• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.2
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• pp.146-156
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• 2002

In this paper, a new virtual-straight line parameter determination methodology and fast time domain simulation technique for non-uniform interconnects are presented and verified. Time domain signal response of interconnects circuit considering the characteristic of non-linear transistor is performed by using model order reduction method. Since model order reduction method is peformed by using per unit length parameters, virtual- straight line parameters for non-uniform interconnects are determined. Its method is integrated into Berkeley SPICE and shown that time domain signal responses using proposed method have a good agreement with the results of conventional circuit simulator HSPICE. The proposed method can be efficiently employed in the high-performance VLSI circuit design since it can provide a fast and accurate time domain signal response of complicated multi - layer interconnects.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.4
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• pp.39-47
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• 2001

In this paper, the hydroelastic behavior of a mat-type large floating structure is analyzed in time domain by using mode superposition method. The time-memory function is estimated by Fourier transforming the wave damping coefficients, which are computed by a higher-order boundary element method based on potential theory. Meanwhile, the structural response is obtained by time integrating the eigenmodes of the structure. Numerical examples are made for three test cases on the scaled model of a mat-type large floating structure ; weight pull-up case, weight drop case and weight moving case. In all three cases, the numerical results coincide well with experimental data.

• 한국IT서비스학회:학술대회논문집
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• 2008.05a
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• pp.425-430
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• 2008

USN의 발전으로 인해 인간 중심의 정보화 사회에서 사물 간에도 정보들을 유기적으로 결합하여 활용하는 유비쿼터스 컴퓨팅 사회로 급격히 변모하고 있다. 이러한 유비쿼터스 컴퓨팅 인프라를 성공적으로 구축하기 위해서는 센서노드에 대한 기술의 발전과 함께 USN 미들웨어에 대한 연구가 필요하다. USN의 핵심기술 중 하나인 USN 미들웨어는 시스템 소프트웨어로써 USN 응용에서 USN 계층의 자원과 데이타를 쉽게 활용할 수 있도록 다양한 기본 서비스를 제공한다. USN 디렉토리 서비스는 이와 같은 USN 미들웨어의 핵심 컴포넌트로서 USN 응용이 필요로 하는 USN 자원에 대한 정보를 검색하는 기능을 수행한다. 분산된 USN 자원에 대한 메타데이타의 효율적인 검색은 분산된 환경에서의 USN 디렉토리 서비스의 핵심요소이며 최근 이에 대한 연구가 보이고 있다. 분산 USN 디렉토리 서비스에서의 메타데이타 검색 모델은 크게 중앙 집중식(Centralized) 모델, 계층식(Hierarchical) 모델, P2P(Peer-to-Peer) 모델이 있다. 그러나 현재 메타데이타 검색 모델에 대한 연구는 원하는 메타데이타를 찾기 위한 서버 검색 회수만을 대상으로 하고 있으며 실제 단말 간 응답시간에 영향을 미치는 지연시간은 고려하지 않고 있다. 본 논문은 실제 단말 간 응답시간에 영향을 미치는 검색회수와 지연시간을 고려한 하이브리드 모델을 제안하고, 하이브리드 모델이 계층 모델에서 검색 시 불필요한 검색횟수의 증가와 P2P 모델의 광범위한 지역에서 응답시간이 증가하게 되는 단점을 개선할 수 있음을 보인다.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.5 s.45
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• pp.75-86
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• 2005

In performance-based design methods, it is clear that the evaluation of the nonlinear response is required. Analysis methods available to the design engineer today are nonlinear time history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. The nonlinear time analysis is the most accurate method in computing the nonlinear response of structures, but it is time-consuming and necessitate more efforts. Some codes proposed the capacity spectrum method based on the nonlinear static analysis to determine earthquake-induced demand. The nonlinear direct spectrum method is proposed and studied to evaluate nonlinear response of structures, without iterative computations, given by the structural linear vibration period and yield strength from pushover analysis. The purpose of this paper is to compare the accuracy and the reliability of approximate nonlinear methods with respect to shear buildings and various earthquakes. The conclusions of this study are summarized as follows: 1) Linear capacity spectrum method may fail to find a convergent answer or make a divergence. Even if a convergent answer is found, it has a large error in some cases and the error varies greatly depending on earthquakes. 2) Although nonlinear capacity spectrum method need much less calculation than capacity spectrum method and find an answer in any case, it may be difficult to obtain an accurate answer and generally large error occurs. 3) The nonlinear direct spectrum method is thought to have good applicability because it produce relatively correct answer than other methods directly from pushover curves and nonlinear response spectrums without additional and iterative calculations.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.333-341
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• 2008

In this paper, a new interpolation model for the head related transfer function (HRTF) was proposed. In the method herein, we assume that the impulse response of the HRTF for each azimuth angle is given by linear interpolation of the time-delayed neighboring impulse responses of HRTFs. The time delay of the HRTF for each azimuth angle is given by sum of the sound wave propagation time from the ears to the sound source, which can be estimated by using azimuth angle, the physical shape of the underlying head and the distance between the head and sound source, and the refinement time yielding the minimum mean square error. Moreover, in the proposed model, the interpolation intervals were not fixed but varied, which were determined by minimizing the total number of HRTFs while the synthesized signals have no perceptual difference from the original signals in terms of sound location. To validate the usefulness of the proposed interpolation model, the proposed model was applied to the several HRTFs that were obtained from one dummy-head and three human heads. We used the HRTFs that have 5 degree azimuth angle resolution at 0 degree elevation (horizontal plane). The experimental results showed that using only $30\sim40%$ of the original HRTFs were sufficient for producing the signals that have no audible differences from the original ones in terms of sound location.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.9
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• pp.29-36
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• 2010

Consider an RFID network configured as a star such that a single reader is surrounded by a crowd of tags. In the RFID network, prior to attaining the information stored at a tag, the reader must cognize the tags while arbitrating a collision among tags' responses. For this purpose, we present a tag cognizance scheme based on framed and slotted ALOHA, which statically provides a number of slots in each frame for the tags to respond. For the evaluation of the cognizance performance, we choose the cognizance completion probability and the expected cognizance completion time as key performance measures. Then, we present a method to numerically calculate the performance measures. Especially, for small numbers of tags, we derive them in a closed form. Next, we formulate a problem to find an optimal time structure which either maximizes the cognizance completion probability under a constraint on the cognizance time or minimizes the expected cognizance completion time. By solving the problem, we finally obtain an optimal number of slots per frame for the tags to respond. From numerical results, we confirm that there exist a finite optimal number of slots for the tags to respond. Also, we observe that the optimal number of slots maximizing the cognizance completion probability tends to approach to the optimal number of slots minimizing the expected cognizance completion time as the constraint on the cognizance time becomes loose.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.384-394
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• 2001

In this paper, we propose AST-AET(Average valid Start Time-Average valid End Time) data migration strategy based on the storage structure where temporal data is divided into a past segment, a current segment, and a future segment. We define AST and AET which are used in AST-AET data migration strategy and also define entity versions to be stored in each segment. We describe methods to compute AST and AET, and processes to search entity versions for migration and move them. We compare average response times for user queries between AST-AET data migration strategy and the existing LST-GET(Least valid Start Time-Greatest valid End Time) data migration strategy. The experimental results show that, when there are no LLTs(Long Lived Tuples), there is little difference in performance between the two migration strategies because the size of a current segment is nearly equal. However, when there are LLTs, the average response time of AST-AET data migration strategy is smaller than that of LST-GET data migration strategy because the size of a current segment of LST-GET data migration strategy becomes larger. In addition, when we change average interarrival times of temporal queries, generally the average response time of AST-AET data migration strategy is smaller than that of LST-GET data migration strategy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.1-9
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• 2016

Railroad bridges account for 25% of the entire high-speed rail network. Railway bridges are subject to gradual structural degradation or fatigue accumulation due to consistent and repeating excitation by fast moving trains. Wireless sensing technology has opened up a new avenue for bridge health monitoring owing to its low-cost, high fidelity, and multiple sensing capability. On the other hand, measuring the transient response during train passage is quite challenging that the current wireless sensor system cannot be applied due to the intrinsic time delay of the sensor network. Therefore, this paper presents a framework for monitoring such transient responses with wireless sensing systems using 1) real-time excessive vibration monitoring through ultra-low-power MEMS accelerometers, and 2) post-event time synchronization scheme. The ultra-low power accelerometer continuously monitors the vibration and trigger network when excessive vibrations are detected. The entire network of wireless smart sensors starts sensing through triggering and the post-event time synchronization is conducted to compensate for the time error on the measured responses. The results of this study highlight the potential of detecting the impact load and triggering the entire network, as well as the effectiveness of the post-event time synchronized scheme for compensating for the time error. A numerical and experimental study was carried out to validate the proposed sensing hardware and time synchronization method.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.219-226
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• 2010

Current earthquake alert notification for immediate post-earthquake procedures for the critical facilities is exclusively dependent on the ground-motion intensity measures observed at the seismic station located within the site. This practice is prune to false notification due to a noise and problems of missing and poor quality records of the seismic station. The credibility of the earthquake alert notification can be enhanced by utilizing the multiple transformed records of the nearby seismic stations at other sites interconnected to the same earthquake monitoring system by a network. The time-domain transformation of the site-response between the seismic stations is implemented by convoluting the nearby records with a pair of forward and inverse FIR filters designed for the site response relative to a seismic basement. The transformed records from the nearby seismic stations can be used to estimate the ground-motion intensity measures missing at the site or to evaluate the data quality along with other various possible applications in the area of geoscience and earthquake engineering.

• Korean Journal of Health Education and Promotion
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• v.12 no.1
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• pp.128-150
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• 1995

본 연구의 목적은 중학생의 보건교육에 대한 요구도를 살피기 위해 먼저 현재 자신이 알고 있는 보건지식에 대한 만족도와 보건교육에 대한 필요도 및 이에 영향을 미치는 요인에 대해 알아보고, 이와 관련하여 보건지식에 대한 만족도와 보건교육에 대한 필요도가 보건교육 요구도에 미치는 영향을 분석해 보는 데 있다. 연구를 위한 조사대상으로 경기도 소재 M, S 중학교의 1,2학년 전체 학생 688명을 선정하였고, 1994년 12월 1일부터 15일까지 자기기입식 설문지를 통해 보건교육에 대한 요구도를 조사하였다. 본 연구의 결과는 다음과 같다. 1. 조사대상자의 분포는 남학생이 59.3%, 여학생이 40.7%였고, 자신의 건강상태에 대해 건강하다고 응답한 학생이 78.9%, 건강하지 않다고 응답한 학생이 21.1%였다. 또한 현재 알고 있는 보건지식에 대해 만족한다고 응답한 학생은 68.2%였고, 31.8%의 학생이 만족하지 않는다고 응답하였다. 보건교육에 대한 필요도에 대해서는 92.7%의 학생이 필요하다고 응답하였다. 2. 보건교육에 대한 요구도에서는 첫째, 보건교과설정에 대해 45.6%가 찬성하였고, 둘째, 보건교육 실시시기에 대해서는 82.8%가 유치원 및 국민학교에서부터 시작되어야 한다고 하였다. 셋째, 보건교육의 적정시간에 대해 82.4%가 1주일 또는 1달에 1-2시간이라고 하였으며, 넷째, 보건교육 담당교사에 대해서는 63.2%가 보건교육 전문가가 담당하여야 한다고 응답하였다. 다섯째, 보건교육 내용에 대한 선호도 순위는 구급처치, 안전교육, 영양, 환경, 음주와 흡연 및 약물남용, 구강보건, 개인위생, 식품위생, 전염병관리, 성교육, 건강과 운동, 정신건강, 비전염성질환 관리, 공중보건, 의료기관의 기능 순이었다. 3. 현재 알고 있는 보건지식에 대한 만족도에 영향을 미치는 변수로는 성(p<0.01). 형제순위(p<0.05), 아버지의 학력(p<0.01), 어머니의 학력(p<0.01), 학업성적(p<0.05)이었으며, 보건교육 필요도에 영향을 미치는 변수는 성(p<0.05), 어머니의 학력(p<0.05), 학업성적(p<0.01)이었다. 4. 현재 알고 있는 보건지식에 대한 만족도에 따라 보건교육에 대한 요구도에 차이가 나타났다. 보건지식에 대해 만족하고 있지 못한 비만족군의 경우 보건교과의 설정에 대해 만족군보다 더 적극적으로 찬성하였고(p<0.05), 보건교육의 실시 시기에 대해서는 유치원 시기부터가 적정하다고 응답하였다(p>0.01). 보건교육의 내용선정에 있어서도 만족군과 비만족군간의 차이가 나타났는데, 만족군의 경우는 안전교육, 건강과 운동, 공중보건, 비만족군의 경우는 성교육을 요구하였다(p<0.05). 5. 보건교육에 대한 필요도에 따라 보건교육에 대한 요구도에 차이가 나타났다. 보건교육이 필요하다고 응답한 필요군의 경우 보건교과의 설정에 대해 적극적으로 찬성하였다(p<0.01). 또한 필요군은 보건교육의 실시 시기에 대해 유치원 시기부터가 적정하다고 응답한 반면, 보건교육이 필요하지 않다고 한 비필요군의 경우는 중학교 이후부터 적정하다고 응답하였다(p<0,01). 보건교육의 내용선정에 있어서도 음주와 흡연 및 약물남용, 식품위생, 건강과 운동, 비전염성질환 예방을 제외한 내용에서 필요군과 비필요군간의 차이가 나타났다(p<0.05).