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1
Alhawari, Abdalhadi, and Phalguni Mukhopadhyaya. "Construction and Calibration of a Unique Hot Box Apparatus." Energies 15, no. 13 (June 26, 2022): 4677. http://dx.doi.org/10.3390/en15134677.
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A variety of mathematical models are available to estimate the thermal performance of buildings. Nevertheless, mathematical models predict the thermal performance of buildings that might differ from the actual performance. The hot box is a widely-used test apparatus to assess the actual thermal performance of various building envelope components (walls, roofs, windows) in the laboratory. This paper presents the process of designing, constructing, and calibrating a unique small-scale hot box apparatus. Despite its smaller metering area (1.0 m × 1.0 m), this apparatus met the key requirements (below ±0.25 °C fluctuations in chambers’ air temperature, and below 2.0% variation from the point-to-point temperature in reference to the temperature difference across the specimen) as prescribed in the ASTM C1363 and ISO 8990 standards. The walls of this apparatus are uniquely constructed using vacuum insulation panels or VIPs. The efficient and novel use of VIPs and workmanship during the construction of the apparatus are demonstrated through the temperature stability within the chambers. The achieved range of temperature steadiness below ±0.05 °C and point-to-point temperature variation below 1.0% of the temperature difference across the specimen allow for this apparatus to be considered unique among the calibrated hot box categories reported in the literature. In addition, having an affordable, simple-to-operate, and high-accuracy facility offers a great opportunity for researchers and practitioners to investigate new ideas and solutions. The apparatus was calibrated using two extruded polystyrene foam (XPS) specimens with thicknesses of 2″ and 4″. The calibration exercise indicates small differences between results obtained numerically, theoretically, and experimentally (below 3.0%). Ultimately, the apparatus was employed to measure the thermal properties of a specimen representing a lightweight steel framing (LSF) wall system, which is commonly used in cold climates. The results obtained experimentally were then compared to the ones estimated numerically using a 3D finite element modelling tool. The difference between the results obtained by both methods was below 9.0%.
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Gorshenin, S. D., S. I. Shuvalov, E. V. Zinovieva, and l. A. Kokulin. "Improving the efficiency of fly ash reinjection in grate stoker of boiler." Vestnik IGEU, no. 5 (October 31, 2022): 18–23. http://dx.doi.org/10.17588/2072-2672.2022.5.018-023.
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A significant disadvantage of grate stokers is great carbon loss. To reduce these losses, the ash caught in the flue is returned to the furnace for afterburning. The effectiveness of this measure depends on the thermal characteristics of coal, the size of the pieces of coal and ash, the degree of carbon elimination, and the design features of the combustion chamber. Normative techniques to calculate and design grate stokers do not consider the features of coal combustion with ash return. Thus, it is relevant to develop the models that describe the creation of ash flows in the boiler path depending on its design, properties and dispersed composition of the burned coal and the aerodynamics of the combustion chamber. Mathematic simulation of the processes of particle size classification has been carried out to describe the creation of ash mass flows on the grate and in the convection chamber. To evaluate the parameters of mathematical models, simulation modeling of gas dynamics of flue gases in the combustion chamber has been carried out with SolidWorks software. The authors have developed a mathematical model and the method to identify its parameters. It allows us to obtain quantitative estimates of the economic efficiency of boilers with grate firing of coal. Thus, a computer program has been developed. The authors have used the program and the Neryungri brown coal to burn in the KV-TS-30-150 boiler. The results have shown that carbon loss without fly ash reinjection is 11,27 %. Introduction of fly-coke return unit reduces the loss up to 10,45 %. It is established that elimination of slit windows in the rotary baffle will lead to a change of the trajectories of ash particles and carbon losses reduction up to 10,17 %. Limiting the maximum size of coal pieces to 50 mm will lead to a more noticeable increase of boiler efficiency. The calculations have showed that in case the value of the carbon burn out factor equals 0,935, the carbon loss when the system of fly ash reinjection is turned off, its commissioning and, in addition, an increase of the gas density of the rotary screen will be 4 ,88%, 4,44% and 4,3% respectively. In case of a more careful assessment of the burnout factor at the level of 0,9, the carbon loss will be 7,51%, 6,87% and 6,65% respectively. The developed mathematical model makes it possible to evaluate the effect of the operation of the fly ash reinjection unit on the efficiency of the operation of a boiler with a grate stoker. Validation of a model for adequacy and for accuracy increase can be carried out after field testing of the boiler equipment.
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Stanmore, Brian R. "Examination of PCDD/F Formation in Thermal Systems Using Simple Mathematical Models." Advances in Environmental and Engineering Research 02, no. 02 (March 1, 2021): 1. http://dx.doi.org/10.21926/aeer.2102013.
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A set of empirical models which accounts for the formation of gas phase polychlorinated dibenzo-p-dioxins and furans (PCDD and PCDF), and solid phase PCDD/F by the de novo mechanism is described.In each case, competing formation and destruction reactions are considered to operate.The effect of the time-temperature history on their formation is then examined.At high temperatures, steady-state is reached in fractions of a second, resulting in the observed low product concentrations.Rapid cooling as found in furnaces produces higher PCDD/F nett formation rates than slower cooling over the same temperature range, but with less overall yield.In addition, a cooling process will result in more PCDD/F production than heating at the same rate. Thus the conventionally-regarded temperature “windows” for formation are misleading, as in practical conditions PCDD/F are produced at higher temperatures.Simulations carried out of a pilot scale municipal solid waste (MSW)incinerator, a commercial fluidised bed boiler burning wood as a fuel, and of the laboratory scale thermal “annealing” of particulates taken from iron ore sintering off-gases illustrate the effects.There is sufficient promise in the approach to suggest that better characterisation of particulates will lead to acceptable predictions.
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Sharo, Abdulla A., Samer R. Rabab’ah, Mohammad O. Taamneh, Hussein Aldeeky, and Haneen Al Akhrass. "Mathematical Modelling for Predicting Thermal Properties of Selected Limestone." Buildings 12, no. 12 (November 24, 2022): 2063. http://dx.doi.org/10.3390/buildings12122063.
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Due to a lack of geotechnical and geothermal studies on Jordanian limestone, this paper aims to provide the thermal properties, including thermal conductivity, thermal diffusivity, and specific heat, using the Hot Disk Transient Plane Source (TPS) 2200 method. It also aims to provide a set of mathematical models through which the thermal properties can be indirectly predicted from the rocks’ physical and engineering properties. One hundred cylindrical rock specimens with a height of 20 cm and a diameter of 10 cm were extracted and prepared. The results showed that the thermal conductivity values ranged between (1.931–3.468) (W/(m*k)), thermal diffusivity (1.032–1.81) (mm2/s), and specific heat (1.57–2.563) ((MJ)/(m3*K)). The results also suggest a direct relationship between conductivity and diffusivity and an inverse relationship between conductivity and specific heat. On the other hand, the results indicate the direct relationship between the conductivity and diffusivity, and the inverse relationship between the specific heat and density, hardness, sound velocity, and rock strength; the opposite happens when the rock’s porosity is considered. Simple regression, multivariate regression, and the backpropagation–artificial neural network (BP–ANN) approach were utilized to predict the thermal properties of limestone. Results indicated that the ANN model provided superior prediction performance compared to other models.
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Habib, Khairul, Mohammed Ahmed, Ahmed Qays Abdullah, Omer A. Alawi, Balaji Bakthavatchalam, and Omar A. Hussein. "Metallic Oxides for Innovative Refrigerant Thermo-Physical Properties: Mathematical Models." Tikrit Journal of Engineering Sciences 29, no. 1 (November 15, 2021): 1–15. http://dx.doi.org/10.25130/tjes.29.1.1.
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Nano-refrigerant is announced to become an excellent refrigerant, which often improves heat transfer efficiency in the cooling systems. Different materials can be applied to be suspended in traditional coolants in the same way as nanoparticles. In this comprehensive research, mathematical modeling was used to investigate the effect of suspended nanoparticles (Al2O3, CuO, SiO2 and ZnO) on 1,1,1,2-Tetrafluoroethane, R-134a. The thermal conductivity, dynamic viscosity, density and specific heat capacity of the nano-refrigerant in an evaporator pipe were investigated. Compared to conventional refrigerants, the maximum increase in thermal conductivity was achieved by Al2O3/R-134a (96.23%) at a volume concentration of 0.04. At the same time, all nano-refrigerant types presented the same viscosity enhancement of(45.89%) at the same conditions. These types of complex thermophysical properties have enhanced the heat transfer tendencies in the pipe. Finally, the nano-refrigerant could be a likely working fluid generally used in the cooling unit to improve high-temperature transfer characteristics and save energy use.
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Gavrilovski, Dragica, Nikola Blagojevic, and Milorad Gavrilovski. "Modeling glass-ceramic enamel properties." Journal of the Serbian Chemical Society 67, no. 2 (2002): 135–42. http://dx.doi.org/10.2298/jsc0202135g.
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The results of an investigation of the chemical and thermal characteristics of glass-ceramic enamels, derived from the Li2O-Na2O-Al2O3-TiO2-SiO2 system obtained by employing the methods of mathematical experiment planning, are presented in this paper. Adequate mathematical models, showing the dependence of the chemical and thermal stability on the chemical composition of enamel systems, after different thermal treatment procedures, were obtained. Based on the testing carried out, it was concluded that in the obtained glass-ceramic enamels the chemical resistance is decreased, but at the same time, the thermal stability is increased, relative to reference coatings.
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Kozlov, A. A., N. S. Klimova, A. M. Smirnov, N. S. Chekmarev, and M. D. Shabala. "MATHEMATICAL MODELS OF OPERATING PROPERTIES OF THERMAL RESISTANT DUAL PURPOSE ARAMID MATERIALS." Вестник Санкт-Петербургского государственного университета технологии и дизайна. Серия 4: Промышленные технологии, no. 1 (2021): 115–23. http://dx.doi.org/10.46418/2619-0729_2021_1_13.
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Misiopecki, Cezary, Robert Hart, Arild Gustavsen, and Bjørn Petter Jelle. "Operating Hardware Impact on the Heat Transfer Properties of Windows." Energies 14, no. 4 (February 21, 2021): 1145. http://dx.doi.org/10.3390/en14041145.
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Despite significant advancements in fenestration technology in the last two decades, the thermal transmittance of fenestration products is still significantly higher than that of walls. This corresponds to 60% of the total energy loss of a modern building envelope through the windows. Hence, further development and improvements of fenestration products are necessary. Increasingly stringent codes and standards for fenestration stimulate industry to work on improved solutions. Thus, it is crucial that assessment techniques are able to account for innovations accurately. The thermal effects of non-continuous hardware in window frames are currently ignored by international rating procedures. A preliminary investigation conducted by our team showed significant performance degradation in two of the three out-opening casement profiles caused by the presence of operating hardware. Frames with the structure made of vinyl and fiberglass consist of many air cavities that are penetrated by operating hardware made of highly conductive materials. In these frames, in order to have an accurate assessment, it may be required to employ three-dimensional modeling due to the convective nature of heat transfer within the cavities. However, in this study, we demonstrate that the three-dimensional (3D) effects of non-continuous hardware can be approximated accurately with simpler two-dimensional (2D) simulations. We then develop a simplified model based on weighted average capable of replacing the time- and computation-intensive 3D simulations with 2D simulations and validate it against market available frames and their corresponding hardware. Validation results show that our approximation technique results in discrepancies lower than 0.05 W/(m2K), or 3% of the total thermal transmittance. Thus, we conclude that simplified 2D simulation models may be used for predicting hardware impact in window frames with reasonable accuracy. As windows and glazing structures are becoming ever better thermally insulated, it is becoming even more important to be able to model the impact of the operating hardware on the total thermal performance in order to design the best windows possible and not let the operating hardware ruin an otherwise well-proven design, which is hence addressed in this study.
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Grazzini, G., C. Balocco, and U. Lucia. "Measuring thermal properties with the parallel wire method: a comparison of mathematical models." International Journal of Heat and Mass Transfer 39, no. 10 (July 1996): 2009–13. http://dx.doi.org/10.1016/0017-9310(95)00311-8.
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Rastgou, Mostafa, Hossein Bayat, and Muharram Mansoorizadeh. "Fitting soil particle-size distribution (PSD) models by PSD curve fitting software." Polish Journal of Soil Science 52, no. 2 (November 21, 2019): 211. http://dx.doi.org/10.17951/pjss.2019.52.2.211.
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This paper describes a particle-size distribution (PSD) curve fitting software for analyzing the soil PSD and soil physical properties. A better characterization of soil texture can be obtained by describing the soil PSD using mathematical models. The mathematical equations of soil PSD are mainly used as a basis to estimate the soil hydraulic properties. Until now, many attempts are made to represent PSD curves using mathematical models, but selecting the best PSD model requires fitting all models to the PSD data, which would be difficult and time-consuming. So far, no specific program has been developed to fit the PSD models to the experimental data. A practical user-friendly software called "PSD Curve Fitting Software" was developed and introduced to program a simultaneous fitting of all models on soil PSD data of all samples. Some of the capabilities of this software are calculating evaluation statistics for all models and soils and their statistical properties such as average, standard deviation, minimum and maximum for all models, the amount of models’ fitting parameters and their statistical properties for all soil samples, soil water retention curve by Arya and Paris (1981) and Meskini-Vishkaee et al. (2014) methods, soil hydraulic conductivity by Arya et al. (1999) method, different textural and hydraulic properties, specific surface area, and other descriptive statistics of PSD for all soil samples. All calculated parameters are presented in an output Excel file format by the software. The software runs under Windows XP/7/8/10.
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Kang, Jun-Gu, Jin-Hee Kim, and Jun-Tae Kim. "Performance Evaluation of DSC Windows for Buildings." International Journal of Photoenergy 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/472086.
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Interest in BIPV systems with dye-sensitized solar cells (DSCs) that can replace building windows has increased for zero energy buildings. Although DSCs have lower efficiency in terms of electricity generation than silicon solar cells, they allow light transmission and application of various colors; they also have low production costs, which make them especially suitable for BIPV systems. DSC research is interdisciplinary, involving electrical, chemical, material, and metal engineering. A considerable amount of research has been conducted on increasing the electrical efficiency of DSC and their modules. However, there has not been sufficient research on building applications of DSC systems. The aim of this study is to evaluate the optical performance and thermal performance of DSC windows in buildings. For this study, DSC experimental models with different thicknesses and dye colors were manufactured, and their optical properties, such as transmittance and reflectivity, were measured by a spectrometer. The thermal and optical characteristics of double-glazed windows with DSC were analyzed with a window performance analysis program, WINDOW 6.0.
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Kuvyrkin, George, Inga Savelyeva, and Daria Kuvshinnikova. "Nonlocal Thermodynamics: Mathematical Model of Two-Dimensional Thermal Conductivity." E3S Web of Conferences 321 (2021): 03005. http://dx.doi.org/10.1051/e3sconf/202132103005.
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Nonlocal models of thermodynamics are becoming more and more popular in the modern world. Such models make it possible to describe materials with a complex structure and unique strength and temperature properties. Models of nonlocal thermodynamics of a continuous medium establish a relationship between micro and macro characteristics of materials. A mathematical model of thermal conductivity in nonlocal media is considered. The model is based on the theory of nonlocal continuum by A.K. Eringen. The interaction of material particles is described using local and nonlocal terms in the law of heat conduction. The nonlocal term describes the effect of decreasing the influence of the surrounding elements of the material structure with increasing distance. The effect of nonlocal influence is described using the standard non-locality function based on the Gaussian distribution. The nonlocality function depends on the distance between the elements of the material structure. The mathematical model of heat conduction in a nonlocal medium consists of an integro-differential heat conduction equation with initial and boundary conditions. A numerical solution to the problem of heat conduction in a nonlocal plate is obtained. The numerical solution of a two-dimensional problem based on the finite element method is described. The influence of nonlocal effects and material parameters on the thermal conductivity in a plate under highintensity surface heating is analyzed. The importance of nonlocal characteristics in modelling the thermodynamic behaviour of materials with a complex structure is demonstrated.
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Kuvyrkin, Georgy, Inga Savelyeva, and Daria Kuvshinnikova. "One mathematical model of thermal conductivity for materials with a granular structure." Thermal Science 23, Suppl. 4 (2019): 1273–80. http://dx.doi.org/10.2298/tsci19s4273k.
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The creation of new materials based on nanotechnology is an important direction of modern materials science development. Materials obtained by using nanotechnology can possess unique physicomechanical and thermophysical properties, al-lowing to use them effectively in structures exposed to high-intensity thermomechanical effects. An important step of the creation and usage of new materials is the construction of mathematical models to describe the behavior of these materials in a wide range of changes in external influences. One of the possible models for describing the process of thermal conductivity in structurally sensitive materials is proposed in this paper. The model is based on the laws of rational thermodynamics of irreversible processes and models of a continuous medium with internal state parameters. A qualitative study of the constructed model is carried out. A difference scheme is constructed in order to find the solution of the non-stationary heat conduction problem with allowance for the spatial non-locality effect. The analysis of the solutions is carried out.
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Drzyzga, Agnieszka. "The latest mathematical and empirical models to calculate the thermal conductivity of the soils." E3S Web of Conferences 323 (2021): 00007. http://dx.doi.org/10.1051/e3sconf/202132300007.
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The paper presents the latest models for calculating the thermal conductivity of soil. Precise determination of this parameter is necessary for the correct and safe location of geoengineering objects, underground infrastructure such as cables or ground heat exchangers. A universal model that is easy to apply and gives the most accurate results has not yet been developed. New models are constantly being developed. The aim of this work is to present the latest models for calculating thermal conductivity, so that knowing the properties of the soil, it is possible to select an appropriate model to calculate its conductivity.
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Kostyleva, Liliya Yu, Oleg V. Loginovskiy, Evgeniya A. Retc, and Igor M. Yachikov. "Possibilities of using mathematical models for thermal nondestructive testing of defects in multilayer bimetallic plates." Bulletin of the South Ural State University. Ser. Computer Technologies, Automatic Control & Radioelectronics 22, no. 1 (January 2022): 53–64. http://dx.doi.org/10.14529/ctcr220104.
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There is an actual task of delamination detection in multilayer bimetallic materials. Various methods of nondestructive testing (NDT) are used to solve it, including the method of transient thermal NDT. This method consists in remote registration, visualization and analysis of thermal (temperature) fields, which depend on thermophysical and geometric characteristics, thermal effect capacity and internal structure features of the object. The internal structure defects cause the appearance of abnormal temperature zones on the object surface. Their analysis allows us to judge the presence of changes in the material as a whole or in individual areas. It is possible to understand whether there is a defect under the anomalous site, and what its parameters are, if there is an adequate mathematical model that theoretically describes the dependence of the measuring results on the properties of the object and the selected technological modes. This model is a significant component of thermal NDT systems. For the same object or process, a certain set of mathematical models can be compiled, differing in the number of factors taken into account, the assumptions made, the completeness and accuracy of the description of the state of the object or the conditions of the process. The set of factors is determined by the purpose of the study, and in order to unambiguously determine the model of the thermal state, it is necessary to describe the characteristics of the object (geometric shape and thermophysical characteristics of the material) and the heat exchange process (characteristics of heat sources, initial and boundary conditions). Aim. To analyze the existing mathematical models for the research object – a multilayer bimetallic plate with delaminations between the outer and inner layers, and to identify common approaches to modeling the processes of thermal NDT of multilayer objects. Materials and methods. The structure of the mathematical model of the thermal state of the object is determined. An analytical review of mathematical models of thermal NDT of multilayer objects is performed. Results. The requirements, assumptions and limitations for a mathematical model of thermal NDT of a multilayer bimetallic plate with delamination defects are formulated. Conclusion. On the basis of the considered approaches to the mathematical modeling of the thermal state of multilayer objects with ideal layers contact and delamination defects, the necessary factors for the development of a model for the transient thermal NDT processes of the studied objects are determined.
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Katyal, Puneet, and Punit Kumar. "A simplified approach for thermal elastohydrodynamic lubrication analysis of circular contacts using realistic lubricant properties." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 12 (February 23, 2018): 1618–32. http://dx.doi.org/10.1177/1350650118760613.
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Thermal effect in elastohydrodynamic lubrication has been the subject of extensive research for several decades. The focus of this study was primarily on the development of an efficient numerical scheme to deal with the computational challenges involved in the solution of thermal elastohydrodynamic lubrication model; however, some important aspects related to the accurate description of lubricant properties such as viscosity, rheology, and thermal conductivity in elastohydrodynamic lubrication point contact analysis remain largely neglected. A few studies available in this regard are based upon highly complex mathematical models difficult to formulate and execute. The end-users may not have the specialized skill, knowledge, and time required for the development of computational codes pertaining to these models. Therefore, this paper offers a very simple approach to determine the distribution of mean fluid temperature within an elastohydrodynamic lubrication film. While it is an approximate method, it yields reasonably accurate results with only a little increase in computation time with respect to the isothermal case. Moreover, it can be added as a small module to any existing isothermal algorithm. Using this simplified thermal elastohydrodynamic lubrication model for point contacts, this work sheds some light on the importance of accurate characterization of the lubricant properties and demonstrates that the computed thermal elastohydrodynamic lubrication characteristics are highly sensitive to lubricant properties. It also emphasizes the use of appropriate mathematical models with experimentally determined parameters to account for the correct lubricant behavior.
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Kovács, Róbert. "Mathematical aspects of non-Fourier heat equations." Journal of Computational and Applied Mechanics 17, no. 1 (2022): 1–12. http://dx.doi.org/10.32973/jcam.2022.001.
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Due to technological advancement, as materials with complex structures (e.g., metamaterials and foams) appear in practice there is a need to develop advanced thermal models. These are called non-Fourier equations, and all have particular mathematical properties differing from the conventional attributes of Fourier's law. The present paper discusses the thermodynamic origin of non-Fourier equations and their consequences. The second law of thermodynamics influences the relations among the material parameters, and therefore, it restricts how the temperature-dependent properties can be included in the model. Furthermore, we present the properties of initial and boundary conditions, since these are crucial in solving any practical problems and are different from the usual interpretation used for the Fourier equation.
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Gomez, Ricardo Soares, Antonio Gilson Barbosa de Lima, Túlio Rafael Nascimento Porto, Hortência Luma Fernandes Magalhães, Michelly Dayane Araújo de Almeida, João de Mélo Vieira Neto, and Loredanna Melyssa Costa de Souza. "Thermal Analysis in an Intermittent Kiln with Thermal Insulation: An Experimental Design Approach." Diffusion Foundations 27 (May 2020): 99–112. http://dx.doi.org/10.4028/www.scientific.net/df.27.99.
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The main purpose of this work is to evaluate the influence of the thickness and thermophysical properties of insulating materials on the maximum external surface temperature and energy gain provided for an intermittent ceramic kiln operating with natural gas as fuel. To evaluate the influence of independent variables on response variables, a factorial experimental design was developed. From the analysis of variance (ANOVA), it was possible to determine significant and well-adjusted mathematical models for both response variables. It was verified that the thickness and thermal conductivity of thermal insulation are the independent variables that have the greatest influence on the process efficiency.
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Maldhure, Atul V., and Jayant D. Ekhe. "Effect of modifications of lignin on thermal, structural, and mechanical properties of polypropylene/modified lignin blends." Journal of Thermoplastic Composite Materials 30, no. 5 (October 22, 2015): 625–45. http://dx.doi.org/10.1177/0892705715610402.
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Use of organic biomass, industrial waste lignin, was considered interesting due to its easy availability, polymeric nature, and ample scope to modify with an aim to replace conventional metal oxides to achieve improved properties of the blend when blended with polyolefins. To study the effect of chemical modification of lignin on the thermal, structural, and mechanical properties of polypropylene (PP)/modified lignin blends, purified industrial waste lignin was modified by two different chemical methods and blended in various proportions in PP matrix. The thermal stability of the blends was studied by thermogravimetric analysis, whereas melting and crystallization behavior of blends was studied by non-isothermal differential scanning calorimetry. The results show improved thermal stability of blends with increasing modified lignin proportion in the PP matrix. More depression in melting point was observed in PP/alkylated lignin blends than PP/arylated lignin blends, whereas addition of alkylated lignin shows polymorphism in PP matrix. Intermolecular interactions between blend components have been evaluated by applying several mathematical models to experimental mechanical property data. In most of the cases, good agreement has been obtained between the predictions made by using mathematical models and interpretations done on the basis of experimental data, showing the suitability of these models for predicting the mechanical properties of PP/modified lignin blends.
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Lacki, Piotr, Judyta Różycka, and Marcin Rogoziński. "Analysis of Heat Transfer through PVC Window Profile Reinforced with Ti6Al4V Alloy." Key Engineering Materials 687 (April 2016): 236–42. http://dx.doi.org/10.4028/www.scientific.net/kem.687.236.
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This requires the use of additional reinforcement in order to prevent excessive or permanent deformation of PVC windows. In the paper particular attention was devoted to space located in a corrosive environment exposed to chemical agents. For this purpose, proposed to change the previously used steel profiles reinforcements made of Ti6Al4V titanium alloy corrosion-resistant in the air, at sea and many types of industrial atmosphere. Analysis of the thermal insulation properties of PVC windows with additional reinforcement of profile Ti6Al4V titanium alloy was performed. PVC window set in a layer of thermal insulation was analyzed. Research was conducted using Finite Element Analysis. Numerical models and thermal calculations were made in the program ADINA, assuming appropriate material parameters. The constant internal temperature of 20 ̊ and an outer-20 ̊ was assumed. The course of temperature distribution in baffle in time 24 hours and graphs of characteristic points was obtained. The time of in which followed the steady flow of heat, as well as the course of isotherm of characteristic temperature in the baffle was determined. On the basis of numerical analysis obtained vector distribution of heat flux q [W/m2] and was determined heat transfer coefficients U [W/m2K] for the whole window with titanium reinforcement . All results were compared with the model of PVC windows reinforced with steel profile.
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Apalak, M. Kemal, and M. Didem Demirbas. "Improved Mathematical Models of Thermal Residual Stresses in Functionally Graded Adhesively Bonded Joints: A Critical Review." Reviews of Adhesion and Adhesives 7, no. 4 (December 1, 2019): 367–416. http://dx.doi.org/10.7569/raa.2019.097313.
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Functionally graded material (FGM) concept has been applied successfully in order to improve/design heat transfer, electric and electronic conductivity, static and dynamic strengths of adhesive joints by reliving stress distributions in both adhesive and adherend materials. This new approach relies on tailoring material composition of adhesive and adherends along one or more coordinate directions. Thermal residual stresses in adhesive joints are a vital issue in terms of the joint strength. FGM concept also allows to relieve/control thermal residual stresses encountered in adhesive joints due to mismatches between coefficients of thermal expansion of adhesive and adherend materials. Mathematical models and solutions on the thermal residual stress analysis have been continuously improved. This paper reviews the current status of mathematical models, and offers an improved mathematical model and numerical solution method by considering two-dimensional thermal stress and deformation states of adhesively bonded bi-directional functionally graded clamped plates subjected to an in-plane heat flux along one of the ceramic edges. This mathematical model assumes the material properties of the functionally graded plates to vary with a power law along two in-plane directions and not through the plate thickness direction, in particular, considers the spatial derivatives of thermal and mechanical properties of the material, and enables the investigation of the effects of the bi-directional composition variations and spatial derivative terms on the displacement, strain and stress distributions. The heat conduction and Navier equations describing the twodimensional thermo-elastic problem are discretized using finite-difference method, and the set of linear equations are solved using the pseudo singular value method. The functionally graded plates relieve both stress and strain distributions and levels in the adhesive layer and in the plates even though the adhesive layer is still ungraded. The spatial derivatives of mechanical and thermal properties of the local material become more effective on the strain and stress distributions of the plates and adhesive layer. The model, disregarding these derivative terms, exhibits sensitivity to small changes in the compositional gradients (n, m) by adjusting the variations of ceramic volume fraction along the x - and y-directions, respectively, and instability in the calculation of stress and strain distributions and levels. However, the improved model with material derivatives, which considers the effects of these derivative terms, predicts stress and strain distributions and levels complying with changes in the compositional gradient exponents.
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Belov, Alexander, Dmitry Shaforost, and Viktor Chebotarev. "Mathematical Models for Assessing the Thermal Engineering Reliability of Boiler Units of Power Complexes." Известия высших учебных заведений. Электромеханика 64, no. 6 (2021): 88–93. http://dx.doi.org/10.17213/0136-3360-2021-6-88-93.
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The analysis is carried out and the definitions of the concept of thermal engineering reliability, the determining parameter and the determining function of boiler units, are given. A classification has been developed for the determining parameters of steam and hot water boilers by level in the chain of cause-and-effect relationships in the event of a thermal failure. It is proposed to divide the determining parameters and functions of boilers according to their spatial localization into integral and local. A lot of models for defining functions with different mathematical properties (for example, the presence or absence of discontinuities of the second kind) are considered. The defining functions (reliability criteria) currently used in boiler construction have been identified. The analysis of the safety factors for overturning and stagnation in direct-flow and drum boiler units is carried out. The incorrectness of the currently used dependence is shown. A formula has been proposed for these coefficients using internal useful heads, which is especially relevant for boilers with natural circulation at ultrahigh pressure.
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Velichkin, Vladimir, and Vladimir Zavyalov. "Identification of heat exchangers according to the criterion of energy efficiency." MATEC Web of Conferences 276 (2019): 06022. http://dx.doi.org/10.1051/matecconf/201927606022.
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The article presents the results of the analysis of the characteristics of heat exchangers methods for determining their mathematical models. The necessity of the availability of the mathematical model during the synthesis of automatic control systems with desired properties. The method of identification of the thermal control object by the testing control action is proposed. Since technological control objects always be an energy of interaction the energy efficiency criterion applied for automatic formation of the control action. Also the analytical self-adjusting system with a reference model in the form of an integrating link was applied. From the analytical researches it follows that the movement of the system along the optimal trajectory occurs at a constant speed and does not depend on the properties of the control object, and the optimal control depends on the properties of the control object, time, and technological requirements. It is shown that mathematical models of heat exchangers of the first and second orders are determined quite simply. The accuracy of the mathematical model parameters is limited only by the accuracy of the experimental data. The quality of control systems with desired properties, synthesized by experimental, and accurate models are virtually indistinguishable.
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Susoeva, Irina V., Tatiana N. Vakhnina, Andrey A. Titunin, and Varvara E. Rumyantseva. "Processing Factors and Properties of Thermal Insulation Boards Made of Plant Fillers." Lesnoy Zhurnal (Forestry Journal), no. 4 (July 5, 2022): 185–97. http://dx.doi.org/10.37482/0536-1036-2022-4-185-197.
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Wood processing soft waste is mainly used in the production of fuel briquettes, irrecoverable (non-recyclable) waste from spinning flax and cotton are incinerated or sent to dump. The development of methods for recycling non-recyclable cellulosic waste through the product manufacturing is relevant, both from the resource conservation perspective, as well as the environmental point of view. The issues of plant waste recycling through the manufacturing of various types of products are widely developed in the Russian and foreign scientific research practice. Researchers deal with the processing of wheat, rice straw, bamboo stalks, and other cellulosic materials. There is a plenty of published information on methods of soft wood waste recycling. However, no research on recycling irrecoverable waste of spinning flax and cotton fibers had been carried out before this paper. We propose to produce thermal insulation boards based on phenol-formaldehyde resol binder using flax and cotton spinning waste and soft wood processing waste. The wet production method used here involves mixing the filler with water, a precipitant solution and a binder. After spinning the material is dried. The paper presents the results of determining the physical and mechanical properties and thermal conductivity coefficient of boards made of plant waste. The research was carried out according to the B-plan of the second order. Adequate regression mathematical models of the dependences of physical and mechanical parameters of the boards on the varying factors of the production process were developed according to the experimental data processing results. Using the developed regression models we built the response surfaces of the composite parameters: the bending strength of the boards, the thickness swelling of the boards after 24 h of exposure in water and the thermal conductivity coefficient. Nomograms of the dependencies of board parameters on the values of varying factors have been developed based on the mathematical models analysis. The nomograms are the basis for the development of practical recommendations for determining the rational values of the parameters of insulation board materials production from irrecoverable waste of spinning flax and cotton and soft wood processing waste.
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Aksenov, Ivan, and Aleksandr Konstantinov. "TEMPERATURE DEFORMATIONS OF PVC WINDOW PROFILES WITH REINFORCEMENT." International Journal for Computational Civil and Structural Engineering 18, no. 2 (June 24, 2022): 98–111. http://dx.doi.org/10.22337/2587-9618-2022-18-2-98-111.
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Modern window structures made of PVC profiles can experience significant temperature deformation during both winter and summer operation. This effect is not considered in the current engineering methods of PVC windows calculation, which causes a number of problems in their operation (freezing and blowing through the windows, the failure of fittings, etc.). The use of laboratory methods of testing windows for temperature loads is limited due to their labor intensity and the high cost of testing equipment. We propose to develop an engineering method for calculating the mechanical operation of PVC windows under the action of temperature loads, which can be used at an early stage of design. One of the stages of its creation is a theoretical description of the temperature deformation of a PVC window profile when it works together mechanically with a reinforcing core. The article describes the nature of the forces transmitted by the PVC profile on the core during thermal bending (the case of temperature deformation at negative outside temperatures is considered). It was proposed to decompose these forces into two components: longitudinal, caused by different values of temperature shrinkage of PVC profile and reinforcing core, and transverse, caused by thermal bending of PVC profile. Mathematical models have been developed to calculate both force components and temperature deformation of the profile at different numbers and spacing of attachment points. A physical model has been proposed for implementation in the numerical calculation program, which allows a more accurate description of the temperature deformation of a long profile. Calculation of the test problem according to the proposed methodology and by means of full-fledged three-dimensional finite-element modeling in the COMSOL Multiphysics program was performed. A comparison of the results showed a discrepancy of less than 10%. It was found that the key influence on the deformations of PVC window profiles with a reinforcing core will have characteristics of the outermost joints "PVC profile – reinforcing core", because the greatest forces arise in them under the action of temperature loads.
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Bassyouni, M. "Dynamic mechanical properties and characterization of chemically treated sisal fiber-reinforced polypropylene biocomposites." Journal of Reinforced Plastics and Composites 37, no. 23 (September 7, 2018): 1402–17. http://dx.doi.org/10.1177/0731684418798049.
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The incorporation of sisal fiber as reinforcement materials for polymers will be advantageous if it is synthesized and manufactured perfectly. In this study, surface modification using polymeric diphenylmethane di-isocyanate and gamma-aminopropyltriethoxysilane was applied for further amelioration of polypropylene–sisal bonding. Surface morphology, thermomechanical properties, thermal stability, and chemical bonding were investigated using scanning electron microscopy, dynamic mechanical analysis, thermogravimetric analysis, and Fourier transform infrared spectroscopy, respectively. A number of mathematical models were studied for predicting the effect of untreated and modified sisal fiber loadings on the mechanical properties of biocomposites. Polymeric diphenylmethane di-isocyanate showed a significant improvement on the thermal and mechanical properties of polypropylene biocomposites. Fourier transform infrared spectroscopy analysis of polypropylene–sisal biocomposite showed the formation of urethane group at 3333 cm−1 in the presence of polymeric diphenylmethane di-isocyanate. Glass transition temperature of polypropylene–sisal was slightly increased to 6.8°C by chemical modification with polymeric diphenylmethane di-isocyanate. Yield strength of polypropylene–sisal (30 wt%) was enhanced by more than 50% with polymeric diphenylmethane di-isocyanate chemical treatment. Halpin–Tsai and Nielsen theoretical mathematical models showed a good agreement with experimental results of polypropylene–untreated sisal and polypropylene–treated sisal, respectively.
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Kaveh, M., R. Chayjan Amiri, and M. Esna-Ashari. "Thermal and physical properties modelling of terebinth fruit (Pistacia atlantica L.) under solar drying." Research in Agricultural Engineering 61, No. 4 (June 2, 2016): 150–61. http://dx.doi.org/10.17221/45/2013-rae.
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A laboratory solar dryer was used to study terebinth fruit drying. Two solar collectors were adjusted in east-west directions with the angle of 45°. Initial moisture content of terebinth fruit was dried under natural and forced airflow. In order to predict terebinth moisture content during drying process five mathematical models were used. Colour change and shrinkage of the terebinth samples were calculated. Results showed that the Page model had the best performance in moisture content prediction of terebinth samples. Effective moisture diffusivity of terebinth fruit was increased under forced convection. The lowest colour change and shrinkage of the samples in natural air flow condition were observed. Maximum rupture force and energy values were obtained at maximum airflow velocity. Models were fitted to the experimental data of physical, thermal and mechanical properties of terebinth fruit with high correlation coefficients.
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Gendels, S. "Application of Mathematical Models in Analysis of Heat Losses in the Buildings." Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 1 (June 26, 2006): 341. http://dx.doi.org/10.17770/etr2003vol1.1987.
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Physical model of heat balance for separate living room is discussed, which allows to analyse the distributions of the flow of air and temperature depending on the physical conditions and geometry. The model enables to choose the optimal surface area of building elements and their properties in order to decrease the heat losses and improve the conditions of thermal comfort. Room with bounding constructions and real dimensions is modelled that helps to understand the peculiarities of heat transfer process in the room as well as distribution of various characteristic quantities and their dependence on the different conditions. Multiple parameters are varied in 2D calculations and their influence on the distributions of temperature and velocity fields is analysed, which characterises the conditions of the thermal comfort. On the basis of considered model, the quantity of heat has been estimated that inflows or outflows through the bounding constructions. The power of convector is estimated, too, at a given temperature of the surface of convector. It is possible to estimate the heat transfer coefficients of the surfaces of bounding constructions with various properties, what requires considerable effort in real conditions of exploitation. One of the conditions of comfort is the temperature difference between frontal walls of the room – it should be less than some degrees. Essential role is played also by the intensity of air flow mostly because it increases heat transfer. Hence, flows between the room and outside environment are created with significant heat losses (so called convective heat losses). The influence of various geometric parameters on the character of the flow of air is analysed. The software ANSYS/FLOTRAN 5.5, where the turbulence is described by k- ? model, has been used for the elaboration of the heat balance model of the room.
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Sarsam, Saad I. "Modeling the Thermal Behavior of the Viscoelastic Properties of Asphalt Concrete." Britain International of Exact Sciences (BIoEx) Journal 4, no. 2 (September 2, 2022): 79–91. http://dx.doi.org/10.33258/bioex.v4i2.729.
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The viscoelastic properties of asphalt concrete are susceptible to the variation in the pavement temperature. In the present work, asphalt concrete beam specimens were prepared at optimum binder content and tested under repeated flexural stresses for fatigue life. Three testing temperature were implemented (5, 20, and 30) ℃. The variation in the phase angle, dissipated energy, flexural stiffness, and permanent deformation due to the testing temperatures were monitored and modeled. It was concluded that the viscoelastic properties of asphalt concrete are highly sensitive to the variation in testing temperature. The phase angle and the permanent deformation increases sharply as the testing temperature rises. However, the dissipated energy and the flexural stiffness declines as the testing temperature rise. Mathematical models were obtained which can be implemented in identifying the thermal behavior of the viscoelastic properties of asphalt concrete.
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Мурзин, В. В., and К. М. Сое. "Development of physical models for calculating thermal fields in wet underwater welding." MORSKIE INTELLEKTUAL`NYE TEHNOLOGII), no. 3(53) (August 27, 2021): 60–63. http://dx.doi.org/10.37220/mit.2021.53.3.007.
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В статье рассматривается влияние на развитие технологии мокрой подводной сварки использование методов математического моделирования значительно облегчает исследование тепловых потоков, что позволяет рассчитать скорость охлаждения металла в опасном диапазоне температур (800-500оС) и определить свойства металла сварного соединения. Определяющую роль в сварке играет теплообмен, который формирует протекание физико-химических, диффузионных, гидродинамических процессов. Форма сварочной ванны, а значит, объем и теплосодержание характеризуется ее длиной, шириной, толщиной и глубиной проплавления основного металла. Сварочная ванна ограничивается изотермической поверхностью, имеющей температуру плавления основного металла. Предполагается, что на свойства сварного соединения влияет только энергия, поступающая в основной металл. В известных физических образах и математических моделях теплового процесса сварки и наплавки не рассматривается, какое влияние на околошовную зону оказывают потоки теплоты от объема (массы) металла сварочной ванны, хотя в некоторых моделях изучается влияние скрытой теплоты плавления на тепловое состояние основного металла. The article discusses the impact on the development of wet underwater welding technology the use of mathematical modeling methods significantly facilitates the study of heat flows, which allows us to calculate the cooling rate of the metal in the dangerous temperature range (800-500oC) and determine the properties of the metal of the welded joint. The decisive role in welding is played by heat transfer, which forms the flow of physico-chemical, diffusion, and hydrodynamic processes. The shape of the weld pool, and hence the volume and heat content, is characterized by its length, width, thickness, and depth of penetration of the base metal. The welding bath is limited to an isothermal surface having a melting point of the base metal. It is assumed that the properties of the welded joint are affected only by the energy entering the base metal. In the known physical images and mathematical models of the thermal process of welding and surfacing, it is not considered what effect the heat fluxes from the volume (mass) have on the near-seam zone) the effect of the latent heat of melting on the thermal state of the base metal is studied in some models.
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Selivanova, Z. M., and T. A. Hoang. "Mathematical Models and Algorithms for Improving Information-Measuring Systems of Nondestructive Testing of Thermal Physical Properties of Materials." Vestnik Tambovskogo gosudarstvennogo tehnicheskogo universiteta 22, no. 4 (2016): 520–34. http://dx.doi.org/10.17277/vestnik.2016.04.pp.520-534.
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Mikhno, O., I. Patrakeyev, and N. Levinskova. "ANALYSIS OF TACTICAL PROPERTIES OF MODERN GEOINFORMATIONAL MONITORING." Visnyk Taras Shevchenko National University of Kyiv. Military-Special Sciences, no. 2 (46) (2021): 74–80. http://dx.doi.org/10.17721/1728-2217.2021.46.74-80.
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Geoinformational monitoring of urban environment is a necessary component of modern military-geographical description of military operation theater. The polymorphism property of modern geoinformational monitoring can be attributed to tactical properties, since it significantly expands range of decryption features of territory to be studied. The essence of polymorphism property of geoinformational monitoring is as follows: the same object of monitoring or the same phenomenon or process can be represented by different models. This property of geoinformational monitoring allows to preserve the integrity of representation of monitoring objects due to the invariance of description of objects and to bring the study of tasks of one type of monitoring to tasks of another type. Consistency of disparate models of monitoring objects is carried out provided that they belong to a given category of models. A constructive approach to the integration of different types of models of monitoring objects in the system of geoinformational monitoring is using methods of categorical-functional analysis. The mathematical apparatus of category theory allows the formalization of structures of complex systems in the form of sets of morphisms and objects of category of structured sets. This allows us to preserve integrity of representation of monitored object, and the consistency of its disparate models based on the analysis of their belonging to a given category of models. The paper presents the mathematical apparatus of implementation of this method, which is the theoretical basis of properties of polymorphism of geoinformational monitoring. The property of polymorphism allows us to increase the efficiency of processes of observation, evaluation, control and management of urban environment on basis of a heterogeneous polymodel complex, which forms information space of object of monitoring. Specific models of practical implementation of the polymorphism properties of geoinformational monitoring on the example of anomalous zones of density of vehicles and thermal field of the city surface are considered.
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Vahala, George, Pavol Pavlo, Linda Vahala, and Nicos S. Martys. "Thermal Lattice-Boltzmann Models (TLBM) for Compressible Flows." International Journal of Modern Physics C 09, no. 08 (December 1998): 1247–61. http://dx.doi.org/10.1142/s0129183198001126.
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The progress and challenges in thermal lattice-Boltzmann modeling are discussed. In particular, momentum and energy closures schemes are contrasted. Higher order symmetric (but no longer space filling) velocity lattices are constructed for both 2D and 3D flows and shown to have superior stability properties to the standard (but lower) symmetry lattices. While this decouples the velocity lattice from the spatial grid, the interpolation required following free-streaming is just 1D. The connection between fixed lattice vectors and temperature-dependent lattice vectors (obtained in the Gauss–Hermite quadrature approach) is discussed. Some (compressible) Rayleigh–Benard simulations on the 2D octagonal lattice are presented for extended BGK collision operators that allow for arbitrary Prandtl numbers.
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Mandal, Sumit, Simon Annaheim, Martin Camenzind, and René M. Rossi. "Characterization and modelling of thermal protective performance of fabrics under different levels of radiant-heat exposures." Journal of Industrial Textiles 48, no. 7 (February 28, 2018): 1184–205. http://dx.doi.org/10.1177/1528083718760801.
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The investigation of thermal protective performance of fabrics is highly relevant in order to procure and further develop the firefighters' protective clothing. Therefore, this paper aims at investigating the thermal protective performance of fabrics used in firefighters' clothing under different levels of radiant-heat exposures. For this, properties of a set of thermal protective single- and multi-layered fabrics were measured, and these fabrics were tested under radiant-heat exposures using the Method B of ISO 6942:2002 standard. During the testing, fabrics were exposed to low (10 kW/m2), medium (40 kW/m2), and high (80 kW/m2) intensity radiant-heat exposures; and the heat transfer level (i.e., time required to increase the skin temperature of a wearer/firefighter by certain degrees) through these fabrics were calculated to measure their thermal protective performance. The effects of fabric parameters, structures, properties, and radiant-heat intensities on the protective performance were characterized, and fabric properties that significantly affected the protective performance were statistically identified at different level of radiant-heat exposures. It has been found that weight, thickness, thermal resistance, and evaporative resistance can positively affect the protective performance. Also, the significant fabric properties affecting the protective performance vary for single- and multi-layered fabrics. By using these significant properties, the protective performance of single- and multi-layered fabrics were also separately predicted by mathematical models, i.e., multiple linear regression models and multiple logarithmic regression models. As per the findings of this study, multiple linear regression models can effectively be used to predict the thermal protective performance of fabrics. This study will lead towards building a better understanding and prediction of thermal protective performance of fabrics under radiant-heat exposures.
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MARCHWIŃSKI, Janusz. "Theoretical Models of PV-EC Windows Based on the Architectural Analysis of PV-EC Technologies." Architecture, Civil Engineering, Environment 15, no. 2 (June 1, 2022): 95–107. http://dx.doi.org/10.2478/acee-2022-0018.
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Abstract The paper provides an architectural analysis of the switchable PV-EC glazing technology based on combining photovoltaic (PV) technology with electrochromic (EC) glazing. The integration of these technologies is considered to constitute future-oriented façade solutions in shaping buildings that are energy-saving and environmentally friendly. The paper aims to define theoretical models of windows using PV-EC technology as solutions adequate from the architectural point of view. To achieve this goal, a comparative analysis of three PV-EC technologies was conducted, i.e., side-by-side (SBS) technology and tandem technologies, namely tandem solid technology (TST) and tandem liquid technology (TLT). The analysis covered functional aspects related to such issues as thermal and visual comfort, energy and aesthetics. The analysis led to extracting the features of the three compared technologies; consequently, their strengths and weaknesses were determined. As a result, seven window models were developed which, based on the above analysis and the insights derived from it, were recognized as the solutions in which the potential of PV and EC technology is best used. The dominant advantages of SBS, being the most developed technology and one with the greatest flexibility in construction applications, are indicated. The research is of a contributory nature, as it constitutes the basis for further numerical and simulation research. Such studies may prove useful to architects in making design decisions, especially at the initial design stages. However, at the current stage of technological development, the study mainly serves as an introduction to further research on improving the PV-EC properties towards integration with the building and its architecture.
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Cheremisin, D. D., S. A. Novokreschenov, V. S. Shvydkiy, and V. P. Zhukov. "Mathematical modelling of the thermal regime of a ladle- furnace unit considering internal heat sources." Proceedings of Irkutsk State Technical University 25, no. 4 (September 1, 2021): 509–18. http://dx.doi.org/10.21285/1814-3520-2021-4-509-518.
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We apply mathematical modelling to study heat transfer processes during fire refining of blister copper in a ladle-furnace unit. A ladle-furnace unit was designed to test the refining technology using bottom blowing in a bubble mode by gaseous reducing agents (hydrocarbons) and an oxidiser. Mathematical modelling allows the properties of a real process to be described based on mathematical formalisation of physical laws and regularities. It was proposed to use gaseous reducing agents, rather than expensive residual fuel, as a liquid-reducing agent. The use of gaseous reducing agents in the bottom blowing mode produces higher technical and economic indicators of the process. In addition, some technological operations were transferred directly to the ladle, thereby eliminating the need for re-melting and heating of refined copper. One of the identified problems was the need to maintain the predetermined thermal regime, which provides the very possibility of both performing refining operations and introducing a gaseous reagent (determining the hydro-gas-dynamic parameters) into the melt during bottom blowing. An original method for considering the thermal effects of chemical reactions in mathematical models was presented using an example of exothermic reactions during oxidative refining. The use of two different methods of analysis allowed a comprehensive assessment of the influence of the main exothermic reactions on the thermal regime of the refining process. The presented mathematical models can be used for determining the specific effect of various technological parameters (composition and fuel consumption, temperature and degree of blast enrichment, lining design, etc.) on the dynamics of changes in the temperature field of the melt and the technical and economic parameters of melting as a whole.
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Ostroukh, Andrey, Andrey Mavrin, and Nataliya Surkova. "Technological Processes Automation of Chemical Heat Treatment at Industrial Enterprises." Advanced Materials Research 1098 (April 2015): 120–25. http://dx.doi.org/10.4028/www.scientific.net/amr.1098.120.
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This paper presents analysis of chemical and thermal processing (CTP) methods to support multi-component gas atmosphere processes and their mathematical models as objects in the automated process control system (APCS). CTP mathematical models, algorithms, interaction structures and concepts of APCS components based on a specialized electronic controller have been proposed and implemented. The system provides a time control of all the necessary gas atmosphere parameters – its composition, temperature, pressure, with the possibility of using saturating medium of up to four components. Implementation of the system will improve the service properties of processed products, reduce the rate of spoilage and the psychophysical stress of the production staff, as well as reduce the overall CTP time.
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Pavlinic, Daniela Zavec, Eugene H. Wissler, and Igor B. Mekjavic. "Using a mathematical model of human temperature regulation to evaluate the impact of protective clothing on wearer thermal balance." Textile Research Journal 81, no. 20 (September 14, 2011): 2149–59. http://dx.doi.org/10.1177/0040517511414971.
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Thermal factors are often important in determining whether a given clothing ensemble is suitable for use under specified conditions. Although final approval of a particular ensemble often involves field trials, the need for such trials can be minimized by measuring the thermal properties of the garment using a heated manikin and then predicting human behavior using a mathematical human thermal model. While many laboratories are capable of measuring the properties of garments using manikins and several mathematical models exist, there have been very few published comparisons of actual human behavior with model predictions. The purpose of this paper is to present such a comparison for soldiers wearing a Slovene Armed Forces summer clothing ensemble during a three-hour hike across a 160 m high ridge. Values measured during the trial were: oxygen consumption; skin and core temperatures; regional thermal fluxes; clothing temperature; and environmental conditions. Subjective assessments of thermal comfort were made at regular intervals during the hike. Agreement between predicted and actual behavior was reasonable, although there were significant differences which could be attributed both to deficiencies in the model and to difficulties inherent in conducting field trials of this kind.
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Sanin-Villa, Daniel. "Recent Developments in Thermoelectric Generation: A Review." Sustainability 14, no. 24 (December 15, 2022): 16821. http://dx.doi.org/10.3390/su142416821.
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The world’s growing energy demand poses several concerns regarding the rational and efficient use of energy resources. This is also the case for many industrial processes, where energy losses and particularly thermal losses are common. Thermoelectric generators offer an alternative to address some of these challenges by recovering wasted heat and thereby increasing the overall efficiency of these processes. However, the successful operation of the thermoelectrical modules meant to carry this process is only possible when pairing these to an external control system; such a system plays an important role in predicting and operating such modules at its maximum power point. In this review paper, recent developments in the field of thermoelectric technology are discussed along with their mathematical models, applications, materials, and auxiliary devices to harvest thermal energy. Moreover, new advancements in phenomenological models are also discussed and summarized. The compiled evidence shows that the thermal dependence properties on the thermoelectric generator material’s modules and the mismatching thermal conditions play an important role in predicting power output in those systems, which prove the importance of including those parameters to enhance the accuracy of the energy production prediction. In addition, based on the evaluation of the mathematical models, it is shown that more studies are required to fill the gap between the current state-of-the-art of the technology and adjacent modeling techniques for the design and evaluation of thermal energy harvesting systems employing thermoelectric arrays under mismatching thermal conditions.
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Onal, Levent, and Sabit Adanur. "Modeling of Elastic, Thermal, and Strength/Failure Analysis of Two-Dimensional Woven Composites—A Review." Applied Mechanics Reviews 60, no. 1 (January 1, 2007): 37–49. http://dx.doi.org/10.1115/1.2375143.
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The usage of textile structures as a reinforcement for polymer composites became essential in many industrial applications in, for example, the marine and aerospace industries because of their favorable stiffness and strength to weight ratio. Determination of elastic properties and failure behavior of textile reinforced composites is vital for industrial design and engineering applications. This paper aims to present a review of numerical and analytical models for elastic, thermal, and strength/failure analysis of 2D reinforced woven composites. Major modeling techniques and approaches are presented. A state of the art review of woven fabric composites is presented starting from earlier one-dimensional models to recent three-dimensional models. The intention is not to give a detailed analysis of the mathematical approaches to the models discussed, but rather to inform researchers about the main ideas of previous works. This review article cites 122 references.
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Rodicheva, Margarita V., Anton V. Abramov, Nikolai N. Utkin, and Polina M. Malyarova. "NEW APPROACHES TO THERMAL CALCULATIONS OF VENTILATED CLOTHING." Technologies & Quality 56, no. 2 (August 25, 2022): 11–15. http://dx.doi.org/10.34216/2587-6147-2022-2-56-11-15.
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It is shown that the existing mathematical models of heat transfer do not fully take into account the real shape and dimensions of the air layers of ventilated clothing. A numerical modelling method is proposed that takes into account the influence of the morphology of the human body and the physical and mechanical properties of textile materials on the size and shape of the air gap. Peculiarities of convective processes in the air interlayers of ventilated clothing at the ambient temperature of +27 °C are revealed by the calcula-tions. The zones of intensification and deceleration of the air flow under the clothes were revealed. It is shown that the results of calculations are consistent with the results of experimental studies.
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Shulpekov, A. M., and O. V. Lapshin. "Self-propagating high-temperature synthesis in a thin-layer CuO–B–glass system." Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Universitiesʹ Proceedings. Powder Metallurgy аnd Functional Coatings), no. 3 (September 16, 2018): 46–54. http://dx.doi.org/10.17073/1997-308x-2018-3-46-54.
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The paper provides experimental research and mathematical models of wave synthesis and thermal explosion in a thin-layer CuO–B–glass system. It is found that burning front propagation has a multi-source behavior and its rate depends on reacting layer thickness by the parabolic law with a maximum at d = 4·10–4m. Increased reacting layer thickness improves thermal explosion properties in this system, and dilution with an inert component makes it possible to obtain copper coatings featuring good electrical conductivity. X-ray phase analysis and optical microscopy demonstrated that the coating consists of metallic copper drops fused together and surrounded by boron-lead silicate glass melt. Coatings have high electrical conductivity comparable with that of metals. It is found that layer thickness increased over 4·10–4m results in a significantly reduced layer propagation rate due to initial mixture loosening under the evaporation effect of water vapors and gases adsorbed on powders, and, as a consequence, it results in reduced heat transfer in the burning front. These coatings are not electrically conductive. Mathematical models of wave synthesis and thermal explosion in a thin-layer CuO–B–glass system using macroscopic approximation. Process dynamics are numerically calculated. Theoretical estimates correspond satisfactorily to experimental values. Thermophysical and thermokinetic process constants are determined by the inverse problem method. Experimental data obtained and mathematical models developed made it possible to obtain prototypes of electric film heaters with high electrical conductivity and operating temperature.
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Rădulescu, Bruno, Andrei Marius Mihalache, Adelina Hrițuc, Mara Rădulescu, Laurențiu Slătineanu, Adriana Munteanu, Oana Dodun, and Gheorghe Nagîț. "Thermal Expansion of Plastics Used for 3D Printing." Polymers 14, no. 15 (July 28, 2022): 3061. http://dx.doi.org/10.3390/polym14153061.
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The thermal properties of parts obtained by 3D printing from polymeric materials may be interesting in certain practical situations. One of these thermal properties is the ability of a material to expand as the temperature rises or shrink when the temperature drops. A test experiment device was designed based on the thermal expansion or negative thermal expansion of spiral test samples, made by 3D printing of polymeric materials to investigate the behavior of some polymeric materials in terms of thermal expansion or contraction. A spiral test sample was placed on an aluminum alloy plate in a spiral groove. A finite element modeling highlighted the possibility that areas of the plate and the spiral test sample have different temperatures, which means thermal expansions or contractions have different values in the spiral areas. A global experimental evaluation of four spiral test samples was made by 3D printing four distinct polymeric materials: styrene-butadiene acrylonitrile, polyethylene terephthalate, thermoplastic polyurethane, and polylactic acid, has been proposed. The mathematical processing of the experimental results using specialized software led to establishing empirical mathematical models valid for heating the test samples from −9 °C to 13 °C and cooling the test samples in temperature ranges between 70 °C and 30 °C, respectively. It was found that the negative thermal expansion has the highest values in the case of polyethylene terephthalate and the lowest in the case of thermoplastic polyurethane.
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Arias-Hernández, L. A., G. Ares de Parga, and F. Angulo-Brown. "On Some Nonendoreversible Engine Models with Nonlinear Heat Transfer Laws." Open Systems & Information Dynamics 10, no. 04 (December 2003): 351–75. http://dx.doi.org/10.1023/b:opsy.0000009556.27759.11.
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In this work, we analyze a nonendoreversible thermal engine model with a nonlinear heat transfer law between the heat reservoirs and the working fluid under two optimization criteria: the maximum power regime and the so-called ecological criterion. We find that this nonendoreversible model has a similar behaviour to that shown by De Vos (Am. J. Phys. 53, 570 (1985)) for endoreversible models with two thermal conductances with only one superior conductance and with only one inferior conductance, respectively. The model is compared with two sets of real power plants, the first one containing power plants of old design (before 1960's) and the second one being formed by modern nuclear power plants. Our results suggest that the first group was designed under conditions which are reminiscent of a maximum power regime and the second one under an ecological-like criterion. We also study some general properties of nonendoreversible thermal engine models.
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Karasik, E. V., and Yu S. Hordieiev. "Calculation of thermal expansion, glass transition temperature and glass density in the system RO–Al2O3–B2O3–SiO2 (where RO=BaO, SrO, CaO, MgO, ZnO)." Voprosy Khimii i Khimicheskoi Tekhnologii, no. 6 (December 2020): 69–74. http://dx.doi.org/10.32434/0321-4095-2020-133-6-69-74.
Full textAbstract:
Glasses of the system RO–Al2O3–B2O3–SiO2 are used as a base for the fabrication of heat-resistant nonmetallic materials and general-purpose products. The purpose of this work is to develop mathematical models for calculating the temperature coefficient of linear expansion, glass transition temperature and density as a function of the composition of glass in the oxide system RO–Al2O3–B2O3–SiO2 where RO=BaO, SrO, CaO, MgO, ZnO. The disadvantage of the known models is that the range of their application is limited by the quantitative content of components in the glass. At the same time, an increase in the sample size of experimental compositions made it possible to obtain more accurate mathematical models for calculating these properties. The glasses included in the experimental sample are distinguished by a wide range of temperature coefficient of linear expansion (from 30 to 10510–7 К–1). The glass transition temperature of these glasses is within the range of 580–7100C, which allows a reasonable approach to the choice of temperature regime for the formation of the structure vitreous and glass-ceramic materials for different functional purposes. The mathematical models were developed with the use of the experimental and statistical method. The obtained mathematical models are adequate to the experimental data and allow calculating the thermal expansion, glass transition temperature and density of glasses; the mean-square deviations of temperature coefficient of linear expansion, glass transition temperature and density being 1.910–7 К–1, 16.00C and 0.06 g cm–3, respectively. Their accuracy is sufficient for the development of basic glass compositions for various functional purposes.
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Baba Babanli, Mustafa, Liubov Shumska, and Maryna Leshchenko. "Heat Treatment Technology of Porous Building Materials with Predictability of Thermophysical Properties." International Journal of Engineering & Technology 7, no. 3.2 (June 20, 2018): 501. http://dx.doi.org/10.14419/ijet.v7i3.2.14579.
Full textAbstract:
The work is devoted to theoretical and experimental research of thermophysical features of the creation of new porous heat insulating materials, precisely: research of thermodynamic parameters of the heating processes, swelling and drying of materials; substantiation of the choice of the raw mixture method formation and determination of the optimal energy parameters of the swelling process; development of mathematical models of material heat treatment process and methods of basic technological parameters determination; development of advanced technologies for thermal protection of buildings and power equipment. Experimentally determined dependencies of technological parameters of heat treatment of the raw material mixture in the discharge, its composition, which allows obtaining material with minimal thermal conductivity. Also, the resulting dependencies ensure to find the required mode of heat treatment for the given thermophysical properties. The experimental setup has been developed, which provided to determine the basic laws of heat transfer of porous material, on the basis of which data were obtained, which allow to carry out an estimation of heat transfer and exchange characteristics of the new dispersed porous material necessary for technological calculations. A complex mathematical model of the heat energy mode of the building was created, as well as a program for solving the equations of this model, which makes it possible to determine the basic energy characteristics.
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Jastaneyah, Zuhair, Haslinda Kamar, and Hakim Al Garalleh. "A Review Paper on Thermal Comfort and Ventilation Systems in Educational Buildings: Nano-Mechanical and Mathematical Aspects." Journal of Nanofluids 12, no. 1 (February 1, 2023): 1–17. http://dx.doi.org/10.1166/jon.2023.1902.
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Thermal comfort has always been an essential factor that affects students’ productivity and success. Students spend considerable time at their schools or universities more than any other building type except their homes. Thus, indicating the importance of providing thermal comfort in educational buildings. Many studies worldwide are conducted to assess and optimize thermal comfort inside classrooms. However, the results have not been accurate even for similar study conditions due to the differences in the studies’ conditions. This paper focuses on thermal comfort studies in educational buildings (classrooms). The studies are divided into two sections, the first covering field studies methodologies, objective, and subjective questionnaires, and the second reviewing thermal comfort results based on the climatic zone, educational level, and analysis approach. It is recommended that thermal comfort studies be carried out using rational and adaptive models as they provide more accurate, reliable results. Also, it is found that thermal comfort standards are generally inadequate to assess thermal comfort in classrooms. Thus, other international standards should be created and considered for classroom assessment. Over the past few years, the combination between nanotechnology and architecture engineering has been widely used in several disciplines because of its crucial significance in finding new nanodevices to contribute in reducing of energy consumption, particularly on construction materials. Filling functionalized tools with nanoparticles plays a critical role in improving the thermal and optical properties, particularly with respect to nanofluids applications, i.e., buildings applications of thermal comfort. The experimental results of long-term studies show that the calculation values of optimization have a consistent agreement with the experimental transmission of nanofluids models.
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Bizon, Katarzyna. "Application of Pseudohomogeneous and Heterogeneous Models in Assessing the Behavior of a Fluidized-Bed Catalytic Reactor." Energies 14, no. 1 (January 3, 2021): 208. http://dx.doi.org/10.3390/en14010208.
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Comparative analysis of the steady-state and transient properties of a bubbling fluidized-bed catalytic reactor obtained according to different mathematical models of the emulsion zone was performed to verify the commonly used assumption regarding the pseudohomogeneous nature of this zone. Four different mathematical models of the fluidized-bed reactor dynamics were formulated, based on different thermal and diffusional conditions at the gas-solid interface and within the catalyst pellet, namely the model based on the assumption of pseudohomogeneous character for the emulsion zone, and a group of two-scale models accounting for the heterogeneous character of this zone. It was demonstrated that, while the pseudohomogeneous model of the emulsion zone predicts almost identical behavior of the reactor at steady-state as the proposed heterogeneous models, it may fail in the prediction of the reactor start-up behavior, especially when dealing with highly exothermic processes run at relatively high fluidization velocity.
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Benner, Michael, and Alfred Rieckers. "Spectral Properties Of Weakly Inhomogeneous Bcs-Models In Different Representations." Zeitschrift für Naturforschung A 60, no. 5 (May 1, 2005): 343–65. http://dx.doi.org/10.1515/zna-2005-0506.
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For a class of Bardeen-Cooper-Schrieffer (BCS)-models, with complex, weakly momentum dependent interaction coefficients, the representation dependent effective Hamiltonians and their spectra are reconsidered in order to obtain a consistent physical picture by means of operator algebraic methods. The starting point is the limiting dynamics, the existence of which had been proved in a previous work, in terms of a C*-dynamical system acting in a classically extended, electronic Canonical Anticommutation Relations (CAR)-algebra. The C*-algebraic KMS-theory, including the low temperature limit, specifies the order parameters. These appear as classical observables, which commute with all other observables, constituting elements of the center of the algebra. The algebraic spectral theory, in the sense of Arveson, is first applied to the dynamics in general pure energy state representations. The spectra of the finite temperature representations are analyzed, identifying the gap as the lowest of those energy values, which are stable under local perturbations. Further insights are obtained by decomposing the thermal dynamical systems into the pure energy state Heisenberg dynamics, after having first extended them to more comprehensive W*-dynamical systems. The decomposing orthogonal measure is transferred to the infinite product space of quasi-particle occupation numbers and its support is characterized in terms of 0-1-laws leading to an asymptotic ratio of quasi-particles and holes, which depends on the temperature. This ratio is connected with an algebraic invariant of the representation dependent observable algebra. Energy renormalization aspects and pair occupation probabilities are discussed. The latter reveal, beside other things, the difference between macroscopic term occupation and coherent macroscopic term occupation for a condensate.
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Selivanova, Z. M., and V. S. Eryshova. "Reconfigurable Information-Measuring System of Thermophysical Properties of Solid Materials with an Intelligent Sensor." Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, no. 5 (128) (October 2019): 4–19. http://dx.doi.org/10.18698/0236-3933-2019-5-4-19.
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An information-measuring system for non-destructive testing of thermophysical properties of solid materials with an intelligent sensor has been developed. Mathematical models for reconfiguring the structure of the information-measuring system and the intelligent sensor were built. Algorithms for changing the configuration of the intelligent sensor and the functioning of the information-measuring system have been developed, allowing us to expand the systems functionality for studying thermophysical properties of solid materials in a wide range of thermal conductivities, as well as to improve the accuracy and efficiency of thermophysical measurements by adapting the system to the class of materials studied.