• 한국광학회지
• /
• 제16권1호
• /
• pp.103-108
• /
• 2005

Poled polymer를 사용하여 도파로구조를 제작하고 2차 비선형광학현상에 의해 제 2고조파(SHG)글 발생시켰다. 기본파와 제 2고조파 사이의 위상정합은 poled polymer의 이상분산 특성을 이용하여 기본파 도파모드(TM$_{0}$)로부터 제 2고조파 도파모드(TM$_{0}$)를 실현하였다. 이때 발생되는 제 2고조파의 power는 위상정합이 가능한 다른 모드의 기본파로부터 발생한 제 2고조파의 power보다 크게 됨을 이론적으로 확인하였고, 위상정합이 가능한 도파로를 제작하였다. 기본파로서 Ti-sapphire laser(740 nm)를 사용하여 근자외 영역의 제 2고조파(370 nm)를 관찰하였다.

• 지구물리
• /
• 제9권3호
• /
• pp.231-240
• /
• 2006

The crustal structure of the Korean Peninsula was investigated by analyzing phase velocity dispersion data of Rayleigh waves. Earthquakes recorded by three component broad-band velocity seismographs during 1999-2004 in South Korea were used in this study. The fundamental mode Rayleigh waves were extracted from vertical components of seismograms by multiple filter technique and phase match filter method. Phase velocity dispersion curves of the fundamental mode signal pairs for 14 surface wave propagation paths on the great circle in the range 10 to 80 sec were computed by two-station method. Treating the shear velocity of each layer as an independent parameter, phase velocity data of Rayleigh wave were inverted. All the result models can be explained by a rather homogeneous crust of shear-wave velocity increasing from 2.8 to 3.25 km/sec from top to about 33 km depth without any distinctive crustal discontinuities and an uppermost mantle of shear-wave velocity between 4.55 and 4.67 km/sec. Our results turn out to agree well with recent study of Cho et al. (2006 b) based on the analysis of seismic background noises to recover short-period (0.5-20 sec) Rayleigh- and Love-wave group velocity dispersion characteristics.

• 대한전자공학회논문지
• /
• 제23권6호
• /
• pp.936-943
• /
• 1986

The lasing wavelengths and gain characteristics of the array modes of channel-substrate planar(CSP) lasers are presented. The gain values of array modes are determined from the complex coupling coefficients calculated using the fields of neighborig elements of the array. The computations show that for index guided lasers which have fields that are almost real valued, or have only slight phase curvature, the highest order array mode will have preferred oscillation. The inphase or fundamental mode, which produces only one major lobe in the far-field radiation pattern, will have the lowest modal gain of all array modes. Some of the devices discussed have modal gain differences of less than 10 cm**-1 between the highest and fundamental modes. For optical field confinement factors of about 20%, this gain difference corresponds to avtive layer gains of approximately 50**-1.

• Smart Structures and Systems
• /
• 제15권5호
• /
• pp.1253-1270
• /
• 2015

In this paper Magnetic Charged System Search (MCSS) and Particle Swarm Optimization (PSO) are applied to the problem of damage detection using frequencies and mode shapes of the structures. The objective is to identify the location and extent of multi-damage in structures. Both natural frequencies and mode shapes are used to form the required objective function. To moderate the effect of noise on measured data, a penalty approach is applied. A variety of numerical examples including two beams and two trusses are considered. A comparison between the PSO and MCSS is conducted to show the efficiency of the MCSS in finding the global optimum. The results show that the present methodology can reliably identify damage scenarios using noisy measurements and incomplete data.

• Nuclear Engineering and Technology
• /
• 제35권1호
• /
• pp.1-13
• /
• 2003

In this study, an effective method to estimate the fundamental frequencies of co-axial cylinders immersed in fluid is proposed. The proposed method makes use of the equivalent mass or density that is derived from the added mass matrix caused by the fluid-structure interaction (FSI) phenomenon. The equivalent mass is defined from the added mass matrix based on a 2-D potential flow theory. The theory on two co-axial cylinders extended to the case of three cylinders. To prove the validity of the proposed method, the eigenvalue analyses upon coaxial cylinders coupled with fluid gaps are peformed using the equivalent mass. The analyses results upon various fluid gap is conditions reveal that the present method could provide accurate frequencies and be suitable for expecting the fundamental frequencies of fluid coupled cylinders in beam mode vibration.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 추계학술대회 논문집
• /
• pp.259-262
• /
• 2000

In this study, 3.1$\times$3.7$\times$0.365 $\textrm{mm}^2$ model of thickness-longitudinal vibration mode VHF ceramic resonator with (Pb,Ca)(Co,W,Ti)O$_3$ ceramics was simulated by ANSYS according to the electrode size. With the variations of electrode size of the model, fundamental and the third overtone dynamic ratio was investigated. At the ratio of electrode to model thickness(1/t) 2.5, third overtone dynamic ratio was largely increased. That model is suitable for 20 MHz resonator.

• Earthquakes and Structures
• /
• 제12권4호
• /
• pp.437-448
• /
• 2017

Soft or extreme soft storeys in multi-storied buildings cause localized damage (and even collapse) during strong earthquake shaking. The presence of such soft or extremely soft storey is identified through provisions of vertical stiffness irregularity in seismic design codes. Identification of the irregularity in a building requires estimation of lateral translational stiffness of each storey. Estimation of lateral translational stiffness can be an arduous task. A simple procedure is presented to estimate storey stiffness using only properties of fundamental lateral translational mode of oscillation (namely natural period and associated mode shape), which are readily available to designers at the end of analysis stage. In addition, simplified analytical expressions are provided towards identifying stiffness irregularity. Results of linear elastic time-history analyses indicate that the proposed procedure captures the irregularity in storey stiffness in both low- and mid-rise buildings.

• 한국통신학회논문지
• /
• 제39C권4호
• /
• pp.380-386
• /
• 2014

본 논문은 Ku대역 모노펄스 위성추적을 위한 동축구조 도파관 고차모드 커플러를 제안하였다. 제안된 고차모드 커플러는 이동체 탑재용 위성추적시스템에 적용 가능하도록 소형/경량화를 위하여 동축구조의 도파관을 이용하였다. 기본모드 신호 추출을 위해 내측 원형도파관을 이용하였고, 고차모드 신호 추출을 위해 외측 원형도파관에 내어진 4개의 슬롯과 스텝 구조의 직사각형 도파관을 이용하였다. 제안된 고차모드 커플러의 모의실험 결과는 반사손실 및 삽입손실이 약 250 MHz의 대역폭(12.75~13.00 GHz)을 만족하며, 모노펄스 추적에 적용 가능한 기본모드 패턴 및 고차모드 패턴이 만족스럽게 생성된 결과를 확인하였다. 제안된 Ku대역 동축구조 도파관 고차모드 커플러는 고속 정밀추적이 요구되는 모노펄스 위성추적시스템에 이용될 것으로 기대된다.

• 한국통신학회:학술대회논문집
• /
• 한국통신학회 1984년도 추계학술발표회논문집
• /
• pp.22-24
• /
• 1984

The mode spot size is a fundamental parameter of a single mode optical fibre which determines especially the spilces and the microbending loss. The spot-size measurement is recognised to be a useful mean to define the cut-off wavelength of single-mode fibres, ESI parameters and to predict the modal dispersion. To determine the ESI parameters, this paper is based on the use of a Ronchi ruling.

• 전자공학회논문지A
• /
• 제31A권5호
• /
• pp.18-26
• /
• 1994

We express fundamental second-order and third- order harmonic distortions and intermodulation distortions in terms of the laser parameters. Compared to the Darcie `s result only limited to the high frequency (f >1GHz), these expression are quite valid in the entire modulation frequency region. It is found that the fundamental nonlinear distortions are strongly effected by the spontaneous emission to lasing mode as well as the gain compresion damping in the low frequency region.