5,922 research outputs found
Advanced superalloy protection systems evaluation Final report
Metalliding parameters developed for sequential deposition of manganese, aluminum, and tantalum alloys as protective coatings for superalloy
GATE convection subprogramme: field phase report
Assisted by J. L. Rasmussen and W. Murray of the U.S. GATE Project Office.February, 1975.Includes bibliographical references.A summary of the in-field decisions affecting the GATE Convection Subprogramme (C.S.P.) objectivesa preliminary tabulation and discussion of the data collectionand a discussion of the work of the Special Analysis Group in Dakar. Preliminary tables are presented of the upper air data coverage for the B and A/B ship arrays, the C-band ship radars, the SMS satellite coverage and the multi-aircraft missions flown in support of the C.S.P.A preliminary assessment of the subprogramme observational objectives is given
Analytical sun synchronous low-thrust manoeuvres
Article describes analytical sun synchronous low-thrust manoeuvres
Interaction effects and quantum phase transitions in topological insulators
We study strong correlation effects in topological insulators via the Lanczos
algorithm, which we utilize to calculate the exact many-particle ground-state
wave function and its topological properties. We analyze the simple,
noninteracting Haldane model on a honeycomb lattice with known topological
properties and demonstrate that these properties are already evident in small
clusters. Next, we consider interacting fermions by introducing repulsive
nearest-neighbor interactions. A first-order quantum phase transition was
discovered at finite interaction strength between the topological band
insulator and a topologically trivial Mott insulating phase by use of the
fidelity metric and the charge-density-wave structure factor. We construct the
phase diagram at as a function of the interaction strength and the
complex phase for the next-nearest-neighbor hoppings. Finally, we consider the
Haldane model with interacting hard-core bosons, where no evidence for a
topological phase is observed. An important general conclusion of our work is
that despite the intrinsic nonlocality of topological phases their key
topological properties manifest themselves already in small systems and
therefore can be studied numerically via exact diagonalization and observed
experimentally, e.g., with trapped ions and cold atoms in optical lattices.Comment: 13 pages, 12 figures. Published versio
Triggering Deep Convection with a Probabilistic Plume Model
A model unifying the representation of the planetary boundary layer and dry, shallow and deep convection, the Probabilistic Plume Model (PPM), is presented. Its capacity to reproduce the triggering of deep convection over land is analysed in detail. The model accurately reproduces the timing of shallow convection and of deep convection onset over land, which is a major issue in many current general climate models.
The PPM is based on a distribution of plumes with varying thermodynamic states (potential temperature and specific humidity) induced by surface layer turbulence. Precipitation is computed by a simple ice microphysics, and with the onset of precipitation, downdrafts are initiated and lateral entrainment of environmental air into updrafts is reduced.
The most buoyant updrafts are responsible for the triggering of moist convection, causing the rapid growth of clouds and precipitation. Organization of turbulence in the subcloud layer is induced by unsaturated downdrafts, and the effect of density currents is modeled through a reduction of the lateral entrainment. The reduction of entrainment induces further development from the precipitating congestus phase to full deep cumulonimbus.
Model validation is performed by comparing cloud base, cloud top heights, timing of precipitation and environmental profiles against cloud resolving models and large-eddy simulations for two test cases. These comparisons demonstrate that PPM triggers deep convection at the proper time in the diurnal cycle, and produces reasonable precipitation. On the other hand, PPM underestimates cloud top height
Adolescents' experiences of street harassment: creating a typology and assessing the emotional impact
Purpose: Research examining young people's experiences of harassment has tended to focus on the school and digital environment. Despite street harassment being identified as a common experience for adult women, very few studies have explored adolescents' experiences of street harassment.
Methodology: A person centred analytical approach, based on experienced reporting, was used to create a typology of street harassment. Reports of street harassment were received from 118 (68 female, 43 male, 7 no gender reported) 11- to 15-year-olds over a 6 to 8 week period.
Findings: Cluster analysis revealed four distinct groups: "predominately verbal", "non-verbal/non-direct", "other incident", and "all forms". Young women and those in the "all forms" group reported experiencing greater negative emotions following the episode of street harassment. Young men were equally as likely as young women to report experiencing street harassment.
Value: The findings uniquely highlight that adolescents experience distinct types of street harassment and some of which are associated with negative emotions
Spin-1/2 J1-J2 model on the body-centered cubic lattice
Using exact diagonalization (ED) and linear spin wave theory (LSWT) we study
the influence of frustration and quantum fluctuations on the magnetic ordering
in the ground state of the spin-1/2 J1-J2 Heisenberg antiferromagnet (J1-J2
model) on the body-centered cubic (bcc) lattice. Contrary to the J1-J2 model on
the square lattice, we find for the bcc lattice that frustration and quantum
fluctuations do not lead to a quantum disordered phase for strong frustration.
The results of both approaches (ED, LSWT) suggest a first order transition at
J2/J1 0.7 from the two-sublattice Neel phase at low J2 to a collinear
phase at large J2.Comment: 6.1 pages 7 figure
A modelling approach for long-term degradation of thin film silicon photovoltaic modules
This paper introduces a new concept of approach
for modelling the ageing behaviour of a-Si PV
modules with voltage-dependent photocurrent.
The basis is the equivalent circuit of a PV module,
specifically the modified single diode model. The
parameters are extracted from I-V measurements.
Ageing is then analysed by relating these to the
environmental stresses seen by the devices. This
paper focuses on the behaviour the product of
carrier mobility and carrier life time (ÎŒÏ), since the
ÎŒÏ has been considered to be an important
indicator for module degradation of amorphous
silicon thin film devices. A fitting approach for
determining ÎŒÏ is discussed and extended to be
applied to the outdoor module IV data. Three a-Si
modules of the same type operating under
different temperature conditions are analysed to
identify changes in the ÎŒT
The role of parental alcohol use, parental discipline and antisocial behaviour on adolescent drinking trajectories
Backgrounds: : Parental drinking, harsh parental discipline and adolescent antisocial behaviour have been independently implicated in adolescent alcohol use. Robust prospective studies are required to examine developmental relationships between these factors and their effect on trajectories of alcohol use across adolescence
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