we will develop guidelines for levelling the imbalance of the heating network under the conditions of uneven provision of facilities with automation equipment when implementing projects for the complex modernisation of heat consumers or connecting new facilities to existing heat supply networks.
10
Demchenko, Vladimir, Alina Konyk, and Vladimir Falko. "Mobile Thermal Energy Storage." NTU "KhPI" Bulletin: Power and heat engineering processes and equipment, no. 3 (December 30, 2021): 44–50. http://dx.doi.org/10.20998/2078-774x.2021.03.06.
Повний текст джерелаАнотація:
The article is devoted to topical issues related to the storage, accumulation and transportation of heat by stationary and mobile heat storage. Analysis of the current state of the district heating system indicates significant heat losses at all stages of providing the consumer with heat. The use of heat storage in heat supply systems leads to balancing the heat supply system, namely, the peak load is reduced; heat production schedules are optimized by accumulating excess energy and using it during emergency outages; heat losses caused by uneven operation of thermal equipment during heat generation are reduced; the need for primary energy and fuel consumption is reduced, as well as the amount of harmful emissions into the environment. The main focus is on mobile thermal batteries (M-TES). The use of M-TES makes it possible to build a completely new discrete heat supply system without the traditional pipeline transport of the heat carrier. The defining parameters affecting the efficiency of the M-TES are the reliability and convenience of the design, the efficiency and volume of the “working fluid”, the operating temperature of the MTA recharging and the distance of transportation from the heat source to the consumer. The article contains examples of the implementation of mobile heat accumulators in the world and in Ukraine, their technical and technological characteristics, scope and degree of efficiency. The technical indicators of the implemented project for the creation of a mobile heat accumulator located in a 20-foot container and intended for transportation by any available means of transport are given.
11
Mu, Mingfei, Lizhuang Dou, Jawad Aslam, and Bisheng Chen. "Synergy Analysis of the Influence of the Connection Cone on the Thermal Distribution during Regeneration." Symmetry 13, no. 6 (June 2, 2021): 995. http://dx.doi.org/10.3390/sym13060995.
Повний текст джерелаАнотація:
Diesel particulate filters (DPF) are typically used for particle filtration in vehicle exhausts after a treatment system. The monolith inside a DPF is a symmetrical column structure, frequently an axisymmetric cylinder structure where filtration and regeneration occur. Due to the complex structure before the symmetric monolith, the internal particle distribution is not uniform, which leads to an uneven temperature change when regeneration occurs. During thermal regeneration, the temperature field inside a DPF is affected by the particle load, exhaust temperature and exhaust flow. The relationship between the temperature gradient and velocity vector is also a key factor influencing regeneration performance. Based on the particle-loading test method, a bench for thermal distribution testing during regeneration was built. Via experiments and simulations, the temperature field in an axisymmetric monolith during particle combustion given an uneven particle distribution was analyzed. Through field synergy analysis of the temperature and velocity fields in the monolith, the influence of connection cones with different structures on heat transfer enhancement was studied. The results indicated that compared with a monolith with a conventional linear cone, the radial temperature gradient is 1.1 °C/mm lower, the area of enhanced regeneration is larger, and the regeneration rate is improved in the monolith with a streamlined cone.
12
Novosád, Jan, Pavel Peukert, and Marcel Havrda. "Improvement of the Combustion Chamber." MATEC Web of Conferences 328 (2020): 02011. http://dx.doi.org/10.1051/matecconf/202032802011.
Повний текст джерелаАнотація:
The subject of this work is the analysis of an independent heater combustion chamber. The main goals are the analysis of the current state and modification of the combustion chamber design, while the CFD methods are applied. The standard methodology considering the model and grid preparation and the ANSYS Fluent solver setup were provided to obtain the velocity, thermal and species concentration fields as results. These results were used for the analysis of the flame stability as well as the heat load of the individual component of the combustion chamber. The initial results leads to the identification of areas for possible improvement due to the uneven thermal fields and high thermal stress. Then, several modifications were designed and tested. Finally, the results for modified design were analysed to evaluate the variant suitable for future experimental testing.
13
Chang, Xinyu, Koji Fujita, and Hiroki Nagai. "Numerical Analysis of Wick-Type Two-Phase Mechanically Pumped Fluid Loop for Thermal Control of Electric Aircraft Motors." Energies 15, no. 5 (February 28, 2022): 1800. http://dx.doi.org/10.3390/en15051800.
Повний текст джерелаАнотація:
The development of thermal control systems has become an important issue in next-generation electric aircraft design due to the increase in heat exhausted with electrification. In this paper, a wick-type two-phase mechanically pumped fluid loop system for future electric aircraft was proposed through the investigation of current two-phase flow cooling technology. Taking the experimental electric aircraft X-57 as an example, a wick-type two-phase mechanically pumped fluid loop with four evaporators for transporting 12 kW of waste heat within an 80 °C temperature limit was proposed and its feasibility was confirmed. A numerical model was constructed and validated to predict the operating characteristics of a two-phase mechanically pumped fluid loop. The optimal pump outputs under-even and uneven heat load conditions and was investigated for the first time by considering the vapor-liquid separation conditions in each flow path and the power consumption of the pump. Under the optimal pump output condition, the operating characteristics of the wick-type two-phase mechanically pumped fluid loop system were calculated. The calculation results indicate that the proposed wick-type two-phase mechanically pumped fluid loop is suitable as the thermal control system for an X-57 electric aircraft motor, as the calculation results satisfied the operational requirements of the motor.
14
Jebaraj, Bharath Singh, Jaison Bennet, Raju Kannadasan, Mohammed H. Alsharif, Mun-Kyeom Kim, Ayman A. Aly, and Mohamed H. Ahmed. "Power Quality Enhancement in Electric Arc Furnace Using Matrix Converter and Static VAR Compensator." Electronics 10, no. 9 (May 10, 2021): 1125. http://dx.doi.org/10.3390/electronics10091125.
Повний текст джерелаАнотація:
In recent years, non-linear loads on the distribution side are increasing rapidly. Notably, the electric arc furnace (EAF) is the most used non-linear load due to its diverse applications for industrial needs. However, EAF has some disadvantages like uneven distribution of heat inside the furnace, release of unwanted gases, increased level of harmonics, and Flickers in voltages. Specifically, power quality concerns are more and need comprehensive solutions. In this work, a matrix converter (MC) along with static VAR compensator (SVC) is proposed, and the hybrid exponential-hyperbolic furnace model is adapted in MATLAB platform. Simulations are carried out for different cases and the observed results are compared with existing methodologies. It was perceived that the power quality parameters such as peak current and voltages, total harmonic distortions (THDs), voltage flickers, and power factors are enhanced compared with existing methodologies. Precisely, the THD of current and voltage attains a prime rate of about 2.85% and 29.54%, respectively. Moreover, the proposed model’s voltage flicker and power factor offer a grander scale of about 1.26% and 0.9975, respectively. The enhanced scheme provides more significant advantages to the large-scale steel manufacturing plant with EAF.
15
SEREDA, B. P., V. I. SUKHOMLIN, V. I. VOLOKH, and D. B. SEREDA. "ANALYSIS OF THE REASONS FOR CRACKING PIPES OF THE BOILER OF THE RECOVERY." Ukrainian Journal of Civil Engineering and Architecture, no. 1 (June 24, 2021): 95–101. http://dx.doi.org/10.30838/j.bpsacea.2312.230221.96.723.
Повний текст джерелаАнотація:
8-381X
Abstract. Formulation of the problem. One of the main tasks of production is reliable and trouble-free operation of equipment. In the oxygen-envelope process, when cast iron is purged, a large amount of carbon monoxide CO is emitted in the converter, which has a high temperature of more than 1 700 °С of the outgoing gases. The envelope gases in the waste heat boiler are cooled. Converter gas output is characterized by cyclic unevenness In this case, uneven heating of the walls of the boiler pipes occurs. By circulation pumps, chemically purified water is supplied for forced cooling of the boiler walls. When raising the outgoing gases, the cooling water is converted to pars by its subsequent supply to the consumer. The study is dedicated to solving the scientific and applied problem for the reasons for the formation of defects and the identification of cracks in the pipes of the recovery boiler.The purpose of the work. To investigate the causes of the development of transverse cracks in the pipelines of the recovery boiler by various methods of non-destructive testing, to use the methods of scanning microscopy to analyze the microstructure, mechanical tests, and the magnetic properties of structural carbon steel. Conclusions. One of the main reasons for the appearance of massive cracks in the pipes of cylindrical caissons is thermal fatigue caused by high thermal loads. Transverse cracks have the character of thermal fatigue failure, which is confirmed by changes in the ferrite-pearlite structure of the metal, resulting from uneven local cooling of the walls of the caisson. The reasons for the violation of the water circulation in the boiler are the pressure drop in the boiler and a sharp discharge, the load is the release of water from the boiler.
16
Ma, Biao, Likun Yang, Heyan Li, and Nan Lan. "Hot judder behavior in multidisc clutches." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 231, no. 1 (August 5, 2016): 136–46. http://dx.doi.org/10.1177/1350650116648069.
Повний текст джерелаАнотація:
This paper presents an investigation of the hot judder phenomenon of multidisc clutches, which takes place during the engagement process. Depending on the results of finite element analysis, a pressure distribution function is defined and a contact pressure equation is established to demonstrate the non-uniformity of the contact pressure distribution on the friction interfaces due to frictional heat. The relationship between the coefficient of friction and the temperature is analyzed. A 4 degrees of freedom power-train model is developed to evaluate the clutch judder behavior. The paper indicates that the clutch judder is influenced by the non-uniformity of the interface contact pressure distribution, which is excited by frictionally induced thermal load. The non-uniform contact pressure distributions along the radial direction have a slight influence on the clutch judder, while the uneven contact pressure distributions along the circumference contribute to the judder substantially. Furthermore, the results in this work can be used to study the operation instability and the thermal failure of clutches.
17
Cabrini, Marina, Sara Bocchi, Gianluca D'Urso, Claudio Giardini, Sergio Lorenzi, Cristian Testa, and Tommaso Pastore. "Stress Corrosion Cracking of Friction Stir-Welded AA-2024 T3 Alloy." Materials 13, no. 11 (June 8, 2020): 2610. http://dx.doi.org/10.3390/ma13112610.
Повний текст джерелаАнотація:
The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding AA-2024 T3 joints. Constant load (CL) cell and slow strain rate (SSR) tests were carried out in aerated NaCl 35 g/L solution. During the tests, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were measured in the different zones of the welding. The results evidenced initial practical nobilty of the nugget lower compared to both heat-affected zone and the base metal. This effect can be mainly ascribed to the aluminum matrix depletion in copper, which precipitates in form of copper-rich second phases. In this zones, no stress corrosion cracking was noticed, but well-evident stress-enhanced intergranular corrosion occurred. This is due to the uneven distribution of platic deformation during the slow strain rate tests. Higher strain values are localized at the heat affected zone, where softening occurs. On the contrary, stress values at the nugget are not sufficient to favor both the initiation and propagation of stress corrosion cracks. In the range of processing parameter studied in this experimental work, the stress corrosion cracking susceptibility of the friction stir welding (FSW)-ed alloy is then similar to that of the base metal.
18
Chuikina, A. A., M. Ya Panov, and S. N. Kuznetsov. "DEVELOPMENT OF A METHODOLOGYFOR DETERMINING THE BEST OPTION FOR THE ROUTE OF THE HEAT NETWORK AT THE INITIAL DESIGN STAGE." Russian Journal of Building Construction and Architecture, no. 4(52) (November 19, 2021): 36–43. http://dx.doi.org/10.36622/vstu.2021.52.4.003.
Повний текст джерелаАнотація:
Statement of the problem. Choosing the best option for the route of the thermal network at the initial stage of design is a complex multifactorial task, in addition, due to the lack of a number of necessary design calculations, its solution is accompanied by a limited set of initial data. Thus, it becomes relevant to develop a new methodology for designing the optimal route of the heat supply system considering the qualitative and quantitative characteristics of the discussed object.Results. A mathematical model of a generalized additive vector optimality criterion has been developed, taking into account the material consumption of the heat network, its reliability, construction time, annual thermal losses, heat turnover and temperature dispersion at the consumer. A method is proposed for determining the best option for the route of a thermal network at the initial design stage by jointly solving the optimization problem using vector optimization and matrix generalization methods. The expediency of the joint application of the methods of pairwise comparison and vector optimization in solving the problem under consideration is noted.Conclusions. An important characteristic of the developed mathematical model of the generalized criterion is the possibility of obtaining a more accurate solution to the optimization problem under consideration with an uneven distribution of the heat load by means of a biased estimate of the temperature variance among consumers. A combination of the methods of matrix generalization, pairwise comparison and vector optimization can improve the accuracy of the calculation while solving the optimization problem of choosing the best route of the thermal network.
19
Kusumawardani, Chaterina Diyah Nanik, Ronaldo Triputro Chondro, Ivan Andrian, and Rima Parwati Sari. "Pengaruh penambahan hidroksiapatit terhadap porositas dan compressive strength basis resin akrilik heat-curedEffect of hydroxyapatite addition towards porosity level and compressive strength of heat-cured acrylic resin base." Jurnal Kedokteran Gigi Universitas Padjadjaran 32, no. 2 (August 31, 2020): 91. http://dx.doi.org/10.24198/jkg.v32i2.26627.
Повний текст джерелаАнотація:
Pendahuluan: Resin akrilik heat cured (HC) merupakan pilihan utama bahan sebagai basis gigi tiruan. Hidroksiapatit (HAP) adalah molekul kristalin yang sudah banyak digunakan di kedokteran gigi. Penelitian terdahulu membuktikan bahwa HAP mampu mengurangi monomer sisa pada resin akrilik HC, yang akan mengurangi juga porositas resin akrilik tersebut. Berkurangnya porositas resin akrilik, diharapkan akan meningkatkan kekuatan mekanik resin akrilik tersebut. Tujuan penelitian menganalisis pengaruh penambahan hidroksiapatit terhadap porositas dan compressive strength resin akrilik HC. Metode: Jenis penelitian eksperimental laboratoris. Sampel penelitian 20 resin akrilik HC berbentuk silindris (6x3mm), dibagi menjadi 4 kelompok. Kelompok kontrol (tanpa penambahan HAP), kelompok HAP 2%, kelompok HAP 5%, dan kelompok HAP 10%. Permukaan sampel diteliti menggunakan SEM untuk porositasnya. Penghitungan compressive strength sampel menggunakan Universal Testing Machine (load cell 300kg/mm2). Hasil: Uji one-way ANOVA dan Tukey-HSD menunjukkan perbedaan signifikan (p<0,05) antara kelompok kontrol (90±13,5MPa) dengan 5%HAP (105±4,3MPa) dan 10%HAP (113±10,2MPa), begitu pula antara 2%HAP (96±8,4MPa) dengan 10%HAP. Uji SEM menunjukkan tidak adanya reaksi kimia antara HAP dan resin akrilik HC. Tampak pula bercak putih tersebar tidak merata pada permukaan sampel akrilik di kelompok-kelompok perlakuan. Bercak putih ditemukan meningkat sebanding dengan peningkatan konsentrasi HAP, dengan diameter yang semakin besar. Simpulan: Penambahan HAP pada basis resin akrilik HC mampu menurunkan tingkat porositas dan meningkatkan nilai compressive strength. Penurunan tingkat porositas meningkat seiring dengan penambahan HAP. Compressive strength yang paling tinggi didapatkan pada basis resin akrilik heat cured dengan penambahan 10% hidroksiapatit.Kata kunci: Compressive strength, uji SEM, resin akrilik heat cured, hidroksiapatit. ABSTRACT Introduction: Heat-cured acrylic resin has been commonly used as a denture base, whereas hydroxyapatite (HAP) is a crystalline molecule widely used in the field of dentistry. Previous research has been proofed that HAP could reduce the residual monomer of heat-cured acrylic resin, which will reduce the porosity level in advance, so it was expected for better mechanical properties. This research was aimed to analyse the effect of HAP addition towards the porosity level and compressive strength of heat-cured acrylic resin. Methods: An experimental laboratory research was conducted towards 20 cylindrical samples (6 x 3 mm) of heat-cured acrylic resins, which were divided into four groups: Control group (without HAP addition), 2% HAP addition group, 5% HAP addition group, and 10% HAP addition group. Compressive strength was tested using Universal Testing Machine (load cell of 300kg / mm2). Each sample surface porosity was observed using the scanning electron microscope (SEM). Results: One-way ANOVA and Tukey-HSD tests results showed significant differences (p < 0.05) between compressive strength in the control group (90 ± 13.5 MPa) compared to 5% (105 ± 4.3 MPa) and 10% HAP addition group (113 ± 10.2 MPa), significant differences were also shown between the 2% (96±8.4MPa) and 10% HAP addition group. SEM imaging showed that there was no chemical reaction between HAP and heat-cured acrylic resin. It showed uneven white spots in acrylic sample’s surface in all treatment groups. Those white spots were likely to be found more in the higher concentration of HAP, so did the diameter of white spots was also found more in the higher concentration. Conclusion: The addition of hydroxyapatite to the base of heat-cured acrylic resin can reduce the level of porosity and increase the compressive strength value. The decrease in the porosity level increases with the addition of hydroxyapatite. The highest compressive strength is obtained with the addition of 10% hydroxyapatite.Keywords: Compressive strength, SEM imaging, heat-cured acrylic resin, hydroxyapatite.
20
Graffeo, Federica, Silvio Vaschetto, Alessio Miotto, Fabio Carbone, Alberto Tenconi, and Andrea Cavagnino. "Lumped-Parameters Thermal Network of PM Synchronous Machines for Automotive Brake-by-Wire Systems." Energies 14, no. 18 (September 8, 2021): 5652. http://dx.doi.org/10.3390/en14185652.
Повний текст джерелаАнотація:
Thermal analysis represents a key factor in electrical machine design due to the impact of temperature increase on insulation lifetime. In this context, there has been a wide investigation on thermal modeling, particularly for machines used in harsh working conditions. In this perspective, brake-by-wire (BBW) systems represent one of the most challenging applications for electrical machines used for automotive smart actuators. Indeed, electro-actuated braking systems are required to repeatedly operate the electric machine in high overload conditions in order to limit the actuator response time, as well as to enhance gravimetric and volumetric specific performance indexes. Moreover, BBW systems often impose unconventional supply conditions to the electric machine, consisting of dc currents in three-phase windings to keep the rotor fixed during the braking intervals. However, a dc supply leads to uneven temperature distributions in the machine, and simplified thermal models may not accurately represent the temperature variations for the different machine parts. Considering such unconventional supply conditions, this paper initially investigates the applicability of a conventional lumped-parameters thermal network (LPTN) based on symmetry assumptions for the heat paths and suitable for surface-mounted PM synchronous machines used in BBW systems. An extensive test campaign consisting of pulses and load cycle tests representative of the real machine operations was conducted on a prototype equipped with several temperature sensors. The comparison between measurements and predicted average temperatures, together with insights on the unbalanced heat distribution under the dc supply obtained by means of finite element analyses (FEA), paved the way for the proposal of a phase-split LPTN with optimized parameters. The paper also includes a critical analysis of the optimized parameters, proposing a simplified, phase-split lumped-parameters thermal model suitable to predict the temperature variations in the different machine parts for PM synchronous electric machines used in BBW systems.
21
Pan, Zhi Yong, Sheng Yin Song, Wen Hong Liu, Jian Jun Wang, and Xin Hu Wang. "Cause Analysis of Buttress Premium Thread Connection Pullout for a Well." Advanced Materials Research 337 (September 2011): 627–32. http://dx.doi.org/10.4028/www.scientific.net/amr.337.627.
Повний текст джерелаАнотація:
The buttress thread connection was used in deep well or ultra-deep well widely because of its high joint efficiency. Pullout failure scarcely happen on buttress premium thread connection with great joint strength and good sealing property. Direct evidences about connection dropout couldn’t get in most cases by reason of casing string had fallen into well or casing string had been concreted in formation by cement. Now the difficulty of analysis on pullout is higher and higher. A buttress premium thread casing joint had pulled out at mill end of coupling in a straight well and dropout casing string couldn’t get out of the well. Research on this pullout case was carried out combining relative theories with tests. Macroscopic analysis and dimension measurement were done for dropout coupling. The material’s physical and chemical properties were checked. Thread inspection and full-scale tests were done for two casing simples that are same lot with pullout. Metallograph analysis was carried out on load flank and guide flank in box thread of pullout coupling and same lot new coupling. The results showed that dropout failure was ascribe to inadequate make-up torque at mill end of pullout coupling and complex downhole condition and improper handling in the oil field. On the other hand joint’s strength decline on the effect of unsuitable heat treatment to coupling and greatly uneven black crested pin thread around circumference. The pertinence measures were laid down at the end of this passage.
22
Фролов, Є. А., та В. В. Муравльов. "ДОСЛІДЖЕННЯ ВПЛИВУ НЕРІВНОМІРНОСТІ ЦЕМЕНТОВАНОГО ШАРУ НА НЕСУЧУ ЗДАТНІСТЬ БАЗОВИХ ТА ОПОРНО-КОРПУСНИХ ДЕТАЛЕЙ УНІВЕРСАЛЬНО-ЗБІРНИХ ПРИСТОСУВАНЬ". Open Information and Computer Integrated Technologies, № 88 (6 листопада 2020): 95–103. http://dx.doi.org/10.32620/oikit.2020.88.07.
Повний текст джерелаАнотація:
The article contains analysis of the uneven cemented layer effect upon the bearing capacity of the base and supporting parts of versatile prefabricated welded work tools. The issue was studied as there is a lack of data on contact deformations, which are necessary for further calculation of assembly errors due to thermal deformations. Fluctuations of the cemented layer depth along the base part surface negatively affect the contact of the tool base surfaces. This issue is especially acute when expanding the scope of application of reconfigurable reusable technological equipment, which would be cost-effective in terms of serial multi-item production of welded structures.The relation between microhardness and the value of the polished cemented layer was determined during testing of 12 ХН3А steel samples, cemented to a depth of 2.4 mm and hardened to a hardness of HRC 60-62. Obtained relation between the microhardness and polished layer thickness has shown that with increasing polished layer, the microhardness decreases. This leads to a decrease in the critical load, under which recoverable deformations of irregularities transit into plastic deformations. The ratio of the actual planes of contact, where the recoverable deformation of microroughnesses appoears when approaching and penetration of harder irregularities into soft ones occurs, will be proportional to the ratio of the nominal planes of the cemented and raw layers.As a result of processing the test data, the relation between critical pressure and cemented layer thickness has been got. Microroughnesses at lower loads will be deformed plastically, reducing the bearing capacity of base surfaces, which is unacceptable for parts of tools and affects their service life. It follows from the above that the unevenness of the cemented layer depth of the front surfaces of the base and supporting parts is a negative phenomenon that impairs their performance. It is necessary to use a process that ensures minimal distortion of the part during heat treatment and a stable depth of the cemented layer.
23
Чуйкина, А. А. "Development of a Methodology for Determining the Best Option for the Route of the Heat Network at the Initial Design Stage." НАУЧНЫЙ ЖУРНАЛ СТРОИТЕЛЬСТВА И АРХИТЕКТУРЫ, no. 3(63) (September 24, 2021): 57–64. http://dx.doi.org/10.36622/vstu.2021.63.3.005.
Повний текст джерелаАнотація:
Постановка задачи. Выбор наилучшего варианта трассы тепловой сети на начальном этапе проектирования является сложной многофакторной задачей, кроме того, ввиду отсутствия ряда необходимых конструктивных расчетов ее решение сопровождается ограниченностью набора исходных данных. Таким образом, становится актуальной разработка новой методики проектирования оптимальной трассы системы теплоснабжения, учитывающей качественные и количественные характеристики рассматриваемого объекта. Результаты. Разработана математическая модель обобщенного аддитивного векторного критерия оптимальности, учитывающая материалоемкость тепловой сети, ее надежность, время строительства, годовые тепловые потери, оборот теплоты и дисперсию температуры у потребителя. Предложен способ определения наилучшего варианта трассы тепловой сети на начальном этапе проектирования путем совместного решения задачи оптимизации методами векторной оптимизации и матричного обобщения. Отмечена целесообразность совместного применения методов попарного сравнения и векторной оптимизации при решении рассматриваемой задачи. Выводы. Важной характеристикой разработанной математической модели обобщенного критерия является возможность получения более точного решения рассматриваемой оптимизационной задачи при неравномерным распределении тепловой нагрузки посредством смещенной оценки дисперсии температуры у потребителей. Совместное применение методов матричного обобщения, попарного сравнения и векторной оптимизации позволяет повысить точность расчета при решении оптимизационной задачи выбора наилучшей трассы тепловой сети. Statement of the problem. Choosing the best option for the route of the thermal network at the initial stage of design is a complex multifactorial task, in addition, due to the lack of a number of necessary design calculations, its solution is accompanied by a limited set of initial data. Thus, it becomes relevant to develop a new methodology for designing the optimal route of the heat supply system, taking into account the qualitative and quantitative characteristics of the object under consideration. Results. A mathematical model of a generalized additive vector optimality criterion has been developed, taking into account the material consumption of the heat network, its reliability, construction time, annual thermal losses, heat turnover and temperature dispersion at the consumer. A method is proposed for determining the best option for the route of a thermal network at the initial design stage by jointly solving the optimization problem using vector optimization and matrix generalization methods. The expediency of the joint application of the methods of pairwise comparison and vector optimization in solving the problem under consideration is noted. Conclusions. An important characteristic of the developed mathematical model of the generalized criterion is the possibility of obtaining a more accurate solution to the optimization problem under consideration with an uneven distribution of the heat load by means of a biased estimate of the temperature variance among consumers. The combined application of the methods of matrix generalization, pairwise comparison and vector optimization can improve the accuracy of the calculation when solving the optimization problem of choosing the best route of the thermal network.
24
Krysiński, Lech, Marek Grad, Rolf Mjelde, Wojciech Czuba, and Aleksander Guterch. "Seismic and density structure of the lithosphere−asthenosphere system along transect Knipovich Ridge−Spitsbergen−Barents Sea – geological and petrophysical implications." Polish Polar Research 34, no. 2 (June 1, 2013): 111–38. http://dx.doi.org/10.2478/popore-2013-0011.
Повний текст джерелаАнотація:
AbstractThis paper presents a study of the seismic P−wave velocity and density structure of the lithosphere−asthenosphere system along a 800 km long transect extending from the actively spreading Knipovich Ridge, across southern Spitsbergen to the Kong Karls Land Volcanic Province. The 2D seismic and density model documents 6-8 km thick oceanic crust formed at the Knipovich Ridge, a distinct continent−ocean−boundary (COB), the east− ern boundary of the dominantly sheared Hornsund Fault Zone, and the eastern boundary of the Early Cenozoic West Spitsbergen Fold−and−Thrust Belt. The crustal continent−ocean transitional zone has significant excess of density (more than 0.1 g/cm3in average), charac− teristic for mafic/ultramafic and high−grade metamorphic rocks. The main Caledonian su− ture zone between Laurentia and Barentsia is interpreted based on variations in crustal thickness, velocities and densities. A high velocity body in the lower crust is preferably in− terpreted in terms of Early Cretaceous magmatism channelled from an Arctic source south− wards along the proto−Hornsund zone of weakness. The continental upper mantle expresses high velocities (8.24 km/s) and densities (3.2 g/cm3), which may be interpreted in terms of low heat−flow and composition dominated by dunites. The lower velocities (7.85 km/s) and densities (3.1 g/cm3) observed in the oceanic lithosphere suggest composition dominated by primitive peridotites. The model of mantle allows for successful direct description of subcrustal masses distribution compensating isostatically uneven crustal load. The esti− mated low value of correlation between density and velocity in the mantle 0.12 kg·s·m−4suggests that horizontal density differences between oceanic and continental mantle would be dominated by compositional changes.
25
Pei, Xin, Lu Huang, Wei Pu, and Pengchong Wei. "Dynamical wear prediction along meshing path in mixed lubrication of spiral bevel gears." Advances in Mechanical Engineering 12, no. 9 (September 2020): 168781402095823. http://dx.doi.org/10.1177/1687814020958236.
Повний текст джерелаАнотація:
Surfaces of gears under combined rolling and sliding motions may suffer a complicated wear process due to the transient time-varying effect along the meshing path. In this paper, a methodology for predicting the wear of tooth surfaces is developed for the spiral bevel gears. In the wear model, the machined surface roughness, mixed lubrication, friction, flash temperature and the dynamic behavior of gears are all considered. Tooth-Contact-Analysis (TCA) method is used to get the time-varying parameters of meshing points along the meshing path. By simulating real movement process, the material is removed according to the Arrhenius equation. First, the distribution of pressure and film thickness is obtained by solving the mixed EHL model. After that, the flash temperature can be computed by the point heat source integration method with the obtained pressure, film thickness and velocity vector. The material removal is based on surface temperature and sliding distance. The numerical results are compared to the ball-on-disk experiments to demonstrate the reasonableness of the present wear model. And it shows that the angle difference between velocity vectors has strong influences on the wear profile. Furthermore, the mechanism of surface wear evolution is investigated systematically in spiral bevel gears. The difference of the wear track between the pinion and gear surfaces is observed. Besides, in the meshing process of tooth surface, the wear along the meshing path is uneven, which appears to be much greater at the engaging-in and engaging-out areas. There is a position with maximum wear rate in the meshing process, and the position is affected by the load and speed.
26
Shelgunov, A. V. "Cost-effective use of autonomous power sources." Power and Autonomous equipment 2, no. 1 (March 28, 2019): 50–57. http://dx.doi.org/10.32464/2618-8716-2019-2-1-50-57.
Повний текст джерелаАнотація:
Introduction: the chapter “Introduction” contains information on the economic benefits of building your own sources of heat and electricity. Methods: the chapter “Methods” presents natural gas as the main fuel resource of the Russian Federation. In this regard, the expediency of the use of gas piston and gas turbine installations is emphasized. It is also noted that the gas piston unit (GPU) has the highest efficiency. In confirmation of this statement is a brief calculation of the efficiency of this installation. Results and discussions: this chapter discusses the effectiveness of the use of a gas piston cogeneration plant on the example of a company engaged in the processing of recycled metal. Based on the electricity consumption graph, it shows the uneven use of energy during the day. In accordance with the data obtained, the average load of the GPU and its capacity are determined. Based on the available source data, the calculation of the cost of maintaining the GPU and the production of electrical and thermal energy. Also in the chapter “Results and Discussions” it is emphasized that in developing the prozhect, it is necessary to involve the design organization, which will make a complete survey of the obzhect, study the annual energy consumption graphs, determine the necessary equipment and the volume of construction and installation work. At the same time, this chapter focuses on the fact that additional savings are provided by attracting leasing equipment purchase schemes. Conclusion: in the chapter “Conclusions” it is noted that the relevance and efficiency of the autonomous power supply additionally provides not only financial benefits, but also allows, in a shorter time, to provide obzhects with energy, to increase capacity in addition to the existing ones and to avoid unpredictable energy suppliers tariffs.
27
Kalashnikov, Kirill, Andrey Chumaevskii, Tatiana Kalashnikova, Aleksey Ivanov, Valery Rubtsov, Evgeny Kolubaev, and Vladimir Bakshaev. "On the problem of tool destruction when obtaining fixed joints of thick-walled aluminum alloy blanks by friction welding with mixing." Metal Working and Material Science 23, no. 3 (September 15, 2021): 72–83. http://dx.doi.org/10.17212/1994-6309-2021-23.3-72-83.
Повний текст джерелаАнотація:
Introduction. Among the technologies for manufacturing rocket and aircraft bodies, marine vessels, and vehicles, currently, more and more attention is paid to the technology of friction stir welding (FSW). First of all, the use of this technology is necessary where it is required to produce fixed joints of high-strength aluminum alloys. In this case, special attention should be paid to welding thick-walled blanks, as fixed joints with a thickness of 30.0 mm or more are the target products in the rocket-space and aviation industries. At the same time, it is most prone to the formation of defects due to uneven heat distribution throughout the height of the blank. It can lead to a violation of the adhesive interaction between the weld metal and the tool and can even lead to a destruction of the welding tool. The purpose of this work is to reveal regularities of welding tool destruction depending on parameters of friction stir welding process of aluminum alloy AA5056 fixed joints with a thickness of 35.0 mm. Following research methods were used in the work: the obtaining of fixed joints was carried out by friction welding with mixing, the production of samples for research was carried out by electric erosion cutting, the study of samples was carried out using optical metallography methods. Results and discussion. As a result of performed studies, it is revealed that samples of aluminum alloy with a thickness of 35.0 mm have a heterogeneous structure through the height of weld. There are the tool shoulder effect zone and the pin effect zone, in which certain whirling of weld material caused by the presence of grooves on tool surface is distinctly distinguished. It is shown that the zone of shoulders effect is the most exposed to the formation of tunnel-type defects because of low loading force and high welding speeds. It is revealed that tool destruction occurs tangentially to the surface of the tool grooves due to the high tool load and high welding speeds.
28
Li, Yong Le, Jiang Feng Wang, Qian Wang, and Kun Yang. "Numerical Analysis on Interaction of Superstructure-Piled Raft Foundation-Foundation Soil." Advanced Materials Research 261-263 (May 2011): 1578–83. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1578.
Повний текст джерелаАнотація:
based on the finite element method of superstructure-the pile raft foundation-the foundation soil action and interaction are studied. Research shows that the common function is considered, fundamental overall settlement and differential settlement with the increase of floor of a nonlinear trend. The influence of superstructure form is bigger for raft stress, the upper structure existing in secondary stress, and the bending moment and axial force than conventional design method slants big; With the increase of the floors, pile load sharing ratio is reduced gradually,but soil load sharing ratio is increased. Along with the increase of the upper structure stiffness, the load focused on corner and side pile; Increasing thickness of raft, can reduce the certain differential settlement and foundation average settlement, thus reducing the upper structure of secondary stress and improving of foundation soil load sharing ratio, at the same time the distribution of counterforce on the pile head is more uneven under raft, thus requiring more uneven from raft stress, considering the piles under raft and the stress of soils to comprehensive determines a reasonable raft thickness, which makes the design safety economy. As the foundation soil modulus of deformation of foundation soil improvement, sharing the upper loads increases, counterforce on the pile head incline to average, raft maximum bending moment decrease gradually.
29
I., Lobaev, Pleshakov V., Dzhugan V., Malko V., and Nazarov S. "FIRE INVESTIGATION ACTIVITY MODEL BASED ON A SCENARIO APPROACH." Fire and emergencies: prevention, elimination 4 (2021): 5–14. http://dx.doi.org/10.25257/fe.2021.4.5-14.
Повний текст джерелаАнотація:
Purpose. Fire investigation is one of the main functions of EMERCOM of Russia. The analysis of activity results of Federal Fire Service forensic institutions based on the current model shows that the point of fire origin is not identified with sufficient accuracy in 63 % of cases, and the fire cause is not unambiguously identified in 74 % of cases. This situation makes it impossible to create an incident information model, to establish cause-and-effect relationships between the phenomena and conditions at a fire scene and also to give the correct legal qualification of the incident. The purpose of the study is to improve the efficiency and effectiveness of fire investigation activities. Methods. The study is based on the theory of system analysis, the theory of functions and the theory of risks. The authors use methods of mathematical modeling and information synthesis, instrumental methods for their support, methods of informatics, expert analysis and combinatorics. Findings. A scenario approach to organize fire investigation activities is proposed. It allows effectively identifying the circumstances of fire occurrence, fire development and negative fire consequences. The problems of the proposed approach are the need to develop a reasonable list of scenarios to be investigated under conditions of information uncertainty and the labour-consuming nature of scenario research, which requires the availability of software and powerful computers. Research application field. The use of the proposed approach will improve the accuracy of determining a fire scenario with severe thermal damage to building structures and interior items caused by fire heat as well as with uneven distribution of fire load in the compartment with the ignition source, taking into account the specific gas exchange in the compartment during a fire and other parameters. Conclusions. The proposed activity model based on the scenario approach, which includes the physical evidence investigation at a fire scene and the results of mathematical modeling of the dynamics of hazardous fire factors, enables to determine the point of fire origin and the cause of the fire and also to establish cause-and-effect relationships between the fire and negative fire consequences with sufficient accuracy.
30
Diatlov, Ilia, and Natalia Trufanova. "POWER CABLE INSULATION PRODUCTION LINE CONTROL." Applied Mathematics and Control Sciences, no. 3 (November 10, 2021): 81–94. http://dx.doi.org/10.15593/2499-9873/2021.3.04.
Повний текст джерелаАнотація:
The paper considers the problem of control the cable insulation continuous vulcanization line. The axisymmetric mathematical model of the power cable rubber insulation vulcanization technological process has been developed. The model describes the heat transfer process inside the vulcanization pipe and the vulcanization process kinetics inside the insulation. The mathematical model is based on the energy conservation equation and it is presented in the form of a differential equations system closed by boundary conditions The mathematical model makes it possible to estimate the influence of various technological and design parameters on the temperature distribution along the radius and length of the cable. Based on the temperature distribution curves, the cable insulation vulcanization degree is calculated The study of the raw rubber compositions vulcanization properties was carried out by rotary rheometer, where the samples of the material were subjected to an oscillating load at different temperatures. As a result of the experiment, the curves family of the torque dependence on the curing time at different temperatures was obtained. To describe the vulcanization process kinetics, a parametric expression is used based on the experimentally obtained torque dependences. The obtained temperature dependence of the parametric expression coefficients makes it possible to describe the vulcanization process taking into account the uneven temperature distribution along the cable radius and length. The developed model makes it possible to calculate the speed at which the vulcanization degree reaches a given value. Algorithms for calculating and correcting line speed and extruder flow rate are proposed on the basis of a mathematical model. It allows us to determine the speed and flow rate of the extruder for various: cable designs, insulation materials, abnormal operating conditions of the production line. The results can be used at enterprises engaged in the production of cable and wire products with cross linked insulation. In cases where it is required to quickly calculate a new technological mode, make changes to the cable design, change the insulation material, and also take into account possible pressure drops inside the vulcanization pipe and deviations in the cable properties during the production process.
31
Shprekher, Dmitry, Gennady Babokin, Evgeny Kolesnikov, and Dmitry Ovsyannikov. "Research of Load Unbalance of a Two- Motor Variable Frequency Dtive for Scraper Conveyor." Известия высших учебных заведений. Электромеханика 64, no. 4-5 (2021): 37–45. http://dx.doi.org/10.17213/0136-3360-2021-4-5-37-45.
Повний текст джерелаАнотація:
The article analyzes the uneven loading of the scraper conveyor electric motors. The most common type of multi-motor conveyor is considered here: two-drive, with head and end drives connected through gearboxes and sprockets by an endless chain with scrapers. The simulation results are presented for three variants of com-binations of parameters of electric drives. It has been established that the use of a two-motor variable frequen-cy drive of a scraper conveyor powered by a single frequency converter inevitably entails uneven loading of the electric motors of the head and end drives. To eliminate this disadvantage, it is proposed to supply each electric motor from its own frequency converter. A system of automatic load balancing is proposed. The implementation and the result of the work of the load balancing system are carried out on a model in the Matlab / Simulink system.
32
Kuzmich, M. A., and A. A. Artsiukh. "Intensification of heat transfer in the zone of the thermosyphon evaporator when changing the boiling surface shape." Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series 67, no. 1 (April 6, 2022): 49–56. http://dx.doi.org/10.29235/1561-8358-2022-67-1-49-56.
Повний текст джерелаАнотація:
In present paper the influence of the boiling surface treatment types of thermosyphon evaporator on the heat transfer coefficient was studied. An experimental setup «Loop thermosyphon with replacing lower part of the evaporator» has been developed and assembled. This feature makes it easy to replace samples with various surface modifications as the lower part of the evaporator. The description of the experimental setup, equipment and research methods is given. Heat transfer coefficients for the samples at various applied thermal loads (from 5 to 200 W) were calculated. In case of flat aluminum plate (boiling surface) concentric grooves and uneven coating of aluminum oxide particles, an increase of the heat transfer coefficient from h1 = 5760 W/(m2·K) to h2 = 28339 W/(m2·K) at the supplied heat flux density q = 250 kW/m2 was observed. The heat transfer coefficient for a sample without concentric grooves, but with an uneven coating of aluminum oxide particles was h3 = 16952 W/(m2·K) at q = 250 kW/m2. Results of the study can be used for further increase of thermosyphon evaporator efficiency.
33
Peng, Duo, and Suo Ping Li. "Uneven Cluster-Routing Protocol of Base on Energy for Wireless Sensor Networks." Applied Mechanics and Materials 687-691 (November 2014): 1823–26. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.1823.
Повний текст джерелаАнотація:
For severe energy constraint problem of wireless sensor networks, a non-uniform energy efficient clustering routing protocol (EUCRP) is proposed based on the analysis of the existing clustering routing protocol the characteristics and shortcomings. In EUCRP, we use a limiting cluster size optimization formation algorithm to produce clusters in descending order of the size of the cluster. Improved multi-hop inter-cluster data forwarding, saving energy cluster head and energy consumption of inter-cluster is balanced. Propose using “watering pot path” in the last hop to effectively solve the “hot zone” problem caused by uneven load energy. Simulation results show that the protocol can effectively reduce network energy consumption and prolong the network lifetime.
34
Stennikov, Valery, Ekaterina Mednikova, and Ivan Postnikov. "Optimization of the district heating zones." MATEC Web of Conferences 212 (2018): 02005. http://dx.doi.org/10.1051/matecconf/201821202005.
Повний текст джерелаАнотація:
A method for determining the optimal action zones of the centralized sources of thermal energy is developed using the calculation of the effective heat supply radius of consumers. The methodology allows to take into account the features of heat supply systems’ functioning, their technical and economic indicators, the uneven distribution of heat loads throughout the city, and limitations on the reliability of the system. Practical implementation of the proposed methodology on the scheme of operating a heat supply system is presented, the results of calculating the effective heat supply radius with their subsequent correction for reliability requirements are obtained. The application of this technique in the development of heat supply schemes for cities will allow to determine the boundaries of effective heat supply radii in all directions of the mains of heat networks, taking into account the optimal flow distribution of the coolant in them and the sections’ technical characteristics.
35
Xie, Jinli, and Yinghong Qin. "Heat Transfer and Bearing Characteristics of Energy Piles: Review." Energies 14, no. 20 (October 10, 2021): 6483. http://dx.doi.org/10.3390/en14206483.
Повний текст джерелаАнотація:
Energy piles, combined ground source heat pumps (GSHP) with the traditional pile foundation, have the advantages of high heat transfer efficiency, less space occupation and low cost. This paper summarizes the latest research on the heat transfer and bearing capacity of energy piles. It is found that S-shaped tubes have the largest heat transfer area and the best heat transfer efficiency; that energy piles need to be designed conservatively, such as adjusting the safety coefficient, number and spacing of the piles according to the additional temperature loads; and that unbalanced surface temperature has not been resolved, caused by uneven refrigeration/heating demand in one cycle. A composite energy pile applied to water-rich areas is proposed to overcome the decay of bearing and heat transfer performance. Besides, most of the heat transfer models are borehole-oriented and will fit for energy piles effectively if the models support variable ground temperature boundary conditions.
36
Veerabadrappa, Veerabadrappa, and Booma Poolan Marikannan. "Lifetime centric load balancing mechanism in wireless sensor network based IoT environment." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 5 (October 1, 2021): 4183. http://dx.doi.org/10.11591/ijece.v11i5.pp4183-4193.
Повний текст джерелаАнотація:
Wireless sensor network (WSN) is a vital form of the underlying technology of the internet of things (IoT); WSN comprises several energy-constrained sensor nodes to monitor various physical parameters. Moreover, due to the energy constraint, load balancing plays a vital role considering the wireless sensor network as battery power. Although several clustering algorithms have been proposed for providing energy efficiency, there are chances of uneven load balancing and this causes the reduction in network lifetime as there exists inequality within the network. These scenarios occur due to the short lifetime of the cluster head. These cluster head (CH) are prime responsible for all the activity as it is also responsible for intra-cluster and inter-cluster communications. In this research work, a mechanism named lifetime centric load balancing mechanism (LCLBM) is developed that focuses on CH-selection, network design, and optimal CH distribution. Furthermore, under LCLBM, assistant cluster head (ACH) for balancing the load is developed. LCLBM is evaluated by considering the important metrics, such as energy consumption, communication overhead, number of failed nodes, and one-way delay. Further, evaluation is carried out by comparing with ES-Leach method, through the comparative analysis it is observed that the proposed model outperforms the existing model.
37
Tomilov, Valeriy Viktorovich, Sandugash Myrzabekovna Utepbergenova, and Oleg Alexeevich Sidorov. "Pantograph cooling system mathematical model during motion of the railway electric transport." Transport of the Urals, no. 2 (2020): 86–92. http://dx.doi.org/10.20291/1815-9400-2020-2-86-92.
Повний текст джерелаАнотація:
Uneven heating of the pantograph slide is the reason for limiting the pantograph removal of the maximum permissible long-term current from the contact network. The highest heating point is observed in the center of the pantograph head relative to the path axis, which can be taken into account when developing a pantograph slide cooling device. Existing models of the thermal state of the pantograph slide do not describe the transient modes of distributed heating of a closed-type structure (euro pantograph head) as a result of the impact of a contact wire in the plan when moving a rolling stock. Existing methods for calculating the heating of the pantograph slide require the use of special programs for the development of its three-dimensional model and significant power of electronic computers. The paper presents a mathematical model euro pantograph head standard design and are equipped with passive cooling system the center through the frame device of the confuser type, which can calculate the load characteristics of the pantograph slide, to evaluate the reduction of uneven heating of its design and to determine the maximal permissible continuous current of the pantograph.
38
Li, Chuang, Yan Wei Liu, Na Fu, and Rui Tao Fang. "Underground Runoff Product Flow of Red Loam under Rainfall Simulation." Applied Mechanics and Materials 737 (March 2015): 766–70. http://dx.doi.org/10.4028/www.scientific.net/amm.737.766.
Повний текст джерелаАнотація:
The red loam had abundant rainfall, rich in light and heat resource of Yunnan Province. But the uneven distribution of rainfall temporal during the year, it restricts the development of agriculture in this region. Thus how to use soil water resources reasonably and efficiency become the key to ensure crop and vegetation growth of needed water and improve the ecological environment. In this study, the key factor is district’s slope. Setting the runoff district’s rainfall intensity was 28.7mm/24h under rainfall simulation, selected four Yunnan Province read loam’ slop: 7.5°、10°、12.5°、15°.The results showed that at the same soil prophase water content and rainfall intensity, the higher runoff district’s slope will make it less time to product flow; At the beginning of product flow, flow of underground runoff was little, product flow was reached stable increase.
39
Bytčanková, Lucia, Ján Rumann, and Peter Dušička. "Analyzing the impact of intake structure on the flow at low pressure SHPP." Pollack Periodica 16, no. 1 (March 25, 2021): 114–19. http://dx.doi.org/10.1556/606.2020.00149.
Повний текст джерелаАнотація:
AbstractThe structural parts of intake structures directly affect the flow velocity distribution in the turbine intake of small hydropower plants, where inhomogeneous flow leads to uneven load of the turbine units causing operational problems. A 2D numerical flow modeling was used for investigations of the flow in an intake structure of a low-head small hydropower plant. The effects of shape changes of the intake structure on the flow velocity distribution in the turbine intakes were investigated and assessed proving significant effect of the shapes of the intake structure on the flow homogeneity in turbine intakes.
40
Parlyuk, E. P., N. N. Pulyaev, and A. V. Kurilenko. "Mathematical efficiency model of the block-module cooling system of automotive vehicles and tractors." IOP Conference Series: Earth and Environmental Science 839, no. 5 (September 1, 2021): 052061. http://dx.doi.org/10.1088/1755-1315/839/5/052061.
Повний текст джерелаАнотація:
Abstract As related to other heat exchange systems, the operation of a heat exchanger should be based on the quality analysis of the heat carrier flows. One of these quality characteristics is the uneven distribution of temperature and air flow velocity ahead of the heat exchanger. To obtain more accurate performance indicators, it is necessary to build mathematical models of thermal processes in the radiator taking into account the unevenness of the air flow. The improvement of cooling systems is one of the priorities for the development of motor vehicles, as the temperature and dynamic loads in the engines are increasing due to the requirements that are becoming more stringent every year. First of all, this relates to environmental friendliness and fuel efficiency parameters, and secondly, it is service maintenance and labor safety, etc. Given this trend, it is necessary to pay attention to such important issues as improving the design of cooling systems, influencing the efficiency of heat balance distribution in the internal combustion engine. When developing new heat exchangers, a thermal engineering design should be analyzed to determine the heat exchange surface area that ensures the transfer of a given amount of heat from one heat carrier to another.
41
Xu, Hua, Yangyang Zhou, Jungang Yin, Ruiqing Zhang, Chao Li, Senlin Wang, and Fuming Yi. "Structural Analysis and Optimization of Steel Pin on Cylindrical Head Suspension Porcelain Insulators." Journal of Physics: Conference Series 2166, no. 1 (January 1, 2022): 012038. http://dx.doi.org/10.1088/1742-6596/2166/1/012038.
Повний текст джерелаАнотація:
Abstract There is no essential difference in theory between the inner and outer insulating properties of cylindrical and conical head disc suspension porcelain insulators. Compared with a conical head porcelain insulator, a cylindrical head porcelain insulator is significantly lighter in weight, which can effectively reduce the mechanical load of the tower and wire; and it has better dispersion and adjustment capabilities for changes in material properties over time, so that the product is not subject to excessive and uneven stress over a long-term. In order to improve the mechanical performance of cylindrical head insulator products, this paper establishes a parameterized fine simulation model of the steel pin without changing the geometry of the insulator iron cap and porcelain body. The finite element method is used to calculate and analyze how the geometric parameters of the steel pin influence insulator mechanical properties, which can provide design reference for further product optimization.
42
Gravois, KA, and RS Helms. "Effect of uneven emergence on rice yield, milling yield, and yield components." Australian Journal of Experimental Agriculture 34, no. 7 (1994): 949. http://dx.doi.org/10.1071/ea9940949.
Повний текст джерелаАнотація:
Establishing a uniform rice (Oryza sativa L.) stand is an important beginning to managing a rice crop and attaining high yields. Most rice management practices in the United States are timed according to rice growth stages. Non-uniform rice stands, and subsequently non-uniform growth stages, present problems for the timely application of management practices for attaining high yields. Our objective was the determination of the effects of uneven emergence on rice yield, milling yield, and yield components. Experiments were conducted in 1988 and 1989 on a Hebert silt loam (Vertic Hapludoll) at the Southeast Branch Experiment Station near Rohwer, Arkansas. Uneven emergence was simulated by delayed (18 days from emergence) interseeding of rice to achieve 0, 20, 40, 60, and 80% uneven emergence. Each experiment was planted with the cultivars Lemont (semi-dwarf) and Tebonnet (tall) and was replicated 4 times. Rice yields for the uneven emergence treatment levels were significantly less than the rice yields seeded exclusively at PD1 (planting date 1), except for the uneven emergence levels 80-20 (80% planted at PD1 and 20% planted at PD2) and 60-40 for Tebonnet, and 60-40 in 1988 for Lemont. In 1989, there was a trend for head rice yields to decrease as uneven emergence levels increased. Average panicle density and number of grains per panicle for both Lemont and Tebonnet decreased with increasing uneven emergence, indicating a failure in the typical compensatory relationship between panicle density and grain per panicle. Lemont exhibited reduced average grain weights due to uneven emergence, especially at 80-20, 60-40, and 40-60 uneven emergence levels. Harvest indices were higher for PD1 than for PD2, except at 20-80 uneven emergence level. Essentially, the later emerging rice from the second planting acted much like a weed by competing against rather than contributing to rice yields. Late interseeding to enhance poor rice stands is unlikely to produce an economic return that could be expected from an adequate initial plant stand.
43
Svoboda, Martin, Milan Chalupa, Karel Jelen, František Lopot, Petr Kubový, Milan Sapieta, Zdeněk Krobot, and Marcin Suszyński. "Load Measurement of the Cervical Vertebra C7 and the Head of Passengers of a Car While Driving across Uneven Terrain." Sensors 21, no. 11 (June 2, 2021): 3849. http://dx.doi.org/10.3390/s21113849.
Повний текст джерелаАнотація:
The article deals with the measurement of dynamic effects that are transmitted to the driver (passenger) when driving in a car over obstacles. The measurements were performed in a real environment on a defined track at different driving speeds and different distributions of obstacles on the road. The reaction of the human organism, respectively the load of the cervical vertebrae and the heads of the driver and passenger, was measured. Experimental measurements were performed for different variants of driving conditions on a 28-year-old and healthy man. The measurement’s main objective was to determine the acceleration values of the seats in the vehicle in the vertical movement of parts of the vehicle cabin and to determine the dynamic effects that are transmitted to the driver and passenger in a car when driving over obstacles. The measurements were performed in a real environment on a defined track at various driving speeds and diverse distributions of obstacles on the road. The acceleration values on the vehicle’s axles and the structure of the driver’s and front passenger’s seats, under the buttocks, at the top of the head (Vertex Parietal Bone) and the C7 cervical vertebra (Vertebra Cervicales), were measured. The result of the experiment was to determine the maximum magnitudes of acceleration in the vertical direction on the body of the driver and the passenger of the vehicle when passing a passenger vehicle over obstacles. The analysis of the experiment’s results is the basis for determining the future direction of the research.
44
Ismatov, Jumaniyoz, and Obidjon Ergashev. "Processes of mixture formation, ignition and combustion of a diesel engine." E3S Web of Conferences 264 (2021): 04062. http://dx.doi.org/10.1051/e3sconf/202126404062.
Повний текст джерелаАнотація:
One of the most significant concepts of deep restructuring of the economic mechanism of the Republic of Uzbekistan is the creation of an integral, effective and flexible system of economic management and the implementation on this basis of a program to improve the technical level and quality of machines. The car park of our country is more replenished with vehicles with diesel engines. The development of contemporary diesel engine building is proceeding by forcing engines: increasing the average effective pressure and speed. Therefore, high reliability and service life, fuel efficiency and environmental performance are the basic criteria for their quality. Forcing diesel engines leads to an increase in thermal and mechanical loads on the basic parts of the cylinder-piston group (CPG) (piston, liner and cylinder head), a significant increase in their temperature, as well as the temperature of piston rings and valves. Overheating of parts is accompanied by the formation of temperature fields with a pronounced uneven temperature distribution and, as a result, an increase in thermal stresses with a simultaneous deterioration of the mechanical properties of the material, the formation of cracks and, finally, the destruction of the part. In this regard, the task of protecting parts from excessive exposure to high thermal loads from the working fluid becomes urgent, or, in other words, the task of creating a diesel engine with reduced heat removal from the working fluid.
45
Zhang, Hong Ming, and Li Xiang Zhang. "Numerical Investigation of Cavitating Turbulent Flow in a Francis Turbine Runner Fitted with Splitter Blades." Advanced Materials Research 662 (February 2013): 637–42. http://dx.doi.org/10.4028/www.scientific.net/amr.662.637.
Повний текст джерелаАнотація:
The paper presents numerical investigation of cavitating turbulent flow in a high head Francis turbine runner fitted with splitter blades at part load operation. Analysis was performed by OpenFOAM code. A mixture assumption and a finite rate mass transfer model were introduced. The finite volume method is used to solve the governing equations of the mixture model and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results show that the volume fraction of water vapor and the pressure uneven distribution on the main blade and splitter blade. It will lead to cavitation and fatigue damage.
46
Yang, Jun, Chang Yu, and Zijian Hu. "Improvement of Perception Layer Routing Protocol with Static Nodes in IoT-Based Microgrids." Processes 9, no. 11 (October 22, 2021): 1882. http://dx.doi.org/10.3390/pr9111882.
Повний текст джерелаАнотація:
Aiming at the problem of uneven clustering and the unreasonable energy consumption of LEACH protocol in the perception layer of IoT-based microgrids of static nodes; in this paper, we propose a stationary-node energy-based routing protocol (SERP). First, we select a dynamic cluster radius for clustering to meet the actual needs of the network during clustering. Then, to solve the problem that the number of cluster heads is difficult to determine, a dynamic optimal cluster head ratio is adopted. The dynamic optimal cluster head ratio can be obtained by minimizing the total energy consumption of cluster formation and the stable transmission phase, which can improve the efficiency of network transmission. Finally, by setting the residual energy factor and distance factor to improve the calculation of the cluster head election threshold, the energy load of the network is more uniform, and the location of the cluster head is more reasonable. Compared with the LEACH protocol and the HEED protocol, the simulation results show that the SERP protocol can effectively prolong the lifetime of the whole network.
47
Liang, Yu, Xiangyu Chen, Junsheng Yang, and Linchong Huang. "Risk Analysis and Control Measures for Slurry Shield Tunneling Diagonally under an Urban River Embankment." Advances in Civil Engineering 2020 (November 17, 2020): 1–11. http://dx.doi.org/10.1155/2020/8875800.
Повний текст джерелаАнотація:
The construction of urban cross-river tunnels usually requires passing under river embankments, which inevitably disturbs the embankment substratum and causes ground deformation. Previous engineering cases have shown that embankment settlement is greater than ordinary surface settlement and that uneven settlement results in cracks of in the embankment, reducing the embankment stability. Based on a cross-river tunnel project in China, the construction risks caused by the additional stress on the embankment substratum, asymmetrical embankment load, and shield tunneling in saturated fine sand are analyzed during a large-diameter slurry shield tunneling below an urban river embankment diagonally. Additionally, relevant risk control measures, such as slurry pressure, jacking thrust setting, and driving velocity in the saturated fine sand stratum, are evaluated. The results show that during shield tunneling under a diagonal urban river embankment, the additional stress and asymmetrical load effects should be considered, and the shield slurry pressure and jacking thrust should be adjusted according to the distance between the cutter head and the embankment. Furthermore, based on settlement monitoring data, the driving velocity of the shield should be reasonably adjusted in a timely manner to avoid disturbing the fine sand stratum below the embankment.
48
Varun, Rajesh Kumar, Rakesh C. Gangwar, Omprakash Kaiwartya, and Geetika Aggarwal. "Energy-Efficient Routing Using Fuzzy Neural Network in Wireless Sensor Networks." Wireless Communications and Mobile Computing 2021 (August 3, 2021): 1–13. http://dx.doi.org/10.1155/2021/5113591.
Повний текст джерелаАнотація:
In wireless sensor networks, energy is a precious resource that should be utilized wisely to improve its life. Uneven distribution of load over sensor devices is also the reason for the depletion of energy that can cause interruptions in network operations as well. For the next generation’s ubiquitous sensor networks, a single artificial intelligence methodology is not able to resolve the issue of energy and load. Therefore, this paper proposes an energy-efficient routing using a fuzzy neural network (ERFN) to minimize the energy consumption while fairly equalizing energy consumption among sensors thus as to prolong the lifetime of the WSN. The algorithm utilizes fuzzy logic and neural network concepts for the intelligent selection of cluster head (CH) that will precisely consume equal energy of the sensors. In this work, fuzzy rules, sets, and membership functions are developed to make decisions regarding next-hop selection based on the total residual energy, link quality, and forward progress towards the sink. The developed algorithm ERFN proofs its efficiency as compared to the state-of-the-art algorithms concerning the number of alive nodes, percentage of dead nodes, average energy decay, and standard deviation of residual energy.
49
Mizin, V. V., O. A. Isakov, M. A. Voitenko, and V. P. Lyashenko. "Interrelation between psychophysiological indices and autonomic adaptive response youth information overload." Ecology and Noospherology 25, no. 3-4 (May 20, 2014): 99–106. http://dx.doi.org/10.15421/031425.
Повний текст джерелаАнотація:
Nowaday humanity lives in a super information world, which is marked by an increase in volume of auditory and visual information, the acceleration of change in the objective and the spirit world, increase information load in the form of electromagnetic waves caused by man. This can lead to information overload, the essence of which is that the amount of useful information coming exceed the objective possibilities of perception. The singular group, which is over loaded by information – the students. The aim of the presented work was to identify the relationship between psychophysiological indices and vegetative adaptive responses of the students from the Dnepropetrovsk National University of Oles Gonchar on information overload, which may form the basis for the formation of curricula and educational work in high school and would like to offer some prognostic model of the functional state of the students in today's environment. The study involved 120 students volunteer 2–3 courses of natural specialties Dnepropetrovsk National University of Oles Gonchar. To determine the physiological features and functional state of the students the program «Psychodiagnostics» was used. For registration of heart rate variability a heart rate monitor POLAR RS800CX was used. Testing was conducted before and after the information load. Information load carried by means of tests Schulte, Bourdon and Gorbova granted in computerized form. In boys enrolled in natural specialties found high rates of properties of neural processes. Under the influence of information load indicator latent period of reaction time choosing two out of three was significantly decreased by 15 % and the rate of functional mobility of nervous processes that characterize the strength of nervous processes significantly decreased by 17 %. Mobility and balance the nervous processes when information load decreased. These changes in performance can indicate the presence of an imbalance of the autonomic nervous system stress due to information load. Resulting in uneven tasks and the lack of a clear rhythm work. Under the influence of information load significantly increased capacity is very high-frequency range (VLF, ms2) and total power (Total, ms2). Exceeding the indicator VLF, may indicate an increased influence of humoral-metabolic mechanisms regulating heart rate. There is a tendency to increase of high-capacity and low-frequency spectra, and reduce the percentage of very low-frequency (HF) range. Also, the rate of vago-sympathetic tone (LF/HF) 2 times higher than normal, which may indicate the presence sympathicotonia. Indicators spectral analysis of heart rate variability was significantly increased, the rate of the average standard deviation (SDNN) increased by 23 % and the prevalence rate of parasympathetic regulation of sympathetic link link (pNN50) by 37 %. These changes indicate activation of the sympathetic division of the autonomic nervous system and low adaptive capacities of the autonomic nervous system. Our investigations have shown that young natural specialties of Dnepropetrovsk National University of Oles Gonchar are influenced by information load significantly deteriorated physiological parameters and heart rate variability. Infringement of autonomic adaptive responses leads to a decline in physical and mental performance of boys.
50
Szymanski, Pawel, Richard Law, Ryan MᶜGlen, and David Reay. "Recent Advances in Loop Heat Pipes with Flat Evaporator." Entropy 23, no. 11 (October 20, 2021): 1374. http://dx.doi.org/10.3390/e23111374.
Повний текст джерелаАнотація:
The focus of this review is to present the current advances in Loop Heat Pipes (LHP) with flat evaporators, which address the current challenges to the wide implementation of the technology. A recent advance in LHP is the design of flat-shaped evaporators, which is better suited to the geometry of discretely mounted electronics components (microprocessors) and therefore negate the need for an additional transfer surface (saddle) between component and evaporator. However, various challenges exist in the implementation of flat-evaporator, including (1) deformation of the evaporator due to high internal pressure and uneven stress distribution in the non-circular casing; (2) heat leak from evaporator heating zone and sidewall into the compensation chamber; (3) poor performance at start-up; (4) reverse flow through the wick; or (5) difficulties in sealing, and hence frequent leakage. This paper presents and reviews state-of-the-art LHP technologies; this includes an (a) review of novel manufacturing methods; (b) LHP evaporator designs; (c) working fluids; and (d) construction materials. The work presents solutions that are used to develop or improve the LHP construction, overall thermal performance, heat transfer distance, start-up time (especially at low heat loads), manufacturing cost, weight, possibilities of miniaturization and how they affect the solution on the above-presented problems and challenges in flat shape LHP development to take advantage in the passive cooling systems for electronic devices in multiple applications.