Reduced reference image quality assessment using regularity of phase congruency

In this paper, a reduced-reference image quality assessment metric is proposed, which measures the difference of the regularity of the phase congruency (PC) between the reference image and the distorted image. The proposed model adopts a three-stage approach. The PC of the image is first extracted, then the fractal dimensions are computed on PC as the image features that characterize the image structures from the view of the spatial distribution. Finally the image features are pooled as the quality score using ℓ₁ distance. The proposed approach is evaluated on seven public benchmark databases. Experimental results have demonstrated the excellent performance of the proposed approach.     

Effect of Ag photo-doping on structural,optical and phase change properties of GeTe chalcogenide films

This paper reports the effect of Ag photo-doping on optical, electrical and structural properties of GeTe:Ag thin films. The absence of sharp diffraction peak confirms the amorphous nature of as-deposited and photo-doped films. The decrease in reflectance of GeTe:Ag bilayer films with photo-doping reaction time has been observed. The RAMAN spectrum showed the characteristic Raman bands for GeTe₄ (127 cm⁻¹), long chain interactions of Te–Te chains (145 cm⁻¹) and a broad peak for Ge–Ge vibrations (275 cm⁻¹) without appreciable change in their position/shape with photodoped Ag concentration. The electrical resistivity measurement shows that photo-doping of Ag led to sharp amorphous-crystalline phase transition along with an increase in transition temperature and resistivity value in both amorphous as well as crystalline state. The annealing of photo-doped GeTe:Ag samples showed an enhancement in the crystallinity of GeTe phase without any segregation of Ag phases in annealed samples. The preferential formation of GeTe (200) phase upon crystallization has been observed for GeTe:Ag films. Different optical parameters have been calculated for photo-doped and annealed samples and are discussed in conjunction with the modification of network structure of GeTe with inclusion of photo-doped Ag content.     

Structure and Thermal Properties of Lithium Cyanate

The synthesis, structural, and thermal characterization of lithium cyanate are reported in this work. LiOCN forms crystals in the trigonal crystal system. The structure was solved in the space group R$\bar{3}$ m. It is isomorphous to the structure of sodium cyanate. In the temperature range from –90 °C up to the melting point no phase transition was observed. Furthermore the vibrational Raman spectrum was measured. The system KOCN‐LiOCN shows a dystecticum and the new phase was confirmed by powder X‐ray diffraction.     

Approximation of M/M/c retrial queue with PH-retrial times

We consider the M/M/c retrial queues with PH-retrial times. Approximation formulae for the distribution of the number of customers in service facility and the mean number of customers in orbit are presented. Some numerical results are presented.     

A multi-field incremental variational framework for gradient-extended standard dissipative solids

The paper presents a constitutive framework for solids with dissipative micro-structures based on compact variational statements. It develops incremental minimization and saddle point principles for a class of gradient-type dissipative materials which incorporate micro-structural fields (micro-displacements, order parameters, or generalized internal variables), whose gradients enter the energy storage and dissipation functions. In contrast to classical local continuum approaches to inelastic solids based on locally evolving internal variables, these global micro-structural fields are governed by additional balance equations including micro-structural boundary conditions. They describe changes of the substructure of the material which evolve relatively to the material as a whole. Typical examples are theories of phase field evolution, gradient damage, or strain gradient plasticity. Such models incorporate non-local effects based on length scales, which reflect properties of the material micro-structure. We outline a unified framework for the broad class of first-order gradient-type standard dissipative solids. Particular emphasis is put on alternative multi-field representations, where both the microstructural variable itself as well as its dual driving force are present. These three-field settings are suitable for models with threshold- or yield-functions formulated in the space of the driving forces. It is shown that the coupled macro- and micro-balances follow in a natural way as the Euler equations of minimization and saddle point principles, which are based on properly defined incremental potentials. These multi-field potential functionals are outlined in both a continuous rate formulation and a time-space-discrete incremental setting. The inherent symmetry of the proposed multi-field formulations is an attractive feature with regard to their numerical implementation. The unified character of the framework is demonstrated by a spectrum of model problems, which covers phase field models and formulations of gradient damage and plasticity.     

Phase boundaries as agents of structural change in macromolecules

We model long rod-like molecules, such as DNA and coiled-coil proteins, as one-dimensional continua with a multi-well stored energy function. These molecules suffer a structural change in response to large forces, characterized by highly typical force-extension behavior. We assume that the structural change proceeds via a moving folded/unfolded interface, or phase boundary, that represents a jump in strain and is governed by the Abeyaratne–Knowles theory of phase transitions. We solve the governing equations using a finite difference method with moving nodes to represent phase boundaries. Our model can reproduce the experimental observations on the overstretching transition in DNA and coiled-coils and makes predictions for the speed at which the interface moves. We employ different types of kinetic relations to describe the mobility of the interface and show that this leads to different classes of experimentally observed force-extension curves. We make connections with several existing theories, experiments and simulation studies, thus demonstrating the effectiveness of the phase transitions-based approach in a biological setting.     

A multi-axial, multimechanism based constitutive model for the comprehensive representation of the evolutionary response of SMAs under general thermomechanical loading conditions

We present a fully general, three dimensional, constitutive model for Shape Memory Alloys (SMAs), aimed at describing all of the salient features of SMA evolutionary response under complex thermomechanical loading conditions. In this, we utilize the mathematical formulation we have constructed, along with a single set of the model’s material parameters, to demonstrate the capturing of numerous responses that are experimentally observed in the available SMA literature. This includes uniaxial, multi-axial, proportional, non-proportional, monotonic, cyclic, as well as other complex thermomechanical loading conditions, in conjunction with a wide range of temperature variations. The success of the presented model is mainly attributed to the following two main factors. First, we use multiple inelastic mechanisms to organize the exchange between the energy stored and energy dissipated during the deformation history. Second, we adhere strictly to the well established mathematical and thermodynamical requirements of convexity, associativity, normality, etc. in formulating the evolution equations governing the model behavior, written in terms of the generalized internal stress/strain tensorial variables associated with the individual inelastic mechanisms. This has led to two important advantages: (a) it directly enabled us to obtain the limiting/critical transformation surfaces in the spaces of both stress and strain, as importantly required in capturing SMA behavior; (b) as a byproduct, this also led, naturally, to the exhibition of the apparent deviation from normality, when the transformation strain rate vectors are plotted together with the surfaces in the space of external/global stresses, that has been demonstrated in some recent multi-axial, non-proportional experiments.     

无线广播电视监测信号接收链路技术分析

通过对无线广播电视信号接收链路的分析研究,汇总整理了与接收性能有关的技术要点,提出改善接收效果、提高监测性能的具体措施。通过在监测前端的实践,极大提高监测数据的准确性,为广播电视发射台的安全播出提供了重要保障。     

Stability of MgAl 2 O 4 Under High-Pressure Conditions

A theoretical investigation of the MgAl 2 O 4 crystal response to high-pressure conditions has been carried out to determine its stability against decomposition towards MgO and f -Al 2 O 3 , and towards recently observed orthorhombic phases. We have evaluated total energy versus volume curves using the density functional formalism under the non-local B3LYP approximation, as implemented in the CRYSTAL package. Numerical and analytical fittings have been carried out to determine the equilibrium unit cell geometry and equation of state parameters for all the structures and compounds involved in the phase diagram. The macroscopic compressibility of the spinel phase is interpreted considering the compressibility of its elementary MgO 4 and AlO 6 coordination polyhedra, and implications to understand the phase stability are suggested.     

Neutral to Ionic Pressure-Induced Phase Transition in the Mixed Stack Charge-Transfer Crystal ClMePD-DMeDCNQI

In the present work we report a spectroscopic investigation of the pressure-induced neutral to ionic (NI) phase transition in the mixed stack charge-transfer crystal 2-chloro-5-methyl-p-phenylenediamine 2,5-dimethyl-dicyanoquinonediimine, ClMePD-DMeDCNQI. The pressure induced phase change is studied by calculating, from spectroscopic data, the degree of ionicity, 𝜌 , which undergoes a continuous change as a function of pressure, reaching a value of about 0.65 at 3 GPa. The NI crossing reveals unique properties with respect to previously studied cases on similar compounds.