acta physica slovaca

Abstract: A variational problem for three-dimensional (3D) classical lattice models is considered with trial state given by two-dimensional (2D) uniform product of local variational weights. This approach, the tensor product variational approach (TPVA), has been applied to 3D classical models (the Ising and the Potts models). We consider a way of estimating the magnetic critical exponent $\beta$ for the simple 3D Ising model assuming a functional form of the spontaneous magnetization in the off critical region, where the TPVA provides reliable data.

Abstract: A generalized harmonic oscillator on noncommutative spaces is considered. Dynamical symmetries and physical equivalence of noncommutative systems with the same energy spectrum are investigated and discussed. General solutions of three-dimensional noncommutative harmonic oscillator are found and classified according to dynamical symmetries. We have found conditions under which three-dimensional noncommutative harmonic oscillator can be represented by ordinary, isotropic harmonic oscillator in effective magnetic field.

Abstract: The contribution deals with thermophysical parameter estimation in dynamic methods. The influence of temperature measurement uncertainty on the parameter estimation uncertainty is studied using least squares procedure. Difference analysis is used for time window determination in which the fitting procedure should be applied. The sensitivity coefficient analysis is performed on Pulse transient, Step-wise transient and EDPS method.

Abstract: Activating a flip-flop circuit by a current fast-rising slope impulse, the circuit occupies one of the two stable states, the stable state `one' or `zero'. In case of a perfect flip-flop symmetry over a large number of cycles, a noise causes the ratio of  `ones' and `zeros' is equal to one  - 50% position of a flip-flop. However, any imbalance in the system changes the probability of taking a `one' or a `zero', and thus the ratio of `ones' and `zeros'. In this paper, the formula for equivalent voltage of the flip-flop circuit is derived. This voltage is incorporated into the flip-flop as a voltage source to restore 50% position. The formula is derived for the first time. The results are useful for capacitance measurement and in capacitive sensor applications.

Abstract: We have investigated the halo formation in the neutron rich Ca isotopes within the framework of recently proposed relativistic mean-field plus BCS (RMF+BCS) approach wherein the single particle continuum corresponding to the RMF is replaced by a set of discrete positive energy states for the calculation of pairing energy. For the neutron rich Ca isotopes in the vicinity of neutron drip-line, it is found that further addition of neutrons causes a rapid increase in the neutron rms radius with a very small increase in the binding energy, indicating thereby the occurrence of halos. This is essentially caused by the gradual filling in of the loosely bound 3s1/2 state. Interesting phenomenon of accommodating several additional neutrons with almost negligible increase in binding energy is shown to be due to the pairing correlations.

Abstract: Moments of inertia of even-even actinide nuclei have been calculated in the framework of BCS cranking model in which the neutron-proton (np) pairing has been taken into account. First, making a perturbative approximation, we assumed that the form of the equations of the BCS theory and usual Bogolyubov transformations are unchanged. Second, considering a new approach for the np pairing strength constant we observed that the results changed dramatically. Since neutrons and protons occupy different major shells in heavy nuclei, well known thought is that interaction between themselves might be weak due to small overlapping of wave functions thus the influence of the np pairing might be so small in the ground state. However, our results showed that the np pairing might be effective on the moments of inertia of actinide nuclei if it has been considered correctly.

Abstract: We present the architecture and code design for a highly scalable, 2.5 Gb/s per user optical code division multiple access (OCDMA) system. The system is scalable to 100 potential and more than 10 simultaneous users, each with a bit error rate (BER) of less than 10^{-9}. The system architecture uses a fast wavelength-hopping, time-spreading codes. Unlike frequency and phase sensitive coherent OCDMA systems, this architecture utilizes standard on-off keyed optical pulses allocated in the time and wavelength dimensions. This incoherent OCDMA approach is compatible with existing WDM optical networks and utilizes off the shelf components. We discuss the novel optical subsystem designs for encoders and decoders that enable the realization of a highly scalable incoherent OCDMA system with rapid reconfigurability. A detailed analysis of the scalability of the two dimensional code is presented and select network deployment architectures for OCDMA are discussed.

Abstract: Electrical conduction in Y1-xScxBa2Cu3Oy prepared in the range of x=0.0 - 1.0 was investigated. X-ray, infrared spectroscopy and electron microscope inspections were employed to develop an understanding for the structural properties of the samples. The results indicate that all the samples were multiphase even at x=0.1 due to probably the low solubility of Sc in YBa2Cu3Oy. The samples were found to be the mixtures of semiconductive and superconductive phases, the ratio of which determines the critical temperature, Tc, the resistance and temperature dependence of the resistance. Tc varied within a narrow range of 10 K until the semiconductivity appears at x=0.9. It was argued that the Y1-xScxBa2Cu3Oy samples show semiconducting transition at a Sc content higher than the percolation threshold. Hopping mechanisms were found to be responsible for the conduction in Y0.1Sc0.9Ba2Cu3Oy in which the density of states at the Fermi level was obtained as 6.0 x 10E+21 m^{-3} eV^{-1}.

Abstract: We study an impact of the cosmological environment on the solar gravitational system by the imbedding formalism of Gautreau. It turns out that the cosmic mean-mass density and the cosmological constant give negligibly small contribution to the gravity potentials. On the other hand, the cosmic acceleration beyond the Robertson-Walker geometry can considerably influence the curvature of spacetime in the solar system. The resulting anomalous constant acceleration towards the Sun is order of magnitude smaller than that measured by Pioneer 10 and 11. However, it is larger than the second order terms of potentials, thus well within the sensitivity of new gravity probes such as the LATOR mission.