• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.373-373
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• 2016

파푸아뉴기니 열대 우림에 서식하는 극락조의 가슴깃은 독특한 나노 구조를 가지고 있다. 이 독특한 구조에 의해 구조색이 발현된다. 또한 이 구조색은 입사하는 빛의 각도에 따라 색이 변화 하며 아름다운 색을 낸다. 극락조의 가슴깃의 구조는 keratin과 melanin으로 구성 되어 있는데 keratin과 melanin이 한 층씩 교대로 위치하여 multi layer 구조를 가진다. 가슴깃의 단면의 형태는 부메랑 모양의 구조로 되어 있는데 물질은 주로 keratin 으로 이루어져 있고 keratin 내부에 melanin rodlet이 층층이 박혀서 multi layer를 형성한다. 부메랑 모양의 단면에서 keratin 피질의 각도는 약 $30^{\circ}$ 정도로 이루어져 있고 내부의 melanin 기둥이 이루는 층은 약 $11.3^{\circ}$ 정도로 이루어져 있다. 본 연구에서는 극락조 가슴깃의 구조를 도식화 하여 입사하는 빛의 각도에 따라 나타나는 구조색을 FDTD simulation을 통해 계산하였고 실제 구조에 의해 측정된 reflectance spectra와 비교하여 특성이 유사하게 나타남을 확인 하였다. 실제 극락조 가슴깃의 반사 특성은 부메랑 모양 구조의 가운데 부분에서는 파장이 610 nm 정도인 주황빛이 주로 반사가 되고, 부메랑 모양 구조의 양옆 부분에서는 파장이 420 nm 정도인 파란빛이 주로 반사되어 나타난다. 그리고 각도에 따른 구조색의 변화는 보통의 multi layer의 특징과 다르게 나타난다. 입사하는 빛의 각도가 커질수록 reflectance peak가 나타나는 파장이 점점 짧아지는 특징은 일반적인 multi layer와 일치하지만 일반적인 multi layer가 입사 각도가 커질수록 reflectance가 커지는데 반해 극락조 가슴깃의 반사특성은 입사 각도가 커질수록 reflectance는 오히려 작아진다. 우리가 도식화한 구조를 FDTD simulation한 결과는 이러한 특징이 실제 구조의 측정 결과와 일치하게 잘 나타났다. 또한 keratin과 melanin층의 각도 및 두께변화에 따른 reflectance를 FDTD simulation을 통해 계산 해보았고 구조변화에 따른 특징들을 확인해 보았다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.8
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• pp.519-525
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• 2016

In a pump, from the performance point of view, it is very important to minimize the shock loss at the inlet of the rotor blades. In this study, the effects of shape and install angle of the inlet guide on the performance of an axial-flow pump are numerically simulated using commercial CFD code, Ansys CFX. Finally, to obtain the optimized shape of the vanes and the install angle of the vanes in the inlet guide under given operating conditions, optimization analysis is conducted using Analysis design exploration based on response surface optimization.

• Korean Journal of Environment and Ecology
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• v.22 no.4
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• pp.435-441
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• 2008

This study conducted a survey on the moulting sequence subsequent to age of Haliaeetus pelagicus raised in captivity at the Ornithology Laboratory attached to Kyungsung University for about six years from November, 2000 until July, 2006. The survey indicated that the moult of rectrices usually began in July and continued until April of the next year and most of the rectrices were replaced by one-time moult. Usually, about two thirds of the tail feathers were replaced while the rest were replaced no later than April of the next year, and the moult also continued during the wintertime. The total number of rectrices was 14, and the moult progressed alternately on a systematic basis. The progress of the moult for female & male was made on four stages and three stages respectively and the characteristic shown on every stage of the moult was that the left & right tail feathers progressed symmetrically and not until one stage of progress almost completed did the next stage began. The color of the juvenile steller's sea-eagle was dotted with black spots on its original white color and there existed regular black belt on its feather's fringes; however, it was difficult to identify its age by tail feathers only because there was almost no difference in color between feathers ranging from the first to the third generation(1st-3rd summer feathers). In addition, this research took the different amounts of black-speckled pattern appearing by individual into consideration. There existed slight black speckles in white color feathers of the fourth generation(the 4th summer feathers) while showing a big difference compared to the 3rd generation feathers. The 5th generation feathers[the 5th summer feathers]were found to be equipped with perfect tail feathers having virgin white of a steller's sea-eagle after completing its 4th molt. When observing a steller's sea-eagle in the open air, it is necessary for an observer to have a deliberate examination in judging its age belonging to the 1st-3rd generation feathers, and it is considered that the changes of other parts of feathers should be also observed besides tail feathers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1391-1398
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• 2011

Design and performance analysis of a steam turbine for variations of degree of reaction were performed by computer simulation. Design parameters such as blade angles, exit areas, and heights of the nozzle and moving blade were represented as functions of the degree of reaction. The main performance factors such as turbine power, diagram efficiency, and axial thrust were also expressed in terms of the degree of reaction. For further information about the design and performance, the blade angles and main performance factors were investigated as functions of the flow coefficient. The turbine power and diagram efficiency reached a maximum value for a given degree of reaction and flow coefficient, and the symmetric shape of the moving blade showed distortion as the degree of reaction was increased.

• Journal of KSNVE
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• v.10 no.2
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• pp.229-239
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• 2000

To reduce the drag rise on the advancing helicopter rotor blade tips, the tip of the blade is modified to have sweep, anhedral and pretwist. The equations of motion of rotor blade with these tip angles were derived using Hamilton principle, programmed using FORTRAN and named as ARMDAS(Advanced Rotorcraft Multidisplinary Design and Analysis System). Rotating frequency analysis of rotor blades with swept tipe was performed that is necessary in conceptual and preliminary design phases of the helicopter design. Vibration analysis of non-rotating blades was also accomplished and compared with MSC/NASTRAN resutls for the basis of comparison with the vibration test data. The rotating frequency analysis of blades with an actual rotor blade data was also performed to verify coded program and to check the possibility of a resonance of an actual rotor blade at the specific rotating speed.

• Journal of KSNVE
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• v.8 no.3
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• pp.477-484
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• 1998

An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the prewist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and prewist angles, lead to the coupled motions of the shaft and the bladed disk.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1017-1024
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• 2012

The aerodynamic design and analysis on advanced propeller with blade sweep was performed for recent turboprop aircraft. HS1 airfoil series are selected as a advanced propeller blade airfoil. Adkins method is used for aerodynamic design and performance analysis with respect to the design point. Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. Propeller geometry is generated by varying chord length and pitch angle at design point of target aircraft. Advanced propeller is designed by apply the modified chord length, the tip sweep which is based on the geometry of conventional propeller. The aerodynamic characteristics of the designed Advanced propeller were verified by CFD(Computational Fluid Dynamic) and evaluated to be properly designed.

• Korean Journal of Environment and Ecology
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• v.13 no.2
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• pp.160-166
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• 1999

대구시에 식재되어 있는 조경수목 20종류 199그루를 대상으로 큰 가지 전정 후 부위의 상태를 그루터기의 길이, 절단면의 상태, 가지 깃이 찢어진 여부, 유합제 처리여부를 중심으로 조사한 결과 그루터기의 길이는 근린공원, 시설녹지, 주택단지에서 각각 평균 8.8cm, 3,7cm, 6.8cm로 나타났다. 절단면의 상태에 있어서 돌출되거나 함몰되는 등 매끈하지 못한 경우의 비율은 근린공원, 시설녹지, 주택단지에서 각각 26.7%, 40.0%, 16.7%로 나타났다. 가지 깃(branch collar)이 찢어진 경우의 비율은 근린공원, 시설녹지, 주택단지에서 각각 18.7%, 5.7%, 11.1%로 나타났다. 유합제를 처리한 비율은 근린공원, 시설녹지, 주택단지에서 각각 0.0%, 20.0%, 1.0%로 나타나 대구시 조경수목의 전정 관리상태는 전반적으로 불량한 상태이며, 전정 후 절단부위가 병충해에 의한 감염과 습도에 의한 부패에 매우 취약할 것으로 조사되었다. 또한 절단면의 상태는 그루터기를 기준보다 길게 남긴 경우, 가지 깃 부분이 찢어지거나 부러진 경우, 절단면이 불규칙한 경우와 이상 3가지 유형 중 2가지 이상의 경우가 복합적으로 나타나는 경우 등 4가지로 크게 구분되었으며, 각 유형에 따른 적당한 사후 관리가 필요하다.

• Korean Journal of Plant Taxonomy
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• v.44 no.4
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• pp.257-260
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• 2014

While preparing a floristic study of Korean Pteridophytes, we discovered the following two unrecorded species from Jeju Island: Cyclosorus penangianus (Hook.) Copel. and Pteris fauriei Hieron. C. penangianus can be distinguished from other Korean congeners of the genus Cyclosorus by having exindusiate sori, toward with sinus of ultimate segments of veinlets more than 4. P. fauriei can be distinguished from other Korean congeners of the genus Pteris by having ultimate segments with entire margins, veins reaching to leaf margin and membraneous petiolar scales.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.57.1-57.1
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• 2005