6,040 research outputs found
Enhancing efficiency of single, large-aperture antennas
Numerical analysis method provides means of describing energy distribution in focal plane of parabolic surface in terms of phase and wavelength. Two approaches for enhancing antenna efficiency include single, large reflector focused to feeding element, and array of smaller apertures whose individual outputs are summed
Hydrogen solubility in zirconium intermetallic second phase particles
The enthalpies of solution of H in Zr binary intermetallic compounds formed
with Cu, Cr, Fe, Mo, Ni, Nb, Sn and V were calculated by means of density
functional theory simulations and compared to that of H in {\alpha}-Zr. It is
predicted that all Zr-rich phases (formed with Cu, Fe, Ni and Sn), and those
phases formed with Nb and V, offer lower energy, more stable sites for H than
{\alpha}-Zr. Conversely, Mo and Cr containing phases do not provide
preferential solution sites for H. In all cases the most stable site for H are
those that offer the highest coordination fraction of Zr atoms. Often these are
four Zr tetrahedra but not always. Implications with respect to H-trapping
properties of commonly observed ternary phases such as Zr(Cr,Fe)2, Zr2(Fe,Ni)
and Zr(Nb,Fe)2 are also discussed.Comment: manuscript accepted for publication in Journal of Nuclear Materials
(2013
Test of nuclear level density inputs for Hauser-Feshbach model calculations
The energy spectra of neutrons, protons, and alpha-particles have been
measured from the d+59Co and 3He+58Fe reactions leading to the same compound
nucleus, 61$Ni. The experimental cross sections have been compared to
Hauser-Feshbach model calculations using different input level density models.
None of them have been found to agree with experiment. It manifests the serious
problem with available level density parameterizations especially those based
on neutron resonance spacings and density of discrete levels. New level
densities and corresponding Fermi-gas parameters have been obtained for
reaction product nuclei such as 60Ni,60Co, and 57Fe
Coupled phonon-ripplon modes in a single wire of electrons on the liquid-helium surface
The coupled phonon-ripplon modes of the quasi-one-dimensional electron chain
on the liquid helium sutface are studied. It is shown that the electron-ripplon
coupling leads to the splitting of the collective modes of the wire with the
appearance of low-frequency modes and high-frequency optical modes starting
from threshold frequencies. The effective masses of an electron plus the
associated dimple for low frequency modes are estimated and the values of the
threshold frequencies are calculated. The results obtained can be used in
experimental attempts to observe the phase transition of the electron wire into
a quasi-ordered phase.Comment: 5 pages, 1 figure, Physical Review (in press
Crew Motion and the Dynamic Environment of Spaceborne Experiments
Analytical study of crew motion on dynamic environment of orbiting laboratorie
Interplanetary communications study Final report
Mathematical expression for phase and amplitude distribution in focal plane of apertur
Extending HIV Prevention: People Living With HIV/AIDS (PLWHA) Strategize to Reduce Stigma and Promote HIV Testing
Strategies to reduce acquired immunodeficiency syndrome (AIDS)‐related stigma are paramount to promoting effective HIV prevention. As in the case of HIV antibody testing, despite the benefits of early detection, links to care, and risk behavior modification, nearly 250,000 people are unaware of their HIV status. AIDS‐related stigma has impeded such efforts due to discrimination, ignorance and other forms of stigma. These issues related to stigma and HIV testing are magnified when placed in the context of the rural Deep South region of the United States, where the incidence of HIV/AIDS are growing at alarming rates. The purpose of this paper was to examine strategies to reduce AIDS‐related stigma that in turn promotes HIV testing as proposed by people living with HIV/AIDS (PLWHA) who reside in the Deep South. An exploratory descriptive qualitative research design was utilized. The sample consisted of 18 PLWHA. Data was collected using a focus group and individual, semi‐structured interviews. The analysis revealed the importance of ongoing education as a mediator between reducing stigma and promoting HIV testing. Other salient findings were related to reframing HIV/AIDS‐related health messages to reflect a sense of empowerment; the need to normalize testing; the use of less stigmatizing testing sites; and the continuance of anonymous HIV testing. This article is significant because it illuminates the challenges of HIV prevention in the Deep South, while also generating culturally‐sensitive strategies to counter these barriers
Level density of Fe and low-energy enhancement of -strength function
The MnFe differential cross section is measured at
MeV\@. The Fe level density obtained from neutron evaporation spectra is
compared to the level density extracted from the
FeHe,Fe reaction by the Oslo-type technique.
Good agreement is found between the level densities determined by the two
methods. With the level density function obtained from the neutron evaporation
spectra, the Fe -strength function is also determined from the
first-generation matrix of the Oslo experiment. The good agreement
between the past and present results for the -strength function
supports the validity of both methods and is consistent with the low-energy
enhancement of the strength below MeV first discovered by the
Oslo method in iron and molybdenum isotopes.Comment: 7 pages, 5 figure
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