• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1644-1654
• /
• 2018

Eigenvalue distributions for a periodic metal-insulator-metal waveguide, classified into the point spectrum and the discretized continuous spectrum (DCS), are investigated as functions of frequencies, gap widths, and periods. Muller's method is suggested for solving exact eigenvalues, and we propose the scheme for finding proper initial values in the Muller's method by considering only ${\Re}e({\varepsilon}_r)$ in the dispersion equation. We then find that anti-crossing behavior, repulsive effect between the point spectrum and the DCS, becomes stronger when the real parts of the roots in the point spectrum have smaller values. Finally, we examine the transmittances of a single subwavelength slit for real metals using the mode matching technique. The transmittances in real metals similarly follow those of the perfect electric conductor (PEC) at low frequencies, while the patterns at higher frequencies begin to differ from the PEC.

• 한국통신학회논문지
• /
• 제26권11B호
• /
• pp.1607-1611
• /
• 2001

매우 짧은 펄스를 이용한 40-Gb/s 광전송의 성능과 전송용 광섬유의 색 분산과의 관계를 컴퓨터 시뮬레이션을 사용하여 연구하였다. 매우 짧은 펄스를 사용할 경우 펄스매우 짧은 펄스를 이용한 40-Gb/s 광전송의 성능과 전송용 광섬유의 색 분산과의 관계를 컴퓨터 시뮬레이션을 사용하여 연구하였다. 매우 짧은 펄스를 사용할 경우 펄스의 넓은 스펙트럼이 광섬유의 색분산과 어우러져서 광섬유의 비선형성에 의한 신호의 왜곡이 억제된다. 이러한 억제의 정도는 광섬유의 색분산, 광신호의 세기 그리고 전송거리 등에 의해 복합적으로 결정된다. 3ps의 길이를 갖는 펄스가 사용되었을 경우 장신호의 세기가 너무 높지 않을 때, 눈 잠김 페널티는 광섬유의 색분산이 D=4ps/nm/km일 경우 가장 컸으며 그 양쪽으로 패널티는 줄어들었다.

• 대한전자공학회논문지
• /
• 제26권7호
• /
• pp.98-105
• /
• 1989

본 논문에서는 생체 조직을 정량화하기 위한 음속의 측정법을 제안하였다. 기존의 음속 측정법에서는 주파수 분산의 영향이 무시되고 있으나, 주파수 분산은 전파 지연에 영향을 미친다. 따라서 진폭 스펙트럼으로부터 최소 위상 스펙트럼을 유도하여 주파수 분산을 정량화하였으며, 주파수 분산을 제거하기 위한 신호 분해법을 제안하였다. 또한 컴퓨터 시뮬레이션을 통하여 제안된 이론의 유효성분을 확인하였다.

• 한국정밀공학회지
• /
• 제31권9호
• /
• pp.805-811
• /
• 2014

In this investigation, we constructed and demonstrated a simple Yb-doped fiber laser, of which longitudinal modes are mode-locked without any additional devices to compensate the dispersion caused by optical components. Non-linear polarization rotation (NPR) was adopted for the mode-locking mechanism and a polarization controller (PC) was used for a kind of spectral filters to restrict the bandwidth for mode-locking. As the result, the laser was successfully operated as mode-locked with the repetition rate of 42.2 MHz and the spectrum was broadened up to approximately 16 nm at 1033 nm center wavelength when the laser was mode-locked. In this paper, the operation of the developed Yb-doped mode-locked laser is explained with the concept of Lyot filter realized by a PC, which enables mode-locking under normal dispersion. In the industrial applications, this laser can be used as a seed laser of the high power lasers for optical manufacturing.

• 천문학논총
• /
• 제32권1호
• /
• pp.343-345
• /
• 2017

We present the development of a spectral dispersion device for wideband spectroscopy for which the primary scientific objective is the characterization of transiting exoplanets. The principle of the disperser is simple: a grating is fabricated on the surface of a prism. The direction of the spectral dispersion power of the prism is crossed with the grating. Thus, the prism separates the spectrum into individual orders while the grating produces a spectrum for each order. In this work, ZnS was selected as the material for the cross disperser, which was designed to cover the wavelength region, ${\lambda}=0.6-13{\mu}m$, with a spectral resolving power, $R{\geq}50$. A disperser was fabricated, and an evaluation of its surface was conducted. Two spectrometer designs, one adopting ZnS (${\lambda}=0.6-13{\mu}m$, $R{\geq}300$) and the other adopting CdZnTe (${\lambda}=1-23{\mu}m$, $R{\geq}250$), are presented. The spectrometers, each of which has no moving mechanical parts, consist simply of a disperser, a focusing mirror, and a detector.

• 한국인터넷방송통신학회논문지
• /
• 제14권3호
• /
• pp.43-49
• /
• 2014

마크-젠더 변조기와 저역 통과 필터를 사용하여 광 듀오바이너리 신호를 생성하는 광 듀오바이너리 송신기의 전송 특성을 40Gbps에서 이론적으로 분석하였다. 광 듀오바이너리 시스템의 전송 성능은 송신기를 구성하는 저역 통과 필터와 광 필터 그리고 수신기내 필터의 대역폭에 따라 차이를 보였으며 각 필터들은 광 파워 스펙트럼에 각기 다른 영향을 주었다. 필터들의 최적화된 대역폭을 선택함으로써 광 듀오바이너리 신호 전송 시 부엽 발생과 리플을 억제시키고 분산 내성을 개선 할 수 있었다.

• 한국해양공학회지
• /
• 제27권6호
• /
• pp.100-105
• /
• 2013

This paper presents a sea surface reconstruction method that uses measured radar images by applying filtering techniques and identifying wave characteristics of the surrounding the Ieodo ocean research station using WaveFinder (X-band wave measurement radar), which is installed in the station. In addition, the results obtained from real radar images are used to verify the reconstructed sea surface. WaveFinder is a marine system that was developed to measure wave information in real time. The WaveFinder installed in the station could acquire sequent images for the sea surface at constant time intervals to obtain real time information (Wave height, mean wave period, wave directionality, etc.) for the wave by getting a three-dimensional spectrum by applying an FFT algorithm to the acquired sequent images and wave dispersion relation. In particular, we found the wave height using the SNR (Signal to noise ratio) of the acquired images. The wave information measured by WaveFinder could be verified by comparing and analyzing the results measured using the wave measurement instrument (Sea level monitor) in the station. Additionally, the wave field around the station could be reconstructed through the three-dimensional spectrum and the inverse FFT filtering from the analyzed results for the measured radar images. We verified the applicability of the sea surface reconstruction method by comparing the measured and simulated sea surfaces.

• 천문학논총
• /
• 제8권1호
• /
• pp.33-45
• /
• 1993

The variation of instrumental profile for the different scan speed of PDS is estimated as FWHM of the assumed Gaussian Profile. The effects of scan speed and scan aperture of PDS on the objective prism spectrum analysis are investigated for 8 combinations of scan speed and scan aperture. Amomg them. D1 apture with 15 csu is found to be the most optimum choice for measuring KISO objective prism film. We suggest the preliminary test study of the scan speed and aperture for the optimum use of PDS for any massive scan of spectra. The optimum scan speed and aperture depends on the dispersion of spectrum as well as the type of phtographic emulsion.

• Earthquakes and Structures
• /
• 제15권4호
• /
• pp.443-452
• /
• 2018

In this paper the new intensity measures (IMs) for probabilistic seismic analysis of RC high-rise buildings with core wall structural system are proposed. The existing IMs are analysed and the new optimal ones are presented. The newly proposed IMs are based on the existing ones which: 1) comprise a wider range of frequency velocity spectrum content and 2) are defined as the integral along the velocity spectrum. In analysis characteristics of optimal IMs such as: efficiency, practicality, proficiency and sufficiency are considered. As prototype buildings, RC high-rise buildings with core wall structural system and with characteristic heights: 20-storey, 30-storey and 40-storey, are selected. The non-linear 3D models of the prototype buildings are constructed. 720 non-linear time-history analyses are conducted for 60 ground motion records with a wide range of magnitudes, distances to source and various soil types. Statistical processing of results and detailed regression analysis are performed and appropriate demand models which relate IMs to demand measures (DMs), are obtained. The conducted analysis has shown that the newly proposed IMs can efficiently predict the DMs with minimum dispersion and satisfactory practicality as compared to the other commonly used IMs (e.g., PGA and $S_a(T_1)$). The newly proposed IMs overcome difficulties in calculating of integral along the velocity spectrum and present adequate replacement for IMs which comprise a wider range of frequency velocity spectrum content.

• 대한기계학회논문집B
• /
• 제40권2호
• /
• pp.111-117
• /
• 2016

본 연구의 목적은 실리콘 열전달 조절을 위한 포논의 평균자유행로(Mean free path, MFP) 스펙트럼 열전달 기여도 예측이다. 열전달의 크기 효과는 포논의 MFP 와 재료의 특성길이가 비슷할 때 나타나는데, 나노시스템 응용을 위한 재료의 열전달 증감을 위해 포논 MFP 스펙트럼에 대한 열전달 기여도 예측이 중요하다. 이를 위해 포논의 주파수 의존성이 고려된 볼츠만 수송방정식(Boltzmann transport equation) 근간의 full phonon dispersion 모델을 통해 실리콘 박막(Silicon-on-Insulator) 트랜지스터의 실리콘 박막 두께 변화(41-177 nm)에 따른 포논 MFP 스펙트럼 열전달 특성 및 비등방성을 해석함으로써, 본 연구 결과는 향후 박막 트랜지스터에 대한 고효율 열소산(heat dissipation) 설계전략에 활용될 수 있다.