• 한국실내디자인학회논문집
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• 제25권1호
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• pp.73-80
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• 2016

Street is the most fundamental component of city and place to promote diverse actions of people. Pedestrians gaze at various street environments. A visual gaze means that there are interesting elements and these elements need to be preferentially improved in the street environment improvement project. Therefore, this study aims to set up the priorities of street environment components by analyzing eye movements from a pedestrian perspective. In this study, street environment components were classified into road, street facility, building(facade) and sky and as street environment images, three "Streets of Youth" situated in Gwangbok-ro, Seomyeon and Busan University of Busan were selected. The experiment targeted 30 males and females in their twenties to forties. After setting the angle of sight through a calibration test, an eye-tracking experiment regarding the three images was conducted. Lastly, the subjects were asked to fill in questionnaires. The following three conclusions were obtained from the results of the eye-tracking experiment and the survey. First, building was the top priority of street environment components and it was followed by street facility, road and sky. Second, as components to be regarded as important, fast 'Sequence', many 'Fixation Counts' and 'Visit Counts', short 'Time to First Fixation' and long 'Fixation Duration' and 'Visit Duration' were preferred. Third, after voluntary eye movements, the subjects recognized the objects with the highest gaze frequency and the lowest gaze frequency.

• 비파괴검사학회지
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• 제19권2호
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• pp.85-92
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• 1999

비선형 음향효과를 계측함에 의해서 재료열화를 평가하는 연구는 오래 전부터 있어 왔다. 여기서, 비선형 음향효과를 계측하는 가장 일반적인 방법은 전파된 수신 신호에서 기본주파수 성분과 2차 고조파 성분의 절대적인 크기를 계측하는 것이다. 이 목적을 위해서 일반적으로 파워스펙트럼 해석법이 널리 사용되어 왔다. 그러나, 파워스펙트럼은 신호처리 후에도 주파수 영역에서 가우스 잡음이 혼재한다는 단점이 있다. 게다가, 비선형 효과에 의해서 발생되는 2차 고조파 성분의 크기는 너무 작아서 잡음에 묻혀버릴 수도 있다. 본 논문에서는, 이 문제를 해결하기 위해서 주파수 영역에서 가우스 잡음을 제거할 수 있는 바이스펙트럼 해석법을 제안하였다. 시뮬레이션을 통하여 잡음이 크게 혼재된 신호에서도 참 값에 가까운 비선형 파라미터를 구할 수 있음을 밝혔다. 또한, 실제 경우에 이 방법의 유용함을 확인하기 위하여 피로 하중에 의해서 고의로 열화시킨 여러 시편에 대하여 파워스펙트럼과 바이스펙트럼을 구하여 비교하였다.

• 비파괴검사학회지
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• 제37권1호
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• pp.7-12
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• 2017

음향 비선형 파라미터는 입사시킨 기본주파수 성분의 변위 진폭 크기와 재료의 비선형성에 의하여 발생된 2차 고조파 성분의 변위 진폭 크기의 비로 정의된다. 본 연구에서는, 압전소자 방식을 이용한 초음파 절대변위진폭 측정의 타당성을 확인하고자, 이 기법을 통해 초음파가 입사된 SUS316 시편의 절대변위진폭을 측정하였다. 또한 비교를 위해, 레이저를 통한 패브리패럿 방식의 간섭계를 이용하여 동일 시편에 대한 절대변위진폭을 측정하였다. 두 가지 기법을 통한 실험 결과는 서로 잘 일치하는 경향을 보였으며, 특히 압전형 수신 기법의 경우 기존의 레이저 변위측정기법에 비하여 반복 측정의 안정성이 우수한 것으로 나타났다. 이 결과로부터 압전형 수신 기법은 기존 레이저 측정 기법에 비하여 과정이 복잡하지만, 미세변위를 더 안정적으로 측정할 수 있어 음향 비선형 파라미터의 측정에 유리할 것으로 기대된다.

• 한국전자파학회논문지
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• 제19권7호
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• pp.771-777
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• 2008

본 논문에서는 변형된 시간 지연 기법을 이용한 마이크로파 2차 주파수 체배기가 제안되었다. 제안된 주파수 체배기에서는 입력 신호와 지연된 신호 사이에 발생하는 군지연 시간 부정합을 전압 제어 지연 선로(VCDL)를 이용하여 보상하였다. 가변 슈미트 트리거를 이용한 군지연 시간 정합과 신호 파형의 성형(waveform shaping)으로 인해 원하지 않는 기본 주파수($f_0$)와 3, 4차 고조파 성분들이 충분히 제거할 수 있었다. 결과적으로 출력 단자에서는 오직 2 체배된 주파수 성분($2f_0$)만이 우세하게 나타난다 제안된 주파수 체배기는 1.15 GHz의 기본 주파수에서 설계되었고 TSMC 0.18 $\mu m$ 공정을 이용하여 제작되었다. 입력 신호 전력을 0 dBm 인가하였을 때, 2차 체배된 출력 주파수 성분의 측정된 전력은 2.57 dBm이었다. 2차 체배된 주파수 성분에 대해 $f_0,\;3f_0$, 그리고 $4f_0$ 성분의 제거율은 각각 43.65, 38.65, 그리고 35.59 dB이다.

• Journal of electromagnetic engineering and science
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• 제3권1호
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• pp.1-6
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• 2003

In this paper, a sub-harmonic dual-gate FET mixer is suggested to improve the isolation characteristic between LO and RF ports of an unbalanced mixer. The mixer was designed by using single-gate FET cascode structure and driven by the second harmonic component of LO signal. A dual-gate FET mixer has good isolation characteristic since RF and LO signals are injected into gatel and gate2, respectively. In addition, the isolation characteristic of a sub-harmonic mixer is better than that of a fundamental mixer due to the large frequency separation between the LO and RF frequencies. As RF power was -30 ㏈m and LO power was 0 ㏈m, the designed mixer yielded the -47.17 ㏈m LO-to-RF leakage power level, 10 ㏈ conversion gain, -2.5 ㏈m OIP3, -12.5 ㏈m IIP3 and -1 ㏈m 1 ㏈ gain compression point. Since the LO-to-RF leakage power level of the designed mixer is as good as that of a double-balanced mixer, the sub-harmonic dual-gate FET mixer can be utilized instead.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.611-614
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• 1991

In variable speed driving system of three phase induction motor controlled by an inverter, because of the switching of semiconductor devices in inverter, an appreciable amount of harmonic components of voltage waveform can cause the motor to generate losses, torque ripple, acoustic noise and oscillation of semiconductor devices. In this paper a new PAM type PWM inverter using IGBT is described. The output waveforms in the proposed PAM type PWM inverter are investigated both theoretiically and experimentally. The line-voltage waveform is composed of fundamental component and the sidebands of carrier frequency. The lower order harmonics are not included in the output wave form. As each inverter arm does not operate during two-thirds period, the heats, generated in the devices are reduced. That is, the size of the inverter system can he minimized because of the reduction in the heat dissipating equipment.

• 전기학회논문지P
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• 제62권1호
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• pp.12-17
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• 2013

Fault currents are expressed as a combination of harmonic components and exponentially decaying DC offset components, during the occurrence of fault in power system. The DC offset components are included, when the voltage phase angle of fault inception is closer to $0^{\circ}$ or $180^{\circ}$. The digital protection relay should be detected quickly and accurately during the faults, despite of the distortions of relaying signal by these components. It is very important to implement the robust protection algorithm, that is not affected by DC offset and harmonic components, because most relaying algorithms extract the fundamental frequency component from distorted relaying signal. So, In order to high performance in relaying, advanced DC offset removal filter is required. In this paper, a new DC offset removal filter, which is no need to preset a time constant of power system and accurately estimate the DC offset components with one cycle of data, is proposed, and compared with the other filter. In order to verify performance of the filter, we used collecting the current signals after synchronous machine modeling by ATPDraw5.7p4 software. The results of simulation, the proposed DC offset removal filter do not need any prior information, the phase delay and gain error were not occurred.

• 대한기계학회논문집A
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• 제23권7호
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• pp.1155-1163
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• 1999

This study deals with the vibration ride quality for passenger car when running on straight highway at the speed of 70km/h. Ten accelerations were measured at four positions, three axes each at the feet, hip, and head, and one axis at the back. Five seats that have different static sponge stiffness were used, and two subjects were participated. These accelerations were analyzed to produce the ride values such as component ride value and overall ride value. It was hard to see the difference of ride value by the change of sponge stiffness. However we could rank the ride quality by the total vibration exposed to passengers. From the transfer function between the hip and the foot, the fundamental mode was observed to be around 5.8Hz. Also the transfer function between the head and hip was studied. The optimal damping ratio of the seat was calculated according to the seat natural frequency with human weighting filter which makes the optimal damping ratio different from that without weighting filter.

• 전기학회논문지
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• 제57권9호
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• pp.1485-1490
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• 2008

This paper proposes a new Fourier transform-based phasor estimation method to eliminate the adverse influence of the exponentially decaying dc offsets when Discrete Fourier Transform (DFT) is used to calculate the phasor of the fundamental frequency component in a relaying signal. By subtracting the result of odd-sample-set DFT from the result of even-sample-set DFT, the information of dc offsets can be obtained. Two dc offsets in a relaying signal are treated as one dc offset which is piecewise approximated in one cycle data window. The effect of the dc offsets can be eliminated by the approximated dc offset. The performance of the proposed algorithm is evaluated by using computer-simulated signals and EMTP-generated signals. The algorithm is also tested on a hardware board with TMS320C32 microprocessor. The evaluation results indicate that the proposed algorithm has the stable and accurate eliminating performance even if the input signal contains two decaying dc components having different time constants.

• 전기학회논문지
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• 제57권12호
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• pp.2263-2268
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• 2008

We investigated the malfunction and destruction characteristics of microcontroller devices under high power electromagnetic(HPEM) wave by magnetron. HPEM was rated at a microwave output of 0 to 1,000 W, at a frequency of 2,450${\pm}$50 MHz and was radiated from the open-ended standard rectangular waveguide(WR-340) to free space. The influence of different reset-, clock-, data-, and power supply-line lengths has been tested. The variation of the line length was done with flat cables. The susceptibility of the tested microcontroller devices was in general much influenced by clock-, reset-, and power supply-line length, little influenced by data-line length. Further the line length was increased, the malfunction threshold was decreased as expected, because more energy couples to the devices. The surfaces of the destroyed microcontroller devices were removed and the chip conditions were investigated with microscope. The microscopic analysis of the damaged devices showed component and bondwire destructions such as breakthroughs and melting due to thermal effects. The obtained results are expected to provide fundamental data for interpreting the combined mechanism of microcontroller devices in an intentional microwave environment.