4,600 research outputs found
Investigations on the interaction between the low energy heavy ion beams and hydrogen plasma
The investigations on the interaction between
ion beam and matter is one of the most important
topics in atomic physics and nuclear physics. It is
indeed a requirement for a deeper understanding
of the interaction processes. Especially the energy
deposition by an intense heavy ion beam with the
low energy impinging into a degenerate matter,
which is related to the topics of warm dense
matter, fast ignition process and helium ions selfheating
in the fusion process..
Exact exchange-correlation potential of a ionic Hubbard model with a free surface
We use Lanczos exact diagonalization to compute the exact
exchange-correlation (xc) potential of a Hubbard chain with large binding
energy ("the bulk") followed by a chain with zero binding energy ("the
vacuum"). Several results of density functional theory in the continuum
(sometimes controversial) are verified in the lattice. In particular we show
explicitly that the fundamental gap is given by the gap in the Kohn-Sham
spectrum plus a contribution due to the jump of the xc-potential when a
particle is added. The presence of a staggered potential and a nearest-neighbor
interaction V allows to simulate a ionic solid. We show that in the ionic
regime in the small hopping amplitude limit the xc-contribution to the gap
equals V, while in the Mott regime it is determined by the Hubbard U
interaction. In addition we show that correlations generates a new potential
barrier at the surface
Simulation of heat transport in low-dimensional oscillator lattices
The study of heat transport in low-dimensional oscillator lattices presents a
formidable challenge. Theoretical efforts have been made trying to reveal the
underlying mechanism of diversified heat transport behaviors. In lack of a
unified rigorous treatment, approximate theories often may embody controversial
predictions. It is therefore of ultimate importance that one can rely on
numerical simulations in the investigation of heat transfer processes in
low-dimensional lattices. The simulation of heat transport using the
non-equilibrium heat bath method and the Green-Kubo method will be introduced.
It is found that one-dimensional (1D), two-dimensional (2D) and
three-dimensional (3D) momentum-conserving nonlinear lattices display power-law
divergent, logarithmic divergent and constant thermal conductivities,
respectively. Next, a novel diffusion method is also introduced. The heat
diffusion theory connects the energy diffusion and heat conduction in a
straightforward manner. This enables one to use the diffusion method to
investigate the objective of heat transport. In addition, it contains
fundamental information about the heat transport process which cannot readily
be gathered otherwise.Comment: Article published in: Thermal transport in low dimensions: From
statistical physics to nanoscale heat transfer, S. Lepri, ed. Lecture Notes
in Physics, vol. 921, pp. 239 - 274, Springer-Verlag, Berlin, Heidelberg, New
York (2016
Energy Deposition and Excitation of Wakefield in Case of 100keV/u Ion Beam Passing through a Plasma Target
Recently our team investigated the energy deposition
and excitation of wakefield in case of
hundreds keV proton/helium ion beams passing
a gas-discharged plasma target..
Test of detuning system for dielectronic recombination experiment at CSRm
The storage ring equipped with an electron cooler is an ideal platform for
dielectronic recombination (DR) experiments. In order to fulfil the requirement
of DR measurements at the main Cooler Storage Ring, a detuning system for the
precision control of the relative energy between the ion beam and the electron
beam has been installed on the electron cooler device. The test run using 7.0
MeV/u C6+ beam was performed to examine the influence of this system on the
performance of the stored ion beam. The Schottky spectra and the ion beam
currents were recorded to monitor the beam status. The influence of pulse
heights and widths of the detuning voltage on the ion beam was investigated.
For the small pulse height, the experimental results from the Schottky spectrum
were in good agreement with the theoretical results. The frequency shift in the
Schottky spectrum is significantly reduced for the short pulse width. For the
large pulse height, an oscillation phenomenon was observed. From the Schottky
spectrum, we found the oscillation amplitude is dependent on the pulse width of
detuning and the ion beam intensity. The detailed description of the phenomenon
and the theoretical model based on the plasma oscillation was discussed in this
paper.Comment: contributed to Chinese Physics
Towards a generalized vision of oxides: disclosing the role of cations and anions in determining unit-cell dimensions
Theoretical calculations of the electron-localization function show that, at the volumes of the two CaO phases (rocksalt and CsCl type), the parent Ca structures (fcc: face-centred cubic; sc: simple cubic) exhibit charge-concentration zones which coincide with the positions occupied by the O atoms in their oxides. For the first time, the structure type, dimension and topology of CaO and BaSnO3 are explained in univocal physical terms
Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials
Recent years witnessed a rapid growth of interest of scientific and
engineering communities to thermal properties of materials. Carbon allotropes
and derivatives occupy a unique place in terms of their ability to conduct
heat. The room-temperature thermal conductivity of carbon materials span an
extraordinary large range - of over five orders of magnitude - from the lowest
in amorphous carbons to the highest in graphene and carbon nanotubes. I review
thermal and thermoelectric properties of carbon materials focusing on recent
results for graphene, carbon nanotubes and nanostructured carbon materials with
different degrees of disorder. A special attention is given to the unusual size
dependence of heat conduction in two-dimensional crystals and, specifically, in
graphene. I also describe prospects of applications of graphene and carbon
materials for thermal management of electronics.Comment: Review Paper; 37 manuscript pages; 4 figures and 2 boxe
Simulation of dimensionality effects in thermal transport
The discovery of nanostructures and the development of growth and fabrication
techniques of one- and two-dimensional materials provide the possibility to
probe experimentally heat transport in low-dimensional systems. Nevertheless
measuring the thermal conductivity of these systems is extremely challenging
and subject to large uncertainties, thus hindering the chance for a direct
comparison between experiments and statistical physics models. Atomistic
simulations of realistic nanostructures provide the ideal bridge between
abstract models and experiments. After briefly introducing the state of the art
of heat transport measurement in nanostructures, and numerical techniques to
simulate realistic systems at atomistic level, we review the contribution of
lattice dynamics and molecular dynamics simulation to understanding nanoscale
thermal transport in systems with reduced dimensionality. We focus on the
effect of dimensionality in determining the phononic properties of carbon and
semiconducting nanostructures, specifically considering the cases of carbon
nanotubes, graphene and of silicon nanowires and ultra-thin membranes,
underlying analogies and differences with abstract lattice models.Comment: 30 pages, 21 figures. Review paper, to appear in the Springer Lecture
Notes in Physics volume "Thermal transport in low dimensions: from
statistical physics to nanoscale heat transfer" (S. Lepri ed.
Depression and Sexual Orientation During Young Adulthood: Diversity Among Sexual Minority Subgroups and the Role of Gender Nonconformity.
Sexual minority individuals are at an elevated risk for depression compared to their heterosexual counterparts, yet less is known about how depression status varies across sexual minority subgroups (i.e., mostly heterosexuals, bisexuals, and lesbians and gay men). Moreover, studies on the role of young adult gender nonconformity in the relation between sexual orientation and depression are scarce and have yielded mixed findings. The current study examined the disparities between sexual minorities and heterosexuals during young adulthood in concurrent depression near the beginning of young adulthood and prospective depression 6 years later, paying attention to the diversity within sexual minority subgroups and the role of gender nonconformity. Drawn from the National Longitudinal Study of Adolescent Health (N = 9421), we found that after accounting for demographics, sampling weight, and sampling design, self-identified mostly heterosexual and bisexual young adults, but not lesbians and gay men, reported significantly higher concurrent depression compared to heterosexuals; moreover, only mostly heterosexual young adults were more depressed than heterosexuals 6 years later. Furthermore, while young adult gender nonconforming behavior was associated with more concurrent depression regardless of sexual orientation, its negative impact on mental health decreased over time. Surprisingly, previous gender nonconformity predicted decreased prospective depression among lesbians and gay men whereas, among heterosexual individuals, increased gender nonconformity was not associated with prospective depression. Together, the results suggested the importance of investigating diversity and the influence of young adult gender nonconformity in future research on the mental health of sexual minorities.The authors acknowledge support for this research: the University of Arizona Norton School of Family and Consumer Sciences Fitch Nesbitt Endowment and a University of Arizona Graduate Access Fellowship to the second author. This research uses data from Add Health, a program project directed by Kathleen Mullan Harris and designed by J. Richard Udry, Peter S. Bearman, and Kathleen Mullan Harris at the University of North Carolina at Chapel Hill, and funded by grant P01-HD31921 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, with cooperative funding from 23 other federal agencies and foundations. Special acknowledgment is due Ronald R. Rindfuss and Barbara Entwisle for assistance in the original design. Information on how to obtain the Add Health data files is available on the Add Health website (http://www.cpc.unc.edu/addhealth). No direct support was received from grant P01-HD31921 for this analysis. The authors thank Noel Card and Susan Stryker for comments on the previous versions of this article and Richard Lippa and Katerina Sinclair for methodological and statistical consult. The authors also thank the anonymous reviewers and the Editor for their helpful comments.This is the accepted manuscript of a paper published in Archives of Sexual Behavior (Li G, Pollitt AM, Russell ST, Archives of Sexual Behavior 2015, doi:10.1007/s10508-015-0515-3). The final version is available at http://dx.doi.org/10.1007/s10508-015-0515-3
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