• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2004년도 추계 종합학술대회 논문집
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• pp.448-452
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• 2004

부분키를 사용한 캐쉬 인식 $B^+$ 트리는 키 압축과 포인터 압축 방법을 동시에 적용한 캐쉬 인식 트리이다. 기존의 캐쉬 인식 트리들은 키 압축과 포인터 압축을 따로 고려하였다. 이에 반해 부분키를 사용한 캐쉬 인식 $B^+$ 트리는 키와 포인터를 동시에 압축하여 캐쉬 활용도를 높였다. 본 논문은 기 발표된 부분키를 사용한 캐쉬 인식 $B^+$ 트리의 벌크로드와 검색 알고리즘을 구현하여 성능 평가를 수행하였다. 그리고 $B^+$-트리와 Simple Prefix $B^+$-트리의 성능비교를 통하여 부분키 캐쉬 인식 $B^+$ 트리의 성능의 우수함을 확인 하였다.

• International Journal of Contents
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• 제11권4호
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• pp.56-69
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• 2015

This paper proposes an efficient image encryption scheme based on quintuple encryption using two chaotic maps. The encryption process is realized with quintuple encryption by calling the encrypt(E) and decrypt(D) functions five times with five different keys in the form EDEEE. The decryption process is accomplished in the reverse direction by invoking the encrypt and decrypt functions in the form DDDED. The keys for the quintuple encryption/decryption processes are generated by using a Tent map. The chaotic values for the encrypt/decrypt operations are generated by using a Gumowski-Mira map. The encrypt function E is composed of three stages: permutation, pixel value rotation and diffusion. The permutation stage scrambles all the rows and columns to chaotically generated positions. This stage reduces the correlation radically among the neighboring pixels. The pixel value rotation stage circularly rotates all the pixels either left or right, and the amount of rotation is based on chaotic values. The last stage performs the diffusion four times by scanning the image in four different directions: Horizontally, Vertically, Principal diagonally and Secondary diagonally. Each of the four diffusion steps performs the diffusion in two directions (forward and backward) with two previously diffused pixels and two chaotic values. This stage ensures the resistance against the differential attacks. The security and performance of the proposed method is investigated thoroughly by using key space, statistical, differential, entropy and performance analysis. The experimental results confirm that the proposed scheme is computationally fast with security intact.

• 한국인터넷방송통신학회논문지
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• 제13권6호
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• pp.137-145
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• 2013

최근 대부분의 모바일 단말기는 LCD 터치 화면에 소프트 키보드를 장착한다. 그러나 소프트 키보드의 터치화면의 크기가 작기 때문에, 인접키가 실수로 눌러지고, 한 키를 여러 키 입력에 중복 사용함에 따라 사용자의 키 입력 오류가 많이 발생한다. 본 논문에서는 사용자가 텍스트를 입력하는 동안 적절한 어휘를 추천하여 키 입력 오류를 쉽게 수정하도록 돕는 알고리즘을 제안하고 MissLess 소프트 키보드를 구현한 내용에 대해 기술한다. 3개의 간단한 테스트 셋을 작성하여 MissLess 키보드의 추천 성능을 평가한 결과 다소 차이가 있지만 90%에 달하는 추천 성능을 얻었다. 그러나 추천 워드가 4개인 것을 고려하면 추천 성능을 해석할 필요가 있다.

• 한국환경과학회지
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• 제7권3호
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• pp.251-262
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• 1998

A number of illustrated floras are generally used when we want to idenufy a name of a certain tree. This method, however, has not been efficient because it has taken a great deal of time and effort for persons who do not have much knowledge on the group of the plant. In contrast to this method, the use of taxonomical keys is very efficient for finding out the group of a certain plant. But this method Is very dirtficult for non-specialists to understand the taxonomical ternunology and thus has not been of general use. In thins context, this study was conducted to present the efficient way of the group of a certain tree through the computer database by using the brief forms of plant organs. The database consists of effect fields such as form of trunk and evergreen or deciduous, types of leaf and leaf arrangement, existence of price and hair on twig, form of leaf margin, leaf form and venation, existence of hair on leaf surface and petiole, length of leaf and petiole. The 222 species of tree used for landscape architecture were sorted by items of the eight fields. As a result, the 222 species were divided into 185 groups and the one group contains 7species, 2 groups contain 3 species, 27 groups contain 2 species and 155 groups contain only one species. Therefore it is suggested that the use of computer database and illustrated floras is very easy and efficient in identifying a tree.

• 한국과학교육학회지
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• 제9권1호
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• pp.69-74
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• 1989

For the advancement of research in biological education in Korea, research trends shown in Journal of Biological Education(JBE)of England were analyzed by using a PC program(REFMENU). Papers Published in JBE between 1977 and 1987 were registered on the program with classifying keys of biological education and biology including names of authors, year, title, volume pages, and key words. Those input-date were analyzed by sorting depend-ing on either the classifying keys or the key words. Among the 361 papers 28.8% was dealing with the theory of science education. The rest dealt with biology and biological education, together. Of the six categories of biological education, the research on biological curriculum was 41 % of total and was the most. The major trends in this category was in developing the content of the curriculum. In the research of biological instruction, 37 papers dealt with the instruction theory and the rest 60 papers dealt with the tactics of Instruction. Of the 60 papers on materials in biological education, the research in developing the biological material was the most. Thus, the general research trend was far more practical aspect than the theoretical aspect of biological education. In the analysis of the papers depending on the biological categories, the one dealt with ecology was the most(26.8%). The rest papers showed almost even distribution in the 13 categories of biology. The results of this analysis was discussed by comparing with the research trends in Korea to suggest the possible future studies.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.5100-5119
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• 2018

Most of existing privacy-preserving multi-authorities attribute-based encryption schemes (PP-MA-ABE) only considers the privacy of the user identity (ID). However, in many occasions information leakage is caused by the disclosing of his/her some sensitive attributes. In this paper, we propose a collusion-resisting ciphertext-policy PP-MA-ABE (CRPP-MACP-ABE) scheme with hiding both user's ID and attributes in the cloud storage system. We present a method to depict anonymous users and introduce a managerial role denoted by IDM for the management of user's anonymous identity certificate ($AID_{Cred}$). The scheme uses $AID_{Cred}$ to realize privacy-preserving of the user, namely, by verifying which attribute authorities (AAs) obtain the blinded public attribute keys, pseudonyms involved in the $AID_{Cred}$ and then distributes corresponding private keys for the user. We use different pseudonyms of the user to resist the collusion attack launched by viciousAAs. In addition, we utilize IDM to cooperate with multiple authorities in producing consistent private key for the user to avoid the collusion attack launched by vicious users. The proposed CRPP-MACP-ABE scheme is proved secure. Some computation and communication costs in our scheme are finished in preparation phase (i.e. user registration). Compared with the existing schemes, our scheme is more efficient.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권6호
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• pp.2518-2533
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• 2020

In wireless sensor networks, adversaries may physically capture sensor nodes on the fields, and use them to launch false positive attacks (FPAs). FPAs could be conducted by injecting forged or old sensing reports, which would represent non-existent events on the fields, with the goal of disorientating the base stations and/or reducing the limited energy resources of sensor nodes on the fields. Researchers have proposed various mitigation methods against FPAs, including the statistical en-route filtering scheme (SEF). Most of these methods are based on key pre-distribution schemes and can efficiently filter injected false reports out at relay nodes through the verification of in-transit reports using the pre-distributed keys. However, their filtering power may decrease as time goes by since adversaries would attempt to capture additional nodes as many as possible. In this paper, we propose an adaptive key distribution method that could maintain the security power of SEF in WSNs under such circumstances. The proposed method makes, if necessary, BS update or re-distribute keys, which are used to endorse and verify reports, with the consideration of the filtering power and energy efficiency. Our experimental results show that the proposed method is more effective, compared to SEF, against FPAs in terms of security level and energy saving.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권3호
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• pp.1249-1272
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• 2016

In this paper, we propose a symmetric key establishment scheme for wireless sensor networks which tries to minimize the resource usage while satisfying the security requirements. This is accomplished by taking advantage of the communication pattern of wireless sensor networks and adopting heterogeneous wireless sensor networks. By considering the unique communication pattern of wireless sensor networks due to the nature of information gathering from the physical world, the number of keys to be established is minimized and, consequently, the overhead spent for establishing keys decreases. With heterogeneous wireless sensor networks, we can build a hybrid scheme where a small number of powerful nodes do more works than a large number of resource-constrained nodes to provide enhanced security service such as broadcast authentication and reduce the burden of resource-limited nodes. In addition, an on-demand key establishment scheme is introduced to support extra communications and optimize the resource usage. Our performance analysis shows that the proposed scheme is very efficient and highly scalable in terms of storage, communication and computation overhead. Furthermore, our proposed scheme not only satisfies the security requirements but also provides resilience to several attacks.

• Journal of the Korean Wood Science and Technology
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• 제15권1호
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• pp.22-55
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• 1987

본(本) 연구(硏究)는 육안적(肉眼的) 특성(特性)에 의한 목재식별(木材識別)의 속보(續報)로써 앞으로 생산가능(生産可能)한 한국산(韓國産) 단판수종(單板樹種)의 현미경적(顯微鏡的) 목재특성(木材特性)을 조사(調査)하여 합판공업(合板工業)에 필요(必要)한 기초자료(基礎資料)를 제공하기 위하여 실시(實施)하였다. 선정(選定)된 50수종(樹種)의 현미경적(顯微鏡的) 특성(特性)을 조사(調査)하여 수종별(樹種別)로 기재(記載)하였고 이를 바탕으로 하여 침엽수재(針葉樹材) 및 활엽수재별(闊葉樹材別)로 목재식별(木材識別) 검색표(檢索表)를 간략(簡略)하게 보고(報告)하면 다음과 같다.

• Structural Engineering and Mechanics
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• 제64권2호
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• pp.213-223
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• 2017

Bridges are lifeline and integral components of transportation system that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. The vulnerability assessment of bridges common in Pakistan is very important as it is seismically very active region and the available code for the seismic design of bridges is obsolete. This research presents seismic vulnerability assessment of three real case simply supported multi-span reinforced concrete bridges commonly found in northern Pakistan, having one, two and three bents with circular piers. The vulnerability assessment is carried through the non-linear dynamic time history analyses for the derivation of fragility curves. Finite element based numerical models of the bridges were developed in MIDAS CIVIL (2015) and analyzed through with non-linear dynamic and incremental dynamic analyses, using a suite of bridge-specific natural spectrum compatible ground motion records. Seismic responses of shear key, bearing pad, expansion joint and pier components of each bridges were recorded during analysis and retrieved for performance based analysis. Fragility curves were developed for the bearing pads, shear key, expansion joint and pier of the bridges that first reach ultimate limit state. Dynamic analysis and the derived fragility curves show that ultimate limit state of bearing pads, shear keys and expansion joints of the bridges exceed first, followed by the piers ultimate limit state for all the three bridges. Mean collapse capacities computed for all the components indicated that bearing pads, expansion joints, and shear keys exceed the ultimate limit state at lowest seismic intensities.