• Proceedings of the Korean Information Science Society Conference
• /
• 2005.11a
• /
• pp.721-723
• /
• 2005

본 논문에서는 영상 기반 항해를 위하여 최적의 영상 샘플링을 획득하기 위한 영상 샘플링 알고리즘을 제안한다. 이를 위해 초기 과다 샘플링 된 영상열의 입력으로부터 장면 전역에 걸쳐 적절한 렌더링 품질을 보장하는 최소의 샘플링을 선택하는 감소 샘플링(decremental sampling)의 접근 방법을 기반으로 본 문제를 Set Covering 문제로 공식화한다. 각 시점으로부터 최상의 영상 품질을 보장하는 영역을 3D 와핑 알고리즘을 사용하여 포함 영역으로 표현하여, 이렇게 표현된 Set Covering 문제는 유전 알고리즘을 사용하여 최적화 문제로 설계한다. 실험 결과 본 논문에서 제안한 방법을 통해 최적 해를 구함으로서 만족할 만한 영상 기반 항해의 결과를 얻을 수 있었다.

• The KIPS Transactions:PartD
• /
• v.13D no.3 s.106
• /
• pp.369-376
• /
• 2006

This paper presents a new method of significantly improving conventional Bayesian statistical text classifier by incorporating accelerated EM(Expectation Maximization) algorithm. EM algorithm experiences a slow convergence and performance degrade in its iterative process, especially when real online-textual documents do not follow EM's assumptions. In this study, we propose a new accelerated EM algorithm with uncertainty-based selective sampling, which is simple yet has a fast convergence speed and allow to estimate a more accurate classification model on Naive Bayesian text classifier. Experiments using the popular Reuters-21578 document collection showed that the proposed algorithm effectively improves classification accuracy.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.1
• /
• pp.153-160
• /
• 2022

A greedy algorithm is proposed to select a subset of nodes of a graph for bandlimited graph signals in which each signal value is generated with its weight. Since graph signals are weighted, we seek to minimize the weighted reconstruction error which is formulated by using the QR factorization and derive an analytic result to find iteratively the node minimizing the weighted reconstruction error, leading to a simplified iterative selection process. Experiments show that the proposed method achieves a significant performance gain for graph signals with weights on various graphs as compared with the previous novel selection techniques.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.292-292
• /
• 2015

최근 상수관망의 물 공급 과정에서 여러 가지 원인으로 인해 물의 손실에 따른 비용손실이 발생하고 있다. 급수시스템의 경우에는 파열 및 누수발생과 관련되어 사용되는 비용은 분실되는 물의 직적비용, 급수시스템 수리에 따른 공사비용, 공급중지와 관련된 사회적 비용이 있다. 파열 및 누수를 신속하게 감지하는 것은 물 손실에 의해 발생하는 직접 및 간접비용을 줄일 수 있다. 그러나 국내의 경우 정기적으로 매년 1회 시행되는 상수관로에 대한 누수탐지작업으로 신속한 감지 및 즉각적인 대처를 할 수 없는 실정이다. 본 연구에서는 수도관에서 발생되는 파열 및 누수를 탐지하기 위하여 블록 유입부에 설치된 유량계의 샘플링 간격의 영향에 대한 연구를 실시하였다. 적응칼만필터 알고리즘을 이용한 가변 샘플링 간격은 최대 최소 샘플링 간격과 정규화된 잔차의 상한값과 하한값 도입하여 제시하였다. 샘플링 간격의 효과를 강조하기 위해 사인 곡선, 사다리꼴 파열, 불규칙 잡음으로 구성된 가상의 유량 데이터로 알고리즘에 대한 검증실험을 진행하였고 실험 결과 샘플링 간격이 길수록 긴 시간 동안 누수 및 파열에 대한 작은 잔차를 발생시켰다. 모의실험결과 샘플링 주기를 변경함으로써 분석에 필요한 유량 데이터의 샘플수를 크게 줄일 수 있었다.

• KIPS Transactions on Software and Data Engineering
• /
• v.2 no.1
• /
• pp.27-34
• /
• 2013

Background subtraction is one of the key techniques for automatic video content analysis, especially in the tasks of visual detection and tracking of moving object. In this paper, we present a new sample-based technique for background extraction that provides background image as well as background model. To handle both high-frequency and low-frequency events at the same time, multiple interval background models are adopted. The main innovation concerns the use of a confidence factor to select the best model from the multiple interval background models. To our knowledge, it is the first time that a confidence factor is used for merging several background models in the field of background extraction. Experimental results revealed that our approach based on multiple interval sampling works well in complicated situations containing various speed moving objects with environmental changes.

• KIPS Transactions on Computer and Communication Systems
• /
• v.4 no.1
• /
• pp.15-22
• /
• 2015

Estimating the number of distinct values is really well-known problems in network data measurement and many effective algorithms are suggested. Recent works have built upon technique called Linear Counting to solve the estimation problem for massive sets or spreaders in small memory. Sampling is used to reduce the measurement data, and it is assumed that sampling gives bad effect on the accuracy. In this paper, however, we show that the sampling on multi-set estimation sometimes gives better results for CSE with sampling than for MCSE that examines all the packets without sampling in terms of accuracy and estimation range. To prove this, we presented mathematical analysis, conducted experiment with real data, and compared the results of CSE, MCSE, and CSES.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.10a
• /
• pp.465-469
• /
• 2017

In this paper we propose a human body tracking method for application of smartphones. The conventional human body tracking method is divided into a sensor-based method and a vision-based method. The sensor-based methods have a weakness in that tracking accuracy is low due to cumulative error of position information. The vision-based method has no cumulative error, but it requires reduction of the computational complexity for application of smartphone. In this paper we use the improved HOG algorithm as a human body tracking method for application of smartphone. The improved HOG algorithm is implemented through downsampling and frame sampling. Gaussian pyramid is applied for downsampling, and uniform sampling is applied for frame sampling. We measured the proposed algorithm on two devices, four resolutions, and four frame sampling intervals. We derive the best detection rate among downsampling and frame sampling parameters that can be applied in realtime.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.07b
• /
• pp.844-846
• /
• 2005

본 논문에서는 3차원 모델을 검색하기 위한 형태 기반 기술자를 추출하는 알고리즘을 제안한다. 제안하는 알고리즘은 모델의 기하학적인 특성을 고려하여 레이 캐스팅 샘플링과 구면조화함수를 이용하는 방법이다. 레이 캐스팅 기법은 모델의 외형을 고려한 적응적인 방법으로 샘플링 하여 기술자에 포함되는 형태 정보를 증가시켜 기술자의 식별성을 높인다. 또한 구면조화함수 계수 추출에서는 기하학적인 주파수 특성을 고려하여 적응적인 계수를 추출한다. 이 방법은 검색 성능에 영향을 미치지 않고 기술자를 조밀하고 간결하게 만든다. 최종적으로 두 방법을 결합함으로써 검색 엔진에서 이용 가능한 기술자를 생성한다. 실험 결과에서는 제안된 알고리즘의 성능이 기존 방법에 비해 약 $12.5\%$ 향상 된 것을 확인 할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.1A
• /
• pp.73-81
• /
• 2012

In this paper, we propose a high-speed synchronization method for Digital Radio Mondiale (DRM) receivers. In order to satisfy the high-speed synchronization requirement of DRM receivers, the proposed method eliminate the initial sampling frequency synchronization process in conventional synchronization methods. In the proposed method, sampling frequency tracking is performed after integer frequency synchronization and frame synchronization. Different correlation algorithms are applied to detect the first frame of the Orthogonal Frequency Division Multiplexing (OFDM) demodulation symbol with sampling frequency offset (SFO). A frame detection algorithm that is robust to SFO is selected based on the performance analysis and simulation. Simulation results show that the proposed method reduces the time spent for initial sampling frequency synchronization even if SFO is present in the DRM signal. In addition, it is verify that inter-cell differential correlation used between reference cells is roubst to the effect of initial SFO.

• Journal of Advanced Navigation Technology
• /
• v.24 no.4
• /
• pp.322-327
• /
• 2020

Recently, a research on obtaining a vital signal using a Doppler radar has been developed and is used as a technology applied to patients in bed. However, in the case of the measured pulse, the respiration signal is generated as noise, resulting in a problem of lowering accuracy. In this paper, we propose a bio-signal measurement algorithm based on the sampling point to improve the accuracy of the signal for measuring the pulse rate when measuring bio-signals using a Doppler radar. The proposed algorithm improves the accuracy of the measured bio-signal by removing noise generated when measuring biosignals based on two sampling points. Compared with actual medical equipment and existing bio-signal algorithms, it is more than 90% similar to medical equipment. In addition, it was confirmed that severe amplitude change was minimized compared to the existing algorithm.