• 음성과학
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• 제7권2호
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• pp.7-18
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• 2000

The purpose of this study was to investigate the phonological error patterns of korean children with and without specific phonological disorders(SPD). In this study, 29 normally developing children and 10 SPD children were involved. The children were matched the percentage of consonants correct(PCC). 22 picture cards were used to elicit korean consonants in word initial syllable initial, word medial syllable initial, word medial syllable final, word final syllable final positions. The findings were as follows. First, the phonological error patterns of SPD were 1) similar to those of normal children with the same PCC, 2) similar to those of normal children with the lower PCC, or 3) unusual to those of normal children. Second,. korean children showed phonological processes reflecting the korean phonological characteristics: tensification, reduction of the word medial syllable final consonant. This study suggests that both the PCC and error patterns should be considered in assessing phonological abilities of children.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
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• pp.130-134
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• 2001

In the re-entry control system, errors apt to induce because the time derivative of drag acceleration is analytically estimated. Still more, the difficulty of estimation of the exact drag coefficient in hypersonic velocity and the nun-reality of the scale height cause a steady-state drag error. This paper proposes the additional method of the disturbance observer. This reduces the steady-state drag error according to the following series. First, this method estimates a error in drag acceleration time derivative by the analytic calculation and then creates the new drag acceleration time derivative using the estimated error. The performance of the re-entry control system is verified about 32 reference trajectories.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1817-1827
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• 2009

Although human error is recognized as the primary cause of railway accidents and incidents, there have been limitations in finding the root causes of errors and developing effective corrective actions in the Korean railway industry, due to the absence of a systematic method and lack of professional knowledge and skills of investigators. Therefore, there has been a strong need for a systematic methodology for human error analysis. This paper introduces a methodology for analyzing human error m railway operations, called HEAR (Human Error Analysis and Reduction). HEAR is intended to help analysts identify the sequences and various levels of causes of operators' erroneous actions in railway accidents or incidents and make recommendations to eliminate or reduce the future possibility of similar errors and accidents. It was developed based on a thorough investigation of various techniques for human errors analysis and feedback from field investigators.

• 대한인간공학회지
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• 제15권1호
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• pp.27-38
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• 1996

A total of 77 unanticipated trip cases induced by human errors in Korean nuclear power plants were collected from the nuclear power plant trip event reports and analyzed to investigate the areas of high priority for human error reduction. Prior to this analysis, a classification system was made on the four task-related categories including plant systems, work situations, task types, and error types. The erroneous actions affecting the unanticipated plant trips were indentified by reviewing carefully the description of trip events. Then, the events with erroneous action were analyzed by using the classification system. Based on the results for the individual cases, human error occurrences were counted for each of the four categories, also for the selected pairs of categories, to find out the relationships between the two categories in aspects of human errors. As a result, the plant systems, work situations, and task types, and error types which are dominant in human error occurrences were identified.

• Journal of Communications and Networks
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• 제13권5호
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• pp.481-493
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• 2011

Multiple-input multiple-output (MIMO) technology provides high data rate and enhanced quality of service for wireless communications. Since the benefits from MIMO result in a heavy computational load in detectors, the design of low-complexity suboptimum receivers is currently an active area of research. Lattice-reduction-aided detection (LRAD) has been shown to be an effective low-complexity method with near-maximum-likelihood performance. In this paper, we advocate the use of systolic array architectures for MIMO receivers, and in particular we exhibit one of them based on LRAD. The "Lenstra-Lenstra-Lov$\acute{a}$sz (LLL) lattice reduction algorithm" and the ensuing linear detections or successive spatial-interference cancellations can be located in the same array, which is considerably hardware-efficient. Since the conventional form of the LLL algorithm is not immediately suitable for parallel processing, two modified LLL algorithms are considered here for the systolic array. LLL algorithm with full-size reduction-LLL is one of the versions more suitable for parallel processing. Another variant is the all-swap lattice-reduction (ASLR) algorithm for complex-valued lattices, which processes all lattice basis vectors simultaneously within one iteration. Our novel systolic array can operate both algorithms with different external logic controls. In order to simplify the systolic array design, we replace the Lov$\acute{a}$sz condition in the definition of LLL-reduced lattice with the looser Siegel condition. Simulation results show that for LR-aided linear detections, the bit-error-rate performance is still maintained with this relaxation. Comparisons between the two algorithms in terms of bit-error-rate performance, and average field-programmable gate array processing time in the systolic array are made, which shows that ASLR is a better choice for a systolic architecture, especially for systems with a large number of antennas.

• 전기전자학회논문지
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• 제24권4호
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• pp.1028-1033
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• 2020

기존의 동일대역 간섭저감 방법은 무선기기 사이에 물리적인 이격거리를 지정하는 것으로 이격거리를 통해서 간섭을 억제한다. 만약 무선기기에서 동일대역 간섭을 저감할 수 있다면 물리적인 이격거리에 마진을 줄 수 있고, 수신기의 동작영역을 확장시키는 효과가 있으므로 간섭 대응 및 개선에 활용도가 크다. 본 논문에서는 동일대역 아날로그 간섭저감기의 구조를 제안하였고, 제안한 아날로그 간섭저감기의 설계와 구현에 대해서 기술하였다. 아날로그 간섭저감기를 설계하기 위해서 아날로그 간섭저감기의 성능에 영향을 미치는 지연(delay) 불일치, 위상오차 그리고 지연선로의 수에 따른 간섭저감 성능을 시뮬레이션 하였다. 16개의 지연선로로 구성된 아날로그 간섭저감기를 제작하였으며, 구현한 간섭저감기는 3.32㎓의 중심주파수에서 40MHz 대역폭을 갖는 5G(NR-FR1-TM-1.1) 신호에 대해서 약 10dB의 간섭저감 성능을 갖는다. 본 논문에서 제안한 아날로그 간섭저감기는 동일대역 간섭저감기로 활용가능하다.

• 조명전기설비학회논문지
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• 제23권9호
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• pp.83-90
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• 2009

본 논문은 스테레오 영상의 깊이정보특성을 이용하여 물체의 이등성분과 외란광에 의해 오인식되는 이동성분을 구분하여 외란광에 의한 오인식률을 경감하기 위한 방법을 제안한다. 추출된 이동성분으로부터 깊이정보의 변화를 측정, 변화가 미약한 경우 외란광으로 인식하여 이동물체가 없는 것으로 판단하도록 하였다. 실험 결과 외란광에 의한 오인식률과 그림자와 같은 허상에 의한 오인식률이 87.3[%]의 감소를 보여 본 논문에서 제안하는 방법의 유용성을 확인하였다.

• 한국정밀공학회지
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• 제14권3호
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• pp.107-113
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• 1997

This paper presents the active control of a flexible cantilever beam vibration. The cantilever beam was excitied by a steady-state harmonic and white noise point force and the control was performed by one piezo ceramic actuator bonded to the surface of the beam. An adaptive controller based on filtered-x LMS algorithm was used and the controller was defined by minimizing the square of the response of error sensor. In the experiment, gap sensor was used as an error sensor while the sinusoidal or white noise was applied as a disturbance. In the case of sinusoidal input, more than 20 dB of vibration reduction was achieved over all range of the natural frequencies and it takes 5 seconds to control the vibration at first natural frequency and 1 second at other natural frequencies. In the case of white noise input, 7 dB of vibration reduction was achieved at the first natural frequency and good control performance was achieved in the considered whole frequency range. Results indicate that the vibration of a flexible cantilever beam could be controlled effectively when the piezo ceramic actuator was used with filtered-x LMS algorithm.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2197-2204
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• 2015

In recent years, medical image diagnosis has growing significant momentous in the medicinal field. Brain and lung image of patient are distorted with salt and pepper noise is caused by moving the head and chest during scanning process of patients. Reconstruction of these images is a most significant field of diagnostic evaluation and is produced clearly through techniques such as linear or non-linear filtering. However, restored images are produced with smaller amount of noise reduction in the presence of huge magnitude of salt and pepper noises. To eliminate the high density of salt and pepper noises from the reproduction of images, a new efficient fuzzy based median filtering algorithm with a moderate elapsed time is proposed in this paper. Reproduction image results show enhanced performance for the proposed algorithm over other available noise reduction filtering techniques in terms of peak signal -to -noise ratio (PSNR), mean square error (MSE), root mean square error (RMSE), mean absolute error (MAE), image enhancement factor (IMF) and structural similarity (SSIM) value when tested on different medical images like magnetic resonance imaging (MRI) and computer tomography (CT) scan brain image and CT scan lung image. The introduced algorithm is switching filter that recognize the noise pixels and then corrects them by using median filter with fuzzy two-sided π- membership function for extracting the local information.

• 한국정밀공학회지
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• 제13권4호
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• pp.129-135
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• 1996

The area of gear vibration and noise, has recently been the focus of many studies. The proper kinematic and geometric design of gears, the mathematical modeling of gear system are essential for a good design. This work present a gear disign for reducing noise, and practical approaches used for machinery noise reduction slong with the summary of methods available for predicting gear noise in terms of the transmis- sion error, and show a comparative study with other methods. A new tooth profile modification is proposed for reducing vibration and noise of involute gears. The method is based on the use of cubic spline curves. The tooth profile is constrained to assume an involute shape during the loaded operation. Thus the new gear profile assures conjugate motion at all points along the line of action. The new profile is found to result in a more uniform static transmission error compared to not only standard involute profile but also modificated profile therby contributing to the improvement of vibration and noise characteristics of the gear.