6,436 research outputs found
Illumination Estimation Based Color to Grayscale Conversion Algorithms
In this paper, a new adaptive approach, namelythe illumination estimation approach is introduced into the colorto grayscale conversion technique. In this approach, someassumptions will be made to calculate the weight contribution ofred, green, and blue components during the conversion process.Two color to grayscale conversion algorithms are developedunder this approach, namely the Gray World Assumption Colorto Grayscale Conversion (GWACG) and Shade of GrayAssumption Color to Grayscale (SGACG) conversion algorithms.Based on the extensive experimental results, the proposedalgorithms outperform the conventional conversion techniquesby producing resultant grayscale images with higher brightness,contrast, and amount of details preserved. For this reason, theseproposed algorithms are suitable for pre- and post- processing ofdigital images
IT-Enabled Dynamic Capability Creation: A Perspective on Exploitative vs. Explorative IT Utilization
By focusing on today’s highly competitive and rapidly changing business environment, this study theorizes how organizations can create their dynamic capability from the utilization of information technology (IT) resources. The organizational exploitation and exploration perspective is adopted as the central theoretical basis of this study. A reflection on the exploitation and exploration of organizational IT management provides the possibility for theorizing multiple paths for IT-enabled dynamic capability creation. Under our theoretical development, the multiple paths involve different types of IT utilization capabilities that, in conjunction with organizational IT resources and other non-IT factors, lead to organizational dynamic capability. This study provides a theoretical basis for the role of IT in creating organizational dynamic capability. Specifically, it reveals the multiple types of interrelations between organizational IT resources and their utilization capabilities. This study serves as a basis for further empirical studies
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Investigation of Fiber Reinforced Composite Using Multi-Material 3D Printing
Fiber reinforced composite materials have been commonly fabricated by laying and
curing the stiff and high strength fibers within tough matrix to enhance the elastic modulus.
The strength and elasticity of the fiber reinforced polymers are dependent on the intrinsic
mechanical properties of matrix and fiber, the fiber layup pattern as well as the volume
percentage of the matrix and fiber. In this paper, the effects of these factors on the 3D printed
fiber reinforced composite materials were investigated. The fiber reinforced polymers were
fabricated using multi-material inkjet printer with rubbery material as matrix and rigid strong
polymer as the fiber reinforcement. Two types of fiber layup configurations and fiber/matrix
volume ratios were designed for this study. The experimental result shows that both tensile
strength and elastic modulus of the fiber reinforced polymers could be largely enhanced by
varying the fiber/matrix ratio and layup pattern.Mechanical Engineerin
a mixed-method approach
Background Sedentary behaviours (SB) can be characterized by low energy
expenditure in a reclining position (e.g., sitting) often associated with work
and transport. Prolonged SB is associated with increased risk for chronic
conditions, and due to technological advances, the working population is in
office settings with high occupational exposure to SB. This study aims to
assess SB among office workers, as well as barriers and strategies towards
reducing SB in the work setting. Methods Using a mixed-methods approach guided
by the socio-ecological framework, non-academic office workers from a
professional school in a large public university were recruited. Of 180
eligible office workers, 40 enrolled and completed all assessments. Self-
reported and objectively measured SB and activity levels were captured. Focus
group discussion (FGD) were conducted to further understand perceptions,
barriers, and strategies to reducing workplace SB. Environmental factors were
systematically evaluated by trained research staff using an adapted version of
the Checklist for Health Promotion Environments at Worksites (CHEW). Thematic
analysis of FGD was conducted and descriptive analysis of quantitative data
was performed. Results The sample was mostly Chinese (n = 33, 80 %) with a
total of 24 (60 %) female participants. Most participants worked five days a
week for about 9.5(0.5) hrs/day. Accelerometer data show that participants
spend the majority of their days in sedentary activities both on workdays
(76.9 %) and non-workdays (69.5 %). Self-report data confirm these findings
with median sitting time of 420(180) minutes at work. From qualitative
analyses, major barriers to reducing SB emerged, including the following
themes: workplace social and cultural norms, personal factors, job scope, and
physical building/office infrastructure. CHEW results confirm a lack of
support from the physical infrastructure and information environment to
reducing SB. Conclusions There is high SB among office workers in this sample.
We identified multiple levels of influence for prolonged occupational SB, with
a particular emphasis on workplace norms and infrastructure as important
barriers to reducing SB and increasing PA. A larger, representative sample of
the Singaporean population is needed to confirm our findings but it seems that
any intervention aimed at reducing SB in the workplace should target
individual, environmental, and organizational levels
ELUCID IV: Galaxy Quenching and its Relation to Halo Mass, Environment, and Assembly Bias
We examine the quenched fraction of central and satellite galaxies as a
function of galaxy stellar mass, halo mass, and the matter density of their
large scale environment. Matter densities are inferred from our ELUCID
simulation, a constrained simulation of local Universe sampled by SDSS, while
halo masses and central/satellite classification are taken from the galaxy
group catalog of Yang et al. The quenched fraction for the total population
increases systematically with the three quantities. We find that the
`environmental quenching efficiency', which quantifies the quenched fraction as
function of halo mass, is independent of stellar mass. And this independence is
the origin of the stellar mass-independence of density-based quenching
efficiency, found in previous studies. Considering centrals and satellites
separately, we find that the two populations follow similar correlations of
quenching efficiency with halo mass and stellar mass, suggesting that they have
experienced similar quenching processes in their host halo. We demonstrate that
satellite quenching alone cannot account for the environmental quenching
efficiency of the total galaxy population and the difference between the two
populations found previously mainly arises from the fact that centrals and
satellites of the same stellar mass reside, on average, in halos of different
mass. After removing these halo-mass and stellar-mass effects, there remains a
weak, but significant, residual dependence on environmental density, which is
eliminated when halo assembly bias is taken into account. Our results therefore
indicate that halo mass is the prime environmental parameter that regulates the
quenching of both centrals and satellites.Comment: 21 pages, 16 figures, submitted to Ap
ELUCID V. Lighting dark matter halos with galaxies
In a recent study, using the distribution of galaxies in the north galactic
pole of SDSS DR7 region enclosed in a 500\mpch box, we carried out our ELUCID
simulation (Wang et al. 2016, ELUCID III). Here we {\it light} the dark matter
halos and subhalos in the reconstructed region in the simulation with galaxies
in the SDSS observations using a novel {\it neighborhood} abundance matching
method. Before we make use of thus established galaxy-subhalo connections in
the ELUCID simulation to evaluate galaxy formation models, we set out to
explore the reliability of such a link. For this purpose, we focus on the
following a few aspects of galaxies: (1) the central-subhalo luminosity and
mass relations; (2) the satellite fraction of galaxies; (3) the conditional
luminosity function (CLF) and conditional stellar mass function (CSMF) of
galaxies; and (4) the cross correlation functions between galaxies and the dark
matter particles, most of which are measured separately for all, red and blue
galaxy populations. We find that our neighborhood abundance matching method
accurately reproduces the central-subhalo relations, satellite fraction, the
CLFs and CSMFs and the biases of galaxies. These features ensure that thus
established galaxy-subhalo connections will be very useful in constraining
galaxy formation processes. And we provide some suggestions on the three levels
of using the galaxy-subhalo pairs for galaxy formation constraints. The
galaxy-subhalo links and the subhalo merger trees in the SDSS DR7 region
extracted from our ELUCID simulation are available upon request.Comment: 18 pages, 13 figures, ApJ accepte
Full-sky ray-tracing simulation of weak lensing using ELUCID simulations: exploring galaxy intrinsic alignment and cosmic shear correlations
The intrinsic alignment of galaxies is an important systematic effect in
weak-lensing surveys, which can affect the derived cosmological parameters. One
direct way to distinguish different alignment models and quantify their effects
on the measurement is to produce mocked weak-lensing surveys. In this work, we
use full-sky ray-tracing technique to produce mock images of galaxies from the
ELUCID -body simulation run with the WMAP9 cosmology. In our model we assume
that the shape of central elliptical galaxy follows that of the dark matter
halo, and spiral galaxy follows the halo spin. Using the mocked galaxy images,
a combination of galaxy intrinsic shape and the gravitational shear, we compare
the predicted tomographic shear correlations to the results of KiDS and DLS. It
is found that our predictions stay between the KiDS and DLS results. We rule
out a model in which the satellite galaxies are radially aligned with the
center galaxy, otherwise the shear-correlations on small scales are too high.
Most important, we find that although the intrinsic alignment of spiral
galaxies is very weak, they induce a positive correlation between the
gravitational shear signal and the intrinsic galaxy orientation (GI). This is
because the spiral galaxy is tangentially aligned with the nearby large-scale
overdensity, contrary to the radial alignment of elliptical galaxy. Our results
explain the origin of detected positive GI term from the weak-lensing surveys.
We conclude that in future analysis, the GI model must include the dependence
on galaxy types in more detail.Comment: 23 pages, 13 figures, published in ApJ. Our mock galaxy catalog is
available upon request by email to the author ([email protected],
[email protected]
A bifunctional kinase–phosphatase module balances mitotic checkpoint strength and kinetochore–microtubule attachment stability
Point singularity array with metasurfaces
Phase singularities are loci of darkness surrounded by monochromatic light in
a scalar field, with applications in optical trapping, super-resolution
imaging, and structured light-matter interactions. Although 1D singular
structures, such as optical vortices, are the most common due to their robust
topological properties, uncommon 0D (point) and 2D (sheet) singular structures
can be generated by wavefront-shaping devices such as metasurfaces. Here, using
the design flexibility of metasurfaces, we deterministically position ten
identical point singularities in a cylindrically symmetric field generated by a
single illumination source. The phasefront is inverse-designed using phase
gradient maximization with an automatically-differentiable propagator. This
process produces tight longitudinal intensity confinement. The singularity
array is experimentally realized with a 1 mm diameter TiO2 metasurface. One
possible application is blue-detuned neutral atom trap arrays, for which this
light field would enforce 3D confinement and a potential depth around 0.22 mK
per watt of incident trapping laser power. Metasurface-enabled point
singularity engineering may significantly simplify and miniaturize the optical
architecture required to produce super-resolution microscopes and dark traps
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