• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.126-132
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• 2010

A Lamb wave guided by a plate structure has dispersive characteristics because phase and group velocity change with the variation of frequency and thickness. The Lamb wave has two modes, symmetric and anti-symmetric mode, which propagates symmetrically and non-symmetrically with respect to centerline. In this paper, the derivation of Lamb wave equation with anisotropic material property is investigated. The phase velocity and group velocity dispersion curves are shown using the stiffness matrix of composite materials with the variation of angle.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1171-1177
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• 2011

A high power laser beam focused on a small area accelerates a thin material that flies and hits other target material in which a shock wave may be induced. This laser induced shock experimental method is more repeatable and cheaper but worse than other experimental method using gas gun or other apparatus. An optical system including a phase zone plate reduces the interference and also makes the focused-beam-intensity distribution uniform. We wrote a computer code that calculates light ray traces. Using the code we designed and fabricated an optical system including a phase zone plate and improved the laser-beam uniformity. We introduce preliminary experimental results of laser induced shock of the samples such as aluminum and other materials.

• Korean Journal of Optics and Photonics
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• v.2 no.4
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• pp.219-226
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• 1991

The phase and the amplitude of the photoacoustic signal were measured as a function of chopping frequency for several kinds of widely used thin metallic plates (stainless steel 304, brass, aluminum and copper) attached to plexiglass backing. The experimental data have been analyzed systematically by parameter estimation technique based on the two-layer model developed from Rosencwaig-Gersho (R-G) theory. Using this analysis, the values of thermal diffusivity and thermal effusivity of the materials have been determined.

• Korean Architects
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• s.596
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• pp.20-27
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• 2018

올해로 '대한민국 신진건축사대상(이하 신진건축사대상)'은 6회째를 맞이했다. 정부가 한국식 '유로판(Europan)'을 추진한다는 목적 하에 젊고 창의적 건축사를 육성하기 위한 취지로 시작된 본 시상제도는, 만 45세 이하 건축사 중 건축사사무소를 개설 신고해 본인 설계로 준공된 작품이 1개 이상 보유한 건축사만 참여할 수 있다. 정부의 취지 만큼 국제적 명성의 건축사를 성장시키는 토양과 배려가 필요한 시점이다. 사실 단순 상수상은 의미가 없다. 건축사의 설계 작품은 건설업이나 건자재 사업을 촉진 시킬 수 있는 지식 산업으로 인식이 필요한데, 정부의 적극적인 지원 정책이 요구되는 시점이다. 신진건축사 대상은 2013년 국내 건축문화와 우수 건축사에 대한 국제브랜드화를 위해 명망 높은 신진 건축사를 키우기 위해 시작됐지만, 인센티브 부족 등 당초 기대치에 못 미친다는 지적도 있다. 정부가 그동안 공을 들여온 신진건축사 육성을 위해선 사무소 직원채용 지원, 홍보, 각종 정부사업 참여로 파이를 키울 수 있는 기회를 부여하는 등 실질적인 인센티브를 부여해야 한다는 의견도 있다. <월간 건축사>가 역대 '대한민국 신진건축사대상' 대상수상자에게 시상제도 발전을 위한 제언과 대한민국 건축사로 살아가며 느끼는 다양한 건축이야기들을 들어봤다.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.55-61
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• 2021

In this paper, we proposed and implemented defect detection methods of polarized film with half-wave phase retardation plates. We investigated the principles of phase retardation compensation and optical principle of half-wave phase retardation plates. We analyzed of samples of polarized film with half-wave phase retardation plates. The optical defect detection methods are proposed and the performance is validated with experiments.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.165-172
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• 2009

A set of equations for description of transformation of harmonic waves is proposed here. Velocity potential function and separation of variables are introduced for the derivation. The continuity equation is in a vertical plane is integrated through the water so that a horizontal one-dimensional wave equation is produced. The new equation composed of the complex velocity potential function, further be modified into. A set up of equations composed of the wave amplitude and wave phase gradient. The horizontally one-dimensional equations on the wave amplitude and wave phase gradient are the first and second-order ordinary differential equations. They are solved in a one-way marching manner starting from a side where boundary values are supplied, i.e. the wave amplitude, the wave amplitude gradient, and the wave phase gradient. Simple spatially-centered finite difference schemes are adopted for the present set of equations. The equations set is applied to three test cases, Booij's inclined plane slope profile, Massel's smooth bed profile, and Bragg's wavy bed profile. The present equations set is satisfactorily verified against existing theories including Massel's modified mild-slope equation, Berkhoff's mild-slope equation, and the full linear equation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.9
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• pp.973-978
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• 2014

This study focused on the design of the reflecting layer of a light trapping system fora thin film solar cell using topology optimization based on the phase field method. Therefore, incident light was caused to propagate in the desired direction by reflecting it from this layer, which is the design domain. The same method was applied to the conceptual design of an infrared stealth structure in near infrared range. The results using the phase field method were compared with those using the density method. The design objective was to maximize the Poynting vector value representing the energy flux, which was measured in a measuring domain to control the reflected wave direction. A finite element analysis and optimization process were performed using the commercial package COMSOL combined with the MATLAB programming.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.211-216
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• 2008

In this study, we have developed a program which can calculate phase and group velocities, attenuation and wave structures of each mode in multi-layered plates. The wave structures of each mode are obtained, varying material properties and number of layers. The key in the success of guided wave NDE is how to optimize the mode selection scheme by minimizing energy loss when a structure is in contact with liquid. In this study, the normalized out-of-plane displacements at the surface of a free plate are used to predict the variation of modal attenuation and verily the correlation between attenuation and wave structure. It turns out that the guided wave attenuation can be efficiently obtain from the out-of-plane displacement variation of a free wave guide alleviating such mathematical difficulties in extracting complex roots for the eigenvalue problem of a liquid loaded wave guide. Through this study, the concert to optimize guided wave mode selection is accomplished to enhance sensitivity and efficiency in nondestructive evaluation for multi-layered structures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1356-1363
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• 2009

The aim of this research is to construct eigenfrequency optimization codes for plates with Arbitrary Rank Microstructures. From among noise factors, resonance sound is main reason for floor's solid noise. But, Resonance-elusion design codes are not fixed so far. Besides, The prediction of composite material's capability and an resonance elusion by controlling natural frequency of plate depend on designer's experiences. In this paper, First, using computer program with arbitrary rank microstructure, variation on composite material properties is studied, and then natural frequency control is performed by plate topology optimization method. The results of this study are as followed. 1) Programs that calculate material properties along it's microstructure composition and control natural frequency on composite material plate are coded by Homogenization and Topology Optimization method. and it is examined by example problem. 2) Equivalent material properties, calculated by program, are examined for natural frequency. In this paper, Suggested programs are coded using $Matlab^{TM}$, Feapmax and Feap Library with Homogenization and Topology Optimization method. and Adequacy of them is reviewed by performing the maximization or minimization of natural frequency for plates with isotropic or anisotropic materials. Since the programs has been designed for widely use. If the mechanism between composite material and other structural member is identified, extension application may be possible in field of structure maintenance, reinforcement etc. through application of composite material.

• Journal of the Korean Geographical Society
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• v.39 no.3
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• pp.409-424
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• 2004

This study examines Korean-related description from 1931 to 2002 in 18 university-level ‘World Regional Geography’ textbooks, being published as English. During this period, the amounts of Korean-related contents in world regional geography textbooks have gradually increased. The main Korean-related topics were generally ‘Colonization by Japan’, ‘Korean War’, ‘Rapid economic development in South Korea’, and ‘North Korea’. The distorted information and erroneous description about Korea were mostly found in textbooks. The national and cultural identity of Korea was severely distorted and made a fallacy by ‘accidental-centered’ thought. It is suggested that foreign geographers who refer ‘Korea’ in World Regional Geography textbooks need to critically re-examine the ways in which Korean-related contents are in proper place.