728 research outputs found
Semi-classical Characters and Optical Model Description of Heavy Ion Scattering, Direct Reactions, and Fusion at Near-barrier Energies
An approach is proposed to calculate the direct reaction (DR) and fusion
probabilities for heavy ion collisions at near-Coulomb-barrier energies as
functions of the distance of closest approach D within the framework of the
optical model that introduces two types of imaginary potentials, DR and fusion.
The probabilities are calculated by using partial DR and fusion cross sections,
together with the classical relations associated with the Coulomb trajectory.
Such an approach makes it possible to analyze the data for angular
distributions of the inclusive DR cross section, facilitating the determination
of the radius parameters of the imaginary DR potential in a less ambiguous
manner. Simultaneous -analyses are performed of relevant data for the
O+Pb system near the Coulomb-barrier energy
Trimer classical spin liquid from interacting fractional charges
We study a problem of interacting fractional charges with the J(1)-J(2)-J(3) Ising model on a checkerboard lattice under magnetic field. As a result of the interplay between repulsive interactions and particle density tuning by a magnetic field, the fractional charges form a classical spin liquid (CSL) phase. The CSL phase is composed of degenerate spin configurations, which can be mapped to the trimer covering of dual square lattice. The CSL state shows macroscopic ground-state entropy, implying the emergence of a novel quantum spin liquid phase when quantum fluctuations are turned on. In addition to the CSL phase, the system exhibits multiple magnetization plateaus, reflecting the fertile screening processes of dimer-monomer mixtures
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Section Data for the 7Li+208Pb System at Near-Coulomb-Barrier Energies using the Folding Potential
Simultaneous analyses previously made for elastic scattering and
fusion cross section data for the Li+Pb system is extended to the
Li+Pb system at near-Coulomb-barrier energies based on the
extended optical model approach, in which the polarization potential is
decomposed into direct reaction (DR) and fusion parts. Use is made of the
double folding potential as a bare potential. It is found that the experimental
elastic scattering and fusion data are well reproduced without introducing any
normalization factor for the double folding potential and that both the DR and
fusion parts of the polarization potential determined from the
analyses satisfy separately the dispersion relation. Further, we find that the
real part of the fusion portion of the polarization potential is attractive
while that of the DR part is repulsive except at energies far below the Coulomb
barrier energy. A comparison is made of the present results with those obtained
from the Continuum Discretized Coupled Channel (CDCC) calculations and a
previous study based on the conventional optical model with a double folding
potential. We also compare the present results for the Li+Pb system
with the analysis previously made for the Li+Pb system.Comment: 7 figures, submitted to PR
Interferometric detection of dispersed shock waves in small scale diaphragm-less shock tube of 1mm diameter
We have developed a small scale shock tube of 1mm diameter which has a diaphragm-less driver section. The experiment is performed by using our small scale shock tube, where the propagation velocities of the shock waves are measured with a specially designed laser interferometer under several pressure conditions. Helium and CO2 are used as the driver and test gas, respectively. As the results show, we have succeeded in observing weak shock waves in a shock tube of 1mm diameter. The fully or partly dispersed shock waves, which are attributed to the exitation of the vibrational energy of CO2, are also observed at the weak shock region
A Novel Method for the Solution of the Schroedinger Eq. in the Presence of Exchange Terms
In the Hartree-Fock approximation the Pauli exclusion principle leads to a
Schroedinger Eq. of an integro-differential form. We describe a new spectral
noniterative method (S-IEM), previously developed for solving the
Lippman-Schwinger integral equation with local potentials, which has now been
extended so as to include the exchange nonlocality. We apply it to the
restricted case of electron-Hydrogen scattering in which the bound electron
remains in the ground state and the incident electron has zero angular
momentum, and we compare the acuracy and economy of the new method to three
other methods. One is a non-iterative solution (NIEM) of the integral equation
as described by Sams and Kouri in 1969. Another is an iterative method
introduced by Kim and Udagawa in 1990 for nuclear physics applications, which
makes an expansion of the solution into an especially favorable basis obtained
by a method of moments. The third one is based on the Singular Value
Decomposition of the exchange term followed by iterations over the remainder.
The S-IEM method turns out to be more accurate by many orders of magnitude than
any of the other three methods described above for the same number of mesh
points.Comment: 29 pages, 4 figures, submitted to Phys. Rev.
Effects of Fermi surface and superconducting gap structure in the field-rotational experiments: A possible explanation of the cusp-like singularity in YNiBC
We have studied the field-orientational dependence of zero-energy density of
states (FODOS) for a series of systems with different Fermi surface and
superconducting gap structures. Instead of phenomenological Doppler-shift
method, we use an approximate analytical solution of Eilenberger equation
together with self-consistent determination of order parameter and a
variational treatment of vortex lattice. First, we compare zero-energy density
of states (ZEDOS) when a magnetic field is applied in the nodal direction
() and in the antinodal direction (), by taking
account of the field-angle dependence of order parameter. As a result, we found
that there exists a crossover magnetic field so that for for , consistent with our previous analyses. Next, we showed that and the
shape of FODOS are determined by contribution from the small part of Fermi
surface where Fermi velocity is parallel to field-rotational plane. In
particular, we found that is lowered and FODOS has broader minima, when a
superconducting gap has point nodes, in contrast to the result of the
Doppler-shift method. We also studied the effects of in-plane anisotropy of
Fermi surface. We found that in-plane anisotropy of quasi-two dimensional Fermi
surface sometimes becomes larger than the effects of Doppler-shift and can
destroy the Doppler-shift predominant region. In particular, this tendency is
strong in a multi-band system where superconducting coherence lengths are
isotropic. Finally, we addressed the problem of cusp-like singularity in
YNiBC and present a possible explanation of this phenomenon.Comment: 13pages, 23figure
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Sections for 6Li + 208Pb System at Near-Coulomb-Barrier Energies by using Folding Potential
Based on the extended optical model approach in which the polarization
potential is decomposed into direct reaction (DR) and fusion parts,
simultaneous analyses are performed for elastic scattering and
fusion cross section data for the Li+Pb system at
near-Coulomb-barrier energies. A folding potential is used as the bare
potential. It is found that the real part of the resultant DR part of the
polarization potential is repulsive, which is consistent with the results from
the Continuum Discretized Coupled Channel (CDCC) calculations and the
normalization factors needed for the folding potentials. Further, it is found
that both DR and fusion parts of the polarization potential satisfy separately
the dispersion relation.Comment: 6 figure
Acoustic Microscope Image from Round Shape Specimen
Due to high frequency of applying ultrasonics up to 1GHz, acoustic microscope has estimate microstructural features with higher resolving power comparing other acoustic methods in laboratories[1]~[5]. However in industrial fields, acoustic microscope have not widely applied now. One of the reason of it is that acoustic microscope can’t be measure round surface specimen because it has been developed as flat surface specimen measurement system which requires high accurate linear scanning of acoustic lens[5]
‘A Slow Build-Up of a History of Kindness’: Exploring the Potential of Community-Led Housing in Alleviating Loneliness
This article explores the potential of community-led housing (CLH) in combatting loneliness, and represents a mixed-methods research project carried out from just before the beginning of the pandemic, through 2020. Methods comprised a nationwide quantitative online survey of members of CLH groups (N = 221 respondents from England and Wales), followed by five case studies of communities representing a range of different CLH models. This qualitative element comprised participant observation, and semi-structured interviews at each group. The article also considers data from a smaller research project carried out by the same team in July 2020, that aimed to capture the experience of the pandemic for CLH groups, and comprising an online questionnaire followed by 18 semi-structured interviews. We conclude that members of CLH projects are measurably less lonely than those with comparable levels of social connection in wider society, and that such benefits are achieved through combinations of multiple different elements that include physical design, social design and through social processes. Notably, not all aspects of communities that contribute positively are a result of explicit intentionality, albeit the concept is considered key to at least one of the models
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