Dynamic phase transitions and dynamic phase diagrams of the Blume–Emery–Griffiths model in an oscillating field: the effective-field theory based on the Glauber-type stochastic dynamics

Using the effective-field theory based on the Glauber-type stochastic dynamics (DEFT), we investigate dynamic phase transitions and dynamic phase diagrams of the Blume–Emery–Griffiths model under an oscillating magnetic field. We presented the dynamic phase diagrams in (T/J, h₀/J), (D/J, T/J) and (K/J, T/J) planes, where T, h₀, D, K and z are the temperature, magnetic field amplitude, crystal–field interaction, biquadratic interaction and the coordination number. The dynamic phase diagrams exhibit several ordered phases, coexistence phase regions and special critical points, as well as re-entrant behavior depending on interaction parameters. We also compare and discuss the results with the results of the same system within the mean-field theory based on the Glauber-type stochastic dynamics and find that some of the dynamic first-order phase lines and special dynamic critical points disappeared in the DEFT calculation.     

Magnetic phase diagrams of Fe–Mn–Al alloy on the Bethe lattice

The magnetic behaviors of the Fe–Mn–Al alloy are simulated on the Bethe lattice by using a trimodal random bilinear exchange interaction(J) distribution in the Blume–Capel(BC) model. Ferromagnetic(J 0) or antiferromagnetic(J 0)bonds or dilution of the bonds(J = 0) are assumed between the atoms with some probabilities. It is found that the secondor the first-order phase boundaries separate the ferromagnetic(F), antiferromagnetic(AF), paramagnetic(P), or spin-glass(SG) phases from the possible other one. In addition to the tricritical points, the special points at which the second- and the first-order and the spin-glass phase lines meet are also found. Very rich phase diagrams in agreement with the literature are obtained.     

A polynomial hybrid reflection model and measurement of its parameters based on images of sample

Reflectance model is a basic concept in computer vision.Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance.But the ratio of diffuse and specular reflection decided manually has no clear meaning. We propose a new polynomial hybrid reflectance model.The reflectance map equation with a known shape (for example cylinder)as a sample is used to estimate parameters of the proposed reflectance model by least square regression algorithm.Then the reflectance parameters for surfaces of the same class of materials can be determined.Experiments are performed for a metal surface.The synthesis images produced by the proposed method and existing ones are compared with the real acquired image,and the results show that the proposed reflectance model is suitable for describing real reflectance.     

A hybrid strategy for cryptanalysis of optical encryption based on double-random phase–amplitude encoding

A hybrid two-step attack scheme that combines the chosen-plaintext attack (CPA) and the known-plaintext attack (KPA) algorithms is proposed to acquire the secret keys of the optical cryptosystem based on double-random phase–amplitude encoding (DRPAE) technique. By implementing our presented attack, an opponent can obtain not only the estimated solutions of the two random phase keys but also the accurate solution of the amplitude modulator (AM), which is introduced to the encryption process and regarded as an additional key to enhance the security level of the DRPAE-based cryptosystem. The validity and effectiveness of this attack strategy is analyzed theoretically and then verified by computer simulations.     

A study on improving anti-interference capability of inversion method reconstructing layered sea bottom parameters

The remote measurement of the vertical distribution of acousticalparameters of the sea bottom is an inverse method in acoustics.The existingmethods can be divided into two types:the wave method and the raymethod.The former usually does not apply to cases with discontinuity inacoustical parameter profiles,whereas the latter usually ignores the contribu-tions made by multiple reflections,resulting in the appearance of pseudo inter-faces.However,under certain practical circumstances,the ray method canproduce satisfactory results.In this paper,at first we use the conception ofequitime layer thickness to obtain the pulse response iteration method.Theanti-interference capability of this method is poor.In order to improve this ca-pability,we develope the sample iteration method and the sample-averagingiteration method.The sample-averaging iteration method introduces a way ofstatistical averaging,which can further improve the anti-interference capability.     

Hydrostaticity and hidden order: effects of experimental conditions on the temperature–pressure phase diagram of URu2Si2

The pressure dependence of the hidden order phase transition of URu₂Si₂ is shown to depend sensitively upon the quality of hydrostatic pressure conditions during electrical resistivity measurements. Hysteresis in pressure is demonstrated for two choices of pressure medium: the commonly used mixture of 1:1 Fluorinert FC70/FC77 and pure FC75. In contrast, no hysteresis is observed when the pressure medium is a 1:1 mixture of n-pentane/isoamyl alcohol, as it remains hydrostatic over the entire studied pressure range. Possible ramifications for the interpretation of the temperature–pressure phase diagram of URu₂Si₂ are discussed.     

Kondo entropy of δ-phase plutonium and its impact on Pu alloy phase diagrams

We present a new analysis of the heat capacity of δ-phase Pu-5 at.% Al with a fit using a single-ion Kondo term and a low-temperature Schottky anomaly in addition to the Debye and linear terms. The Kondo and Schottky terms together contribute 1.2 R to the entropy at 300?K. We show how the extra entropy could affect the alloy phase diagrams of δ-phase Pu.     

Effect of solid-state characteristics on the critical parameters of the vapor–liquid phase transition

Database for the critical point parameters of almost all metals (including transition metals) and semiconductors is used to derive a number of empirical expressions to relate these parameters to the heat of evaporation, the normal density, and the isothermal bulk modulus of these substances in a solid state under normal conditions. The database is obtained using the thermodynamic model proposed earlier.     

Memristance controlling approach based on modification of linear M–q curve

The memristor has broad application prospects in many fields, while in many cases, those fields require accurate impedance control. The nonlinear model is of great importance for realizing memristance control accurately, but the im- plementing complexity caused by iteration has limited the actual application of this model. Considering the approximate linear characteristics at the middle region of the memristance-charge （M-q） curve of the nonlinear model, this paper pro- poses a memristance controlling approach, which is achieved by linearizing the middle region of the M-q curve of the nonlinear memristor, and establishes the linear relationship between memristances M and input excitations so that it can realize impedance control precisely by only adjusting input signals briefly. First, it analyzes the feasibility for linearizing the middle part of the M-q curve of the memristor with a nonlinear model from the qualitative perspective. Then, the lin- earization equations of the middle region of the M-q curve is constructed by using the shift method, and under a sinusoidal excitation case, the analytical relation between the memristance M and the charge time t is derived through the Taylor series expansions. At last, the performance of the proposed approach is demonstrated, including the linearizing capability for the middle part of the M-q curve of the nonlinear model memristor, the controlling ability for memristance M, and the influence of input excitation on linearization errors.     

Dependence of the form of a phase shifter’s phase–temporal characteristics on the parameters of ferrite spinels and the means of their fabrication

On the basis of experimental results, it is shown that the form of a phase shifter’s phase–temporal characteristics when working with waves of linear polarization in the 8 mm range can deviate substantially from linear and be unstable in the range of operating temperatures at the similar parameters of ferrites with critical saturation magnetic moments but certain differences in the manufacturing process.     

A selective and sensitive tert-butylhydroquinone sensor based on synergy of CTAB and AuNPs–PVP–graphene nanohybrids

Gold nanoparticles (AuNPs)–polyvinylpyrrolidone (PVP)–graphene (Gr) nanohybrids were prepared by a facile one-pot green strategy. The obtained Au–PVP–Gr composites were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Then, a novel electrochemical sensor for highly sensitive and selective detection of tert-butylhydroquinone (TBHQ) is proposed based on cetyltrimethyl-ammonium bromide (CTAB) and Au–PVP–Gr modified glassy carbon electrode (GCE). Due to the synergistic effect of CTAB and Au–PVP–Gr, the developed sensor displays a wide linear range from 0.02 to 0.1 and 0.1 to 100.0 μM. A low detection limit of 0.009 μM was observed. Further, the sensitivity and selectivity of PVP–CTAB/Au–PVP–Gr/GCE was demonstrated by its practical application in the determination of TBHQ in real samples.     

North-South asymmetry of some solar parameters: A study based on the dominance of hemispheric sunspot activity during the solar cycles 18–24

Solar activity indices differ over the solar disk, and different activity parameters are not considered to be symmetric between the northern and southern solar hemispheres. In the present paper, the daily data of a set of solar parameters (solar radio flux F10.7, total solar irradiance TSI, plage area PA, coronal index CI, solar flare index SFI, and solar mean magnetic field ǀBǀ) as well as the daily hemispheric sunspot areas (SSAs) and sunspot numbers (SSNs) during a timeframe 1945–2017 (covering almost the last seven solar cycles, 18 ̶ 24) have been employed to investigate the north-south (N-S) asymmetry of the considered solar parameters based on the dominance of hemispheric distributions of SSAs and SSNs. The N-S asymmetry for each solar parameter has been investigated and the results revealed that it is a significant aspect through different years in the entire period. The grand average of each solar parameter for the northern and southern groups over each solar activity cycle has been calculated to investigate the statistical significance of N-S asymmetry of each solar parameter in each solar activity cycle. The solar cycles 19 and 24 displayed the dominance of the southern F10.7 and PA over the northern one. However, the solar cycle 23 showed the reverse. The grand average of CI displayed the southern preference in the solar cycle 19 while, the northern dominance of CI is revealed for the solar cycle 23. The grand averages of CI demonstrated nearly symmetric distribution in solar cycles 18, and 20–22. The N-S asymmetry of the grand averages of SFI exhibited a southern dominance during solar cycles 21 and 24. On the other hand, the northern preference is observed for the grand average of SFI through the solar cycle 23. The asymmetry of the grand averages of ǀBǀ obviously has the same dominance (sign) of hemispheric sunspot activity indices for the solar cycles 21–24. The periodic behavior of the N-S asymmetry of SSAs, SSNs, F10.7, and ǀBǀ has been investigated using Fast Fourier Transformation. Many mid- and long term periodicities have been detected. We present our results and discuss their possible explanations.     

Three-class classification models of logS and logP derived by using GA–CG–SVM approach

In this investigation, three-class classification models of aqueous solubility (logS) and lipophilicity (logP) have been developed by using a support vector machine (SVM) method combined with a genetic algorithm (GA) for feature selection and a conjugate gradient method (CG) for parameter optimization. A 5-fold cross-validation and an independent test set method were used to evaluate the SVM classification models. For logS, the overall prediction accuracy is 87.1% for training set and 90.0% for test set. For logP, the overall prediction accuracy is 81.0% for training set and 82.0% for test set. In general, for both logS and logP, the prediction accuracies of three-class models are slightly lower by several percent than those of two-class models. A comparison between the performance of GA–CG–SVM models and that of GA–SVM models shows that the SVM parameter optimization has a significant impact on the quality of SVM classification model. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Hui Zhang and Ming-Li Xiang are contributed equally.     

Effects of current density on electropulsing-induced phase transformations in a Zn–Al based alloy

Phase transformations of an electropulsing-treated ZA22 alloy were studied after tensile deformation by using scanning electron microscopy and transmission electron microscopy. It was found that electropulsing tremendously accelerated phase transformations consequentially in the two stages: (a) quenching from supersaturated state approaching the final stable state, i.e., α+ε→T′+η, and (b) up-quenching from the final stable state to a higher temperature state, i.e., T′+η→α+ε. The mechanism of electropulsing-induced phase transformation is discussed from the point of view of Gibbs free energy, and electropulsing kinetics.     

A comparative study of conventional type II and inverted core–shell nanostructures based on CdSe and ZnS

The objective of this work is to investigate structural, morphological and optical properties of conventional CdSe/ZnS core–shell and inverted ZnS/CdSe core–shell nanostructures for opto-electronic device applications. For this purpose both nanostructures were synthesized using chemical bath deposition technique in thin film form. The structural properties were studied using X-ray diffraction technique with Rietveld refinement and transmission electron microscopy (TEM). The surface morphology of synthesized thin film was illustrated in the form 2D and 3D images using atomic force microscopy (AFM). The optical properties were explained using UV–Vis absorption spectroscopy and photo luminescence (PL) spectroscopy in in situ monitoring process. A comparison of estimated particle size from XRD, high resolution AFM and TEM images was resulted in good agreement as 2.1, 2.4 and 2.1 nm respectively for conventional CdSe/ZnS core–shell and as 2.5, 2.5 and 2.2 nm respectively for inverted ZnS/CdSe core–shell nanostructures.     

Development of the device prototype based on the semiconductor–carbon nanotubes structure for optical radiation detection and study of its parameters

A light-receiving device prototype based on the semiconductor–carbon nanotubes (CNTs) structure consisting of 16 cellular structured sensitive elements grown on the same substrate is developed. The topology of sensitive cells represents holes through metallization and insulator layers to the semiconductor from which the CNT array grows to the top metallization layer. The device prototype parameters are determined as follows: the effective wavelength range is within 400–1100 nm, the operational speed is no longer than 30 μs, the coefficients of peak sensitivity reached at wavelengths of 640 and 950 nm are 197 and 193 μA/W, respectively.     

Molecular simulation of binary phase diagrams from the osmotic equilibrium method: vapour pressure and activity in water–ethanol mixtures

ABSTRACT

Herein, an approach for simulating phase diagrams of binary mixtures is presented, where a bulk liquid and its corresponding vapour phase are simulated by means of molecular dynamics using explicit polarisation. Time-averaged density profiles for the pure compounds and mixtures at different mole fractions provide information about the spatial distribution in the bulk liquid and the amount of evaporated species in the adjacent vapour phase. The activities in the liquid phase are calculated from the mean vapour phase densities at a given composition, providing a good qualitative agreement compared to experimental data and the precision of the method follows a previously developed Poisson model of evaporation. With the Redlich–Kister approach for the activities in a binary mixture, the directly obtained activities are fitted providing corrected activity coefficients of the two species. This method is applied to ethanol water mixtures at different mole fractions. The obtained structural data are in good agreement with experimental data and time-averaged density profiles provide a detailed insight into the composition of the liquid–vapour interface. An azeotropic point is obtained for an excess concentration of ethanol at 87% as percentage by mass compared to the experimental value of 95%.