7,407 research outputs found
An Unusual Application of NASTRAN Contour Plotting Capability
A procedure is presented for obtaining contour plots of any physical quantity defined on a number of points of the surface of a structure. Rigid Format 1 of HEAT approach in Cosmic NASTRAN is ALTERED to enable use of contour plotting capability for scalar quantities. The ALTERED DMAP sequence is given. Examples include temperature distribution on the face of a cooled laser mirror and the angle of incidence or a radome surface
Constraining star formation rates in cool-core brightest cluster galaxies
We used broad-band imaging data for 10 cool-core brightest cluster galaxies
(BCGs) and conducted a Bayesian analysis using stellar population synthesis to
determine the likely properties of the constituent stellar populations.
Determination of ongoing star formation rates (SFRs), in particular, has a
direct impact on our understanding of the cooling of the intracluster medium
(ICM), star formation and AGN-regulated feedback. Our model consists of an old
stellar population and a series of young stellar components. We calculated
marginalized posterior probability distributions for various model parameters
and obtained 68% plausible intervals from them. The 68% plausible interval on
the SFRs is broad, owing to a wide range of models that are capable of fitting
the data, which also explains the wide dispersion in the star formation rates
available in the literature. The ranges of possible SFRs are robust and
highlight the strength in such a Bayesian analysis. The SFRs are correlated
with the X-ray mass deposition rates (the former are factors of 4 to 50 lower
than the latter), implying a picture where the cooling of the ICM is a
contributing factor to star formation in cool-core BCGs. We find that 9 out of
10 BCGs have been experiencing starbursts since 6 Gyr ago. While four out of 9
BCGs seem to require continuous SFRs, 5 out of 9 seem to require periodic star
formation on intervals ranging from 20 Myr to 200 Myr. This time scale is
similar to the cooling-time of the ICM in the central (< 5 kpc) regions.Comment: 33 pages, 14 Figures, 14 Tables. Accepted for publication in MNRA
The challenging task of determining star formation rates: the case of a massive stellar burst in the brightest cluster galaxy of Phoenix galaxy cluster
Star formation in galaxies at the center of cooling-flow galaxy clusters is
an important phenomenon in the context of formation and evolution of massive
galaxies in the Universe. Yet, star formation rates (SFRs) in such systems
continue to be elusive. We use our Bayesian-motivated spectral energy
distribution (SED)-fitting code, BAYESCOOL, to estimate the plausible SFR
values in the brightest cluster galaxy of a massive, X-ray luminous galaxy
cluster, Phoenix. Previous studies of Phoenix have resulted in the highest
measurement of SFR for any galaxy, with the estimates reaching up to 1000 solar
masses/yr. However, a very small number of models have been considered in those
studies. BAYESCOOL allows us to probe a large parameter space. We consider two
models for star formation history, instantaneous bursts and continuous star
formation, a wide range of ages for the old and the young stellar population,
along with other discrete parameters, such as the initial mass function,
metallicities, internal extinction and extinction law. We find that in the
absence of any prior except that the maximum cooling rate < 3000 solar
masses/yr, the SFR lies in the range (2230-2890) solar masses/yr. If we impose
an observational prior on the internal extinction, E(B-V) < 0.6, the best-fit
SFR lies in (454-494) solar masses/yr, and we consider this as the most
probable range of SFR values for Phoenix. The SFR dependence on the extinction
is a reflection of the standard age-extinction degeneracy, which can be
overcome by using a prior on one of the two quantities in question.Comment: 12 pages, 4 figures, 1 Table, accepted for publication in MNRA
Parallel finite element simulation of 3d incompressible flows: fluid-structure interactions
Massively parallel finite element computations of 3D, unsteady incompressible flows, including those involving fluid-structure interactions, are presented. The computation with time-varying spatial domains are based on the deforming spatial domain/stabilized space-time (DSD/SST) finite element formulation. The capability to solve 3D problems involving fluid-structure interactions is demonstrated by investigating the dynamics of a flexible cantilevered pipe conveying fluid. Computations of flow past a stationary rectangular wing at Reynolds number 1000, 2500 and 107 reveal interesting flow patterns. In these computations, at each time step approximately 3 × 106 non-linear equations are solved to update the flow field. Also, preliminary results are presented for flow past a wing in flapping motion. In this case a specially designed mesh moving scheme is employed to eliminate the need for remeshing. All these computations are carried out on the Army High Performance Computing Research Center supercomputers CM-200 and CM-5, with major speed-ups compared with traditional supercomputers. The coupled equation systems arising from the finite element discretizations of these large-scale problems are solved iteratively with diagonal preconditioners. In some cases, to reduce the memory requirements even further, these iterations are carried out with a matrix-free strategy. The finite element formulations and their parallel implementations assume unstructured meshes
Thermodynamics predicts how confinement modifies hard-sphere dynamics
We study how confining the equilibrium hard-sphere fluid to restrictive one-
and two-dimensional channels with smooth interacting walls modifies its
structure, dynamics, and entropy using molecular dynamics and transition-matrix
Monte Carlo simulations. Although confinement strongly affects local
structuring, the relationships between self-diffusivity, excess entropy, and
average fluid density are, to an excellent approximation, independent of
channel width or particle-wall interactions. Thus, thermodynamics can be used
to predict how confinement impacts dynamics.Comment: 4 pages, 4 figure
Batch and bulk adsorptive removal of anionic dye using metal/halide-free ordered mesoporous carbon as adsorbent
The authors are grateful to the Ministry of Human Resource Development of the Government of India for financial support through the SPARC Project- SPARC/2018–2019/P307/SL. One of the authors (Asna Mariyam) is also grateful to MANIT, Bhopal for providing fellowship assistance. We thank the University of St Andrews for a PhD scholarship for FS. We acknowledge EPSRC Strategic Resources Grant (EP/R023751/1).The present report is an outcome of investigations to assess the adsorptive potential of a synthesized metal- and halide-free variant of ordered mesoporous carbon (OMC) towards an anionic azo dye, Methyl Orange. The results of preliminary studies, carried out in batch mode, helped in setting up the process variables to achieve optimum adsorption conditions. The experimental data were then fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevitch isotherm models. The equilibrium data fitted well to the Langmuir model at 303 K and the monolayer adsorption capacity was 0.33 mmol g−1. The adsorption kinetics were explored by fitting the data to pseudo-first-order and pseudo-second-order kinetic models. The latter described the kinetics well, as indicated by higher regression coefficients. To elucidate the mechanism of mass transfer, various well-known mathematical models were employed. The adsorption of the dye was found to involve particle diffusion. Thermodynamic studies revealed that the adsorptive uptake of Methyl Orange by the OMC was spontaneous (ΔG0 = −23.71 kJ mol−1) and exergonic (ΔH0 = −123.15 kJ mol−1). Finally, the bulk removal of the anionic dye was investigated through column operations followed by column regeneration (desorption) studies. Column saturation of up to 96.55% could be realized. Values for dye recovery reached up to 93.26%. The column efficiency was then evaluated by carrying out three consecutive adsorption/desorption cycles. The results obtained indicated that the adsorbent has a good ability to eliminate Methyl Orange from wastewater, both in batch and column operations.PostprintPeer reviewe
Sync-DRAW: Automatic GIF Generation using Deep Recurrent Attentive Architectures
This paper introduces a novel approach for generating GIFs called Synchronized Deep Recurrent Attentive Writer (Sync-DRAW). Sync-DRAW employs a Recurrent Variational Autoencoder (R-VAE) and an attention mechanism in a hierarchical manner to create a temporally dependent sequence of frames that are gradually formed over time. The attention mechanism in Sync-DRAW attends to each individual frame of the GIF in sychronization, while the R-VAE learns a latent distribution for the entire GIF at the global level. We studied the performance of our Sync-DRAW network on the Bouncing MNIST GIFs Dataset and also, the newly available TGIF dataset. Experiments have suggested that Sync-DRAW is efficient in learning the spatial and temporal information of the GIFs and generates frames where objects have high structural integrity. Moreover, we also demonstrate that Sync-DRAW can be extended to even generate GIFs automatically given just text captions
Accuracy of computerized tomography in determining hepatic tumor size in patients receiving liver transplantation or resection
Computerized tomography (CT) of liver is used in oncologic practice for staging tumors, evaluating response to treatment, and screening patients for hepatic resection. Because of the impact of CT liver scan on major treatment decisions, it is important to assess its accuracy. Patients undergoing liver transplantation or resection provide a unique opportunity to test the accuracy of hepatic-imaging techniques by comparison of finding of preoperative CT scan with those at gross pathologic examination of resected specimens. Forty-one patients who had partial hepatic resection (34 patients) or liver transplantation (eight patients) for malignant (30 patients) or benign (11 patients) tumors were evaluable. Eight (47%) of 17 patients with primary malignant liver tumors, four (31%) of 13 patients with metastatic liver tumors, and two (20%) of 10 patients with benign liver tumors had tumor nodules in resected specimens that were not apparent on preoperative CT studies. These nodules varied in size from 0.1 to 1.6 cm. While 11 of 14 of these nodules were 1.0 cm. These results suggest that conventional CT alone may be insufficient to accurately determine the presence or absence of liver metastases, extent of liver involvement, or response of hepatic metastases to treatment
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