• Journal of Broadcast Engineering
• /
• v.10 no.2
• /
• pp.174-181
• /
• 2005

In this paper, we proposed new fast scattered pilot synchronization techniques to reduce the burst synchronization time for the DVB-H receiving system with robustness. DVB-H terminals employ a TDM system called 'Time-Slicing' to reduce power consumption. In order to fully exploit the potential power reduction, the synchronization time for the DVB-H receiver must be very short. A typical DVB-T system uses the TPS Synchronization to determine the position of scattered pilots which are used for channel estimation, and it takes 68 OFDM symbol time. In this paper, several new fast scattered pilot synchronization techniques are proposed.

• Journal of the Korea Society of Computer and Information
• /
• v.16 no.5
• /
• pp.101-107
• /
• 2011

The optimum weight vector is studied to remove interference and jamming signals in adaptive array antenna system. The optimum weight vector is calculated to apply a minimum variance algorithm and cost function in linearly constrained conditions, and accurately estimates target's signal. Adaptive array antenna system is the system which improves signal to noise ratio(SNR) and decreases interference and jammer power. Adaptive array antenna system delays at tap output of antenna array element. Each tap finally makes the complex signal of one in multiplier complex weight. In order to obtain optimum's weight calculation, optimum weight vector is used in this paper. After simulation, resolution is increased below $3^{\circ}$, and sidelobe is decreased about 10 dB.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.44 no.2 s.314
• /
• pp.74-81
• /
• 2007

In this paper, an efficient SAD(Sum of Absolute Differences) processor structure for motion estimation of H.264 is proposed. SAD processors are commonly used both in full search methods for motion estimation and in fast search methods for motion estimation. Proposed structure consists of SAD calculator block, combinator block, and minimum value calculator block. Especially, proposed structure is simplified by using Distributed Arithmetic for addition operation. The Verilog-HDL(Hard Description Language) coding and FPGA(Field Programmable Gate Array) implementation results for the proposed structure show 39% and 32% gate count reduction in comparison with those of the conventional structure, respectively. Due to its efficient processing scheme, the proposed SAD processor structure can be widely used in size dominant H.264 chip.

• Journal of Energy Engineering
• /
• v.22 no.1
• /
• pp.1-7
• /
• 2013

This paper attempts to estimate the residential electricity demand function, using survey data of 521 households in Korea. As the residential electricity demand function provides us information on the pattern of consumer's electricity consumption, it can be usefully utilized in predicting the impact of policy variables such as electricity price and forecasting electricity demands. We apply least absolute deviation(LAD) estimation as a robust approach to estimating parameters. The results showed that price and income elasticities are -0.68 and 0.14 respectively, and statistically significant at the 10% levels. The price and income elasticities portray that residential electricity is price- and income-inelastic. This implies that the residential electricity is indispensable goods to human-being's life, thus the residential electricity demand would not be promptly adjusted to responding to price and/or income change.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.9
• /
• pp.782-791
• /
• 2013

This paper proposes the location estimation techniques of distributed targets with the multi-sensor data perceived through IR sensors of the military robots. In order to match up targets with measured azimuths, we apply the maximum likelihood (ML), depth-first, and breadth-first tree search algorithms, in which we use the measured azimuths and the number of pixels on IR screen for pruning branches and selecting candidates. After matching up targets with azimuths, we estimate the coordinate of each target by obtaining the intersection point of the azimuths with the least square error (LSE) algorithm. The experimental results show the probability of missing target, mean of the number of calculating nodes, and mean error of the estimated coordinates of the proposed algorithms.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.2
• /
• pp.331-338
• /
• 1990

In adaptive control, the lack of persistent and rich excitation causes the estimated parameters to drift, which degrade the performance of the system and may introduces instability to the system in a stochastic environment. To solve the problem of the parameter drift, the concept of single parameter adaptation is presented. For the parameter identification, a priori error is directly used for adaptation error. The structure of the controller is based upon the minimum variance control technique. The stability and robustness analysis is carried out by the sector stability theorem for the second order system. The computer simulation is performed to justify the theoretical analysis for the various cases.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2022.01a
• /
• pp.107-108
• /
• 2022

오늘날 도메인 네임 시스템(DNS) 서비스는 단순히 IP 주소를 .com, .net 등의 도메인으로 변환해주는 기능을 넘어 컨텐츠 가속(CDN) 서비스, 고가용성(HA) 서비스, 분산 서비스 거부공격(DDoS) 방어 서비스, 통신 구간 암호화 서비스로서 그 용도를 넓혀가고 있다. 이용자들은 이러한 업체가 외부 기관에 정보를 넘기지 않고, 모든 통신 구간은 서비스 업체도 그 내용을 들여다보지 못할 정도로 철저히 암호화한다는 도덕적인 영업과 운영을 할 것으로 기대하지만, 실제 사례를 살펴보면 그렇지 못하다는 점이 드러난다. 본 논문에서는 2021년 기준으로 최소 7년간 이어져온 것으로 추정되는 유명 DNS 서비스 업체의 보안접속 악용 사례를 중심으로 이러한 악용이 어떻게 이루어지고 이것에 대응하기 위해 사용할 수 있는 표준화 기술은 이 문제에 효용성이 있는지를 DNS 업체와 동일한 실제 환경 구성을 통해 검증하였다.

• Korean Business Review
• /
• v.7
• /
• pp.165-196
• /
• 1994

Harris(1986)[22]는 주식가격에 있어서의 요일효과(曜日效果)(day-of-the-week effect)의 증거는 광범위한 시장지수에서의 일별(日別) 종가(終價) 대 종가(終價)수익률(收益率)에 대한 연구들에서 나타난다고 한다. 이러한 연구들은 결론적으로 체계적 수익률 행태를, 특히 음(陰)의 월요일 수익률을 증명한다. Harris(1990)[24]는 군집현상(群集現象)은 가격이산성(價格離散性)이 추정량(推定量)에 미치는 영향을 분석할 때 고려되어야 한다고 주장한다. 특히, 군집현상(群集現象)이 거래자가 규정된 최소가격변동에 기초한 집합보다 더 큰 이산적(離散的)가격집합(價格集合)을 사용하기 때문에 결과한다면, Gottlieb 와 Kalay(1985)[21] 및 Harris(1990)[24]에서 확인된 분산(分散)과 시계열공분산(時系列共分散) 추정량(推定量) 편의(偏倚)는 훨씬 더 심각할 것이라고 한다. 또한 모든 연구들은 이산성(離散性)이 거래가격의 유의한 특성이기 때문에 군집현상(群集現象)을 고려하여야 한다고 한다. 주식시장의 경우 요일효과가 존재한다면, 관찰주가의 이산성(離散性)으로 인한 요일별 주가의 끝자리가격의 분포가 월요일과 다른 요일에 있어 차이가 있는지와 요일별 가격결정의 정도가 (1) 주가의 수준, (2) 주가수익률의 기복 및 (3) 시장에서의 주식거래량에 있어 차이가 있는지 둥에 대하여 의문을 갖게 한다. 따라서 본 연구는 이산성으로 인한 요일별 관찰주가의 군집현상에 관한 거래자료를 연구하기 위하여 한국 주식시장에서의 입수가능한 최근년도인 1990년 1월 4일에서 1994년 6월 30일까지의 4년 6개월 동안의 일별주가변동(日別株價變動) 거래자료(去來資料)를 조사하고 실증분석을 수행하였다. 본 연구의 결과에 의하면 주식가격에 있어서의 요일효과는 관찰가격의 이산성 특히, 호가(呼價)의 가격단위(價格單位)에 기인하는 것 같지는 않다. 그러나 본 연구의 결과에 의하면 최돈일(1993)[7]의 연구 결과에서와 같이 Gottlieb 와 Kalay(1985) [21] 및 Ball(1988)[9]의 주장을 받아들이기 어렵다. 최돈일(1993)[7]의 연구를 확장한 본 연구의 결과는 최돈일(1993)의 연구 결과와도 상이하다.

• Journal of Navigation and Port Research
• /
• v.43 no.1
• /
• pp.1-8
• /
• 2019

Identifying behavioral errors of seafarers that have led to marine accidents is a basis for research into prevention or mitigation of marine accidents. The purpose of this study is to estimate the optimal probability distribution function needed to model behavioral errors of crew members into three behaviors (i.e., Skill-, Rule-, Knowledge-based). Through use of behavioral data obtained from previous accidents, we estimated the optimal probability distribution function for the three behavioral errors and verified the significance between the probability values derived from the probability distribution function. Maximum Likelihood Estimation (MLE) was applied to the probability distribution function estimation and variance analysis (ANOVA) used for the significance test. The obtained experimental results show that the probability distribution function with the smallest error can be estimated for each of the three behavioral errors for eight types of marine accidents. The statistical significance of the three behavioral errors for eight types of marine accidents calculated using the probability distribution function was observed. In addition, behavioral errors were also found to significantly affect marine accidents. The results of this study can be applied to predicting marine accidents caused by behavioral errors.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6B
• /
• pp.551-560
• /
• 2010

This study presents the export of constituent transport loads through a river system. The proposed constituent transport load estimating procedure can be operated with the on-going Korean TMDL monitoring system. This study firstly discusses the use of a hydrologic simulation model (TANK) to estimate stream-flow for the 40 sub-catchments. Model parameters are estimated from 8-days intervals flow data which has been monitored by NIER since 2004. Constituent transport loads are estimated with the 7-parameter log linear model whose parameters are estimated by the minimum variance unbiased estimator. Results from Nakdong river basin reveals that the proposed procedure provides satisfactory TN, TP and SS transport load estimates. As an application, a representative load duration curve is derived to represent the overall hydrologic flux of TN, TP and SS at Nakdong river basin.