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1,593 results on '"Lee, Chang Hun"'

1. Model Predictive Guidance for Fuel-Optimal Landing of Reusable Launch Vehicles

Author

Jung, Ki-Wook, Lee, Sang-Don, Jung, Cheol-Goo, and Lee, Chang-Hun

Subjects
Electrical Engineering and Systems Science - Systems and Control
Abstract

This paper introduces a landing guidance strategy for reusable launch vehicles (RLVs) using a model predictive approach based on sequential convex programming (SCP). The proposed approach devises two distinct optimal control problems (OCPs): planning a fuel-optimal landing trajectory that accommodates practical path constraints specific to RLVs, and determining real-time optimal tracking commands. This dual optimization strategy allows for reduced computational load through adjustable prediction horizon lengths in the tracking task, achieving near closed-loop performance. Enhancements in model fidelity for the tracking task are achieved through an alternative rotational dynamics representation, enabling a more stable numerical solution of the OCP and accounting for vehicle transient dynamics. Furthermore, modifications of aerodynamic force in both planning and tracking phases are proposed, tailored for thrust-vector-controlled RLVs, to reduce the fidelity gap without adding computational complexity. Extensive 6-DOF simulation experiments validate the effectiveness and improved guidance performance of the proposed algorithm.

Published
2024

2. Connections between Reachability and Time Optimality

Author

Bae, Juho, Bai, Ji Hoon, Lee, Byung-Yoon, Lee, Jun-Yong, and Lee, Chang-Hun

Subjects
Mathematics - Optimization and Control, Electrical Engineering and Systems Science - Systems and Control
Abstract

This paper presents the concept of an equivalence relation between the set of optimal control problems. By leveraging this concept, we show that the boundary of the reachability set can be constructed by the solutions of time optimal problems. Alongside, a more generalized equivalence theorem is presented together. The findings facilitate the use of solution structures from a certain class of optimal control problems to address problems in corresponding equivalent classes. As a byproduct, we state and prove the construction methods of the reachability sets of three-dimensional curves with prescribed curvature bound. The findings are twofold: Firstly, we prove that any boundary point of the reachability set, with the terminal direction taken into account, can be accessed via curves of H, CSC, CCC, or their respective subsegments, where H denotes a helicoidal arc, C a circular arc with maximum curvature, and S a straight segment. Secondly, we show that any boundary point of the reachability set, without considering the terminal direction, can be accessed by curves of CC, CS, or their respective subsegments. These findings extend the developments presented in literature regarding planar curves, or Dubins car dynamics, into spatial curves in $\mathbb{R}^3$. For higher dimensions, we confirm that the problem of identifying the reachability set of curvature bounded paths subsumes the well-known Markov-Dubins problem. These advancements in understanding the reachability of curvature bounded paths in $\mathbb{R}^3$ hold significant practical implications, particularly in the contexts of mission planning problems and time optimal guidance., Comment: Submitted to Automatica

Published
2024

3. Osteoporosis Prediction from Hand and Wrist X-rays using Image Segmentation and Self-Supervised Learning

Author

Lee, Hyungeun, Hwang, Ung, Yu, Seungwon, Lee, Chang-Hun, and Yoon, Kijung

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Computer Science - Computer Vision and Pattern Recognition
Abstract

Osteoporosis is a widespread and chronic metabolic bone disease that often remains undiagnosed and untreated due to limited access to bone mineral density (BMD) tests like Dual-energy X-ray absorptiometry (DXA). In response to this challenge, current advancements are pivoting towards detecting osteoporosis by examining alternative indicators from peripheral bone areas, with the goal of increasing screening rates without added expenses or time. In this paper, we present a method to predict osteoporosis using hand and wrist X-ray images, which are both widely accessible and affordable, though their link to DXA-based data is not thoroughly explored. Initially, our method segments the ulnar, radius, and metacarpal bones using a foundational model for image segmentation. Then, we use a self-supervised learning approach to extract meaningful representations without the need for explicit labels, and move on to classify osteoporosis in a supervised manner. Our method is evaluated on a dataset with 192 individuals, cross-referencing their verified osteoporosis conditions against the standard DXA test. With a notable classification score (AUC=0.83), our model represents a pioneering effort in leveraging vision-based techniques for osteoporosis identification from the peripheral skeleton sites., Comment: Extended Abstract presented at Machine Learning for Health (ML4H) symposium 2023, December 10th, 2023, New Orleans, United States, 10 pages

Published
2023

7. Attitude Takeover Control for Noncooperative Space Targets Based on Gaussian Processes with Online Model Learning

Author

Liu, Yuhan, Wang, Pengyu, Lee, Chang-Hun, and Tóth, Roland

Subjects
Electrical Engineering and Systems Science - Systems and Control
Abstract

One major challenge for autonomous attitude takeover control for on-orbit servicing of spacecraft is that an accurate dynamic motion model of the combined vehicles is highly nonlinear, complex and often costly to identify online, which makes traditional model-based control impractical for this task. To address this issue, a recursive online sparse Gaussian Process (GP)-based learning strategy for attitude takeover control of noncooperative targets with maneuverability is proposed, where the unknown dynamics are online compensated based on the learnt GP model in a semi-feedforward manner. The method enables the continuous use of on-orbit data to successively improve the learnt model during online operation and has reduced computational load compared to standard GP regression. Next to the GP-based feedforward, a feedback controller is proposed that varies its gains based on the predicted model confidence, ensuring robustness of the overall scheme. Moreover, rigorous theoretical proofs of Lyapunov stability and boundedness guarantees of the proposed method-driven closed-loop system are provided in the probabilistic sense. A simulation study based on a high-fidelity simulator is used to show the effectiveness of the proposed strategy and demonstrate its high performance., Comment: 17 pages, 14 figures. Submitted to in IEEE Transactions on Aerospace and Electronic Systems

Published
2023

14. MPPI Control-Based Adaptive Pursuit Guidance for Path-Following Control of Quadrotors in the Presence of Wind Disturbances

Author

Jeong, Eui-Taek, Lee, Sang-Don, Na, Kyung-Mi, Lee, Chang-Hun, Kacprzyk, Janusz, Series Editor, Gomide, Fernando, Advisory Editor, Kaynak, Okyay, Advisory Editor, Liu, Derong, Advisory Editor, Pedrycz, Witold, Advisory Editor, Polycarpou, Marios M., Advisory Editor, Rudas, Imre J., Advisory Editor, Wang, Jun, Advisory Editor, Jo, Jun, editor, Choi, Han-Lim, editor, Helbig, Marde, editor, Oh, Hyondong, editor, Hwangbo, Jemin, editor, Lee, Chang-Hun, editor, and Stantic, Bela, editor

Published
2023
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15. Nonlinear Autoregressive with Gaussian Process Regression-Based Path-Following Guidance for UAV Under Time-Varying Disturbances

Author

Yoon, Dain, Kim, Young-Won, Kim, Boseok, Lee, Chang-Hun, Kacprzyk, Janusz, Series Editor, Gomide, Fernando, Advisory Editor, Kaynak, Okyay, Advisory Editor, Liu, Derong, Advisory Editor, Pedrycz, Witold, Advisory Editor, Polycarpou, Marios M., Advisory Editor, Rudas, Imre J., Advisory Editor, Wang, Jun, Advisory Editor, Jo, Jun, editor, Choi, Han-Lim, editor, Helbig, Marde, editor, Oh, Hyondong, editor, Hwangbo, Jemin, editor, Lee, Chang-Hun, editor, and Stantic, Bela, editor

Published
2023
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16. Estimation of Aerodynamic Uncertainty in Missile System Using Physics-Informed Neural Network Framework

Author

Na, Kyung-Mi, Park, Jongchan, Jung, Ki-Wook, Lee, Chang-Hun, Kacprzyk, Janusz, Series Editor, Gomide, Fernando, Advisory Editor, Kaynak, Okyay, Advisory Editor, Liu, Derong, Advisory Editor, Pedrycz, Witold, Advisory Editor, Polycarpou, Marios M., Advisory Editor, Rudas, Imre J., Advisory Editor, Wang, Jun, Advisory Editor, Jo, Jun, editor, Choi, Han-Lim, editor, Helbig, Marde, editor, Oh, Hyondong, editor, Hwangbo, Jemin, editor, Lee, Chang-Hun, editor, and Stantic, Bela, editor

Published
2023
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22. Anomaly Detection for Monte-Carlo Simulation Data of Missile Control System

Author

Jung, Ki-Wook, Lee, Chang-Hun, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Lee, Sangchul, editor, Han, Cheolheui, editor, Choi, Jeong-Yeol, editor, Kim, Seungkeun, editor, and Kim, Jeong Ho, editor

Published
2023
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23. Legendre Pseudo-Spectral Method for Missile Trajectory Optimization with Free Final Time

Author

Jung, Cheol-Goo, Lee, Chang-Hun, Tahk, Min-Jea, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Lee, Sangchul, editor, Han, Cheolheui, editor, Choi, Jeong-Yeol, editor, Kim, Seungkeun, editor, and Kim, Jeong Ho, editor

Published
2023
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24. Path-Following Guidance Using Model Predictive Path Integral Control

Author

Jeong, Eui-Taek, Lee, Chang-Hun, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Lee, Sangchul, editor, Han, Cheolheui, editor, Choi, Jeong-Yeol, editor, Kim, Seungkeun, editor, and Kim, Jeong Ho, editor

Published
2023
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25. Pseudospectral Convex Optimization for Reentry Vehicle Guidance with No-Fly Zone Constraints

Author

Lee, Sang-Don, Lee, Chang-Hun, Kim, Sung-Yug, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Lee, Sangchul, editor, Han, Cheolheui, editor, Choi, Jeong-Yeol, editor, Kim, Seungkeun, editor, and Kim, Jeong Ho, editor

Published
2023
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27. Flavor mixing and renormalization in a perturbation theory

Author

Lee, Chang-Hun

Subjects
High Energy Physics - Phenomenology
Abstract

The renormalization of theories with flavor mixing is discussed, and it is shown that the physical unstable particles should be interpreted as quasiparticles which cannot be regarded as external states. Several popular beliefs on renormalization are disproved accordingly, and the limitations of physical renormalization schemes are discussed. In addition, the properties of unstable particles with flavor mixing such as decay widths are studied from scattering mediated by them., Comment: 40 pages, 5 figures

Published
2020

30. Generation of quasiparticles by particle-antiparticle mixing and limitations of quantum mechanics

Author

Lee, Chang-Hun

Subjects
High Energy Physics - Phenomenology
Abstract

The mixing of a neutral unstable particle and its antiparticle has been usually discussed in the framework of quantum mechanics in the literature. In this paper, the particle-antiparticle mixing is discussed fully in the quantum field theory, and it is shown that quantum mechanics is not the proper non-relativistic limit of the quantum field theory in the presence of such mixing. Moreover, it is also shown that a discrepancy indeed exists between the results from quantum mechanics and the quantum field theory, which can sometimes make big differences in theoretical predictions of observables such as decay widths. This result has an implication for the mixing of neutral mesons and the CP violation in their decays., Comment: 41 pages, 10 figures

Published
2020

40. Exploring the effect of justice, social capital, and power on supply chain disruption recovery : buyer-supplier dyadic perspectives

Author

Lee, Chang-Hun

Subjects
658.7, HD28 Management. Industrial Management
Abstract

A number of studies have brought understanding to supply chain disruption, but the recovery stage – what happens after a disruption event and how organisations can be successfully recovered – has received little attention. This thesis presents two studies that address this gap in the extant literature by incorporating theories that explain the cooperative relationship and influence mechanism in the buyer–supplier relationship. In the first study, by bridging research on justice and social capital theory, it is presumed that these two views can explain the strong relationship that facilitates parties’ interactions and the corresponding collective action effected to recover from the disruption. In the second study, the moderating role of the buyer’s intention to use mediated power (coercive and reward power) during the process of disruption response and recovery in the relationship between the buyer-supplier’s relational capital and their disruption response and recovery performance was investigated. To examine the dyadic nature of the supply chain and reduce the possibility of single rater bias, 239 matched pairs data were collected to adopt a buyers and supplier dyadic perspective. This was geared towards capturing the different perceptions of the relationship and its impact on the disruption response and recovery performance. The main contribution of this research is two-fold. First, this study is one of the first to examine the relationship between the impact of the justice perception on social capital accumulation, impact of accumulation of social capital on the firm’s disruption response and recovery performance as well as the moderating role of power on the link between relational capital and disruption recovery performance. The outcomes of this study allow for appropriate theoretical framing that can lead to understanding of this scantly previously investigated area. Second, having investigated the buyer–supplier’s dyadic relationship in the disruption recovery context, this has led to robust findings being delivered according to both parties’ individual viewpoints. More importantly, this has allowed for a dyadic perspective on the appropriate ways of dealing with such a situation to be uncovered.

Published
2020

42. Generation of quasiparticles by flavor mixing and CP violation: heavy Majorana neutrinos, part I

Author

Lee, Chang-Hun

Subjects
High Energy Physics - Phenomenology
Abstract

The phenomenology of flavor mixing of heavy Majorana neutrinos is studied. The physical degrees of freedom, which propagate like free particles until they decay in the presence of flavor mixing, are identified by diagonalizing the resummed propagator. It is shown that they should be interpreted as quasiparticles which lose Majorana nature., Comment: 38 pages, 9 figures

Published
2019

43. Trajectory-Based Anomaly Classification of 6-DOF Guided Missile Using Neural Networks

Author

Park, Su-Jeong, Oh, Yunseo, Kim, Sung Jun, Kim, Young-Won, Choi, Han-Lim, Lee, Chang-Hun, Kacprzyk, Janusz, Series Editor, Gomide, Fernando, Advisory Editor, Kaynak, Okyay, Advisory Editor, Liu, Derong, Advisory Editor, Pedrycz, Witold, Advisory Editor, Polycarpou, Marios M., Advisory Editor, Rudas, Imre J., Advisory Editor, Wang, Jun, Advisory Editor, Kim, Jinwhan, editor, Englot, Brendan, editor, Park, Hae-Won, editor, Choi, Han-Lim, editor, Myung, Hyun, editor, Kim, Junmo, editor, and Kim, Jong-Hwan, editor

Published
2022
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44. A New Biased Proportional Navigation Guidance for Decelerating Targets

Author

Kim, Boseok, Lee, Chang-Hun, Tahk, Min-Jea, He, Shaoming, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zhang, Junjie James, Series Editor, Yan, Liang, editor, and Yu, Xiang, editor

Published
2022
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