• 대한예방한의학회지
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• 제3권1호
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• pp.173-179
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• 1999

압력을 증가시켜가며 맥파를 측정하여 맥파의 진동수와 푸리에 진폭이 가해준 압력에 따라 어떠한 양상을 보이는지 조사하였다. 맥파의 기본 진동수는 압력에 따른 변화를 거의 보이지 않았으며, 푸리에 진폭은 개인의 체질에 따라 몇 가지 유형으로 분류될 수 있음을 보였다. 이 유형들을 다시 푸리에 진폭이 최고점에 이를 때의 압력의 크기와 최고점에서의 상태를 유지할 수 있는 압력의 범위에 따라 맥상의 여러 형태와 연관지을 수 있음을 보였다.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2875-2886
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• 1996

This work present the experimental resutls for the free vibration of unstiffened, stiffened cylindrical shell filled with air, half water and full water. The natural frequencies and mode shapes of unstiffened, stiffened cylindrical shell are obtained experimentally also. The natural frequencies of stiffened cylindrical shell were generally highter than those of unstiffened cylindrical shell and natural requencies were decreased as cylindrical shell was filled with water. The effect of circumferential stiffener in the first mode was shown that natural frequency more increased 25% at air environment, 29% at half water environment and 37% at full water than those of unstiffened cylindrical shell, respectively. Also, the natural frequencies were decreased according to the added mass effect of fluid in the shell of unstiffened and stiffened cylindrical shell. The six mode shape results of all cases are simular and given. The natural frequencies are determined for a wide range of parameters : e.g. unstiffened shell, and filled with air, half and full water. The effects of varying the parameters on the free vibration frequencies and mode shapes are discussed.

• KIEE International Transactions on Power Engineering
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• 제5A권2호
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• pp.138-143
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• 2005

During faults, the voltage and current signals available to the relay are affected by the decaying dc component and harmonics. In order to make appropriate and accurate decisions, most of the relaying algorithms require the fundamental frequency phasor information that is immune to decaying dc effect and harmonics. The conventional Fourier ph as or estimation algorithm is affected by the presence of decaying-exponential transients in the fault signal. This paper presents a modified Fourier algorithm, which effectively eliminates the decaying dc component and the harmonics present in the fault signal. The decaying dc parameters are estimated by means of an out-of-band filtering technique. The decaying dc offset and harmonics are removed by means of a simple computational procedure that involves the design of two sets of Orthogonal digital OFT filters tuned at different frequencies and by creating three off-line look-up tables. The technique was tested for different decay rates of the decaying dc component. It was also compared with the conventional mimic plus the full cycle OFT algorithm. The results indicate that the proposed technique has a faster convergence to the desired value compared to the conventional mimic plus OFT algorithms over a wide range of decay rates. In all cases, the convergence to the desired value was achieved within one cycle of the power system frequency.

• 대한음성학회지:말소리
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• 제48호
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• pp.19-33
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• 2003

Sasang Constitutional Medicine, a branch of traditional Korean medicine, believes that the health of human beings can be promoted by taking advantage of the fact that people have different constitutions. It utilizes the characteristics in human voice to diagnose the constitution of the patients. This study aims at establishing the relationship between Sasang constitutions and their corresponding voice characteristics by investigating source-related variables. Voice recordings of 23 patients from three different constitutions were obtained whose constitutions had been already diagnosed by the experts in the fields. Fundamental frequency related variables (average pitch, maximum/minimum pitch, pitch range), phonation type, speaking tempo were measured and analyzed for each group. The phonation type seemed to be a possible candidate for a successful variable to determine constitution. No statistically significant relationship was manifested between other variables and constitutions. Despite its failure to firmly establish the relationship between voice and constitutions, the current study suggests that future research should include not only source-related variables

• 음성과학
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• 제14권3호
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• pp.7-19
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• 2007

The present study investigated some phonetic attributes which distinguish two Korean stop types $^-aspirated$ and $lax^-$ in a prosodic position which has previously received little attention, namely medial in an accentual phrase. The intonational pattern across syllables which are initial in an accentual phrase (Jun, 1993) is said to depend on the type of stop (aspirated or lax), while that of syllables which are medial in an accentual phrase are not. In Experiment 1, nine native Korean speakers read sentences with a controlled prosodic pattern in which aspirated or lax stops occurred in accentual phrase-medial position. Acoustic analysis revealed significant differences between aspirated and lax stops in closure duration, voice-onset time, and fundamental frequency (F0) values for post-stop vowels. The results indicate that a wider range of acoustic cues distinguish aspirated and lax Korean stops than previously demonstrated. Phonetic and phonological models of consonant-tone interactions for Korean will need to be revised to account for these results.

• 천문학회보
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• 제37권2호
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• pp.63-63
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• 2012

The Square Kilometre Array (SKA) will be the world's largest and most sensitive radio telescope. It will address a wide range of fundamental questions in physics, astrophysics, cosmology and astrobiology. Australia, one of the two countries selected to host the SKA, has spent several years preparing by opening up the Murchison Radio-astronomy Observatory (MRO) as a uniquely radio quiet site in Western Australia, and by constructing the world's most powerful radio survey telescope, the Australian SKA Pathfinder (ASKAP). The SKA will be built in two phases. Phase I will include ASKAP, which will use novel phased-array feeds and grow to become "SKA-survey". Phase I will also include a dish array ("SKA-mid") in South Africa and a low-frequency array ("SKA-low") in Australia, and is slated for operation from about 2020. Phase II of the SKA will consist of further expansion of SKA-low and SKA-mid and is due for completion in the middle of the next decade.

• 센서학회지
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• 제28권2호
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• pp.121-126
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• 2019

The voltage-controlled oscillator is one of the fundamental building blocks that determine the signal quality and power consumption in RF transceivers for wireless sensor networks. Ring oscillators are attractive owing to their small form factor and multi-phase capability despite the relatively poor phase noise performance in comparison with LC oscillators. The phase noise of a ring oscillator can be improved by using a coupled structure that works at a lower frequency. This paper introduces a 2.4 GHz low-noise ring oscillator that consists of two 3-stage coupled ring oscillators. Each sub-oscillator operates at 800 MHz, and the multi-phase signals are combined to generate a 2.4 GHz quadrature output. The voltage-controlled ring oscillator designed in a 65-nm standard CMOS technology has a tuning range of 800 MHz and exhibits the phase noise of -104 dBc/Hz at 1 MHz offset. The power consumption is 13.3 mW from a 1.2 V supply voltage.

• 한국ITS학회 논문지
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• 제1권1호
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• pp.1-9
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• 2002

본 논문에서는 높은 안정도를 가지는 DSRC(Dedicated Short Range Communication)용 유전체 공진 발진기 (DRO : Dielectric Resonator Oscillator)를 설계 및 제작하였다. 제안된 유전체 공진 발진기는 기본 주파수로부터 100kHz 떨어진 곳에서 -109dBc/Hz의 위상잡음 특성을 나타내었다 5.8GHz에서의 출력은 11.53dBm을 나타내었고, 55.33dBc의 2차 고주파 억압 특성을 나타내었다. 이와 같이 위상잡음 특성의 높은 안정성을 갖는 유전체 공진 발진기는 DSRC용 시스템에 응용할 수 있으리라 예측된다.

• 한국정밀공학회지
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• 제28권2호
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• pp.226-232
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• 2011

In this study, an optimized design of a triaxial load cell has been developed by the use of finite element analysis, design of experiment and response surface method. The developed optimal design was further validated by both stress-strain analysis and natural vibration analysis under an applied load of 30 kgf. When vertical, horizontal, and axial loads of 30 kgf were applied to the load cell with the optimal design, the calculated strains were satisfied with the required strain range of $500{\times}10^{-6}{\pm}10%$. The natural vibration analysis exhibited that the fundamental natural frequency of the optimally designed load cell was 5.56 kHz and higher enough than a maximum frequency of 0.17 kHz which can be applied to the load cell for wind-tunnel tests. The satisfactory sensitivity in all triaxial directions also suggests that the currently proposed design of the triaxial load cell enables accurate measurements of the multi-axial forces in wind-tunnel tests.

• 융합신호처리학회논문지
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• 제3권2호
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• pp.45-52
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• 2002

EMI(전자파간섭)은 전기/전자제품의 이상동작을 야기할수 있는 장치로부터 방사되는 10KHz에서 3GHz대역의 전자파를 말한다. 본 연구에서는 안정적이고 정상적인 동작을 위해 2.5Gbps SDH시스템에서 전자파발생원인 STGU유니트에 대하여 전자파간섭을 시뮬레이션하였으며 On-Site Test를 통하여 조화주파수에 대한 전자파 세기를 측정하였다. 또한 소자들간의 EMI를 최소화하기 위하여 2GHz의 Cut-off주파수에서 저역통과필터를 설계하였다. 저역통과필터를 STGU유니트에 적용한 결과 전자파는 약 20dBm이상 감소되었으며 동기기준클럭의 품질을 결정하는 TIE와 MTIE를 측정한 결과 ITU-T G8l3을 만족하였다.