• ETRI Journal
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• v.35 no.5
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• pp.935-938
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• 2013

This letter presents an algorithm for selecting a low delay for the modified discrete cosine transform (MDCT) and inverse MDCT (IMDCT). The implementation of conventional MDCT and IMDCT requires a 50% overlap-add (OLA) for a perfect reconstruction. In the OLA process, an algorithmic delay in the frame length is employed. A reduced overlap window and MDCT/IMDCT phase shifting is used to reduce the algorithmic delay. The performance of the proposed algorithm is evaluated by applying the low-delay MDCT to the G.729.1 speech codec.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.5
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• pp.294-304
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• 2019

This study evaluates the variation characteristics of wave fields (transmission ratio, wave height, time-averaged velocity and time-averaged turbulent kinetic energy) for two-dimensional low-crested structure by olaFlow model based on the two-phases flow numerically. In addition, the present numerical results are verified by comparing with the existing experimental results. The time-averaged velocity, one of various numerical results is formed counterclockwise circulating cell on the front of structure and is occurred strong uni-directional flow on onshore side. It is shown that these are closely related to the factors such as overtopping, etc.

• Communications for Statistical Applications and Methods
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• v.16 no.6
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• pp.1037-1046
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• 2009

Copy number variations(CNVs) are known as one of the most important factors in susceptibility to genetic disorders because they affect expression levels of genes. In previous studies, pyrosequencing, mini-sequencing real-time polymerase chain reaction(PCR), invader assays and other techniques have been used to detect CNVs. However, the higher the copy number in a genome, the more difficult it is to resolve the copies, so a more accurate method for measuring CNVs and assigning genotype is needed. PCR followed by a quantitative oligonucleotide ligation assay(qOLA) was developed for quantifying CNVs. The aim of this study was to compare the two methods for detecting and quantifying the CNVs of duplicated gene: the published pyrosequencing assay(pyro_CNV) and the newly developed qOLA_CNV. The accuracy and precision of the assay were evaluated for porcine KIT, which was selected as a model locus. Overall, the root mean squares(RMSs) of bias and standard deviation of qOLA_CNV were 2.09 and 0.45, respectively. These values are less than half of those of pyro CNV.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.2
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• pp.39-50
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• 2018

In this study, the nonlinear interaction of irregular waves with wave breaking and currents around permeable submerged breakwater was investigated with the aid of olaFlow model which is open source CFD software published under the GPL license. The irregular wave performance of olaFlow applied in this study was verified by comparing and evaluating the target frequency spectrum and the generated frequency spectrum for applicability to irregular waves. Based on the applicability of this numerical model to irregular wave fields, in the coexistence fields of irregular waves and currents, the characteristics of wave height, frequency spectrum, breaking waves, averaged velocity and turbulent kinetic energy around porous submerged breakwater with the respect to the beach type and current direction versus wave propagation were carefully investigated. The numerical results revealed that the shape of wave breaking on the crown of the submerged breakwater and the formation of the mean flow velocity around the structure depend greatly on the current directions and the type of the beach. In addition, it was found that the wave height fluctuation due to the current direction with respect to the wave propagation is closely related to the turbulent kinetic energy.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.4
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• pp.166-179
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• 2018

This study aims at numerically investigating the water-surface characteristics such as wave height distribution depending on the current direction around the three-dimensional permeable submerged breakwaters in wave-current coexisting field which has not been considered in detail so far. In addition, the characteristics of the velocity field including the average flow velocity, longshore current and turbulent kinetic energy, which act as the main external forces of formation of salient, are also examined. For numerical analysis, olaFlow which is open source code of CFD was used and the numerical tests included different types of target waves, both regular waves and irregular waves. Numerical results indicated that wave height variation with wave following or opposing a current behind the submerged breakwater is closely related to turbulent kinetic energy. Furthermore, it was found that weaker longshore currents are formed under wave-current coexisting field compared to the non-current conditions, and transport flow is attenuated. As a result, it was possible to understand the influence of current existence and direction (following and opposing) on the formation of the salient formed behind the submerged breakwaters.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.17-20
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• 1999

본 논문에서는 중첩 가산 Sinusoidal 합성방식에서 위상계승에 의한 단위음 연결법과 다프레임간 정현파 크기의 보간법을 제안한다. 그리고 합성 프레임의 중심이 pitch onset time이라고 가정하고, 음성에서 분리한 성도 모델의 위상을 음성 전체의 위상으로 사용하는 방법을 제안한다. 제안한 방법으로 문서-음성 변환 시스템 (Text-to-Speech System, TTS System)을 구현한 결과 단위음 연결시 연결부분의 파형 왜곡이 감소함을 알 수 있었고, 부드럽게 연결된 합성음을 얻을 수 있었다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.11-14
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• 1999

본 논문에서는 중첩가산 Sinusoidal 합성방식에서 매칭된 정현파별로 위상을 계승하는 단위음성 연결방법을 제안한다. 선행 단위음의 마지막 프레임, 후행 단위음의 첫 프레임, 후행 단위음의 나머지 프레임의 단계로 나누어 각 단계마다 제안한 방식으로 선행 프레임의 위상을 계승하였다. 실험결과 후행 단위음의 연결 위치를 이동하는 기존의 방식을 사용한 연결음에 비해 연결부분에서 음성파형의 급격한 변화가 줄었다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.339-343
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• 1998

Sinusoidal model 은 음성신호처리의 넓은 분야에 적용되고 있는 방법으로 고음질의 합성음을 생성해 낼 수 있고, 조작이 용이하다는 장점을 가지고 있다. 본 논문에서는 Analysis-by-synthesis/Overlap-add Sinusoidal model 이라는 방법을 이용하여 시간축 변환과 dam성 변환을 수행하였다. 특히 본 논문에서는 음질향상을 위하여 시간축 변환시에는 정적인 구간과 변화하는 구간을 구별하여 서로 다른 시간축 변환비를 이용하였고, 기존의 LPC 방법에 비해 스펙트럼 포락선을 보다 잘 추정하는 Improved Cepstrum을 이용하여 음정변환에 적용하였다. 또 서로 다른 문맥에서 얻어진 음성단위들을 결합할 때 생기는 위상차이를 극복하기 위하여, 기본주파수 성분이 일치하도록 시간축을 이동하여 합성하였다. 실험결과 본 논문에서 적용한 방법들을 통해 기존 방식에 비해 개선된 음질을 얻을 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.281-281
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• 2019

수리모형실험은 수로 내에서 장시간 파랑을 발생시킬 경우, 수로 내에 반사 파랑의 성분이 누적될 수 있어 상당한 계측 오차를 발생시킬 우려가 있어 수리모형실험 결과의 검증이 필요하다. 일반적으로 수리모형실험 결과의 검증을 위해서는 동일 실험을 무수히 반복하여 불확실성을 제거하거나 다양한 수리실험실에서 수리모형실험을 수행하고 결과를 분석하여 불확실성을 제거할 수 있다. 그러나 이는 엄청난 시간과 노력은 물론 막대한 실험비용이 소요되기 때문에 경제적으로 효용성이 매우 낮아 현실적으로 수행이 어렵다. 이에 비해 수치모형실험은 상대적으로 저렴한 비용으로 수행할 수 있으며, 다수의 실험을 수행하지 않아도 불확실성을 제거할 수 있어 수리모형실험의 검증에 효율적이다. 일반적으로 난류 거동을 동반하는 복잡한 구조물 주변의 흐름 해석에는 3차원 CFD 모형이 필요하다. 특히, 병렬연산이 가능한 CFD 모형을 활용하면 수리모형실험에서도 재현이 쉽지 않은 다양한 조건에 따른 복잡한 흐름을 해석할 수 있어 효용성이 점점 증가하고 있다. 그러나 복잡한 구조물이 존재하게 되면 구조물에 재현에 막대한 격자구조가 필요하여 현실적으로 적용이 쉽지 않다. 이에 대한 대안으로 복잡한 구조물을 비교적 큰 격자에서 재현할 수 있는 가상경계법을 활용하는 연구가 활발히 진행되고 있다. 가상경계법은 Navier-Stokes 방정식에서 유체 내에 존재하는 고체를 모멘텀 이론으로 대체하여 고려하는 기법으로 수치모델링 수행 시 매질을 유체만으로 구성할 수 있어 안정적으로 적용할 수 있는 것으로 알려져 있다. 본 과업에서는 다양한 분야에서 널리 활용되고 있는 3차원 CFD 모형인 OpenFOAM®기반으로 파랑해석에 필요한 경계조건을 계산할 수 있는 olaFlow를 활용하여 복잡한 구조물을 지나는 파랑해석을 수행하기 위해 가상경계법을 olaFlow에 도입한 수치 알고리즘을 개발하였다. 개발한 수치알고리즘을 활용하여 복잡한 구조를 수치모델에서 재현하였으며, 수치모델에 적용된 수치 알고리즘의 안정성에 대해 고찰하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.129-145
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• 2019

For the design of composite breakwater as representative one of the coastal and harbor structures, it has been widely discussed by the researchers about the relation between the behavior of excess-pore-water pressure inside the rubble mound and seabed caused by the wave load and its structural failure. Recently, the researchers have tried to verify its relation through the numerical simulation technique. The above researches through numerical simulation have been mostly applied by the linear and nonlinear analytic methods, but there have been no researches through the numerical simulation by the strongly nonlinear mutiphase flow analytical method considering wave-breaking phenomena by VOF method and turbulence model by LES method yet. In the preceding research of this study, olaFlow model based on the mutiphase flow analytical method was applied to the nonlinear interaction analysis of regular wave-composite breakwater-seabed. Also, the same numerical techniques as preceding research are utilized for the analysis of irregular wave-composite breakwater-seabed in this study. Through this paper, it is investigated about the horizontal wave pressures, the time variations of excess-pore-water pressure and their frequency spectra, mean flow velocities, mean vorticities, mean turbulent kinetic energies and etc. around the caisson, rubble mound of the composite breakwater and seabed according to the changes of significant wave height and period. From these results, it was found that maximum nondimensional excess-pore water pressure, mean turbulent kinetic energy and mean vorticity come to be large equally on the horizontal plane in front of rubble mound, circulation of inflow around still water level and outflow around seabed is formed in front of rubble caisson.