23,010 research outputs found
GMAW shielding gas flow optimisation by refinement of nozzle geometry
With an ongoing demand to improve the efficiency of the gas metal arc welding process, steps are being taken to reduce the shielding gas consumption. However, sufficient shielding gas coverage of the weld region is essential for the generation of high quality welds, and drafts can be detrimental to its efficiency. In industry, the general practise to ensure coverage is to increase the shielding gas flow rate, however, too high a flow rate can induce undesirable turbulence in the shielding gas column, whilst adding unnecessary cost to the process. A simplified computational fluid dynamics model has been generated, and validated through extensive experimental trials, to accurately model the shielding gas flow when subjected to the adverse effects of cross drafts. Several nozzle geometry changes have been investigated with the aim of improving the shielding gas column’s resistance to drafts, eliminating the requirement to increase the shielding gas flow rate
Deuteron production and elliptic flow in relativistic heavy ion collisions
The hadronic transport model \textsc{art} is extended to include the
production and annihilation of deuterons via the reactions , where and stand for baryons and mesons, respectively, as well as
their elastic scattering with mesons and baryons in the hadronic matter. This
new hadronic transport model is then used to study the transverse momentum
spectrum and elliptic flow of deuterons in relativistic heavy ion collisions,
with the initial hadron distributions after hadronization of produced
quark-gluon plasma taken from a blast wave model. The results are compared with
those measured by the PHENIX and STAR Collaborations for Au+Au collisions at
GeV, and also with those obtained from the coalescence
model based on freeze-out nucleons in the transport model.Comment: 9 pages, 10 figures, REVTeX, version to be published in Phys. Rev.
Pediatric asthma and autism-genomic perspectives.
High-throughput technologies, ranging from microarrays to NexGen sequencing of RNA and genomic DNA, have opened new avenues for exploration of the pathobiology of human disease. Comparisons of the architecture of the genome, identification of mutated or modified sequences, and pre-and post- transcriptional regulation of gene expression as disease specific biomarkers are revolutionizing our understanding of the causes of disease and are guiding the development of new therapies. There is enormous heterogeneity in types of genomic variation that occur in human disease. Some are inherited, while others are the result of new somatic or germline mutations or errors in chromosomal replication. In this review, we provide examples of changes that occur in the human genome in two of the most common chronic pediatric disorders, autism and asthma. The incidence and economic burden of both of these disorders are increasing worldwide. Genomic variations have the potential to serve as biomarkers for personalization of therapy and prediction of outcomes
Charm meson production from meson-nucleon scattering
Using an effective hadronic Lagrangian with physical hadron masses and
coupling constants determined either empirically or from SU(4) flavor symmetry,
we study the production cross sections of charm mesons from pion and rho meson
interactions with nucleons. With a cutoff parameter of 1 GeV at interaction
vertices as usually used in studying the cross sections for absorption
and charm meson scattering by hadrons, we find that the cross sections for
charm meson production have values of a few tenth of mb and are dominated by
the s channel nucleon pole diagram. Relevance of these reactions to charm meson
production in relativistic heavy ion collisions is discussed.Comment: 8 pages, 4 figures, slight revision and references adde
Charmonium Absorption in the Meson-exchange Model
We review the meson-exchange model for charmonium absorption by hadrons. This
includes the construction of the interaction Lagrangians, the determination of
the coupling constants, the introduction of form factors, and the predicted
cross sections for absorption by both mesons and nucleons. We further
discuss the effects due to anomalous parity interactions, uncertainties in form
factors, constraints from chiral symmetry, and the change of charmed meson mass
in medium on the cross sections for charmonium absorption in hadronic matter.Comment: 10 pages, 2 figures. Talk given at Quark Matter 2002 (QM 2002),
Nantes, France, 18-24 July 2002. To appear in the proceedings (Nucl. Phys. A
Violating Bell Inequalities Maximally for Two -Dimensional Systems
We investigate the maximal violation of Bell inequalities for two
-dimensional systems by using the method of Bell operator. The maximal
violation corresponds to the maximal eigenvalue of the Bell operator matrix.
The eigenvectors corresponding to these eigenvalues are described by asymmetric
entangled states. We estimate the maximum value of the eigenvalue for large
dimension. A family of elegant entangled states that violate
Bell inequality more strongly than the maximally entangled state but are
somewhat close to these eigenvectors is presented. These approximate states can
potentially be useful for quantum cryptography as well as many other important
fields of quantum information.Comment: 6 pages, 1 figure. Revised versio
A unified approach for exactly solvable potentials in quantum mechanics using shift operators
We present a unified approach for solving and classifying exactly solvable
potentials. Our unified approach encompasses many well-known exactly solvable
potentials. Moreover, the new approach can be used to search systematically for
a new class of solvable potentials.Comment: RevTex, 8 page
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