scholarly journals Quasi-averaged formulation of Stefan's linear problem in drying of cylindrical beam

2021 ◽  
pp. 13-21
Author(s):  
Bogdana Hayvas ◽  
Veronika Dmytruk
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Porous Materials ◽  
Linear Problem ◽  
The Body ◽  
External Influence ◽  
Moving Surface ◽  
Body Components

In the process of drying of porous materials there is a moving surface separating the dried and wet areas in the body. This surface is a phase transition, which significantly depends on the properties of the material and the temperature, which is due to the external influence of the drying agent and is a function of coordinates and time, and the movement of boundaries is a consequence of phase transitions. The paper presents the properties of the material, namely: heat capacity, density, thermal conductivity coefficients to be the functions of the porosity of the material, densities and heat capacities of body components.

scholarly journals Теплофизические свойства мультиферроиков Bi-=SUB=-1-x-=/SUB=-Tm-=SUB=-x-=/SUB=-FeO-=SUB=-3-=/SUB=-

2022 ◽  
Vol 64 (2) ◽  
pp. 305
Author(s):  
С.Н. Каллаев ◽  
А.Г. Бакмаев ◽  
З.М. Омаров ◽  
Л.А. Резниченко
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Thermal Diffusivity ◽  
Mean Free Path ◽  
Antiferromagnetic Phase ◽  
Temperature Dependences ◽  
Additional Anomaly

Investigations of the heat capacity, thermal diffusivity, and thermal conductivity of multiferroics Bi1-xTmxFeO3 (x = 0, 0.05, 0.10, 0.20) have been carried out in the high temperature range of 300-1200 K. and thermal conductivity in the region of phase transitions. The temperature dependences of the specific heat for compositions with x = 0.10 and 0.20 exhibit an additional anomaly characteristic of the phase transition at T = 580 K. The dominant mechanisms of phonon heat transfer in the region of ferroelectric and antiferromagnetic phase transitions are considered. The temperature dependence of the average phonon mean free path is determined.

scholarly journals The origin of the lattice thermal conductivity enhancement at the ferroelectric phase transition in GeTe

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Đorđe Dangić ◽  
Olle Hellman ◽  
Stephen Fahy ◽  
Ivana Savić
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Transitions ◽  
Thermoelectric Materials ◽  
Ferroelectric Phase Transition ◽  
Lattice Thermal Conductivity ◽  
Ferroelectric Phase ◽  
Structural Phase ◽  
High Symmetry ◽  
Structural Phase Transitions

AbstractThe proximity to structural phase transitions in IV-VI thermoelectric materials is one of the main reasons for their large phonon anharmonicity and intrinsically low lattice thermal conductivity κ. However, the κ of GeTe increases at the ferroelectric phase transition near 700 K. Using first-principles calculations with the temperature dependent effective potential method, we show that this rise in κ is the consequence of negative thermal expansion in the rhombohedral phase and increase in the phonon lifetimes in the high-symmetry phase. Strong anharmonicity near the phase transition induces non-Lorentzian shapes of the phonon power spectra. To account for these effects, we implement a method of calculating κ based on the Green-Kubo approach and find that the Boltzmann transport equation underestimates κ near the phase transition. Our findings elucidate the influence of structural phase transitions on κ and provide guidance for design of better thermoelectric materials.

scholarly journals The GoogLeNet-assisted Phase Transition Detectors

2021 ◽  
Author(s):  
C. H. Wong ◽  
Raymond P. H. Wu ◽  
X. Lei ◽  
A. F. Zatsepin
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Xy Model ◽  
Superconducting Transition ◽  
Superconducting Nanowires ◽  
Superconducting Vortices ◽  
Bkt Transition ◽  
Superconducting Nanowire

Abstract The GoogLeNet model can completely split the overlapped phase transitions in the superconducting nanowire arrays under Josephson interaction. In the presence of the phase fluctuations in superconducting nanowires array, the electrical resistance of the superconducting nanowires is always non-zero unless the system undergoes Berezinskii-Kosterlitz-Thouless (BKT) transition where the superconducting vortices and anti-vortices form pairs. The two-dimensional XY model can mimic the superconducting transition temperature Tc and the BKT transition temperature TBKT by observing the heat capacity anomalies upon cooling. If the Josephson coupling across the nanowires is strong, the heat capacity anomalies almost overlap with each other so that the traditional curve-fitting techniques are difficult to completely distinguish between the Tc and the TBKT. To solve this issue, we apply an artificial-intelligence technique to completely split the overlapped heat capacity anomalies. After the GoogLeNet-assisted phase transition detector is built, the GoogLeNet model can learn from the features of the phase transitions and then interpret the Tc and TBKT in the ‘unseen’ system precisely. Our work opens a path for the GoogLeNet model to enter the world of superconductivity.

scholarly journals THERMOPHYSICAL PROPERTIES OF ALLOY COMPOSITIONS (2Bi2O3∙B2O3)100-x(2Bi2O3∙3GeO2)x (x=0, 10, 50)

2021 ◽  
pp. 44-48
Author(s):  
S.I. Bananyarli ◽  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Thermal Resistance ◽  
Temperature Dependence ◽  
Thermophysical Properties ◽  
Chemical Bonds ◽  
Temperature Range ◽  
The Difference

The termophisical properties, namely, the temperature dependence of thermal conductivity, thermal resistance and heat capacity of the allays compositions (2Bi2O3∙B2O3)100-x (2Bi2O3∙3GeO2)x in the (300–600) K temperature range have ligated been invest. An increase in thermal conductivity χ(T) above 500 K is probably associated with the softening of alloys and the presence of blurred phase transitions, which are accompanied by partial breaking of chemical bonds. It was revealed that the heat capacity in alloys of the compositions (2Bi2O3∙B2O3)100-x (2Bi2O3∙3GeO2)x increases with an increase in the GeO2 concentration. In the studied samples, that showed their own disorder during solidification, the thermal conductivity is strongly reduced due to the enhancement of the anharmonicity of phonon – phonon interactions. İn turn a small "disorder" introduced by defects due to the difference in masses is not noticeable against the background of the huge "disorder" inherent in oxide substances

scholarly journals Overview of Low-Temperature Heat Capacity Data for Zn2(C8H4O4)2.C6H12N2 and the Salam Hypothesis

Symmetry ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 657
Author(s):  
Svetlana Kozlova ◽  
Maxim Ryzhikov ◽  
Denis Pishchur ◽  
Irina Mirzaeva
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Low Temperature ◽  
Metal Organic Framework ◽  
Model System ◽  
Temperature Heat ◽  
Metal Organic ◽  
Low Temperature Heat Capacity ◽  
Capacity Data

The review presents the progress in the analysis of low-temperature heat capacity of the metal-organic framework Zn2(C8H4O4)2.C6H12N2 (Zn-DMOF). In Zn-DMOF, left-twisted D3(S) and right-twisted D3(R) DABCO molecules (C6H12N2) can transform into each other by tunneling to form a racemate. Termination of tunneling leads to a phase transition in the subsystem of twisted molecules. It is suggested that Zn-DMOF may be considered a model system to study the mechanisms of phase transitions belonging to the same type as hypothetical Salam phase transitions.

Dilatometric Study on Phase Transitions of Benzylidene-p-n-hexadecyl /Hexadecyloxy Anilines (5.O16, 5O.O16 and 5.16)

2011 ◽  
Vol 181-182 ◽  
pp. 67-70
Author(s):  
M. Ramakrishna Nanachara Rao ◽  
P.V. Datta Prasad ◽  
D. Madhavi Latha ◽  
V.G.K.M. Pisipati
Keyword(s):  
Phase Transition ◽  
Schiff Base ◽  
Phase Transitions ◽  
Liquid Crystalline ◽  
The Body ◽  
Phase Identification ◽  
Transition Temperatures ◽  
Phase Transition Temperatures ◽  
Characterization Studies ◽  
Density Results

Synthesis, characterization and phase transition studies (Dilatometry) have been carried out on three mesomorphic Schiff base compounds viz., N-(p-n-pentyl benzylidene)-p-n-hexadecyloxy aniline, 5.O16, N-(p-n-pentyloxy benzylidene)-p-n-hexadecyloxy aniline 5O.O16 and N-(p-n-pentyl benzylidene)-p-n-hexadecyl aniline, 5.16. The liquid crystalline phase identification and the phase transition temperatures have been carried out using SDTECHS polarising microscope attached with temperature controller with accuracy of ± 0.1 °C and for the conformation of the phase identification and the textures observed are compared with the standard textures. Further, the phase transition temperatures and the corresponding heats of transition across the phase transitions are recorded using DSC (Perkin Elmer). The characterization studies reveal that these compounds exhibit NG, N and A phase variants respectively. The nature of the phase transitions are studied through density results using dilatometric technique. The phase transitions exhibit first order nature in all the cases as expected. The results are discussed in the light of the body of the data available on other Schiff base compounds and on 5O.16.

Uncertainty Analysis of Thermal Protection by Microencapsulated Phase Change Micro/Nanoparticles during Hyperthermia

2011 ◽  
Vol 291-294 ◽  
pp. 1816-1819
Author(s):  
Yong Gang Lv ◽  
Yang Zou ◽  
Li Yang
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermal Protection ◽  
Treatment Protocol ◽  
Lower Phase ◽  
Phase Transition Temperatures ◽  
Protection Efficacy

Uncertainties for thermal protection efficacy caused by deviations of the values of phase change materials (PCMs) properties (including conductivity, heat capacity, thermal conductivity, latent heat and phase transition temperature) were studied based on our previous study. Our results suggested that the radius of the micro/nano PCM particle, and the upper and lower phase transition temperatures of the PCM should be carefully measured before performing thermal protection by PCMs during hyperthermia. The results will further help us to enlarge the application of clinical hyperthermia in cancer treatment and optimize the treatment protocol of thermal protection by PCMs.

Heat Capacity of K3LnCl6 Compounds with Ln = La, Ce, Pr, Nd

1999 ◽  
Vol 54 (3-4) ◽  
pp. 229-235 ◽  
Author(s):  
M. Gaune-Escard ◽  
L. Rycerz
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Liquid Phase ◽  
Temperature Dependence ◽  
Heat Capacities ◽  
Scanning Calorimetry ◽  
The Enthalpy Of Formation

The heat capacities of the solid and liquid K3LnCl6 compounds (Ln = La, Ce, Pr, Nd) have been determined by differential scanning calorimetry (DSC) in the temperature range 300 -1100 K. Their temperature dependence is discussed in terms of the phase transitions of these compounds as reported in literature. The heat capacity increases and decreases strongly in the vicinity of a phase transition but else varies smoothly. The Cp data were fitted by an equation which provides a satisfactory representation up to the temperatures of Cp discontinuity. The measured heat capacities were checked for consistency by calculating the enthalpy of formation of the liquid phase, which had been previously measured. The results obtained compare satisfactorily with these experimental data.

scholarly journals The Variation Mechanism of Thermal Properties of Loess with Different Water Contents during Freezing

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xihao Dong ◽  
Shuai Liu ◽  
Yuanxiang Yu
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Water Content ◽  
Volumetric Heat Capacity ◽  
Soil Particles ◽  
Water Ice ◽  
Variation Mechanism

The thermal properties of soils are affected by many factors, such as temperature, water content, and structure. Based on the transient plane source method of thermal physics, the thermal properties of loess with different water content during the freezing process were tested. We analyzed the variation mechanism of thermal properties from the perspective of phase change. Based on the Pore/Particle and Crack Analysis System (PCAS) and theory of heat transfer, we then analyzed the microstructure and heat conduction process of loess. And a calculation model of volumetric heat capacity of frozen soil was presented. The results show that, in the major phase transition zone, the variation of the thermal properties of loess with temperature is the most significant. And the thermal diffusivity increases sharply with the significant increase of thermal conductivity and the rapid decrease of volumetric heat capacity. Moisture content not only increases the thermal conductivity and volume heat capacity of loess but also makes the influence of temperature on the thermophysical parameters more significant. The effect of temperature on thermal properties is mainly due to the change of heat transfer media caused by phase transition of water-ice, followed by the change of thermal properties of heat transfer media such as soil particles, water, ice, and air with temperature. Increasing the water content reduces the contact thermal resistance between soil particles because of the increase in the thickness of the water film on the surface of soil particles and the thermal conductivity of the heat transfer medium between particles, thus changing the thermal properties of soils.

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