1,506 research outputs found
Development of driving simulator for the experiment of tsunami evacuation using automobile
The 2011 off the Pacific coast of Tohoku Earthquake, which occurred on March 11, 2011, triggered an extremely large tsunami. More than 15,000 deaths and 3,400 people missing were confirmed and 92.4% of the fatalities in Iwate, Miyagi, and Fukushima prefectures resulted from drowning. In Japan, it is basically prohibited to evacuate by automobile in case of tsunami because there may occur traffic congestions and accidents. However, Central Disaster Management Council of Japan reported that about 57% of evacuees used their automobiles to reach the upland refuges. This resulted from the social situations in the coastal residential areas in Japan. Aging of population is rather fast especially in the affected areas by the 2011 Tohoku earthquake, and the number of people in need of nursing care is increasing. Based on these circumstances, many people drove to the elevated areas after the 2011 Tohoku earthquake although the use of automobile was prohibited. This study aims to reveal the permissible limits of tsunami evacuation using automobile based on a series of driving simulator experiments. The authors perform numerical simulation of tsunami propagation, and the results are visualized from driver???s point of view using 3D computer graphics (CG). The CG is installed to a driving simulator, which consists of three LCDs, steering wheel, and brake and accelerator pedals. Several tsunami scenarios are employed in the driving simulator experiments to reveal the effectiveness of evacuation using automobile quantitatively
Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities
We calculate the intersubband absorption linewidth in quantum wells (QWs) due
to scattering by interface roughness, LO phonons, LA phonons, alloy disorder,
and ionized impurities, and compare it with the transport energy broadening
that corresponds to the transport relaxation time related to electron mobility.
Numerical calculations for GaAs QWs clarify the different contributions of each
individual scattering mechanism to absorption linewidth and transport
broadening. Interface roughness scattering contributes about an order of
magnitude more to linewidth than to transport broadening, because the
contribution from the intrasubband scattering in the first excited subband is
much larger than that in the ground subband. On the other hand, LO phonon
scattering (at room temperature) and ionized impurity scattering contribute
much less to linewidth than to transport broadening. LA phonon scattering makes
comparable contributions to linewidth and transport broadening, and so does
alloy disorder scattering. The combination of these contributions with
significantly different characteristics makes the absolute values of linewidth
and transport broadening very different, and leads to the apparent lack of
correlation between them when a parameter, such as temperature or alloy
composition, is changed. Our numerical calculations can quantitatively explain
the previously reported experimental results.Comment: 17 pages, including 15 figure
Cooling of radiative quantum-dot excitons by terahertz radiation: A spin-resolved Monte Carlo carrier dynamics model
We have developed a theoretical model to analyze the anomalous cooling of
radiative quantum dot (QD) excitons by THz radiation reported by Yusa et al
[Proc. 24th ICPS, 1083 (1998)]. We have made three-dimensional (3D) modeling of
the strain and the piezoelectric field and calculated the 3D density of states
of strain induced quantum dots. On the basis of this analysis we have developed
a spin dependent Monte Carlo model, which describes the carrier dynamics in
QD's when the intraband relaxation is modulated by THz radiation. We show that
THz radiation causes resonance transfer of holes from dark to radiative states
in strain-induced QD's. The transition includes a spatial transfer of holes
from the piezoelectric potential mimima to the deformation potential minimum.
This phenomenon strongly enhances the QD ground state luminescence at the
expense of the luminescence from higher states. Our model also reproduces the
delayed flash of QD ground state luminescence, activated by THz radiation even
s after the carrier generation. Our simulations suggest a more general
possibility to cool the radiative exciton subsystem in optoelectronic devices.Comment: 18 pages, 1 table, 8 figures, submitted to Physical Review B v2:
major conceptual changes. The article was extended considerably to suit
Physical Review B (instead of Physical Review Letters
Green's function approach to transport through a gate-all-around Si nanowire under impurity scattering
We investigate transport properties of gate-all-around Si nanowires using
non-equilibrium Green's function technique. By taking into account of the
ionized impurity scattering we calculate Green's functions self-consistently
and examine the effects of ionized impurity scattering on electron densities
and currents. For nano-scale Si wires, it is found that, due to the impurity
scattering, the local density of state profiles loose it's interference
oscillations as well as is broaden and shifted. In addition, the impurity
scattering gives rise to a different transconductance as functions of
temperature and impurity scattering strength when compared with the
transconductance without impurity scattering.Comment: 8 pages, 4 figure
Sensitivity of cosmic-ray experiments to ultra-high-energy photons: reconstruction of the spectrum and limits on the superheavy dark matter
We estimate the sensitivity of various experiments detecting
ultra-high-energy cosmic rays to primary photons with energies above 10^19 eV.
We demonstrate that the energy of a primary photon may be significantly (up to
a factor of ~ 10) under- or overestimated for particular primary energies and
arrival directions. We consider distortion of the reconstructed cosmic-ray
spectrum for the photonic component. As an example, we use these results to
constrain the parameter space of models of superheavy dark matter by means of
both the observed spectra and available limits on the photon content. We find
that a significant contribution of ultra-high-energy particles (photons and
protons) from decays of superheavy dark matter is allowed by all these
constraints.Comment: 18 pages, 7 figure
Quantum wires from coupled InAs/GaAs strained quantum dots
The electronic structure of an infinite 1D array of vertically coupled
InAs/GaAs strained quantum dots is calculated using an eight-band
strain-dependent k-dot-p Hamiltonian. The coupled dots form a unique quantum
wire structure in which the miniband widths and effective masses are controlled
by the distance between the islands, d. The miniband structure is calculated as
a function of d, and it is shown that for d>4 nm the miniband is narrower than
the optical phonon energy, while the gap between the first and second minibands
is greater than the optical phonon energy. This leads to decreased optical
phonon scattering, providing improved quantum wire behavior at high
temperatures. These miniband properties are also ideal for Bloch oscillation.Comment: 5 pages revtex, epsf, 8 postscript figure
Energy partitioning on intermolecular interactions: ab initio Monte Carlo study of water dimer
Ab initio Monte Carlo computations were carried out on H₂O dimer system. By introducing the energy partitioning
scheme that we have developed recently, ab initio calculated H₂O–H₂O interaction can be analyzed
from the viewpoint of atom-atom interaction. The electronic polarization caused by the interaction and its
temperature dependence are also discussed. To our best knowledge, this is the first report on the thermal
distribution of electronic distortion energy assigned to a molecule.Виконанi ab initio Монте Карло розрахунки для H2O димерної системи. Вводячи розроблену ранiше схему роздiлення енергiї, ab initio розрахована взаємодiя H2O–H2O може бути проаналiзована з точки зору атом-атомної взаємодiї. Обговорюється електронна поляризацiя, обумовлена взаємодiєю, та її температурна залежнiсть. З точки зору наших вiдомостей, це є перше повiдомлення про термiчний розподiл електронної змiни енергiї, переданої молекулi
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