Intermittency in the Slow Particle Emission During Hadron–Nucleus Interactions

The study of the angular distribution of slow particles during high energy hadron-nucleus interaction indicates that emission of slow particles takes place from a thermally non-equilibrated system. This evidence has come out from the presence of intermittency - a phenomenon that reveals a fractal structure and represents a self-similarity in the particle production process. Hence, this study highlights inadequacy of cascade-evaporation model and advocates the need of its refinement.     

Doppler cooling a single Ca+ ion with a violet extended-cavity diode laser

We present a scheme for employing a violet extended-cavity diode laser in experiments with single, trapped ions. For this the grating-stabilised laser is spatially and spectrally filtered and referenced to a Fabry–Pérot cavity. We measure an upper limit to the line width by observing a 305-kHz FWHM beat note with the second harmonic of a titanium sapphire laser. The laser is subsequently used to optically cool a single ⁴⁰Ca⁺ ion close to the Doppler limit. PACS 03.67.Lx; 32.80.Pj; 42.55.Px     

Wave function mapping of self-assembled quantum dots by capacitance spectroscopy

We use frequency-dependent capacitance–voltage spectroscopy to study the dynamic charging of self-assembled InAs quantum dots. With increasing frequency, the AC charging becomes suppressed, beginning with the low-energy states. By applying an in-plane magnetic field, we generate an additional magnetic confinement that alters the tunneling barrier and hence the charging dynamics. In traveling through the potential barrier, the electrons acquire an additional momentum k₀, proportional to the magnetic field B. As the tunneling is enhanced, when k₀ matches the maximum of the electronic wave function Ψ (in momentum representation), we are able to map out the shape of Ψ by varying B.     

Vibration analysis of planar serial-frame structures

A hybrid analytical/numerical method is proposed that permits the efficient dynamic analysis of planar serial-frame structures. The method utilizes a numerical implementation of a transfer matrix solution to the equation of motion. By analyzing the transverse and longitudinal motions of each segment simultaneously and considering the compatibility requirements across each frame angle, the undetermined variables of the entire frame structure system can be reduced to six which can be determined by application of the boundary conditions. The main feature of this method is to decrease the dimensions of the matrix involved in the finite element methods and certain other analytical methods.     

Optical spectroscopy of single InAs/InP quantum dots around λ=1.55 μm

We discuss the preparation and spectroscopic characterisation of a single InAs/InP quantum dot suitable for long-distance quantum key distribution applications around λ=1.55 μm. The dot is prepared using a site-selective growth technique which allows a single dot to be deposited in isolation at a controlled spatial location. Micro-photoluminescence measurements as a function of exciton occupation are used to determine the electronic structure of the dot. Biexciton emission, shell filling and many-body re-normalization effects are observed for the first time in single InAs/InP quantum dots.     

Ultrafast carrier dynamics in ferromagnetic InGaMnAs

We have carried out an ultrafast time-resolved differential reflectivity study of a ferromagnetic semiconductor InGaMnAs and made a systematic comparison with low-temperature grown and high-temperature grown InGaAs reference films. Very short carrier lifetimes (2 ps) were observed in InGaMnAs and the low-temperature grown InGaAs film, but not in the high-temperature grown InGaAs film. We attribute the short lifetimes to carrier trapping by mid-gap states introduced during low-temperature MBE growth. Furthermore, at long times, we observed periodic oscillations in the differential reflectivity signal with period 20 ps, which we interpret as coherent acoustic phonons.     

Microstructure and high-temperature wear resistance of a laser surface alloyed γ-TiAl with carbon

TiC reinforced composite coating on γ-TiAl alloy was successfully fabricated by laser surface alloying with carbon. The fine TiC reinforcing phase had a gradient distribution in the coating, and its growth morphology of TiC in laser surface alloyed coating was in unique faceted platelet-like. The composite coating exhibited high hardness and excellent high-temperature sliding wear resistance.     

The Transformation Matrix of Vibrational Waves

The general theory on the transformation of elastic waves at a rigid nodal junction of an arbitrary number of thin plates is considered. The notion of transformation marix is introduced, and a way for computing it and numerical examples are given. Properties of the transformation matrix resulted from the reciprocity principle and the energy conservatin law are studied. In particular, a new relation that expresses the energy conservation low for the case where a wave damped in the direction of the joint of plates is a source of a field is obtained. Bibliography: 18 titles.