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122 results on '"Kim, Kimin"'

1. Stochastic fluctuation and transport of tokamak edge plasmas with the resonant magnetic perturbation field

Author

Choi, Minjun J., Kwon, Jae-Min, Kim, Juhyung, Rhee, Tongnyeol, Bak, Jun-Gyo, Shin, Giwook, Kim, Hyun-Seok, Jhang, Hogun, Kim, Kimin, Yun, Gunsu S., Kim, Minwoo, Kim, SangKyeun, Kaang, Helen H., Park, Jong-Kyu, Lee, Hyung Ho, In, Yongkyoon, Lee, Jaehyun, Kim, Minho, Park, Byoung-Ho, and Park, Hyeon K.

Subjects
Physics - Plasma Physics
Abstract

We present that a statistical method known as the Complexity-Entropy analysis is useful to characterize a state of plasma turbulence and flux in the resonant magnetic perturbation (RMP) edge localized mode (ELM) control experiment. The RMP ELM suppression phase with the stochastic pedestal top temperature fluctuation can be distinguished from the natural ELM free phase with the chaotic fluctuation. It is discussed that the stochastic temperature fluctuation localized near the pedestal top can be originated from the narrow layer of the field penetration near the pedestal top. The forced magnetic island can emit the resonant drift wave of comparable sizes (relatively low-k) in the RMP ELM suppression phase, and it can results in the generation of stochastic higher wavenumber fluctuations coupled to tangled fields around the island. The analysis of the ion saturation current measurement around the main outer striking point on the divertor shows that it also becomes more stochastic as the stronger plasma response to the RMP field is expected.

Published
2021
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2. Reliable detection and characterisation of dim target via track-before-detect

Author

Kim, Kimin, Mulgrew, Bernie, and Gishkori, Shahzad

Subjects
efficient algorithms, small aircraft detection, object-related parameters, detection algorithm, coherently integrating reflected signals, object trajectory estimation, micro-Doppler signature, maximum likelihood approach, drone frequency
Abstract

Detection of manoeuvring and small objects is a challenging task in radar surveillance applications. Small objects in high noise background induce low signal to noise ratio (SNR) reflections. Conventional methods detect such objects by integrating multiple reflections in the same range-bearing and doppler bins in sampled versions of received signals. When the objects manoeuvre, however, these methods are likely to fail to detect them because the integration is performed without taking into account the possibility of the object movements across resolution bins. Furthermore, slowly manoeuvring objects create detection difficulties in discriminating them from radar clutter. Reflections of such objects contain micro-Doppler shifts generated by their propulsion devices. These shifts can characterise specific types of objects. In this case, estimation of these shifts is a challenging task because the front-end signals at the receiver are low SNR reflections and are the superposition of all reflections from the entire object and the noise background. Conventional estimators for this purpose only use reflections collected in a coherent processing interval (CPI) and produce poor estimate outputs. In order to achieve the desired accuracy, one requires more reflections than those collected in a CPI. This thesis mainly considers the aforementioned two difficulties and aims to develop efficient algorithms, which can detect low SNR and manoeuvring objects by incorporating long-time pulse integration and micro-doppler estimation. Main contributions in this thesis are based on the following two algorithms. The first work considers the detection of manoeuvring and small objects with radars. The radar systems are considered both co-located and separated transmitter/receiver pairs, i.e., monostatic and bistatic configurations, respectively, as well as multistatic settings involving both types. The proposed detection algorithm is capable of coherently integrating reflected signals within a CPI in all these configurations and continuing integration for an arbitrarily long time across consecutive CPIs. This approach estimates the complex value of the reflection coefficients for the integration while simultaneously estimating the object trajectory. Compounded with this simultaneous tracking and reflection coefficient estimation is the estimation of the unknown time reference shift of the separated transmitters necessary for coherent processing. The detection is made by using the resulting integration value in a Neyman-Pearson test against a constant false alarm rate threshold. The second work focuses on micro-Doppler signature estimation of manoeuvring and small rotor based unmanned aerial vehicle (UAV) systems with a monostatic radar. The micro-Doppler signature is considered rotation frequencies generated by rotating rotor blades of the UAVs. This estimation uses a maximum likelihood (ML) approach that finds rotation frequencies to maximise a likelihood function conditioned on an object trajectory, complex reflection coefficients, and rotation frequencies. In particular, the proposed algorithm uses an expectation-maximisation (EM) approach such that the expectation of the likelihood mentioned above is approximated by using the state distributions generated from Bayesian recursive filtering for the trajectory estimation. The reflection coefficients and the rotation frequencies are estimated by maximising this approximated expectation. As a result, this algorithm is capable of simultaneously tracking the trajectory and estimating the reflection coefficients and the rotation frequencies of the UAVs before the decision on the object presence is made.

Published
2021
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3. Development of a Virtual Tokamak platform

Author

Kwon, Jae-Min, Choi, Hosaeng, Ki, JaeSeok, Park, Sang Yun, Park, Sang Hyeon, Kim, Young Jin, Cho, Hanju, Kim, Soojin, Chae, Hyun Sic, Lee, Kun-Su, Woo, Minho, Lee, Taegu, Lee, Dosub, Park, Jinseop, Tak, Taehyun, Rhee, Tongnyeol, Kim, Kimin, and Han, Hyunsun

Published
2022
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4. Detection via simultaneous trajectory estimation and long time integration

Author

Kim, Kimin, Uney, Murat, and Mulgrew, Bernard

Subjects
Computer Science - Systems and Control, Statistics - Applications
Abstract

In this work, we consider the detection of manoeuvring small objects with radars. Such objects induce low signal to noise ratio (SNR) reflections in the received signal. We consider both co-located and separated transmitter/receiver pairs, i.e., mono-static and bi-static configurations, respectively, as well as multi-static settings involving both types. We propose a detection approach which is capable of coherently integrating these reflections within a coherent processing interval (CPI) in all these configurations and continuing integration for an arbitrarily long time across consecutive CPIs. We estimate the complex value of the reflection coefficients for integration while simultaneously estimating the object trajectory. Compounded with this is the estimation of the unknown time reference shift of the separated transmitters necessary for coherent processing. Detection is made by using the resulting integration value in a Neyman-Pearson test against a constant false alarm rate threshold. We demonstrate the efficacy of our approach in a simulation example with a very low SNR object which cannot be detected with conventional techniques., Comment: submitted to the IEEE Transactions on Aerospace and Electronic Systems

Published
2017

5. Overview of recent progress in 3D field physics in KSTAR

Author

Park, Gunyoung, In, Yongkyoon, Park, Jong-Kyu, Ko, Won-Ha, Lee, Jaehyun, Kim, Minwoo, Shin, Giwook, Hahn, Sang-Hee, Kim, SangKyeun, Yang, Seong Moo, Hu, Qiming, Rhee, Tongnyeol, Choi, Minjun J., Kim, Kimin, Lee, Hyung-Ho, Jeon, Young-Mu, Kim, Woong-Chae, and Yoon, Siwoo

Published
2022
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8. Development of high-performance long-pulse discharge in KSTAR

Author

Kim, Hyun-Seok, primary, Jeon, YoungMu, additional, Han, Hyunsun, additional, Kim, Kimin, additional, Kim, Kwangpyo, additional, Kim, H.-S., additional, Rhee, Tongnyeol, additional, Kim, Juhyung, additional, Kim, Junghee, additional, Seo, Dongcheol, additional, Bang, Eunnam, additional, Ahn, Hee-Jae, additional, Ahn, Hyun-Sik, additional, Hong, Jaesic, additional, Jeong, J.H., additional, Kong, Jongdae, additional, Kwak, Jong Gu, additional, Jin, Jongkook, additional, Bak, J G, additional, Park, Kaprai, additional, Lee, Kyu-Dong, additional, Jung, Mi, additional, Kwag, Sang Woo, additional, Hahn, Sang-Hee, additional, Kim, SangKyeun, additional, Yoon, Si-Woo, additional, Wang, Sonjong, additional, Kim, Woong Chae, additional, and Kim, Young-Ok, additional

Published
2023
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13. A Dental Simulator for Training of Prevalent Interventions: Tooth Restoration and Ultrasonic Scaling

Author

Kim, Kimin, Cho, Jaehyun, Kim, Jaihyun, Park, Jinah, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Isokoski, Poika, editor, and Springare, Jukka, editor

Published
2012
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14. Stochastic fluctuation and transport of tokamak edge plasmas with the resonant magnetic perturbation field

Author

Choi, Minjun J., primary, Kwon, Jae-Min, additional, Kim, Juhyung, additional, Rhee, Tongnyeol, additional, Bak, Jun-Gyo, additional, Shin, Giwook, additional, Kim, Hyun-Seok, additional, Jhang, Hogun, additional, Kim, Kimin, additional, Yun, Gunsu S., additional, Kim, Minwoo, additional, Kim, SangKyeun, additional, Kaang, Helen H., additional, Park, Jong-Kyu, additional, Lee, Hyung Ho, additional, In, Yongkyoon, additional, Lee, Jaehyun, additional, Kim, Minho, additional, Park, Byoung-Ho, additional, and Park, Hyeon K., additional

Published
2022
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22. Quasi-randomization by survey date for policy analysis.

Author

Kim, Kimin and Lee, Myoung-Jae

Subjects
POLICY analysis, INCOME
Abstract

In annual surveys, the interview dates are scattered over several months. When a policy takes place during the survey period, quasi-randomized data may be obtained, if individuals interviewed before and after the policy timing are similar. The policy effect can be found with a before–after difference, which is 'Quasi-Randomization by Survey date (QRS)'. QRS may be viewed as an regression discontinuity (RD) with time as the running variable. When seasonality is present, the RD-style estimator fails, but we develop a difference-in-differences style estimator, which relies on a weaker assumption analogous to parallel trends that controls for sesonality. We provide an empirical example using Korea Labor and Income Panel Study data for a weekly work-hour reduction law in 2004 from 44 to 40 h. We find that the law effect is about 2 h reduction, not 4 h as the law stipulates. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Development of a Virtual Tokamak Platform

Author

Kwon, Jae-Min, primary, Choi, Hosaeng, additional, Ki, JaeSeok, additional, Park, Sang Yun, additional, Park, Sang Hyeon, additional, Kim, Young Jin, additional, Cho, Hanju, additional, Kim, Soojin, additional, Chae, Hyun Sic, additional, Lee, Kun-Su, additional, Woo, Minho, additional, Lee, Taegu, additional, Lee, Dosub, additional, Park, Jinseop, additional, Tak, Taehyun, additional, Rhee, Tongnyeol, additional, Kim, Kimin, additional, and Han, Hyunsun, additional

Published
2022
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34. Development of new computational methods for identifying segments and estimating the risk of water supply interruption for a segment in water pipe networks

Author

Kim KiMin and Park SuWan

Subjects
Pipeline transport, Petroleum engineering, Computer science, business.industry, 020209 energy, Computer software, 0202 electrical engineering, electronic engineering, information engineering, Water pipe, Water supply, Water treatment, 02 engineering and technology, business
Published
2017
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42. Anti-melanogenic effects of extracellular vesicles derived from plant leaves and stems in mouse melanoma cells and human healthy skin.

Author

Lee, Ruri, Ko, Hae Ju, Kim, Kimin, Sohn, Yehjoo, Min, Seo Yun, Kim, Jeong Ah, Na, Dokyun, and Yeon, Ju Hun

Subjects
EXTRACELLULAR vesicles, MELANINS, PLANT stems, MICROPHTHALMIA-associated transcription factor, PLANT cells & tissues, EPIDERMIS, MELANOMA, FOLIAGE plants
Abstract

Consumer interest in cosmetic industry products that produce whitening effects has increased demand for agents that decrease melanin production. Many such anti-melanogenic agents are associated with side effects, such as contact dermatitis and high toxicity, and also exhibit poor skin penetration. Considerable recent research has focused on plant-derived products as alternatives to chemotherapeutic agents that possess fewer side effects. In the current study, we investigated the anti-melanogenic effects of extracellular vesicles (EVs) extracted from leaves and stems of Dendropanax morbifera. Using spectrophotometric and biochemical approaches, we found that leaf-derived extracellular vesicles (LEVs) and stem-derived extracellular vesicles (SEVs) reduced melanin content and tyrosinase (TYR) activity in the B16BL6 mouse melanoma cell line in a concentration-dependent manner. An electron microscopy analysis further confirmed that LEVs and SEVs induce a concentration-dependent decrease in melanin content in melanoma cells. Both LEVs and SEVs exerted a greater whitening effect on melanoma cells than arbutin, used as a positive control, with LEVs producing the greater effect. Notably, neither LEVs nor SEVs induced significant cytotoxicity. We also examined the effects of plant-derived EVs on the expression of tyrosinase-related proteins (TRPs) in melanoma cells. LEVs inhibited expression of melanogenesis-related genes and proteins, including microphthalmia-associated transcription factor (MITF), TYR, TRP-1 and TRP-2. In a human epidermis model, LEVs exerted a stronger inhibitory effect on melanin production than arbutin. Collectively, our data suggest that LEVs from D. morbifera may be a novel candidate natural substance for use as an anti-melanogenic agent in cosmeceutical formulations. [ABSTRACT FROM AUTHOR]

Published
2020
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