4,496 research outputs found
Hope for the Best, Prepare for the Worst: Response of Tall Steel Buildings to the ShakeOut Scenario Earthquake
This work represents an effort to develop one plausible realization of the effects of the scenario event on tall steel moment-frame buildings. We have used the simulated ground motions with three-dimensional nonlinear finite element models of three buildings in the 20-story class to simulate structural responses at 784 analysis sites spaced at approximately 4 km throughout the San Fernando Valley, the San Gabriel Valley, and the Los Angeles Basin. Based on the simulation results and available information on the number and distribution of steel buildings, the recommended damage scenario for the ShakeOut drill was 5% of the estimated 150 steel moment-frame structures in the 10ā30 story range collapsing, 10% red-tagged, 15% with damage serious enough to cause loss of life, and 20% with visible damage requiring building closure
A relation between moduli space of D-branes on orbifolds and Ising model
We study D-branes transverse to an abelian orbifold C^3/Z_n Z_n. The moduli
space of the gauge theory on the D-branes is analyzed by combinatorial
calculation based on toric geometry. It is shown that the calculation is
related to a problemto count the number of ground states of an
antiferromagnetic Ising model. The lattice on which the Ising model is defined
is a triangular one defined on the McKay quiver of the orbifold.Comment: 20 pages, 13 figure
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Microfluidic droplet control by photothermal interfacial flow
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Droplet-based microfluidics is an emerging field that can perform a variety of discrete operation of
tiny amount of reagent or individual cell. Noncontact manipulation of droplets in a microfluidic platform can
be achieved by using the Marangoni convection due to a local temperature gradient given by the irradiation
of heating light. This method provides noncontact, selective and flexible manipulation for droplets flowing in
microfluidic network. Although the potential of this selective operation method of droplets was confirmed,
the driving force exerted on droplets has not been quantitatively obtained. In this study, we have developed a
measurement system of the temperature field around droplets during the manipulation by light irradiation
and evaluated the manipulation force. In O/W emulsion system with oleic acid and buffer solution, oleic acid
for droplet and buffer solution for continuous phase, the temperature distribution around the droplets was
measured by laser-induced fluorescence. From the balance of drag force and photo-induced Marangoni force,
the driving force was determined. From the results, we confirmed the applicability of the noncontact droplet
manipulation using the photothermal Marangoni effect
Role of three-body interactions in formation of bulk viscosity in liquid argon
With the aim of locating the origin of discrepancy between experimental and
computer simulation results on bulk viscosity of liquid argon, a molecular
dynamic simulation of argon interacting via ab initio pair potential and
triple-dipole three-body potential has been undertaken. Bulk viscosity,
obtained using Green-Kubo formula, is different from the values obtained from
modeling argon using Lennard-Jones potential, the former being closer to the
experimental data. The conclusion is made that many-body inter-atomic
interaction plays a significant role in formation of bulk viscosity.Comment: 4 pages, 3 figure
Application of Stochastic Simulation Methods to System Identification
Reliable predictive models for the response of structures are a necessity for many
branches of earthquake engineering, such as design, structural control, and structural
health monitoring. However, the process of choosing an appropriate class of models
to describe a system, known as model-class selection, and identifying the specific
predictive model based on available data, known as system identification, is difficult.
Variability in material properties, complex constitutive behavior, uncertainty in the
excitations caused by earthquakes, and limited constraining information (relatively
few channels of data, compared to the number of parameters needed for a useful
predictive model) make system identification an ill-conditioned problem. In addition,
model-class selection is not trivial, as it involves balancing predictive power with
simplicity.
These problems of system identification and model-class selection may be addressed
using a Bayesian probabilistic framework that provides a rational, transparent
method for combining prior knowledge of a system with measured data and for
choosing between competing model classes. The probabilistic framework also allows
for explicit quantification of the uncertainties associated with modeling a system.
The essential idea is to use probability logic and Bayes' Theorem to give a measure
of plausibility for a model or class of models that is updated with available data.
Similar approaches have been used in the field of system identification, but many
currently used methods for Bayesian updating focus on the model defined by the set
of most plausible parameter values. The challenge for these approaches (referred to as
asymptotic-approximation-based methods) is when one must deal with ill-conditioned
problems, where there may be many models with high plausibility, rather than a single
v
dominant model. It is demonstrated here that ill-conditioned problems in system
identification and model-class selection can be effectively addressed using stochastic
simulation methods.
This work focuses on the application of stochastic simulation to updating and
comparing model classes in problems of: (1) development of empirical ground motion
attenuation relations, (2) structural model updating using incomplete modal data
for the purposes of structural health monitoring, and (3) identification of hysteretic
structural models, including degrading models, from seismic structural response.
The results for system identification and model-class selection in this work fall into
three categories. First, in cases where the existing asymptotic approximation-based
methods are appropriate (i.e., well-conditioned problems with one highest-plausibility
model), the results obtained using stochastic simulation show good agreement with
results from asymptotic-approximation-based methods. Second, for cases involving
ill-conditioned problems based on simulated data, stochastic simulation methods are
successfully applied to obtain results in a situation where the use of asymptotics is
not feasible (specfically, the identification of hysteretic models). Third, preliminary
studies using stochastic simulation to identify a deteriorating hysteretic model with
relatively sparse real data from a structure damaged in the 1994 Northridge earthquake
show that the high-plausibility models demonstrate behavior consistent with
the observed damage, indicating that there is promise in applying these methods to
ill-conditioned problems in the real world
Body Parts and Their Epic Struggle in Ovidās Amores
This thesis examines how body parts in Ovidās Amores provide the location for an epic battle between the conflicting genres of Tragedy and Elegy. The first chapter summarizes past Ovidian scholarship. The second chapter examines how Ovid separates body parts of the amator and the puella in Amores 1.4 and 1.5 in order to deny the lovers complete unification. The third chapter expands the conclusion of the second by analyzing poems in Books 2 and 3, which contain a significant number of body parts, to determine how the amatorās interaction with the puellaās body parts reflects his lack of union with her in public and private spheres. The fourth chapter rereads the puellaās body parts, and the amatorās relationship with them, with a view to establish the puella as either Tragedy or Elegy and to theorize how the amatorās relationship with the puella symbolizes the poetaās relationship with his poetry
Response of tall steel buildings in southern California to the magnitude 7.8 shakeout scenario earthquake
Currently, there is a significant campaign being undertaken in southern California to increase public awareness
and readiness for the next large earthquake along the San Andreas Fault, culminating in a large-scale
earthquake response exercise. The USGS ShakeOut scenario is a key element to understanding the likely
effects of such an event. A source model for a M7.8 scenario earthquake has been created (Hudnet et al.
2007), and used in conjunction with a velocity model for southern California to generate simulated ground
motions for the event throughout the region (Graves et al. 2008). We were charged by the USGS to provide
one plausible realization of the effects of the scenario event on tall steel moment-frame buildings. We have
used the simulated ground motions with three-dimensional non-linear finite element models of three buildings
(in two orthogonal orientations and two different connection fragility conditions, for a total of twelve
cases) in the 20-story class to simulate structural responses at 784 analysis sites spaced at approximately
4 km throughout the San Fernando Valley, the San Gabriel Valley and the Los Angeles Basin. Based on
the simulation results and available information on the number and distribution of steel buildings, we have
recommended that the ShakeOut drill be planned with a damage scenario comprising of 5% of the estimated
150 steel moment frame structures in the 10-30 story range collapsing (8 collapses), 10% of the structures
red-tagged (16 red-tagged buildings), 15% of the structures with damage serious enough to cause loss of life
(24 buildings with fatalities), and 20% of the structures with visible damage requiring building closure (32
buildings with visible damage and possible injuries). This paper details the analytical study underlying these
recommendations
Phase transitions in systems with two species of molecular motors
Systems with two species of active molecular motors moving on (cytoskeletal)
filaments into opposite directions are studied theoretically using driven
lattice gas models. The motors can unbind from and rebind to the filaments. Two
motors are more likely to bind on adjacent filament sites if they belong to the
same species. These systems exhibit (i) Continuous phase transitions towards
states with spontaneously broken symmetry, where one motor species is largely
excluded from the filament, (ii) Hysteresis of the total current upon varying
the relative concentrations of the two motor species, and (iii) Coexistence of
traffic lanes with opposite directionality in multi-filament systems. These
theoretical predictions should be experimentally accessible.Comment: 7 pages, 4 figures, epl style (.cls-file included), to appear in
Europhys. Lett. (http://www.edpsciences.org/epl
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