782 research outputs found
An experimental investigation of natural convection with solidification in a differentially heated cavity
This paper introduces an experimental rig used to produce data for the validation of computational models of natural convection within water in an enclosed cavity. The rig consisted of a rectangular cavity with the two long sides maintained at constant temperature. All other surfaces were insulated and adiabatic except for the top surface which was a free surface with an air gap between the free surface and the insulation. Experimental data in the form of velocity, ice growth rate and profiles are presented at 30 min time steps with a cold wall temperature of −10 °C and hot wall temperature of 5 °C. The data produced has systematic and random errors of ±0.4% and ±0.5%, respectively
Search for a Standard Model Higgs Boson in CMS via Vector Boson Fusion in the H->WW->l\nu l\nu Channel
We present the potential for discovering the Standard Model Higgs boson
produced by the vector-boson fusion mechanism. We considered the decay of Higgs
bosons into the W+W- final state, with both W-bosons subsequently decaying
leptonically. The main background is ttbar with one or more jets produced. This
study is based on a full simulation of the CMS detector, and up-to-date
reconstruction codes. The result is that a signal of 5 sigma significance can
be obtained with an integrated luminosity of 12-72 1/fb for Higgs boson masses
between 130-200 GeV. In addition, the major background can be measured directly
to 7% from the data with an integrated luminosity of 30 1/fb. In this study, we
also suggested a method to obtain information in Higgs mass using the
transverse mass distributions.Comment: 26 pages, 22 figure
Nab: Measurement Principles, Apparatus and Uncertainties
The Nab collaboration will perform a precise measurement of 'a', the
electron-neutrino correlation parameter, and 'b', the Fierz interference term
in neutron beta decay, in the Fundamental Neutron Physics Beamline at the SNS,
using a novel electric/magnetic field spectrometer and detector design. The
experiment is aiming at the 10^{-3} accuracy level in (Delta a)/a, and will
provide an independent measurement of lambda = G_A/G_V, the ratio of
axial-vector to vector coupling constants of the nucleon. Nab also plans to
perform the first ever measurement of 'b' in neutron decay, which will provide
an independent limit on the tensor weak coupling.Comment: 12 pages, 6 figures, 1 table, talk presented at the International
Workshop on Particle Physics with Slow Neutrons, Grenoble, 29-31 May 2008; to
appear in Nucl. Instrum. Meth. in Physics Research
Supersymmetry in carbon nanotubes in a transverse magnetic field
Electron properties of Carbon nanotubes in a transverse magnetic field are
studied using a model of a massless Dirac particle on a cylinder. The problem
possesses supersymmetry which protects low energy states and ensures stability
of the metallic behavior in arbitrarily large fields. In metallic tubes we find
suppression of the Fermi velocity at half-filling and enhancement of the
density of states. In semiconducting tubes the energy gap is suppressed. These
features qualitatively persist (although to a smaller degree) in the presence
of electron interactions. The possibilities of experimental observation of
these effects are discussed.Comment: A new section on electron interaction effects added and explanation
on roles of supersymmetry expanded. Revtex4, 6 EPS figure file
Higgs Physics in the Large N limit
In this paper we study the large N limit of the Standard Model Higgs sector
with , and constant and being the number of
would-be Goldstone bosons. Despite the simplicity of this method at leading
order, its results satisfy simultaneously important requirements such as
unitarity and the low-energy theorems in contrast with other more conventional
approaches. Moreover, it is fully compatible with the Equivalence Theorem and
it yields a consistent description of the Higgs boson mass and width. Finally
we have also included a phenomenological discussion concerning the applications
of this method to the LHC.Comment: 15 pages, 5 Figures, 3 .EPS files. Available at
http://www-physics.lbl.gov/www/theorypapers/preprints.htm
Regression Error Characteristic Optimisation of Non-Linear Models.
Copyright © 2006 Springer-Verlag Berlin Heidelberg. The final publication is available at link.springer.comBook title: Multi-Objective Machine LearningIn this chapter recent research in the area of multi-objective optimisation of regression models is presented and combined. Evolutionary multi-objective optimisation techniques are described for training a population of regression models to optimise the recently defined Regression Error Characteristic Curves (REC). A method which meaningfully compares across regressors and against benchmark models (i.e. ‘random walk’ and maximum a posteriori approaches) for varying error rates. Through bootstrapping training data, degrees of confident out-performance are also highlighted
Astrophysical Axion Bounds
Axion emission by hot and dense plasmas is a new energy-loss channel for
stars. Observational consequences include a modification of the solar
sound-speed profile, an increase of the solar neutrino flux, a reduction of the
helium-burning lifetime of globular-cluster stars, accelerated white-dwarf
cooling, and a reduction of the supernova SN 1987A neutrino burst duration. We
review and update these arguments and summarize the resulting axion
constraints.Comment: Contribution to Axion volume of Lecture Notes in Physics, 20 pages, 3
figure
Effects of plant population density on cabbage (Brassica oleracea var. capitata L.) crop
Com a finalidade de avaliar o efeito da densidade de população de plantas sobre a cultura de repolho (Brassica cleraoea var, capitata L.), foi realizado um experimento no Campo Experimental do Setor de Horticultura da Escola Superior de Agricultura "Luiz de Queiroz", Piracicaba, São Paulo, em um Latossol Roxo, Série Luiz de Queiroz, utilizando-se os espaçamentos de 0,60 mx 0,80 m; 0,60 m x 0,65 m; 0,60 m x 0,45 m; 0,60 m x 0,30 m e 0,60 m x 0,15 m. À medida em que se aumentou a densidade de população, houve as seguintes alterações na planta de repolho: mudança de for mato chato da "cabeça" para cônico, redução do numero de folhas, tamanho (peso, volume e diâmetros transversal e longitudinal) , aumento na densidade da "cabeça" (peso/volume) e aumento na porcentagem de plantas que não produziram "cabeça.In order to study the effects of plant population density on cabbage crop (Brassica oleracea var-. capitata), an experiment using different spacing (0,60 m x 0.80 m, 0.60 m x 0.65 m, 0.60mx0.45m, 0.60 m x 0.30 m, and 0.60mx 0.15m) was carried out. There were the following changes in cabbage plants due to increasing population density: plant head became conical: number and size (weight, volume and diameters) of leaves decreased; density (weight/volume) and percentage of plants forming no head increased
Anomalous Heat Conduction and Anomalous Diffusion in Low Dimensional Nanoscale Systems
Thermal transport is an important energy transfer process in nature. Phonon
is the major energy carrier for heat in semiconductor and dielectric materials.
In analogy to Ohm's law for electrical conductivity, Fourier's law is a
fundamental rule of heat transfer in solids. It states that the thermal
conductivity is independent of sample scale and geometry. Although Fourier's
law has received great success in describing macroscopic thermal transport in
the past two hundreds years, its validity in low dimensional systems is still
an open question. Here we give a brief review of the recent developments in
experimental, theoretical and numerical studies of heat transport in low
dimensional systems, include lattice models, nanowires, nanotubes and
graphenes. We will demonstrate that the phonon transports in low dimensional
systems super-diffusively, which leads to a size dependent thermal
conductivity. In other words, Fourier's law is breakdown in low dimensional
structures
Active Brownian Particles. From Individual to Collective Stochastic Dynamics
We review theoretical models of individual motility as well as collective
dynamics and pattern formation of active particles. We focus on simple models
of active dynamics with a particular emphasis on nonlinear and stochastic
dynamics of such self-propelled entities in the framework of statistical
mechanics. Examples of such active units in complex physico-chemical and
biological systems are chemically powered nano-rods, localized patterns in
reaction-diffusion system, motile cells or macroscopic animals. Based on the
description of individual motion of point-like active particles by stochastic
differential equations, we discuss different velocity-dependent friction
functions, the impact of various types of fluctuations and calculate
characteristic observables such as stationary velocity distributions or
diffusion coefficients. Finally, we consider not only the free and confined
individual active dynamics but also different types of interaction between
active particles. The resulting collective dynamical behavior of large
assemblies and aggregates of active units is discussed and an overview over
some recent results on spatiotemporal pattern formation in such systems is
given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte
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