1,609 research outputs found
Seismic PBD of Piles from Monte-Carlo Simulation Using EQWEAP Analysis with Weighted Intensities
[[abstract]]This paper discusses the seismic performance based design (PBD) analysis on piles using one-dimensional stress wave equation and Monte Carlo Simulation. Seismic responses of the piles were monitored at a wider spectrum of earthquake intensities rather than the target ones. To obtain appropriate estimations, weights of the intensities were calculated from the probability density function solvable from the seismic hazard curve. Probabilities of failure of the piles were evaluated for uncertainties of soil parameters and seismic records, and then calibrated with the weights. The result of the numerical study indicates that the seismic force is the most dominant factor. Large diameter pile will exert cracks around pile head under moderate earthquakes. Therefore assessment based on only the pile head would become very critical. For design and maximum consideration (MCE) earthquakes, the piles were found satisfied because of performance required on ductility resistance and ultimate moment capacity. Probabilities of failure of the piles were also found sensitive to horizontal load from the superstructure. Comparing the correspondent reliability indexes with those required for acceptable foundations, the seismic performance of the piles can be assessed. With the suggested factor of safety, the seismic performance of the piles was found to be 1.1~2.2 for design and MCE quakes in this study.[[notice]]補正完畢[[incitationindex]]EI[[booktype]]紙
Fine structure of excitons in CuO
Three experimental observations on 1s-excitons in CuO are not consistent
with the picture of the exciton as a simple hydrogenic bound state: the
energies of the 1s-excitons deviate from the Rydberg formula, the total exciton
mass exceeds the sum of the electron and hole effective masses, and the
triplet-state excitons lie above the singlet. Incorporating the band structure
of the material, we calculate the corrections to this simple picture arising
from the fact that the exciton Bohr radius is comparable to the lattice
constant. By means of a self-consistent variational calculation of the total
exciton mass as well as the ground-state energy of the singlet and the
triplet-state excitons, we find excellent agreement with experiment.Comment: Revised abstract; 10 pages, revtex, 3 figures available from G.
Kavoulakis, Physics Department, University of Illinois, Urban
Update of High Resolution (e,e'K^+) Hypernuclear Spectroscopy at Jefferson Lab's Hall A
Updated results of the experiment E94-107 hypernuclear spectroscopy in Hall A
of the Thomas Jefferson National Accelerator Facility (Jefferson Lab), are
presented. The experiment provides high resolution spectra of excitation energy
for 12B_\Lambda, 16N_\Lambda, and 9Li_\Lambda hypernuclei obtained by
electroproduction of strangeness. A new theoretical calculation for
12B_\Lambda, final results for 16N_\Lambda, and discussion of the preliminary
results of 9Li_\Lambda are reported.Comment: 8 pages, 5 figures, submitted to the proceedings of Hyp-X Conferenc
New Polynomial Cases of the Weighted Efficient Domination Problem
Let G be a finite undirected graph. A vertex dominates itself and all its
neighbors in G. A vertex set D is an efficient dominating set (e.d. for short)
of G if every vertex of G is dominated by exactly one vertex of D. The
Efficient Domination (ED) problem, which asks for the existence of an e.d. in
G, is known to be NP-complete even for very restricted graph classes.
In particular, the ED problem remains NP-complete for 2P3-free graphs and
thus for P7-free graphs. We show that the weighted version of the problem
(abbreviated WED) is solvable in polynomial time on various subclasses of
2P3-free and P7-free graphs, including (P2+P4)-free graphs, P5-free graphs and
other classes.
Furthermore, we show that a minimum weight e.d. consisting only of vertices
of degree at most 2 (if one exists) can be found in polynomial time. This
contrasts with our NP-completeness result for the ED problem on planar
bipartite graphs with maximum degree 3
The Role of Nonequilibrium Dynamical Screening in Carrier Thermalization
We investigate the role played by nonequilibrium dynamical screening in the
thermalization of carriers in a simplified two-component two-band model of a
semiconductor. The main feature of our approach is the theoretically sound
treatment of collisions. We abandon Fermi's Golden rule in favor of a
nonequilibrium field theoretic formalism as the former is applicable only in
the long-time regime. We also introduce the concept of nonequilibrium dynamical
screening. The dephasing of excitonic quantum beats as a result of
carrier-carrier scattering is brought out. At low densities it is found that
the dephasing times due to carrier-carrier scattering is in picoseconds and not
femtoseconds, in agreement with experiments. The polarization dephasing rates
are computed as a function of the excited carrier density and it is found that
the dephasing rate for carrier-carrier scattering is proportional to the
carrier density at ultralow densities. The scaling relation is sublinear at
higher densities, which enables a comparison with experiment.Comment: Revised version with additional refs. 12 pages, figs. available upon
request; Submitted to Phys. Rev.
Rising drug allergy alert overrides in electronic health records: an observational retrospective study of a decade of experience
Objective There have been growing concerns about the impact of drug allergy alerts on patient safety and provider alert fatigue. The authors aimed to explore the common drug allergy alerts over the last 10 years and the reasons why providers tend to override these alerts. Design: Retrospective observational cross-sectional study (2004–2013). Materials and Methods Drug allergy alert data (n = 611,192) were collected from two large academic hospitals in Boston, MA (USA). Results Overall, the authors found an increase in the rate of drug allergy alert overrides, from 83.3% in 2004 to 87.6% in 2013 (P < .001). Alarmingly, alerts for immune mediated and life threatening reactions with definite allergen and prescribed medication matches were overridden 72.8% and 74.1% of the time, respectively. However, providers were less likely to override these alerts compared to possible (cross-sensitivity) or probable (allergen group) matches (P < .001). The most common drug allergy alerts were triggered by allergies to narcotics (48%) and other analgesics (6%), antibiotics (10%), and statins (2%). Only slightly more than one-third of the reactions (34.2%) were potentially immune mediated. Finally, more than half of the overrides reasons pointed to irrelevant alerts (i.e., patient has tolerated the medication before, 50.9%) and providers were significantly more likely to override repeated alerts (89.7%) rather than first time alerts (77.4%, P < .001). Discussion and Conclusions These findings underline the urgent need for more efforts to provide more accurate and relevant drug allergy alerts to help reduce alert override rates and improve alert fatigue
Fluorescent carbon dioxide indicators
Over the last decade, fluorescence has become the dominant tool in biotechnology and medical imaging. These exciting advances have been underpinned by the advances in time-resolved techniques and instrumentation, probe design, chemical / biochemical sensing, coupled with our furthered knowledge in biology. Complementary volumes 9 and 10, Advanced Concepts of Fluorescence Sensing: Small Molecule Sensing and Advanced Concepts of Fluorescence Sensing: Macromolecular Sensing, aim to summarize the current state of the art in fluorescent sensing. For this reason, Drs. Geddes and Lakowicz have invited chapters, encompassing a broad range of fluorescence sensing techniques. Some chapters deal with small molecule sensors, such as for anions, cations, and CO2, while others summarize recent advances in protein-based and macromolecular sensors. The Editors have, however, not included DNA or RNA based sensing in this volume, as this were reviewed in Volume 7 and is to be the subject of a more detailed volume in the near future
Search for Small Trans-Neptunian Objects by the TAOS Project
The Taiwan-America Occultation Survey (TAOS) aims to determine the number of
small icy bodies in the outer reach of the Solar System by means of stellar
occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9)
telescopes have been installed at Lulin Observatory in Taiwan to simultaneously
monitor some thousand of stars for such rare occultation events. Because a
typical occultation event by a TNO a few km across will last for only a
fraction of a second, fast photometry is necessary. A special CCD readout
scheme has been devised to allow for stellar photometry taken a few times per
second. Effective analysis pipelines have been developed to process stellar
light curves and to correlate any possible flux changes among all telescopes. A
few billion photometric measurements have been collected since the routine
survey began in early 2005. Our preliminary result of a very low detection rate
suggests a deficit of small TNOs down to a few km size, consistent with the
extrapolation of some recent studies of larger (30--100 km) TNOs.Comment: 4 pages, 3 figures, IAU Symposium 23
Electronic structure, charge transfer, and intrinsic luminescence of gadolinium oxide nanoparticles: Experiment and theory
The cubic (c) and monoclinic (m) polymorphs of Gd2O3 were studied using the
combined analysis of several materials science techniques - X-ray diffraction
(XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy
(XPS), and photoluminescence (PL) spectroscopy. Density functional theory (DFT)
based calculations for the samples under study were performed as well. The
cubic phase of gadolinium oxide (c-Gd2O3) synthesized using a precipitation
method exhibits spheroidal-like nanoclusters with well-defined edges assembled
from primary nanoparticles with an average size of 50 nm, whereas the
monoclinic phase of gadolinium oxide (m-Gd2O3) deposited using explosive
pyrolysis has a denser structure compared with natural gadolinia. This phase
also has a structure composed of three-dimensional complex agglomerates without
clear-edged boundaries that are ~21 nm in size plus a cubic phase admixture of
only 2 at. % composed of primary edge-boundary nanoparticles ~15 nm in size.
These atomic features appear in the electronic structure as different defects
([Gd...O-OH] and [Gd...O-O]) and have dissimilar contributions to the
charge-transfer processes among the appropriate electronic states with
ambiguous contributions in the Gd 5p - O 2s core-like levels in the valence
band structures. The origin of [Gd...O-OH] defects found by XPS was
well-supported by PL analysis. The electronic and atomic structures of the
synthesized gadolinias calculated using DFT were compared and discussed on the
basis of the well-known joint OKT-van der Laan model, and good agreement was
established.Comment: 27 pages, 10 figures, accepted in Appl. Surf. Sc
A Nanofiber-Based Optical Conveyor Belt for Cold Atoms
We demonstrate optical transport of cold cesium atoms over millimeter-scale
distances along an optical nanofiber. The atoms are trapped in a
one-dimensional optical lattice formed by a two-color evanescent field
surrounding the nanofiber, far red- and blue-detuned with respect to the atomic
transition. The blue-detuned field is a propagating nanofiber-guided mode while
the red-detuned field is a standing-wave mode which leads to the periodic axial
confinement of the atoms. Here, this standing wave is used for transporting the
atoms along the nanofiber by mutually detuning the two counter-propagating
fields which form the standing wave. The performance and limitations of the
nanofiber-based transport are evaluated and possible applications are
discussed
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