836 research outputs found
Excitation spectra of a 3He impurity on 4He clusters
The diffusion Monte Carlo technique is used to calculate and analyze the
excitation spectrum of a single 3He atom bound to a cluster with N 4He atoms,
with the aim of establishing the most adequate filling ordering of
single-fermion orbits to the mixed clusters with a large number of 3He atoms.
The resulting ordering looks like the rotational spectrum of a diatomic
molecule, being classified only by the angular momentum of the level, although
vibrational-like excitations appear at higher energies for sufficiently large
N
The spectra of mixed He-He droplets
The diffusion Monte Carlo technique is used to calculate and analyze the
excitation spectrum of He atoms bound to a cluster of He atoms, by
using a previously determined optimum filling of single-fermion orbits with
well defined orbital angular momentum , spin and parity quantum numbers.
The study concentrates on the energies and shapes of the three kinds of states
for which the fermionic part of the wave function is a single Slater
determinant: maximum or maximum states within a given orbit, and fully
polarized clusters. The picture that emerges is that of systems with strong
shell effects whose binding and excitation energies are essentially determined
over configuration at fixed number of particles and spin, i.e., by the monopole
properties of an effective Hamiltonian.Comment: 14 pages, 15 figure
Performance based probabilistic seismic risk assessment for urban heritage. An example in Pla del Remei Area (Valencia)
The assessment of the seismic behaviour of historic residential buildings and the estimation of their possible losses in the event of an earthquake, is a must for defining strategic mitigation plans to prevent irreplaceable heritage losses. In this study an integrated performance based probabilistic risk assessment methodology is developed. An archival study and a field survey allow to identify architectural and construction characteristics of heritage residential buildings in urban areas and determine realistic structural models. These are analysed by using a limit state approach, coded in the FaMIVE method, considering different construction hypotheses, to produce capacity curves which support the identification of a discrete number of typologies representative of the entire building stock in the area. Their fragility functions are then derived using the modified N2 method. Because of the difficulty in quantifying the expected probable losses in purely economic terms, given the heritage value of these assets, losses are computed in terms of damaged floor surface area and mean damage ratio. These have been obtained through the earthquake loss estimation platform SELENA, considering different possible seismic scenarios. The procedure is applied to masonry residential buildings in Pla del Remei area of Valencia, Spain, built between the end of the 19th Century and the end of the Spanish War (1939). This neighbourhood embodies the cultural values, construction techniques and historic legacy of a new and brief era of modernity, inspired by the new urban theories and architectural styles of Eclecticism and Modernism. Despite Valencia being located in an area of low to moderate seismicity, the results show that the maximum percentage of built damaged area ranges from 5.8 to 11.6% for 475 years return period, increasing to 33.59–51.59% for 975 years return period. The high level of resolution of the study allows mapping and identifying the structures at higher risk and is therefore a valuable tool to support sensitive and targeted retrofitting policies
Equation of state of low--density neutron matter and the pairing gap
We report results of the equation of state of neutron matter in the
low--density regime, where the Fermi wave vector ranges from . Neutron matter in this regime is superfluid because of
the strong and attractive interaction in the channel. The properties of
this superfluid matter are calculated starting from a realistic Hamiltonian
that contains modern two-- and three--body interactions. The ground state
energy and the superfluid energy gap are calculated using the Auxiliary
Field Diffusion Monte Carlo method. We study the structure of the ground state
by looking at pair distribution functions as well as the Cooper-pair wave
function used in the calculations.Comment: 12 pages, 7 figure
Silicon-based three-dimensional microstructures for radiation dosimetry in hadrontherapy
In this work, we propose a solid-state-detector for use in radiation microdosimetry. This device improves the performance of existing dosimeters using customized 3D-cylindrical microstructures etched inside silicon. The microdosimeter consists of an array of micro-sensors that have 3D-cylindrical electrodes of 15 μm diameter and a depth of 5 μm within a silicon membrane, resulting in a well-defined micrometric radiation sensitive volume. These microdetectors have been characterized using an 241Am source to assess their performance as radiation detectors in a high-LET environment. This letter demonstrates the capability of this microdetector to be used to measure dose and LET in hadrontherapy centers for treatment plan verification as part of their patient-specific quality control program
Ground state properties of a dilute homogeneous Bose gas of hard disks in two dimensions
The energy and structure of a dilute hard-disks Bose gas are studied in the
framework of a variational many-body approach based on a Jastrow correlated
ground state wave function. The asymptotic behaviors of the radial distribution
function and the one-body density matrix are analyzed after solving the Euler
equation obtained by a free minimization of the hypernetted chain energy
functional. Our results show important deviations from those of the available
low density expansions, already at gas parameter values . The
condensate fraction in 2D is also computed and found generally lower than the
3D one at the same .Comment: Submitted to PRA. 7 pages and 8 figure
Solidification of small para-H2 clusters at zero temperature
We have determined the ground-state energies of para-H clusters at zero
temperature using the diffusion Monte Carlo method. The liquid or solid
character of each cluster is investigated by restricting the phase through the
use of proper importance sampling. Our results show inhomogeneous
crystallization of clusters, with alternating behavior between liquid and solid
phases up to N=55. From there on, all clusters are solid. The ground-state
energies in the range N=13--75 are established and the stable phase of each
cluster is determined. In spite of the small differences observed between the
energy of liquid and solid clusters, the corresponding density profiles are
significantly different, feature that can help to solve ambiguities in the
determination of the specific phase of H clusters.Comment: 17 pages, accepted for publication in J. Phys. Chem.
State-dependent Jastrow correlation functions for 4He nuclei
We calculate the ground-state energy for the nucleus 4He with V4 nucleon
interactions, making use of a Jastrow description of the corresponding
wavefunction with state-dependent correlation factors. The effect related to
the state dependence of the correlation is quite important, lowering the upper
bound for the ground-state energy by some 2 MeV.Comment: 10 pages, REVTeX, to be published in J. Phys. G: Nucl. Part. Phy
Modelling diffusion of innovations in a social network
A new simple model of diffusion of innovations in a social network with
upgrading costs is introduced. Agents are characterized by a single real
variable, their technological level. According to local information agents
decide whether to upgrade their level or not balancing their possible benefit
with the upgrading cost. A critical point where technological avalanches
display a power-law behavior is also found. This critical point is
characterized by a macroscopic observable that turns out to optimize
technological growth in the stationary state. Analytical results supporting our
findings are found for the globally coupled case.Comment: 4 pages, 5 figures. Final version accepted in PR
Insight into the HEV/PHEV optimal control solution based on a new tuning method
The paper presents a formulation of the energy management problem for Hybrid Electrical Vehicles and Plug-in Hybrid Electrical Vehicles alike, which permits to consider different cost indexes like fuel consumption, total and primary energy consumption, economic cost or CO2 footprint. In-depth analysis of the problem optimal solution is done by means of the application of the λ-plot method, which also permits the optimal tuning of other implementable control strategies. Such an approach is used to understand the effect of the selected cost index, the regional energetic share, the driving conditions, and for deriving rules for battery sizing.C. Guardiola and B. Pla research has been partially supported by Ministerio de Ciencia e Innovacion through Project TRA2010-16205 uDiesel, and the Universitat Politecnica de Valencia through Grants PAID-00-11 2105 and PAID-00-11 2106.Guardiola García, C.; Plá Moreno, B.; Onori, S.; Rizzoni, G. (2014). Insight into the HEV/PHEV optimal control solution based on a new tuning method. Control Engineering Practice. 29:247-256. https://doi.org/10.1016/j.conengprac.2014.01.022S2472562
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