• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.81-92
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• 2001

According to analyses of high-resolution seismic profiles (air gun, sparker, and SBP) and a deep-drill core(YSDP 105) in the mid-eastern Yellow Sea, stratigraphic and geoacoustic models have been established and seismo-acoustic modeling has been fulfilled using ray tracing of finite element method. Stratigraphic model reflects seismo-, litho-, and chrono-stratigraphic sequences formed under a significant influence of Quaternary glacio-eustatic sea-level fluctuations. Each sequence consists of terrestrial to very-shallow-marine coarse-grained lowstand systems tract and tidal fine-grained transgressive to highstand systems tract. Based on mean grain-size data (121 samples) of the drill core, bulk density and P-wave velocity of depositional units have been inferred and extrapolated down to a depth of the recovery using the Hamilton's regression equations. As goo-acoustic parameters, the 121 pairs of bulk density and P-wave velocity have been averaged on each unit of the stratigraphic model. As a result of computer ray-tracing simulation of the subsurface strata, we have found that there are complex ray paths and many acoustic-shadow zones owing to the presence of irregular layer boundaries and low-velocity layers.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.1
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• pp.33-37
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• 2000

The 1-3 piezoelectric composite transducer with 75 volume percents PZT was fabricated by the dicing-filling method. The resonance modes of the 1-3 transducer have been studied with electric impedance measurement as a function of frequency. The fundamental frequencies of the planar and thickness mode were observed at 0.95MHz and 1.63MHz respectively, but the lateral mode was not observed. In the thickness mode, the electromechanical coupling coefficient of the 1-3 piezoelectric composite transducer, 0.54, was very closed to that of the single phase PZT(0.52). The pulse-echo response by exciting the 1-3 transducer with an electric pulse was observed from the water/reflector interface, and analyzed bandwidth by the spectrum of the impulse response. The quality factor Q for the 1-3 transducer was observed as 1.5 smaller than that of the single phase(80) and then the 1-3 transducer may be used to the broad band type transducer applications.

• Journal of Digital Contents Society
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• v.13 no.3
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• pp.279-290
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• 2012

The purpose of this experimental study is to investigate and compare the vowel lengths of the English diphthongs, /eɪ/ and /aɪ/, and the front low vowel /æ/ among English-speaking natives with Korean college students using the Praat software program. To do this English sentences were uttered and recorded by twelve subjects, six Korean subjects and six English-speaking native subjects. All the subjects are female and their age ranges from 23 to 35. Acoustic features(duration) were measured from a sound spectrogram with the help of the Praat software program and analyzed through statistical analysis. Results showed that the vowel lengths of the English diphthongs and the front low vowel between native English speakers and Korean collegians were different. In the pronunciation of the diphthongs /eɪ/ and /aɪ/, Korean subjects pronounced longer than native subjects did, but the difference was not significant. However, in the pronunciation of the English front low vowel /æ/, native subjects pronounced significantly longer than Korean subjects did. From the data of the overall sum of words and vowels between the two subject groups, we were able to find out that the differences of lengths of both the three words and the two diphthongs /eɪ/ and /aɪ/ were not significant, but those of /æ/ were significant.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.64-72
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• 2007

Under the AE methods, the valid condition analysis and evaluation the leak etc, resulted by the AE signal pattern on the bottom plate of ground tank at full. In next more, the gradient of accumulation amplitude distribution analysis and comparison the energy, count, and duration time that noise of EMI signal were removed. EMI signal showed height-energy, count, and duration time, it also appeared great gradient of accumulation distribution. Then, with the pure remaining AE signals cluster analysis and location. It would possibly assume of damage with corrosion. Total cluster 20 and energy showed between the maximum 11,990 and 8,565 which is much lower than above figure and event number showed from 8 to 5. Even when it difficult to certify damage by open, as it is raised higher height-sensitivity and threshold by 60 dB. It would possibly presume of location source more accurately.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.5
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• pp.35-43
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• 2022

Precise modeling and analysis of closed bomb test(CBT) combustion using solid propellants was performed. The fluid structure interaction(FSI) method was implemented to analyze the gas and solid phases at the same time. The Eulerian analysis method was applied for the gas phase and grain combustion, and the Lagrangian analysis method was implemented for the grain movement. The interaction between the solid phase grains and the combustion gas was fully coupled through the source term. The volume of fluid(VOF) method was used to simulate the burning distance of the grain and the movement of the combustion surface. The force acting on the grain was comprised of the pressure and gravity acting on the grain burning surface, and the grain burning rate and grain movement speed were considered in the velocity term of the VOF. The combustion analysis was performed for both one and three grains, and fairly compared with the experiments. The acoustic field during grain combustion due to pressure fluctuations was also analyzed.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.233-233
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• 2021

ADCP(Acoustic Doppler Current Profiler)는 유수의 흐름을 방해하지 않으면서 수중에 발사된 음파의 도플러 효과를 이용하여 3차원 유속 측정이 가능한 초음파 유량측정장비이다. 2009년부터 다양한 하천에서 ADCP 사용량이 증가하면서 ADCP를 이용한 유량측정 기법과 현장 적용상의 문제, 자료처리 과정에서의 문제점들이 발생하고 있다. 이런 문제점들을 분석한 결과 다음과 같은 사례들이 나타났다. 첫 번째 하상이 매우 불규칙한 단면의 부적절한 측정 사례, 두 번째 하안 수직벽 존재에 따른 단면의 부적절한 측정 사례, 세 번째 수심 오측이 다수 발생한 측정 사례, 네 번째 유속 프로파일 결측이 다수 발생한 측정 사례, 다섯 번째 통신문제로 인한 주기적인 결측이 발생한 측정 사례, 여섯 번째 홍수기 고농도 유사로 인해 결측이 발생한 사례, 일곱 번째 수중식생의 영향으로 수심 및 유속 프로파일 오측이 발생한 측정 사례, 여덟 번째 이동상 조건이 발생한 측정 사례 등 많은 문제들이 발생하였다. 본 연구에서는 수중식생의 영향으로 수심 및 유속 프로파일 오측이 발생하는 사례에 대해 개선할 수 있는 방안을 연구하였다. ADCP에서 수중에 발사한 음파 중 식생에 부딪친 강한 반사파의 노이즈로 side-lobe현상에 의한 오측 및 결측이 발생한다. 현재 오측 및 결측 자료는 ADCP 제조사별 자료 취득 소프트웨어의 기능에 의존 하거나, USGS의 OSW(Office of Surface Water) Hydroacoustics의 QRev를 이용하여 후처리 과정을 거쳐 측정 자료로 정리하고 있다. 이에 본 연구에서는 노이즈로 인한 side-lobe 현상을 물리적인 방법으로 제거하기 위해 음향 녹음 과정에서 노이즈를 물리적인 방법으로 제거하는 윈드실드와 팝 필터를 고려한 ADCP필터를 개발하여 적용하였다. 이번 연구의 대상지점은 원주시(지정대교)수위관측소로 5월 이후 수중에 식생이 성장하는 지점이다. 먼저 ADCP필터를 제거한 상태에서 측정을 실시하고, 이후 ADCP필터를 장착하여 측정을 실시하였다. ADCP필터 적용의 측정성과에서는 노이즈에 의한 오측 및 결측이 다수 발생하는 것을 볼 수 있고, ADCP필터를 적용한 측정성과에서는 노이즈가 제거되어 오측 및 결측이 개선되는 결과를 볼 수 있었다. 본 연구에서는 수중식생 영향으로 강한 반사파에 의한 노이즈로 side-lobe현상에 의한 ADCP측 정성과의 오측 및 결측을 ADCP필터를 적용하여 물리적인 방법으로 노이즈를 제거 할 수 있다는 결과를 얻었다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.107-116
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• 1999

To study the characters of surface sediment and to describe the seasonal depositional environment as a result of sedimentation process off Byun-San Peninsula, a total 61 samples of surface sediment (32 samples in summer; 29 samples in winter) were collected and analysed. A digitized depth data from sea chart and echosounding profiles along five trans-sections were helpful for understanding the morphological factors. The types classified by the characters of surface sediment are type I (sand, S), type II (silty sand, zS), and type ill (sandy silt, sZ). Mean grain size varies from 2.11 to 7.81 ${\Phi}$. The positive-skewness shows the typical tide-dominated environment. The sediment type of the northwestern stations is medium sand and the sorting value is 0.5~1.4 ${\Phi}$ of well/moderately sorted. Meanwhile, other stations are composed of muddy sands and sandy muds transported from rivers and offshore. These sediment types toward inshore change gradually from silty sand to sandy silt. According to the C/M diagram, there are three major transport modes of sediment: bed load (Mode A), graded suspension (Mode B), and suspension (Mode C), correlating with north-eastern sandy area, middle part of silty-sand area, and southern sandy-silt area, respectively. The result of Principal Component Analysis shows also similar pattern of sediment types. In result, sediment texture of type III tends to be finer and more poorly-sorted than that of type II and sediment facies are correlateed with sedimentation process.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.94-101
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• 2019

Most of the existing rail structures have undergone a lot of aging since a considerable period of time has passed from completion. In particular, among existing railway bridges, many of the plate girder bridges are older bridges that have lived 40 to 60 years or more. Since the treadmill is directly connected to the girder without the ballast, the running load of the vehicle is directly transmitted to the bridge. Therefore, the shock and noise applied to the bridge are larger than those of the ballast bridge, and the dynamic shock and vibration are also relatively large. Therefore, it is very urgent to develop appropriate maintenance, repair and reinforcement technology for existing steel plate bridge. In this study, the authors introduced the characteristics of embedded rail (ERS) developed for improving the performance of the existing plate girder bridge and the techniques solving the vibration and noise problems. In order to evaluate the vibration and noise reduction performance of ERS, a non-ballast plate girder bridge with 5m length of sleepers installed and a plate girder bridge with ERS were fabricated. And, then, the vibration response generated under the same excitation condition was measured and analyzed. Also, the radiated noise analysis was performed using the vibration response data obtained from the experiment as the input data of the acoustic analysis model. As a result of experiments and analyses, it was confirmed that the plate girder bridge's vibration using ERS was reduced by 15.0~18.8dB and the average noise was reduced by 7.7dB(A) more than the non-ballast bridge.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.266-269
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• 2010

급속한 정보 통신 기술의 발달로 인해 멀티미디어 재생 개발 기술들은 단순히 수동적으로 보고 듣는 재생 기술에서 벗어나 청취자 감성, 취향 등에 따라 보다 실감 있고 사용자가 능동적으로 재생할 수 있는 기술로 진화 하고 있다. 지금까지의 오디오 서비스는 음원 개발자 중심의 오디오 서비스, 즉 보컬 및 모든 악기가 믹스된 단일음원이기 때문에 사용자는 단순히 오디오 음원 개발자나 음반 제작사가 발매한 단일 음원을 일방적으로 수동적 청취할 수밖에 없다. 하지만 사용자 능동형 오디오 서비스에서는 사용자가 능동적으로 자신이 원하는 음악적 취향에 따라 능동적으로 각각의 객체 기반의 독립 음원을 선택, 감성에 따른 음원 효과 추가, 최적의 음원 청취 위치(Sweet Spot) 변경, 음원 및 스피커 재생 공간 및 위치 변경 재생 등을 할 수가 있다. 본 논문에서는 디지털 음원들을 입력받아 임의의 필터링을 실행하고, 사용자 음원 보정 정보, 출력 유닛의 공간적, 음향적 특성을 상위제어기로부터 입력받아 전신호경로 상에 디지털 신호처리 하여 출력신호를 생성하는 DSP 시스템 플랫폼 및 알고리즘에 관하여 소개한다.

• Journal of the Korea Computer Industry Society
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• v.7 no.5
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• pp.555-562
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• 2006

Computer animation is tile most advanced composite art to apply image, sound to the theme, Domestic technique is improved but still lacks creativity and content in theinternational market. In this paper, I'll notify the importance of planning and introduce narrative animation to produce their own style of animation. A successful career in the digital animation industry requires more than just technical expertise. It also demands creative mastery, a sense of wonder and boundless imagination. This unique hands-on program combines traditional, creative and technical skills and develops digital artists, not software technicians. Especially, people involved in the industry shouldrecognize a special quality of narrative animation in today's 3D animation and game- saturated climate. Therefore, they are able to create a new form of high-quality animation. It will be expected to promote digital animation education with a new index.