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Twin-Image Elimination in an In-Line Digital Holographic Microscope
Hyungjun Cho,Younghun Yu,Doocheol Kim,Jung-Young Son,Sanghoon Shin,Wongun Jang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4
A novel method is employed to eliminate the twin images in the so-called ``in-line" digital holographic microscope. We could develop a digital holographic microscope that can solve the problems of overlapping of real and imaginary images and eliminate one of them by padding and removing the DC term by using an averaging method. The entire process requires only one digital hologram. A novel method is employed to eliminate the twin images in the so-called ``in-line" digital holographic microscope. We could develop a digital holographic microscope that can solve the problems of overlapping of real and imaginary images and eliminate one of them by padding and removing the DC term by using an averaging method. The entire process requires only one digital hologram.
A study on the Force of interaction potential between a Single microparticle and an evanescent Field
HyungJun Cho,YoungHun Yu,Chikyu Choi,DooCheol Kim 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
Forces acting on a single dielectric micro particle within an Evanescent Field have been analyzed by means of a potential measurement system. We show that the radiation pressure strongly depends on the incident laser power and the relative distance between interface and particles. If the relative distance is more than 1 m, the radiation pressure does not depending on the laser power.
SVR을 이용한 가상머신 자원 이용률 예측 기법의 성능 분석
김형준(HyungJun Kim),김세진(SeJin Kim),길준민(JoonMin Gil),정광식(KwangSik Chung),유헌창(HeonChang Yu) 한국정보과학회 2021 한국정보과학회 학술발표논문집 Vol.2021 No.6
최적의 자원 이용률로 데이터센터를 운영하기 위해서는 가상 머신 이주를 통한 동적 자원 관리가 필수적이다. 가상 머신 이주의 사전 예방적(proactive) 방법에서 가상 머신 이주 시점을 결정하기 위해서는 가상 머신과 호스트의 자원 이용률 예측 작업이 수행되어야 하는데, 이 때 시계열 분석 기법이 활용된다. 본 논문에서는 가상 머신 자원 이용률 예측 작업을 수행하기 위한 시계열 분석 기법 중 SVR의 성능 분석을 진행하였으며, ARIMA를 비교하여 기준 모델(baseline model)로 선택하였다. 실험은 다양한 데이터 크기, 자원유형 및 매개변수 설정 하에서 이루어졌으며, 예측 정확도, 강건함(robustness), 학습부터 추론까지의 소요 시간에 초점을 맞춰 각 기법에 대한 성능 분석을 진행하였다.
유지용(Jiyong Yu),김세준(Sejun Kim),이준용(Junyong Lee),정민영(Minyoung Jung),김형준(Hyungjun Kim),김광연(Gwangyoen Kim) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
ISG (Idle Stop & Go) system for Automatic-transmission equipped vehicle is developed for fuel saving consumed during idle stop. For this purpose, we made three kinds of system suit for the vehicle’s market positioning. One, called semiautomatic version, for small & TAXI vehicle and it operates when the driver changed the shift lever from D to Neutral. The second version, called automatic version, for conventional vehicle and it operates without any shift lever operation. The third one is Belt-Driven system and it developed only for Luxury class vehicle because of its NVH characteristic and higher cost. For these one, we developed our own Software and test procedure. And as a result, we can get more than 6%~30% of fuel economy improvement and eco-friendly brand image.
The Tip-Tilt Correction System in AO System for Small Telescope
유형준,박용선,이방원,Yu, Hyungjun,Park, Yong-Sun,Lee, Bangweon 한국천문학회 2012 天文學會報 Vol.37 No.2
We are developing Adaptive Optics (AO) system for 24 inch telescope at Seoul National University Observatory. It consists of the tip-tilt correction system and the residual wavefront error correction system with a deformable mirror and a wavefront sensor. We present the construction and performance measurements of the tip-tilt correction system. The tip-tilt component is the single largest contributor to wavefront error, especially for small telescope. The tip-tilt correction system consists of a quadrant photodiode, a tip-tilt mirror and a feed back loop. The collimated He-Ne laser beam is used for input light source and is artificially disturbed by air turbulence generated by a heat gun. Most of the turbulence is of low frequency less than 20 Hz, but extends to a few hundreds Hz. It is found that the closed loop system using proportional-integral-derivative (PID) control successfully corrects tip-tilt error at a rate as high as 300~400 Hz.
강동길(Donggil Kang),YU WENXING(WenXing Yu),조형준(HyungJun Cho) 한국자료분석학회 2023 Journal of the Korean Data Analysis Society Vol.25 No.3
의사결정나무는 분류 규칙을 기반으로 데이터를 재귀적으로 분할하여 예측을 수행하는 데이터 마이닝 방법론 중 하나이다. 나무 구조를 통해 분석 결과를 이해할 수 있어 예측력뿐만 아니라 높은 해석력을 동시에 갖는 장점이 있다. 또한 반응변수와 설명변수 간 비선형 상관관계에도 사용이 가능한 장점 때문에 많은 분야에서 활용되고 있다. 하지만 예측 목적이 반응변수의 최빈값인 경우, 기존에 제안된 의사결정나무를 적용할 수 없다는 한계가 있다. 본 연구는 커널 밀도 추정 방법을 의사결정나무 모형에 접목하여 새로운 형태의 최빈값 의사결정나무(modal decision tree) 모형을 정의한다. 모의실험은 4가지 모형으로 진행하였으며 설명변수와 반응변수가 선형 및 비선형 상관관계일 때, 데이터의 크기별로 결과를 비교하였다. 모의실험 결과를 통해 데이터가 선형 상관관계인 경우, 본 논문에서 제안하는 최빈값 의사결정나무 모형과 기존에 제안된 최빈값 선형 회귀(modal linear regression: MODLR)모형과 성능이 비슷하게 보이는 반면 데이터가 비선형 상관관계인 경우, 본 논문에서 제안하는 최빈값 의사결정나무 모형 성능이 더 우수함을 보인다. Decision trees are one of the data mining techniques that make predictions by recursively partitioning data structures based on split rules. Since the analysis results can be understood through the tree structure, it has the advantage of having high interpretation power as well as predictive power. In addition, it is used in many fields because it is able to identify nonlinear relationships between response and predictor variables. However, if the purpose of it is to predict the mode of the response variable, there is a limitation in that the previously proposed decision tree cannot be applied. Thus, we develop a new form of the modal decision tree model by integrating the kernel density estimation methods into the decision tree model. The simulation is conducted with four models. The results are compared for each size of the data when the predictor variable and the response variable are linear and nonlinear relationship cases. When the data has a linear relationship, the performance of the modal desicion tree model proposed in this paper is comparative to that of the previously proposed modal linear regression (MODLR) model. When the data has a nonlinear relationship, the performance of the modal tree model is better.