Game of two cars: Case of variable speed

A stochastic version of Isaacs's (Ref. 1) game of two cars is dealt with here. In this version, the pursuer, owing to thrust and drag forces, has a variable speed, whereas the evader's speed is constant. Also, the pursuer can maneuver as long as his speed is bounded by some lower and upper limits. The probability of interception, corresponding to optimal (saddle-point) feedback strategies, is computed and serves as a reference for evaluating the performance of four different versions of the proportional navigation pursuit law as well as two other strategies.     

A cutting plane algorithm for a clustering problem

In this paper we consider a clustering problem that arises in qualitative data analysis. This problem can be transformed to a combinatorial optimization problem, the clique partitioning problem. We have studied the latter problem from a polyhedral point of view and determined large classes of facets of the associated polytope. These theoretical results are utilized in this paper. We describe a cutting plane algorithm that is based on the simplex method and uses exact and heuristic separation routines for some of the classes of facets mentioned before. We discuss some details of the implementation of our code and present our computational results. We mention applications from, e.g., zoology, economics, and the political sciences.     

Influence of focusing depth on the microfabrication of waveguides inside silica glass by femtosecond laser direct writing

We studied the influence of focusing depth on the index change threshold and damage threshold of silica glass irradiated by a focused 120 fs laser beam. Both thresholds increased with the focusing depth. The aspect ratio of the waveguide cross section can be selected by changing the focusing depth. A 5 mm long waveguide was written at the depth of 2100 μm, which was single mode at 632.8 nm and exhibited propagation loss of 0.56 dB/cm. The refractive index change was calculated to be ∼2.47×10^-3. The influence of the focusing depth should be considered in multi-layer devices as shown in the fabrication of a 3×3 waveguide array. PACS 42.62.-b; 42.82.Et; 81.05.Kf     

Nonlinear magneto-optical diffraction by two-dimensional magnetic superstructures

Nonlinear (at the second-harmonic frequency of the incident light) optical reflection by two-dimensional magnetic superstructures is theoretically studied. A square lattice of magnetic dots and a hexagonal lattice of magnetic bubbles (cylindrical magnetic domains) are considered. Because the periods of these structures are comparable with the wavelengths of the fundamental and the second-harmonic radiation, it would be possible to observe diffraction at the second-harmonic frequency. A polarization analysis of nonlinearly diffracted radiation is performed and the numbers of observable diffraction orders for the above structures are estimated. Received: 10 January 2002 / Published online: 11 June 2002     

The nonlinear effects of quantum electrodynamics at high energies

In this paper we considere ⁺ e ^? scattering with intermediate photon-photon scattering as a possibility for getting information about the nonlinear effects of quantum electrodynamics (QED) at high energies. This process is a higher-order correction to double bremsstrahlung. However, these two processes have quite different behaviour with the photon-photon scattering angle. Here we calculate the unpolarized differential cross section of thee ⁺ e ^? scattering with intermediate γγ scattering and also the interference terms with the double bremsstrahlung. Moreover, we show that the sum of these two contributions predominates over the contribution of the double bremsstrahlung for sufficiently large scattering angles of the photons. This result enables us to extract the differential cross section of the γγ scattering. Through extrapolation to different kinematical conditions we can get the cross sections for nearly real photon-photon scattering, photon splitting and Delbrück scattering. As a quantitative example we use the result for a test of the electron propagator in a gauge-invariant way with the usual minimal interaction. We give also numerical examples of this test, which will improve the present values of the testing parameters.     

Laboratory experiment on kinetic Alfven waves in connection withphenomena in space plasmas

A laboratory experiment has been performed in connection with interesting phenomena in space plasmas such as geomagnetic pulsations in the magnetosphere or particle acceleration by the kinetic Alfven wave in field-aligned currents of the auroral circuit. Fast waves or MHD surface waves in a cylindrical finite-β plasma have been observed to be mode converted into kinetic Alfven waves at the Alfven resonance layer. The surface waves were excited using small loop antennas located at the edge of the inhomogeneous plasma to simulate those on the magnetosphere or plasmapause     

Fluorides of ruthenium and chromium: Theoretical studies

The electronic and structural characteristics of CrF₅, CrF₄, RuF₅ and RuF₄ were studied. Ab initio (SCF-CI) calculations were performed with different structures and spin states for each complex. The favored conformation always corresponds to the highest multiplicity: doublet for CrF₅ in D_3h, triplet for CrF₄ in T_d, quadruplet for RuF₅ in C_4v and quintuplet for RuF₄ in D_4h symmetry.     

Effects of Au coating on thermal stresses in stainless-to-Kovar packages

A finite-element method (FEM) analysis has been carried out on the thermally-induced stresses generated when stainless steel covers are laser-welded to Au-coated Kovar TO headers during the packaging of semiconductor lasers. In particular, the effect of varying the Au coating thickness of these stresses was investigated. Maximum stresses were found to be reduced as the Au thickness increased. This effect is attributed to the reduction in thermal gradient in the weld region provided by the increased thermal conduction of thicker Au. The result suggests that adequate Au coating thickness is important for ensuring good reliability of opto-electronic packages having laser-welded caps. This revised version was published online in June 2006 with corrections to the Cover Date.     

T-violation neutron experiment and polarized3He

An experimental scheme of the spin detailed balance in polarized neutron transmission through a polarized nuclear target is discussed for the T-violation test. The value of the spin detailed balance is estimated by using the data of the scattering amplitudes. The nuclear polarizations of proton,³He and¹³⁹La are discussed for the T-violation experiment.     

CO-laser photoacoustic detection of phosgene (COCl2)

Detection of COCl₂, a highly toxic gas in chemical industry, using laser photoacoustic spectroscopy is presented. The spectrophone system used has a broad band LN₂ cooled CW CO laser as a source of radiation, which operates from 4.8–8.4 um in the mid-infrared. Using an extracavity open longitudinal resonant cell, absorption signals to about 30 CO laser lines in the 5.45 um region could be observed. detection sensitivity has been estimated to be ppb order.This work has been supported by the NSFC