• 한국초등수학교육학회지
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• 제24권1호
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• pp.53-87
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• 2020

본 연구는 초등학교 수학에서의 계산어림활동을 고찰함으로써 계산어림지도를 위한 개선방향을 모색하고자 2015 개정 초등학교 수학과 교육과정과 그에 따른 수학교과서 및 교사용지도서에 포함된 계산어림 관련 내용을 살펴보았다. 이를 통해서 전학년군에 걸쳐서 계산어림을 강조할 필요가 있으며, 계산어림의 효과적인 지도를 위해서 계산어림하기, 어림과정설명하기, 어림값과 계산값 비교를 통한 계산결과의 타당성 검증하기 등을 체계적으로 지도하는 것이 필요하며, 연산관련단원에서 계산어림관련 활동을 좀 더 강화하는 것이 필요하다는 것을 알 수 있었다.

• Journal of information and communication convergence engineering
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• 제12권1호
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• pp.53-59
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• 2014

Motion estimation is a core part of most video compression systems since it directly affects the output video quality and the encoding time. The full search (FS) technique gives the highest visual quality but has the problem of a significant computational load. To solve this problem, we present in this paper a modified median (MMED) operation and advanced search strategies for fast motion estimation. The proposed MMED operation includes a temporally co-located motion vector (MV) to select an appropriate initial candidate. Moreover, we introduce a search procedure that reduces the number of thresholds and simplifies the early termination conditions for the determination of a final MV. The experimental results show that the proposed approach achieves substantial speedup compared with the conventional methods including the motion vector field adaptive search technique (MVFAST) and predictive MVFAST (PMVFAST). The proposed algorithm also improves the PSNR values by increasing the correlation between the MVs, compared with the FS method.

• International Journal of Aeronautical and Space Sciences
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• 제11권4호
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• pp.326-337
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• 2010

This work addresses problems regarding trajectory planning for unmanned aerial vehicle sensors. Such sensors are used for taking measurements of large nonlinear systems. The sensor investigations presented here entails methods for improving estimations and predictions of large nonlinear systems. Thoroughly understanding the global system state typically requires probabilistic state estimation. Thus, in order to meet this requirement, the goal is to find trajectories such that the measurements along each trajectory minimize the expected error of the predicted state of the system. The considerable nonlinearity of the dynamics governing these systems necessitates the use of computationally costly Monte-Carlo estimation techniques, which are needed to update the state distribution over time. This computational burden renders planning to be infeasible since the search process must calculate the covariance of the posterior state estimate for each candidate path. To resolve this challenge, this work proposes to replace the computationally intensive numerical prediction process with an approximate covariance dynamics model learned using a nonlinear time-series regression. The use of autoregressive time-series featuring a regularized least squares algorithm facilitates the learning of accurate and efficient parametric models. The learned covariance dynamics are demonstrated to outperform other approximation strategies, such as linearization and partial ensemble propagation, when used for trajectory optimization, in terms of accuracy and speed, with examples of simplified weather forecasting.

• 대한수학교육학회지:수학교육학연구
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• 제8권1호
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• pp.251-568
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• 1998

It is the purpose of this study that is to examine the practice and awareness on the use of calculator and to find the method to utilize the calculator as the tool in elementary school mathematics. Recently, it is recommendes strongly to use technical tools such as calculator and computer for the quiltative development on mathematics education. But we prohibite the usage of calculator and do not have the policy to use the calculator in our country because we have little understanding about it. The following direction for educational development is focused not on the repeat learning through the written computation, but on the ability for students to choose an operator and to perform the task with their own objects and strategies. By using the calculator, We can do the followings : 1)to help the mathematical concept develop, 2)to expand the computational ability from written computation to both mental computation and computational estimation, 3)to use the practical value in the problem situation, 4)to reinforce the problem solving, 5)to obtain the interest and the confedence on mathematics. Therefore, we must endevor actively for the broad usage of calculator in the mathematics class.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.25-25
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• 2023

The ensemble optimal interpolation (EnOI) scheme is a sub-optimal alternative to the ensemble Kalman filter (EnKF) with a reduced computational demand making it potentially more suitable for operational applications. Since only one model is integrated forward instead of an ensemble of model realizations, online estimation of the background error covariance matrix is not possible in the EnOI scheme. In this study, we investigate two Gaussian noise based ensemble generation strategies to produce dynamic covariance matrices for assimilation of water level observations into a distributed hydrological model. In the first approach, spatially correlated noise, sampled from a normal distribution with a fixed fractional error parameter (which controls its standard deviation), is added to the model forecast state vector to prepare the ensembles. In the second method, we use an adaptive error estimation technique based on the innovation diagnostics to estimate this error parameter within the assimilation framework. The results from a real and a set of synthetic experiments indicate that the EnOI scheme can provide better results when an optimal EnKF is not identified, but performs worse than the ensemble filter when the true error characteristics are known. Furthermore, while the adaptive approach is able to reduce the sensitivity to the fractional error parameter affecting the first (non-adaptive) approach, results are usually worse at ungauged locations with the former.

• Journal of applied mathematics & informatics
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• 제41권6호
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• pp.1377-1391
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• 2023

When sensitive topics such as gambling habits, drug addiction, alcoholism, tax evasion tendencies, induced abortions, drunk driving, past criminal involvement, and homosexuality are the focus of open or direct surveys, it becomes challenging to obtain accurate information due to nonresponse bias and response bias. People often hesitate to provide truthful answers. Warner introduced an ingenious method to address this issue. In this study, a new and unrelated randomized response model is proposed to eliminate misleading responses and nonresponses caused by the stigma associated with the attribute being investigated. The proposed randomized response model allows for the estimation of the population percentage with the sensitive characteristic in an unbiased manner. The characteristics and recommendations of the proposed randomized response model are examined, and numerical examples are provided to support the findings of this study.

• 전자공학회논문지
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• 제51권12호
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• pp.150-159
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• 2014

최신 영상 압축 표준 방식인 HEVC는 H.264/AVC에 비해 압축 효율을 크게 개선시킬 수 있지만, 부호화기 복잡도 또한 크게 증가한다. 특히 비정수 정밀도 움직임 보상에 사용되는 보간 필터의 길이가 종래 6-tap에서 8-tap으로 증가함으로 인해, 비정수 정밀도 움직임 추정에 많은 연산량이 요구된다. 본 논문에서는 HEVC의 비정수 움직임 추정 과정에 대한 압축 효율 기여도 및 복잡도를 분석하고, 이로부터 부호화기의 복잡도를 효과적으로 감소시키기 위한 방법을 제안한다. 먼저, 움직임 추정과 움직임 보상에 사용되는 보간 필터를 분리하고, 움직임 추정만을 위한 최적 필터 길이를 찾는다. 또한 최적 비정수 움직임 벡터를 찾기 위한 탐색 과정에서 특정 조건을 만족하는 일부 후보들만을 검사하고, 꼭 필요한 보간 과정만을 수행하도록 함으로써 부호화 복잡도를 감소시킨다. 실험 결과, 제안한 방법을 사용하면 평균 압축 성능 하락 폭 0.7%, 1.5%, 2.5%에서 부호화기 복잡도를 각각 13.6%, 18.5%, 21.1% 감소시킬 수 있었다. 또한 고해상도 영상($1920{\times}1080$)의 경우 압축 성능 하락 폭이 0.4%, 1.1%, 1.6%로 감소함으로써 제안한 방법이 고해상도 영상에 더욱 효과적임을 보였다.