• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.92-93
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• 2001

주파수 안정화 레이저 광원은 10-6 이상의 상대 불확도가 필요한 간섭계에서 널리 쓰이고 있으며 특히 변위 측정 시스템에서는 반드시 쓰이고 있다. 상용화된 많은 변위 측정 시스템은 신호 대 잡음비가 우수하고 광학계의 정렬이 더 쉬운 헤테로다인 방식을 채택하고 있으며 이를 위해서 서로 수직 선형 편광인 다른 주파수의 광을 내보내는 광원이 필요하다. 현재 헤테로다인 변위 측정 시스템에 쓰이고 있는 광원은 이중 주파수 광원을 만드는 방식에 따라 지만 효과(Zeeman effect)를 이용한 지만 레이저(HP사)와 음향-광 변조기(Acousto-optic modulator)를 이용한 이중 주파수 레이저(Zy해사)가 있다. (중략)

• Journal of the Korean Institute of Telematics and Electronics
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• v.14 no.2
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• pp.28-31
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• 1977

Normal modes of carrier waves due to longitudinal modulation in solids have been defined. The dispersion relationship of these waves in the presence of collision effects and thermal diffusion is derived and examined in detail. It is also shown that the carrier waves are reduced to the wellknown space-charge waves and electroacoustic hayes in special cases.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.29-29
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• 2004

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.516-519
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• 2012

This study proposes a method of an equivalent bell model in order to tune the beat period of a Korean bell. In a Korean bell having a slight asymmetry, each circumferential mode splits into a mode pair which has a slight difference in frequency, and the interaction of the mode pair makes a beat in vibration and sound. An equivalent bell model which consists of an axi-symmetric bell and an equivalent point mass, has the same mode property as in a real bell. The equivalent bell model is constructed by the finite element analysis based upon the theory of a revolutionary shell Using the equivalent bell model, the beat period is predicted when the bell thickness is locally decreased to improve the beat property. The predicted result is verified by experiment on a test bell. The proposed method is useful to save the time required for tuning the beat period of a large bell.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.854-855
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• 2013

As an unique acoustic characteristic of a Korean bell. beat phenomenon is a periodic repetition of strong and weak sounds. Beat sounds good when it is clear and it has a proper period, however, it is not easy to satisfy these two conditions simultaneously. In this study, we propose a beat tuning method to satisfy these two conditions, by using an equivalent bell model. First, we construct an equivalent bell which has the same beat property with the 1st beat of a real bell and we investigate the change of mode pair by finite element analysis, when thickness of the bell is locally decreased at $22.5^{\circ}$ from the striking point. From the analysis result, minimum thickness reduction amount is determined to make a clear and strong beat.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.186-193
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• 2017

Silla Great Bell was manufactured in order to ring for the new millennium in succession to King Seongdeok Divine Bell. This study investigates how Silla Great Bell is similar to King Seongdeok Divine Bell in respect of structure and sound. First, design and manufacturing processes are introduced and dimensions of the two bells are compared and the similarity is estimated. Three main characteristics of the sound of a Korean bell are magnificent and harmonic striking sound, dynamic beat, and long lasting hum tone. These three features are compared and objectively estimated using physical parameters. The purpose of the study is to provide useful information to manufacture Korean bell which has beautiful appearance and excellent sound.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.222-227
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• 1995

A single mode, 100-mW diode laser was injection-locked by the master laser which was spectrally narrowed with Littman-type grating feedback. In the incomplete-injection-locking, we observed that two frequencies were simultaneously generated from the slave laser. The power ratio and frequency shift of two frequency components were proportional to the square of injected laser intensity. When the ratio of the injection intensity to the slave laser intensity was about $10^{-3}$, the injection-locking bandwidth was to be about 1.4 GHz. The bandwidth proportionally increased to the square root of the injection intensity, which was in good agreement with the theoretical predictions. The Iinewidth of the locked-laser was about 2.5 MHz, which was five times as narrow as that of free-running operation. ation.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.107-115
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• 1997

비성형 동력학계로 모델링된 부유수송체의 동적응답을 조사하고 그 운동의 안정성을 해석하였다. 종동요 모우드의 고유주파수가 횡동요 모우드의 고유주파수의 두배가 되는, 즉, 2:1 내부공진 혹은 자기계수공진인 조건하에서, 이부유수송체는 한 운동 모우드의 직접가진에 의해 간접가진된 다른 모우드가 대진폭 응답을 보일 수 있음을 밝혔다. 또항, 종동요 모우드의 감쇠력은 비교적 넓은 범위의 운동에 대해 선형적임에 반해, 횡동요 모우드의 감쇠력은 점성의 영향이 대단히 커서 비선형성이 대단히 강한 것으로 알려져 왔다. 이 문제를 수학적으로 모델링하기 위하여, 종동요 모우드의 운동방정식에는 선형및 제곱형의 합의 형태인 감쇠력 모형을 사용하였다. 다중척도법을 사용하여 이 두가지 운동 모우드의 주기적 응답및 그의 안정성에 미치는 제곱형 비선형 횡동요 감쇠력의 영향을 밝혔다. 조우주기가 횡동요 모우드의 고유주기와 근사한 경우에 대하여 이 비선형계의 응답을 구하고 주파수-응답 곡선으로 나타내었다.

• Journal of IKEEE
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• v.19 no.3
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• pp.311-318
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• 2015

This dissertation proposes method for development technology of voice and SMS(Short Message Service) alarming system based on modbus protocol. The proposed technology is composed of the following 3 stages; hardware development based on microprocessor, development of input and output driver for modem, mp3 decoder, making modbus protocol stack. In the stage of hardware development based on microprocessor, we develop hardware which receives alarm from modbus master and transmit sms message, play mp3. In the stage of development of input / ouput device driver such as modem, mp3 decoder, we develop program which control each devices. In the stage of making modbus protocol stack, voice and sms alarm system is made for receiving alarm via modbus protocol. To evaluate performance of proposed technology, we issued alarm to voice and sms alarming system on purpose. As a result, response speed of detecting alarm was 10.7ms, communication distance was 1.2Km, operating temperature was from $-25^{\circ}C$ to $70^{\circ}C$, we confirmed supporting modbus protocol. And we verified that proposed voice and sms alarming system in the thesis has a performance to be used as an industrial building alarming system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.130-136
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• 2002

In this paper, a flight test method is described for the system identification of the unmanned aerial vehicle equipped with an automatic flight control system. Multistep inputs are applied for both longitudinal mode and lateral/directional excitation. Optimal time step for excitation is sought to provide the broad input bandwidth. A programmed mode flight test method provides high-quality flight data for system identification using the flight control computer with the longitudinal and lateral/directional autopilot which enables the separation of each motion during the flight test. In addition, exact actuating input that is almost equivalent to the designed one guarantees the highest input frequency attainable. Several repetitive flight tests were implemented in the calm air in order to extract the consistent system model for the air vehicle. The enhanced airborne data acquisition system endowed the high-quality flight data for the system identification. The flight data were effectively used to the system identification of the unmanned aerial vehicle.