• 한국해양공학회지
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• 제27권5호
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• pp.51-62
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• 2013

The water wave interactions on any three-dimensional structure of arbitrary geometry can be calculated numerically through the use of source distribution or Green's function techniques. However, such a method can be computationally expensive. In the present study, the water wave interactions in floating circular cylinder arrays were investigated numerically using the eigenfunction expansion method with the three- dimensional potential theory to reduce the computational expense. The wave excitation force, added mass coefficient, radiation damping coefficient, and wave run-up are presented with the water wave interactions in an array of 5 or 9 cylinders. The effects of the number of cylinders and the spacing between them are examined because the water wave interactions in floating circular cylinder arrays are significantly dependent upon these.

• 한국환경복원기술학회지
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• 제14권1호
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• pp.11-22
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• 2011

This study was established to build and suggest the Ecological Performance Standards for replaced wetlands as the mitigation strategies for the construction projects. The request performance and assessment factors and standards were derived by bibliographic review and verified by the field survey for the reference wetlands. And the weights for each factor were derived by AHP(Analytical Hierarchy Process) method. The results are as follows : 1) Assessment factors were induced by in-depth research of many wetland assessment models and benchmarks evaluated ecological functions. This study proposed final 12 assessment factors through ecological specialist and experts interviews added with literature analysis. 2) 10 natural wetlands were selected as Reference Wetlands as the measure to propose assessment factors and assessment criteria. Those reference wetlands are well-conserved inland natural wetlands classified to the one having worthy to conserve (grade "high") according to RAM(Rapid Assessment Method). Reference wetlands chosen by the study are Parksilji, Jeongyangji, Mulkubi, Bawineupkubi, Jilnalneup, Jinchonneup, Doomoso, Haepyung wetland, Whangjeong wetland, and Whapo wetland. The research developed assessment criteria for the performance assessment factors based on several explorations of the reference wetlands. 3) "Requiring performance" of replaced wetlands is defined as "to carry out similar or same ecological functions provided by natural wetlands", in overall. The detailed requiring performances are as follows; ${\bullet}$ to play a role of wildlife habitats ${\bullet}$ to have biological diversity ${\bullet}$ to connect with other ecosystems ${\bullet}$ to provide water environment to perform good ecological functions 4) The assessment factors for required performance are categorized by wildlife habitat function, biological diversity, connectivity of adjacent ecosystem, and water environment. Wildlife habitat category is consisted of wildlife habitat creation, size of replacement wetland, and site suitability. Biological diversity category contains the number of plant species, the number of wildlife species, and number of protected species as the sub-factors. Connectivity of adjacent ecosystem is comprised of wildlife corridor, green network and distance from other ecosystem. Finally, water environment make up with water quality, depth of water body, and shape of waterfront. 5) Finally, every assessment factors were verified and weighted by the AHP methods and the final standards were proposed. The weights of factors of requiring performance suggested as habitat (0.280), connectivity (0.261), diversity (0.260), hydraulic environment (0.199). And those of detailed sub-factors are site suitability (0.118), protected species (0.096), distance to neighbor ecosystem (0.093), habitat creating (0.091), green corridor (0.090) etc.

• 대한화장품학회지
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• 제41권4호
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• pp.325-331
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• 2015

피부는 낮 동안 태양빛과 인공 빛에 끊임없이 노출되어 있으며, 그중 5%는 UV 영역, 50%는 가시광선, 나머지 45%는 적외선 영역으로 구성되어 있다. 이중 자외선의 피부에 대한 영향은 많은 연구가 되어 왔으나, 나머지 영역에 대한 연구는 미진한 실정이다. 이에, 가시광선에서 적외선 사이의 파장이 피부 섬유아세포에 어떤 영향을 미치는지 연구하고자 하였다. 광처리에 의한 효과는 광파장, 처리 시간, 광세기, 광조합 등 다양한 파라미터들의 조합에 의해 그 효능이 결정되므로, 본 연구에서는 섬유아세포의 성장 및 콜라겐 합성과 관련된 기능을 촉진시킬 수 있는 광처리 조건을 찾아내고자 하였다. 가시광선과 적외선 영역 사이의 6개의 파장을 처리한 결과, 레드(630 nm)와 그린(520 nm) 파장에 의해 섬유아세포의 증식이 증가함을 확인하였다. 광처리 시간은 콜라겐 합성량 증가를 위해서는 10 min의 광처리가 30 min의 광처리 보다 적합한 조건이었다. 광세기는 $0.05{\sim}0.75mW/cm^2$에서 6개의 광세기로 분할하여 실험한 결과, 레드 $0.3mW/cm^2$와 그린파장 0.15, $0.3mW/cm^2$ 세기가 type I collagen의 mRNA의 양을 증가시킬 수 있었다. 마지막으로 두 개 파장을 순차적으로 조합 처리하였을 때의 효과를 확인한 결과, 레드와 그린파장의 조합 조건은 섬유아세포의 수적증가를 목적으로 할 때 효율적인 방법이며, 콜라겐 합성에는 레드 단독처리가 보다 효과적인 방법이었다. 따라서 본 연구에서 제시하는 광처리 조건을 이용시 피부 세포의 성장이나 콜라겐 합성에 긍정적 영향을 유도할 수 있으며, 재생 및 피부 미용 등에 활용할 수 있는 가능성이 클 것으로 기대된다.

• 한국광학회지
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• 제16권1호
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• pp.63-70
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• 2005

컬러 LCD(liquid crystal display) 모니터의 광학적 상에 대한 성능을 평가하기 위하여 LCD 모니터를 포함한 모든 광학계의 파장별 공간주파수 반응에 가중치를 부여한 진폭전달함수(modulation transfer function ; MTF)를 이용한 다색광전달함수(polychromatic modulation transfer function ; PMTF)를 제안한다. 서로 다른 진폭들을 갖는 적색(R), 녹색(G), 청색(B)의 3개의 막대형 LCD 단위물체를 이용한 컬러 LCD의 PMTF의 시뮬레이션 결과와 실험적 결과가 잘 일치하며, 이 결과 컬러 LCD의 결상성능은 단색으로 측정하는 MTF 및 가시광의 전파장대를 사용하는 백색광 MTF와는 다른 R, G, B의 3색에 대한 PMTF로 측정하늘 것이 보다 적절하다.

• 한국지능시스템학회논문지
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• 제11권3호
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• pp.241-245
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• 2001

기존의 퍼지 교통 제어기들이 직관적 지식과 경험 또는 표준 규칙 베이스를 이용하여 규칙 베이스를 구성하지만, 그런 방식으로 구성된 규칙 베이스는 전문가와 운전자의 제어지식을 구체적이고 정확하게 표현할 수 없다는 문제가 있다. 따라서 본 연구에서는 제어지식을 더욱 정확하게 표현한 퍼지 교통 제어기를 설계하여 퍼지 교통 제어의 성능을 향상시킬 수 있는 방법을 제안한다. 제안된 방법은 제어지식을 정확히 표현할 수 있도록 입출력 데이터 클러스터링을 기초하여 퍼지 소속함수의 위치와 형태를 수정한다. 직관적 지식과 경험에 의해 주어진 대략적인 제어지식은 입출력 데이터 클러스터링을 위한 평가함수로 이용된다. 제안된 방법으로 설계된 퍼지 교통 제어기는 전문가와 운전자의 제어지식을 더욱 정확하게 표현할 수 있었고, 통과 차량수의 녹색시간 낭비율면에서 기존의 제어기 보다 우수한 성능을 보였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.352.2-352.2
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• 2016

In recent times, much effort has been concentrated on trivalent rare-earth ions activated ceramics or oxide phosphors to develop display industries due to their promising applications in optoelectronic devices and field-emission displays. To prepare efficient phosphors, citrate sol-gel method is one of the best synthetic methods. Green and blue emissive CaLa2ZnO5:RE3+ nanocrystalline materials are synthesized by a citrate sol-gel method. After the samples annealing at $1100^{\circ}C$, morphological and structural properties are investigated by scanning electron microscope images and X-ray diffraction patterns, respectively. At low electron beam voltage of <5 kV, the visible photoluminescence properties are obtained. Various concentrations of the RE3+ ions exhibited their characteristic emission peaks at different excitation wavelengths, respectively. Similarly, at high electron beam anodic voltage, the cathodoluminescence properties are studied as a function of acceleration voltage and filament current. The chromaticity coordinates are calculated for the optimized CaLa2ZnO5 nanocrystalline luminescent materials.

• 한국소음진동공학회논문집
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• 제19권5호
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• pp.454-461
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• 2009

Internal aeroacoustics of an axial fan used for circulating cold air in refrigerators are computed by using the hybrid method where CFD, acoustic analogy and BEM techniques are utilized. The unsteady flow field around the axial fan is predicted by solving the incompressible RANS equations with the conventional CFD techniques. Then, main noise sources are extracted from this unsteady flow field predictions using Acoustic Analogy. Lastly, BPF noise generated from an axial fan are predicted using these modeled sources combined with the tailed Green function techniques, which are numerically solved by the BEM technique. This hybrid model is validated by comparing the prediction with the experiment. Then, parameter studies are carried out, which suggest a capability of the current method as a design tool for the low-noise of the current axial fan system in a refrigerator.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.731-734
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• 2002

This paper presents the assessment of input impedance of a sectoral cylindrical cavity-backed slot antenna excited by a probe. This antenna is proposed to be an element of array that can be assembled to be the antenna for UHF TV broadcasting system. The integral equations are derived based on boundary conditions of the proposed structure and are expressed in terms of dyadic Green's functions and unknown currents. The unknown current densities are solved by the Method of Moments and the input impedance is derived subsequently. Numerical results show the variation of input impedance, for the specified dimensions of the antenna, as a function of frequency. This result is validated by measurement and found that the result is sufficiently accurate. The result from this study is useful for the design of a sectoral cylindrical cavity-backed slot antenna excited by a probe.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1752-1761
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• 2000

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• 대한조선학회지
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• 제18권1호
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• pp.19-27
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• 1981

The surge motion of a freely-floating sphere in a regular wave is studied within the framework of a linear potential theory. The fluid is assumed to be perfect and only the steady-state harmonic motion in a water of infinite depth is considered. A velocity potential describing the fluid motion is decomposed into three parts; the incident wave potential, the diffraction potential and the radiation potential. In this paper the diffraction potential and the radiation potential are analysed by using multipole expansion method. Upon calculating pressures over the immersed surface of the sphere, the hydrodynamic forces are evaluated in terms of Froude-Krylov, diffraction, added mass and damping forces as functions of the frequency of the incident wave. Finally the frequency dependence of two pertinent parameters, the amplitude ratio and the phase lag between the motion of the sphere and that of the incident wave is derived from the equation of motion. As for numerical results the general tendency of the present calculation shows good agreement with Kim's work who also treated this problem utilizing the Green's function method.