• Wind and Structures
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• v.35 no.3
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• pp.147-155
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• 2022

This research proposes a wind-lens turbine design that can startup and operate at a low wind speed (< 5m/s). The performance of the wind-lens turbine was investigated using CFD and wind tunnel testing. The wind-lens turbine consists of a 3-bladed horizontal axis wind turbine with a diameter of 0.6m and a diffuser-shaped shroud that uses the suction side of the thin airfoil SD2030 as a cross-section profile. The performance of the 3-bladed wind-lens turbine was then compared to the two-bladed rotor configuration while keeping the blade geometry the same. The 3-bladed wind-lens turbine successfully startup at 1m/s and produced a torque of 66% higher than the bare turbine, while the two-bladed wind-lens turbine startup at less than 4m/s and produced a torque of 186 % higher than the two-bladed bare turbine at the design point. Findings testify that adding the wind-lens could improve the bare turbine's performance at low wind speed.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.563-568
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• 2015

풍력터변의 성능을 높이기 위한 방법으로 최근 해외에서는 쉬라우드를 장착하여 유입 유량을 증진시키는 형상에 대한 새로운 아이디어가 제안되고 시범적으로 적용되고 있다. 본 연구에서는 쉬라우드가 장착된 수평축 풍력터빈에 대해서 EDISON CFD를 이용하여 쉬라우드 내부로 유입되는 질량 유량의 변동을 몇 가지 형상에 대해 수치적으로 비교 분석하였다. 유동장은 비압축성 난류유동으로 가정하였으며, 수치 해석 결과로부터 쉬라우드 주변의 순환의 세기를 형상 변동에 따라 도출하였다. 쉬라우드 형상으로는 캠버를 갖는 goe 417 에어포일을 두 개의 받음각(5도, 10도)에 대해서 수치해석을 수행하였으며, 브림을 갖는 디퓨저 형상(Wind-lens)에 대해서도 유입 유량 변동과 순환 세기에 대해 수치해석을 수행하고 결과를 상호 비교하였다. 본 연구를 통해 쉬라우드가 발생시키는 순환에 의한 유입 유량 증가 현상을 파악할 수 있었으며, 이로써 풍력터빈의 출력을 증대시킬 수 있음을 확인하였다.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.4
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• pp.41-48
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• 2017

It is necessary to develop an LED traffic light lens having a snow removal function capable of clearly providing a traffic signal to the driver even when a traffic light is blurred due to heavy snow and wind in the winter season. This study is focused on the research and development of the traffic light lens in the process of developing the LED traffic light with the snow removal function. In the developed traffic light lens, instead of attaching the film heater, the coated nichrome wire was wound into a coil shape and inserted directly into the groove in the lens. The developed heater system facilitates the insertion of the heating wire with high elasticity into a curved lens and can provide a sufficient heat without deformation of the PC lens. The proposed traffic lights were tested in various external environments and the test results showed that complete snow removal is possible without tunnel effect.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.90-97
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• 2002

The interaction between airflow and liquid phase LfG (Liquefied Petroleum Gas) sprays was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside intake port of LPG engines with liquid injection system. The spray developments in flowing fields with the mean velocities of 5.4, 21.5 and 42.4m/s were identified by spray visualization techniques such as Mie scattering and shadowgraph. The microscopic visualization using a telescopic lens system was performed to investigate the shape and size of liquid droplets in the spray. PDA measurement was used to get 1-dimensional velocity and diameter of liquid droplets. The fast co-flows make the spray field be compact and be lead upward to the injection direction. SMD of the spray was smaller at the fast flowing field. Spray width got bigger and SMD of the spray was smaller with higher injection pressure.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.14 no.2
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• pp.207-223
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• 2001

The Wonyenaejang is equivalent to the (senile)cataract in western medicine. The word cataract is used to describe the natural lens that has turned cloudy. As the natural lens of the eye becomes cloudy, it does not allow light to pass through it. Cataracts usually start as a slight cloudiness that progressively grows more opaque. As the cataract becomes more mature(increasingly opaque and dense), the retina receives less and less light. The light that does reach the retina becomes increasingly blurred and distorted. This causes gradual impairment of vision. If left untreated, cataracts can cause needless blindness. Although there are many kinds of cataracts, a senile cataract is the most common one. We chose the oriental medicine textbooks and the oriental medicine journals that were dealing with the symptoms, etiology, and internal/external treatments. The results were as follows : 1. The main causes of this disease are weak liver and kidney, burning up of the wind and heat in the liver and gall, weak spleen and stomach. 2. As the internal treatment of the Cataract, Geegukjihwangtang is mostly prescribed. 3. As the external treatment of the Cataract, (l) In the field of medicine for external application is commonly prescribed (2) In the field of drug action, frequently used treatments are as follows. emission of the evil, alleviation of fever, removal of lump of blood, and the medicine for external applications. (3) In the field of four Qi, cold medicine is commonly prescribed. (4) In the field of five tastes, bitter/hot/sweet mdicine are commonly prescribed. (5) In the field of toxicity, non-togic medicine is commonly prescribed. (6) In the field of channel distribution, most of the medicine belong to liver channel.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.1
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• pp.55-62
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• 2002

A new off-surface visualization method of using the micro water droplet and laser beam sheet was presented. About a size of 5 to TEX>$10\mu\textrm{m}$ micro water droplet could be made from home-style ultrasonic humidifier, A 3 W Argon ion laser and cylindrical lens were used to generate a laser beam sheet, which interrogate specific cross section of the vortical flow field. Application of this new visualization method was conducted in KAFA small-sized low speed wind tunnel of having the test section of 0TEX>$0.9 m(W){\times}$0.9 m(H){\times}2.1 m(L)$$$. Visualization results show this method relatively easy and safe flow visualization method for wind tunnel testing. Moreover, this method is also make up for the disadvantage of smoke visualization, and can be applied to higher flow velocity range than that of smoke visualization.

• Journal of Mechanical Science and Technology
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• v.19 no.10
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• pp.1856-1863
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• 2005

In this study, a visual sensor system for weld seam tracking the I-butt weld joints in GMA welding was constructed. The sensor system consists of a CCD camera, a diode laser with a cylindrical lens and a band-pass-filter to overcome the degrading of image due to spatters and arc light. In order to obtain the enhanced image, quantitative relationship between laser intensity and iris opening was investigated. Throughout the repeated experiments, the shutter speed was set at 1/1000 second for minimizing the effect of spatters on the image, and therefore the image without the spatter traces could be obtained. Region of interest was defined from the entire image and gray level of the searched laser stripe was compared to that of weld line. The differences between these gray levels lead to spot the position of weld joint using central difference method. The results showed that, as long as weld line is within $\pm15^{o}$ from the longitudinal straight line, the system constructed in this study could track the weld line successfully. Since the processing time is no longer than 0.05 sec, it is expected that the developed method could be adopted to high speed welding such as laser welding.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.545-551
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• 2016

Surface temperature of supersonic wind tunnel model was measured using an infrared thermography technique. To measure the temperature quantitatively, various calibration techniques such as blackbody calibration which converts detected camera signal to temperature, distortion correction due to the camera lens and an imbalance of camera pose, and emissivity calibration which considers viewing angles to the model surface, were employed. Throughout the study, for the quantitative as well as qualitative surface temperature measurement, it was verified that the distortion correction must be considered even for the use of two-dimensional model in aerodynamics testing.

• Journal of the Korean Society of Earth Science Education
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• v.3 no.3
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• pp.184-190
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• 2010

This study is to verify the effects of classes at a finishing stage using cartoons depicting certain science textbook units on scientific attitudes and academic achievements of students, compared to those of classes using experiment and observation oriented textbooks. Participants of this study were 56 fifth graders at B Elementary School in Busan, and cartoon textbooks were developed based on 'Unit 1. Mirror & Lens' and 'Unit 3. Temperature & Wind' from a science textbook for the 1st semester, the year 5 to conduct cartoon led lessons just before ending a class till the 10th lesson, for the period of 4 weeks. The result of this study can be summarized as follows: Firstly, scientific attitudes improved better from the cartoon based lesson of a final stage than from the experiment and observation method, and especially more effective in lower groups among all other academic achievement levels as well as in male students. Secondly, academic achievements scored higher when cartoons were used in lessons than when the experiment and observation type was used, with higher groups of academic achievement levels working better, despite no significant gap existing between two genders. Thirdly, the memory transfer and sustenance of lessons were more effective in finishing class stage with cartoon studies than with experiment and observation one, and among all levels and both sexes, higher academic groups and male pupils exceeded. Fourthly, when questioned about their opinions on a cartoon led lesson for a final stage, 65% of those participants responded positively, while higher groups preferred more than lower groups. responded positively, while higher groups preferred more than lower groups.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.381-384
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• 2011

Wave drag reduction due to the repetitive laser induced energy deposition over a flat-nosed cylinder is experimentally conducted in this study. Irradiated laser pulses are focused by a convex lens installed in side of the in-draft wind tunnel of Mach 1.94. The maximum frequency of the energy deposition is limited up to 80. Time-averaged drag force is measured using a low friction piston which was backed by a load cell in a cavity as a controlled pressure. Stagnation pressure history, which is measured at the nose of the model, is synchronized with corresponding sequential schlieren images. With cylinder model, amount of drag reduction is linearly increased with input laser power. The power gain only depends upon the pulse energy. A drag reduction about 21% which corresponds to power gain of energy deposition of approximately 10 was obtained.