• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.377-381
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• 2014

Coupled guided modes, proposed in various modified hollow hexagonal cavities each attached internally to a hexagon, were demonstrated by investigating the laser oscillations in semiconductor cavities. The mode spacing between two adjacent lasing peaks decreased as the size of the internal hexagon increased, due to the increased round-trip length of the coupled guided modes. The linear dependency of the inverse mode spacing to the calculated round-trip length strongly confirmed the lasing of the coupled guided modes. The proposed modes in common-sized external cavities showed resonance structure that could be adjusted widely by controlling the size of the internal hexagon.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.9
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• pp.876-883
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• 2009

The radiation of sound from a rectangular plate with a guided edge condition is investigated. By taking this particular boundary condition into account, simple analytical forms of the average radiation efficiency and radiation power based on the modal approach can be found, where the cross-modal terms can average out for all possible point excitation locations. Design variables of the plate such as thickness, aspect ratio, and damping that are closely related to the sound radiation are mainly discussed. The radiation power of the guided plate is found to be governed by the piston mode as well as the critical frequency. While both the radiation efficiency and the radiation power seem to be influenced by thickness and a large aspect ratio, damping loss factor seems less important to the radiation power. It is also shown that no clear corner and edge mode regions may be found for the guided case, unlike the pinned.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.59-63
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• 2003

Modal properties of guided waves along circular dispersive double negative (DNG) index metamaterial rod waveguides are numerically investigated. Identical forms of dispersive dielectric and magnetic material constants are used for simplicity. For degenerated azimuthally symmetric mode, a multimode region, a single mode region, a band gap region and a forbidden region are found which cannot be observed in the case of the conventional dielectric rod waveguide. As the normalized frequency goes down, discrete guided modes are continuously generated, which is a reverse property of conventional dielectric rod waveguide. Also, there are high-frequency cutoffs, which have been generally examined in dispersive circular geometries such as a plasma column or a plasma Goubau line. In the single mode region, both the low- and high-frequency cutoffs are existed where the propagation constants are continued between the guided oscillating and surface modes.

• Journal of Korean Society for Quality Management
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• v.41 no.3
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• pp.487-494
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• 2013

Purpose: In this study, we propose the precision guided munitions verification methodology using the statistical analysis method has been proposed. and it can be applied to the precision guided munitions quality assurance work. Methods: This modeling is based on Failure Mode and Effects Analysis, Statistical Process Control, Defense Quality Managerment System, Production Readiness Review, Manufacturing Readiness Assesment and so on. Results: The Process Control Modeling that has the following procedures ; searching the critical to quality, statistical analysis by process, verify process. Moreover, the effectiveness of the methodology is verified by applying to the precision guided munitions. Conclusion: To achieve a analysis methods of statistical process control and verify process for precision guided munitions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.550-554
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• 2014

Regarding thin films in MEMS/NEMS structures, the exact evaluation of mechanical properties is very essential to enhance the reliability of their design and manufacturing. However, such methods as a tensile test and a resonance test, general methods to measure elastic moduli, cannot be applied to thin films since its thickness is so small. This work concerns guided wave based elastic modulus measurement method. To this end, guided wave excitation and detection system using a pulsed laser and a laser interferometry has been established. Also an elastic modulus extraction algorithm from the measured guided wave signal was developed. Finally, it was applied to actual thin film structures such as Ni-Si and Al-Si multilayers. From experimental results, we confirm that the proposed method has considerable feasibility to measure elastic properties of thin films.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.371-382
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• 2001

The recognition of such natural wave guides as plates, rods, hollow cylinders, multi-layer structures or simply an interface between two materials combined with an increased understanding of the physics and wave mechanics of guided wave propagation has led to a significant increase in the number of guided wave inspection applications being developed each year. Of primary attention Is the ability to inspect partially hidden structures, hard to access areas, and teated or insulated structures. An introduction to some physical consideration of guided waves followed by some sample problem descriptions in pipe, ice detection, fouling detection in the foods industry, aircraft, tar coated structures and acoustic microscopy is presented in this paper. A sample problem in Boundary Element Modeling is also presented to illustrate the move in guided wave analysis beyond detection and location analysis to quantification.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.161-164
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• 2015

본 논문에서는 고정된 카메라에서 초기 프레임을 참조하여 현재 프레임에 새롭게 유입된 물체의 실시간 분류 방법을 제안한다. 제안한 알고리즘의 실시간 분류 처리를 위하여 복잡도를 최소화 하였다. 먼저 전경과 배경을 구분하는 이진 분류 영상을 추출하기 위하여 DCT(Discrete Cosine Transform) 기법을 사용한다. DCT는 기존 공간영역에서 Texture를 분석하는 방식보다 더욱 정확하게 Texture를 분석할 수 있다. 이는 주파수 영역에서 Texture 특징 분석이 더욱 용이하고 각 요소 안에 intensity와 texture 정보를 종합적으로 고려할 수 있기 때문이다. 또한 DCT 계산 복잡도를 최소화하기 위하여 DCT 수행 전에 색 정보를 이용하여 미리 분류 영역을 분석함으로써 처리 효율을 극대화 하였다. 마지막으로 생성된 이진 분류 영상을 자연스럽게 matting하기 위하여 Guided 필터 사용을 제안한다. Guided 필터는 guidance 정보를 통해 입력 영상을 전반적으로 개선할 수 있지만 intensity가 평탄한 영역 등에서 그 한계를 보여주므로 본 논문에서는 Guided 필터의 단점을 개선하는 방법을 추가적으로 제안한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1031-1036
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• 2011

In this paper, we have proposed a methodology which can test and evaluate on system level in development phase of command guided missile system. Test and evaluation play a significant role in the development of weapon system, providing the means for determining to what extent the weapon system satisfies its requirements, whether it functions normally in the operational environment. In case of command guided missile having seeker, the missile communications link provides data to allow the missile to fly an efficient trajectory toward target. Therefore, it is very important to test and evaluate for data link between missile and radar on whole system aspect. we introduce the concept and devices for system level test and evaluation of command guided missile system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.757-762
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• 2013

A technique is presented that uses a new guided wave technique for sludge and blockages detection in long-range pipelines. Existing techniques have the limitations that the sludge position needs to be known a priori and the area to be inspected needs to be accessible. Two guided wave techniques have been developed which allow the sludge or blockages to be detected remotely without the need to access the specific location where the pipe is blocked, nor to open the pipe. The first technique measures the reflection of guided waves by sludge which can be used to accurately locate the blocked region; the second technique detects sludge by revealing the changes to the transmitted guided waves propagating in the blocked region or after it. The two techniques complement each other and their combination leads to a reliable sludge or blockage detection. Various types of realistic sludge have been considered in the study and the practical capabilities of the two techniques have been demonstrated.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.6
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• pp.589-598
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• 2002

The safe operation of petrochemical plant requires screening of the pipework to ensure that there are no unacceptable levels of corrosion. Unfortunately, each plant has many thousands of metres of pipe, much of which is insulated or inaccessible. Conventional methods such as visual inspection and ultrasonic thickness gauging require access to each point of the pipe which is time consuming and very expensive to achieve. Extensional or torsional ultrasonic guided waves in the pipe wall provide an attractive solution to this problem because they can be excited at one location on the pipe and will propagate many metres along the pipe, returning echoes indicating the presence of corrosion or other pipe features. Guided Ultrasonics Ltd have now commercialised the technique and this paper describes the basis of the method, together with examples of practical test results and typical application areas.