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828 results on '"Lee, Sun"'

1. Stability and Robustness of Time-discretization Schemes for the Allen-Cahn Equation via Bifurcation and Perturbation Analysis

Author

Hao, Wenrui, Lee, Sun, Xu, Xiaofeng, and Xu, Zhiliang

Subjects
Mathematics - Numerical Analysis, 65M12, 35Q99, 35A35
Abstract

The Allen-Cahn equation is a fundamental model for phase transitions, offering critical insights into the dynamics of interface evolution in various physical systems. This paper investigates the stability and robustness of frequently utilized time-discretization numerical schemes for solving the Allen-Cahn equation, with focuses on the Backward Euler, Crank-Nicolson (CN), convex splitting of modified CN, and Diagonally Implicit Runge-Kutta (DIRK) methods. Our stability analysis reveals that the Convex Splitting of the Modified CN scheme exhibits unconditional stability, allowing greater flexibility in time step selection, while the other schemes are conditionally stable. Additionally, our robustness analysis highlights that the Backward Euler method converges to correct physical solutions regardless of initial conditions. In contrast, the other methods studied in this work show sensitivity to initial conditions and may converge to incorrect physical solutions if the initial conditions are not carefully chosen. This study introduces a comprehensive approach to assessing stability and robustness in numerical methods for solving the Allen-Cahn equation, providing a new perspective for evaluating numerical techniques for general nonlinear differential equations.

Published
2024

2. Merging bound states in the continuum at third-order $\Gamma$ point enabled by controlling Fourier harmonic components in lattice parameters

Author

Lee, Sun-Goo, Kim, Seong-Han, and Lee, Wook-Jae

Subjects
Physics - Optics
Abstract

Recent studies have demonstrated that ultrahigh-$Q$ resonances, which are robust to fabrication imperfections, can be realized by merging multiple bound states in the continuum (BICs) in momentum space. The merging of multiple BICs holds significant promise for practical applications, providing a robust means to attain ultrahigh-$Q$ resonances that greatly enhance light-matter interactions. In this study, we introduce a novel approach to achieve the merging of BICs at the edges of the fourth stop band, which opens at the third-order $\Gamma$ point, in one-dimensional leaky-mode photonic lattices. Photonic band gaps and BICs arise from periodic modulations in lattice parameters. However, near the third-order $\Gamma$ point, out-of-plane radiation arises by the first and second Fourier harmonic components in the lattice parameters. Accidental BICs can emerge at specific $k$ points where an optimal balance exists between these two Fourier harmonic components. We demonstrate that these accidental BICs are topologically stable, and their positions in momentum space can be precisely controlled by adjusting a specific lattice parameter that influences the strength of the first and second Fourier harmonic components. Furthermore, we show that accidental BICs can be merged at the third-order $\Gamma$ point, with or without a symmetry-protected BIC, by finely adjusting this specific lattice parameter while keeping other parameters constant.

Published
2024

31. Hiding and Seeking Knowledge-Providing Ties from Rivals: A Strategic Perspective on Network Perceptions.

Author

Kilduff, Martin, Wang, Kun, Lee, Sun Young, Tsai, Wenpin, Chuang, You-Ta, and Tsai, Fu-Sheng

Subjects
COMPETITION (Psychology), DECEPTION, COWORKER relationships, SOCIAL perception, MOTIVATION (Psychology), SOCIAL status, SOCIAL cohesion, ORGANIZATIONAL behavior
Abstract

Rivalry is endemic in society and organizations, fueling competitive intentions and behaviors. According to social network theory, rivalry emerges among people who, like siblings, have many of the same connections to others. For this structurally equivalent rivalry to have its effects, the individual must see the other person as a rival. We ask whether, in the context of competition, people seek to identify the knowledge providers of their rivals while striving to hide their own knowledge providers from perceived rivals. We conducted two experiments that showed, for the first time, that structural equivalence does induce feelings of rivalry and does lead people to take action with respect to perceived rivals, namely to hide and seek knowledge providers. Our analysis of time-separated social network and outcome data from all 73 employees in the headquarters of a chemical company found support for these patterns of hiding and seeking in relation to perceived rivals. We also found limited evidence that career outcomes may be influenced by individuals' success in hiding and seeking. Bringing together research on rivalry and network cognition, we provide a new approach to the strategic deployment of deception and detection in social networks. [ABSTRACT FROM AUTHOR]

Published
2024
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47. Environmental Factors Associated With Risk of Crohn’s Disease Development in the Crohn’s and Colitis Canada - Genetic, Environmental, Microbial Project

Author

Abreu, Maria, Beck, Paul, Bernstein, Charles, Croitoru, Kenneth, Dieleman, Levinus A., Feagan, Brian, Griffiths, Anne, Guttman, David, Jacobson, Kevan, Kaplan, Gilaad, Krause, Denis O., Madsen, Karen, Marshall, John, Moayyedi, Paul, Ropeleski, Mark, Seidman, Ernest, Silverberg, Mark, Snapper, Scott, Stadnyk, Andy, Steinhart, Hillary, Surette, Michael, Turner, Dan, Walters, Thomas, Vallance, Bruce, Aumais, Guy, Bitton, Alain, Cino, Maria, Critch, Jeff, Denson, Lee, Deslandres, Colette, El-Matary, Wael, Herfarth, Hans, Higgins, Peter, Huynh, Hien, Hyams, Jeffrey S., Mack, David, McGrath, Jerry, Otley, Anthony, Panancionne, Remo, Xue, Mingyue, Leibovitzh, Haim, Jingcheng, Shao, Neustaeter, Anna, Dong, Mei, Xu, Wei, Espin-Garcia, Osvaldo, Griffiths, Anne M., Steinhart, A. Hillary, Huynh, Hien Q., Panaccione, Remo, Bressler, Brian, Murthy, Sanjay, Marshall, John K., Bernstein, Charles N., Fich, Alexander, Denson, Lee A., Ropeleski, Mark J., Abreu, Maria T., Avni-Biron, Irit, Lee, Sun-Ho, and Turpin, Williams

Published
2024
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48. an-QNA: An Adaptive Nesterov Quasi-Newton Acceleration-Optimized CMOS LNA for 65 nm Automotive Radar Applications

Author

Unal Aras, Lee Sun Woo, Tahesin Samira Delwar, Abrar Siddique, Anindya Jana, Yangwon Lee, and Jee-Youl Ryu

Subjects
adaptive Nesterov quasi-Newton acceleration (an-QNA), conventional quasi-newton (c-QN), global convergence, highly linear, low-noise amplifier (LNA), improved post-linearization (IPL), Chemical technology, TP1-1185
Abstract

An adaptive Nesterov quasi-Newton acceleration (an-QNA)-optimized low-noise amplifier (LNA) is proposed in this paper. An optimized single-ended-to-differential two-stage LNA circuit is presented. It includes an improved post-linearization (IPL) technique to enhance the linearity. Traditional methods like conventional quasi-Newton (c-QN) often suffer from slow convergence and the tendency to get trapped in local minima. However, the proposed an-QNA method significantly accelerates the convergence speed. Furthermore, in this paper, modifications have been made to the an-QNA algorithm using a quadratic estimation to guarantee global convergence. The optimized an-QNA-based LNA, using standard 65 nm CMOS technology, achieves a simulated gain of 17.5 dB, a noise figure (NF) of 3.7 dB, and a 1 dB input compression point (IP1dB) of −13.1 dBm. It is also noted that the optimized LNA achieves a measured gain of 12.9 dB and an NF of 4.98 dB, and the IP1dB is −17.8 dB. The optimized LNA has a chip area of 0.67 mm2.

Published
2024
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