• Journal of KIISE:Databases
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• v.34 no.1
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• pp.84-97
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• 2007

Selectivity estimation techniques in query optimization have been used in commercial databases and histograms are popularly used for the selectivity estimation. Recently, the techniques for spatio-temporal databases have been restricted to existing temporal and spatial databases. In addition, the selectivity estimation techniques focused on time-series data such as moving objects. It is also impossible to estimate selectivity for range queries with a time interval. Therefore, we construct two histograms, CMH (current multidimensional histogram) and PMH (past multidimensional histogram), to estimate the selectivity of multidimensional sequence data in spatio-temporal databases and propose effective selectivity estimation methods using the histograms. Furthermore, we solve a problem about the range query using our proposed histograms. We evaluated the effectiveness of histograms for range queries with a time interval through various experimental results.

• Environmental and Resource Economics Review
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• v.15 no.5
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• pp.961-974
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• 2006

This paper estimates output and price elasticities of the industrial water in order to provide the government with tools that help make educated decisions with regard with the water provision policies rendering the latter more efficient. The estimated output elasticity produces useful insights on the role of industrial water as an input into the production process while the estimate of price elasticity enablesus to forecast the effects of various water pricing policies. This paper employs the marginal productivity method in order to estimate the abovementioned elasticities. The magnitude of the estimated output elasticity imply that the value of industrial water is much higher than its average price while the price elasticity estimate suggests that the water pricing policy can be an effective tool of controlling the demand for industrial water.

• Journal of Internet of Things and Convergence
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• v.2 no.4
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• pp.35-39
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• 2016

This paper is about IoT(Internet of Things)-based indoor localization scheme. GPS and WiFi are widely used to estimate the location of things. However, GPS has drawback of poor reception and radio disturbance in doors. To estimate the location in WiFi-based method, the user collects the information by scanning nearby WiFi(s) and transferring the information to WiFi database server. This is a fingerprint method with disadvantage of having an additional DB server. IoT is the internetworking of things, and this is on rapid rise. I propose the IoT-based indoor localization scheme. Under the proposed method, a device internetworking with another device with its own location information like GPS coordinate can estimate its own location through RSSI. With more devices localizing its own, the localization accuracy goes high. The proposed method allows the user to estimate the location without GPS and WiFi DB server.

• Korean Journal of Construction Engineering and Management
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• v.15 no.6
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• pp.44-52
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• 2014

Generally, the most difficult works at scheduling are to estimate the duration of activities and linkages between them because the possibility that the duration and linkages could be exposed to the uncertainties is so high. When estimating a project duration, therefore, the probabilistic estimation of the duration as well as the probabilistic estimation of the linkages between activities should be considered concurrently. The PERT that is one of the most popular techniques applied for the probabilistic estimation of a project duration can not consider the uncertainties of the linkages because it only estimates the probabilistic duration limited to 'FS0' relationship. The purpose of this study is to propose the new method "PLET" for stochastically estimating the project duration based on the probabilistic estimation of the BDM's relationships, and also provide more wide and various probabilsitic information about the project duration by it.

• Journal of the Korea Society of Computer and Information
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• v.16 no.9
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• pp.155-162
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• 2011

It is using to incident angle estimation technique in order to target estimation in radar. This paper was estimated incident angle estimation for target using adaptive array incident angle and single look error incident angle estimation technique. We estimated signal incident angle of target to removal main lobe and side lobe to adaptive array incident angle technique. It is difficult to correctly target estimation because single look technique increase direction error of signal incident angle. In order to receive a desired target signal must be not almost look error between signal incident angle and look angle. we had decreased to occur a look error using delay time and single look condition to calculation a covariance when incident angle estimate. Through simulation, we show that the proposed incident angle estimation technique improves the performance of target estimation compared to previous method.

• The Korean Journal of Applied Statistics
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• v.23 no.5
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• pp.891-908
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• 2010

In Korea, the small area estimation method is currently unpopular in generating o cial statistics. Because it may be difficult to determine the reliability for small area estimation, although small area estimation ha a sufficiently good advantage to generate small area statistics for Korea. This paper inspects the method of making small area unemployment through the small area estimation method. To estimate small area unemployment we used an EBLUP-type estimator based on a logistic linear mixed model. To evaluate the EBLUP-type estimator we accomplished the real data analysis and simulation experiment from the population and housing census data. In addition, small area estimates are compared to large sample survey estimates. We found the provided method in this paper is highly recommendable to generate small area unemployment as the official statistics.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.12
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• pp.76-84
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• 1999

This paper presents an integrated method for aircraft position estimation using sequential aerial images. The proposed integrated system for position estimation is composed of two parts: relative position estimation and absolute position estimation. Relative position estimation recursively computes the current position of an aircraft by accumulating relative displacement estimates extracted from two successive aerial images. Simple accumulation of parameter values decreases reliability of the extracted parameter estimates as an aircraft goes on navigating, resulting in large position error. Therefore absolute position estimation is required to compensate for the position error generated in relative position estimation. Absolute position estimation algorithms by image matching or digital elevation model (DEM) matching are presented. In image matching, a robust oriented Hausdorff measure (ROHM) is employed whereas in DEM matching an algorithm using multiple image pairs is used. Computer simulation with four real aerial image sequences shows the effectiveness of the proposed integrated position estimation algorithm.

• Journal of Advanced Navigation Technology
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• v.10 no.4
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• pp.385-393
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• 2006

In this paper, we proposed a location estimation algorithm considering an extension of searching area in 2.45GHz band RTLS and analyzed its performance in terms of an average estimation error distance. The extendable searching area was assumed to be square of $300m{\times}300m$ and 2 dimensions. The arrangement shape of available readers was considered circle, rectangle, and shrinkage rectangle for extendable searching area. Also, we assumed that propagation path was LOS (Line-Of-Sight) environment, and analyzed the estimation error performance as a function of the number of received sub-blink considering an arrangement shape of available readers in searching area. From the results, compared with rectangle shape, circle shape showed the higher estimation accuracy. Also, we confirmed that the proposed location estimation algorithm provided high estimation accuracy in the shrinkage rectangle shape that was suitable for extension of searching area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9C
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• pp.778-785
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• 2010

This paper proposes a high-precision ranging scheme based on channel estimation technique and multipath delay analysis in IR-UWB systems. When the IR-UWB signal is transmitted and received, the high-precision ranging is estimated with the time-of-arrival information of the signal. In the proposed scheme, the channel estimation process with the minimum mean square error technique or zero forcing technique is performed and the overlapped multipath within the pulse is analyzed with matrix pencil (MP) algorithm to achieve the ranging accuracy of centimeters. The performance of proposed scheme is evaluated with various IEEE 802.15.4a channel models and the relationship between the ranging performance and the computational complexity is analyzed in terms of the MP parameter values.

• The Korean Journal of Financial Management
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• v.12 no.2
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• pp.73-93
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• 1995

본 연구는 주식시장에서의 체결가격을 균형가격으로 가정하여 계산된 수익률에 관한 통계추정치의 편의에 관하여 분석하고 있다. 주식수익률의 통계적모멘트를 추정하는 것은 주식가격의 행태를 분석하는 연구 및 사건연구등에서 많은 학자들에 의하여 수행되어 왔다. 기존의 대부분의 연구들은 시장에서 체결된 가격이 그 시점의 진정한 균형가격이라는 가정하에 수익률을 계산하고 이 수익률 자료로부터 수익률의 평균, 표준편차, 외도(skewness), 침도(kurtosis) 등의 통계적모멘트를 추정하였다. 그러나 체결가격은 시장의 규칙에 의해 일정한 호가단위로만 거래될 뿐 아니라 매도 또는 매수호가에 거래됨으로써 진정한 균형가격과의 괴리가 있을 수 있게 된다. 본 연구는 주식호가단위의 불연속성과 매도매수호가의 차이로 연한 통계추정치의 편의에 관한 모형을 도출하여 편의의 크기와 특징을 분석하고, 이를 수정하는 간편식을 도출하여 그 유효성을 검증하고 있다. Gottlieb and Kalay(1985), Ball(1988), Cho and frees(1988)등은 1/8 달러의 최소호가단위로 인하여 발생하는 기존의 분산추정치의 편의를 계산하고 이를 수정하는 간편식을 제시하였다. French and Roll(1986)은 휴일이 포함된 기간의 수익률 분산과 평일 분산추정치의 비율이 기간과 비례하지 않는 원인중 하나는 매도매수호가차이로 인한 분산추정치의 편의라는 점을 설명한 바 있다. Choi and Shastri(1989)는 Black and Scholes 옵션가격 결정모형 이 주식 분산값의 크기에 따라 일정한 편의를 보이는 주요한 원인은 퍼센티지 매도매수호가차이와 옵션가격이 모두 진정한 분산치의 정의 함수이기 때문이라는 점을 보였다. Harris(1988)와 최종연(1994)는 주가의 불연속성 및 매도매수호가차이를 동시에 고려하여 기존의 분산추정치가 어떠한 편의를 보이는지에 관하여 분석한 바 있다. 본 연구에서는 최종연(1994)의 연구에서 도출된 모형을 연장하여 국내 주식시장과 같이 주가 수준에 따라 최소호가단위가 변화할 때의 변형모형을 도출하였다. 또한 이 모형에 따라 통계추정치의 편의를 수익률의 표준편차를 중심으로 계산하여 그 정도를 미국시장의 경우와 비교하였고, 그 추정치의 수정 방법에 대하여 호가단위가 변화하는 주가금액이 10,000원 주변일 경우를 중심으로 분석하였다.