37,359 research outputs found
The effects of shock waves on meteorites Final report
Shock wave effects on iron and iron-nickel alloys in meteorites analyzed by phase diagrams and residual effects due to shock loadin
Liquid oil painting: Free and forced convection in an enclosure with mechanical and thermal forcing
A fluid dynamics video is linked to this article, which have been submitted
to the Gallery of Fluid Motion as part of the 65th American Physical Society
meeting of the Division of Fluid Dynamics, held in San Diego, California, USA,
over 17-20 November 2012. The video serves to visualize flows generated in a
rectangular enclosure that are subjected to both mechanical and thermal forcing
through a common horizontal boundary. This system exhibits features consistent
with either horizontal convection or lid-driven cavity flows depending on the
ratio between thermal and mechanical stirring, and three different cases are
visualized in the linked videos.Comment: 2 video files attached, 4 pages, 1 figure. This article is submitted
accompanying a video submitted to the Gallery of Fluid Motion as part of the
65th Division of Fluid Dynamics meeting of the American Physical Society
(17-20 November, San Diego, CA, USA
Pion Interferometry for Hydrodynamical Expanding Source with a Finite Baryon Density
We calculate the two-pion correlation function for an expanding hadron source
with a finite baryon density. The space-time evolution of the source is
described by relativistic hydrodynamics and the Hanbury-Brown-Twiss (HBT)
radius is extracted after effects of collective expansion and multiple
scattering on the HBT interferometry have been taken into account, using
quantum probability amplitudes in a path-integral formalism. We find that this
radius is substantially smaller than the HBT radius extracted from the
freeze-out configuration.Comment: 4 pages, 2 figure
A Probabilistic Linear Genetic Programming with Stochastic Context-Free Grammar for solving Symbolic Regression problems
Traditional Linear Genetic Programming (LGP) algorithms are based only on the
selection mechanism to guide the search. Genetic operators combine or mutate
random portions of the individuals, without knowing if the result will lead to
a fitter individual. Probabilistic Model Building Genetic Programming (PMB-GP)
methods were proposed to overcome this issue through a probability model that
captures the structure of the fit individuals and use it to sample new
individuals. This work proposes the use of LGP with a Stochastic Context-Free
Grammar (SCFG), that has a probability distribution that is updated according
to selected individuals. We proposed a method for adapting the grammar into the
linear representation of LGP. Tests performed with the proposed probabilistic
method, and with two hybrid approaches, on several symbolic regression
benchmark problems show that the results are statistically better than the
obtained by the traditional LGP.Comment: Genetic and Evolutionary Computation Conference (GECCO) 2017, Berlin,
German
The effect of legislation on the contractor's attitudes on solid waste reduction
It has been a difficult task to reduce and handle solid wastes generated from construction and demolition (C&D) activities in a number of countries. In Hong Kong, the C&D soHd wastes of which many of them are suitable for recycling land reclamation were typically disposed to landfills. Regarding this, in December 2005, a main piece of legislation regarding the C&D solid waste minimization namely the Construction Waste Disposal Charging Scheme (CWDCS) was enacted in Hong Kong. Since then disposal of C&D solid waste to public landfill sites has no longer been a 'free meal' for the contractors. While the government statistics indicate that the average quantity of C&D solid waste disposed to the public landfill has been tremendously decreased, disgraceful news about the illegal disposal of C&D waste by contractors have begun to mount. Some criticized that the illegal disposal was indeed driven by the legislation. It is because the legislation itself basically cannot solve the problems encountered by the contractors i.e. an effective solid waste reduction and management. As such, a behavioral change of solid waste disposal by the contractors has yet been noted. This study uses the enactment of the CWCS as a benchmark, and seeks to investigate [I] whether the Scheme has prompted the construction contractors to adopt C&D solid wastes reduction strategies in the construction projects; and [2] the effect of the strategy applied by the contractors on C&D solid waste reduction in their projects. A questionnaire survey was conducted. The analysed results based on the Pearson correlation analysis show that the enactment of the CWCS merely led the main contractors reorient their operational practices. Collaboration among project team members in C&D solid waste reduction remains inadequate. Recommendation in response to the research findings was suggested
Ion-acoustic solitary waves and shocks in a collisional dusty negative ion plasma
We study the effects of ion-dust collisions and ion kinematic viscosities on
the linear ion-acoustic instability as well as the nonlinear propagation of
small amplitude solitary waves and shocks (SWS) in a negative ion plasma with
immobile charged dusts. {The existence of two linear ion modes, namely the
`fast' and `slow' waves is shown, and their properties are analyzed in the
collisional negative ion plasma.} {Using the standard reductive perturbation
technique, we derive a modified Korteweg-de Vries-Burger (KdVB) equation which
describes the evolution of small amplitude SWS.} {The profiles of the latter
are numerically examined with parameters relevant for laboratory and space
plasmas where charged dusts may be positively or negatively charged.} It is
found that negative ion plasmas containing positively charged dusts support the
propagation of SWS with negative potential. However, the perturbations with
both positive and negative potentials may exist when dusts are negatively
charged. The results may be useful for the excitation of SWS in laboratory
negative ion plasmas as well as for observation in space plasmas where charged
dusts may be positively or negatively charged.Comment: 13 pages, 9 figures; To appear in Physical Review
Heavy flavor kinetics at the hadronization transition
We investigate the in-medium modification of the charmonium breakup processes
due to the Mott effect for light (pi, rho) and open-charm (D, D*)
quark-antiquark bound states at the chiral/deconfinement phase transition. The
Mott effect for the D-mesons effectively reduces the threshold for charmonium
breakup cross sections, which is suggested as an explanation of the anomalous
J/psi suppression phenomenon in the NA50 experiment. Further implications of
finite-temperature mesonic correlations for the hadronization of heavy flavors
in heavy-ion collisions are discussed.Comment: 4 pages, 2 figures, Contribution to SQM2001 Conference, submitted to
J. Phys.
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