International Journal of Modern Physics B

The density profiles of a hard Gaussian overlap (HGO) fluid confined in between hard walls and in contact with a hard wall are studied using the density functional theory. The hyper-netted chain (HNC) approximation is used to find the coupled integral equations for the density profiles. The restricted orientation model (ROM) is used. The required homogeneous direct correlation function (DCF) is obtained by solving Ornstein–Zernike (OZ) integral equation numerically, using the Precus–Yevick (PY) approximation and the procedure mentioned by Letz and Latz [Phys. Rev.E60, 5865 (1999)]. We also obtained the DCF of hard ellipsoidal (HE) fluid by using the modified closest approach introduced by Rickayzen [Mol. Phys.68, 903 (1989)]. For both HGO and HE, we calculate the density profiles of molecules parallel and perpendicular to the walls and we compare the results. The calculations are performed for various values of packing fractions of the fluid and various molecular elongations. For moderate elongations, k≤3, the results for HGO and HE are almost the same, especially for the density profile of the molecules parallel to the walls but for k=5 there are some discrepancies between the results, in particular for the density profiles of the molecules perpendicular to the walls.

In this paper we consider a non-dissipative distributed parameter circuit at a finite temperature T. We find the unitary operator for diagonalizing the Hamiltonian of the uniform periodic transmission line. The unitary operator is expressed in a coordinate representation. Thermal field dynamic is used in our discussion. It is shown that distributing parameter circuits and quantum fluctuations, which also have distributing properties, are related to both the circuit parameters and the positions and the model of signals and temperature T. The higher the temperature, the more quantum noise the circuit exhibits. The research will be helpful to miniaturize intergreate circuits and electric components. It will be also significant for the futher study of the qualitities of mesoscopic system.

As a continuation of our previously published work, the metastable phase diagram of the Blume–Emery–Griffiths model with the arbitrary bilinear (J), biquadratic (K) and crystal field interaction (D) is presented in addition to the equilibrium phase diagram in (T/K, J/K) and (T/K, D/K) plane by using the pair approximation of the cluster variation method on a body centered cubic lattice. We also calculate the phase transitions for the unstable branches of order parameters. The calculated first- and second-order phase boundaries of the unstable branches of the order parameters are superimposed on the equilibrium phase diagram and metastable phase diagram. It is found that the metastable phase diagram and the first- and second-order phase boundaries for unstable branches of order parameters always exist at low temperatures, which are consistent with the experimental and theoretical works.

The purpose of this research is to investigate the structure of lead zirconate titanate ceramics (Zr:Ti = 52:48) doped with CeO₂ and corresponding properties such as micro-structural properties, physical properties, dielectric constant (ε_r), piezoelectric properties (k_p, Q_m, and d₃₃), and the ferroelectric property. The specimens were prepared via a conventional mixed oxide method and sintered at 1200°C. Rietveld refinement of X-ray diffraction patterns resulted in the P4mm tetragonal structure for all samples. At a high dopant content (10 mol%), pyrochlore phases of CeO₂ appeared which caused the detriment of dielectric and piezoelectric properties. At a low dopant content (1 mol%), Ce⁴⁺ ions entered the B site with isovalent dopant effects, and clearly resulted lower values of ε_r, and k_p compared with those of the undoped sample. The hysteresis loops showed ferroelectric properties for all samples. Microstructures displayed dense grain distribution and thus yielded a high density. The additional phase of CeO₂ was clearly observed for 10 mol% doping which implied it was overdoped. Finally, the Curie temperature has been found to decrease with increasing dopant content, as determined from high temperature X-ray diffraction and differential scanning calorimetry.

The molten and cross-linked polybutadiene were observed by NMR methods in order to disclose the influence of the presence of the temporary and permanent junctions between the polymeric chains on the relaxation of the longitudinal and transverse magnetization. The residual dipolar interaction determined by the entanglements of the polymeric chains is observed by the pseudo-solid echo method and is associated with the existence of the temporary network.

The results of an investigation of humidity sensors based on ceramic material are discussed. It is widely approved that the ceramics based humidity sensor is superior to the polymer one due to their better thermal stability over a variety of chemical species, wide range of operating temperature and rapid response to change of humidity. Properties of humidity sensor based on ceramic system Ca_1-xY_xTi_1-xCo_xO₃ are presented. The role of each part of the sensitive material in the electrical conduction process is determined based on measurements and calculated equivalent circuits. The proposed model describes the water absorption on grain and grain boundaries surfaces with very good fit to the experimental data. A new approach to the modeling of the impedance frequency dependence by means of an equivalent circuit yields very promising results for sensors.

We investigate experimentally and via computer simulations the segregation pattern of binary granular mixtures in a vibrated container with bottlenecks. During the vibration the granular motion is more violent at the bottlenecks than at the bellies. Particles with more mobility congregate to the necks, while those with less mobility congregate to the bellies. We use discrete element simulations to reproduce the main characteristics of the experimental observations.

The varieties of intensity correlation time T with input signal are studied for gain-noise model of a single-mode laser driven by colored pump noise and colored quantum noise with colored cross-correlation with a bias signal modulation in this paper. By using the linear approximation method, it is found that a minimum (i.e. suppression) in the curves of the intensity correlation time T versus the bias current i₀ exists when the noise correlation coefficient λ is negative; and the intensity correlation time T increases monotonously with the increase of i₀ when λ≥0. In addition, we also analyze the curve of T versus the signal frequency Ω, find that no matter what the value of λ is, a minimum (i.e. suppression) in the T-Ω curves always exists.

The structure of xMoO₃·(100-x)[2P₂O₅·PbO] glass system with 0≤x≤50 mol% is investigated by IR and Raman spectroscopies.

The characteristic bands of the glass matrix [2P₂O₅·PbO] and MoO₃ oxide due to the stretching and bending vibrations are identified. This allows us to identify the specific structural units which occur in these glasses and to deduce the role of the MoO₃ oxide on the structural aspects of 2P₂O₅·PbO network.

At high MoO₃ content a depolymerization of the phosphate structure appears and the short phosphate chain units or ring structures are formed too.

The structure of xFe₂O₃·(100-x)[3B₂O₃·BaO] system with 0≤x≤50 mol% was studied by DTA, X-ray diffraction, density, optical microscopy and EPR measurements in vitreous and partial crystallized state, the samples being obtained by under cooling method. The data obtained show that, by melting the samples at T_e = 1200°C or T_e = 1250°C, glasses for x≤35 mol% were obtained, and the forming of crystalline microprecipitates of Fe₂O₃ in the sample with x = 50 mol%. It was also established that the thermal treatment at 565°C without and in the presence of magnetic field of 0.7 T is influencing the forming and the development of the Fe₂O₃ microcrystals in samples with x≥35 mol%. The samples melted at T_c = 1200°C and T_c = 1250°C were studied by magnetic susceptibility measurements which evidenced similar results with those obtained by EPR. Also, the magnetic measurements show that for the thermal untreated samples the iron ions participate at superexchange interactions for x≥5 mol% and for x≥10 mol%, respectively.