• 정보보호학회논문지
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• 제23권5호
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• pp.931-938
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• 2013

디스크 암호화 소프트웨어로 데이터를 암호화 하는 경우 패스워드를 획득하기 전까지 암호화 데이터의 원본 데이터를 추출하기 위해서는 많은 어려움이 있다. 이러한 디스크 암호화 소프트웨어의 암호화 키는 물리 메모리 분석을 이용하여 암호화 키를 추출할 수 있다. 물리 메모리에서 암호화 키 탐색을 수행하는 경우 일반적으로 메모리 전체를 대상으로 탐색을 수행하기 때문에 메모리 크기에 비례하여 많은 시간이 요구된다. 하지만 물리 메모리 데이터에는 시스템 커널 오브젝트, 파일 데이터와 같이 암호화 키와 관련이 없는 많은 데이터가 포함되어 있음으로, 이를 분석하여 키 탐색에 필요한 유효한 데이터를 추출하는 방법이 요구된다. 본 논문에서는 윈도우즈 커널 가상 주소 공간 분석을 통해 물리 메모리에서 디스크 암호화 키가 저장되는 메모리 영역만 수집하는 효율적인 방법을 제시하고자 한다. 실험을 통해 제안된 방법이 기존 방법보다 암호화 키 탐색 공간을 효율적으로 줄임으로써 우수함을 증명한다.

• 한국인터넷방송통신학회논문지
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• 제21권6호
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• pp.65-70
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• 2021

최근 모바일 앱의 수가 급증하면서 스마트폰의 메모리 크기 또한 크게 증가하고 있다. 메모리 매체인 DRAM은 모든 셀이 지속적인 전원재공급 연산을 수행해야 내용이 유지되는 휘발성 매체로 메모리 크기 증가 시 전력 소모도 그에 비례해 늘어난다. 최근 스마트폰의 메모리로 DRAM이 아닌 저전력의 비휘발성 메모리를 사용하여 배터리 소모를 줄이고자 하는 시도가 늘고 있다. 그러나, 비휘발성 메모리는 쓰기 연산에 취약성을 가지고 있어 이를 해결하기 위한 분석이 필요하다. 본 논문은 모바일 앱의 메모리 쓰기 참조 트레이스를 추출하고 그 특성을 다양한 각도에서 분석하였다. 본 논문의 연구 결과는 비휘발성 메모리가 메인 메모리로 채택되는 미래의 스마트폰 시스템에서 쓰기 효율성을 가진 메모리 관리 기법 설계에 널리 활용될 수 있을 것으로 기대된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.687-691
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• 2001

Al alloy matrix composite with TiNi shape memory fiber as reinforcement has been fabricated by hot pressing to investigate mechanical properties. The stress-strain behavior of the composites was evaluated at temperatures between 363K and room temperature as a function of pre-strain by using experimental and finite element analysis, and both cases showed that the tensile stress at 363K was higher than that of the room temperature. Especially, the tensile stress of this composite increases with increasing the amount of pre-strain, and it also depends on the volume fraction of fiber and heat treatment. The smartness of the composite is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being pre-strained.

• 대한기계학회논문집A
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• 제32권12호
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• pp.1153-1160
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• 2008

In this paper, the algorithm of Abaqus UMAT is introduced to analyze the shape memory alloy. The SMA has two main effects which show non-linearity. Due to this, it is hard to analyze SMA using analysis tools and to describe all of two effects. Therefore, in this study, the program using Abaqus UMAT based on Modified Brinson model is used to analyze SMA. The martensite fraction, the most important factor which defines SMA motion, is also calculated by Fortran program in UMAT. In addition, the tensile test of SMA specimen is conducted. The availability of algorithm is proved by comparing analysis to experimental result.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.257-258
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• 1998

To reveal the interconnected brain regions involved in human working memory, their functional connectivity was analyzed using principal component analysis (PCA). rCBF PET scans were peformed on 5 normal volunteers during the verbal and visual working memory tasks and PCA was applied. PCA produced the first principal components related with the increase of the difficulty and the second one which demonstrate the dissociation of verbal and visual memory system.

• 정신신체의학
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• 제6권2호
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• pp.136-146
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• 1998

Objectives : This study was performed to evaluate the effects of PTSD on memory function, to investigate the difference of memory function between PTSD and non-PTSD patients, and to identify major variables correlated to PTSD scale and Memory Assessment Scale. Methods: The authors used PTSD-scale(Mississippi scale and Combat Exposure Scale) for measuring PTSD severity. And, Beck Depression Inventory was also used. Memory assessment scale was assessed by well trained psychologist. Thirty one Vietnam veterans who had been hospitalized were collected consecutively. These patients were evaluated by psychiatrists with interview and measurement for fifteen months since March, 1997. The collected data were analyzed by SPSS and the stastistic methods used for analysis Chi-square, t-test, and Pearson's correlation. Results : 1) There were significant differences in short-term memory and verbal memory between PTSD and non-PTSD in Vietnam veterans. 2) Mississippi scale and Combat Exposure Scale were negatively correlated to short-term memory and verbal memory(Pearson's correlation). 3) Religion status was a significant variable between PTSD and non-PTSD in Vietnam veterans. 4) There is no significant difference in visual memory and total memory scale between PTSD and Non-PTSD in Vietnam veterans Conclusions : Neuropsychological changes were found in the posttraumatic stress disorder. There were significant differences in short-term memory and verbal memory between PTSD and non-PTSD in Vietnam veterans. Mississippi scale and Combat Exposure Scale were negatively correlated to short-term memory and verbal memory. We suggest that neuropsychological test might be used for an objective assessment of patients with the combat related PTSD and be considered helpful in the assessment of patients with the diagnosis. And we also suggest rehabilitation strategies would be used to compensate for memory deficits in PTSD patients.

• 인터넷정보학회논문지
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• 제17권4호
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• pp.1-9
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• 2016

Algorithms implementing distributed shared memory (DSM) were developed for ensuring consistency. The performance of DSM algorithms is dependent on system and usage parameters. However, ensuring these algorithms to tolerate faults is a problem that needs to be researched. In this study, we proposed fault-tolerant scheme for DSM system and analyzed reliability and fault-tolerant overhead. Using our analysis, we can choose a proper algorithm for DSM on error prone environment.

• 전기의세계
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• 제21권4호
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• pp.39-44
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• 1972

This paper describes a new approach for minimizing working memory spaces without loosing too much amount of computing time in the analysis of power system faults. This approach requires the decomposition of alrge power system into several small groups of subsystems, forms individual bus impedance matrics, store them in the auxiliary memory, later assembles them to the original total system by algorithms. And also the approach uses techniques for diagonalizing primitive impedances and expanding the system bus impedance matrices by adding a fault bus. These scheme ensures a remarkable savings of working storage and continous computations of fault currents and voltages with the voried fault locations.

• Journal of Computing Science and Engineering
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• 제8권3호
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• pp.157-172
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• 2014

Contemporary embedded systems often use NAND flash memory instead of hard disks as their swap space of virtual memory. Since the read/write characteristics of NAND flash memory are very different from those of hard disks, an efficient page replacement algorithm is needed for this environment. Our analysis shows that temporal locality is dominant in virtual memory references but that is not the case for write references, when the read and write references are monitored separately. Based on this observation, we present a new page replacement algorithm that uses different strategies for read and write operations in predicting the re-reference likelihood of pages. For read operations, only temporal locality is used; but for write operations, both write frequency and temporal locality are used. The algorithm logically partitions the memory space into read and write areas to keep track of their reference patterns precisely, and then dynamically adjusts their size based on their reference patterns and I/O costs. Without requiring any external parameter to tune, the proposed algorithm outperforms CLOCK, CAR, and CFLRU by 20%-66%. It also supports optimized implementations for virtual memory systems.

• 대한전자공학회논문지SD
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• 제46권12호
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• pp.73-79
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• 2009

최근 VLSI 회로 직접도가 급속도로 증가함에 따라 하나의 시스템 칩에 고밀도와 고용량의 내장 메모리(Embedded Memory)가 구현되고 있다. 고장난 메모리를 여분 메모리(Spare Memory)로 재배치함으로써 메모리 수율 향상과 사용자에게 메모리를 투명하게 사용할 수 있도록 제공할 수 있다. 본 논문에서는 고장난 메모리 부분을 여분 메모리의 행과 열 메모리 사용으로 고장난 메모리를 고장이 없는 메모리처럼 사용할 수 있도록 여분 메모리 재배치 알고리즘인 MRI를 제안하고자 한다.