Table of contents

This paper deals with the problem of stabilizability of a dynamics of two nonlinearly coupled oscillators which linearization at the origin is controllable and observable. Under assumptions on the nonlinear part, we prove that the system is globally exponentially stabilizable (G.E.S.) by means of linear feedback law and can be G.E.S. using a state estimation given by an observer.

We analyze the influence of imperfections on which-way and eraser experiments. We study how to modify the mathematical definition of distinguishability to account for the nonideal correlations between the incident particle and the which-way device. On the other hand, we show that the quantum eraser scheme here considered is insensitive to the detection inefficiencies, but can be invalidated by large values of background counts.

We investigate the potentials of future high energy lepton-proton colliders to detect supersymmetric particles in the charged current type lp → _lX, l = e, μ, reactions. We also study their decays by using the mass spectrum given in the Technical Design Report of ATLAS Collaboration (SUGRA Point 6 corresponding to large tanβ).

Nuclear level densities and thermodynamic functions have been determined for light A nuclei, from a microscopic theory, which includes nuclear pairing interaction. Nuclear level densities have also been obtained using Bethe formula as well as constant temperature formula. Level densities extracted from the theories are compared with their corresponding experimental values. It is found that the nuclear level densities deduced by considering various statistical theories are comparable; however, the Fermi-gas formula becomes inadequate at higher excitation energies. This conclusion, which has also been arrived at by other investigations, reveals that a realistic treatment of the statistical nuclear properties requires the introduction of residual interaction. The effects of the pairing interaction and deformation on nuclear state densities are illustrated and discussed.

A detailed study on the gamma decay of ¹⁵⁴Eu to ¹⁵⁴Gd nuclei has been carried out using different advanced gamma rays spectrometers such as high efficiency hyper pure germanium (HPGe) detector, (HPGe–HPGe) coincidence spectrometer and HPGe-4π(NaI (Tl)) anti-Compton array. The identified gamma ray transitions were placed in a proposed decay scheme. The energy levels of ¹⁵⁴Gd are calculated using the IBA-1 model and compared to the available experimental data. The rotational behavior of ¹⁵⁴Gd is discussed in terms of moment of inertia.

Electron capture from excited H(2s) and H(2p) targets by protons and alpha particles, at intermediate and high collision energies, is theoretically studied employing three distorted wave models. This study is carried out using the Continuum Distorted Wave, the Continuum Distorted Wave – Eikonal Initial State and the Continuum Distorted Wave – Eikonal Final State approximations, according to the symmetry of the collision reaction. Total and partial cross sections are calculated and compared with other existing theoretical results. The influence of the polarization of the initial states on the cross sections is also analyzed.

We have calculated the excitation energies for the lowest 23 LS and 43 fine-structure levels as well as oscillator strengths and radiative decay rates for the transitions among (1s²2s²2p⁶) 3s² (¹S), 3s3p (^1,3P^o), 3p² (¹S, ³P, ¹D), 3s3d (^1,3D), 3s4s (^1,3S), 3p3d (^1,3P^o, ^1,3D^o, ^1,3F^o), 3s4p (^1,3P^o), 3s4d (^1,3D), 3s4f (^1,3F^o) and 3p4s (^1,3P^o) states in P IV. These states are represented by extensive configuration-interaction (CI) wavefunctions obtained with the CIV3 computer code of Hibbert. The calculations have been carried out in both LS and intermediate-coupling schemes. Relativistic effects are included through the Breit-Pauli approximation via spin-orbit, spin-other-orbit, spin-spin, Darwin and mass correction terms. We have also calculated the radiative lifetimes from our radiative decay rates. Our results are compared with other theoretical calculations and the available experimental data.

The spectra of Pt VIII and Au IX ions were investigated for the first time. The spectra were excited in a low-inductance vacuum spark and photographed on high resolution VUV spectrographs. One hundred and seventy eight lines in the Pt VIII ion and one hundred and fifty four lines in the Au IX ion have been classified as belonging to the 5d³–5d²6p transitions. The complete energy structures of the ground state 5d³ configuration and the first excited odd 5d²6p configuration have been determined in both ions. The analyses of both spectra were based on semi-empirical calculations in the frame of an orthogonal operators approach.

The linear stability problem for a fluid in a classical Benard configuration is examined. In addition to a steady temperature difference between the walls of the fluid layer, a time-dependent perturbation is applied to the wall temperatures. The time-dependent perturbation is expressed in Fourier series. The shift in the critical Rayleigh number is calculated and it is found that it is possible to advance or delay the onset of convection. Some comparisons are made with the known results.

We compare the Pegg-Barnett (PB) formalism with the covariant phase observable approach to the problem of quantum phase and show that PB-formalism gives essentially the same results as the canonical (covariant) phase observable. We also show that PB-formalism can be extended to cover all covariant phase observables including the covariant phase observable arising from the angle margin of the Husimi Q-function.

This paper investigates the effects of radiation on the MHD mixed free-forced convective steady laminar boundary layer flow of an optically thick electrically conducting viscous fluid, past a moving semi-infinite vertical plate, for large temperature differences. A uniform magnetic field is applied perpendicular to the plate. The density of the fluid is assumed to decrease exponentially with temperature. The usual Boussinesq approximation is neglected due to the large temperature difference between the plate and the fluid. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. With appropriate similarity transformations, the boundary layer equations governing the flow are reduced to ordinary differential equations, which are numerically solved by applying the Runge-Kutta method with the shooting technique. The effects of the radiation parameter R, the local magnetic parameter M_x and the density/temperature parameter n are examined on the velocity and temperature distributions as well as the coefficients of skin-friction and heat flux.

Stark widths of three Ar I spectral lines have been measured in an Ar + He plasma at 13 000 K electron temperature and compared with existing experimental values. The Stark broadening parameters of these three experimentally investigated lines have been calculated within the semiclassical perturbation approach as a function of temperature and compared with the experimental data.

The different optical diagnostic techniques for determining dusty plasma parameters are presented. A comparative analysis of different methods for determining the gas-phase temperature and the density of alkali atoms in low-temperature thermal dusty plasma are carried out. The results obtained show that conventional gas-plasma diagnostics are inapplicable to dusty plasmas. Diagnostic methods allowing for the presence of dust grains are proposed and a system for determining the parameters of dusty plasma is developed. A combination of novel methods for determining the temperature, mean size, density and spectral refractive index of particles in high-temperature flows is described. The technique is based on empirical inversion of the forward-scattering transmittance and spectral emission-absorption measure ments. The measurements were successfully inverted for Al₂O₃, CeO₂, and ash particles in plasma flows. The particle temperature, concentration, mean size, and complex refractive index are retrieved.

As is confirmed experimentally, the liquid-gas critical points of heavy alkali metals attached to the percolation threshold of electron shells obey to a scaling with the atom ionization potential. For light alkali metals, a cell model which yields a renormalized Madelung interaction law reveals possible deviations from the scaling due to quantum effects. Independent estimates based on the phenomenological Clausius-Clapeyron equation together with a parametric dependence of the critical temperature and pressure on the renormalized Madelung coefficient confirm that lithium considerably deviates from the scaling. We have obtained the critical parameters of lithium: T_c = 3350 K, p_c = 430 bar, and ρ_c = 0.053 g cm^-3 in reasonably well agreement with early experimental estimates based on measurements of the equilibrium liquid and gas densities.

We have calculated the density of impurity states (DOIS) as a function of applied uniaxial stress of shallow hydrogen donor impurity in a quantum well (QW). The calculations were carried out using a variational procedure within the effective mass approximation. The results show that the density of impurity states is a function of applied stress. It is therefore important to take into consideration the effect of applied stress in a QW when carrying out experimental studies of optical and electronic properties of such heterostructures.