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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>
김상욱(Sang-Wook Kim),Charu Aggarwal(Charu Aggarwal),Philip Yu(Philip Yu) 한국정보과학회 2001 정보과학회논문지 : 데이타베이스 Vol.28 No.4
최근접 질의(nearest neighbor query)는 멀티미디어 데이타베이스에서 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 단순한 캡슐 표현 방식이 최근접 질의 처리의 성능을 저하시키는 주요 원인임을 지적하고, (1) 클러스터에 적합한 새로운 축 시스템(axis system)의 채택, (2) 원과 사각형의 조합에 의한 다양한 캡슐 형태의 표현, (3) 아웃 라이어(outlier)의 별도 관리 등의 해결 방안을 제안한다. 또한, 이러한 개념들을 채택하는 인덱싱 구조를 제시하고, 이를 이용하는 최근접 질의 처리 방안을 제안한다. 끝으로, 다양한 실험에 의한 성능 평가를 통하여 제안된 기법의 우수성을 검증한다. 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. In this paper, we first point out the fact that the simple representation of capsules incurs performance degradation in processing nearest neighbor queries. For alleviating this problem, we propose (1) adopting new axis systems appropriate to a given cluster, (2) representing various shapes of capsules by combining rectangles and spheres, and (3) maintaining outliers separately. We also verify the superiority of our approach through performance evaluation by performing extensive experiments.
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.
Yu, Youngseok,Koh, Yoobin Esther,Lim, Hojoon,Jeong, Beomgyun,Isegawa, Kazuhisa,Kim, Daehyun,Ueda, Kohei,Kondoh, Hiroshi,Mase, Kazuhiko,Crumlin, Ethan J,Ross Jr, Philip N,Gallet, Jean-Jacques,Bournel, Institute of Physics 2017 Journal of Physics, Condensed Matter Vol.29 No.46
<P>The study of CO oxidation on Pt(1 1 0) surface is revisited using ambient pressure x-ray photoemission spectroscopy. When the surface temperature reaches the activation temperature for CO oxidation under elevated pressure conditions, both the <I>α</I>-phase of PtO<SUB>2</SUB> oxide and chemisorbed oxygen are formed simultaneously on the surface. Due to the exothermic nature of CO oxidation, the temperature of the Pt surface increases as CO oxidation takes place. As the CO/O<SUB>2</SUB> ratio increases, the production of CO<SUB>2</SUB> increases continuously and the surface temperature also increases. Interestingly, within the diffusion limited regions, the amount of surface oxide changes little while the chemisorbed oxygen is reduced.</P>
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>
A Methodology for Generating Process File for Circuit Simulation Using a Modified BSIM2 Model
Lin, Wallace,Yu, Michael,Husain, Asim,Chan, Philip 대한전자공학회 1993 ICVC : International Conference on VLSI and CAD Vol.3 No.1
This paper describes a methodology for generating process file, a file containing transistor model parameters for circuit simulation, based on a modified BSIM2 circuit simulation model [1,2]. The methodology, different from those global-optimization-based ones, was designed for achieving high accuracy in simulating circuits where deep-submicron (L_(eff) $lt;0.5 ㎛) transistors are dominant components. The methodology consists of three parts - design of process isle transistors on test pattern, automatic characterization of model parameters, and modeling of geometry dependence on model parameters. Methods and approaches developed in this methodology are introduced.
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.
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.