Phase Entropy Research Articles

Refrigeration in 2D: Electrostaticaloric effect in monolayer materials

As electrical device components are scaled down to atomic sizes, management of waste heat becomes a major issue in device performance. Minimizing energy consumption of electrical components and waste heat generation are critical issues in the operation of such devices. Interest in alternative cooling mechanisms, such as those provided by electrocaloric, magnetocaloric, elastocaloric, and thermoelectric materials, may also be necessary in mitigating issues associated with waste heat generation. In this work, we provide theoretical predictions for an alternative cooling mechanism, accomplished by utilizing electrostatic gating to induce structural phase transitions in monolayer materials. We refer to this mechanism as the electrostaticaloric effect in reference to the mechanism of electrostatic doping that drives the structural phase transformation and entropy change in the material. Recent predictions and experimental observation that electrostatic gating can induce structural phase transformations in monolayer materials opens the possibility for new application areas. Here, we explore the potential for electrostatically induced structural phase transformations in monolayer ${\mathrm{MoTe}}_{2}$ to be used in a Carnot refrigeration cycle. We predict that a temperature change of 10--15 K may be possible in devices that utilize monolayer ${\mathrm{MoTe}}_{2}$ as the active phase change material. This mechanism may prove useful for future electrical devices which require cooling at the component level, and for which small monolayer devices are necessary.

Entropy budget and coherent structures associated with a spectral closure model of turbulence

We ‘derive’ the eddy-damped quasi-normal Markovian model (EDQNM) by a method that replaces the exact equation for the Fourier phases with a solvable stochastic model, and we analyse the entropy budget of the EDQNM. We show that a quantity that appears in the probability distribution of the phases may be interpreted as the rate at which entropy is transferred from the Fourier phases to the Fourier amplitudes. In this interpretation, the decrease in phase entropy is associated with the formation of structures in the flow, and the increase of amplitude entropy is associated with the spreading of the energy spectrum in wavenumber space. We use Monte Carlo methods to sample the probability distribution of the phases predicted by our theory. This distribution contains a single adjustable parameter that corresponds to the triad correlation time in the EDQNM. Flow structures form as the triad correlation time becomes very large, but the structures take the form of vorticity quadrupoles that do not resemble the monopoles and dipoles that are actually observed.

Prognostic Value of Early Evaluation of Left Ventricular Dyssynchrony After Myocardial Infarction.

Dispersion in the contraction of the normally coordinate ventricular system, referred to as left ventricular (LV) dyssynchrony, is constantly observed at different grades of severity after myocardial infarction (MI). We aimed to investigate the prognostic value of early dyssynchrony in adverse cardiac events after MI in a rat model using the quantified gated single photon emission tomography (SPECT; QGS) software. After thoracotomy, the left coronary arteries of 16 rats were occluded and reperfused. SPECT was performed with [99m Tc]methoxyisobutylisonitrile 3days, 1week, 2weeks, 4weeks, and 8weeks after MI. The phase analysis parameters including mean phase standard deviation (PSD), bandwidth (BW), entropy, and LV function were analyzed by the QGS software. A receiver operating characteristic curve was used to explore the predictors for cardiac death and severe cardiac failure (ejection fraction [EF] < 35%). A Kaplan-Meier event-free survival analysis, univariate, and multivariate Cox proportional hazards regression analyses were conducted. Four rats had died, whereas another four rats presented with severe heart failure. LV end-diastolic volume was increased during follow-up, but no significant changes were noted in the other parameters. The prognosis of rats with lower EF and higher end-diastolic and end-systolic volumes (ESV), PSD, BW, and entropy at 3days after MI was poor. Adverse cardiac events were associated with lower EF (relative risk [RR] 13.1, 95% confidence Interval [CI]: 2.1-259.9, P = 0.003), higher ESV (RR 6.4, CI 1.4-45.9, P = 0.01), and higher entropy (RR 4.3, 95% CI: 1.0-21.8, P = 0.04) by univariate analysis. Multivariate analysis showed that lower EF was the most powerful independent predictor of adverse cardiac events (RR 16.0, CI 1.1-429.2, P = 0.03). Severe early dyssynchrony evaluated by QGS after MI could predict cardiac events in the rat model in the same way as other cardiac function parameters including EF and ESV. The early assessment of dyssynchrony after MI may provide helpful information for the prediction of cardiac events in the future.

Fundamental understanding of mechanical behavior of high-entropy alloys at low temperatures: A review

Abstract

Energetics of point defects in rocksalt structure transition metal nitrides: Thermodynamic reasons for deviations from stoichiometry

First principle calculations of point defect formation energies in group 3–6 transition metal (Me) nitrides MeNx are employed to explain the thermodynamic reasons for the large reported compositional range (typically x = 0.7–1.3) in the rocksalt structure. Both under-stoichiometric (x < 1) and over-stoichiometric (x > 1) compositions are due to relatively low vacancy formation energies that decrease from an average of 2.7 and 4.5 eV for nitrogen and cation vacancies in group 3 nitrides (ScN, YN, LaN) to −1.8 and −0.8 eV in group 6 nitrides (CrN, MoN, WN), indicating that they become thermodynamically stable at zero temperature for group 6 and for group 4–6 nitrides, respectively. Similarly, nitrogen and cation interstitials in tetragonal and 111- or 110-split configurations are unstable for groups 3–5 but become thermodynamically stable for group 6 nitrides, consistent with the mechanical instability of the latter compounds. All antisite defects possess high formation energies and are unlikely to form. The nitrogen chemical potential at finite temperatures and in equilibrium with a N2 gas is strongly affected by the vapor phase entropy, leading to shifts in the defect free energy of, for example, 1.2 eV at 1 Pa N2 at 800 K, causing an increasing likelihood for nitrogen vacancies and cation interstitials at elevated temperatures. In addition, the configurational entropy of point defects causes a correction of e.g. 0.4 eV for a 1% vacancy defect concentration at 800 K. Considering these entropy contributions leads to predicted temperature windows for stoichiometry of e.g. 200–1100 K for TiN, 500–1400 K for ZrN, and 1200–1400 K for HfN, while considerable cation and nitrogen vacancy concentrations are expected for temperatures below and above these ranges, respectively. Schottky pair defects are predicted in VN for T > 200 K and in NbN, TaN, and group 6 nitrides at all temperatures, independent of the N2 partial pressure. The overall results show that thermodynamic arguments (even in the absence of kinetic barriers) can explain many of the reported composition vs temperature and pressure relationships in rocksalt structure nitrides.

Production of CoAl and CoAlCr FSMAs and determination of their thermal, microstructure, and magnetic properties

In this study, some thermal, mechanical, and magnetic properties of Co86Al14 and Co82Al14Cr4 (at.%) alloys have been investigated. The alloys were produced by arc melting method, and their thermal properties such as phase transformation temperature, enthalpy, and entropy were measured using differential scanning calorimetry (DSC). In addition, TG/DTA device has been utilized for determining Curie temperature for each sample. Furthermore, to specify crystal structure and microstructure of specimens, XRD and optical microscope techniques were used. In addition, Vickers hardness test as a mechanical property has been accomplished to compare the effect of Cr addition to CoAl-based shape memory alloy. Finally, at room temperature, physical property measurement system has been used to reveal magnetization of SMAs. The transformation temperatures obtained from DSC measurement at a heating rate of 20 °C min−1 for Co86Al14 (at.%) alloy were As = 235.3 °C, Af = 293.4 °C, Ms = 105.1 °C, and Mf = 56.9 °C, while the same measurements for Co82Al14Cr4 (at.%) alloy gave As = 295.1 °C, Af = 333.4 °C, Ms = 166.5 °C, and Mf = 136.6 °C, which showed a significant increase due to the incorporation of (4 at.%) of Cr. In contrast, the quantitative values of each enthalpy and entropy were diminished. Moreover, magnetization saturation values for the CoAl and CoAlCr shape memory alloys were determined by H–M measurements to be 127.23 and 107.06 emu g−1, respectively, and their Curie temperature (TC) were 716.71 and 686.22 °C, respectively. What is more, Vickers hardness values for the CoAl and CoAlCr alloys were measured to be 203.40 and 239.22 HV, respectively. Thus, the microhardness value increased remarkably for adding (4 at.%) of chromium to CoAl-based SMA.

Bispectral Analysis to Enhance Oximetry as a Simplified Alternative for Pediatric Sleep Apnea Diagnosis.

This study aims at assessing the bispectral analysis of blood oxygen saturation (SpO2) from nocturnal oximetry to help in pediatric sleep apnea-hypopnea syndrome (SAHS) diagnosis. Recent studies have found excessive redundancy in the SAHS-related information usually extracted from SpO2, while proposing only two features as a reduced set to be used. On the other hand, it has been suggested that SpO2 bispectral analysis is able to provide complementary information to common anthropometric, spectral, and clinical variables. We address these novel findings to assess whether bispectrum provides new non-redundant information to help in SAHS diagnosis. Thus, we use 981 pediatric SpO2 recordings to extract both the reduced set of features recently proposed as well as 9 bispectral features. Then, a feature selection method based on the fast correlationbased filter and bootstrapping is used to assess redundancy among all the features. Finally, the non-redundant ones are used to train a Bayesian multi-layer perceptron neural network (BYMLP) that estimate the apnea-hypopnea index (AHI), which is the diagnostic reference variable. Bispectral phase entropy was found complementary to the two previously recommended features and a BY-MLP model trained with the three of them reached high agreement with actual AHI (intra-class correlation coefficient = 0.889). Estimated AHI also showed high diagnostic ability, reaching 82.1%, 81.9%, and 90.3% accuracies and 0.814, 0.880, and 0.922 area under the receiver-operating characteristics curve for three common AHI thresholds: 1 e/h, 5 e/h, and 10 e/h, respectively. These results suggest that the information extracted from the bispectrum of SpO2 can improve the diagnostic performance of the oximetry test.

ASSESSMENT OF CARDIAC HEART FAILURE AND CARDIAC ARTERY DISEASE BY THE HIGHER ORDER SPECTRA

Cardiac diseases are major reason of death in the world populace and the numeral of cases is upsurging every year. Due to cardiac artery disease (CAD), the strength of heart muscles becomes weak and heart pumping is disturbed which may eventually lead to abnormal heart beat and heart failure. Therefore, the beginning stage detection of CAD and cardiac heart failure (CHF) are of prime importance. In this work, we have used a non-invasive diagnosis method as higher order spectra (HOS) for assessment of cardiac diseases. The method indicates whether or not a cardiac heart disease is present, by assessing the cardiac health of subjects using extracted features from heart rate variability (HRV) signals. This assessment is based on 10 spectra nonlinear features. These features were extracted from HRV signals by using the HOS method. For this study, the R-R interval data (i.e. HRV signals) were taken from the standard database of cardiac heart failure (CHF), CAD patients, healthy young (YNG) and Self recorded of healthy young (SELF_YNG) subjects. Statistical assessments were performed on the group of database sets as YNG-CAD, YNG-CHF, SELF_YNG-CAD and Self_YNG-CHF subjects. A Wilcoxon rank sum test ([Formula: see text]-value) was used to statistically compare the features extracted by HOS for group of data sets. It indicates whether or not the same features of individual classes of HRV data sets are dissimilar. The results depicted that the all features are very significant ([Formula: see text]) except the phase entropy (PHE) feature which is not significant for CAD-CHF, SELF_YNG-CAD and SELF_YNG-CHF group of subjects. While in the case of YNG-CAD group of subjects, features like first-order spectral moment of amplitudes of diagonal elements (H3), PHE and logarithmic amplitudes of diagonal elements (H2) are significant ([Formula: see text]) and excluding these features, the remaining features are very significant except MM and H1 which are not significant. The results also depicted that the mean value of sum of logarithmic amplitude (H1), H2, normalized entropy (P1), normalized squared entropy (P2) and PHE features of healthy YNG subjects are having higher values than that of CAD and CHF patients. While weighted center of bi-spectrum (WCOB2) and FLAT spectrum features are lower than CAD and CHF patients compared to YNG subjects. In case of CAD and CHF patients, all the features of CAD patients are having higher values compared to CHF except P1, P2 and WCOB1.

Calculation of Entropy of Adsorption for Small Molecules on Mineral Surfaces

We performed density functional theory calculations for small organic molecules adsorbed on calcite, quartz, and kaolinite mineral surfaces and calculated the entropy change as a result of adsorption. Our results demonstrate that the entropy contribution to the free energy is mainly independent of the mechanism of binding, but it is affected by surface coverage, molecule size, character, and degrees of freedom. Compared with experimental results for weakly bonded molecules, density functional theory calculations predict a higher loss of entropy as a result of adsorption, which can be used as the upper limit for estimating the entropy contribution for adsorption to a mineral surface. The study has demonstrated a linear relationship between the entropy of the adsorbed molecule and the gas phase entropy, which can be used to estimate the entropy contribution to the free energy of adsorption on minerals without explicit density functional theory calculations, which is an important step forward in predicting t...

Investigating the entropy generation in condensing steam flow in turbine blades with volumetric heating

In the last stages of steam turbines, the existence of the liquid phase results in wetness losses. This study intends to analyze the effect of volumetric heating on condensing steam flow in the stationary cascade of turbine blades and the losses associated with wetness. Numerical simulation of a turbulent flow of wet steam in the cascade of turbine blades was conducted based on two phase Eulerian-Eulerian description and SST k - ω turbulence model. Numerical solution results show a consistency with experimental data in the adiabatic cases. An agreement was also shown between the numerical solution and analytical solution results in the presence of heat transfer. The numerical results proposed that by applying volumetric heating to the convergent section, the wetness fraction in the cascade of turbine blades can be reduced which prevent corrosion losses. As volumetric heating is increased to 2.0 × 105(kWm2), the entropy generation is ascending; while as the liquid phase disappears and the entropy generated from the liquid is eliminated at 3.55 × 105(kWm2), the entropy generation shows a descending trend which ascends again by increasing volumetric heating. Hence, applying an appropriate volumetric heating can prevent the corrosion associated with the liquid phase and control total entropy generation.

Comparison of Left Ventricular Phase Parameters Analysis between Two Software Programs in Patients with Normal Gated Single-photon Emission Computed Tomography-Myocardial Perfusion Imaging.

Background:Phase analysis can be easily performed by different software to assess the left ventricular dyssynchrony from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) with high precision. However, the normal values of histogram bandwidth (HBW) and phase standard deviation (PSD) and their comparison using different programs have not been fully elucidated and actively being evaluated at present. The aim of this study was to determine the phase analysis parameters values and to compare the phase indices of two commonly used programs in a group of patients with normal gated SPECT-MPI.Methods:Phase parameters were retrospectively evaluated in 138 consecutive nondiabetic patients having a normal gated SPECT-MPI using the quantitative gated SPECT (QGS) and Emory Cardiac Toolbox (ECTb) software. HBW, PSD, and phase entropy were calculated separately using both programs.Results:The fair correlation between software programs was observed. HBW and PSD in QGS and ECTb were 26.20 ± 9.7 and 25.46 ± 8.0 (r-value. 56, SEE 6.65) and 6.64 ± 2.5 and 7.65 ± 2.5 (r = 0.54, SEE 2.14), respectively. The value of phase entropy in QGS program was 45.08 ± 6.3. A fair correlation between phase entropy and PSD in QGS was observed (r = 0.44, 95% confidence interval-0.29–0.56).Conclusion:Phase analysis parameters derived from gated SPECT-MPI in patients with normal myocardial perfusion are program dependent and may differ. The results cannot be interchangeably used in the same patients.

Outlier Detection using Weighted Holoentropy with Hyperbolic Tangent Function

Numerous research works has been carried out in the literature to detect the outlier's a.k.a anomalies. Outlier detection is considered as a pre-processing step for locating those objects in a dataset that do not conform to well-defined notions of expected behaviour. In the proposed method, logistic sigmoid function related to hyperbolic tangent will be used as weightage function for finding the outlier data point(s). It can distribute the outlier data points effectively as compared with the reverse sigmoid function. The method is implemented with four phases. In the first phase, data is read out and dynamic entropy is calculated. In the second phase, probability and dynamic entropy computations using logistic sigmoid function related to hyperbolic tangent are performed. In the third phase, dynamic entropies are sorted and top N point is selected as outlier data point(s) and finally, the accuracy for correct outliers is computed for the proposed method.

Electroweak phase transition and entropy release in the early universe

It is shown that the vacuum-like energy of the Higgs potential at non-zero temperatures leads, in the course of the cosmological expansion, to a small but non-negligible rise of the entropy density in the comoving volume. This increase is calculated in the frameworks of the minimal standard model. The result can have a noticeable effect on the outcome of baryo-through-leptogenesis.

Outlier detection using weighted holoentropy with hyperbolic tangent function

Numerous research works has been carried out in the literature to detect the outlier's a.k.a anomalies. Outlier detection is considered as a pre-processing step for locating those objects in a dataset that do not conform to well-defined notions of expected behaviour. In the proposed method, logistic sigmoid function related to hyperbolic tangent will be used as weightage function for finding the outlier data point(s). It can distribute the outlier data points effectively as compared with the reverse sigmoid function. The method is implemented with four phases. In the first phase, data is read out and dynamic entropy is calculated. In the second phase, probability and dynamic entropy computations using logistic sigmoid function related to hyperbolic tangent are performed. In the third phase, dynamic entropies are sorted and top N point is selected as outlier data point(s) and finally, the accuracy for correct outliers is computed for the proposed method.

Entropy generation in flow with silver and copper nanoparticles

The purpose of this attempt is mainly to explore the mixed convective flow of viscous fluid by a rotating disk. Thermal radiation, Joule heating, variable thickness and viscous dissipation have been accounted. Flow under consideration is because of nonlinear stretching characteristics of disk. Water is treated as traditional fluid while nanoparticles include silver and copper. Fluid is electrically conducting subject to applied magnetic field with constant strength. Heat generation and absorption is neglected. An entropy generation analysis is utilized through second law of thermodynamics. The effects of silver and copper nanoparticles on the thermal conductivity of continuous phase fluid and entropy generation have been also examined. Total entropy generation rate is scrutinized for different involved variables. Nonlinear formulation based upon conservation laws of mass, momentum and energy is made. Attention is particularly given to the convergence in the computational process. Velocity and thermal gradients at the surface of disk are obtained in tabular forms. Main conclusions have been indicated.

Temperature-dependent Henry's Law constants of 4-alkyl branched-chain fatty acids and 3-methylindole in an oil-air matrix and analysis of volatiles in lamb fat using selected ion flow tube mass spectrometry.

4-Alkyl branched-chain fatty acids and 3-methylindole are characteristic flavor compounds associated with sheep meat. Determining their partitioning behavior between the gas and condensed phase and ultimately developing a correlation between the compound's headspace concentration and sensory descriptive grouping are important for high-throughput characterization and grading classification. The headspace concentrations of 3-methylindole, 4-methyloctanoic acid, 4-ethyl-octanoic acid, and 4-methylnonanoic acid above corn-oil-based standard solutions and lamb fat samples were measured using selected ion flow tube-mass spectrometry (SIFT-MS). The standard solutions were equilibrated at 80, 100, 110 and 125°C while the fat samples were equilibrated at 125°C. Statistical evaluation, linear and polynomial regression analyses were performed to establish the compound-specific and temperature-dependent Henry's Law constants, enthalpy (ΔH) and entropy (ΔS) of phase changes. The Henry's Law constants (kHcp ) were calculated from the regression analysis with a high degree of confidence (p<0.05) and linearity (r2 >0.99). The kHcp increased with increase in equilibrium temperature. The empirical calculation of ΔH and ΔS at different temperatures confirmed the temperature-dependence of the Henry's Law constants. The headspace concentrations of the lamb-flavor compounds were determined above actual lamb fat samples and the corresponding condensed-phase concentrations were successfully derived. The temperature-dependent Henry's Law constants, ΔH, and ΔS of phase changes for 3-methylindole, 4-methyloctanoic acid, 4-ethyloctanoic acid, and 4-methylnonanoic acid in an air-oil matrix were empirically derived. The effectiveness of SIFT-MS for the direct, real-time, and rapid determination of key flavor compounds in lamb fat samples was established.

Acceleration from short-duration blast

The blast-induced motion of spheres has been studied experimentally where the shock wave is rapidly decaying during the period that quasi-steady acceleration would be developed in the case of a step-function shock wave as considered in most shock-tube studies. The motion of sphere models ranging from 39 to 251 mm in diameter and having a range of densities was assessed using the “free-flight” method in a simulator specially designed to replicate the decaying shock wave profile of spherical blast including negative phase and positive entropy gradient. A standardized blast-wave simulation of 125 kPa and 6-ms positive-phase duration was applied for all experiments. In all cases, there are three phases to the motion: a relatively low “kickoff” velocity from the shock diffraction, acceleration or deceleration during the positive duration, then deceleration through the negative phase and subsequent quiescent air. The unexpected deceleration of larger spheres after their kickoff velocity during the decaying yet high-speed flow of the blast wave seems associated with the persistence of a ring vortex on the downstream side of the sphere. The flow is entirely unsteady with initial forces dominated by the shock diffraction; therefore, the early motion of spheres under such conditions is not governed by quasi-steady drag as in classical aerodynamics. The work will help establish scaling rules for model studies of blast-induced motion relevant to improvised explosive devices, and preliminary results are shown for motion imparted to a human skull surrogate.

Precision-Dependent Changes in Motor Variability During Sustained Bimanual Reaching.

Movement variability of the upper limb was investigated using a bimanual Fitts' task. Participants tapped rhythmically between target-pairs of different index of difficulties for three intervals of 20min each. We studied the effects of index of difficulties and time-on-task on movement time, end-point variability, approximate entropy, and standard deviation of the relative phase. Lower index of difficulties and time-on-task caused decreasing movement time and increasing end-point variability. Moreover, standard deviation of the relative phase and approximate entropy moderately increased. By looking into the long-term effects of a sustained bimanual Fitts' task, this is the first time such movement variability increase is demonstrated in multiple variability indices. The relevance of the findings for future studies on work-related musculoskeletal disorders is being discussed.

Quantum Information Measures and Their Use in Chemistry

Background: The resultant measures of the information content in molecular electronic states are revisited. In these overall measures the current-related terms complement the probability functionals of classical Information Theory. The nonclassical Shannon entropy reflects the average magnitude of the state phase distribution, while the related current term in the complementary Fisher measure accounts for the average phase-gradient. Method: These generalized Fisher and Shannon descriptors of the information content in complex electronic states are applied to determine the phase-equilibria in molecules. The vertical and horizontal equilibria in molecules, which mark the extrema of the nonclassical and resultant entropy/information descriptors, respectively, are explored. The requirement, that the resultant measures have common solutions of the associated extreme entropy/information principles, calls for the negative sign of the nonclassical gradient measure. Conclusion: These extrema imply the phase-transformation of molecular electronic states. A separation of the density (modulus) and current (phase) factors in many-electron states is effected using the Harriman-Zumbach-Maschke construction of complex antisymmetric states yielding the specified electron density. A combined description of molecular systems, which accounts for the density and current degrees-of-freedom of electronic states is summarized and continuity equations for the state phase and resultant entropy are discussed. Keywords: Continuity equations, current-information, information continuity, molecular equilibria, phase-entropy/information, entropy.

Application of CT texture analysis in predicting histopathological characteristics of gastric cancers.

To explore the application of computed tomography (CT) texture analysis in predicting histopathological features of gastric cancers. Preoperative contrast-enhanced CT images and postoperative histopathological features of 107 patients (82 men, 25 women) with gastric cancers were retrospectively reviewed. CT texture analysis generated: (1) mean attenuation, (2) standard deviation, (3) max frequency, (4) mode, (5) minimum attenuation, (6) maximum attenuation, (7) the fifth, 10th, 25th, 50th, 75th and 90th percentiles, and (8) entropy. Correlations between CT texture parameters and histopathological features were analysed. Mean attenuation, maximum attenuation, all percentiles and mode derived from portal venous CT images correlated significantly with differentiation degree and Lauren classification of gastric cancers (r, -0.231 ~ -0.324, 0.228 ~ 0.321, respectively). Standard deviation and entropy derived from arterial CT images also correlated significantly with Lauren classification of gastric cancers (r = -0.265, -0.222, respectively). In arterial phase analysis, standard deviation and entropy were significantly lower in gastric cancers with than those without vascular invasion; however, minimum attenuation was significantly higher in gastric cancers with than those without vascular invasion. CT texture analysis held great potential in predicting differentiation degree, Lauren classification and vascular invasion status of gastric cancers. • CT texture analysis is noninvasive and effective for gastric cancer. • Portal venous CT images correlated significantly with differentiation degree and Lauren classification. • Standard deviation, entropy and minimum attenuation in arterial phase reflect vascular invasion.