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130 results on '"Sung, L.-Y."'

1. A semi-periodic initial-value problem for the Kadomtsev-Petviashvili II equation

Author

Kalamvokas, P., Papageorgiou, V. G., Fokas, A. S., and Sung, L. -Y.

Subjects
Mathematics - Analysis of PDEs, Mathematical Physics, Nonlinear Sciences - Exactly Solvable and Integrable Systems, 35Q53, 35Q15, 35Q35, 58F07
Abstract

We investigate the Cauchy problem on the cylinder, namely the semi-periodic problem where there is periodicity in the $x$-direction and decay in the $y$-direction, for the Kadomtsev-Petviashvili II equation by the inverse spectral transform method. For initial data with small $L^1$ and $L^2$ norms, assuming the zero mass constraint, this initial-value problem is reduced to a Riemann-Hilbert problem on the boundary of certain infinite strips with shift.

Published
2023

23. Inter-filament interaction between IMPDH and CTPS cytoophidia

Author

Chang, C-C, Keppeke, GD, Sung, L-Y, and Liu, J-L

Abstract

Inosine monophosphate dehydrogenase (IMPDH) and cytidine triphosphate synthase (CTPS) are two metabolic enzymes that perform rate-limiting steps in the de novo synthesis of purine and pyrimidine nucleotides, respectively. It has been shown that IMPDH and CTPS can comprise a filamentous macrostructure termed the cytoophidium, which may play a role in regulation of their catalytic activity. Although these two proteins may colocalise in the same cytoophidium, how they associate with one another is still elusive. As reported herein, we established a model HeLa cell line co-expressing OFP-tagged IMPDH2 and GFP-tagged CTPS1 and recorded the assembly, disassembly and movement of the cytoophidium in live cells. Moreover, by using super-resolution confocal imaging, we demonstrate how IMPDH- and CTPS-based filaments are aligned or intertwined in the mixed cytoophidium. Collectively, our findings provide a panorama of cytoophidium dynamics and suggest that IMPDH and CTPS cytoophidia may coordinate by inter-filament interaction. This article is protected by copyright. All rights reserved.

Published
2018

26. The short-term prediction of universal time and length of day using atmospheric angular momentum

Author

Freedman, A. P, Steppe, J. A, Dickey, J. O, Eubanks, T. M, and Sung, L.-Y

Subjects
Geophysics
Abstract

The ability to predict short-term variations in the Earth's rotation has gained importance in recent years owing to more precise spacecraft tracking requirements. Universal time (UT1), that component of the Earth's orientation corresponding to the rotation angle, can be measured by number of high-precision space geodetic techniques. A Kalman filter developed at the Jet Propulsion Laboratory (JPL) optimally combines these different data sets and generates a smoothed times series and a set of predictions for UT1, as well as for additional Earth orientation components. These UT1 predictions utilize an empirically derived random walk stochastic model for the length of the day (LOD) and require frequent and up-to-date measurements of either UT1 or LOD to keep errors from quickly accumulating. Recent studies have shown that LOD variations are correlated with changes in the Earth's axial atmospheric angular momentum (AAM) over timescales of several years down to as little as 8 days. AAM estimates and forecasts out to 10 days are routinely available from meteorological analysis centers; these data can supplement geodetic measurements to improve the short-term prediction of LOD and have therefore been incorporated as independent data types in the JPL Kalman filter. We find that AAM and, to a lesser extent, AAM forecast data are extremely helpful in generating accurate near-real-time estimates of UT1 and LOD and in improving short-term predictions of these quantities out to about 10 days.

Published
1994
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28. The Short-Term Prediction of Universal Time and Length-Of-Day Using Atmospheric Angular Momemtum

Author

Freedman, A. P, Steppe, J. A, Dickey, J. O, Eubanks, T. M, and Sung, L. Y

Abstract

Methods to combine the diverse set of geodetic measurements of Earth orientation that are currently available, and to interpolate and extrapolate these data to generate an optimal estimate of Earth orientation, have been under development at JPL for a number of years. The strategy currently in use is a Kalman filtering scheme based on Earth orentation parameters and their excitation functions that incorporates stochastic models of the important physical processes and takes into account the variable form, quality, and temporal density of the data provided by diffent measurement services.

Published
1993

31. Hodge decomposition for two-dimensional time-harmonic Maxwell's equations: impedance boundary condition.

Author

Brenner, S. C., Gedicke, J., and Sung, L. ‐Y.

Subjects
MAXWELL equations, BOUNDARY value problems, ELECTROMAGNETIC fields, MAGNETIC permeability, DECOMPOSITION method
Abstract

We extend the Hodge decomposition approach for the cavity problem of two-dimensional time-harmonic Maxwell's equations to include the impedance boundary condition, with anisotropic electric permittivity and sign-changing magnetic permeability. We derive error estimates for a P1 finite element method based on the Hodge decomposition approach and present results of numerical experiments that involve metamaterials and electromagnetic cloaking. The well-posedness of the cavity problem when both electric permittivity and magnetic permeability can change sign is also discussed. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2017
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44. Three-dimensional adjustment of trilateration data

Author

Sung, L.-Y and Jackson, D. D

Subjects
Geophysics
Abstract

The three-dimensional locations of the monuments in the USGS Hollister trilateration network were adjusted to fit line length observations observed in 1977, using a Bayesian approach, and incorporating prior elevation estimates as data in the adjustment procedure. No significant discrepancies in the measured line lengths were found, but significant elevation adjustments (up to 1.85 m) were needed to fit the length data.

Published
1985

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