scholarly journals Crystal - Rotator-I - Rotator-II Phase Transitions in the Mixtures of Alkanes

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Prabir Kumar Mukherjee
Keyword(s):  
Phase Transitions ◽  
Binary Mixture ◽  
Landau Theory ◽  
Order Parameters ◽  
Experimental Results ◽  
Transition Temperatures ◽  
First Order ◽  
Isotropic Mixing ◽  
Theoretical Results ◽  
Good Agreement

Using the combination of Flory–Huggins theory of isotropic mixing and Landau theory, we discuss the crystal – rotator-I – rotator-II phase transitions in the binary mixture of alkanes. The influence of concentration on the order parameters and the transition temperatures is discussed. Theoretical results show the first order character of both the rotator-I to crystal and rotator-II to rotator-I phase transitions in the mixture of alkanes. A good agreement between theoretical and experimental results are presented in this paper.

Models for New Corrugated and Porous Solar Air Collectors under Transient Operation

2017 ◽  
Vol 42 (1) ◽  
Author(s):  
Qahtan Adnan Abed ◽  
Viorel Badescu ◽  
Adrian Ciocanea ◽  
Iuliana Soriga ◽  
Dorin Bureţea
Keyword(s):  
Climatic Conditions ◽  
Meteorological Conditions ◽  
Bias Error ◽  
First Order ◽  
Solar Air Collector ◽  
Section Surface ◽  
South Eastern Europe ◽  
Main Components ◽  
Theoretical Results ◽  
Good Agreement

AbstractMathematical models have been developed to evaluate the dynamic behavior of two solar air collectors: the first one is equipped with a V-porous absorber and the second one with a U-corrugated absorber. The collectors have the same geometry, cross-section surface area and are built from the same materials, the only difference between them being the absorbers. V-corrugated absorbers have been treated in literature but the V-porous absorbers modeled here have not been very often considered. The models are based on first-order differential equations which describe the heat exchange between the main components of the two types of solar air heaters. Both collectors were exposed to the sun in the same meteorological conditions, at identical tilt angle and they operated at the same air mass flow rate. The tests were carried out in the climatic conditions of Bucharest (Romania, South Eastern Europe). There is good agreement between the theoretical results and experiments. The average bias error was about 7.75 % and 10.55 % for the solar air collector with “V”-porous absorber and with “U”-corrugated absorber, respectively. The collector based on V-porous absorber has higher efficiency than the collector with U-corrugated absorber around the noon of clear days. Around sunrise and sunset, the collector with U-corrugated absorber is more effective.

Vibration Characteristics of Straight Blades of Asymmetrical Aerofoil Cross-Section

1969 ◽  
Vol 20 (2) ◽  
pp. 178-190 ◽  
Author(s):  
W. Carnegie ◽  
B. Dawson
Keyword(s):  
Analytical Solution ◽  
Cross Section ◽  
Natural Frequencies ◽  
Equations Of Motion ◽  
Limited Range ◽  
First Order ◽  
Special Cases ◽  
Theoretical Results ◽  
Theoretical Procedure ◽  
Good Agreement

SummaryTheoretical and experimental natural frequencies and modal shapes up to the fifth mode of vibration are given for a straight blade of asymmetrical aerofoil cross-section. The theoretical procedure consists essentially of transforming the differential equations of motion into a set of simultaneous first-order equations and solving them by a step-by-step finite difference procedure. The natural frequency values are compared with results obtained by an analytical solution and with standard solutions for certain special cases. Good agreement is shown to exist between the theoretical results for the various methods presented. The equations of motion are dependent upon the coordinates of the axis of the centre of flexure of the beam relative to the centroidal axis. The effect of variations of the centre of flexure coordinates upon the frequencies and modal shapes is shown for a limited range of coordinate values. Comparison is made between the theoretical natural frequencies and modal shapes and corresponding results obtained by experiment.

scholarly journals Specific heat jump of two-band superconductor KFe2As2 using Ginzburg-Landau theory

2014 ◽  
Vol 32 (3) ◽  
pp. 465-469 ◽  
Author(s):  
I. Askerzade
Keyword(s):  
Specific Heat ◽  
Order Parameter ◽  
Landau Theory ◽  
Energy Functional ◽  
Order Parameters ◽  
Ginzburg Landau ◽  
Specific Heat Jump ◽  
Nonlinear Temperature Dependence ◽  
Nonlinear Temperature ◽  
Good Agreement

AbstractIn this study specific heat jump using two-gap Ginzburg-Landau (GL) theory has been calculated. In contrast to the previous approaches, we have taken into account intergradient order parameters interaction in the GL free energy functional. The thermodynamic magnetic field revealed nonlinear temperature dependence due to interband interaction between order parameters and their gradients. The calculations showed that the specific heat jump in two-order parameter superconductors was smaller than that of single-order parameter superconductors. It has been shown that such a model is in good agreement with experimental data for KFe2As2 superconductors.

scholarly journals Dynamical scaling for underdamped strain order parameters quenched below first-order phase transitions

2016 ◽  
Vol 94 (22) ◽  
Author(s):  
N. Shankaraiah ◽  
Awadhesh K. Dubey ◽  
Sanjay Puri ◽  
Subodh R. Shenoy
Keyword(s):  
Phase Transitions ◽  
Order Parameters ◽  
Dynamical Scaling ◽  
First Order ◽  
First Order Phase

Modeling of Phase Transitions Kinetics in Systems with Two Interacting Order Parameters

2016 ◽  
Vol 845 ◽  
pp. 166-169 ◽  
Author(s):  
Dmitry A. Kuzmin ◽  
Igor V. Bychkov ◽  
Ivan Yu. Biryukov ◽  
Alexander P. Kamantsev ◽  
Victor V. Koledov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Order Phase Transition ◽  
Transition Process ◽  
Order Parameters ◽  
First Order ◽  
First Order Phase Transition ◽  
1D Model ◽  
Coupled Solution ◽  
First Order Phase

We present common 1D model of first order phase transition based on coupled solution of order parameters evolution and heat transfer equations. Such a model may be used for simulation of phase transitions in multiferroics or magnetostructural phase transitions, for example. First order phase transition process has been described by Landau-Khalatnikov-like equation with the thermodynamic potential of 2-3-4 and 2-4-6 types.

Pressure Broadening of the Microwave Absorption Lines of Oxygen

1973 ◽  
Vol 51 (22) ◽  
pp. 2329-2331 ◽  
Author(s):  
Y. Yamamoto ◽  
M. Cattani
Keyword(s):  
Microwave Absorption ◽  
Quadrupole Moment ◽  
Microwave Spectrum ◽  
The Self ◽  
Experimental Results ◽  
Dispersion Interactions ◽  
Pressure Broadening ◽  
Line Widths ◽  
Theoretical Results ◽  
Good Agreement

We calculate the line widths for the self-broadening of the microwave spectrum of oxygen taking into account simultaneously quadrupole–quadrupole and dispersion interactions. Our theoretical results are compared with the more recent experimental results. A good agreement is obtained between them if the oxygen quadrupole moment is taken as Q = 1.21 ± 0.05 D Å.

Surface Roughness Effects in High-Speed Hydrodynamic Journal Bearings

1997 ◽  
Vol 119 (4) ◽  
pp. 776-780 ◽  
Author(s):  
H. Hashimoto
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Reynolds Equation ◽  
Computation Time ◽  
Experimental Results ◽  
Roughness Effects ◽  
Modified Reynolds Equation ◽  
Nonlinear Simultaneous Equations ◽  
Theoretical Results ◽  
Good Agreement

This paper describes an applicability of modified Reynolds equation considering the combined effects of turbulence and surface roughness, which was derived by Hashimoto and Wada (1989), to high-speed journal bearing analysis by comparing the theoretical results with experimental ones. In the numerical analysis of modified Reynolds equation, the nonlinear simultaneous equations for the turbulent correction coefficients are greatly simplified to save computation time with a satisfactory accuracy under the assumption that the shear flow is superior to the pressure flow in the lubricant films. The numerical results of Sommerfeld number and attitude angle are compared with the experimental results to confirm the applicability of the modified Reynolds equation in the case of two types of bearings with different relative roughness heights. Good agreement was obtained between theoretical and experimental results.

High-speed water jets from vertically accelerated rotating cones

1973 ◽  
Vol 60 (4) ◽  
pp. 703-719
Author(s):  
P. Savic ◽  
J. D. Allan ◽  
G. P. Van Blokland
Keyword(s):  
Explosive Charge ◽  
High Speed ◽  
Order Theory ◽  
Experimental Results ◽  
Viscous Drag ◽  
First Order ◽  
First Order Theory ◽  
Water Jets ◽  
Rotating Cone ◽  
Good Agreement

Water jets are produced by vertically accelerating a rotating cone partially filled with water. It is shown that the acceleration of the parabolic meniscus results in a motion similar to that observed in a shaped explosive charge (Monroe jet). Acceleration of the cone is effected by means of an inductive electromagnetic accelerating device (conical pinch) whose theory is developed in terms of the WKB approximation. A second-order inviscid theory for the motion of the fluid in the cone in terms of the Penney-Price linearization procedure is presented and it is shown that good agreement for the jet head velocity can be achieved for low velocities. At higher velocities, experimental results appear to lag behind the theoretical ones, probably owing to the dispersal of the jet head through viscous drag with the surrounding atmosphere. The shape of the jet at early times is well represented by first-order theory.

Atomic displacements at and order of all phase transitions in multiferroic YMnO3 and BaTiO3

2009 ◽  
Vol 65 (4) ◽  
pp. 450-457 ◽  
Author(s):  
S. C. Abrahams
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Cell Volume ◽  
Unit Cell Volume ◽  
Landau Theory ◽  
Unit Cell ◽  
Paramagnetic Phase ◽  
First Order ◽  
Atomic Displacements ◽  
Magnetic Symmetry

Coordinate analysis of the multiple phase transitions in hexagonal YMnO3 leads to the prediction of a previously unknown aristotype phase, with the resulting phase-transition sequence: P63′cm′(e.g.) ↔ P63 cm ↔ P63/mcm ↔ P63/mmc ↔ P6/mmm. Below the Néel temperature T N ≃ 75 K, the structure is antiferromagnetic with the magnetic symmetry not yet determined. Above T N the P63 cm phase is ferroelectric with Curie temperature T C ≃ 1105 K. The nonpolar paramagnetic phase stable between T C and ∼ 1360 K transforms to a second nonpolar paramagnetic phase stable to ∼ 1600 K, with unit-cell volume one-third that below 1360 K. The predicted aristotype phase at the highest temperature is nonpolar and paramagnetic, with unit-cell volume reduced by a further factor of 2. Coordinate analysis of the three well known phase transitions undergone by tetragonal BaTiO3, with space-group sequence R3m ↔ Amm2 ↔ P4mm ↔ Pm\overline 3m, provides a basis for deriving the aristotype phase in YMnO3. Landau theory allows the I ↔ II, III ↔ IV and IV ↔ V phase transitions in YMnO3, and also the I ↔ II phase transition in BaTiO3, to be continuous; all four, however, unambiguously exhibit first-order characteristics. The origin of phase transitions, permitted by theory to be second order, that are first order instead have not yet been thoroughly investigated; several possibilities are briefly considered.

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