A Study of the LED Module Heat Dissipation Structure Suitable

Keum-yeon Choi,Ik-soo Eo 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.8

In this paper, reduces the absolute temperature of the LED module, results of the experiments have been derived a method to improve the suitability heat dissipation structure and properties are as follows. First, FR-4 PCB size in consideration of the PCB LED module air-hole 3mm radius of the LED module area 10%, 20%, 30% ratio after a process of simulation to generate the air-hole on the PCB and the surrounding, 30%, 50×30mm intervals, when generating a fifty-two, applying the air-hole 3mm 10% of the radius of the area LED module obtained the results of temperature reduction than max. about 3.5℃ and min. about 3.1℃. Second, LED array interval and to be suitable experimental structure through the PCB air-hole generation plate type heat-sink for LED module to support the air-hole radius 40mm size to create a two and six and four, as a result of the simulation in progress, when air-hole number pairs of the increase, max. and min. temperature was reduced to obtain a formal conclusion by about 1~1.5℃. the air-hole 3mm 10% of the radius of the area applied LED module than max. about 4.5℃, min. about 4.2℃ results was confirmed reduction. As a result, to the suitable of the heat dissipation even if the LED module PCB material no matter how good, if the heat sink is not well designed structural cannot obtain a large effect.

특발성황반원공 2, 3기의 유리체절제술, 내경계막제거술과 액체공기교환술의 성적

이성복,남기엽,김경남,조영준 대한안과학회 2009 대한안과학회지 Vol.50 No.7

Purpose: To examine the results of macular hole surgery using pars plana vitrectomy (PPV), triamcinolone-assisted peeling of the internal limiting membrane (ILM), and intravitreous air in idiopathic stage 2 and 3 macular holes. Methods: Thirteen eyes of 13 consecutive patients with idiopathic macular hole underwent a PPV with triamcinolone-assisted ILM peeling and intravitreous air tamponade. An air-fluid exchange was performed and the patient was asked to maintain a face-down position at home for 4 days. The follow-up period was 6 months or more in all cases. If a significant cataract was present before surgery, a combined phacoemulsification with posterior chamber lens implantation was performed at the time of the macular hole surgery. The closure of the macular hole was determined by biomicroscopy and Optical Coherence Tomography (OCT). Results: The idiopathic macular hole was closed after the primary operation in all 13 patients. The postoperative visual acuities (0.1 to 0.9) significantly improved from the preoperative visual acuities (0.02 to 0.4) in all eyes. There was no recurrence of the macular hole and there were no adverse effects of the intraoperative use of triamcinolone and ILM peeling during the follow-up period. Conclusions: This study suggests that triamcinolone-assisted ILM peeling with intravitreous air may be an effective technique for stage 2 and 3 macular holes. This procedure could reduce the face-down position time and improve early visual rehabilitation by using air instead of long-acting gas tamponade. 목적: 특발성 황반원공 2기, 3기 환자에서 유리체절제술, 트리암시놀론을 이용한 내경계막제거술과 액체공기교환술의 수술경과를 알아보 고자 하였다. 대상과 방법: 특발성 황반원공 2, 3기로 진단받은 환자 중 유리체절제술, 트리암시놀론을 이용한 내경계막제거술과 액체공기교환술을 시행받은 13명 13안을 대상으로 하였다. 11안에서 수정체유화술 및 인공수정체삽입술을 동시에 시행하였다. 모든 수술은 구후마취하에 시행되었고, 입원하지 않고 집에서 4일간 안면하체위를 유지하였다. 검안경과 빛간섭단층촬영을 이용하여 황반원공 폐쇄여부를 확인 하였으며, 6개월 이상 경과관찰하였다. 결과: 13안에서 황반원공은 1회의 수술에 의해 폐쇄되었으며, 수술 전 시력 0.02~0.4에서 수술 후 시력은 0.1~0.9로 모든 안에서 수술 전에 비해 시력향상을 보였다. 최소 6개월간의 경과관찰 중 황반원공의 재발 및 유리체강내 트리암시놀론 주입과 내경계막 제거에 의한 합병증은 발생하지 않았다. 결론: 특발성 황반원공 2기와 3기 환자에서 본 수술은 효과적이었으며, 또한 엎드린 자세를 최소화하였으며, 안내 충전기간을 줄여 수술 후 시력의 조기 회복이 가능하였다.

Optimum design of the injection duct system of a stenter machine

막슈다쥬래바,류경진,송동주 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5

Stenter machines are used for drying fabrics in the textile industry and have a heater, injection duct system, and fans inside a chamber. The injection duct system has ducts and air-injecting holes. Plane-type injection duct systems were investigated to obtain uniform airflow at the air-injecting holes. The flowfield of the injection duct systems was computed using ANSYS CFX with different heights of the duct end and different shapes for the air-injecting holes. There was a high mass flow rate at the air-injecting holes and high airflow circulation inside both plane-type and mountain-type ducts at the ends. The height of the duct end was varied between 40 mm and 160 mm. The injection duct systems were analyzed with four different shapes of air-injecting holes. The circular and elliptical holes had lower standard deviations of the mass flow rate than other shapes. Relatively uniform mass flow rates were obtained in the plane-type and mountain-type duct systems when the height of the duct end was 40 mm and the shape of the air-injecting holes was circular or elliptical. The developed injection duct systems were improved by obtaining a uniform mass flow rate at the air-injecting holes. A stenter prototype was fabricated with the developed injection duct system to confirm the numerical results. The developed injection duct system had better performance than the original system.

무등산 너덜지대의 온혈 현상

박철웅 한국지리학회 2017 한국지리학회지 Vol.6 No.3

In winter season, at the inclined talus slope of the north side of Mt. Mudeung, there are holes (Warm Wind Holes; WWH) with no artificial heating, which are warmer than the surrounding area. These holes are usually referred as the wind hole (Poong-hyul in Korean). More precisely speaking, it is referred so when warm air comes out of the entrance of wind holes during the winter season. The effect of winter warming in wind holes in relation to the outside climate has not been well explained. This study, conducted from January 2014 to february 2016, observed and analyzed the annual variations of temperature/humidity of wind hole inside and outside. Based on the result of this analysis, I found several characteristics as follows. First, the annual average temperature/humidity of the WH10 (In) showed 12.01°C/96.12% during two years, while WH19 (Out) showed 7.59°C/84.5%. Second, the difference in maximum temperature during the period was 23.25°C in summer season, but it was 43°C in winter season. This reveals that WWH event has an outstanding phenomenon than cold wind hole event in Mt. Mudeung. This phenomenon is assumed to be caused by the effect of thermal mechanism between inside and outside of wind holes. In other words, it is changed from latent heat to changed sensible heat. In this way, Wind holes zone of Mt. Mudeung is a continuum which is formed by a set of column joint, talus slope, is a infrequent topographical landscape that creates a natural warm hole phenomenon. 무등산 누에봉의 암괴사면에서는 인위적인 열 공급이 없이 겨울에 따뜻한 공기와 수증기를 내뿜는 온혈 현상이 나타난다. 이런 현상이 나타나는 풍혈은 약 40여 개 정도가 밀집되어 풍혈대를 이루고 있다. 겨울철에 풍혈의 입구에서 나오는 따뜻한 바람이 온혈 현상이다. 외부의 기후와 관련하여 겨울철 풍혈의 온혈 효과는 잘 설명되지 않는 부분이 있다. 이 연구는 2014~2016년의 2년간 수집된 데이터를 통해 풍혈의 외부와 내부의 온도와 습도의 연 변화를 모아 분석하였다. 분석 결과, 첫째 풍혈 내부의 2년간 연평균 기온과 습도는 12.1°C/96.1%였고, 풍혈 외부는 7.59°C/84.5%였다. 둘째, 그 기간 동안 최대의 기온편차는 여름철에 23.25°C이고, 겨울철에는 43°C의 차이를 보였다. 이는 무등산에서 겨울철의 온혈이 여름철의 냉혈보다 두드러지게 나타난다는 것을 보여주는 것이다. 이 현상은 풍혈의 내부와 외부 간의 열적 기작의 효과에 의해서 일어난다는 것으로 추정된다. 즉, 잠열이 현열로 변한 것이다. 이와 같이 무등산 풍혈대는 주상절리대, 암괴사면의 너덜이 한 세트로 형성된 연속체로서 자연적인 온혈 현상을 만들어 내는 지형 경관이다.

조기낙엽이 참다래 ``헤이워드`` 과실 바람들이와 품질에 미치는 영향

곽용범 ( Yong Bum Kwack ),김홍림 ( Hong Lim Kim ),최영하 ( Young Hah Choi ),이재한 ( Jae Han Lee ),김진국 ( Jin Gook Kim ),이용복 ( Yong Bok Lee ) 한국환경농학회 2012 한국환경농학회지 Vol.31 No.3

BACKGROUND: The fruit quality and flowering characteristics of Kiwifruit (A. deliciosa cv. Hayward) in the following year is known to be affected by the extent and timing of defoliation of the current year. In korea, the production of kiwi, which is a perennial, straggling deciduous warm-temperate fruit, is often restricted by wind damage due to typhoons resulting to defoliation at the middle season of its growing period. In this paper, we report the effect of the different timing of defoliation and severities at the current season to the kiwifruit quality. METHODS AND RESULTS: Twenty seven-year-old ``Hayward`` trees grown under polyethylene film rain-shelter were defoliated in different days from August to September at seven day-intervals. In each day, 0, 25, 50, 75 and 100% of leaves were removed from the trees. Fruits from each treatment were classified into four floating types (L: lying in bottom, S: standing on bottom, F: floating and SF: floating at the surface of water) by submerging them into tap water. Defoliation of kiwifruit trees in August and September caused air holes in locules of inner pericarp. Increased number of air hole in locules of a fruit was observed in floating types F and SF, and most of the air holes were located in stem end. The defoliation of trees in August significantly reduced the ratio of L-floating type fruits, which have the least number of locule air holes. The extent of defoliation also affected the distribution of the four types, the more leaves removed, the less L-floating type fruits harvested. The weight of fruits from trees defoliated in August was lower than that of fruits from September. Soluble solids content decreased as the number of locule air holes increased. Negative correlations were observed between the extent of defoliation and the weight and soluble solids content of fruits. CONCLUSION: Early defoliation effect on kiwifruit locule air hole occurrence and fruit quality were more severe in August than in September. And also if the defoliation severity is over 25%, severe fruit quality reduction expected to happen due to increase of fruit locule air hole in the inner pericarp.

특발성 황반원공 수술 중 안 내 공기충전술 후 3일간 독서자세만 취한 환자의 수술 결과

권영기(Young Ki Kwon),엄선정(Sun Jung Eum),신재필(Jae Pil Shin),김인택(In Taek Kim),박동호(Dong Ho Park) 대한안과학회 2015 대한안과학회지 Vol.56 No.11

목적: 특발성 황반원공 환자의 유리체절제술과 안내가스충전술 후 일주일간 안면하자세를 취한 군과 액체공기교환술 후 독서자세를 취한 군 간의 수술 후 원공폐쇄율과 평균시력을 비교하고자 한다. 대상과 방법: 특발성 황반원공 2, 3기로 진단 받은 환자 25안을 대상으로 하였다. 유리체절제술 중 액체공기교환술 후 14% C 3 F 8 가스 안내충전술 후 일주일간의 안면하체위를 시행한 군과 액체공기교환술 후 독서자세를 3일간 시행한 군의 수술 6개월 후 원공의 폐쇄율 과 최대교정시력을 각각 비교하였다. 결과: 평균 원공의 크기는 1군과 2군에서 456.2 ± 164.1 μm, 411.2 ± 105.7 μm로 두 군 간의 통계적 차이는 없었고( p =0.647) 원공의 폐쇄율은 수술 6개월째 1군에서 93%, 2군이 100%였다( p =0.616). 최대교정시력(logMAR)은 수술 전, 수술 6개월 후 1군의 경우 0.92 ± 0.35에서 0.82 ± 0.29였고 2군은 0.97 ± 0.33에서 0.71 ± 0.39로 두 군 모두 향상되었으나 두 군 간에 통계적 차이는 없었다 ( p =0.809, p =0.267). 결론: 특발성 황반원공 환자의 유리체절제술 중 액체공기교환술 후 3일간 독서자세만 취한 군의 6개월째 원공의 폐쇄율과 최대교정시 력의 개선 정도가 안내가스충전술 후 1주일간 안면하자세를 취한 군과 비교해서 큰 차이가 없었다. 이 수술 방법을 통해 황반원공의 수술 후 안면하자세로 인한 불편함을 경감시키는 데 도움이 될 수 있다고 생각한다. Purpose: In this study we compared the postoperative hole closure rate and average vision between a group who assumed a face-down position for a week using gas and a group who assumed a reading position after fluid air exchage (FAX), both after re-ceiving internal limiting membrane (ILM) peeling during vitrectomy in patients with idiopathic macular hole. Methods: This study included 25 eyes of patients diagnosed with idiopathic macular hole that underwent vitrectomy. Group I as-sumed a face-down position for a week after intraocular gas tamponade after FAX during vitrectomy and Group II assumed a reading position for 3 days after only FAX. The hole closure rate and the best-corrected visual acuity (BCVA) were compared be-tween the 2 groups 6 months postoperatively. Results: The preoperative mean macular hole size was 456.2 ± 164.1 µm in Group I and 411.2 ± 105.7 µm in Group II and the differences between the 2 groups were not statistically significant (p = 0.647). At 6 months after surgery, the macular hole clo-sure rate was 93% in Group I and 100% in Group II (p = 0.571) and the BCVA (log MAR) was 0.82 ± 0.29 preoperatively and 0.92 ± 0.35 postoperatively in Group I and 0.71 ± 0.39 and 0.97 ± 0.33 in Group II, respectively. The differences between the 2 groups (p = 0.09, p = 0.058) were not statistically significant (p = 0.809, p = 0.267). Conclusions: There was no significant differences in the macular hole closure rate and BCVA improvement after 6 months in pa-tients with idiopathic macular hole who had FAX during vitrectomy and maintained only a reading position for 3 days compared with those with gas tamponade and who maintained a face-down position for a week. This surgical method is considered helpful for easing discomfort caused by a face-down position after the macular hole surgery.

수치해석을 통한 비상피난지원 시스템의 급기구 크기에 따른 유동분석

김지태(Ji Tae Kim),박원희(Park Won Hee),이덕희(Duck Hee Lee),노경철(Kyoung-Chul Ro) 한국산학기술학회 2020 한국산학기술학회논문지 Vol.21 No.4

비상피난 지원시스템은 화재 발생시 차연막이 형성되고 차연막 내부로 외기를 급기 가압을 해주어 연기의 유입을 막아주어 안전한 대피로를 제공한다. 본 연구에서는 수치해석을 통해 급기구 지름이 10, 15, 20, 30 mm로 변화 할 때 비상피난 지원시스템 차연막 내부에 급기구 크기가 유동에 미치는 영향을 분석하였다. 그 결과 급기구 지름이 감소할수록 비상피난지원 시스템 입구부터 출구 길이 방향으로 급기구를 통한 유량이 비교적 고르게 형성 되는 양상을 보였다. 또한 20 mm 이상으로 급기구를 타공 할 경우 출구부 근처에는 급기 유량이 거의 발생하지 않는 문제점이 발생 하므로 급기구 지름을 20 mm 보다 작게 타공 해야 할 것으로 판단된다. 차연막 내부 공간 압력은 20 mm 이하로 타공시 길이방향으로 비교적 매우 균일한 분포를 보였다. 또한 수치해석 결과를 이용하여 급기구의 부차 손실계수을 산출 하였으며 약 K=1.5 으로 계산되었다. 따라서 향후 비상피난 지원 시스템 설계시 본 연구에서 도출한 급기구 지름에 따른 유동특성과 급기구의 부차손실을 적용하여 적절한 설계가 수행될 수 있을 것으로 판단된다. The emergency evacuation support system provides a safe means of evacuation by preventing the inflow of smoke through the formation of a smoke shield curtain in fire situations and pressurizing fresh air to the inside of the smoke shield curtain. In this study, numerical analysis was performed to examine the effects of the hole size on the flow inside the smoke curtain. As the air supply size decreased, the flow rate through the air supply was formed relatively uniformly from the inlet to the outlet length of the emergency support system. In addition, the size of the air supply hole was more than 20 mm, the flow rate was very low near the outlet, so the air supply hole size should be smaller than 20 mm. In addition, the minor loss of the air supply hole was calculated to be K = 1.5 from the numerical results. Therefore, the proper design of an emergency evacuation support system is possible using the flow characteristics according to the size and minor loss of the air supply hole.

열 배출구 형상 모델링 자동화 시스템 개발

박현풍(Hyunpung Park) (사)한국CDE학회 2009 한국CDE학회 논문집 Vol.14 No.5

Nowadays a lot of high-tech electronic products such as TVs, monitors and camcorders are being developed. The more functions the electronic devices have, the more heat problems occur. Therefore, most of electronic products have air-ventilation holes to eliminate heat that is generated inside the products. The shapes of ventilation holes are usually complicated since aesthetic appearance of the products is important these days. In order to create those complicated shapes, designers should do time-consuming jobs because most of commercial CAD systems do not provide the functions that create patterns of lofted parts along freeform surfaces. In this research, an automated air-ventilation hole modeling system was proposed. The system generates patterns of lofted objects on freeform surfaces. Standard process to create air-ventilation holes manually was established, and vent-hole types and pattern types were classified into several categories. Designers can create many kinds of vent-holes by combining vent-hole types and pattern types. Users can also utilize user-defined pattern which can give users more flexibility. Developed system was applied to several design examples and the results are presented.

The effect of rotating receiver hole shape on a gas turbine pre-swirl system

Jungsoo Lee,이현규,Donghwa Kim,Jinsoo Cho 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.5

The life assessment and the efficiency of turbine cooling blades and vanes are seriously affected by the cooling air delivery system of a gas turbine. The pre-swirl system in a gas turbine plays an important role between the stationary and rotating parts to supply enough cooling air at the appropriate temperature at the expense of pressure drop. In the stationary part, the pre-swirl nozzle creates the flow angle in advance of the rotating orifice, called the receiver hole, to minimize energy loss. However, because of the sudden change of direction and area of the flow path, an energy loss occurs at the inlet of the receiver holes. The circumferential velocity at the receiver hole inlet decreases even though the circumferential velocity at the pre-swirl outlet is equal to the tangential velocity of the turbine rotor system. To reduce the energy loss at the pre-swirl system, various shape parameters can be applied to the receiver hole, and the area ratio between the pre-swirl nozzle throat area and the receiver hole crosssectional area can also be varied considering the structure problem, mass flow rate, and pressure drop. In this study, the shape of the receiver holes and its effects were analyzed using a 3D CFD method that was validated by previous studies including experimental data. The edge shape, inclined angle, area ratio, and number of receiver holes were analyzed with the discharge coefficient, adiabatic effectiveness, and pressure drop. The pre-swirl system performance increased as the area ratio increased, and under fixed area ratio, a large number of smalldiameter receiver holes showed better performance. The receiver hole edge fillet was the most influential shape parameter in pre-swirl performance.

결로수 배출구 유무에 따른 삼중유리 시스템창의 결로방지성능 및 기밀성능 실험 평가

박시현(Park, Si-hyun),김민희(Kim, Min-hee),임재한(Lim, Jae-Han),송승영(Song, Seung-Yeong) 한국건축친환경설비학회 2016 한국건축친환경설비학회 논문집 Vol.10 No.1

The condensation risk for windows during winter is high, and such condensation can lead to mold problems, thereby causing discomfort for building occupants. Triple glazing window systems used for energy saving, consist drainage holes placed on glazing beads or gaskets providing a path for condensed water from inside to outside. These holes are considered to be effective in view of draining condensed water. However, these holes may lead to the decrease of air-tightness as well as the increase of condensation risk resulted from the drop of surface temperature due to the intake of cold outside air. Therefore, in this study, the triple glazing window system without the drainage holes was examined as a case with no drainage holes (CNH), and evaluate the condensation resistance and air-tightness compared to a case with drainage holes (CWH). Condensation resistance and air-tightness were tested in accordance with KS F 2295 and KS F 2292, respectively. Temperature difference ratios and infiltration rates between CNH and CWH were compared.