• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.51-59
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• 2006

서해안 조간대에서 24 channel 탐사기로 획득한 표면파 자료의 위상속도와 군속도를 구한다음, 이를 역산하여 그 결과를 비교하였다. 위상속도의 분산곡선은 tau-p stacking 방법에 의하여, 군속도의 분산곡선은 wavelet analysis와 Multiple Filtering Technique의 두가지 방법을 사용하여 구하였다. 위상속도의 오차가 군속도의 오차보다 더 큰 것을 확인하였다. 군속도의 경우, wavelet analysis가 Multiple Filtering Technique 보다 fundamental mode와 higher mode를 구분하는데 더 효과적이었다. 역산결과, 군속도의 fundamental mode와 1st higher mode 를 동시에 사용했을 때, 공간적 해상도가 가장 좋았다. 이연구는 천부 지반의 S파 속도 구조를 구하는데, 군속도의 higher mode를 포함한 군속도 분산곡선을 사용하는 것이 효과적임을 시사한다.

• 전자공학회논문지A
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• 제32A권12호
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• pp.91-100
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• 1995

This paper represents the lateral first-order mode characteristics for the semiconductor laser diodes using a two-dimensional numerical simulator. In order to analyze the lateral first-order mode characteristics, Helmholtz wave equation is solved twice for the lateral fundamental and the first-order mode considering the mode gain, total losses, and the recombination rate due to the stimulated emission radiation for the each mode independantly. Through this procedure, we find that the lateral first-order mode was easily guided as increasing the stripe width for the index-guiding structures, and that the lateral first-order mode seems to be dominated in the distribution of total light intensity when its output power reaches nearly half of that of the lateral fundamental mode. This results may be used to design the device structure which guides only the lateral fundamental mode.

• 전기전자학회논문지
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• 제24권3호
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• pp.727-734
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• 2020

본 논문은 과도 고장을 가지는 비동기 순차 머신에 대한 내고장성 교정 제어를 다룬다. 본 논문에서 다루는 고장은 머신이 과도 상태 천이를 거칠 때 발현할 수 있으므로 비-기본 모드(non-fundamental mode)에서 원하지 않는 상태 천이를 일으킨다. 본 논문에서는 비동기 순차 머신의 비-기본 모드에서 발생하는 과도 고장을 탐지하고 극복할 수 있는 새로운 내고장성 제어 시스템을 제안한다. 교정 제어 이론의 틀 안에서 내고장성 제어기의 존재 조건과 설계 과정을 제시한다. 또한 제안된 제어 시스템의 효용성을 검증하기 위해 FPGA 실험을 실시한다.

• ETRI Journal
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• 제32권2호
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• pp.339-341
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• 2010

The fundamental transverse mode lasing of a hybrid laser diode is a prerequisite for efficient coupling to a single-mode silicon waveguide, which is necessary for a wavelength-division multiplexing silicon interconnection. We investigate the lasing mode profile for a hybrid laser diode consisting of silicon slab and InP/InGaAsP deep ridge waveguides. When the thickness of the top silicon is 220 nm, the fundamental transverse mode is lasing in spite of the wide waveguide width of $3.7{\mu}m$. The threshold current is 40 mA, and the maximum output power is 5 mW under CW current operation. In the case of a thick top silicon layer (1 ${\mu}m$), the higher modes are lasing. There is no significant difference in the thermal resistance of the two devices.

• 한국소음진동공학회논문집
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• 제24권10호
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• pp.780-787
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• 2014

This paper experimentally deals with the vibration characteristics of flat ring transducers used for ultrasonic sensors and actuators. Radial vibration mode, which is the fundamental mode of a thin piezoelectric transducer, was measured by a laser in-plane vibrometer. An impedance analyzer was used to measure natural frequencies. The results measured by experiments verified theoretical predictions. The vibration characteristics of ring transducers were identified according to the outer diameter size. The shape of the fundamental mode is almost uniform but slightly decreases from the inner to the outer circumferential surfaces. The natural frequency of the fundamental mode decreases as the outer diameter increases. It appears that the ring type transducer is suitable to excite uniformly distributed vibration on a flat surface.

• Steel and Composite Structures
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• 제6권6호
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• pp.513-529
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• 2006

This paper deals with the dynamic behaviour of cold-formed steel hollow frames with different connection stiffnesses. An analytical model of a semi-rigid frame was developed to study the influence of connection stiffnesses on the fundamental frequency and dynamic response of the frames. The flexibilities of the connections are modeled by rotational springs. Neglect of semi-rigidity leads to an artificial stiffening of frames resulting in shorter fundamental period, which in turn results in a significant error in the evaluation of dynamic loads. In the seismic design of structures, of all the principal modes, the fundamental mode of translational vibration is the most critical. Hence, experiments were conducted to study the influence of the connection stiffnesses on the fundamental mode of translational vibration of the steel hollow frames. From the experimental study it was found that the fundamental frequency of the frames lie in the semi-rigid region. From the theoretical investigation it was found that the flexibly connected frames subjected to lateral loads exhibit larger deflection as compared to rigidly connected frames.

• 비파괴검사학회지
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• 제30권6호
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• pp.539-547
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• 2010

In this study, characteristics of the fundamental longitudinal guided wave mode, L(0,1), which is a usual mode employed in the inspection of the above-ground pipe, of the buried pipe were numerically investigated considering property changes in the surrounding soil. Results showed that soil conditions are significantly affecting the attenuation of L(0,1) mode in the pipe embedded in soil. Especially, if the soil is partially saturated, the attenuation of L(0,1) mode is larger and is very similar regardless of the degree of water saturation in the surrounding soil. However, when the soil is fully saturated, the attenuation of L(0,1) mode is less and show different trend with its partially saturated counterparts.

• 한국전자통신학회논문지
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• 제17권3호
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• pp.399-408
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• 2022

본 논문에서는 기본 모드 원리를 침해하는 과도 고장이 존재하는 입력/출력 비동기 순차 회로의 내고장성 교정 제어 시스템을 제안한다. 비동기 순차 회로의 과도 천이 과정에서 발생하는 비-기본 모드 고장을 극복하기 위해서는 고장에 의한 상태 천이가 종료되는 시점을 알아야 하며, 회로를 고장 상태로부터 원래 도달해야 하는 상태와 출력 등가적인 상태로 보내기 위한 교정 동작을 구현해야 한다. 본 논문에서는 이러한 고장 탐지 및 극복을 구현할 수 있는 출력 피드백 교정 제어기의 존재 조건을 규명한다. FPGA 실험을 통해 제안된 제어 시스템의 설계 과정을 제시하고 응용 가능성을 검증한다.

• 대한기계학회논문집A
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• 제24권4호
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• pp.916-925
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• 2000

Perhaps, this is the first attempt which applies the wavelet transform to the fundamental vibration mode for damage detection in a beam. Contrary to most existing detection methods on mode shapes, the present method directly works only with the fundamental mode of a damaged beam: no vibration mode shape of a undamaged beam is necessary. Applying the concept of vanishing moments of wavelet functions, we show that wavelet functions are effective damage detectors. Both numerical and experimental results confirm the effectiveness of the present method.

• Earthquakes and Structures
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• 제18권2호
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• pp.263-273
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• 2020

The use of energy concepts in seismic analysis and design of structures requires the understanding of the input energy response of multi-degree-of-freedom (MDOF) systems subjected to strong ground motions. For design purposes and non-time consuming analysis, however, it would be beneficial to associate the input energy response of MDOF systems with those of single-degree-of-freedom (SDOF) systems. In this paper, the theoretical formulation of energy input to MDOF systems is developed on the basis that only a particular portion of the total mass distributed among floor levels is effective in the nth-mode response. The input energy response histories of several reinforced concrete frames subjected to a set of eleven horizontal acceleration histories selected from actual recorded events and scaled in time domain are obtained. The contribution of the fundamental mode to the total input energy response of MDOF frames is demonstrated both graphically and numerically. The input energy of the fundamental mode is found to be a good indicator of the total energy input to two-dimensional regular MDOF structures. The numerical results computed by the proposed formulation are verified with relative input energy time histories directly computed from linear time history analysis. Finally, the elastic input energies are compared with those computed from time history analysis of nonlinear MDOF systems.