• Progress in Superconductivity and Cryogenics
• /
• v.15 no.1
• /
• pp.11-13
• /
• 2013

We have developed a terahertz time-domain spectroscopy (THz-TDS) system for transmission and reflection measurements of metallic thin films. Using our THz-TDS system, we studied the conventional superconductor niobium (Nb) in the normal state in the spectral range from 5 to $50cm^{-1}$. Both the real and imaginary parts of the conductivity are acquired without Kramers-Kronig analysis. Nb exhibits a nearly frequency independent real conductivity spectrum in the terahertz range, with a very small imaginary part.

• Proceedings of the KIEE Conference
• /
• 1999.07e
• /
• pp.2459-2461
• /
• 1999

FDTD(Finite-Difference Time-Domain) 방법을 이용하여 마이크로웨이브 오븐 내부 전자파를 해석하였고, 열전달방정식을 이용하여 부하의 열 분포를 해석하였다. 다양한 형태의 오프닝구조를 갖는 캐비티에 관하여 수치계산을 수행하였고, 서로 다른 종류의 부하가 존재할 때 부하의 온도 분포가 어떻게 변화하는지 알아보았다. 또한 마그네트론의 안테나와 캡이 존재하는 실제 웨이브가이드를 모델링하여 수치 계산한 후, 적외선사진에 의한 부하의 온도분포와 비교하였다.

• Journal of Digital Contents Society
• /
• v.10 no.3
• /
• pp.389-393
• /
• 2009

In this paper, the single patch microstrip antenna and gap coupled broadband microstrip patch antenna using FDTD(Finite Difference Time Domain method) are analyzed. Mur's 2nd absorbing boundary condition to minimize reflected wave is applied. Return loss, voltage standing wave ratio, and input impedance by the length and width of driving patch, the length and width of parasitic patch, and the distance between driving patch and parasitic patch have been analyzed. Design parameters and radiation patterns of broadband antenna have been also shown.

• Journal of Families and Better Life
• /
• v.17 no.1
• /
• pp.167-178
• /
• 1999

The purpose of this study were to 1) classify the domain according to the level f housework sociaklization and 2) illuminate the determinants on it. The subjects of this study were 564 married women living in Seoul. A questionnaire was used as survey method. Frequenciaes percentiles mean and regression were employed for data analysis. major findings were as follows; 1) The domain according to the level of housework socialization were purchases of storage food convemience food dining-out clothes repairing services and laundry wervices 2) Of market goods characteristics quality and time-saving characteristics were influencing variables in the level of storage food purchases. The affecting variables in the level of convenience food purchases dining-out and clothes repairing services purchases was quality of market goods. In the level of laundry services time-saving characteristics was significant.

• Journal of the Semiconductor & Display Technology
• /
• v.1 no.1
• /
• pp.1-7
• /
• 2002

Modem technology depends on the reliability of extremely high precision equipments. In the production of semiconductor wafer, optical and electron microscopes, ion-beam, laser device must maintain their alignments within a sub-micrometer. This equipment requires a vibration free environment to provide its proper function. Therefore, this high technology equipments require very strict environmental vibration criteria because it is used as basic data for the design of building structure and structural dynamics of equipment. In this paper, the new approach is proposed to investigate the mismatch problem of time and frequency domain for vibration criteria of sensitive equipment. The proposed approach is based on a vibration measurement data and a relative transfer function which can be obtained by experiment or analysis.

• Smart Structures and Systems
• /
• v.17 no.1
• /
• pp.59-72
• /
• 2016

The Impact Echo method can be used to measure the thickness of concrete plate like structures. Measurements are based on the identification of a clear thickness resonance frequency which can be difficult in very thick or highly attenuative plates. In this study the detectability of the measured resonant frequency is enhanced by time domain summation of signals with different source receiver spacing. The proposed method is based on the spatial and temporal properties of the first higher symmetric zero group velocity Lamb mode (S1-ZGV) which are described in detail. No application dependent tuning or filtering is needed which makes the method robust and suitable for implementation in automatic IE thickness measurements. The proposed technique is exemplified with numerical data and field data from a thick concrete wall and a highly attenuative asphalt concrete layer.

• Korean Journal of Optics and Photonics
• /
• v.12 no.6
• /
• pp.479-484
• /
• 2001

The analysis of photonic band gaps and anomalous dispersion phenomena in photonic crystals requires understanding of band structures and dispersion surfaces. We show the results of the calculation of band structures and dispersion surfaces for a few two- dimensional lattices, using the finite-difference time-domain method with periodic boundary conditions. In addition, localized defect modes the exist within the band gap are computed by the same method.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.10 no.16
• /
• pp.39-51
• /
• 1987

This paper deals with the case analysis of second order processes under sampled-data. Proportional Integral-Derivative(PID) control, and development of Decision Support Systems(DSS) for such processes. In this paper three techniques were described for identifying the dynamics of closed loop stable processes. The first, called pulse testing is a frequency-domain method, which yields the frequency response diagram of an open loop process. The second is a time-domain method which yields the gain and time constants of the process model. The third technique is based on step response and gives the parameters of PID controllers. The development of DSS design programs consisting of above three techniques will provide very powerful tools in the microcomputer based process control.

• Journal of the Society of Naval Architects of Korea
• /
• v.46 no.2
• /
• pp.105-113
• /
• 2009

A theoretical study on the pressure fluctuation induced by a propeller was carried out in this study. The main objective of this study is to analyze the source mechanism of the pressure fluctuation induced by propeller sheet cavitation. To analyze the pressure fluctuation induced by propeller sheet cavitation, modern acoustic theory was applied. Governing equation of pressure fluctuation induced by sheet cavitation was derived using Ffowcs Williams proposed time domain acoustic approaches. Several factors affecting pressure fluctuation were analyzed based on the derived governing equation. Pressure fluctuation result was represented by combined results of the far field term and near field term. Finally, the physical mechanism of pressure fluctuation at the blade rate frequency was analyzed using numerically generated cavitation volume variation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.9 no.3
• /
• pp.378-385
• /
• 1998

A three-dimensional finite difference time domain (3-D FDTD) algorithm of calculation for the characteristics of coaxial-to-cavity filter including a discended probe and a tuning post is presented. In the arrangement the inner coaxial conductor protrudes into the cavity and operates as a probe radiator. And the height of the rectangular tuning post determines the resonant frequency. The validation of this method is confirmed by comparing the calculated values with experimental results for the designed filter.