NUMERICAL COMPARISON OF WENO TYPE SCHEMES TO THE SIMULATIONS OF THIN FILMS

MYUNGJOO KANG,CHANG HO KIM,YOUNGSOO HA 한국산업응용수학회 2012 Journal of the Korean Society for Industrial and A Vol.16 No.3

This paper is comparing numerical schemes for a differential equation with convection and fourth-order diffusion. Our model equation is ht + (h² - h³)x = -(h³hxxx)x, which arises in the context of thin film flow driven the competing effects of an induced surface tension gradient and gravity. These films arise in thin coating flows and are of great technical and scientific interest. Here we focus on the several numerical methods to apply the model equation and the comparison and analysis of the numerical results. The convection terms are treated with well known WENO methods and the diffusion term is treated implicitly. The diffusion and convection schemes are combined using a fractional step-splitting method.

Higher-order regularization based image restoration with automatic regularization parameter selection

Kang, Myeongmin,Jung, Miyoun,Kang, Myungjoo Elsevier 2018 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.76 No.1

<P><B>Abstract</B></P> <P>Poisson and multiplicative Rayleigh noises often appear in medical imaging such as X-ray images, positron emission tomography, and ultrasound images. In this study, we propose novel variational models for removing Poisson/multiplicative Rayleigh noise. We make use of hybrid higher-order total variation as the regularization terms of our proposed models to eliminate staircasing artifacts. We also adopt the spatially adaptive parameter technique to adequately smooth homogenous regions while preserving the edges. The spatially adaptive parameter selection is closely related to local constraints through a local expected value estimator. We provide a convergence analysis, including the existence and uniqueness of solution, and the first order optimality conditions. We apply the alternating direction method of multipliers for solving the proposed models. Numerical experiments demonstrate that our models exhibit a better performance than that of state-of-the-art models in terms of edge preservation, smoothness of the homogenous regions, and various quality measures.</P>

THE MATHEMATICAL MODELING AND NUMERICAL SIMULATIONS FOR THE MOTION OF SOAP BUBBLES

Myungjoo KANG 한국산업응용수학회 2006 한국산업응용수학회 학술대회 논문집 Vol.1 No.2

In this paper, we develop the appropriate equations for bubble motions depending on curvature using the level set methodology. Our method consists of an appropriate finite difference scheme for solving our model equations and a level set approach for capturing the complicated motion between the bubbles. Results indicate that our models and the level set methods can handle complicated interfacial motions and topology changes, and that they can numerically simulate many of the physical features of bubble motions.

Level Set Methods and Image Processing

Myungjoo Kang 한국산업응용수학회 2005 한국산업응용수학회 학술대회 논문집 Vol.- No.-

Using modern techniques from scientific computing and numerical analysis, natural phenomena or scientific experiment can be simulated effectively with a computer and used for computer graphics, for example as special effects for the film industry and manufacturing the thin film. The Level Set Methods can make those things happen without a lot of difficulties. This method was devised by Osher and Sethian(1988) to represent dynamically moving interfaces as the zero level set of a scalar function that evolves in time. Since then, many researchers have worked on many applications using a Level Set Methods. I will introduce the recent developments using the Level Set Methods which are including Fluid Simulation, Image Processing, Geometric Optics, Geospatial Data Compression.

Is OCIO superior in asset allocation performance?

( Myungjoo Kang ),( Inwook Song ),( Seiwan Kim ) 한국파생상품학회 2023 선물연구 Vol.31 No.2

This study aims to empirically analyze the asset allocation capabilities of Outsourced Chief Investment Officers (OCIOs) in Korea. The empirical analysis used data from 35 funds that were evaluated by the Ministry of Strategy and Finance from 2012 to 2020. The results of the analysis are summarized as follows. First, this study found that funds that adopted OCIO improved their asset allocation performance. Second, the sensitivity between risk-taking and performance decreased for funds that adopted OCIO. Third, it is found that OCIO adoption improves a fund’s asset management execution (tactical capabilities). This study has methodological limitations in which the methodology used in this study is not based on theoretical prior research, but on practical applications. However, considering the need to clearly analyze the capabilities of OCIO and the timeliness of the topic, this study is valuable and can provide meaningful information to funders who are considering adopting OCIO in the future.

Accelerated Bregman Method for Linearly Constrained $$\ell _1$$ – $$\ell _2$$ Minimization

Kang, Myeongmin,Yun, Sangwoon,Woo, Hyenkyun,Kang, Myungjoo Springer-Verlag 2013 Journal of scientific computing Vol.56 No.3

Analytic solution for American strangle options using Laplace–Carson transforms

Kang, Myungjoo,Jeon, Junkee,Han, Heejae,Lee, Somin Elsevier 2017 Communications in nonlinear science & numerical si Vol.47 No.-

<P><B>Abstract</B></P> <P>A strangle has been important strategy for options when the trader believes there will be a large movement in the underlying asset but are uncertain of which way the movement will be. In this paper, we derive analytic formula for the price of American strangle options. American strangle options can be mathematically formulated into the free boundary problems involving two early exercise boundaries. By using Laplace–Carson Transform(LCT), we can derive the nonlinear system of equations satisfied by the transformed value of two free boundaries. We then solve this nonlinear system using Newton’s method and finally get the free boundaries and option values using numerical Laplace inversion techniques. We also derive the Greeks for the American strangle options as well as the value of perpetual American strangle options. Furthermore, we present various graphs for the free boundaries and option values according to the change of parameters.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We derive analytic formula of Laplace–Carson transforms (LCT) for the price of American strangle options. </LI> <LI> By LCT, we can derive the nonlinear system of equations satisfied by the transformed value of two free boundaries of American strangle option. </LI> <LI> We then solve this nonlinear system using Newton’s method and finally get the free boundaries and option values using numerical Laplace inversion techniques. </LI> </UL> </P>

Image Colorization Based on a Generalization of the Low Dimensional Manifold Model

Kang, Myeongmin,Kang, Myungjoo,Jung, Miyoun Springer-Verlag 2018 Journal of scientific computing Vol.77 No.2

배달앱 기사는 왜 배달 노동에 머무는가? - Bourdieu의 자본이론을 중심으로 -

강명주(Kang, Myungjoo),김수영(Kim, Suyoung) 한국사회복지학회 2021 한국사회복지학 Vol.73 No.1

배달플랫폼의 발전에 따라, 교통사고로 인한 배달앱 기사의 부상과 사망, 불합리한 고용상태처럼 배달앱 노동을 둘러싼 심각한 사회문제들이 대두되는 상황이다. 그런데도 여전히 배달앱 기사가 배달앱 노동을 지속하는 이유는 무엇일까? 본 연구는 배달앱 기사가 배달앱 노동을 통해 실제 무엇을 얻고 무엇을 잃고 있는지를 살펴보고자 했다. 이를 위해 Bourdieu의 자본이론을 분석틀로 활용해, 총 13명의 배달앱 기사의 다차원적 자본의 획득과 상실 과정을 분석했다. 본문에서는 전반적인 자본이 부족했던 배달앱 기사들이 배달앱 노동을 통해 경제, 사회, 문화, 상징자본을 끌어올리고자 하지만, 시간이 지날수록 배달앱 노동의 장 안에서 획득했던 자본들을 상실 · 변형되는 과정을 추적했다. 또한, 배달앱 기사들이 상실한 자본을 다시 회복하기 위해 경제자본의 극대화에 초점을 맞춰 자본의 재생산을 시도하면서, 배달앱 기사들의 고유한 아비투스가 형성되는 상황을 드러냈다. 본 논문은 이러한 자본의 획득, 상실, 회복의 반복적 과정이 배달앱 기사의 생존방식이자, 현 배달앱 노동체계에서 벗어나지 못하는 궁극적 원인임을 밝힌다. 결론에서는 이를 토대로 배달앱 기사의 사회보장을 위한 대안을 논했다. With the recent development of delivery platforms, serious social problems surrounding delivery app labour are emerging, such as traffic accidents and poor working conditions. But many delivery app drivers are still willing to work on delivery apps. From the perspective of delivery app drivers" social space, this study intends to closely look at what they are getting and losing through delivery app labor. To this end, the authors conducted in-depth interviews with 13 delivery app drivers, using Bourdieu"s capital theory as an analytical framework to investigate how they acquire and lose multiple forms of capital in the field of delivery work. The delivery app drivers, who had lacked overall capital, pursued raising economic, social, cultural, and symbolic capital through delivery labor. But over time, they went through the process of losing and transforming the capitals acquired in the field of delivery labor. The delivery app drivers attempted to reproduce capitals by focusing on maximizing economic capital to restore their lost capitals, forming a unique habitus of delivery app drivers. This paper reveals that the iterative process of acquiring, losing, and recovering such capital is the survival mechanism of delivery app workers. This is also the fundamental cause which delivery workers continue to work on the current delivery app system. Based on these findings, the conclusion discusses alternatives for the social security of delivery app workers.

GRAYSCALE IMAGE COLORIZATION USING A CONVOLUTIONAL NEURAL NETWORK

MINJE JWA,MYUNGJOO KANG 한국산업응용수학회 2021 Journal of the Korean Society for Industrial and A Vol.25 No.2