2,693 research outputs found
Simulation of an 1857-like Mw 7.9 San Andreas Fault Earthquake and the Response of Tall Steel Moment Frame Buildings in Southern California – A Prototype Study
In 1857, an earthquake of magnitude 7.9 occurred on the San Andreas fault, starting at Parkfield and rupturing
in a southeasterly direction for more than 360 km. Such a unilateral rupture produces significant directivity
toward the San Fernando and Los Angeles basins. The strong shaking in the basins due to this earthquake
would have had significant long-period content (2-8 s), and the objective of this study is to quantify the impact
of such an earthquake on two 18-story steel moment frame building models, hypothetically located at 636 sites
on a 3.5 km grid in southern California. End-to-end simulations include modeling the source and rupture of a
fault at one end, numerically propagating the seismic waves through the earth structure, simulating the damage
to engineered structures and estimating the economic impact at the other end using high-performance computing.
In this prototype study, we use an inferred finite source model of the magnitude 7.9, 2002 Denali fault
earthquake in Alaska, and map it onto the San Andreas fault with the rupture originating at Parkfield and
propagating southward over a distance of 290 km. Using the spectral element seismic wave propagation code,
SPECFEM3D, we simulate an 1857-like earthquake on the San Andreas fault and compute ground motions at
the 636 analysis sites. Using the nonlinear structural analysis program, FRAME3D, we subsequently analyze
3-D structural models of an existing tall steel building designed using the 1982 Uniform Building Code (UBC),
as well as one designed according to the 1997 UBC, subjected to the computed ground motion at each of these
sites. We summarize the performance of these structural models on contour maps of peak interstory drift.
We then perform an economic loss analysis for the two buildings at each site, using the Matlab Damage and
Loss Analysis (MDLA) toolbox developed to implement the PEER loss-estimation methodology. The toolbox
includes damage prediction and repair cost estimation for structural and non-structural components and allows
for the computation of the mean and variance of building repair costs conditional on engineering demand
parameters (i.e. inter-story drift ratios and peak floor accelerations). Here, we modify it to treat steel-frame
high-rises, including aspects such as mechanical, electrical and plumbing systems, traction elevators, and the
possibility of irreparable structural damage. We then generate contour plots of conditional mean losses for the
San Fernando and the Los Angeles basins for the pre-Northridge and modern code-designed buildings, allowing
for comparison of the economic effects of the updated code for the scenario event. In principle, by simulating
multiple seismic events, consistent with the probabilistic seismic hazard for a building site, the same basic
approach could be used to quantify the uncertain losses from future earthquakes
Monitoring and Optimization of Building Operations of a Low-Energy School Building
The ambitious design and energy concept of the new Gebhard-Müller-Schule (GMS) school building in Biberach/Riss, Germany proved itself during the first three school years of operation. The intended target value of 30 kWh/(m2a) overall heating energy consumption was almost met during the second year of operation in 2006 and finally achieved in 2007, due to well-working optimization measures, which were identified through monitoring of the building operation. Heating and cooling energy is mainly provided by a groundwater well plant, which serves as a heat source for two heat pumps as well as a direct cooling source for supplying the radiant heating and cooling system that is integrated in the concrete floor and ceiling slabs (thermally activated building component systems – TABS). Indoor air conditioning and server room cooling are also connected to the groundwater cooling system. The main component of the groundwater well plant is a submersible pump on the bottom of the well which is located underneath the building. The pump supplies the building reliably with geothermal energy, but also consumes a significant amount of electricity. Monitoring and optimization of the building’s operation, funded by the Federal Ministry of Economics and Technology in Germany, revealed fundamental findings about the operation of the system and the possibilities to improve the building’s performance. Since 2005, the measurements show a continuous increase in efficiency, particularly in the field of auxiliary energies. This significantly increased performance clearly shows the potential of the use of groundwater for heating and cooling purposes and of thermally activated building component systems. In addition the measurements reveal the sensitivity of the system efficiency in terms of operating parameters
Chaotic Orbits in Thermal-Equilibrium Beams: Existence and Dynamical Implications
Phase mixing of chaotic orbits exponentially distributes these orbits through
their accessible phase space. This phenomenon, commonly called ``chaotic
mixing'', stands in marked contrast to phase mixing of regular orbits which
proceeds as a power law in time. It is operationally irreversible; hence, its
associated e-folding time scale sets a condition on any process envisioned for
emittance compensation. A key question is whether beams can support chaotic
orbits, and if so, under what conditions? We numerically investigate the
parameter space of three-dimensional thermal-equilibrium beams with space
charge, confined by linear external focusing forces, to determine whether the
associated potentials support chaotic orbits. We find that a large subset of
the parameter space does support chaos and, in turn, chaotic mixing. Details
and implications are enumerated.Comment: 39 pages, including 14 figure
Age-dependent differences in human brain activity using a face- and location-matching task: An fMRI study
Purpose: To evaluate the differences of cortical activation patterns in young and elderly healthy subjects for object and spatial visual processing using a face- and location-matching task. Materials and Methods: We performed a face- and a location-matching task in 15 young (mean age: 28 +/- 9 years) and 19 elderly (mean age: 71 +/- 6 years) subjects. Each experiment consisted of 7 blocks alternating between activation and control condition. For face matching, the subjects had to indicate whether two displayed faces were identical or different. For location matching, the subjects had to press a button whenever two objects had an identical position. For control condition, we used a perception task with abstract images. Functional imaging was performed on a 1.5-tesla scanner using an EPI sequence. Results: In the face-matching task, the young subjects showed bilateral (right 1 left) activation in the occipito-temporal pathway (occipital gyrus, inferior and middle temporal gyrus). Predominantly right hemispheric activations were found in the fusiform gyrus, the right dorsolateral prefrontal cortex (inferior and middle frontal gyrus) and the superior parietal gyrus. In the elderly subjects, the activated areas in the right fronto-lateral cortex increased. An additional activated area could be found in the medial frontal gyrus (right > left). In the location-matching task, young subjects presented increased bilateral (right > left) activation in the superior parietal lobe and precuneus compared with face matching. The activations in the occipito-temporal pathway, in the right fronto-lateral cortex and the fusiform gyrus were similar to the activations found in the face-matching task. In the elderly subjects, we detected similar activation patterns compared to the young subjects with additional activations in the medial frontal gyrus. Conclusion: Activation patterns for object-based and spatial visual processing were established in the young and elderly healthy subjects. Differences between the elderly and young subjects could be evaluated, especially by using a face-matching task. Copyright (c) 2007 S. Karger AG, Basel
Detection of blood aspiration in deadly head gunshots comparing postmortem computed tomography (PMCT) and autopsy
BACKGROUND: The aim of our study was to analyze the reliability of postmortem computed tomography (PMCT) versus autopsy in detecting signs of blood aspiration in a distinct group of patients following deadly head, mouth or floor of mouth gunshot injuries. METHODS: In this study, in 41 cases PMCT was compared to autopsy reports, the gold standard of postmortem exams, regarding detection of blood aspiration. PMCT was evaluated for the presence and level of typical signs of blood aspiration in the major airways and lung using a semi-quantitative scale ranging from level 0 (no aspiration) to 3 (significant aspiration) also taking density values of the described potential aspiratory changes into account. RESULTS: Overall, in 29 (70.7%) of 41 enrolled cases PMCT and autopsy revealed the same level of aspiration. A difference of one level between PMCT and autopsy resulted for 5 (12.2%) of the remaining 12 cases. More than one level difference between both methods resulted for 7 cases (17.2%). Autopsy described no signs of aspiration in 10 cases, compared to 31 cases with reported blood aspiration. In contrast, PMCT revealed no signs of blood aspiration in 15 cases whereas 26 cases were rated as positive for signs of aspiration in the major airways. In 18 of these 26 cases considered positive for blood aspiration by autopsy and PMCT, clear signs of aspiration signs were also described bilaterally by both methods. CONCLUSIONS: The presented study provides evidence for the assumption that PMCT seems to be helpful in the detection of blood aspiration in cases of deadly head gunshots. In conclusion, it seems reasonable to suggest performing PMCT additionally to traditional postmortem exams in cases of suspected aspiration to rule out false-negative cases and to possibly allow for a more detailed and rather evidence based examination reconnoitering the cause of death. However, the adequate use of PMCT in this context needs further evaluation and the definition of an objective scale for aspiration detection on PMCT needs to be established in future studies
Transverse effects in multifrequency Raman generation
The theory of ultrabroadband multifrequency Raman generation is extended, for the first time, to allow for beam-propagation effects in one and two transverse dimensions. We show that a complex transverse structure develops even when diffraction is neglected. In the general case, we examine how the ultrabroadband multifrequency Raman generation process is affected by the intensity, phase quality, and width of the input beams, and by the length of the Raman medium. The evolution of power spectra, intensity profiles, and global characteristics of the multifrequency beams are investigated and explained. In the two-dimensional transverse case, bandwidths comparable to the optical carrier frequency, spanning the whole visible spectrum and beyond, are still achievable
Ultrabroad-bandwidth multifrequency Raman generation
We report on the modeling of transient stimulated rotational Raman scattering in H2 gas. We predict a multifrequency output, spanning a bandwidth greater than the pump frequency, that may be generated without any significant delay with respect to the pump pulses. The roles of dispersion and transiency are quantified
Efficient computation of matched solutions of the Kapchinskij-Vladimirskij envelope equations for periodic focusing lattices
A new iterative method is developed to numerically calculate the periodic,
matched beam envelope solution of the coupled Kapchinskij-Vladimirskij (KV)
equations describing the transverse evolution of a beam in a periodic, linear
focusing lattice of arbitrary complexity. Implementation of the method is
straightforward. It is highly convergent and can be applied to all usual
parameterizations of the matched envelope solutions. The method is applicable
to all classes of linear focusing lattices without skew couplings, and also
applies to all physically achievable system parameters -- including where the
matched beam envelope is strongly unstable. Example applications are presented
for periodic solenoidal and quadrupole focusing lattices. Convergence
properties are summarized over a wide range of system parameters.Comment: 20 pages, 5 figures, Mathematica source code provide
Generation of angular-momentum-dominated electron beams from a photoinjector
Various projects under study require an angular-momentum-dominated electron
beam generated by a photoinjector. Some of the proposals directly use the
angular-momentum-dominated beams (e.g. electron cooling of heavy ions), while
others require the beam to be transformed into a flat beam (e.g. possible
electron injectors for light sources and linear colliders). In this paper, we
report our experimental study of an angular-momentum-dominated beam produced in
a photoinjector, addressing the dependencies of angular momentum on initial
conditions. We also briefly discuss the removal of angular momentum. The
results of the experiment, carried out at the Fermilab/NICADD Photoinjector
Laboratory, are found to be in good agreement with theoretical and numerical
models.Comment: 8 pages, 7 figures, submitted to Phys. Rev. ST Accel. Beam
Comparison of CT colonography, colonoscopy, sigmoidoscopy and faecal occult blood tests for the detection of advanced adenoma in an average risk population.
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