• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.685-688
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• 2011

본 논문에서는 다양한 음향 가진에 따른 음향 응답을 유한 요소법을 통하여 효과적으로 계산하기 위한 새로운 모델 축소법을 제안한다. 일반적인 유한 요소법을 통한 기계구조물의 응답을 구하기 위해서는 음향 방정식의 강성 및 행렬을 구한 뒤 이들의 조합을 통한 동적 강성행렬을 구한 뒤 역행렬을 구하여 다양한 주파수 응답을 구하게 된다. 현재 컴퓨터 하드웨어의 발전과 소프트 웨어의 발전에 의하여 더 많은 유한 요소를 사용할 수 있게 되었고 이로 인하여 더욱 정확하고 넓은 대역의 음향 응답을 구할 수 있게 되었다. 그러나, 아직까지도 아주 복잡한 구조물의 음향 응답을 구하기 위하여 유한 요소를 무한정으로 증가할 수 없는 경우가 많다. 이를 해결하기 위하여 일반적으로 모델 축소법(Model order reduction) 기법을 사용한다. 이 모델 축소법은 기본적으로 전체 행렬을 아주 작지만 효율적인 작은 행렬로 바꾸어 응답을 예측하는 기법으로 mode superposition method, ritz vector method, quasi-static ritz vector method등이 있다. 기존의 모델 축소법은 기본적으로 질량 및 강성행렬이 가진 주파수에 영향을 받지 않는 행렬이라 가정한다. 그렇기 때문에 경계조건이나 다공성 재료를 모델링할 경우 가진 주파수에 영향을 받는 강성행렬과 질량행렬이 만들어지게 되어 기존의 모델 축소법은 효과적이지 못하게 된다. 이런 문제점을 해결하기 위하여 이 논문에서는 Quasi-static ritz vector method의 기본적인 개념을 확장하여 여러 개의 중심 주파수(Center frequency)에서 기저를 계산하고 이를 동시에 이용하는 Multi-frequency quasi-static ritz vector method를 제안한다.

• The Journal of Information Technology
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• v.5 no.4
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• pp.173-183
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• 2002

In this paper, we propose an efficient forecasting methodology of the mid and long-term frequency demand in Korea. The methodology consists of the following three steps: classification of basic service group, calculation of effective traffic, and frequency forecasting. Based on the previous studies, we classify the services into wide area mobile, short range radio, fixed wireless access and digital video broadcasting in the step of the classification of basic service group. For the calculation of effective traffic, we use the measures of erlang and bps. The step of the calculation of effective traffic classifies the user and basic application, and evaluates the effective traffic. Finally, in the step of frequency forecasting, different methodology will be proposed for each service group.

• Phonetics and Speech Sciences
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• v.11 no.1
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• pp.9-18
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• 2019

The purpose of this study is to determine whether the mean fundamental frequency (F0) changes depending on language, task, or language proficiency for Korean-English bilinguals. A total of forty-eight Korean-English speakers (28 balanced bilinguals and 20 Korean dominant bilinguals) participated in the study. Participants were asked to read aloud two types of tasks in English and Korean. For statistical analyses, the language ${\times}$ task two-way repeated ANOVAs were conducted within the balanced bilingual group first, and then group ${\times}$ language two-way mixed ANOVAs. The results showed that the females in both bilingual groups changed their mean F0 depending on the language they used and the tasks (p<.05), whereas no significant results were found in the males in either group under any conditions. The mean fundamental frequency in the Korean reading task was significantly higher than that in the English reading task for females in both balanced and Korean dominant bilingual groups. Thus, changes in mean F0 depending on language and context may reflect gender-specific characteristics, and females seem to be more sensitive to the socio-cultural standards that are imposed on them.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.207-212
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• 2006

The purpose of this study was to compare voice parameters in auditory conditions (normal/noise/music) between a teacher group and a control group. Results of statistical analysis showed that the teacher group had higher jitter (%) and shimmer (%) values than the control group. It indicated that the teacher group had larger variations in pitch and dynamic of their voice. In the teacher group, the voice under noisy condition showed a higher value of fundamental frequency than that under normal condition. though its fundamental frequency did not show any significant difference between the noisy condition and the musical condition. In the control group, however, although the voice under noisy condition also showed a higher value of fundamental frequency than that under normal condition, its fundamental frequency was significantly different between the noisy condition and the musical condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2A
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• pp.213-219
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• 2007

In this paper, A novel structure of frequency doubler using Phase Delay line and $90^{\circ}$ Hybrid coupler at harmonic output have been designed and implemented to improve suppression. Proposed structure of frequency doubler improve output. coupling and fundamental suppression. Active frequency doubler with band from $2.13{\sim}2.15GHz\;to\;4.26{\sim}4.3GHz$ was designed and fabricated with 10dBm input power, 0.79dB conversion gain and -55.54dBc suppression at fundamental frequency, -44.76dBc suppression at third harmonic frequency 6.42GHz and -39.18dBc suppression at fourth harmonic frequency 8.56GHz.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1288-1296
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• 2009

This paper is for multi-frequency thin film loop antenna used on smart phone, PMP and PDA like as a multi-media devices. We developed a loop pattern folding methods to reduce a thin film antenna dimension using that mutual coupling folding loop occurs the higher frequency resonation. To reduce the thin film size for loop antenna, we fold the loop pattern repeatedly control the coupling coefficient than generate a not only higher mode resonation but also basic resonation from loop pattern. To realization the thin film folded loop antenna, we used a $30mm{\times}9mm$ PI film the thickness is 20um so that we realize the CDMA850, GPS, DCS, PCS, WCDMA antenna simultaneously and it's radiation efficiency is over 50% and gain is 0dBi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.625-630
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• 2011

In this paper, spiral meander monopole printed antenna for dual band operation in GPS(1.57~1.577 GHz) and WiBro(2.3~2.4 GHz), WLAN(2.4~2.48 GHz) is proposed. Spiral(positive coupling) mounted end of monopole(small current) and meander mounted fed of monopole(big current) for reduce frequency ratio. Bandwidth(-10 dB) of the antenna is measured 130 MHz(1.49~1.62 GHz) in basic resonance frequency and 330 MHz(2.29~2.62 GHz) in harmonic resonance frequency($3{\lambda}_H/4$). The peak antenna gains are measured 2.86 dBi in GPS(1.57 GHz), and 3.49 dBi in WiBro(2.35 GHz), and 3.71 dBi in WLAN(2.44 GHz).

• Electronics and Telecommunications Trends
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• v.7 no.1
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• pp.38-46
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• 1992

음성통신에 있어 전화기의 주파수 특성은 음량과 함께 통화품질에 많은 영향을 미친다. 각 국에서는 자국의 통신실정에 맞는 주파수 특성을 규정하고 있지만, 다른 나라의 규정을 그대로 도입하는 것은 도리어 전화기의 품질 열화를 초래할 수 있다. 본 고에서는 전화통화에 있어 만족한 통화품질을 얻을 수 있는 바람직한 주파수 특성을 구하고자, 주파수 특성에 대하여 오피니언 평가 및 선호도 평가를 실시하고, 그 결과를 기본으로 최적 주파수 특성에 대해 검토하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2A
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• pp.194-200
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• 2006

A 26.4 GHz phase locked oscillator(PLO) for communication satellite transponder is developed. The PLO consists of fundamental frequency generation module(FFGM) and frequency multiplication part(FMP). The signal of 26.4 GHz is generated through frequency tripling process of 8.8 GHz fundamental frequency. Phase locking technique using sampling phase detector(SPD) is adopted to design the FFGM. The MMIC tripler and amplifier are also designed for the reduction of the size and mass of FMP. The phase noise characteristics are exhibited as -96 dBc/Hz at 10 tHz offset frequency and -105 dBc/Hz at 100 kHz offset frequency, respectively, with the output power over 11 dBm. All performance parameters are complied with the design requirements.

• The Journal of the Acoustical Society of Korea
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• v.14 no.6
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• pp.32-39
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• 1995

This paper describes a method of musical frequency estimation using tree structured octave band filter banks and the constant Q spectral transform. The performances of the proposed method are compared with those of the conventional constant Q transform using FFT. The performances are evaluated by the estimated fundamental frequency, varying the bandwidth and the frequency resolutions. The results are as follows. With the same frequency resolution of the conventional constant Q transform using FFT, the proposed method gives the better time resolutions, thus, the limit of the processing bandwidth is removed. And, when the bandwidth and the frequency resolution are set high for more accurate results, the computational complexity of the proposed method is less than that of the conventional one.