• Tunnel and Underground Space
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• v.20 no.2
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• pp.112-118
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• 2010

Before blasts that can have direct impacts on human bodies or structures, it is necessary to assess impacts of ground vibration. Therefore, frequency has been recognized as an important factor in order to assess impact on ground vibration and damages. There have been many studies on impacts of frequency. But, there have been no studies on relations between vibration and frequency according to delay time difference. In this study, we examined the relations between delay time difference and frequency according to each frequency with which reinforcement and destructive intervention repeat through delay time difference obtained using superposition modeling of single hole blasting waveform based on the theory of time difference developed by Langefors.

• Plant Journal
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• v.16 no.4
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• pp.40-44
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• 2020

In this study, after supplying a pulse wave to the 2 V Industrial Lead-Acid Battery electrode plate and repeating the charging and discharging, the discharging time per voltage was analyzed. According to the result of experiment, while the lead-acid Battery that a pulse wave is not supplied decreased about 18 % of discharging capacity than the beginning, the lead-acid Battery that a pulse wave is supplied decreased a little amount much lower than 18 %, of discharging capacity and recorded the 0.56 % decrease, at a minimum, from discharging capacity at the 20 kHz frequency. This means that the sulfate on electrode plate is detached and the positive and negative charge transfer is highly activated at the 20 kHz frequency

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.166-167
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• 2017

가상 현실에 대한 관심이 높아지면서, 가상 물체와 사람 사이의 보다 자연스러운 상호작용이 중요하게 되었다. 그 중 가장 많이 사용되는 방식 중 하나가 바로 손동작이다. 사람들은 손동작을 통해 자신의 감정을 전달하거나 자신의 의견을 표현할 수 있기 때문에 손동작은 Natural User Interface(NUI)의 중요한 위치를 차지하고 있다. 본 논문에서는 사람들의 손동작 중 비교적 큰 비중을 차지하는 반복적인 궤적을 그리는 손동작 인식을 위한 방법을 제안한다. 손이 움직이는 방향과 거리의 3 차원 좌표 값을 이용하여 벡터화를 한 후, 이 데이터를 Fast Fourier transform(FFT)와 Support Vector Machine(SVM)을 통해 반복적인 손동작을 인식함으로써 자연스러운 손동작을 비교적 정확히 인식할 수 있다.

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.403-405
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• 2003

An iterative Green's function method (IGFM) is introduced to analyze complex electromagnetic waveguide structures in view of the university student. The IGFM utilizes the Green's function and iteration scheme. The physical mechanism with simple mathematical equations is used to formulate the IGFM. Scattering characteristics of a standard E-plane T-junction in a parallel-plate waveguide are theoretically investigated in terms of the IGFM. Numerical computations illustrate the characteristics of resection and transmission powers versus frequency. A dominant-mode solution is presented and compared with the higher-mode solutions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.5
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• pp.437-443
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• 1988

We calculate the distribution of the current on the strip by the incident waves on the infinite conducting strip line. The boundary equations represented as the spatial domain function become very complicated equations including convolution integral. Transformed it to the spectral domain, we have a very simple equation is composed by some algebraic multiplication of the current density function and Green's function. the acceleration of iteration procedure is achieved by Kastner's method. The result of iteration gives us the optimum value when it satisfies the iteration stop condition presented in this paper. We confirmed that the induced current density distribution on the stripline has been changed as variaties of the width.

• Journal of the KSME
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• v.28 no.4
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• pp.313-321
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• 1988

어떤 구조물이 반복하중을 받으면 피로파괴를 일으킨다. 만일 이 구조물이 부식환경 속에 앗 으면 불활성 분위기나 공기 중에서 보다 빨리 파괴에 이르게 된다. 이러한 현상을 흔히 부식 피로라고 한다. 부식피로에 크게 영향을 미치는 변수들을 대략 기계적 변수, 금속학적 변수, 환경 변수로서, 기계적 변수에는 최대응력 확대계수, 응력확대계수범위, 응력비, 반복하중 주파수, 반복하중파형, 응력상태, 잔류응력, 균열의 크기 및 모양 등이 있으며 금속학적 변수로는 합금 조성, 합금원소와 불순물의 분포, 미세조직과 결정구조, 열처리, 소성가공, 집합조직 등이며 환 경변수에는 온도, 환경의 형태(기체, 액체), 부식성분의 분압 또는 농도, 전기화학적 전위, pH, 수용성 환경의 점성, 피복, 부식억제제 등이 있다. 이와 같이 부식환경 속에 있는 구조물의 파 손을 이해하기 위하여는 응력부식과 부식피로를 공부하여야 한다. 이 현상은 매우 복잡한 문 제이기 때문에 아직도 완전히 이해되지 않은 상태이고 따라서 중요한 연구대상이 되고 있다. 여기서는 응력부식과 부식피로의 파괴역학적인 측면을 소개하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1832-1838
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• 2009

In this paper, we present new signal de-interleaving method for the frequency agility radar in which the carrier frequency is changed irregularly. Generally radar use a fixed carrier frequency, and it is easy for electronic warfare system to de-interleave the radar signal with respect to the frequency, pulse width(PW), and direction of signal arriving(DOA). In frequency agility radar, it is difficult to de-interleave the radar signals according to the carrier frequency because the frequency is changed irregularly. We suggest a good de-interleaving method to identify the frequency agility radar signals in comparison with PRI's of radars. First we calculate pulse repeat Interval(PRI) of radar in linked-list and queue structure and de-interleave the radar signals with PRI, PW, and DOA, then identify the frequency agility radar. When we use the proposed algorism to the frequency agility radar, we have a good de-interleaving results with electronic warfare systems.

• The Journal of the Acoustical Society of Korea
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• v.31 no.1
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• pp.11-18
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• 2012

In this paper, the occurrence of a stopband phenomenon when an acoustic wave propagates through periodically corrugated ducts is discussed using theoretical and BEM analyses. A 2-D duct with sinusoidally corrugated upper and lower walls is considered. When the magnitude of the sinusoidal corrugation is sufficiently small compared to the duct's height, the wave equation is solved with the multiple scaling perturbation method. Then stopbands for Bragg and non-Bragg resonances are computed from the condition where frequency becomes a complex number. A 2-D BEM analysis is performed to compute insertion loss of the duct, and stopbands are confirmed as predicted by analytical analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.252-259
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• 2019

Jet engine modulation(JEM) signals are widely used in the field of target recognition along with high-range resolution profile and inverse synthetic aperture radar because they provide specific information of the jet engine. To obtain the number of blades of the jet engine, the chopping frequency proportional to the number of blades must be extracted. In the conventional chopping frequency extraction method, an initial threshold value is defined and a method of detecting the chopping peak is used. However, this detection method takes time depending on the signal due to repetitive detection. Thus, in this study, we proposed to extract the chopping frequency using MUltiple SIgnal Classification(MUSIC) algorithm. We applied the MUSIC algorithm to a given JEM signal to find the chopping frequency and determine the blade number candidates. We also applied the MUSIC algorithm to other chopping frequency extractions to determine the score of the candidate groups. Unlike the conventional detection algorithm, which requires repetitive frequency detection, MUSIC algorithm quickly detects the accurate chopping frequency and reduces the calculation time.

• Annual Conference of KIPS
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• 2005.05a
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• pp.171-174
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• 2005

의료기기의 디지털화로인해 의료영상분야도 디지털화되고 있다. 본 논문에서는 의료영상에서 발생하는 기하학적 변형에서도 개인정보를 인증할 수 있는 디지털 워터마킹을 제안한다. 제안한 방법은 디지털 영상을 주파수 공간으로 변환시킨 후 효과적인 워터마크 삽입을 위해 인간의 감지능력이 떨어지는 주파수 영역과 중요한 주파수 영역을 선택하였다. 그 다음 영상 전체에 반복적이며, 그 내용에 따라 적응적인 워터마크를 삽입하는 방법을 제시하였다.