1,494 research outputs found
Service and price competition when customers are naive
We consider a system of two service providers each with a separate queue. Customers choose one queue to join upon arrival and can switch between queues in real time before entering service to maximize their spot utility, which is a function of price and queue length. We characterize the steady-state distribution for queue lengths, and then investigate a two-stage game in which the two service providers first simultaneously select service rates and then simultaneously charge prices. Our results indicate that neither service provider will have both a faster service and a lower price than its competitor. When price plays a less significant role in customers service selection relative to queue length or when the two service providers incur comparable costs for building capacities, they will not engage in price competition. When price plays a significant role and the capacity costs at the service providers sufficiently differ, they will adopt substitutable competition instruments: the lower cost service provider will build a faster service and the higher cost service provider will charge a lower price. Comparing our results to those in the existing literature, we find that the service providers invest in lower service rates, engage in less intense price competition, and earn higher profits, while customers wait in line longer when they are unable to infer service rates and are naive in service selection than when they can infer service rates to make sophisticated choices. The customers jockeying behavior further lowers the service providers capacity investment and lengthens the customers duration of stay
Development of Super-Dwarf Wheat Under Stress Conditions Simulating Those on the Space Station MIR
Super-Dwarf wheat plants were grown in simulation growth chambers under 12 treatments with three photoperiods (18 h, 21 h, 24 h) and four carbon-dioxide levels (360, 1200, 3000, and 7000 11mol/mol). Carbon-dioxide concentrations affected flower initiation rates of Super-Dwarf wheat. The optimum C02level for flower initiation and development was 1200molμ•mol-1. Super-optimum C01 levels delayed flower initiation, but did not decrease final flower bud number per head. Longer photoperiods not only accelerated flower initiation rates, but also decreased deleterious effects of super-optimum C02. Flower bud size and head length at the same developmental stage were larger under longer photoperiods. But final flower bud number was not affected by photoperiod. Stomatal densities on the abaxial surface were more sensitive to the variation of photoperiod and C02 level than those on the adaxial surface for Super-Dwarf wheat. Stomatal density did not significantly change on the adaxial surface, but was significantly decreased on the abaxial surface under longer photoperiods and higher C02 levels at 27 day after planting (DAP). Cell-walls of both stem and leaf tissues did not significantly change with variation of photoperiod and carbon-dioxide levels at either seedling stage or mature stage. McDowell fixative was suitable for long-term storage of plant tissue for use in light microscopy. When stored up to 180 d, there was no significant change in leaf thickness, shape and size of mesophyll cells, and shape of chloroplasts for wheat leaves under the light microscope
Long Fading Mid-Infrared Emission in Transient Coronal Line Emitters: Dust Echo of Tidal Disruption Flare
The sporadic accretion following the tidal disruption of a star by a
super-massive black hole (TDE) leads to a bright UV and soft X-ray flare in the
galactic nucleus. The gas and dust surrounding the black hole responses to such
a flare with an echo in emission lines and infrared emission. In this paper, we
report the detection of long fading mid-IR emission lasting up to 14 years
after the flare in four TDE candidates with transient coronal lines using the
WISE public data release. We estimate that the reprocessed mid-IR luminosities
are in the range between and erg~s
and dust temperature in the range of 570-800K when WISE first detected these
sources three to five years after the flare. Both luminosity and dust
temperature decreases with time. We interpret the mid-IR emission as the
infrared echo of the tidal disruption flare. We estimate the UV luminosity at
the peak flare to be 1 to 30 times erg s and for warm dust
masses to be in the range of 0.05-1.3 Msun within a few parsecs. Our results
suggest that the mid-infrared echo is a general signature of TDE in the
gas-rich environment
Scenimefy: Learning to Craft Anime Scene via Semi-Supervised Image-to-Image Translation
Automatic high-quality rendering of anime scenes from complex real-world
images is of significant practical value. The challenges of this task lie in
the complexity of the scenes, the unique features of anime style, and the lack
of high-quality datasets to bridge the domain gap. Despite promising attempts,
previous efforts are still incompetent in achieving satisfactory results with
consistent semantic preservation, evident stylization, and fine details. In
this study, we propose Scenimefy, a novel semi-supervised image-to-image
translation framework that addresses these challenges. Our approach guides the
learning with structure-consistent pseudo paired data, simplifying the pure
unsupervised setting. The pseudo data are derived uniquely from a
semantic-constrained StyleGAN leveraging rich model priors like CLIP. We
further apply segmentation-guided data selection to obtain high-quality pseudo
supervision. A patch-wise contrastive style loss is introduced to improve
stylization and fine details. Besides, we contribute a high-resolution anime
scene dataset to facilitate future research. Our extensive experiments
demonstrate the superiority of our method over state-of-the-art baselines in
terms of both perceptual quality and quantitative performance.Comment: ICCV 2023. The first two authors contributed equally. Code:
https://github.com/Yuxinn-J/Scenimefy Project page:
https://yuxinn-j.github.io/projects/Scenimefy.htm
Mid-infrared variability of changing-look AGN
It is known that some active galactic nuclei (AGNs) transited from type 1 to
type 2 or vice versa. There are two explanations for the so-called changing
look AGNs: one is the dramatic change of the obscuration along the
line-of-sight, the other is the variation of accretion rate. In this paper, we
report the detection of large amplitude variations in the mid-infrared
luminosity during the transitions in 10 changing look AGNs using WISE and newly
released NEOWISE-R data. The mid-infrared light curves of 10 objects echoes the
variability in the optical band with a time lag expected for dust reprocessing.
The large variability amplitude is inconsistent with the scenario of varying
obscuration, rather supports the scheme of dramatic change in the accretion
rate.Comment: Published by ApjL, 7 pages, 3 figures, 2 table
Development of an integrated computational tool for modelling structural frames in fire considering local effects
In terms of developing knowledge to enable more effective use of performance
based engineering (PBE), one of the key limitations is the lack of an easy to use
integrated computational tool that is also robust and comprehensive enough to
enable automated modelling of more realistic fire scenarios, i.e., the structural
response to localised or travelling fires. The main objective of this thesis is to
establish such an integrated computational tool, which shall be based on the
OpenSees software framework and facilitated by specially developed approaches
to achieve higher efficiency of the integrated analysis. This includes the analysis
of heat transfer from the fire to structural members, as well as the analysis of
structural response to elevated temperatures during the fire.
In this thesis, the research begins with the investigation of the feasibility of
dimensional reduction for heat transfer analyses of structural members subjected
to localised fire action (SFPE and Eurocode 1 fire models), which can be
numerically represented by a linear or exponential correlation between incident
heat flux and radial distance. Accurate estimates of the error induced by
dimensional reduction are presented under strongly varying localised heat fluxes
that represent the most non-uniform fire conditions in a building compartment.
It is shown that beams and slabs can be adequately modelled with a lower
dimensional heat transfer analysis for ordinary building fires. Using this approach,
the complexity of heat transfer modelling and the required computing resource
and user effort can both be significantly reduced, especially in cases where
structural members are subjected to localised fire action.
Thermo-mechanical simulations are presented to address the behaviour of structural
members subjected to localised fire action, for which a ThermalAction-
Wrapper is developed to approximate the temperature distribution from a
mixed-order interpolation between sections (beam) or locations (slab). For concrete
slabs subjected to localised fire, MITC4 based shell elements are used to
account for material and geometric nonlinearities.
An integrated simulation environment is developed, which is designed to be a
computational tool that requires limited input but provides a comprehensive
solution to the problem of simulating large structural frame and sub-frame
response under realistic fire scenarios. A considerable amount of code has been
written to create and operate the building model, and to process the heat fluxes
from the design fires to the structure and the consequential structural response
to the evolution of temperatures within it.
Parametric studies have been performed to investigate the computational performance
of the newly developed elements in modelling beams and slabs subjected to
different cases of localised fire action. The results suggest that 3 to 6 force-based
beam elements can adequately describe the localised response however more elements
are required for quadratic distribution of incident heat flux and higher
temperatures, which is due to the degradation of material strength that governs
the accuracy especially when the members are heavily loaded. For slabs exposed
to localised fires, centre fires are found to produce greater deflections than corner fires, while lateral restraints applied to the slabs may also lead to higher
deflections.
A small-scale three dimensional structural frame is modelled as a demonstration
of the tool, tested against a number of localised fire scenarios. The global
behaviour of the structure with the local effects induced by the fire action and
partially damaged fire protection are investigated. Severe damage can be found
in the members exposed to a single whole compartment fire, in contrast with the
relatively small deflections that are observed when a fully protected column is
engulfed by a localised fire. However if the passive fire protection is partially
damaged, collapse may occur in the column as a result of load magnification
because of the redistribution.
To the author's knowledge this is the first piece of research that has been able to
develop a practically feasible approach to enable efficient coupled computation of
the response of structural frames to realistic fire scenarios on a freely available
open source software platform. Currently this kind of analysis can only be carried
out by just two or three large consulting firms because of the prohibitive commitment
of analyst time and effort and to a lesser extent the need for significant
computing resources. The work of this thesis will contribute enormously towards
making high-end performance based engineering of structural fire resistance a
much more practical proposition for small and medium size structural consultancies.
Furthermore, the choice of OpenSees, which is a very well respected
software framework for simulating structural response to earthquakes naturally
enables this work to be extended to the simulating the multi-hazard structural
resistance, such as in the event of a fire following an earthquake which may have
locally damaged passive fire protection
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