• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.207-210
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• 2004

단판의 차음 성능 해석에 있어서 무한판과 유한판의 가장 큰 음향학적 차이는 유한한 경계에 의해 발생하는 정재파에 있다고 할 수 있다. 하지만, 일치 주파수 이하에서는 진동 공진이 발생하더라도 음향방사효율이 비교적 작고, 따라서, 비록 그 진동 응답이 크더라도 절대적인 음향 방사 양은 작다. 이를 근거로 대부분의 유한판 해석은 비공진 성분에 국한되어 왔으나, 특정 경우 공진 투과 성분을 무시하면 해석 결과에 오차가 발생할 수 있음이 제시된 바 있다. 본 연구에서는 유한 단판의 차음 해석에 있어서 공진 투과 성분의 상대적 기여도를 수치적 해석을 통해 알아보고, 이로부터 공진 투과 성분이 해석치와 측정치 사이의 정량적 상관도에 미치는 영향을 분석하였다.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.539-541
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• 2006

전력 반도체의 방열 특성은 수명 및 소손과 관계가 있다. 전력 반도체 자체의 열전달 특성 및 전력 반도체가 취부 되는 방열판의 전도, 대류, 방사의 열전달 특성을 고찰하기 위하여 본 논문에서는 실시간으로 방열판의 온도를 관측하여 전력 반도체의 손실을 확인하였고, 프로파일별 히트 싱크 온도 상승 측정 평균 전류와 전류 프로파일과 의 상관 관계를 분석 하여 방열판 최적화 및 히트 싱크 온도 관측 시 히트 싱크의 모델을 제시하였다.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.15-21
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• 2000

본 논문은 체적이 변하는 흙에 대하여 새로운 흙-수분 특성곡선 이론을 제시하고 이를 실험적으로 규명하였다. 그 결과, 점토와 같이 불포화되는 과정중 체적변형이 발생하는 흙의 흙-수분 특성곡선은 간극비와 흡인력의 함수이므로 체적변화를 무시할 수 없음이 밝혀졌다. 따라서 본 논문에서는 체적변화가 있는 경우 흙-수분특성곡선을 구하기 위하여 두가지 실험법을 채택하였다. 그 첫째는 전통적인 압력판 추출시험과, 중량함수비와 간극비와의 관계를 알 수 있는 수축한계시험을 실시하여 조합하는 방법이며, 둘째 방법은 압력판 셀을 새로인 고안하여 추출시험시에 체적 수축도 측정할 수 있는 수정된 압력판 셀 시험방법을 이용하는 것이다. 이 시험결과를 3차원 상의 면(surface)에서 표현하여, 체적변형을 고려한 흙-수분 특성을 규명할수 있도록 하였다.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.326-332
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• 1998

A laminated plate which contains debonds is visualized and evaluated nondestructively by holographic interferometry. Characteristic vibration frequencies of the plate are found in which debonds appear as anomalies in the fringe pattern for realtime holography. A set of time-average holograms for the vibrating plate are generated at various positions using a piezoelectric transducer, and the anomalies in each reconstructed hologram are enhanced through image processing. The images are added together to show the distribution of debonds for the whole area of the test plate.

• Journal of the Korean Society of Radiology
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• v.8 no.5
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• pp.265-269
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• 2014

The therapy of total body irradiation on leukemia carries out to kill harmful bacteria or suppression of immune system by external beam therapy, which is a preparatory stage to reconstitute bone marrow before a pre-treatment of bone marrow transplantation to patients with health bone marrow cells. In case of this kind of radiation therapy, the spoiler use to increase surface dose of patient which varies depending on distance and thickness between patient and spoiler. In this study, the change was investigated the surface dose according to thickness of spoiler. The 0.5% increase of surface dose was observed with each 2.0 cm when the spioler in acrylic was prepared from 0.5 cm to 3.0 cm at intervals of 0.5 cm was evaluated. Based on this result, it suggests that this kind of application will be somewhat limited on clinical trials directly but proper surface dose can be useful method when is applied on patients of treatment prognosis who are required each different surface dose.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.777-783
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• 2012

Vibration intensity has been used to identify the location of a vibration source in a vibrating system. By using vectors representation, the source of the power flow and the vibration energy transmission paths can be revealed. However, due to the large surface area of a plate-like structure, clear transmission paths cannot be achieved using the vectors representation. Experimentally, for a large surface object, the number of measured points will also be increased. This requires a lot of time for measurement. In this study, streamlines representation is used to clearly indicate the power flow transmission paths at all surface plate for FEM and experiment. To clearly improve the vibration intensity transmission paths, streamlines representation from experimental works and FEM computations are compared. Improved transmission paths visualization for both FEM and experiment are shown in comparison to conventional vectors representation. These streamlines visualization is useful to clearly identify vibration source and detail energy transmission paths especially for large surface plate-like structures. Not only that, this visualization does not need many measured point either for experiment or FEM analysis.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.281-287
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• 2001

For the conventional two-dimensional source location of acoustic emission (AE) based on the threshold crossing, wave velocity has to be measured in the actual structure to calculate the arrival-time difference and thus to form the two hyperbolae. Velocity is dependent on the fiber orientation, however, due to the dependence of elastic modulus on fiber orientation in anisotropic materials such as compost#e plates. This tan affect the accuracy of AE source location and make the source location procedure complicated. In this study, we propose a method to reduce the location error in anisotropic plates by using the numerical solution of nonlinear equations, where the velocity term has been removed by employing the fourth sensor. The efficiency and validity of the proposed method has also been experimentally verified.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.38-44
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• 2000

In this paper, we have been fabricated λ/2 phase plates lot an optical pick-up using a blue violet laser diode by employing proton exchange and wet etching in LiNbO$_{3}$. Their functions and fabrication processes are described in detail. It is established the optimal fabrication conditions through the experimental results. The device characteristics are measured by the Mach-zender interferometer which is composed of the optical components and 632.8nm He-Ne laser. The measured phase error was ＋5$^{\circ}$~ -6$^{\circ}$(within 3%). This phase plate could be applied an useful device to improve the resolution and the stability of the optical pick-up which has a blue violet laser diode as an optical source.

• Composites Research
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• v.13 no.5
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• pp.1-9
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• 2000

An intensity-based optical fiber vibration sensor is applied to monitor the structural vibration and detect impact locations on a plate. Optical fiber vibration sensor is constructed by placing two cleaved fiber end, one of which is cantilevered in a hollow glass tube. The movement of the cantilevered section lags behind the rest of the sensor in response to an applied vibration and the amount of light coupled between the two fibers is thereby modulated. For vibration sensing, optical fiber vibration sensor is mounted on the carbon fiber composite beam and its response is investigated to free and forced vibration. In impact location detection, four optical fiber vibration sensors whose location is predetermined are placed at chosen positions and the different arrival times of impact-generated vibration signal are recorded by an FFT analyzer. Impact location can be calculated from these time delays. Experimental results show that optical fiber vibration sensor signals coincide with gap sensor in vibration sensing. The precise location of impact can be detected on an acrylate plate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.1
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• pp.23-26
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• 2000

In spot welded joint. Electronic Speckle Pattern Interferometry(ESPI) method using the Model 95 Ar laser a video system and an image processor was applied to measure the stress Unlike traditional strain gauges or Moire method, ESPI method has no special surface preparation or attachments and can be measured in-plane displacement with non-contact and real time. In this experiment, specimens are loaded in parallel with a load cell. The specimens are made of the cold rolled steel sheet with 1mm thickness, are attached strain. gauges. This study Provides an example of how ESPI has been used to measure stress and strain inspecimen. The results measured by ESPI are compared with the data which was measured by strain gauge method under tensile testing.