• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1609-1614
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• 2003

In this study, a practical holographic interferometric tomography system, which is instantaneous and non-contact for measuring three dimensional flow field, was developed. The system consists of holographic recording/reconstruction system, fringe analysis code and computational tomography code and it is developed with Gill environment for general users. The developed system was applied to three-dimensional natural convection from a discrete flush-mounted circular heat source on the bottom of a cubic enclosure. The heat source was located at the off-center of the bottom plate so that three-dimensional temperature field can be achieved. A set of multi-directional holographic interferograms was recorded by employing a double-reference beam, double-exposure holographic technique. Optical pathlength data were extracted from the recorded interferometric data and finally three dimensional temperature field inside the cube was reconstructed.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.151-157
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• 1996

Postural tremor of the upper arm in a static posture was measured to provide guidelines of hand tool weight. Three types of camera recording postures were selected. Postural tremor was measured on five levels of tool weights; no weight, 400g, 800, 1200g, and 1600g. For each conditions, upper arm postural tremor was measured together with EMG of biceps, deltoid, and pectoralis major, and Borg's CR-20 scale ratings of perceived exertion. Results of the experiment are as follows; Frequency analysis of tremor revealed that increased amplitude of frequency band of 2-4Hz and 10-14Hz was observed. Postural tremor of the upper arm maintained the initial level until fatigue developed. After the development of fatigue, the rate of the change of postural tremor was significantly increased. Different tool weights and hand postures showed different rate of tremor increase. And time to fatigue and the corresponding endurance time was positively correlated with Borg's RPF scores.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.964-967
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• 2001

Aspherical lens with the higher numerical aperture has been needed in the optical storage device to increase the recording density on the disk. However, high numerical aperture means the large slope angle at the clear aperture of the lens. Therefore, the measurement and manufacturing technique including the lens molding process for the slope angle should be developed. In this paper, the evaluation technique was described for the optical performance of the aspherical lens. Aspherical form error brings about the wavefront error and the side lobe of the beam intensity profile. A schematic diagram of the aspherical lens manufacturing was drawn to explain the aspherical form error compensation. Finally, form error of the aspherical lens was defined and plotted using the raw data of the Formtalysurf.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.539-544
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• 2001

The holographic measurement techniques can be applied to various industrial fields such as automobile, airplane, construction, electronics, medical, mechanics and physics. The visualization of fluids is very important in aerodynamics, heat transfer and stress analysis. There are classically optical methods such as shadowgraph, schlieren method, and Mach-Zehnder interferometry for visualizing the fluid flow phenomena. But, it is difficult to understand the continuous state of fluids well in those methods. In this study, the real-time holographic interferometer with high-speed camera is applied to the flow visualization. In addition, collimated laser beam and rotating wedge are used for recording and formation of carrier fringes, respectively.

• Proceedings of the KSPS conference
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• 2005.04a
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• pp.29-33
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• 2005

This study aims to establish a speech corpus for Korean as a foreign language (L2 Korean Speech Corpus, L2KSC) and to examine the aspects of the foreign learners acquisition of the phonetic and phonological systems in the Korean Language. In the first year of this project, L2KSC will be established through the process of reading list organizing, recording, and slicing, and the second year includes an in-depth study of the aspects of foreign learners Korean acquisition and a contrastive analysis of phonetic and phonological systems. The expectation is that this project will provide significant bases for a variety of fields such as Korean education, academic research, and technological development of phonetic information.

• Proceedings of the KSPS conference
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• 2003.10a
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• pp.129-132
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• 2003

The purpose of this study was to investigate the fundamental frequency(Fo) of voice signal, the first to the third(F1-F3), and duration in children with hearing impairment. Each subject made a recording of sustained /i/ and /a/, four VbV as and four VsV. The Praat 4.1.6. was used for analysis. The results of this study were as follows: First, F0 of children with hearing impairment were higher than normal children. Second, /a/ vowel was showed that F1, F2 and duration were higher than normal children. Third, /i/ vowel was showed that F1 and duration were higher than normal children. However, F2 was lower than normal children. Therapeutic implications have been drawn.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.183-186
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• 2007

This study analyzes Korean high school students' pronunciation errors in word-initial onglides in English. For this study, 24 Korean high school students read 34 English words including glide-vowel sequences in word-initial positions and vowel-initial words in a frame sentence. The results showed 2 different error types: glide deletion and vowel distortion. After the analysis of the first recording, the subjects were taught how to pronounce glide-vowel sequences properly in a 60-minute class. Comparison of the analyses of the first and second recordings showed that the subjects improved on the pronunciation of glide-vowel sequences. After the training, the pronunciation errors of diphthongs unique to English, [$j_I$], decreased substantially. However, most subjects still had difficulties in pronouncing [$w{\mho}$], [wu], and [wo]. There was no significant correlation between English course grade and error reduction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.874-875
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• 2008

Gap servo NFR (Near Field Recording) system is one of technologies to reduce beam spot size by increasing NA (Numerical Aperture) of lens. To achieve high NA, SIL (Solid Immersion Lens) is used. In case of using a blue LD (405 nm) as the light source the gap distance should be controlled under 100 nm with much tighter margin. To develop NFR disc drive with very small gap distance between SIL bottom and the surface of media, we need to research for the vibration characteristics and design considerations. This paper deals with a study on vibration characteristic of NFR disc drive.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.87-92
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• 1998

In general, the synthesis unit database was constructed by recording isolated word. In that case, each boundary of word has typical prosodic pattern like a falling intonation or preboundary lengthening. To get natural synthetic speech using these kinds of database, we must artificially distort original speech. However, that artificial process rather resulted in unnatural, unintelligible synthetic speech due to the excessive prosodic modification on speech signal. To overcome these problems, we gathered thousands of sentences for synthesis database. To make a phone level synthesis unit, we trained speech recognizer with the recorded speech, and then segmented phone boundaries automatically. In addition, we used laryngo graph for the epoch detection. From the automatically generated synthesis database, we chose the best phone and directly concatenated it without any prosody processing. To select the best phone among multiple phone candidates, we used prosodic information such as break strength of word boundaries, phonetic contexts, cepstrum, pitch, energy, and phone duration. From the pilot test, we obtained some positive results.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.290-291
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• 2000

광전달망에서 전송용량의 폭발적인 수요 증가에 대처하기 위한 최적의 솔루션으로 파장분할다중화(WDM: wavelength division multiplexing) 방식이 도입되고 있으며, 그 적용 영역 또한 장거리 시외망, 단거리 시내망부터 인터넷 트래픽 전달용 백본망을 위한 핵심기술로 정착될 것으로 예측하고 있다. WDM 광전송 방식은 기존의 시분할 다중(TDM: time division multiplexing) 방식이 갖는 동기식(SDH: synchronous digital hierarchy) 전송기술의 한계를 보완할 수 있으며, 신호의 다중화 및 역다중화 구성체계가 단순하고, 입력 광신호에 대한 신호속도나 형태등의 제한도 없기 때문에, 기존의 동기식 전송에 비해 전송용량을 쉽게 확장할 수 있다는 장점을 가지고 있다. (중략)