• 전자공학회논문지
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• 제49권12호
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• pp.149-155
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• 2012

SSD(Solid State Disk)는 다수의 NAND 플래시 메모리로 구성되었으며 내부에 고성능 컨트롤러와 캐시 버퍼를 포함한 스토리지 장치이다. NAND 플래시 메모리는 제자리 덮어쓰기가 안되기 때문에 파일시스템에서 유효페이지가 갱신 및 삭제시 무효페이지로 전환되어 완전히 삭제하기 위해서는 가비지 컬렉션 과정을 거쳐야한다. 하지만 가비지 컬렉션은 지연시간이 긴 Erase 연산을 포함하기 때문에 SSD의 I/O 성능을 감소시키고 마모도를 증가시키는 문제가 된다. 본 논문에서는 입력데이터에 대하여 유효데이터와 무효데이터에서 중복검사를 실행하는 기법을 제안한다. 먼저 유효데이터에 대한 중복제거 과정을 거치고 그 다음에 무효데이터 재활용 과정을 거침으로써 중복률을 향상시켰다. 이를 통하여 SSD의 쓰기 횟수와 가비지 컬렉션 횟수를 감소시켜 마모도와 I/O 성능이 개선되었다. 실험결과 제안한 기법은 유효데이터 중복제거와 무효데이터 재활용을 둘다 하지 않는 일반적인 경우에 비해서 가비지 컬렉션 횟수가 최대 20% 감소하고 I/O 지연시간이 9% 감소하였다.

• 대한임베디드공학회논문지
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• 제11권2호
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• pp.125-134
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• 2016

NAND flash memory has unique characteristics like as 'out-place-update' and limited lifetime compared with traditional storage systems. According to out-of-place update scheme, a number of invalid (or called dead) pages can be generated. In this case, garbage collection is needed to reclaim invalid pages. Because garbage collection results in not only erase operations but also copy operations of valid (or called live) pages to other blocks, many garbage collection techniques have proposed to reduce the overhead and to increase the lifetime of NAND Flash systems. This techniques sometimes select victim blocks including cold data for the wear leveling. However, most of them overlook the cost of selecting victim blocks including cold data. In this paper, we propose a garbage collection technique named CAPi (Cost Age with Proportion of invalid pages). Considering the additional overhead of what to select victim blocks including cold data, CAPi improves the response time in garbage collection and increase the lifetime in memory systems. Additionally, the proposed scheme also improves the efficiency of garbage collection by separating cold data from hot data in valid pages. In experimental evaluation, we showed that CAPi yields up to, at maximum, 73% improvement in lifetime compared with existing garbage collections.

• Journal of Computing Science and Engineering
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• 제4권4호
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• pp.276-290
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• 2010

The join operator is fundamental in relational database systems. Evaluating join queries on large tables is challenging because records need to be efficiently matched based on a given key. In this work, we analyze join queries in SQL with large tables in which a foreign key may be null, invalid or valid, given a referential integrity constraint. We conduct an extensive join performance evaluation on three DBMSs. Specifically, we study join queries varying table sizes, row size and key probabilistic distribution, inserting null, invalid or valid foreign key values. We also benchmark three well-known query optimizations: view materialization, secondary index and join reordering. Our experiments show certain optimizations perform well across DBMSs, whereas other optimizations depend on the DBMS architecture.

• 인지과학
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• 제20권4호
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• pp.481-506
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• 2009

본 연구의 목적은 단서와 표적의 표상된 위치의 일치성이 주의기제의 작용에 중요한 역할을 하는지 회귀억제 연구방법을 이용하여 규명하는 것이었다. 실험 1에서는 청각단서와 시각표적을, 실험 2에서는 시각단서와 청각표적을 사용하였고, 단서와 표적이 제시되는 표상된 위치와 물리적 위치의 일치성에 따라 일치조건과 불일치조건으로 구분하였다. 실험결과, 실험 1에서 표상된 위치의 일치성에 따라 일치조건과 불일치조건을 구분하였을 경우 일치조건에서 반응촉진이 관찰되었다. 하지만 물리적 위치의 일치성에 따른 일치/불일치조건에서는 반응시간 차이가 관찰되지 않았다. 실험 2에서도 표상된 위치의 일치성에 따라 일치조건과 불일치조건을 구분하였을 경우 일치조건에서 반응촉진이 관찰되었으나 매우 제한적이었다. 이러한 실험결과는 단서와 표적의 표상된 위치의 일치성이 주의기제의 역할 중 반응촉진에 중요한 역할을 하며, 주의 연구에서 물리적 위치와 표상된 위치를 구분해야할 필요성을 시사한다.

• 한국CDE학회논문집
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• 제9권3호
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• pp.203-211
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• 2004

In this paper, we present a method of extracting a regular 2-manifold triangular net from a triangular net including degenerate and self-intersected triangles. This method can be applied to obtaining an offset model without degenerate and self-intersected triangles. Then this offset model can be used to generate CL curves and extract machining features for CAPP The robust and efficient algorithm to detect valid triangles by growing regions from an initial valid triangle is presented. The main advantage of the algorithm is that detection of valid triangles is performed only in valid regions and their adjacent selfintersections, and omitted in the rest regions (invalid regions). This advantage increases robustness of the algorithm. As well as a k-d tree bucketing method is used to detect self-intersections efficiently.

• 한국CDE학회논문집
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• 제11권1호
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• pp.20-26
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• 2006

This paper presents a procedure to compute pencil curves from a triangular mesh which is offset with the radius of a given ball-end mill. An offset triangular mesh has numerous self-intersections caused by an abundance of invalid triangles, which do not contribute to the valid CL-surface. Conceptually, we can obtain valid pencil curves by combining all intersections tying on the outer skin of the offset triangular mesh, i.e., the valid CL-surface. The underlying concept of the proposed algorithm is that visible intersections are always valid for pencil curves, because visible intersections lie on the outer skin of the offset model. To obtain the visibility of intersections efficiently, the proposed algorithm uses a graphics board, which performs hidden surface removal on up to a million polygons per second.

• 무역상무연구
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• 제22권
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• pp.137-171
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• 2004

Under Article 2 of the Uniform Customs and Practice for Documentary Credits (1993 Revision. UCP), letter of credit means an arrangement whereby an issuing bank is to make a payment to a beneficiary, or is to accept and pay bills of exchange drawn by the beneficiary, or authorises another bank to effect such payment, or to accept and pay such bills of exchange, or to negotiate, against stipulated document(s), provided that the terms and conditions of the letter of credit are complied with. In letter of credit operations, all parties concerned deal with documents, and not with goods, services and/or other performances to which the documents may relate (UCP, Article 4). It is important to note that under UCP, if a letter of credit contains conditions without stating the document(s) to be presented in compliance therewith, banks will deem such conditions as not stated and will disregard them (Article 13 c). Section 5-108(g) of the Uniform Commercial Code also contains a similar provision. However on several occasions the Korean Supreme Court held that non-documentary conditions in letter of credit governed by UCP could be regarded as valid, although they were not desirable in the context of letter of credit transactions. The rationale underlying the decisions was that parties to the letter of credit transactions are free to determine the terms and conditions of the relevant letter of credit. After reviewing the relevant provisions of UCP, UCC, the International Standby Practices (ISP98) and the Supreme Court decisions of Korea, the author suggests that we classify conditions that do not require any documents (so called apparent non-documentary conditions) into two categories and treat them differently. There are apparent non-documentary conditions that are consistent with the nature of letter of credit and those which are inconsistent with the nature of letter of credit. In the first category there are two sub-categories, (i) those which are valid and (ii) those which are invalid and thus should be disregarded. In the second category there are two sub-categories, (i) those which are invalid and thus should be disregarded and (ii) those which are valid but deprive the instrument of the nature as letter of credit.

• Journal of Multimedia Information System
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• 제8권1호
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• pp.23-30
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• 2021

Palmprint has become a popular biometric modality; however, palmprint recognition has not been conducted in video media. Video palmprint recognition (VPR) has some advantages that are absent in image palmprint recognition. In VPR, the registration and recognition can be automatically implemented without users' manual manipulation. A good-quality image can be selected from the video frames or generated from the fusion of multiple video frames. VPR in contactless mode overcomes several problems caused by contact mode; however, contactless mode, especially mobile mode, encounters with several revere challenges. Double-line-single-point (DLSP) assisted placement technique can overcome the challenges as well as effectively reduce the localization error and computation complexity. This paper modifies DLSP technique to reduce the invalid area in the frames. In addition, the valid frames, in which users place their hands correctly, are selected according to finger gap judgement, and then some key frames, which have good quality, are selected from the valid frames as the gallery samples that are matched with the query samples for authentication decision. The VPR algorithm is conducted on the system designed and developed on mobile device.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제4권1호
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• pp.1-4
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• 2015

본 논문에서는 주어진 채널이 변형될 때, 아미노산들의 유효한 사이드 체인 배치(side chain conformation)를 찾는 알고리즘을 제시한다. 제안된 알고리즘은 아미노산의 유연성에 근거하여 사이드 체인 유연성을 가진 단백질 분자를 구현하고, 채널 변화에 영향을 주는 인접 아미노산(adjacent amino acid)을 추출한다. 인접 아미노산과 이웃(neighbor) 아미노산의 충돌 검사를 수행하여 유효하지 않은 사이드 체인 배치를 제거한 후, 회전각 조합 트리(rotation angle combination Tree)를 구성하여 사이드 체인 배치 중 유효한 것들만을 추출한다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제8권1호
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• pp.17-24
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• 2002

본 논문에서는 이미지 인증을 목적으로 무효한 블록들을 격리하는 새로운 워터마킹 방법을 제안한다. 이 과정에서 워터마크의 비인식성과 깨지기 쉬운 워터마크를 보장하기 위하여 DCT 도메인의 고주파 영역을 사용하였다. 여러 가지 실험을 통하여 에러가 보정된 원본 영상들과 워터마크된 이미지들 사이에 유효한 블록들이 동일함을 확인하였다. 결과적으로 워터마크 추출 과정에서 원본 이미지나 워터마크와 같은 여분의 정보가 필요 없으며, 워터마크된 이미지만으로 2진 워터마크를 추출할 수 있다는 사실을 발견하였다. 실험 결과들은 제안된 방법이 이미지 인증을 위하여 성공적으로 사용될 수 있음을 보여준다.