1,786 research outputs found
Performance Based Plastic Design of Concentrically Braced Frame attuned with Indian Standard code and its Seismic Performance Evaluation
In the Performance Based Plastic design method, the failure is predetermined; making it famous throughout the world. But due to lack of proper guidelines and simple stepwise methodology, it is not quite popular in India. In this paper, stepwise design procedure of Performance Based Plastic Design of Concentrically Braced frame attuned with the Indian Standard code has been presented. The comparative seismic performance evaluation of a six storey concentrically braced frame designed using the displacement based Performance Based Plastic Design (PBPD) method and currently used force based Limit State Design (LSD) method has also been carried out by nonlinear static pushover analysis and time history analysis under three different ground motions. Results show that Performance Based Plastic Design method is superior to the current design in terms of displacement and acceleration response. Also total collapse of the frame is prevented in the PBPD frame
A New Survey for Giant Arcs
We report on the first results of an imaging survey to detect strong
gravitational lensing targeting the richest clusters selected from the
photometric data of the Sloan Digital Sky Survey (SDSS) with follow-up deep
imaging observations from the Wisconsin Indiana Yale NOAO (WIYN) 3.5m telescope
and the University of Hawaii 88-inch telescope (UH88). The clusters are
selected from an area of 8000 deg^2 using the Red Cluster Sequence technique
and span the redshift range 0.1 < z < 0.6, corresponding to a comoving
cosmological volume of ~ 2 Gpc^3. Our imaging survey thus targets a volume more
than an order of magnitude larger than any previous search. A total of 240
clusters were imaged of which 141 had sub-arcsecond image quality. Our survey
has uncovered16 new lensing clusters with definite giant arcs, an additional 12
systems for which the lensing interpretation is very likely, and 9 possible
lenses which contain shorter arclets or candidate arcs which are less certain
and will require further observations to confirm their lensing origin. The
number of new cluster lenses detected in this survey is likely > 30. Among
these new systems are several of the most dramatic examples of strong
gravitational lensing ever discovered with multiple bright arcs at large
angular separation. These will likely become 'poster-child' gravitational
lenses similar to Abell 1689 and CL0024+1654. The new lenses discovered in this
survey will enable future sysetmatic studies of the statistics of strong
lensing and its implications for cosmology and our structure formation
paradigm.Comment: 19 pages, 7 pages of Figures, submitted to AJ. Fixed Typo
Detection of lensing substructure using ALMA observations of the dusty galaxy SDP.81
We study the abundance of substructure in the matter density near galaxies
using ALMA Science Verification observations of the strong lensing system
SDP.81. We present a method to measure the abundance of subhalos around
galaxies using interferometric observations of gravitational lenses. Using
simulated ALMA observations, we explore the effects of various systematics,
including antenna phase errors and source priors, and show how such errors may
be measured or marginalized. We apply our formalism to ALMA observations of
SDP.81. We find evidence for the presence of a
subhalo near one of the images, with a significance of in a joint
fit to data from bands 6 and 7; the effect of the subhalo is also detected in
both bands individually. We also derive constraints on the abundance of dark
matter subhalos down to , pushing down to the
mass regime of the smallest detected satellites in the Local Group, where there
are significant discrepancies between the observed population of luminous
galaxies and predicted dark matter subhalos. We find hints of additional
substructure, warranting further study using the full SDP.81 dataset
(including, for example, the spectroscopic imaging of the lensed carbon
monoxide emission). We compare the results of this search to the predictions of
CDM halos, and find that given current uncertainties in the host halo
properties of SDP.81, our measurements of substructure are consistent with
theoretical expectations. Observations of larger samples of gravitational
lenses with ALMA should be able to improve the constraints on the abundance of
galactic substructure.Comment: 18 pages, 13 figures, Comments are welcom
A Racist Attack Managing Complex Relationships with Traumatised Service Users – a Psychodynamic Approach
Notions of whiteness, white supremacy and racial hatred such as the recent multiple racist murders by a white supremacist in New Zealand are at the forefront of public consciousness. How does whiteness and racism play out in a clinical and social welfare context? This article illustrates the impact of trauma on a vulnerable young white woman who although was not the direct target of a racist assault was left traumatized by witnessing it. It discusses how initially she sought refuge in a racist solution synonymous with a psychic retreat to her own detriment. Working with such complex, unconscious and bewildering dynamics are extremely challenging for clinicians. It describes the impact of these dynamics on a clinician of colour who attempted to work with this young woman in a child and adolescent mental health service after the family were referred as a consequence of her assaulting her child shortly after witnessing the racist attack. The unconscious responses to trauma and challenges for clinicians and clinician of colour in particular when working with racism in the consulting room are also discussed
AC susceptibility and V NMR study of MnVO
We report V zero-field NMR of manganese vanadate spinel of
MnVO, together with both ac and dc magnetization measurements. The
field and temperature dependence of ac susceptibilities show a
reentrant-spin-glass-like behavior below the ferrimagnetic(FEM) ordering
temperature. The zero-field NMR spectrum consists of multiple lines ranging
from 240 MHz to 320 MHz. Its temperature dependence reveals that the ground
state is given by the simultaneous formation of a long-range FEM order and a
short-range order component. We attribute the spin-glass-like anomalies to
freezing and fluctuations of the short-range ordered state caused by the
competition between spin and orbital ordering of the V site
Dark Matter Structures in the Universe: Prospects for Optical Astronomy in the Next Decade
The Cold Dark Matter theory of gravitationally-driven hierarchical structure
formation has earned its status as a paradigm by explaining the distribution of
matter over large spans of cosmic distance and time. However, its central
tenet, that most of the matter in the universe is dark and exotic, is still
unproven; the dark matter hypothesis is sufficiently audacious as to continue
to warrant a diverse battery of tests. While local searches for dark matter
particles or their annihilation signals could prove the existence of the
substance itself, studies of cosmological dark matter in situ are vital to
fully understand its role in structure formation and evolution. We argue that
gravitational lensing provides the cleanest and farthest-reaching probe of dark
matter in the universe, which can be combined with other observational
techniques to answer the most challenging and exciting questions that will
drive the subject in the next decade: What is the distribution of mass on
sub-galactic scales? How do galaxy disks form and bulges grow in dark matter
halos? How accurate are CDM predictions of halo structure? Can we distinguish
between a need for a new substance (dark matter) and a need for new physics
(departures from General Relativity)? What is the dark matter made of anyway?
We propose that the central tool in this program should be a wide-field optical
imaging survey, whose true value is realized with support in the form of
high-resolution, cadenced optical/infra-red imaging, and massive-throughput
optical spectroscopy.Comment: White paper submitted to the 2010 Astronomy & Astrophysics Decadal
Surve
Towards the theory of ferrimagnetism
Two-sublattice ferrimagnet, with spin- operators at the
sublattice site and spin- operators at the sublattice
site, is considered. The magnon of the system, the transversal fluctuation
of the total magnetization, is a complicate mixture of the transversal
fluctuations of the sublattice and spins. As a result, the magnons'
fluctuations suppress in a different way the magnetic orders of the and
sublattices and one obtains two phases. At low temperature the
magnetic orders of the and spins contribute to the magnetization of the
system, while at the high temperature , the magnetic order of the
spins with a weaker intra-sublattice exchange is suppressed by magnon
fluctuations, and only the spins with stronger intra-sublattice exchange has
non-zero spontaneous magnetization. The transition is a transition
between two spin-ordered phases in contrast to the transition from spin-ordered
state to disordered state (-transition). There is no additional symmetry
breaking, and the Goldstone boson has a ferromagnetic dispersion in both
phases. A modified spin-wave theory is developed to describe the two phases.
All known Neel's anomalous curves are reproduced, in particular that
with "compensation point". The theoretical curves are compared with
experimental ones for sulpho-spinel and rare earth iron
garnets.Comment: 9 pages, 8 figure
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