• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.109-113
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• 2007

The COMS provides the LRIT/HRIT services to users. The COMS LRIT/HRIT broadcast service should satisfy the 15 minutes timeliness requirement. The requirement is important and critical enough to impact overall performance of the LHGS. HRIT image data is acquired from INRSM output receiving but LRIT image data is generated by sub-sampling HRIT image data in the LHGS. Specially, since LRIT is acquired from sub-sampled HRIT image data, LRIT processing spent more time. Besides, some of data loss for LRIT occurs since LRIT is compressed by lossy JPEG. Therefore, algorithm with the fastest processing speed and simplicity to be implemented should be selected to satisfy the requirement. Investigated sub-sampling algorithm for the LHGS were nearest neighbour algorithm, bilinear algorithm and bicubic algorithm. Nearest neighbour algorithm is selected for COMS LHGS considering the speed, simplicity and anti-aliasing corresponding to the guideline of user (KMA: Korea Meteorological Administration) to maintain the most cloud itself information in a view of meteorology. But the nearest neighbour algorithm is known as the worst performance. Therefore, it is studied in this paper that the selection of nearest neighbour algorithm for the LHGS is reasonable. First of all, characteristic of 3 sub-sampling algorithms is studied and compared. Then, several sub-sampling algorithm were applied to MTSAT-1R image data corresponding to COMS HRIT. Also, resized image was acquired from sub-sampled image with the identical sub-sampling algorithms applied to sub-sampling from HRIT to LRIT. And the difference between original image and resized image is compared. Besides, PSNR and MSE are calculated for each algorithm. This paper shows that it is appropriate to select nearest neighbour algorithm for COMS LHGS since sub-sampled image by nearest neighbour algorithm is little difference with that of other algorithms in quality performance from PSNR.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.541-547
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• 1992

The phased array antenna has the ability to perform adaptive sampling by directing the radar beam without inertia in any direction. The adaptive sampling capability of the phased array antenna allows each sampling time interval to be varied for each target, depending on the acceleration of each target at any time. In this paper we design a three-dimensional adaptive tracking algorithm for the phased array radar system with a given set of measurement parameters. The tracking algorithm avoids taking unnecessarily frequent samples, while keeping the angular prediction error within a fraction of antenna beamwidth so that the probability of detection will not be degraded during a track update illuminations. In our algorithm, the target model and the sampling rate are selected depending on the target range and the target maneuver status which is determined by a maneuver detector. A detailed simulation is conducted to test the validity of our tracking algorithm for encounter geometries under various conditions of maneuver.

• Journal of Power Electronics
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• 제16권6호
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• pp.2212-2220
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• 2016

Based on the conventional PID algorithm and the adaptive PID (AD-PID) algorithm, a separate sampling adaptive PID (SSA-PID) algorithm is proposed to improve the transient response of digitally controlled DC-DC converters. The SSA-PID algorithm, which can be divided into an oversampled adaptive P (AD-P) control and an adaptive ID (AD-ID) control, adopts a higher sampling frequency for AD-P control and a conventional sampling frequency for AD-ID control. In addition, it can also adaptively adjust the PID parameters (i.e. $K_p$, $K_i$ and $K_d$) based on the system state. Simulation results show that the proposed algorithm has better line transient and load transient responses than the conventional PID and AD-PID algorithms. Compared with the conventional PID and AD-PID algorithms, the experimental results based on a FPGA indicate that the recovery time of the SSA-PID algorithm is reduced by 80% and 67% separately, and that overshoot is decreased by 33% and 12% for a 700mA load step. Moreover, the SSA-PID algorithm can achieve zero overshoot during startup.

• 전자공학회논문지B
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• 제30B권5호
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• pp.62-72
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• 1993

The phased array antenna has the ability to perform adaptive sampling by directing the radar beam without inertia in any direction. The adaptive sampling capability of the phased array antenna allows each sampling time interval to be varied for each target, depending on the acceleration of each target at any time. In this paper we design a three dimensional adaptive target tracking algorithm for the phased array radar system with a given set of measurement parameters. The tracking algorithm avoids taking unnecessarily frequent samples, while keeping the angular prediction error within a fraction of antenna beamwidth so that the probability of detection will not be degraded during a track updata illuminations. In our algorithm, the target model and the sampling rate are selected depending on the target range and the target maneuver status which is determined by a maneuver level detector. A detailed simulation is conducted to test the validity of our tracking algorithm for target trajectories under various conditions of maneuver.

• Journal of the Korean Statistical Society
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• 제35권2호
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• pp.157-166
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• 2006

This research proposes an efficient Monte Carlo algorithm for computing error probability in high performance digital communication st stems. It characterizes special features of the problem and suggests an importance sampling algorithm specially designed to handle the problem. It uses a shifted exponential density as the importance sampling density, and shows an adaptive way of choosing the rate and the origin of the shifted exponential density. Instead of equal allocation, an intelligent allocation of the samples is proposed so that more samples are allocated to more important part of the error probability. The algorithm uses the nested feature of the error space and avoids redundancy in estimating the probability. The algorithm is applied to an example data set and shows a great improvement in accuracy of the error probability estimation.

• 대한기계학회논문집A
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• 제30권9호
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• pp.1116-1123
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• 2006

In this study, the effective method for reliability estimation is proposed using tow-staged kriging metamodel and genetic algorithm. Kriging metamodel can be determined by appropriate sampling range and the number of sampling points. The first kriging metamodel is made based on the proposed sampling points. The advanced f'=rst order reliability method is applied to the first kriging metamodel to determine the reliability and most probable failure point(MPFP) approximately. Then, the second kriging metamodel is constructed using additional sampling points near the MPFP. These points are selected using genetic algorithm that have the maximum mean squared error. The Monte-Carlo simulation is applied to the second kriging metamodel to estimate the reliability. The proposed method is applied to numerical examples and the results are almost equal to the reference reliability.

• 한국위성정보통신학회논문지
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• 제10권3호
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• pp.57-61
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• 2015

본 논문에서는 3D 방송의 기본적인 원리를 설명하고 실감영상 CS 기술을 적용하여 데이터 용량을 줄이는 방식을 제안한다. 샘플링 이론과 CS 기술의 차이점을 설명하고 개념과 동작원리를 설명한다. 압축 센싱의 복원 알고리즘인 SS-CoSaMP(Single-Space Compressive Sampling Matched Pursuit) 와 AMP(Approximate Message Passing)를 소개하고 이를 이용하여 이미지 데이터를 압축 복원하여 비교한다. 계산시간을 비교하여 낮은 복잡도를 갖는 알고리즘을 판단한다.

• 한국통신학회논문지
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• 제30권11A호
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• pp.1004-1011
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• 2005

OFDM(Orthogonal Frequency Division Multiplexing) 시스템에서는 수신단의 샘플링 주파수가 정확하지 않을 경우 샘플링 주파수 옵셋으로 인한 ICI (Inter-Carrier Interference) 현상이 발생하여 수신 성능의 열화를 초래한다. 일반적으로 샘플링 주파수 옵셋의 추정은 연속된 2개의 OFDM 심볼의 파일럿 신호 또는 약속된 신호간의 상관을 통하여 수행되는데, 이 경우 전송 효율 저하 및 OFDM 시스템의 규격에 따라 적음이 불가능할 수 있다는 단점을 가진다. 본 논문에서는 이러한 문제점을 해결하기 위해 단일 OFDM 심볼을 이용한 새로운 샘플링 주파수 옵셋추정 기법을 제안한다. 제안된 방식은 단일 OFDM 심볼을 이용하므로 전송 효율의 저하 없이 보다 유연하게 OFDM 기반 시스템 규격에 적용 가능하며, 기존의 주파수 영역에서 샘플링 주파수 옵셋을 추정하는 기법보다 더 많은 관찰을 통한 샘플링 주파수 옵셋 추정의 신뢰성을 증가시킬 수 있다. 제안된 방식의 성능을 다양한 모의 실험을 통해 기존의 기법과 비교 분석하였으며 이를 통하여 제안된 기법 적용한 경우 AWGN 채널 및 페이딩 채널환경에서 샘플링 옵셋 추정 및 보상을 통해 시스템의 성능을 크게 향상시킬 수 있음을 확인하였다.

• 전자공학회논문지CI
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• 제45권3호
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• pp.15-21
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• 2008

본 논문은 2단 샘플링을 통해 정확도는 줄지만 신속하게 연관규칙을 추출하는 새로운 마이닝 알고리즘을 제안한다. 직전 연구인 FAST(Finding Association by Sampling Technique) 기법은 빈발1항목만 최적샘플 형성과정에 적용하여 빈발2항목 및 그이상의 빈발항목을 샘플 추출에 반영하지 못하였다. 이 논문은 그러한 약점을 보완하여 트리밍 과정에서 손실항목과 오류항목의 비중을 동시에 고려하여 다수 빈발항목에 대한 마이닝의 정확성을 높였다. 대표적인 데이터 세트를 써서 실험한 결과 이전연구와 비교해서 동일한 품질하에서 새 알고리즘의 정확도가 향상됨을 확인하였다.

• Journal of Communications and Networks
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• 제17권5호
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• pp.517-524
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• 2015

The fast and accurate spectrum sensing over an ultra-wide bandwidth is a big challenge for the radio environment cognition. Considering sparse signal feature, two novel compressed sensing schemes are proposed, which can reduce compressed sampling rate in contrast to the traditional scheme. One algorithm is dynamically adjusting compression ratio based on modulation recognition and identification of symbol rate, which can reduce compression ratio. Furthermore, without priori information of the modulation and symbol rate, another improved algorithm is proposed with the application potential in practice, which does not need to reconstruct the signals. The improved algorithm is divided into two stages, which are the approaching stage and the monitoring stage. The overall sampling rate can be dramatically reduced without the performance deterioration of the spectrum detection compared to the conventional static compressed sampling rate algorithm. Numerous results show that the proposed compressed sensing technique can reduce sampling rate by 35%, with an acceptable detection probability over 0.9.