• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.595-597
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• 2004

In this paper range measurement systems using ultrasonic and visual sensors are designed. By varying the focus of a camera, the range to a target pattern is computed. Pour different methods are tested for the focusing-based range measurement. The best result is obtained when counting edge pixels found by Laplacian operator. Higher accuracy can be obtained by fusing the measurement of camera focusing with that of ultrasonic sensor. The system designed is experimented within the range of 300-450mm.

• Journal of Communications and Networks
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• 제7권4호
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• pp.478-488
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• 2005

To conserve the usage of energy, indexing techniques have been developed in a wireless mobile environment. However, the use of interleaved index segments in a broadcast cycle increases the average access latency for the clients. In this paper, we present the broadcast-based location dependent data delivery scheme (BBS) for dynamic range queries. In the BBS, broadcasted data objects are sorted sequentially based on their locations, and the server broadcasts the location dependent data along with an index segment. Then, we present a data prefetching and caching scheme, designed to reduce the query response time. The performance of this scheme is investigated in relation to various environmental variables, such as the distributions of the data objects, the average speed of the clients, and the size of the service area.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.419-422
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• 2001

The electrical properties of Pr$_{6}$O$_{11}$-based ZnO varistors composed of ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_2$O$_3$-Dy$_2$O$_3$- based ceramics were investigated with CoO content in the range of 0.5~5.0 mol%. As CoO content is increased, the average grain size and the density were increased in the range of 9.86~27.22 $\mu$m and in the range of 5.25-5.55 g/cm$^3$, respectively. The varistor voltage was decreased in the range of 235.32~86.01 V/mm due to the increase of average grain size with CoO content. The varistors doped with CoO in the rage of 1.0~2.0 mol% exhibited a high nonlinearity, in which is above 55 in the nonlinear exponent and below 1.5 $\mu$A in the leakage current. Increasing CoO content further greatly decreased the nonlinearity.ity.ity.

• 전자공학회논문지S
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• 제35S권9호
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• pp.95-103
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• 1998

본 논문에서는 거리영상과 발기영상의 fusion을 이용한 영상분할을 제안한다. Bayes 이론을 기반으로 하여 Markov random field (MRF)로 선험적인 정보를 모델링한다. 거리영상과 밝기영상에서 추출한 특징을 이용하여 maximum a posteriori (MAP) 추정기를 구성한다. 거리영상에서 물체는 국부적인 평면으로 근사되어 각 점마다 평면 계수를 추정해 계수 공간을 구성한다. 밝기영상에서는 ${\alpha}$ 트림드 (${\alpha}$-trimmed) 분산이 밝기특성을 구성한다. 각 공간상의 특징을 에지에 대한 likelihood를 설정하여 구성된 MAP 추정기를 최적화함으로써 영상을 분할한다. 모의실험을 통해 제안된 구조가 그림자, 잡음 그리고 광원의 blurring에 관계없이 영상을 잘 분할한 것을 보였다.

• 대한임베디드공학회논문지
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• 제4권1호
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• pp.42-49
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• 2009

Most Vehicular Ad hoc Network (VANET) applications rely heavily on broadcast transmission of traffic related information to all reachable nodes within a certain geographical area. Among various broadcast approaches, flooding is the first broadcasting technique. Each node rebroadcasts the received message exactly once, which results in broadcast storm problems. Some mechanisms have been proposed to improve flooding in Mobile Ad hoc Networks (MANET), but they are not effective for VANET and only a few studies have addressed this issue. We propose two distance-based and timer-based broadcast suppression techniques: 15P(15percent) and slotted 15P. In the first (distance based) scheme, node's transmission range is divided into three ranges (80%,15%and5%). Only nodes within 15% range will rebroadcast received packet. Specific packet retransmission range (15%) is introduced to reduce the number of messages reforwarding nodes that will mitigate the broadcaststorm. In the second (timer-based) scheme, waiting time allocation for nodes within 15% range isused to significantly reduce the broadcaststorm. The proposed schemes are distributed and reliedon GPS information and do not requireany other prior knowledge about network topology. To analyze the performance of proposed schemes, statistics such as link load and the number of retransmitted nodes are presented. Our simulation results show that the proposed schemes can significantly reduce link load at high node densities up to 90 percent compared to a simple broadcast flooding technique.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권8호
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• pp.3889-3903
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• 2017

Fast and accurate localization of randomly deployed nodes is required by many applications in wireless sensor networks (WSNs). However, mobile nodes localization in WSNs is more difficult than static nodes localization since the nodes mobility brings more data. In this paper, we propose a Range-based Monte Carlo Box (RMCB) algorithm, which builds upon the Monte Carlo Localization Boxed (MCB) algorithm to improve the localization accuracy. This algorithm utilizes Received Signal Strength Indication (RSSI) ranging technique to build a sample box and adds a preset error coefficient in sampling and filtering phase to increase the success rate of sampling and accuracy of valid samples. Moreover, simplified Particle Swarm Optimization (sPSO) algorithm is introduced to generate new samples and avoid constantly repeated sampling and filtering process. Simulation results denote that our proposed RMCB algorithm can reduce the location error by 24%, 14% and 14% on average compared to MCB, Range-based Monte Carlo Localization (RMCL) and RSSI Motion Prediction MCB (RMMCB) algorithm respectively and are suitable for high precision required positioning scenes.

• Communications for Statistical Applications and Methods
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• 제4권2호
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• pp.507-514
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• 1997

Three kinds of unbiased estimators of standard deviation in a truncated arcsine distribution based on the quasi-range, the jackknife quasi-range, and the angle jackknife range are proposed and numerically compared each other in a sense of MSE.

• 한국통신학회논문지
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• 제39A권9호
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• pp.519-527
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• 2014

적응 어레이는 조향벡터를 이용하여 조향벡터 방향의 신호는 보호하면서 간섭신호를 제거한다. 조향벡터에 에러가 있으면 원하는 신호도 감쇠되어 SINR(signal-to-interference-plus-noise ratio) 성능 저하를 가져온다. 본 논문에서는 원하는 신호의 도래범위를 이용하여 조향벡터 에러에 강인한 적응 빔 형성 기법을 제시한다. 제시된 기법에서는 도래범위에서 어레이 응답벡터에 관한 상관행렬을 적분을 통해 구하고, 이 상관행렬의 고유벡터 일부를 이용하여 조향벡터를 구하기 위한 최소화 문제를 정의한다. 이 최소화 문제를 컨벡스 최적화(convex optimization)의 일종인 SDP(semidefinite program) 문제로 완화하여 효과적으로 해결한다. 시뮬레이션 결과에 따르면, 제안방식은 기존의 강인한 빔 형성 방식인 ORM(outside-range-based method), USM(uncertainty-based method)보다 우수한 SINR 성능을 나타낸다.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2008년도 공동추계학술대회
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• pp.297-302
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• 2008

The positioning technology for a moving object is an important and essential component of ubiquitous computing environment and applications, for which Radio Frequency Identification(RFID) has been considered as a core technology. RFID-based positioning system calculates the position of moving object based on k-nearest neighbor(k-nn) algorithm using detected k-tags which have known coordinates and kcan be determined according to the detection range of RFID system. In this paper, RFID-based positioning system determines the position of moving object not using weight factor which depends on received signal strength but assuming that tags within the detection range always operate and have same weight value. Because the latter system is much more economical than the former one. The geometries of tags were determined with considerations in huge buildings like office buildings, shopping malls and warehouses, so they were determined as the line in I-Dimensional space, the square in 2-Dimensional space. In 1-Dimensional space, the optimal detection range is determined as 125% of the tag spacing distance through the analytical and numerical approach. Here, the analytical approach means a mathematical proof and the numerical approach means a simulation using matlab. But the analytical approach is very difficult in 2-Dimensional space, so through the numerical approach, the optimal detection range is determined as 134% of the tag spacing distance in 2-Dimensional space. This result can be used as a fundamental study for designing RFID-based positioning system.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2008년도 공동추계학술대회
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• pp.270-271
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• 2008

The positioning technology for a moving object is an important and essential component of ubiquitous communication computing environment and applications, for which Radio Frequency IDentification Identification(RFID) is has been considered as also a core technology for ubiquitous wireless communication. RFID-based positioning system calculates the position of moving object based on k-nearest neighbor(k-nn) algorithm using detected k-tags which have known coordinates and k can be determined according to the detection range of RFID system. In this paper, RFID-based positioning system determines the position of moving object not using weight factor which depends on received signal strength but assuming that tags within the detection range always operate and have same weight value. Because the latter system is much more economical than the former one. The geometries of tags were determined with considerations in huge buildings like office buildings, shopping malls and warehouses, so they were determined as the line in 1-Dimensional space, the square in 2-Dimensional space and the cubic in 3-Dimensional space. In 1-Dimensional space, the optimal detection range is determined as 125% of the tag spacing distance through the analytical and numerical approach. Here, the analytical approach means a mathematical proof and the numerical approach means a simulation using matlab. But the analytical approach is very difficult in 2- and 3-Dimensional space, so through the numerical approach, the optimal detection range is determined as 134% of the tag spacing distance in 2-Dimensional space and 143% of the tag spacing distance in 3-Dimensional space. This result can be used as a fundamental study for designing RFID-based positioning system.