Phase Transition Dielectric Properties in Order-disorder Antiferroelectric NH4(H2PO4) (ADP) Crystal

2021 ◽  
Author(s):  
Muzaffar Iqbal Khan ◽  
Trilok Chandra Upadhyay
Keyword(s):  
Dielectric Properties ◽  
Coupled Model ◽  
Spin Interaction ◽  
Physical Parameters ◽  
Dihydrogen Phosphate ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
Model Hamiltonian ◽  
Adp Crystal ◽  
Good Agreement

Abstract A modified four sublattice pseudospin lattice coupled model Hamiltonian by adding extra spin-lattice interaction, direct spin-spin interaction has been used to study dielectric properties for ammonium dihydrogen phosphate (ADP) crystal. Using the double-time temperature-dependent Green’s function method, the expressions for soft mode frequency, dielectric permittivity and loss tangent have been derived. By fitting the model values of various physical parameters, the thermal variations of the above quantities are calculated and compared with the experimental results. Our theoretical obtained results are in good agreement with experimental data.

scholarly journals Dielectric Properties of Deuterated Cesium Dihydrogen Phosphate Crystal

2021 ◽  
Vol 16 (2) ◽  
Author(s):  
Muzaffar Iqbal Khan ◽  
Trilok Chandra Upadhyay ◽  
Pawan Singh ◽  
Sidharth Kashyap
Keyword(s):  
Dielectric Properties ◽  
Function Theory ◽  
Mode Frequency ◽  
Physical Parameters ◽  
Dihydrogen Phosphate ◽  
Thermal Dependence ◽  
Normal Mode Frequency ◽  
Coupled Mode ◽  
Dielectric Constant And Loss ◽  
Model Hamiltonian

Modified two sublattice pseudospin lattice coupled-mode model Hamiltonian has been applied to study the dielectric properties of deuterated cesium dihydrogen phosphate crystal. With the help of model Hamiltonian and Green’s function theory, the theoretical expressions for normal mode frequency, dielectric constant and loss tangent are derived. By fitting the model values of different physical parameters, the thermal dependence of the above quantities has been calculated. Our theoretical obtained results are well compared with experimental data.

scholarly journals CHANGES IN FERROELECTRIC PROPERTIES OF MASD ALUM ALONG WITH TEMPERATURE BY USING PLCM MODEL

2019 ◽  
Vol 14 (2) ◽  
Author(s):  
Anubhuti Mamgain ◽  
Trilok Chandra Upadhyay
Keyword(s):  
Ferroelectric Properties ◽  
Function Technique ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
Coupled Mode ◽  
Dielectric Constant And Loss ◽  
Double Time ◽  
Anharmonic Interactions ◽  
Theoretical Results ◽  
Good Agreement

With addition of third-and fourth-order phonon anharmonic interactions, and extra spin-lattice interaction term into pseudospin-lattice coupled mode (PLCM) model, MASD alum has been studied. Employing double time temperature dependent Green′s function technique expressions for shift and width of response function, normal mode frequency, dielectric constant and loss stangent have been derived for MASD alum. Numerical calculation has been done. Theoretical results have been compared with experimental results of Pepinsky et al. [16]. A good agreement has been found.

scholarly journals CHANGES IN FERROELECTRIC PROPERTIES OF MASD ALUM ALONG WITH TEMPERATURE BY USING PLCM MODEL

2019 ◽  
Vol 14 (2) ◽  
Author(s):  
Anubhuti Mamgain ◽  
Trilok Chandra Upadhyay
Keyword(s):  
Ferroelectric Properties ◽  
Function Technique ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
Coupled Mode ◽  
Dielectric Constant And Loss ◽  
Double Time ◽  
Anharmonic Interactions ◽  
Theoretical Results ◽  
Good Agreement

With addition of third-and fourth-order phonon anharmonic interactions, and extra spin-lattice interaction term into pseudospin-lattice coupled mode (PLCM) model, MASD alum has been studied. Employing double time temperature dependent Green′s function technique expressions for shift and width of response function, normal mode frequency, dielectric constant and loss stangent have been derived for MASD alum. Numerical calculation has been done. Theoretical results have been compared with experimental results of Pepinsky et al. [16]. A good agreement has been found.

Effect of shock waves on structural and dielectric properties of ammonium dihydrogen phosphate crystal

2019 ◽  
Vol 234 (9) ◽  
pp. 557-567 ◽  
Author(s):  
Sivakumar Aswathappa ◽  
Sahaya Jude Dhas Sathiyadhas ◽  
Balachandar Settu ◽  
Martin Britto Dhas Sathiyadhas Amalapushpam
Keyword(s):  
Shock Wave ◽  
Grain Size ◽  
Dielectric Properties ◽  
Shock Waves ◽  
Dihydrogen Phosphate ◽  
Ammonium Dihydrogen Phosphate ◽  
X Ray Diffraction ◽  
Research Article ◽  
Adp Crystal ◽  
Post Shock

Abstract In this research article, the authors pay attention to investigate the effect of structural and dielectric properties of ammonium dihydrogen phosphate (ADP) crystal under pre and post shock loaded conditions. A shock wave of Mach number 1.9 was utilized for the present investigation which was generated by a table-top pressure driven shock tube. The crystalline nature and grain size variations were estimated by powder X-ray diffraction technique. The grain size of post shock wave loaded ADP crystal is found to be larger than that of the pre shock wave loaded ADP crystal. The dielectric properties of the pre and post shock loaded crystals were analyzed by impedance analyzer as a function of frequency (1 kHz–1 MHz) at ambient temperature. The dielectric constant is observed to be varying from 346 to 362 at the frequency of 400 kHz for pre and post shock wave loaded ADP crystals, respectively. The obtained results suggest that shock waves can be an alternate tool to tailor the physical properties of materials without creating any change in the original crystal system and surface morphology.

The study of acoustic scattering from a single sound-permeable sphere

2018 ◽  
Vol 13 (4) ◽  
pp. 79-91 ◽  
Author(s):  
E.Sh. Nasibullaeva
Keyword(s):  
Speed Of Sound ◽  
Numerical Technique ◽  
Acoustic Scattering ◽  
Computer Time ◽  
Physical Parameters ◽  
Fast Method ◽  
Scattering Field ◽  
Permeable Sphere ◽  
Test Verification ◽  
Good Agreement

The paper presents a generalized mathematical model and numerical investigation of the problem of acoustic scattering from a single sound-permeable sphere during the passage of two types of waves - spherical from a monopole radiation source and a plane one. In solving the Helmholtz equation, a numerical technique based on the fast method of multipoles is used, which allows achieving high accuracy of the results obtained at the lowest cost of computer time. The calculations are compared with known experimental data and a good agreement is obtained. The formulas for calculating the main characteristic of the scattering field (the total scattering cross section) for a sound-permeable sphere are generalized. The effect on this characteristic of the physical parameters of media outside and inside the sphere, such as the density and speed of sound, is shown. A numerical parametric analysis of the pressure distribution around a single sound-permeable sphere for different values of the wave radius, density, and speed of sound of the outer and inner medium of the sphere is carried out. The obtained results will later be used for test verification calculations for the numerical solution of the generalized problem of acoustic scattering of a set of sound-permeable spheres (coaxial or arbitrarily located in space).

scholarly journals Thermal ignition of a combustible over an inclined hot plate

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Salaika Parvin ◽  
Nepal Chandra Roy ◽  
Rama Subba Reddy Gorla
Keyword(s):  
Mixed Convection ◽  
Convection Flow ◽  
Physical Parameters ◽  
Thermal Ignition ◽  
Mixed Convection Flow ◽  
Flow Properties ◽  
Continuous Transformation ◽  
Hot Plate ◽  
Ignition Characteristics ◽  
Good Agreement

AbstractIn this study, the ignition characteristics and the flow properties of the mixed convection flow are presented. Detailed formulations of the forced, natural and mixed convection problems have been discussed. In order to avoid inconvenient switch between the forced and natural convection we introduce a continuous transformation in the mixed convection. We make a comparison between these situations which reveal a good agreement. For mixed convection flow, the ignition distance is explicitly expressed as a function of the Prandtl number, reaction parameter and wall temperature. It has been observed that owing to the increase of the aforesaid parameters, the thermal ignition distance is reduced. Numerical results are illustrated for velocity, temperature, and concentration for different physical parameters. Furthermore, the development of combustion is presented by using streamlines, isotherms and isolines of fuel and oxidizer.

scholarly journals Finite Element Analysis of the Microwave Ablation Method for Enhanced Lung Cancer Treatment

Cancers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 3500
Author(s):  
Marija Radmilović-Radjenović ◽  
Martin Sabo ◽  
Marta Prnova ◽  
Lukaš Šoltes ◽  
Branislav Radjenović
Keyword(s):  
Dielectric Properties ◽  
Cancer Cells ◽  
Microwave Ablation ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Surrounding Tissue ◽  
Physical Parameters ◽  
Medical Procedure ◽  
Ablation Zone ◽  
Specific Absorption

Knowledge of the frequency dependence of the dielectric properties of the lung tissues and temperature profiles are essential characteristics associated with the effective performance of microwave ablation. In microwave ablation, the electromagnetic wave propagates into the biological tissue, resulting in energy absorption and providing the destruction of cancer cells without damaging the healthy tissue. As a consequence of the respiratory movement of the lungs, however, the accurate prediction of the microwave ablation zone has become an exceptionally demanding task. For that purpose, numerical modeling remains a primordial tool for carrying out a parametric study, evaluating the importance of the inherent phenomena, and leading to better optimization of the medical procedure. This paper reports on simulation studies on the effect of the breathing process on power dissipation, temperature distribution, the fraction of damage, and the specific absorption rate during microwave ablation. The simulation results obtained from the relative permittivity and conductivity for inflated and deflated lungs are compared with those obtained regardless of respiration. It is shown that differences in the dielectric properties of inflated and deflated lungs significantly affect the time evolution of the temperature and its maximum value, the time, the fraction of damage, and the specific absorption rate. The fraction of damage determined from the degree of tissue injury reveals that the microwave ablation zone is significantly larger under dynamic physical parameters. At the end of expiration, the ablation lesion area is more concentrated around the tip and slot of the antenna, and the backward heating effect is smaller. The diffuse increase in temperature should reach a certain level to destroy cancer cells without damaging the surrounding tissue. The obtained results can be used as a guideline for determining the optimal conditions to improve the overall success of microwave ablation.

scholarly journals Tetragonal–Cubic Phase Transition and Low-Field Dielectric Properties of CH3NH3PbI3 Crystals

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4215
Author(s):  
Roxana E. Patru ◽  
Hamidreza Khassaf ◽  
Iuliana Pasuk ◽  
Mihaela Botea ◽  
Lucian Trupina ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Current Knowledge ◽  
Cubic Phase ◽  
Relaxation Processes ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Low Field ◽  
Conduction Mechanisms ◽  
Temperature Ranges ◽  
Nyquist Plots

The frequency and temperature dependence of dielectric properties of CH3NH3PbI3 (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c. electric field. The study correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes, as well as with the different transport regimes indicated by the Nyquist plots. The different energy barriers revealed by the impedance spectroscopy highlight the dominant transport mechanisms in different frequency and temperature ranges, being associated with the bulk of the grains, their boundaries, and/or the electrodes’ interfaces.

PERMITTIVITY IN PERTURBED MOLECULAR NANOFILMS

2012 ◽  
Vol 26 (15) ◽  
pp. 1250078 ◽  
Author(s):  
BRANKO MARKOSKI ◽  
JOVAN P. ŠETRAJČIĆ ◽  
MIROSLAVA PETREVSKA ◽  
SINIŠA VUČENOVIĆ
Keyword(s):  
Optical Properties ◽  
Dielectric Properties ◽  
Green's Functions ◽  
Green’S Functions ◽  
Microscopic Theory ◽  
2D Systems ◽  
Molecular Films ◽  
Temperature Dependent

A microscopic theory of dielectric properties of thin molecular films, i.e., quasi 2D systems bounded by two surfaces parallel to XY planes was formulated. Harmonic exciton states were calculated using the method of two-time, retarded, temperature dependent Green's functions. It has been shown that two types of excitations can occur: bulk and surface exciton states. Analysis of the optical properties of these crystalline systems for low exciton concentration shows that the permittivity strongly depends on boundary parameters and the thickness of the film. Conditions for the appearance of localized or unoccupied exciton states have been especially analyzed.

Analysis of Tempering and Rehardening for Grinding of Hardened Steels

1991 ◽  
Vol 113 (4) ◽  
pp. 388-394 ◽  
Author(s):  
O. B. Fedoseev ◽  
S. Malkin
Keyword(s):  
Thermal Properties ◽  
Heat Source ◽  
Hardened Steel ◽  
Temperature History ◽  
Hardness Distribution ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Reaction Equations ◽  
Rate Controlling Step ◽  
Good Agreement

An analysis is presented to predict the hardness distribution in the subsurface of hardened steel due to tempering and rehardening associated with high temperatures generated in grinding. The grinding temperatures are modeled with a triangular heat source at the grinding zone and temperature-dependent thermal properties. The temperature history, including the effect of multiple grinding passes, is coupled with thermally activated reaction equations for tempering and for reaustenitization which is the rate controlling step in rehardening. Experimental results from the literature are found to be in good agreement with the analytical predictions.

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