6,225 research outputs found
Reducing the inductors of rectifiers having two outputs to improve power density
In this paper, a recently reported single-phase rectifier with two outputs (RECTO) is improved to reduce the neutral inductor and the grid inductor, by moving the neutral inductor away from the path of the grid current. The neutral inductor does not carry the grid current any more so the current stress of the neutral inductor can be significantly reduced, and the size of the inductor becomes much smaller. In theory, the current stress can be reduced by at least three times and the size of the inductor can be reduced by nine times. At the same time, the grid inductor can be reduced to achieve the same level of grid-current switching ripples because of the changed operation modes and modulation strategy. Together, the reduced neutral and grid inductors help improve the system power density. It is worth noting that the voltage and current stresses of the switches and the other features of the RECTO, e.g., two dc outputs and unity power factor, are not affected. Comparative experimental results are presented to demonstrate the reduction. If the two load currents are the same then the neutral inductor is only required to handle the switching ripples. This improved RECTO is particularly suitable for applications with two balanced loads without increasing the cost much
Missing Corner in the Sky: Massless Three-Point Celestial Amplitudes
We study three-point celestial amplitudes in Minkowski space for massless
scalars, photons, gluons, and gravitons. The corresponding scattering
amplitudes in the plane wave basis vanish for generic momenta due to momentum
conservation. However, the delta function for the momentum conservation has
support in the soft and colinear regions, and contributes to the Mellin and
shadow integrals that give non-zero celestial amplitudes. We show that the
amplitudes with the incoming (outgoing) particles in the (shadow) conformal
basis take the standard form of correlators in two-dimensional conformal field
theory. In particular, the three-point celestial gluon amplitudes take the form
of a three-point function of a spin-one current with two spin-one primary
operators, which strongly supports the relation between soft spinning particles
and conserved currents. Moreover, the three-point celestial amplitudes of one
graviton and two massless scalars take the form of a correlation function
involving a primary operator of conformal weight one and spin two, whose
level-one descendent is the supertranslation current
Matrix Formulation of Hamiltonian Structures of Constrained KP Hierarchy
We give a matrix formulation of the Hamiltonian structures of constrained KP
hierarchy. First, we derive from the matrix formulation the Hamiltonian
structure of the one-constraint KP hierarchy, which was originally obtained by
Oevel and Strampp. We then generalize the derivation to the multi-constraint
case and show that the resulting bracket is actually the second Gelfand-Dickey
bracket associated with the corresponding Lax operator. The matrix formulation
of the Hamiltonian structure of the one-constraint KP hierarchy in the form
introduced in the study of matrix model is also discussedComment: 19 pages, Revtex, no figures. Minor changes, reference correcte
THE INTELLECTUAL CORE KNOWLEDGE OF THE MOBILE INFORMATION SYSTEM
O2O, an acronym of online-to-offline or vice versa, is a new business model blending online retailing with offline retailing. This new model improves an existing method of shopping by either integrating the online components for traditional shoppers or the traditional shopping for Internet or mobile shoppers. Few studies have examined consumers’ acceptance of new O2O business model. Therefore, this study attempts to investigate consumer acceptance of O2O business model from the status quo bias and habit perspectives that have been used to examine new system acceptance by past research. Using a sample data collected from 230 respondents, this study applies a structural equation model (SEM) to examine the relationships of the proposed research model. The results reveal that behavioural-based inertia positively impacts perceived ease of use and cognitive-based inertia positively impacts relative advantage, and consequently impacts consumers’ intention to use O2O shopping. In addition, subjective norm positively impacts perceived ease of use and relative advantage, and self-efficacy positively impacts perceived ease of use. Because O2O shopping is a consumer’s adoption of a new business model which involves information technologies and retailing services, this study thus provides in depth insights into enhancing the acceptance of both new information technologies and new business model. Particularly, inertia can facilitate consumers O2O shopping acceptance as opposed to inhibit new system acceptance found in past research. Perceived ease of use and relative advantage fully mediate the relationships between external variables (such as inertia, subjective norm, and self-efficacy) and O2O shopping intention. Implications are drawn for electronic commerce, mobile commerce, and retailing
Probing isospin- and momentum-dependent nuclear effective interactions in neutron-rich matter
The single-particle potentials for nucleons and hyperons in neutron-rich
matter generally depends on the density and isospin asymmetry of the medium as
well as the momentum and isospin of the particle. It further depends on the
temperature of the matter if the latter is in thermal equilibrium. We review
here the extension of a Gogny-type isospin- and momentum-dependent interaction
in several aspects made in recent years and their applications in studying
intermediate-energy heavy ion collisions, thermal properties of asymmetric
nuclear matter and properties of neutron stars. The importance of the isospin-
and momentum-dependence of the single-particle potential, especially the
momentum dependence of the isovector potential, is clearly revealed throughout
these studies.Comment: 27 pages, 19 figures, 1 table, accepted version to appear in EPJA
special volume on Nuclear Symmetry Energ
Tailoring excitonic states of van der Waals bilayers through stacking configuration, band alignment and valley-spin
Excitons in monolayer semiconductors have large optical transition dipole for
strong coupling with light field. Interlayer excitons in heterobilayers, with
layer separation of electron and hole components, feature large electric dipole
that enables strong coupling with electric field and exciton-exciton
interaction, at the cost that the optical dipole is substantially quenched (by
several orders of magnitude). In this letter, we demonstrate the ability to
create a new class of excitons in transition metal dichalcogenide (TMD) hetero-
and homo-bilayers that combines the advantages of monolayer- and
interlayer-excitons, i.e. featuring both large optical dipole and large
electric dipole. These excitons consist of an electron that is well confined in
an individual layer, and a hole that is well extended in both layers, realized
here through the carrier-species specific layer-hybridization controlled
through the interplay of rotational, translational, band offset, and
valley-spin degrees of freedom. We observe different species of such
layer-hybridized valley excitons in different heterobilayer and homobilayer
systems, which can be utilized for realizing strongly interacting
excitonic/polaritonic gases, as well as optical quantum coherent controls of
bidirectional interlayer carrier transfer either with upper conversion or down
conversion in energy
UA-DETRAC: A New Benchmark and Protocol for Multi-Object Detection and Tracking
In recent years, numerous effective multi-object tracking (MOT) methods are
developed because of the wide range of applications. Existing performance
evaluations of MOT methods usually separate the object tracking step from the
object detection step by using the same fixed object detection results for
comparisons. In this work, we perform a comprehensive quantitative study on the
effects of object detection accuracy to the overall MOT performance, using the
new large-scale University at Albany DETection and tRACking (UA-DETRAC)
benchmark dataset. The UA-DETRAC benchmark dataset consists of 100 challenging
video sequences captured from real-world traffic scenes (over 140,000 frames
with rich annotations, including occlusion, weather, vehicle category,
truncation, and vehicle bounding boxes) for object detection, object tracking
and MOT system. We evaluate complete MOT systems constructed from combinations
of state-of-the-art object detection and object tracking methods. Our analysis
shows the complex effects of object detection accuracy on MOT system
performance. Based on these observations, we propose new evaluation tools and
metrics for MOT systems that consider both object detection and object tracking
for comprehensive analysis.Comment: 18 pages, 11 figures, accepted by CVI
A Fringe Center Detection Technique Based on a Sub-Pixel Resolution, and Its Applications Using Sinusoidal Gratings
A common problem in optical profilometry is the accuracy in locating fringe centers. This paper presents an accurate fringe center detection technique based on sub-pixel resolution using the fringe projection method. An optimum reconstruction filter is developed which has low sensitivity to noise. In fringe center detection, computer simulation results of using one-pixel and sub-pixel resolutions are compared. The detection technique is then applied to radius measurement of cylindrical objects and surface profile measurement of diffuse objects. The experimental results thus obtained through the proposed optimum reconstruction filter show significant improvement in measurement accuracy
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