• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.145-155
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• 2015

Noise reduction has been actively studied in the digital image processing and recently, block-based denoising algorithms are widely used. In particular, a low rank approximation employing WNNM(Weighted Nuclear Norm Minimization) and block-based approaches demonstrated the potential for effective noise reduction. However, the algorithm based on low rank a approximation generates the artifacts in the image restoration step. In this paper, we analyzes the image content using the STFT(Short Time Fourier Transform) and proposes an effective method of minimizing the artifacts generated from the conventional algorithm. To evaluate the performance of the proposed scheme, we use the test images containing a wide range of noise levels and compare the results with the state-of-art algorithms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1373-1379
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• 2007

A modified adaptive switching median filter for impulse noise removal, which has the noise detection step and the noise filtering step, is proposed in this paper. In the noise detection step, we use the detection threshold which is earned by calculating the intensity differences between pixels nearby with each other in localized window, to determine whether the pixels in the image are noise or not. Then in the noise filtering step, we will only remove the corrupted pixels and remain the good pixels. By the noise detection result, we can easily get the local noise density of the image, and use it to consider the filtering mask size and the times of filtering iteration according to different localized noise corruptions. For Setting the simulation result, we compared the proposed method to conventional median filters with several test images corrupted by various impulse noise densities. We also use the peak signal-to-noise ratio (PSNR) to evaluate restoration performance, the simulation results demonstrate that the proposed method shows better results than other median-based type filters.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1650-1657
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• 2007

In this paper, we propose an Overlapped Block and an Hanning Window to prevent a Block Discontinuity when we use an algorithm to eliminate ringing artifact which is based on a block structure. The algorithm to eliminate ringing artifact operates with a block structure and 24-RGB data and is based on a modified K-means algorithm. The proposed overlapped block method is piled up one on another per an half of the size of unit-block when an input image is split into several unit-blocks. Therefore, we define a data unit as the unit-block of the block size, $16{\times}16$ pixels. We reconstruct the processed data units into the original form of input image by using an isotropic form of Hanning Window. Finally, in order to evaluate the performance of the abovementioned algorithms, we compare three image, an input image with ringing artifact, an image result obtained by conventional method (non-overlapped), and an image result obtained the proposed method.

• Korean Journal of Remote Sensing
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• v.18 no.6
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• pp.359-367
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• 2002

In this paper, a new embedded wavelet packet image coder algorithm is proposed for an effective image coder using correlation between partitioned coefficients. This new algorithm presents parent-child relationship for reducing image reconstruction error using relations between individual frequency sub-bands. By parent-child relationship, every coefficient is partitioned and encoded for the zerotree data structure. It is shown that the proposed wavelet packet image coder algorithm achieves low bit rates and rate-distortion. It also demonstrates higher PSNR under the same bit rate and an improvement in image compression time. The perfect rate control is compared with the conventional method. These results show that the encoding and decoding processes of the proposed coder are simpler and more accurate than the conventional ones for texture images that include many mid and high-frequency elements such as aerial and satellite photograph images. The experimental results imply the possibility that the proposed method can be applied to real-time vision system, on-line image processing and image fusion which require smaller file size and better resolution.

• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.543-548
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• 2019

The tonal signal caused by the machinery component of a vessel such as an engine, gearbox, and support elements, can be modeled as a sparse signal in the frequency domain. Recently, compressive sensing based techniques that recover an original signal using a small number of measurements in a short period of time, have been applied for the tonal frequency detection. These techniques, however, cannot avoid a basis mismatch error caused by the discretization of the frequency domain. In this paper, we propose a method to detect the tonal frequency with a small number of measurements in the continuous domain by using the atomic norm minimization technique. From the simulation results, we demonstrate that the proposed technique outperforms conventional methods in terms of the exact recovery ratio and mean square error.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.19-19
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• 2016

오늘날, 보다 정밀한 대기기상 분석과 정확한 기상 예측을 위해 보편적으로 기상레이더를 활용하고 있다. 지표면과 가까운 저층에서 주로 발생하는 국지성 호우 및 돌발기상에 대한 대응을 위해서는 기상레이더 역시 저층 관측이 수반되어야 한다. 하지만, 국토 대부분이 산악지형으로 이루어진 우리나라에서는 산악지형에 의한 지형클러터와 빔 차폐의 영향을 피하여 원만한 기상관측을 위해 대부분의 기상레이더가 고지대에 설치, 운영되고 있다. 그럼에도 불구하고 낮은 고도각의 레이더 관측 자료에서는 여전히 지형 클러터 및 차폐에 따른 영향으로 인해 자료 품질의 신뢰성이 떨어질 수 밖에 없다. 현재 클러터나 차폐가 발생한 영역에 대해 상위 고도각의 자료를 이용하는 등의 방법으로 보정을 수행하고 있지만 각 고도각 관측 자료들의 시간적 차이가 발생함에 따라 부정확성이 발생할 수 있다는 단점이 있다. 따라서 본 논문에서는 차폐 영역 보정에 대한 처리를 위해 단일 관측자료 만을 이용하는 방법을 적용함으로서 시간적 불일치성에 대한 문제를 해결하고, 초단기 강수예측을 위한 강수에코의 정확한 추적을 위해 레이더 영상에 적응적인 차폐, 클러터 보정 기법을 제안한다. 제안 기법은 강수에코의 형태학적 구조에 기반한 차폐보정을 위해 영상 처리 기법의 한 종류인 모폴로지 기법을 적용함으로써 강수에코의 모양, 크기, 및 구조에 따라 침식 및 팽창 과정을 수행하여 클러터나 차폐로 인해 소실된 강수에코 영역을 보정한다. 실험결과 레이더 강수추정의 정확성 향상을 꾀할 수 있었으며, 강수 추적을 위한 강수에코의 형태학적 복원이 가능함을 확인하였다. 이로부터, 향후 저층관측 레이더 자료의 활용성 증대와 에코 형태에 기반한 강수 추적 알고리즘 개발 및 성능 향상에 활용될 수 있을 것으로 기대한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.454-454
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• 2016

하천의 치수안정성 확보 및 수심유지, 생태복원 등과 같은 다양한 요구를 충족하기 위한 보의 성능 개선에 대한 연구가 필요하며, 계단형 보는 재료에 의한 폭기효과 및 서식처 효과 등의 환경적요소를 내포하고 있다. 기존 연구는 표면류 흐름특성을 검증하고 유량변화에 따른 하류단 도수발생위치 변화를 분석하는 등 계단형 보에 대해 수리특성을 정량화한 연구가 대부분이며 흐름변화에 따른 유속장에 관한 연구는 미흡한 실정이다. 따라서 본 연구는 기능성 친환경 횡단 구조물 유형 중 하나인 계단형 보의 안정성 검토를 위한 수리적 특성을 분석하고자 함으로써 구조물 안정성에 영향을 줄 수 있는 자체 및 하류 보호공 주변의 유속 분석을 통한 흐름 특성을 검토하고 설계시 외력 고려를 위한 자료를 제공하기 위한 목적이 있다. 이를 위해 계단형 보모형에 대해 수리모형실험을 수행하였다. 폭 0.24 m, 총 길이 3.70 m, 높이 0.30 m인 순환실험수로를 이용하였으며, 계단형 보 모형은 5단으로 단 높이 2 cm와 단 길이 5 cm이며, 보 높이는 10 cm, 보 길이는 25 cm 모형으로 실험하였다. 하류에 전도식 게이트를 설치하여 하류 수위를 증가시키면서 보 하류부에서 발생하는 완전도수부터 하류수심이 보 높이를 초과하는 잠김흐름 조건에 대해 실험하였다. 측정기법은 입자영상측정계(Particle Image Velocimetry; PIV)를 이용하였으며, 상류영역부터 하류영역에 대해 보 주변 흐름의 순간적 유속분포를 확인하였다. 또한 측정된 전반적 흐름 양상에 대해 통계적 수리분석을 수행하였다. 흐름특성에 대한 연구는 향후 계단형 보의 물받이 길이 및 보의 적정 규모 설계시 중요한 자료가 될 것으로 기대한다.

• Journal of the Korea Society of Computer and Information
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• v.26 no.10
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• pp.1-7
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• 2021

Recently, since most of the research on correcting speech recognition errors is based on English, there is not enough research on Korean speech recognition. Compared to English speech recognition, however, Korean speech recognition has many errors due to the linguistic characteristics of Korean language, such as Korean Fortis and Korean Liaison, thus research on Korean speech recognition is needed. Furthermore, earlier works primarily focused on editorial distance algorithms and syllable restoration rules, making it difficult to correct the error types of Korean Fortis and Korean Liaison. In this paper, we propose a context-sensitive post-processing model of speech recognition using a LSTM-based sequence-to-sequence model and Bahdanau attention mechanism to correct Korean speech recognition errors caused by the pronunciation. Experiments showed that by using the model, the speech recognition performance was improved from 64% to 77% for Fortis, 74% to 90% for Liaison, and from 69% to 84% for average recognition than before. Based on the results, it seems possible to apply the proposed model to real-world applications based on speech recognition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.661-669
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• 2021

A mechanical stiffener has been mainly applied on a PCB to secure fatigue life of a solder joint of an electronic components in spaceborne electronics by minimizing bending displacement of the PCB. However, it causes an increase of mass and volume of the electronics. The high damping PCB implemented by multi-layered viscoelastic tapes of a previous research was effective for assuring the fatigue life of the solder joint, but it also has a limitation to decrease accommodation efficiency for the components on the PCB. In this study, we proposed high damping PCB with a multi-layered superelastic shape memory alloy stiffener for spatialminimized, light-weighted, high-integrated structure design of the electronics. To investigate the basic characteristics of the proposed PCB, a static load test, a free vibration test were performed. Then, the high damping characteristic and the design effectiveness of the PCB were validated through a random vibration test.

• Journal of the Korea Fashion and Costume Design Association
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• v.21 no.1
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• pp.181-189
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• 2019

The washability, redeposition, fill power, and fabric damage of wet cleaning and dry cleaning solvents were measured to identify the optimal type of washing that would increase washability while maintaining dimensional stability. The soiled fabric is a polyester cotton blend and the types of soil were wine, blood, make-up and sebum with carbon black. Petroleum and silicone solvents were used in dry cleaning. Results from this study are as follows. First, detergency is significantly influenced by the type of washing and type of soil. Wet cleaning is superior to dry cleaning. Wet cleaning shows a strong washing performance against hydrophilic soils, whereas, dry cleaning is stronger against hydrophobic soils. Second, redeposition is significantly affected by the type of washing, fabrics, and soils. Redeposition occurred little on cotton during wet cleaning, but showed a high rate for nylon. However, when the two types of fabric were dry cleaned, redeposition occurred on both types. Third, the fill power of duck-down is very affected by the type of washing. Resilience is the best in wet cleaning; and in dry cleaning, petroleum solvents showed a higher resilience when as compared to silicone solvents. Last, the level of fabric damage to cotton fabrics is highly influenced by the type of washing. Wet cleaning damages cotton fabrics significantly more than dry cleaning. For dry cleaning, petroleum solvents damage these fabrics slightly more than silicone solvents. In conclusion, the type of soil must initially be identified to determine the optimal type of washing. Special caution is required when textiles with particulate soil and nylon are washed. When considering the resilience of duck-down clothing, wet cleaning is more appropriate than dry cleaning. Dry cleaning, especially when using silicone-based solvents, is more suitable than wet cleaning for maintaining the shape of clothing.