• Communications for Statistical Applications and Methods
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• 제17권4호
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• pp.599-609
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• 2010

확산모형은 금융현상을 모형화하기 위한 방법으로 자주 사용된다. 다양한 확산모형들을 추론하기 위한 다양한 추론기법들이 제안되어져 왔다. 본 연구에서는 시뮬레이션 방법을 통하여 Shoji와 Ozaki (1998)에 의하여 제안된 NLL 방법의 성질을 검토하여 보고, 실제 자료에 적용하게 된다.

• 한국군사과학기술학회지
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• 제19권2호
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• pp.155-162
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• 2016

TASS(Towed Array Sonar System) is a sonar system which tows the sensor array behind a platform. Array shape is generally assumed to be a straight line. But the array shape is often distorted by oceanic current or platform maneuvering which causes the performance loss of signal processing method like beamforming. So array shape estimation methods are needed. Typically the method based on Kalman filter using heading sensor is used. In practice, the measurement is corrupted by biases which are caused by rotation of the tow cable, varying magnetic fields and slowly varying stresses in the mechanical construction. Although they can't be calibrated but can be estimated. In this paper, we suggest the array shape estimation method based on Kalman filter compensating the sensor biases.

• 한국통신학회논문지
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• 제33권6C호
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• pp.505-511
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• 2008

위성 항법 시스템은 (global navigation satellite system, GNSS) 통신 물리계층으로 직접 수열 확산 대역 (direct sequence/spread spectrum, DS/SS) 시스템을 사용하고 있다. DS/SS 시스템은 확산된 정보를 복원하기 위해 한 칩 (chip) 또는 그 이하로 동기를 맞추는 획득 단계와 정확한 동기를 결정하고 유지하는 추적 단계를 수행한다. 가장 널리 알려진 추적 기법은 상관 값의 대칭성을 이용해 부호를 추적하는 $\Delta$-DLL이다 (single delta delay lock loop). 여기서, $\Delta$는 이른-늦은 상관 값의 상관 시간 옵셋 간격을 뜻한다. $\Delta$-DLL은 이상적인 환경에서 최적 부호 추적 기법이다. 그러나 이 기법은 다중경로 환경에서 상관 함수의 대칭성이 깨짐으로 인해 판별기 출력이 비대칭으로 나타나기 때문에 큰 추적 편이를 갖는다. 추적 편이는 정착한 동기 시점과 추적이 완료되어 결정한 동기 시점의 차이를 의미한다. 이러한 추적 편이를 감소시키기 위한 기법으로 작은 $\Delta$를 사용한 $\Delta$-DLL과 두 개의 $\Delta$-DLL을 조합한 ${\Delta}^{(2)}$-DLL이 (double delta DLL) 제안되었다. 그러나 두 기법 모두 여전히 추적 편이가 존재하며, 작은 $\Delta$를 사용하기 때문에 추적 단계의 동적 영역이 줄어들어 정확한 획득 단계가 요구되는 단점을 갖고 있다. 본 논문에서는 추적 편이를 효과적으로 줄이면서도 정확한 획득 단계가 요구되지 않는 상관 값의 최대 기울기 변화에 기반한 추적 편이 감소 기법을 제안한다.

• 한국물환경학회지
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• 제31권3호
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• pp.241-252
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• 2015

Runoff behaviors by five bias correction methods were analyzed, which were Change Factor methods using past observed and estimated data by the estimation scenario with average annual calibration factor (CF_Y) or with average monthly calibration factor (CF_M), Quantile Mapping methods using past observed and estimated data considering cumulative distribution function for entire estimated data period (QM_E) or for dry and rainy season (QM_P), and Integrated method of CF_M+QM_E(CQ). The peak flow by CF_M and QM_P were twice as large as the measured peak flow, it was concluded that QM_P method has large uncertainty in monthly runoff estimation since the maximum precipitation by QM_P provided much difference to the other methods. The CQ method provided the precipitation amount, distribution, and frequency of the smallest differences to the observed data, compared to the other four methods. And the CQ method provided the rainfall-runoff behavior corresponding to the carbon dioxide emission scenario of SRES A1B. Climate change scenario with bias correction still contained uncertainty in accurate climate data generation. Therefore it is required to consider the trend of observed precipitation and the characteristics of bias correction methods so that the generated precipitation can be used properly in water resource management plan establishment.

• 한국전자파학회논문지
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• 제30권2호
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• pp.169-172
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• 2019

FMCW 배열 안테나는 저비용 고해상도라는 장점 때문에 많은 분야에 널리 사용되고 있다. FMCW 배열을 이용하여 표적의 거리와 각도를 추정하기 위해서, 우선 deramped 수신신호로부터 거리-각도 행렬을 구성하고, 그 다음에 거리-각도 행렬에 2D-FFT와 같은 2차원 주파수 추정기법을 적용한다. 하지만, 이러한 주파수 추정기법은 bias 오차를 발생시키게 된다. 그 이유는 거리-각도 행렬의 두 개의 주파수가 서로 독립적이지 않기 때문이다. 따라서 FMCW 배열 안테나를 이용하여 표적의 거리-각도 동시추정을 위한 최대우도 기반 알고리즘을 제안하고, 거리와 각도 추정에 있어서 Cramer-Rao bound에 도달함을 보인다.

• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.267-271
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• 2011

I developed an enhanced correction method for Ricean bias which occurs in linear polarization measurement. Two known methods for Ricean bias correction are reviewed. In low signal-to-noise area, the method based on the mode of the equation gives better representation of the fractional polarization. But a caution should be given that the accurate estimation of noise level, i.e. ${\sigma}$ of the polarized flux, is important. The maximum likelihood method is better choice for high signal-to-noise area. I suggest a hybrid method which uses the mode of the equation at the low signal-to-noise area and takes the maximum likelihood method at the high signal-to-noise area. A modified correction coefficient for the mode solution is proposed. The impact on the depolarization measure analysis is discussed.

• ETRI Journal
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• 제30권6호
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• pp.774-782
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• 2008

An operational orbit determination (OD) and prediction system for the geostationary Communication, Ocean, and Meteorological Satellite (COMS) mission requires accurate satellite positioning knowledge to accomplish image navigation registration on the ground. Ranging and tracking data from a single ground station is used for COMS OD in normal operation. However, the orbital longitude of the COMS is so close to that of satellite tracking sites that geometric singularity affects observability. A method to solve the azimuth bias of a single station in singularity is to periodically apply an estimated azimuth bias using the ranging and tracking data of two stations. Velocity increments of a wheel off-loading maneuver which is performed twice a day are fixed by planned values without considering maneuver efficiency during OD. Using only single-station data with the correction of the azimuth bias, OD can achieve three-sigma position accuracy on the order of 1.5 km root-sum-square.

• 대한전자공학회논문지
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• 제19권2호
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• pp.23-30
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• 1982

본 논문에서는 관성 항해 시스뎀(INS) 수직 찬넬의 bias error 감소를 위해 Kalman filter 방법과 재래식 방법이 적용, 비교되어졌다. 이 두가지 방법들은 예측 error와 반응면에서 다른 보통 쓰이는 방법들 보다 더 잘 수행됨을 보였다. 비교 연구 결과에 의하면, Kalman filter 방법 방호이 별무리없이 재래식 방법보다 효과적으로 더 잘 수행됨을 알 수 있다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.670-674
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• 1992

This paper presents a velocity regulation scheme for a DC motor subjected to random torque and velocity measurement noises of white noise type as well as unknown constant load torque (bias). The scheme separately estimates an unknown bias in addition to state estimation by the bias-free Kalman Filter, and reflects the effect of the bias estimate to the armature input voltage such that velocity variations be regulated. It is shown via computer simulations that the performance of the present scheme is superior to that of the conventional analog PI regulator.

• Journal of the Korean Data and Information Science Society
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• 제25권5호
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• pp.1127-1135
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• 2014

Genome-wide association studies (GWAS) are designed to discover genetic variants such as single nucleotide polymorphisms (SNPs) that are associated with human complex traits. Although there is an increasing interest in the application of GWAS methodologies to population-based cohorts, many published GWAS have adopted a case-control design, which raise an issue related to a sampling bias of both case and control samples. Because of unequal selection probabilities between cases and controls, the samples are not representative of the population that they are purported to represent. Therefore, non-random sampling in case-control study can potentially lead to inconsistent and biased estimates of SNP-trait associations. In this paper, we proposed inverse-probability of sampling weights based on disease prevalence to eliminate a case-control sampling bias in estimation and testing for association between SNPs and quantitative traits. We apply the proposed method to a data from the Korea Association Resource project and show that the standard estimators applied to the weighted data yield unbiased estimates.