1,261 research outputs found
Reaction Time and Mortality from the Major Causes of Death:The NHANES-III Study
Studies examining the relation of information processing speed, as measured by reaction time, with mortality are scarce. We explored these associations in a representative sample of the US population
The Network Analysis of Urban Streets: A Primal Approach
The network metaphor in the analysis of urban and territorial cases has a
long tradition especially in transportation/land-use planning and economic
geography. More recently, urban design has brought its contribution by means of
the "space syntax" methodology. All these approaches, though under different
terms like accessibility, proximity, integration,connectivity, cost or effort,
focus on the idea that some places (or streets) are more important than others
because they are more central. The study of centrality in complex
systems,however, originated in other scientific areas, namely in structural
sociology, well before its use in urban studies; moreover, as a structural
property of the system, centrality has never been extensively investigated
metrically in geographic networks as it has been topologically in a wide range
of other relational networks like social, biological or technological. After
two previous works on some structural properties of the dual and primal graph
representations of urban street networks (Porta et al. cond-mat/0411241;
Crucitti et al. physics/0504163), in this paper we provide an in-depth
investigation of centrality in the primal approach as compared to the dual one,
with a special focus on potentials for urban design.Comment: 19 page, 4 figures. Paper related to the paper "The Network Analysis
of Urban Streets: A Dual Approach" cond-mat/041124
Surface tension in a compressible liquid-drop model: Effects on nuclear density and neutron skin thickness
We examine whether or not the surface tension acts to increase the nucleon
density in the nuclear interior within a compressible liquid-drop model. We
find that it depends on the density dependence of the surface tension, which
may in turn be deduced from the neutron skin thickness of stable nuclei.Comment: 4 pages, 1 figure, to be published in Physical Review
Analysis of bulk and surface contributions in the neutron skin of nuclei
The neutron skin thickness of nuclei is a sensitive probe of the nuclear
symmetry energy having multiple implications for nuclear and astrophysical
studies. However, precision measurements of this observable are difficult. The
analysis of the experimental data may imply some assumptions about the bulk or
surface nature of the formation of the neutron skin. Here, we study the bulk or
surface character of neutron skins of nuclei following from calculations with
Gogny, Skyrme, and covariant nuclear mean-field interactions. These
interactions are successful in describing nuclear charge radii and binding
energies but predict different values for neutron skins. We perform the study
by fitting two-parameter Fermi distributions to the calculated self-consistent
neutron and proton densities. We note that the equivalent sharp radius is a
more suitable reference quantity than the half-density radius parameter of the
Fermi distributions to discern between the bulk and surface contributions in
neutron skins. We present calculations for nuclei in the stability valley and
for the isotopic chains of Sn and Pb.Comment: 13 pages, 9 figure
Analysis of bulk and surface contributions in the neutron skin of nuclei
The neutron skin thickness of nuclei is a sensitive probe of the nuclear
symmetry energy having multiple implications for nuclear and astrophysical
studies. However, precision measurements of this observable are difficult. The
analysis of the experimental data may imply some assumptions about the bulk or
surface nature of the formation of the neutron skin. Here, we study the bulk or
surface character of neutron skins of nuclei following from calculations with
Gogny, Skyrme, and covariant nuclear mean-field interactions. These
interactions are successful in describing nuclear charge radii and binding
energies but predict different values for neutron skins. We perform the study
by fitting two-parameter Fermi distributions to the calculated self-consistent
neutron and proton densities. We note that the equivalent sharp radius is a
more suitable reference quantity than the half-density radius parameter of the
Fermi distributions to discern between the bulk and surface contributions in
neutron skins. We present calculations for nuclei in the stability valley and
for the isotopic chains of Sn and Pb.Comment: 13 pages, 9 figure
Pion-Lambda-Sigma Coupling Extracted from Hyperonic Atoms
The latest measurements of the atomic level width in Sigma-hyperonic Pb atom
offer the most accurate datum in the region of low-energy Sigma-hyperon
physics. Atomic widths are due to the conversion of Sigma-nucleon into
Lambda-nucleon. In high angular momentum states this conversion is dominated by
the one-pion exchange. A joint analysis of the data of the scattering of
negative-Sigma on proton converting into a Lambda and a neutron and of the
atomic widths allows to extract a pseudovector pion-hyperon-Sigma coupling
constant of 0.048 with a statistical error of +-0.005 and a systematic one of
+-0.004. This corresponds to a pseudoscalar coupling constant of 13.3 with a
statistical uncertainty of 1.4 and a systematic one of 1.1.Comment: 12 pages, 1 figure, Use of Revtex.st
Understanding aesthetic appreciation as an aid to the development of sustainable urban environment
Sustainable management of the existing built environment is becoming increasingly important in the construction industry. Consequently, more emphasis has emerged to consider issues of refurbishment and renovation. The aesthetic values of buildings are recognised as critical guiding attributes both in terms of the potential long-term aspects of sustainability and as basic reasoning for the continued maintenance and management of existing buildings. A process is required that will allow different aspects of a potential refurbishment project to be assessed objectively and weighted equally when deciding whether an existing building should be preserved, adapted or demolished. The thesis attempts to provide a useful understanding in terms of the aesthetic appreciation when considering future sustainable management of the existing built environment. Two parallel research activities were initiated to examine important aspects of human aesthetic perception regarding buildings in the built environment. The first addressed the potentially universal and culturally derived aspects of human responses in perceiving the aesthetic qualities of houses from 3 counties through the agency of colour photographs. A three language semantic differential scale was developed to be linguistically equivalent so that an inter-cultural research tool could be derived to ascertain an understanding of people’s aesthetic appreciation through the use of descriptive adjectives. The second activity was initiated to develop and test the concept of building endurance regarding the general public’s aesthetic appreciation of existing buildings. A methodological framework was developed to facilitate investigation of changes of human aesthetic response related to changes in the built environment. Cross-cultural variables and respondent’s age parameter were found to be influential in conditioning people’s aesthetic responses to photographs of houses and urban streetscapes. Few differences were observed between male and female aesthetic responses both in their descriptions of visual quality and their ideal house profile. A cross-cultural, universal profile of ideal house qualities was obtained by utilizing responses from the cross-language semantic differential scale. However differences in people’s aesthetic preference selections were observed. Additionally, respondents’ preference rankings demonstrated that the general public supports the desire of preserving the existing urban condition. Appropriate refurbishment strategies were suggested to guide decision making when assessing changes to be made to an existing building and its surrounding environment while at the same time maintaining people’s aesthetic appreciation. The research activities presented in this thesis provide a contribution to current knowledge of the general public’s aesthetic appreciation of the existing buildings and built environments which may be used to aid future sustainable development of the built environment.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Relativistic Hartree-Bogoliubov description of ground-state properties of Ni and Sn isotopes
The Relativistic Hartree Bogoliubov (RHB) theory is applied in the
description of ground-state properties of Ni and Sn isotopes. The NL3 parameter
set is used for the effective mean-field Lagrangian, and pairing correlations
are described by the pairing part of the finite range Gogny interaction D1S.
Fully self-consistent RHB solutions are calculated for the Ni () and Sn () isotopes. Binding energies, neutron separation
energies, and proton and neutron radii are compared with experimental
data. The model predicts a reduction of the spin-orbit potential with the
increase of the number of neutrons. The resulting energy splittings between
spin-orbit partners are discussed, as well as pairing properties calculated
with the finite range effective interaction in the channel.Comment: 11 pages, RevTex, 12 p.s figures, submitted to Phys. Rev.
Demand-side management in office buildings in Kuwait through an ice-storage assisted HVAC system with model predictive control
Examining methods for controlling the electricity demand in Kuwait was the main objective and motivation of this researchp roject. The extensiveu se of air-conditioning for indoor cooling in office and large commercial buildings in Kuwait and the Gulf States represents a major part of the power and electricity consumption in such countries. The rising electricity generation cost and growing rates of consumption continuously demand the construction new power plants. Devising and enforcing Demand-SideM anagemen(t DSM) in the form of energye fficient operations trategies was the response of this research project to provide a means to rectify this situation using the demand-side management technique known as demand levelling or load shifting. State of the art demand-sidem anagementte chniquesh ave been examined through the developmenot f a model basedp redictive control optimisations trategyf or an integrateda ndm odulara pproachto the provisiono f ice thermals torage. To evaluate the potential of ice-storage assisted air-conditioning systems in flattening the demand curve at peak times during the summer months in Kuwait, a model of a Heating, Ventilation, and Air-conditioning (HVAC) plant was developed in Matlab. The model engaged the use of model based predictive control (MPQ) as an optimisation tool for the plant as a whole. The model with MPC was developed to chose and decide on which control strategy to operate the integrated ice-storage HVAC plant. The model succeeded in optimising the operation of the plant and introduced encouraging improvement of the performance of the system as a whole. The concept of the modular ice-storage system was introduced through a control zoning strategy based on zonal orientation. It is believed that such strategy could lead to the modularisation of ice-storage systems. Additionally, the model was examined and tested in relation to load flattening and demonstrated promising enhancement in the shape of the load curve and demonstrated flattened demand curves through the employed strategy. When compared with measured data from existing buildings, the model showed potential for the techniques utilised to improve the load factor for office buildings.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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