• 말소리와 음성과학
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• 제13권3호
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• pp.65-70
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• 2021

This paper proposes a method for designing a large recording script for open domain English speech synthesis. For read-aloud style text, 12 domains and 294 sub-domains were designed using text contained in five different news media publications. For conversational style text, 4 domains and 36 sub-domains were designed using movie subtitles. The final script consists of 43,013 sentences, 27,085 read-aloud style sentences, and 15,928 conversational style sentences, consisting of 549,683 tokens and 38,356 types. The completed script is analyzed using four criteria: word coverage (type coverage and token coverage), high-frequency vocabulary coverage, phonetic coverage (diphone coverage and triphone coverage), and readability. The type coverage of our script reaches 36.86% despite its low token coverage of 2.97%. The high-frequency vocabulary coverage of the script is 73.82%, and the diphone coverage and triphone coverage of the whole script is 86.70% and 38.92%, respectively. The average readability of whole sentences is 9.03. The results of analysis show that the proposed method is effective in producing a large recording script for English speech synthesis, demonstrating good coverage in terms of unique words, high-frequency vocabulary, phonetic units, and readability.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.252-256
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• 2003

Tuned Mass Damper(TMD) has been applied in various fields in order to mitigate these vibrations. The shape or configuration of TMDs being unrestricted, a large panel of designs is possible to improve their effectiveness and economical-efficiency, where ingenuity plays an essential role and is required. This study presents an application of a new-type TMD on lamp posts to reduce vibrations induced by loads with large frequency domains such as wind loads. It is shown that the proposed TMD absorbs efficiently the energy without being restricted by frequency contents of the vibration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.297-300
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• 2005

This paper presents vibration control of an engine mount for a passenger vehicle utilizing ER fluid and piezoelectric actuator. The proposed engine mount can be isolated the vibration of wide frequency range with many types of amplitude. The main function of ER fluid is to attenuate vibration for low frequency with large amplitude, while the piezoelectric actuator is activated in hish frequency range with small amplitude. A mathematical model of the engine mount is derived using Hydraulic model and mechanical model. After formulating the governing equation of motion, then field-dependent dynamic stiffness of the engine mount is evaluated for various engine speed and excitation amplitude conditions. Then robust controller is designed to attenuate vibration of wide range frequency component. Computer simulation is undertaken in order to evaluate the vibration control performance such as transmissibility magnitude in frequency domains.

• Structural Engineering and Mechanics
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• 제14권1호
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• pp.39-56
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• 2002

In order to trace a target in deep sky, a feed cabin 20 tons in weight used for a large radio telescope is drawn with six cables. To realize a smooth tracing all the time, optimal distribution of the cable tensions is explored. A set of cable-clog systems is utilized to control the wind-induced vibration of the cable-cabin structure. This is an attempt to apply the passive structural control strategy in the area of radio astronomy. Simulations of wind-induced vibration of the structure in both time and frequency domains offer a valuable reference for construction of the next generation large radio telescope.

• 한국소음진동공학회논문집
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• 제24권7호
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• pp.569-574
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• 2014

In order to investigate low frequency swishing noise of wind turbines, acoustic source model using a singularity in circular motion is introduced to derive analytic solution of Lowson acoustic analogy in time domain. Results in time and frequency domains computed by the solution show apparent modulation of amplitude and frequency. The solution indicates that time histories of acoustic pressure at receiver points varied significantly according to receiver's directional location, even when the retarded time distributions are similar. However, the corresponding time-averaged spectra of sound pressure at the receiver locations where the retarded time distributions are almost same are not significantly different. It can be inferred from these results that the time-averaged sound pressure spectra which cannot take into account the detailed difference in the time-variation of wind turbine noise may not represent the sound quality of wind turbines due to its swishing. Finally, as an introduction of procedure to quantify low frequency swishing noise level, relative variation of overall sound pressure level is obtained using tonal low frequency noise model.

• Structural Engineering and Mechanics
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• 제34권6호
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• pp.755-778
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• 2010

Near-fault ground motion with directivity or fling effects is significantly influenced by the rupture mechanism and substantially different from ordinary records. This class of ground motion has large amplitude and long period, exhibits unusual response spectra shapes, possesses high PGV/PGA and PGD/PGA ratios and is best characterized in the velocity and the displacement time-histories. Such ground motion is also characterized by its energy being contained in a single or very few pulses, thus capable of causing severe damage to the structures. This paper investigates the characteristics of near-fault pulse-like ground motions and their implications on the structural responses using new proposed measures, such as, the effective frequency range, the energy rate (in time and frequency domains) and the damage indices. The paper develops also simple mathematical expressions for modeling this class of ground motion and the associated structural responses, thus eliminating numerical integration of the equations of motion. An optimization technique is also developed by using energy concepts and damage indices for modeling this class of ground motion for inelastic structures at sites having limited earthquake data.

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1561-1565
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• 2018

The dielectric properties of the uniaxial relaxor ferroelectric $Sr_xBa_{1-x}Nb_2O_6$ with x = 0.75 were investigated along the polar [001] direction as a function of temperature. The capacitance maximum showed the frequency dispersion commonly observed in relaxors. Additional weak dielectric anomalies were observed in the paraelectric phase; they were only seen during the heating process and disappeared upon subsequent cooling. These were attributed to the existence of large polar clusters strongly pinned at defects and/or to random fields and their metastable characters. Aligning the ferroelectric domains along the polar axis at room temperature removed the high-temperature dielectric anomalies. The dependences of the capacitance and the dielectric maximum temperature on the magnitude of the poling field were investigated.

• 한국IT서비스학회지
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• 제15권3호
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• pp.71-95
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• 2016

In recent years, text mining has been used to extract meaningful insights from the large volume of unstructured text data sets of various domains. As one of the most representative text mining applications, topic modeling has been widely used to extract main topics in the form of a set of keywords extracted from a large collection of documents. In general, topic modeling is performed according to the weighted frequency of words in a document corpus. However, general topic modeling cannot discover the relation between documents if the documents share only a few terms, although the documents are in fact strongly related from a particular perspective. For instance, a document about "sexual offense" and another document about "silver industry for aged persons" might not be classified into the same topic because they may not share many key terms. However, these two documents can be strongly related from the R&D perspective because some technologies, such as "RF Tag," "CCTV," and "Heart Rate Sensor," are core components of both "sexual offense" and "silver industry." Thus, in this study, we attempted to discover the differences between the results of general topic modeling and R&D perspective topic modeling. Furthermore, we package social issues from the R&D perspective and present a prototype system, which provides a package of news articles for each R&D issue. Finally, we analyze the quality of R&D perspective topic modeling and provide the results of inter- and intra-topic analysis.

• 대한전자공학회논문지TC
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• 제44권1호
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• pp.24-31
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• 2007

지상파 디지털 방송 (Digital Video Broadcasting-Terrestrial; DVB-T)은 고속의 데이터 전송이 가능한 중요한 멀티미디어 방송기술이다. 직교 주파수 분할 다중화 (Orthogonal Frequency Division Multiplexing; OFDM)는 유럽에서 채택된 DVB-T 시스템의 변조방식으로써 다양한 대역폭을 갖는 멀티미디어 서비스를 지원하기 위해 광범위하게 사용되고 있다. 그러나, OFDM 신호는 높은 PAPR (Peak-to-Average Power Ratio)을 발생시키는 단점을 가지고 있다. 본 논문에서는 수신단의 구조에 변화를 주지 않으며 또한 추가적인 정보의 전송이 필요 없이 기존 수신기를 그대로 사용할 수 있는 PAPR 감소기법을 기존의 DVB-T 시스템에 적용하여 그 성능을 평가하였다. 이 방법은 에러 벡터 크기 (Error Vector Magnitude; EVM) 내에서 시간영역과 주파수영역 신호에 대하여 클리핑을 사용한 것으로 기존의 최적화 방법과 비교하여 계산량의 복잡도를 낮추기 위하여 준최적화 방법을 사용하였다. 모의실험 결과, 제안된 기법은 성상도 오차가 클수록 PAPR의 감소효과가 크며 변조레벨이 낮을수록 PAPR의 감소폭이 커짐을 관측하였다.

• 한국해양공학회지
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• 제32권5호
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• pp.341-350
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• 2018

A series of model tests was carried out to investigate the vortex-induced vibration (VIV) characteristics of a free hanging PVC pipe under forced oscillation conditions. The prescribed displacement with a period and amplitude was forced at the top of the riser. The motion of the riser along its length was measured with underwater cameras in three dimensions. The top-excited responses in the inline direction and vortex-induced vibration in the cross-flow direction were examined in the time and frequency domains. Multi-peak frequencies in the VIV were demonstrated to be strongly dependent upon the Keulegan-Carpenter number, corresponding with the results of Blevin. It was found that the Reynolds numbers (excitation period) was a critical parameter for the dominant VIV characteristics, even under the condition of using the same Keulegan-Carpenter number, under the top-excited condition. In the resonance at the nth natural frequency by the forced-motion induced VIV frequency, the riser responded with a large amplitude and forced frequency, dominantly in the VIV CF direction.