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홀로그래픽 데이터 저장장치를 위한 저밀도 ON 픽셀 2차원 4-레벨 4/6 균형 변조부호
박근환(Keunhwan Park),이재진(Jaejin Lee) 대한전자공학회 2016 전자공학회논문지 Vol.53 No.11
홀로그래픽 데이터 저장장치 (HDSS)는 한 픽셀에 1비트 이상의 데이터를 저장 가능하며 전송 속도 및 저장 용량을 증가시키는 장점이 있다. 하지만 2차원적으로 생기는 인접 심볼 간의 간섭 (ISI) 및 페이지 간의 간섭 (IPI)이 발생한다. 본 논문에서는 홀로그래픽 데이터 저장장치에서 부호율이 1.33 bit/pixel이면서 코드워드의 밀도가 균일한 부호를 제안하였다. 제안된 저밀도 ON 픽셀 4/6 2차원 균형 변조부호는 기존의 2/3, 6/9 변조부호와 비교하여 비슷한 성능을 보이지만, 한 페이지에 기록되는 ON 픽셀의 비율을 낮춤으로써 체적 내에 페이지 수를 늘려 저장 용량을 증가시킬 뿐만 아니라 코드워드의 밀도가 균일하여 인접 페이지 간의 간섭을 줄일 수 있다. In the holographic data storage system, the data can be stored more than one bit per pixel and the storage capacity and transmission rate can be increased. In this paper, we proposed a sparse-ON pixel 4/6 balanced-modulation code that the code rate is 1.33 (bit/pixel) with uniform page density. Even though the performance of the proposed sparse-ON pixel 4/6 balanced-code is similar to 2/3 and 6/9 modulation codes, it can increase the storage capacity more than these modulation codes and also store more pages in a volume by reducing the rate of ON pixels to mitigate IPI (inter-page interference).
박근환(Keunhwan Park),손태호(Taeho Son),김원정(Wonjung Kim),김호영(Ho-Young Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Lungs are natural microfluidic devices that evolution has optimized to extract oxygen from air. In the bronchial tree, airways branch by dichotomy with a systematic reduction of their length and diameter. It is interesting that when we anatomically observe the human lungs, acinar airways diameter is reduced less steeply with progressive generations than the conducting airways. In conducting airways near the mouth, the reduction ratio is deduced by minimizing the total viscous dissipation, known as the Hess-Murray law. Noting that the acinar airways air drift velocity is smaller than the mean diffusion velocity, we construct a diffusion mass transfer model over a series of acinar airways, which allows us to predict the optimal airway reduction ratio that maximizes the oxygen transfer in a finite acinar airway volume. Our theoretical prediction is consistent with our experimental data obtained by using an artificial lung on a chip as well as the reported clinical data.
홀로그래픽 데이터 저장장치에서 2차원 심볼 간 간섭을 완화하기 위한 4-레벨 균형 변조부호
박근환(Keunhwan Park),이재진(Jaejin Lee) 대한전자공학회 2016 전자공학회논문지 Vol.53 No.9
홀로그래픽 데이터 저장 장치(HDSS)는 페이지 단위로 저장 매체의 체적에 데이터를 저장 및 판독하고 2차원으로 데이터를 처리하기 때문에 데이터 전송 속도 및 저장 용량이 증가한다. 게다가, 멀티레벨 HDSS는 한 픽셀에 한 비트이상을 저장할 수 있다. 하지만 2차원으로 페이지를 처리하므로 기존의 데이터 저장 시스템과 달리 2차원으로 인접한 심볼 간 간섭(ISI) 및 인접페이지 간 간섭(IPI)가 발생한다. 기존에 발표된 논문들은 멀티레벨 HDSS 환경에서 2차원 ISI 완화에 관한 연구에 초점을 두었지만 멀티레벨 HDSS 환경에서 2차원 ISI와 IPI를 동시에 완화하는 연구는 진행되지 않았다. 본 논문에서는 2차원 ISI 및 IPI를 동시에 완화하는 4-레벨 균형 변조부호를 제안하였다. In the holographic data storage system (HDSS), the data regarding the volume of a storage medium are recorded and read by the page, and the transmission rate and storage capacity can be increased because of two-dimensional, page-oriented data processing; furthermore, the multi-level HDSS can store more than one bit per pixel. For this same reason, however, and unlike conventional data-storage systems, the HDSS is hampered by two-dimensional (2D) intersymbol interference (ISI) and interpage interference (IPI). Progress regarding the published papers on 2D ISI, which is more severe in the multi-level HDSS, continues; however, mitigation of both 2D ISI and IPI in terms of the multi-level HDSS has not yet been studied. In this paper, we therefore propose a 4-level balanced-modulation code that simultaneously mitigates 2D ISI and IPI.
김태홍(Tae-Hong Kim),박근환(Keunhwan Park),김호영(Ho-Young Kim) 한국가시화정보학회 2011 한국가시화정보학회지 Vol.9 No.1
The bubble oscillations play an important role in ultrasonic cleaning processes. In the ultrasonic cleaning of semiconductor wafers, the cleaning process often damages micro/nano scale patterns while removing contaminant particles. However, the understanding of how patterns in semiconductor wafers are damaged during ultrasonic cleaning is far from complete yet. Here, we report the observations of the motion of bubbles that induce solid wall damage under 26 kHz continuous ultrasonic waves. We classified the motions into the four types, i.e. volume motion, shape motion, splitting or jetting motion and chaotic motion. Our experimental results show that bubble oscillations get unstable and nonlinear as the ultrasonic amplitude increases, which may exert a large stress on a solid surface raising the possibility of damaging microstructures.
이종진(Jongjin Lee),박근환(Keunhwan Park) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
This paper describes an experimental study on the cleaning of edge grinding tools using a dual-fluid nozzle. For cleaning with the dual-fluid nozzle, the dropletized ultra-pure water must be smaller than the particles. The dropletization is achieved through the pressure of nitrogen and ultrapure water. We have manufactured a dual-fluid nozzle. To demonstrate the droplet effect, the pressure of nitrogen and ultrapure water was set to 5 bar-5 bar. In this paper, cleaning forces by distance and the cleaning method is explained. The distance was set to 5mm and 10mm. We prove particle removal efficiency through a high-speed camera. The dual-fluid nozzle used 5.208 liters per minute of water. water. Existing nozzles used 7.11 liters per minute of water. This saves 26.75 percent of water. This means that cleaning with the dual-fluid nozzle is more useful.
이종진(Jongjin Lee),박근환(Keunhwan Park) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
This paper describes an experimental study on the cleaning of edge grinding tools using a dual-fluid nozzle. For cleaning with the dual-fluid nozzle, the dropletized ultra-pure water must be smaller than the particles. The dropletization is achieved through the pressure of nitrogen and ultrapure water. We have manufactured a dual-fluid nozzle. To demonstrate the droplet effect, the pressure of nitrogen and ultrapure water was set to 5 bar-5 bar. In this paper, cleaning forces by distance and the cleaning method is explained. The distance was set to 5mm and 10mm. We prove particle removal efficiency through a high-speed camera. The dual-fluid nozzle used 5.208 liters per minute of water. water. Existing nozzles used 7.11 liters per minute of water. This saves 26.75 percent of water. This means that cleaning with the dual-fluid nozzle is more useful.
이성섭(Seongseob Lee),박근환(Keunhwan Park) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
A rockwool is a porous medium composed of microscale pores and macroscale pores. We quantify the capillary rise height and the capillary rise weight in a rockwool. In wicking experiment in rockwool, we show that the early stages and the late stages. In early stage, weight and height scale follow t1/2. In late stage, weight and height scale follow t1/4. The reason why this occurs is that the effect of gravity depends on the height. this study is expected to be used as an important fundamental study for improving the performance by analyzing the hydrodynamic properties of the rockwool.