• 전기학회논문지
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• 제59권2호
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• pp.417-422
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• 2010

When memory devices are exposed to space environments, they suffer various effects such as SEU(Single Event Upset). Memory systems for space applications are generally equipped with error detection and correction(EDAC) logics against SEUs. In this paper, several error detection and correction codes - RS(10,8) code, (7,4) Hamming code and (16,8) code - are analyzed and compared with each other. Each code is implemented using VHDL and its performances(encoding/decoding speed, required memory size) are compared. Also the failure probability equation of each EDAC code is derived, and the probability value is analyzed for various occurrence rates of SEUs which the STSAT-3 possibly suffers. Finally, the EDAC algorithm for STSAT-3 is determined based on the comparison results.

• ETRI Journal
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• 제34권3호
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• pp.478-481
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• 2012

Testing memory and repairing faults have become increasingly important for improving yield. Redundancy analysis (RA) algorithms have been developed to repair memory faults. However, many RA algorithms have low analysis speeds and occupy memory space within automatic test equipment. A fast RA algorithm using simple calculations is proposed in this letter to minimize both the test and repair time. This analysis uses the grouped addresses in the faulty bitmap. Since the fault groups are independent of each other, the time needed to find solutions can be greatly reduced using these fault groups. Also, the proposed algorithm does not need to store searching trees, thereby minimizing the required memory space. Our experiments show that the proposed RA algorithm is very efficient in terms of speed and memory requirements.

• 정보처리학회논문지C
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• 제18C권2호
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• pp.89-96
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• 2011

Address Space Randomization(ASR)은 성능 부하가 없고 광범위한 데이터 메모리 영역의 보호가 가능한 우수한 방어 기법이다. ASR은 사용 가능한 데이터 메모리 영역 내에서 변수를 재배치 함으로써 공격자에게 변수의 주소를 숨기는데, 데이터 메모리 영역의 크기가 한정되어서 무차별 공격에 취약한 단점이 있다. 본 논문은 기존 ASR의 단점을 제거하기 위한 다중 ASR 기법을 제시한다. 다중 ASR 기법은 데이터 메모리 영역을 원본 및 복사 영역으로 나누고 각 메모리 영역의 변수 값을 비교함으로써 공격을 탐지하고 방어한다. 다중 ASR에서 각 데이터 메모리 영역의 변수는 서로 다른 순서로 배치되므로 한 번의 공격을 통해 동시에 동일한 변수 값을 조작하는 것은 불가능하다. 다중 ASR이 적용된 프로그램은 중복 수행으로 인해 비교적 높은 성능 부하를 보이나, 실제 공격 대상이 되는 웹서버 등 I/O 처리가 많이 요구되는 프로그램의 경우 40%~50% 정도의 성능 부하를 보인다. 아울러 본 논문에서는 프로그램에 다중 ASR을 적용하기 위한 변환프로그램을 개발하였다.

• Journal of Astronomy and Space Sciences
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• 제29권3호
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• pp.315-320
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• 2012

We developed a mass-memory chip by staking 1 Gbit double data rate 2 (DDR2) synchronous dynamic random access memory (SDRAM) memory core up to 4 Gbit storage for future satellite missions which require large storage for data collected during the mission execution. To investigate the resistance of the chip to the space radiation environment, we have performed heavy-ion-driven single event experiments using Heavy Ion Medical Accelerator in Chiba medium energy beam line. The radiation characteristics are presented for the DDR2 SDRAM (K4T1G164QE) fabricated in 56 nm technology. The statistical analyses and comparisons of the characteristics of chips fabricated with previous technologies are presented. The cross-section values for various single event categories were derived up to ~80 $MeVcm^2/mg$. Our comparison of the DDR2 SDRAM, which was fabricated in 56 nm technology node, with previous technologies, implies that the increased degree of integration causes the memory chip to become vulnerable to single-event functional interrupt, but resistant to single-event latch-up.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2001년도 춘계학술대회 발표논문집
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• pp.277-280
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• 2001

We proposed a novel fractal-space multiplexing holographic memory system using moving window and double-focusing lens, which can eliminate crosstalk due to two neighboring moving window rows in the vertical direction of the conventional moving window holographic memory system, and demonstrated its feasibility through optical experiments.

• 한국전자거래학회지
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• 제8권2호
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• pp.33-48
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• 2003

이동통신과 인터넷 기술의 결합으로 탄생한 무선 인터넷은 휴대의 편리성을 제공하고 있으나 모바일 환경의 제약사항 때문에 대중적인 인터넷 서비스로는 발전하지 못하고 있다. 무선 환경의 제한 요소 중 협소한 메모리 공간으로 모바일 디바이스에서는 효율적인 자원 관리를 수행하지 못하는 단점을 가지고 있다 휴대성이 고려되어야 하는 하드웨어 특성상 충분한 메모리 용량을 확보하는 데에는 한계가 있으므로 향후에는 디바이스 내부의 저장 장치에서 외부의 영역까지 메모리 공간을 확장하여 데이터 처리가 수행될 수 있는 플랫폼 구조로 발전되어야 할 것이다. 본 논문에서는 모바일 디바이스의 내부에서 외부의 서버까지 메모리 공간을 런타임 액세스(Run-time Access)에 의해서 확장하여 데이터 활용을 가능하게 하고 디바이스 내부의 파일을 효율적으로 관리할 수 있는 모바일 에이전트를 제안하며 이를 실현하기 위한 자원 관리시스템(RMS: Resources Management System)을 설계하고 구현하였다. 제안된 RMS를 적용한 디바이스는 '모바일 공간확장'으로 확대된 프로세스 적용이 가능하며 내부 파일을 효과적으로 관리하여 최적의 메모리 공간을 유지하는 효과가 있다.

• ETRI Journal
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• 제35권3호
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• pp.439-447
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• 2013

To increase device memory yield, many manufacturers use incorporated redundancy to replace faulty cells. In this redundancy technology, the implementation of an effective redundancy analysis (RA) algorithm is essential. Various RA algorithms have been developed to repair faults in memory. However, nearly all of these RA algorithms have low analysis speeds. The more densely compacted the memory is, the more testing and repair time is needed. Even if the analysis speed is very high, the RA algorithm would be useless if it did not have a normalized repair rate of 100%. In addition, when the number of added spares is increased in the memory, then the memory space that must be searched with the RA algorithms can exceed the memory space within the automatic test equipment. A very efficient RA algorithm using simple calculations is proposed in this work so as to minimize both the repair time and memory consumption. In addition, the proposed algorithm generates an optimal solution using a tree-based algorithm in each fault group. Our experiment results show that the proposed RA algorithm is very efficient in terms of speed and repair.

• Journal of information and communication convergence engineering
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• 제7권2호
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• pp.199-202
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• 2009

Adaptive memory management is a serious issue in data stream management. Data stream differ from the traditional stored relational model in several aspect such as the stream arrives online, high volume in size, skewed data distributions. Data skew is a common property of massive data streams. We propose the predicted allocation strategy, which uses predictive processing to cope with time varying data skew. This processing includes memory usage estimation and indexing with timestamp. Our experimental study shows that the predictive strategy reduces both required memory space and latency time for skewed data over varying time.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제7권1호
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• pp.7-14
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• 2003

The main concern of this paper is to develop a new class of quasi-newton methods. These methods are intended for use whenever memory space is a major concern and, hence, they are usually referred to as limited memory methods. The methods developed in this work are sensitive to the choice of the memory parameter ${\eta}$ that defines the amount of past information stored within the Hessian (or its inverse) approximation, at each iteration. The results of the numerical experiments made, compared to different choices of these parameters, indicate that these methods improve the performance of limited memory quasi-Newton methods.

• 전자공학회논문지B
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• 제28B권9호
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• pp.703-711
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• 1991

In this paper, an efficient storage reclamation algorithm for RISC parallel processing in the object orented programming environments is presented. The memory management for the dynamic memory allocation and the frequent memory access in object oriented programming is the main factor that decreases RISC parallel processing performance. The proposed algorithm can be efficiently allocated the memory space of RISCy computer which is required the frequent memory access, so it can be increased RISC parallel processing performance. The proposed algorithm is verified the efficiency by implementing C language on SUN SPARC(4.3 BSD UNIX).