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고차원 공간에서 최근접 질의를 효과적으로 처리하기 위한 새로운 인덱싱 기법
김상욱(Sang-Wook Kim),Charu Aggarwal(Charu Aggarwal),Philip S. Yu(Philip S. Yu) 한국정보과학회 2000 한국정보과학회 학술발표논문집 Vol.27 No.2Ⅰ
최근접 질의(nearest neighbor query)는 멀티미디어 데이터베이스에서 주어진 질의 객체와 가장 유사한 객체를 찾기 위한 매우 중요한 연산으로 사용된다. 대부분의 최근접 질의 처리 기법들은 객체의 효과적인 인덱싱을 위하여 다차원 인덱스(multidimensional index)를 사용한다. 그러나 N차원 사각형 혹은 원을 사용하여 객체 클러스터의 캡슐을 표현하는 기존의 다차원 인덱스들은 차원 수가 높아짐에 따라 검색 성능이 크게 떨어진다. 본 논문에서는 이러한 문제를 해결하는 새로운 인덱스 구조를 제시하고, 이를 이용하는 최근접 질의 처리 방안을 제안한다. 또한, 다양한 실험에 의한 성능 평가를 통하여 제안된 기법의 우수성을 검증한다.
Tuning the graphene work function by electric field effect.
Yu, Young-Jun,Zhao, Yue,Ryu, Sunmin,Brus, Louis E,Kim, Kwang S,Kim, Philip American Chemical Society 2009 Nano letters Vol.9 No.10
<P>We report variation of the work function for single and bilayer graphene devices measured by scanning Kelvin probe microscopy (SKPM). By use of the electric field effect, the work function of graphene can be adjusted as the gate voltage tunes the Fermi level across the charge neutrality point. Upon biasing the device, the surface potential map obtained by SKPM provides a reliable way to measure the contact resistance of individual electrodes contacting graphene.</P>
Hiding Sensitive Frequent Itemsets by a Border-Based Approach
Sun, Xingzhi,Yu, Philip S. Korean Institute of Information Scientists and Eng 2007 Journal of Computing Science and Engineering Vol.1 No.1
Nowadays, sharing data among organizations is often required during the business collaboration. Data mining technology has enabled efficient extraction of knowledge from large databases. This, however, increases risks of disclosing the sensitive knowledge when the database is released to other parties. To address this privacy issue, one may sanitize the original database so that the sensitive knowledge is hidden. The challenge is to minimize the side effect on the quality of the sanitized database so that non-sensitive knowledge can still be mined. In this paper, we study such a problem in the context of hiding sensitive frequent itemsets by judiciously modifying the transactions in the database. Unlike previous work, we consider the quality of the sanitized database especially on preserving the non-sensitive frequent itemsets. To preserve the non-sensitive frequent itemsets, we propose a border-based approach to efficiently evaluate the impact of any modification to the database during the hiding process. The quality of database can be well maintained by greedily selecting the modifications with minimal side effect. Experiments results are also reported to show the effectiveness of the proposed approach.
Hiding Sensitive Frequent Itemsets by a Border- Based Approach
Xingzhi Sun,Philip S. Yu 한국정보과학회 2007 Journal of Computing Science and Engineering Vol.1 No.1
Nowadays, sharing data among organizations is often required during the business collaboration. Data mining technology has enabled efficient extraction of knowledge from large databases. This, however, increases risks of disclosing the sensitive knowledge when the database is released to other parties. To address this privacy issue, one may sanitize the original database so that the sensitive knowledge is hidden. The challenge is to minimize the side effect on the quality of the sanitized database so that non-sensitive knowledge can still be mined. In this paper, we study such a problem in the context of hiding sensitive frequent itemsets by judiciously modifying the transactions in the database. Unlike previous work, we consider the quality of the sanitized database especially on preserving the non-sensitive frequent itemsets. To preserve the non-sensitive frequent itemsets, we propose a border-based approach to efficiently evaluate the impact of any modification to the database during the hiding process. The quality of database can be well maintained by greedily selecting the modifications with minimal side effect. Experiments results are also reported to show the effectiveness of the proposed approach.
Singular Value Decomposition 기반 고차원 인덱스 구조
김상욱,Charu Aggarwal,Philip S. Yu 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.B
The nearest neighbor query is an important operation widely used in multimedia databases for finding the object that is most similar to a given query object. Most of techniques for processing nearest neighbor queries employ multidimensional indexes for effective indexing of objects. However, the performance of previous multidimensional indexes, which use N-dimensional rectangles or spheres for representing the capsule of the object cluster, deteriorates seriously as the number of dimensions gets higher. This problem and the query processing method using it. We also verify the superiority of our approach through performance evaluation by performing extensive experiments.
Single‐Gate Bandgap Opening of Bilayer Graphene by Dual Molecular Doping
Park, Jaesung,Jo, Sae Byeok,Yu, Young‐,Jun,Kim, Youngsoo,Yang, Jae Won,Lee, Wi Hyoung,Kim, Hyun Ho,Hong, Byung Hee,Kim, Philip,Cho, Kilwon,Kim, Kwang S. WILEY‐VCH Verlag 2012 ADVANCED MATERIALS Vol.24 No.3
<P><B>Dual doping‐driven perpendicular electric field with opposite directions</B> remarkably increase the on/off current ratio of bilayer graphene field‐effect transistors. This unambiguously proves that it is possible to open a bandgap with two molecular dopants (F4‐TCNQ and NH<SUB>2</SUB>‐functionalized self‐assembled monolayers (SAMs)) even in a single‐gate device structure.</P>
Nanoscale Bipolar and Complementary Resistive Switching Memory Based on Amorphous Carbon
Yang Chai,Yi Wu,Takei, Kuniharu,Hong-Yu Chen,Shimeng Yu,Chan, Philip C. H.,Javey, Ali,Wong, H.-S Philip IEEE 2011 IEEE transactions on electron devices Vol.58 No.11
<P>There has been a strong demand for developing an ultradense and low-power nonvolatile memory technology. In this paper, we present a carbon-based resistive random access memory device with a carbon nanotube (CNT) electrode. An amorphous carbon layer is sandwiched between the fast-diffusing top metal electrode and the bottom CNT electrode, exhibiting a bipolar switching behavior. The use of the CNT electrode can substantially reduce the size of the active device area. We also demonstrate a carbon-based complementary resistive switch (CRS) consisting of two back-to-back connected memory cells, providing a route to reduce the sneak current in the cross-point memory. The bit information of the CRS cell is stored in a high-resistance state, thus reducing the power consumption of the CRS memory cell. This paper provides valuable early data on the effect of electrode size scaling down to nanometer size.</P>
Singular value decomposition 기반 고차원 인덱스 구조
김상욱(Kim Sang Wook),Charu Aggarwal,Philip S. Yu 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.1
The nearest neighbor query is an important operation widely used in multimedia databases for finding the object that is most similar to a given query object. Most of techniques for processing nearest neighbor queries employ multidimensional indexes for effective indexing of objects. However, the performance of previous multidimensional indexes, which use N-dimensional rectangles or spheres for representing the capsule of the object cluster, deteriorates seriously as the number of dimensions gets higher. This problem and the query processing method using it. We also verify the superiority of our approach through performance evaluation by performing extensive experiments.