• Tribology and Lubricants
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• 제21권2호
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• pp.83-92
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• 2005

A piston assembly is very important because it directly receives the energy generated during combustion process. Surely, the friction and lubrication of piston-ring pack do an important role in the performance and fuel economy of an engine. In fact, the friction loss in piston-ring pack is the biggest portion to the whole engine friction. Therefore, the improvement of lubrication quality and friction loss in piston-ring pack will be directly related with the improvement in the performance and fuel economy of an engine. Meanwhile, the oil consumption and blow-by gas through piston-cylinder-ring crevices have to be controlled as less as possible. In these two aspects, the study on the optimized design of piston-ring pack has to be carried out. In this study, for the efficient design of piston-ring pack, it is focused to develop a basic computer program that predicts the inter-ring pressure, the motion of ring and the blow-by gas through a crevice volume model between adjacent rings, and the oil film thickness and the friction computed by lubrication theories.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.452-455
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• 2008

In the present study, blow forming characteristics of commercially roiled AZ31 alloy sheets were investigated. Two different kinds of AZ31 sheets were originally fabricated by using direct casting and strip casting methods respectively. Both sheets have similar grain sizes of about $7{\mu}m$ with a relatively equiaxed structure after rolling. A series of tensile tests were carried out to get flow behavior in terms of temperature and strain rate. Also, grain size effect was investigated by annealing as-received sheet at elevated temperatures. Elongation increased with temperature increment as well expected. However, the differences in tensile test condition did not give much difference in elongation even at the temperature range where a large elongation would be expected with such as fine grain of $7{\mu}m$. Blow forming experiments showed that forming condition did not result in higher difference in dome height. However, the interesting feature from this study was that formability of this AZ31 alloy got different with stress condition. Firstly, biaxial stress condition might result in lower temperature and strain rate dependencies compared to uniaxial tension results for both DC and SC sheets. Secondly, DC showed slower grain growth in uniaxial tension than in biaxial stress state while SC has much higher grain growth rage in uniaxial tension than in bulging.

• 한국산학기술학회논문지
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• 제16권8호
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• pp.5082-5088
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• 2015

본 논문에서는 1000cc급 엔진의 내구성능 시험을 진행하였다. 총 300시간의 내구 시험이 WOT조건으로 진행되었다. 엔진토크, 출력, 제동연료소비율, 블로바이 가스량, 오일압력 등을 시간에 따라 계측하였다. 실험결과, 고 rpm에서의 성능은 시간에 따라 감소하였으나, 저 rpm에서의 성능은 안정적이었다. Blow-by gas 유량은 평균 흡입 공기량의 0.4%로 우수한 성능을 나타내었다. 엔진의 토크와 연료소모율은 100시간까지는 길들이기 특성을 보였으며, 그 이후에 노화되는 경향을 보였다. 300시간 내구시험 후 엔진을 분해하여 부품의 파손 및 균열 여부를 확인하였다.

• 한국음향학회지
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• 제34권4호
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• pp.328-334
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• 2015

본 논문은 다양한 타격 강도와 위치에 따른 징의 음향 차이를 소프닝과 맥놀이 분석을 통해 살펴본다. 타격 강도는 아주 강하게, 강하게, 약하게로 구분하였고 타격 위치는 가운데, 위, 오른쪽으로 구분하였으며 분석에는 스펙트로그램을 사용하였다. 소프닝은 징의 가운데를 강하게 타격할수록 명확하게 관측되었고 주파수 이동 폭은 타격 강도와 주파수에 비례하였다. 이러한 현상은 배음에서 두드러졌으며 다른 부분음에서는 불규칙적으로 발생하였다. 맥놀이는 초기 맥놀이와 후기 맥놀이로 분류할 수 있었으며 가운데를 타격할 때보다 측면을 타격할 때 더 넓은 주파수 대역에서 더 많은 맥놀이가 발생한다는 것을 알 수 있었다. 또한 가운데를 타격한 경우 초기 맥놀이에 영향을 주는 배음 주변의 성분들이 있음을 밝혔다.

• International Journal of Aeronautical and Space Sciences
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• 제7권2호
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• pp.50-55
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• 2006

Currently, a gas fueled diffusion flame is used for the relay torch system. It could be burned cleanly but should be stable at severe weather condition such as rain of up to 55 mm/h, winds of up to 70 km/h and also produce a highly bright yellow visible flame. This paper presents torch diffusion flame characteristics on the various wind speeds and rainfall conditions. From the results, flame lengths are controlled by the momentum flux ratio of fuel and ambient air flow and flame stability is much influenced by the mixing characteristics with air flow. Flame is fluctuated above than 200 mm/h rainfall and blow out is occurred about 300 mm/h rainfall condition.

• Archives of Plastic Surgery
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• 제40권4호
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• pp.445-449
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• 2013

Retrobulbar hemorrhage, especially when associated with visual loss, is a rare but significant complication after facial bone reconstruction. In this article, two cases of retrobulbar hematoma after surgical repair of blow-out fracture are reported. In one patient, permanent loss of vision was involved, but with the other patient, we were able to prevent this by performing immediate decompression after definite diagnosis. We present our clinical experience with regard to the treatment process and method for prevention of retrobulbar hematoma using a scalp vein set tube and a negative pressure drainage system.

• 한국화재소방학회논문지
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• 제28권3호
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• pp.34-42
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• 2014

본 연구에서는 $CH_4$ 및 $C_3H_8$ 연료의 컵버너 비예혼합화염에서 Swing, Rotation, Lifted 및 Blow-out과 같은 화염 불안정성을 발생시키는 불활성기체($N_2$, Ar, $CO_2$ 및 He)의 농도를 측정하였으며, 소화기준(즉, 화염날림 또는 화염불안정성 개시)에 따른 소화농도의 정량적 차이를 검토하였다. 소화농도의 차이는 부상화염의 발생 그리고 낮은 소화성능의 불활성기체일수록 증가됨을 확인하였다. 소화기준에 따른 소화농도의 최대 차이는 $C_3H_8$-air 비예혼합화염의 최대 연료유속의 조건(1.3 cm/s)에서 약 35%이다. 또한 화염 불안정성의 개시를 기준으로 측정된 소화농도는 정확한 그리고 경제적 설계 농도의 관점에서 유용한 정보를 제공할 것으로 기대된다.

• 대한두개안면성형외과학회지
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• 제10권2호
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• pp.71-75
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• 2009

Purpose: Recently, orbital wall fracture is common injuries in the face. Facial CT is essential for the accurate diagnosis and appropriate treatment to reconstruct of the orbital wall. The objective of this study was to report the method for accurate measurement of area and shape of the bony defect in the blow-out fractures using facial CT in prior to surgery. Methods: The authors experienced 46 cases of orbital wall fractures and examined for diplopia, sensory disturbance in the area of distribution of the infraorbital nerve, and enophthalmos in the preoperation and followed 1 months after surgery, from August 2007 to May 2008. Bony defect was predicted by measuring continuous defect size from 3 mm interval facial CT. Copying from the defect model (template), we reconstructed orbital wall with resorbable sheet (Inion $CPS^{(R)}$ Inion Oy, Tampere, Finland). Results: One months after surgery using this method, 26 (100%) of the 26 patients improved in the diplopia and sensory disturbance in the area of distribution of the infraorbital nerve. Also 8 (72.7%) of the 11 patients had enophthalmos took favorable turn. Conclusion: This accurate and time-saving method is practicable for determining the location, shape and size of the bony defect. Using this method, we can reconstruct orbital wall fracture fastly and precisely.

• 대한두개안면성형외과학회지
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• 제11권1호
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• pp.1-6
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• 2010

Purpose: Many surgical approaches for reconstruction of blow out fracture have been introduced, which include subciliary incision, transconjunctival incision and transcaruncular incision. Recently endoscopic approach has been attempted. This study was intended to show the effectiveness of the approach through transconjunctival incision combined with transnasal reduction in reconstructing blow out fracture to its original position. Methods: Medical recoreds of 43 patients from March 2008 to March 2009 who underwent surgery for orbital fracture were reviewed, retrospectively. All fractures were operated through transconjuctival incision approach combined with transnasal reduction. The average follow-up period was 10.1 months. To evaluate the surgical outcomes of orbital fracture, we performed CT of the facial bone before and after the surgery. In addition, preoperative and postoperative data of enophthalmos, diplopia and the limitation of extraocular motion was assessed with physical examination. Results: Post-operative CT scan of 43 patients assured that the bone fragments of the orbital fractures were restored to their original positions. Although a few patients developed postoperative transient diplopia or impairment of ocular movement, most of the patients recovered during the follow-up period without complication. Conclusion: From this study, we were able to demonstrate the effectiveness of the transnsasal reduction technique combined with the approach through transconjunctival incision. This technique can be considered as very useful means of repairing orbital fracture. It is not only easy to perform but also it can minimize the damage to the orbital bone. Furthermore, it can restore the fracture to its original position as much as possible.

• 대한두개안면성형외과학회지
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• 제10권1호
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• pp.29-32
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• 2009

Purpose: Alloplastic implants, such as $Silastic^{(R)}$, $Supramid^{(R)}$, Porous polyethylene, $Teflon^{(R)}$ have been used to prevent reherniation of orbital tissue and are known to be inert for many years, though complications are infrequently reported many years after their insertion. Complications associated with implants are infrequent, but infection, orbital hemorrhage, implant extrusion, motility restriction, migration of implant causing dacryocystitis, cystic formation have been described. The latter was known as a rare late complication of blow-out fracture repair. Methods: We report the case of a discovery of a intraorbital hemorrhagic cyst which developed after silicon implant insertion. This patient developed diplopia, unilateral proptosis, exophthalmos, vertical dystopia, ectropion 10 years after repair of blow-out fracture. In this case, orbital CT scan revealed intraorbital cyst surrounding the orbital implant. At surgery, a fibrous capsule surrounded the silicon implant and was filled with mucin pools. Results: Proptosis, diplopia, exophthalmos, ectropion, vertical dystopia were resolved after surgical removal of the cyst and implant. Conclusion: This case illustrate that it is important for us to be aware of the complication of cyst formation around the silicon implants.