Gamma-ray spectroscopy of the neutron-rich Ni region through heavy-ion deep-inelastic collisions

Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T _1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the doubly magic ⁶⁸Ni and its neighbor ^69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed. Received: 1 May 2001 / Accepted: 4 December 2001     

Estimation of dynamic properties of attractors observed in hollow copper electrode atmospheric pressure arc plasma system

Understanding of the basic nature of arc root fluctuation is still one of the unsolved problems in thermal arc plasma physics. It has direct impact on myriads of thermal plasma applications being implemented at present. Recently, chaotic nature of arc root behavior has been reported through the analysis of voltages, acoustic and optical signals which are generated from a hollow copper electrode arc plasma torch. In this paper we present details of computations involved in the estimation process of various dynamic properties and show how they reflect chaotic behavior of arc root in the system.     

Formation on field emitters coated with fullerenes of microformations producing ordered emission images

Field emission projector studies of fullerene coatings deposited on tungsten tip field emitters reveal specific ordered patterns in the form of doublets, quadruplets, rings, disks, and other forms in the emitter images. The ways in which these types of ordered emission patterns arise and their relation to C₆₀ microformations have been established. Possible causes of the emergence of the ordered emission images are analyzed on the basis of published data and experimental results obtained. A modification of the model of field emission from the surface of microformations taking into account internal reflection of the electronic waves from the formation boundaries has been proposed.     

Shell model interaction between proton holes and between proton holes and neutron particles around 208Pb

An effective residual interaction between particles and holes for shell model calculations around ²⁰⁸Pb, derived from the interaction between free nucleons, is compared with the measured properties of proton-hole neutron states in ²⁰⁸Tl and the interaction between proton holes is adjusted to newly measured level energies in ²⁰⁶Hg. These interaction elements are particularly relevant for neutron-rich nuclei. The adjustment of two mixing elements reproduces the known γ-decay data in ²⁰⁸Tl. Received: 2 April 2002 / Accepted: 2 May 2002     

Crystal structure and magnetic ordering of RNi Si compounds

The element distributions and the magnetic ordering behaviour of compounds RNi₁₀Si₂ (R = Tb, Dy, Ho, Er, Tm) have been studied by neutron powder diffraction down to temperatures of 1.6 K. The compounds crystallize in an ordered variant of the ThMn₁₂ structure type in the tetragonal space group P4/nmm. An ordered 1:1 distribution of Ni and Si on sites 4d and 4e, respectively, corresponds to a modulation vector [0, 0, 1] with respect to the space group I4/mmm of the ThMn₁₂ structure. TbNi₁₀Si₂ orders antiferromagnetically below T _N = 4.5 K with a magnetic propagation vector of [0, 0, 1/2]. The magnetic Tb moments, 8.97(2) /Tb atom at 1.6 K, are aligned along the c-axis. The Ni sites in TbNi₁₀Si₂ do not carry any ordered magnetic moments. The compounds with R = Dy, Ho, Er, and Tm are paramagnetic down to 1.6 K and 3.0 K, respectively. Received 10 July 2002 / Received in final form 12 September 2002 Published online 29 October 2002     

Higher-order <Emphasis Type="Bold">?</Emphasis> corrections in the semiclassical quantization of chaotic billiards

In the periodic orbit quantization of physical systems, usually only the leading-order ? contribution to the density of states is considered. Therefore, by construction, the eigenvalues following from semiclassical trace formulae generally agree with the exact quantum ones only to lowest order of ?. In different theoretical work the trace formulae have been extended to higher orders of ?. The problem remains, however, how to actually calculate eigenvalues from the extended trace formulae since, even with ? corrections included, the periodic orbit sums still do not converge in the physical domain. For lowest-order semiclassical trace formulae the convergence problem can be elegantly, and universally, circumvented by application of the technique of harmonic inversion. In this paper we show how, for general scaling chaotic systems, also higher-order ? corrections to the Gutzwiller formula can be included in the harmonic inversion scheme, and demonstrate that corrected semiclassical eigenvalues can be calculated despite the convergence problem. The method is applied to the open three-disk scattering system, as a prototype of a chaotic system. Received 10 September 2001 and Received in final form 3 January 2002     

The simulation of dendrite growth and partial discharges in epoxy resin

A self-consistent model of the development of dendrites and partial discharges in a dielectric solid under a variable voltage is suggested. Dendrites originate at sites with the enhanced local field strength and also where the dielectric is broken down under the action of partial discharges. The numerical simulation is used to quantitatively describe the space-time dynamics of the dendrites and partial discharges in epoxy resin for the tip-plane electrode configuration. The simulated data are compared with electrical measurements of partial discharges and with optical images of dendrite growth under the same conditions.     

Development of high-speed video cameras for Dynamic PIV

The most promising next generation Image Velocimtry (IV) is the high-speed Dynamic PIV. It requires the development of innovative high-speed video camera sensors. We started by specifying the required performance of these new sensors, for measurements in air and water flows. These criteria founded on the most recent developments in PIV algorithms and incorporate results from a large questionnaire survey of users of high-speed video cameras in Japan. The results suggest that the followings are required: (1) frame rate of 1,000,000 fps, (2) pixel count of 1,000,000 pixels, (3) frame storage capacity of 100–200 frames for tracing a single event and 10,000 frames for turbulent measurements, (4) gray levels of 4–8 bits for PTV; 12 bits for observation. Finally, we reviewed the state of the art of high-speed video-image sensors. Currently the standard parallel-readout sensors can operate at 1 Kfps with a pixel count of approximately 1 Kpixels. The In-situ Storage Image Sensor (ISIS) developed by the authors has recently achieved frame rates of 1 Mfps.     

Aspects of alpha-particle scattering and structure of the nuclear surface

The interaction of α particles above 5 MeV with a 2s-1d target is dominated by resonances. It cannot be described only in terms of a mean-field one-body potential. An analysis of the elastic α-particle scattering by ²⁸Si encourages the comprehension of the resonance states to be mainly fragments of a mixed-parity band. In the present article, the angular distributions of particles scattered by ³²S are analyzed in terms of such bands. The analysis of new data from an experiment made at Florida State University reveals the existence of states that do not belong to the above bands. This follows from a coupled-channel analysis of the elastic and inelastic (2⁺) cross sections. An α-particle structure at the nuclear surface is suggested.