Dynamic stability of nonlinear barge-towing system

A method for predicting the dynamic stability of a nonlinear barge-towing system is presented in which the equations of motion of the dynamic system are first transformed into a six-dimensional state-space equation. The governing equation is then linearized by using the Taylor series expanding with respect to the equilibrium configurations of the towed barge. It is found that the stability conditions of a towing system are determined by the signs of the real part of some associated eigenvalues: Positive and negative 1's will result in unstable and stable dynamic responses, respectively, and 0 corresponds to the marginally stable condition. The reliability of the foregoing criteria is confirmed by the time histories (simulations) of the nonlinear barge-towing system. The effects of the stabilizing skegs and significantly improve the course stability of the towed barge and that the length and material of the towrope are also key factors affecting the dynamic stability of the barge-towing system.     

On Mutual Transform Between Number-Difference State and Phase State Corresponding to Operational Phase Operator

In the mutual transform between the number-difference state and the phase state corresponding to the operational phase operator we find that there exists an end-point ambiguousness. This problem can be avoided by Lighthill＇s method.     

The effect of air exposure on palladium–copper composite membranes

It was found that when electrolessly deposited thin Pd and Pd–Cu membranes were exposed to air at temperatures above 350 °C, their H₂ flux increased substantially immediately after the air exposure, then decreased to a new steady-state value. While this was a quasi-reversible change for the H₂ flux, the flux of insoluble species, such as N₂, irreversibly increased with every air exposure but by a much smaller extent. The extent of these changes was found to be dependent on the exposure time and the temperature of the tests. Thus, we decided to investigate the effect of gas exposures on the properties of these materials.

Palladium and palladium–copper films, prepared by electroless deposition on ceramic supports, and commercial foils were exposed to air, hydrogen and helium at 500 and 900 °C for times varying from 1 h to 1 week with the objective of determining the effect of the different exposure conditions on the surface morphology, the flux of different penetrants and the crystalline structure of the materials. Atomic force microscopy (AFM) and X-ray diffraction (XRD) were used to study the changes occurring in the films under those conditions.

It was observed that the exposure of both the electroless films and the foils to hydrogen and air markedly modified their surface morphology. The hydrogen exposure tended to smooth the surface features whereas the oxygen exposure created new surface features such holes and large peaks. Additionally it was found that the air exposure produced some oxidation of the film to create PdO.

These results suggested that a common hypothesis stating that air oxidation just cleans the surface of the membrane might not be sufficient to explain all of those changes. A contributing effect of air exposure may be the increase in surface area due to the formation of palladium oxide. However, the extent of the surface area increase was insufficient to explain the increase in steady-state H₂ flux.     

Interaction of CO molecules with surface state electrons on Ag(1 1 1)

Like other close-packed noble metal surfaces, Ag(1 1 1) exhibits an occupied Shockley-type surface state that is believed to influence the adsorption of atoms and molecules. Using low-temperature scanning tunneling microscopy, we have directly probed this interaction by investigating the local CO distribution dependent on the Ag(1 1 1) surface state standing wave pattern forming in the neighborhood of strong scattering centers such as step edges or hexagonal holes. A quantitative analysis of the STM data reveals that the CO molecules are not arbitrarily distributed upon adsorption at 5 K; they adsorb preferentially near the minima of the standing wave pattern.     

Entropy of the Binomial Field Interacting with the Two Entangled Atoms

In this paper, we investigate entropy properties of the single-mode binomial field interacting with the two entangled two-level atoms. It is found that the different initial conditions lead to the different evolutions of entropy of the binomial field.     

On a class of PDEs with nonlinear distributed in space and time state‐dependent delay terms

A new class of nonlinear partial differential equations with distributed in space and time state‐dependent delay is investigated. We find appropriate assumptions on the kernel function which represents the state‐dependent delay and discuss advantages of this class. Local and long‐time asymptotic properties, including the existence of global attractor and a principle of linearized stability, are studied. Copyright © 2008 John Wiley & Sons, Ltd.     

Bell态原子与腔场拉曼相互作用的辐射谱(英文)

采用时间演化算符方法 ,研究了Fock态腔场内通过拉曼相互作用的Bell态下两原子的辐射谱 ,给出了原子辐射谱的物理表达式。在每个Bell态下辐射谱呈现出不同的对称的多峰结构     

Quantum mechanical ab initio simulation of the electron screening effect in metal deuteride crystals

In antecedent experiments the electron screening energies of the d+d reactions in metallic environments have been determined to be enhanced by an order of magnitude in comparison to the case of gaseous deuterium targets. The analytical models describing averaged material properties have not been able to explain the experimental results so far. Therefore, a first effort has been undertaken to simulate the dynamics of reacting deuterons in a metallic lattice by means of an ab initio Hartree-Fock calculation of the total electrostatic force between the lattice and the successively approaching deuterons via path integration. The calculations have been performed for Li and Ta, clearly showing a migration of electrons from host metallic to the deuterium atoms. However, in order to avoid more of the necessary simplifications in the model the utilization of a massive parallel supercomputer would be required.     

Simplified Scheme for Test of Quantum Nonlocality Without Using Bell Inequality

A simplified scheme is proposed for the test of quantum nonlocality of the type described by Hardy [Phys.Rev.Left.71 (1993) 1665].In the scheme two appropriately prepared atoms are simultaneously sent through a cavity and dispersively interact with the cavity field.Then state-selective measurements are performed on these atoms,which may reveal quantum nonlocality without using Bell inequality.We also propose a simple scheme for the generation of multi-atom entangled states.``     

Multilayer hydrous oxide growth on copper in base and its correlation with previously reported electrocatalytic data for this electrode system

A repetitive potential cycling procedure was used to produce a specific multilayer hydrous oxide film on copper in base at 60 °C. Such a deposit undergoes reduction in a quasi-reversible manner at ca. −0.1 V (RHE), i.e. at a potential that is unrelated to Pourbaix data for copper but, as demonstrated previously, is of major significance with regard to the electrocatalytic behaviour of this electrode system. In accordance with the incipient hydrous oxide/adatom mediator model of electrocatalysis, an active surface state of the metal (Cu*) is assumed to be involved both in electrocatalysis and as a primary product in the hydrous oxide reduction reaction. While the latter process occurs very rapidly at −0.1 V, it is not usually reversible as it is accompanied by subsequent rapid loss of the active state of the metal. The same general approach was used previously to explain the hydrous oxide and electrocatalytic behaviour of a range of noble metals. Received: 28 August 1999 / Accepted: 11 November 1999