945 research outputs found
When Does a Firm Have Faster Speed Despite Inferior Capability? Disintegrating Capability and Incentive Effects When Examining Firm Speed
Firm speed has long been a construct of interest among managers and researchers. Although both a firmโs capabilities and incentives to be fast determine observed firm speed, practitioners and academic scholars have typically focused on the capability mechanism alone. However, the omission of incentives in understanding firm speed can lead to mistaking faster firm speed for superior firm capability. To address this shortcoming, we develop a theoretical framework considering both capabilities and incentives simultaneously to examine faster firm speed. Our developed framework allows us to discern whether superior capabilities or greater incentives lead to a faster speed. We also show how to apply our framework to empirical analysis by analyzing actual firm data in the Liquefied Natural Gas industry from 1996 to 2007. In this way, the current paper contributes to the literature on firm speed by providing a theoretical framework that enables a more nuanced understanding of firm speed
Stochastic Processes and the Dirac Equation with External Fields
The equation describing the stochastic motion of a classical particle in
1+1-dimensional space-time is connected to the Dirac equation with external
gauge fields. The effects of assigning different turning probabilities to the
forward and the backward moving particles in time are discussed.Comment: 9 pages, 1 figure, scalar parts eliminate
k-Space Deep Learning for Reference-free EPI Ghost Correction
Nyquist ghost artifacts in EPI are originated from phase mismatch between the
even and odd echoes. However, conventional correction methods using reference
scans often produce erroneous results especially in high-field MRI due to the
non-linear and time-varying local magnetic field changes. Recently, it was
shown that the problem of ghost correction can be reformulated as k-space
interpolation problem that can be solved using structured low-rank Hankel
matrix approaches. Another recent work showed that data driven Hankel matrix
decomposition can be reformulated to exhibit similar structures as deep
convolutional neural network. By synergistically combining these findings, we
propose a k-space deep learning approach that immediately corrects the phase
mismatch without a reference scan in both accelerated and non-accelerated EPI
acquisitions. To take advantage of the even and odd-phase directional
redundancy, the k-space data is divided into two channels configured with even
and odd phase encodings. The redundancies between coils are also exploited by
stacking the multi-coil k-space data into additional input channels. Then, our
k-space ghost correction network is trained to learn the interpolation kernel
to estimate the missing virtual k-space data. For the accelerated EPI data, the
same neural network is trained to directly estimate the interpolation kernels
for missing k-space data from both ghost and subsampling. Reconstruction
results using 3T and 7T in-vivo data showed that the proposed method
outperformed the image quality compared to the existing methods, and the
computing time is much faster.The proposed k-space deep learning for EPI ghost
correction is highly robust and fast, and can be combined with acceleration, so
that it can be used as a promising correction tool for high-field MRI without
changing the current acquisition protocol.Comment: To appear in Magnetic Resonance in Medicin
(E)-2,2โฒ-[3-(2-Nitroยญphenยญyl)prop-2-ene-1,1-diยญyl]bisยญ(3-hyยญdroxyยญcycloยญhex-2-en-1-one)
In the title compound, C21H21NO6, each of the cycloยญhexenone rings adopts a half-chair conformation. Each of the pairs of hyยญdroxy and carbonyl O atoms are oriented to allow for the formation of intraยญmolecular OโHโฏO hydrogen bonds, which are typical of xanthene derivatives
A Passivity-based Nonlinear Admittance Control with Application to Powered Upper-limb Control under Unknown Environmental Interactions
This paper presents an admittance controller based on the passivity theory
for a powered upper-limb exoskeleton robot which is governed by the nonlinear
equation of motion. Passivity allows us to include a human operator and
environmental interaction in the control loop. The robot interacts with the
human operator via F/T sensor and interacts with the environment mainly via
end-effectors. Although the environmental interaction cannot be detected by any
sensors (hence unknown), passivity allows us to have natural interaction. An
analysis shows that the behavior of the actual system mimics that of a nominal
model as the control gain goes to infinity, which implies that the proposed
approach is an admittance controller. However, because the control gain cannot
grow infinitely in practice, the performance limitation according to the
achievable control gain is also analyzed. The result of this analysis indicates
that the performance in the sense of infinite norm increases linearly with the
control gain. In the experiments, the proposed properties were verified using 1
degree-of-freedom testbench, and an actual powered upper-limb exoskeleton was
used to lift and maneuver the unknown payload.Comment: Accepted in IEEE/ASME Transactions on Mechatronics (T-MECH
The Development of Recurrent Choroidal Neovascularization in a Patient with Choroidal Coloboma
We report a case of recurrent choroidal neovascularization (CNV) in an eye with chorioretinal coloboma. A 36-year-old woman presented complaining of decreased visual acuity (VA) in her left eye. Best corrected visual acuity (BCVA) was 20/200 and iris coloboma was observed. Funduscopy and fluorescein angiography (FA) showed CNV in the superior extrafoveal region with chorioretinal coloboma reaching just inferior to the optic disc. No other cause for CNV was observed except for the chorioretinal coloboma. BCVA improved to 20/30 after laser photocoagulation. She revisited our clinic for deteriorating VA (20/400) in the same eye 3 years after treatment. Funduscopy and FA demonstrated recurrent CNV with subfoveal hemorrhage. Photodynamic therapy (PDT) was followed by three consecutive intravitreal bevacizumab injections (IVB) for the subfoveally-located CNV. However, the CNV persisted with the appearance of a fresh subretinal hemorrhage. Additional PDT was combined with IVB on the same day 6 months after the initial PDT. The CNV regressed 3 months after treatment and has not recurred as of 8 months after the last treatment. The patient's BCVA improved to 20/60. This case suggests that PDT combined with IVB can be an alternative treatment for the management of recurrent CNV after laser photocoagulation in eyes with chorioretinal coloboma
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