재할당 블록을 이용한 플래시 메모리를 위한 효율적인 공간 관리 기법

권세진(Se-Jin Kwon),정태선(Tae-Sun Chung) 한국정보과학회 2007 정보과학회 컴퓨팅의 실제 논문지 Vol.13 No.7

플래시 메모리는 전원이 끊기더라도 정보를 유지할 수 있는 비 휘발성 메모리로써 빠른 접근속도, 저 전력 소비, 간편한 휴대성 등의 장점을 가진다. 플래시 메모리는 다른 메모리와 달리 “쓰기 전지우기”(erase before write) 성질과 제한된 수의 지우기 연산을 수행할 수 없는 성질을 지닌다. 이와 같은 하드웨어 특성들로 인해 소프트웨어인 플래시 변환 계층(FTL: flash translation layer)을 필요로 한다. FTL은 파일 시스템의 논리주소를 플래시 메모리의 물리주소로 바꾸어주는 소프트웨어로써 FTL의 알고리즘으로 인해 플래시 메모리의 성능, 마모도 등이 좌우된다. 이 논문에서는 새로운 FTL의 알고리즘인 EAST를 제안한다. EAST는 재할당 블록(reallocation block)을 이용한 효율적인 공간 관리 기법으로 로그 블록의 개수를 최적화 시키고, 블록 상태를 사용한 사상 기법을 사용하며, 플래시 메모리의 공간을 효율적으로 관리한다. EAST는 특히 플래시 메모리의 용량이 크고 사용하는 용량이 작을 경우 FAST보다 더 나은 성능을 보인다. Flash memory offers attractive features, such as non-volatile, shock resistance, fast access, and low power consumption for data storage. However, it has one main drawback of requiring an erase before updating the contents. Furthermore, flash memory can only be erased limited number of times. To overcome limitations, flash memory needs a software layer called flash translation layer (FTL). The basic function of FTL is to translate the logical address from the file system like file allocation table (FAT) to the physical address in flash memory. In this paper, a new FTL algorithm called an efficient and advanced space-management technique (EAST) is proposed. EAST improves the performance by optimizing the number of log blocks, by applying the state transition, and by using reallocation blocks. The results of experiments show that EAST outperforms FAST, which is an enhanced log block scheme, particularly when the usage of flash memory is not full.

사회주의 국가의 체제전환의 대한 재론

권세진 ( Kwon Se Jin ) 대한정치학회 2003 大韓政治學會報 Vol.11 No.1

모택동 시기의 정치,사회 분석 방법론 -Andrew G. Walder의 신전통주의(Neo-Traditionalism)를 중심으로-

권세진 ( Kwon Se Jin ) 영남중국어문학회 2003 중국어문학 Vol.0 No.42

本文把會試圖中國的在性出發來中國的政治和社會的 Walder的理論做檢討, 幷論此方法論的適用性. 首先, 在第二篇談毛澤東時期的主流觀点, 幷通過分析毛澤東時期的特征來談論那時期的特性. 在第三篇檢討Walder的新傳統主義方法論的方法論側面和理論. 在第四篇通過Brantly Womack對Walder的方法論的批判和Walder對此的辯論來分析中國社會. 最后在第五篇論述對改革開放后的中國社會的分析方法論中的新傳統主義槪念的可行性. Walder的新傳統注意方法論的方法論探索了與以前的全體主義視覺的硏究不同的內在的接法這一点上可謂是體現現實性前槪念. 但在타一個總括性的方法, 且沒有動員精巧性的變數上無法避免一般槪念的修辭學羅列和批判. 幷且, 卽使假設Walder的新傳統主義能구明確地分析中國的狀況, 但是如果不能說明其是否適應改革開放后的中國的變化過程的話, 就可以說明其有致命的弱点. 硏究中國政治社會分析方法論, 需利用把能구說明其內在的特殊性的曆史·傳統文化·社會主義制度 以及政治經濟基礎的總括的槪念. 在此觀点上Walder的新傳統主義的分析可以說是打開了一個新的開端.

CAD 모델 기반 비접촉 기상 측정에 관한 연구

권세진(Se Jin Kwon),이정근(Jeong Geon Lee),박정환(Jung Whan Park),고태조(Tae Jo Ko),김선호(Sun Ho Kim) Korean Society for Precision Engineering 2003 한국정밀공학회지 Vol.20 No.11

체적팽창효과를 고려한 예혼합화염과 와동의 상호작용에 관한 연구

정의헌,권세진,Chung, Eui-Heon,Kwon, Se-jin 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.12

A method is developed to include the effect of volume expansion in the description of the flame dynamics using G-equation. Line volume-source is used to represent the effect of the exothermic process of combustion with source strength assigned by the density difference between the burned and the unburned region. The present model provides good agreement with the experimental results. Including volume expansion, the flow field is adjusted to accommodate the increased volume flow rate which crossing the flame front and the result predicts the same behavior of measured velocity field qualitatively. The effect of increasing volume expansion does not change the initial growth rate of flame area but increase the residence time. Consequently this effect increases the maximum area of flame front. The flame propagation in varying flow field due to volume expansion provides a promising way to represent the wrinkled turbulent premixed flames in a numerically efficient manner.

형상 축소된 연소기의 열손실 및 소염해석 모델

이대훈,권세진,Lee, Dae-Hoon,Kwon, Se-Jin 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7

Down scaled combustor undergoes increased heat loss that results in incomplete combustion or quenching of the flame as a consequence. Therefore, effect of enhanced heat loss should be understood to design a MEMS scale combustion devices. Existing combustion models are inadequate for micro combustors because they were developed for analysis of regular scale combustor where heat loss can be ignored during the flame propagation. In this research a combustion model is proposed in order to estimate the heat loss and predict quenching limit of flame in a down scaled combustor. Heat loss in the burned region is expressed in a convective form as a product of wall surface area, heat transfer coefficient and temperature difference. Comparison to the measurements showed satisfactory agreement of the pressure and temperature drop. Quenching is accounted for by introducing a correlation of quenching parameter and heat loss. The present model predicted burnt fraction of gases with reasonable accuracy and proved to be applicable in thermal design of a micro combustor.

압력 변화 모사를 통한 초소형 연소기에서의 열손실 예측 모텔 개발

최권형,권세진,이대훈,Choi, Kwon-Hyoung,Kwon, Se-Jin,Lee, Dad-Hoon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.1

As the size of a combustor decreases to a MEMS scale, heat loss increases and becomes a dominant effect on the performance of the devices. Existing models, however, are not adequate to predict the heat transfer and combustion processes in such small scales. In the present study, a semi-empirical model to calculate heat loss from a micro combustor is described. The model derives heat transfer coefficients that best fits the heat loss characteristics of a micro combustor that is represented by transient pressure record after combustion is completed. From conservation of energy equation applied to the burned gas inside the combustor, a relationship between pressure and heat transfer is reduced. Two models for heat transfer coefficients were tested; a constant and first order polynomial of temperature with its coefficients determined from fitting with measurements. The model was tested on a problem of cooling process of burnt gas in a micro combustor and comparison with measurements showed good agreements. The heat transfer coefficients were used for combustion calculation in a micro vessel. The results showed the dependence of flame speed on the scale of the chamber through enhanced heat loss.

화학레이저 구동용 이젝터 시스템 개발 (I) - 화학레이저 구동용 초음속 이젝터 설계 변수 연구 -

김세훈,권세진,Kim, Se-Hoon,Kwon, Se-Jin 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.12

It is essential to operate chemical lasers with supersonic ejector system as the laser output power goes up. In this research, ejector design parameter study was carried out for optimal ejector design through understanding the ejector characteristics and design requirements for chemical lasers operating. Designed ejector was 3D annular type with 2$^{nd}$ -throat geometry and pressurized air was used for primary flow. Ejector design was carried out with two steps, quasi-1D gas dynamics was used for first design and commercial code was used to verify the first design. In this study, to get the effect of ejector geometry on its performance, three cases of primary nozzle area ratio and 2$^{nd}$ -throat cross sectional area and two cases of 2$^{nd}$ -throat L/D ratio experiments were carried out. Primary and secondary pressures were measured to get the mass flow rate ratio, minimum secondary pressure, ejector starting pressure and unstarting pressure at every case. In the result, better performance than design level was shown and optimal ejector design method for chemical lasers was obtained.

초소형 연소기내 화염전파의 수치모사

최권형,이대훈,권세진,Choi, Kwon-Hyoung,Lee, Dae-Hoon,Kwon, Se-Jin 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.6

A numerical simulation of flame propagation in a micro combustor was carried out. Combustor has a sub -millimeter depth cylindrical internal volume and axisymmetric one-dimensional was used to simplify the geometry. Semi-empirical heat transfer model was used to account for the heat loss to the walls during the flame propagation. A detailed chemical kinetics model of $H_2/Air$ with 10 species and 16 reaction steps was used to calculate the combustion. An operator-splitting PISO scheme that is non-iterative, time-dependent, and implicit was used to solve the system of transport equations. The computation was validated for adiabatic flame propagation and showed good agreement with existing results of adiabatic flame propagation. A full simulation including the heat loss model was carried out and results were compared with measurements made at corresponding test conditions. The heat loss that adds its significance at smaller value of combust or height obviously affected the flame propagation speed as final temperature of the burnt gas inside the combustor. Also, the distribution of gas properties such as temperature and species concentration showed wide variation inside the combustor, which affected the evaluation of total work available of the gases.

플래시 메모리의 데이터 신뢰성 향상 및 수명 연장을 위한 하이브리드 메모리기반의 FTL알고리즘 제안

이하림 ( Harim Lee ),권세진 ( Se Jin Kwon ),김성수 ( Sungsoo Kim ),정태선 ( Tae Sun Chung ) 한국정보처리학회 2014 한국정보처리학회 학술대회논문집 Vol.21 No.2

최근 낸드 플래시 메모리는 임베디드 저장 장치로 많이 사용되고 있다. 비휘발성인 플래시 메모리는 기존의 하드디스크와 달리 저 전력,좋은 내충격성 및 집적도 둥 많은 장점이 있지만 데이터 업데이트시 덮어쓰기가 안 되어 쓰기 연산 전 해당 블록을 지우는 작업이 선 진행되어야 하며 이로 인해 부분 페이지 업데이트가 자주 일어난다. 이런 플래시메모리와 더불어 최근 차세대 메모리연구가 많이 진행 중인데,이 중에서 PCM 이라는 메모리는 비휘발성으로 정전시 데이터가 날라 가버리는 DRAM에 반해 전원이 공급 안 되더라도 데이터가 보존되는 특성이 있다. 하지만 PCM 역시 플래시 메모리와 마찬 가지로 블록 당 쓰기연산 작업이 제한되어 있어서 근래에 DRAM과 같이 사용하는 하이브리드 구조를 채택하여 많은 연구가 진행되고 있다. 따라서 본 논문에서는 플래시 메모리의 문제점을 해결함으로서 수명을 연장시키고 정 전시 데이터가 보존되지 않는 DRAM의 단점을 하이브리드 메모리를 기반으로 하여 데이터의 신뢰성을 높이는 FTL알고리즘을 제안한다.