• 접착 및 계면
• /
• 제7권4호
• /
• pp.13-17
• /
• 2006

The elasto-plastic finite element method (FEM) was used to investigate the effect of off-center recessing location (8 mm length) on the stress distribution in the lap zone of adhesively bonded aluminium double lap joint. The results from simulation showed that the effect of off-cent recessing in bondline of double lap joint in the mid-bondline is not evidently to stress distribution in mid-bondline but the peak stresses both in mid-bondline and in the interface near the adherend side of the joint may increase markedly when an 8 mm length recessing was arranged symmetrical to the point of x =18 mm. When shifting an 8 mm length recess from near left end to the right end of the lap zone, all the highest peak stresses in the mid-bondline occurred under the condition of recess arranged symmetrical to the point of x = 6 mm.

• 한국추진공학회지
• /
• 제8권2호
• /
• pp.85-94
• /
• 2004

본 연구에서는 이중 와류 동축형 분사기의 설계 인자 특성 파악을 위해 실 추진제 연소 시험을 수행하였다. 본 시험에서는 물냉각이 적용된 재사용이 가능한 구리 재질의 노즐을 사용하였다. 연소 시험 시 고압 연소 조건에서 주요 설계 변수인 분무각과 함몰길이의 영향을 살펴보았다. 이 두 변수는 분사기의 연소 성능과 동특성, 수력학적인 특성에 큰 영향을 미치고 있다. 함몰영역에서의 내부혼합은 같은 유량을 보내기 위해 필요한 차압의 증가와 더불어 연소 효율을 증가시킨다. 내부 화염에 의한 분사기 차압은 LOx 축 방향 모멘텀 및 함몰길이의 변경을 통해 감소 또는 증가됨을 알 수 있었다. 또한 연소기에서 발생하는 동압 특성은 분사기의 형상에 따라 변화함을 알 수 있었다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
• /
• pp.288-293
• /
• 2006

본 논문은 축소형 액체로켓엔진 연소기의 성능 및 연소특성에 관한 것이다. 축소형 연소기는 분사기 헤드부, 내열재 실린더부, 그리고 강제 물냉각 노즐부로 구성되어 있다. 분사기 헤드부는 18개의 주분사기와 한 개의 점화기용 분사기로 구성되어 있다. 분사기의 형태는 동축 와류형 분사기이며, 리세스 길이에 따른 4종류의 분사기를 적용한 각각의 축소형 연소기의 연소시험 결과, 성능 비교 및 정압, 동압 특성에 대해 기술하였다. 또한 설계점 및 탈설계점에서의 연소특성에 대해서도 기술하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.699-703
• /
• 2017

액체로켓엔진에 사용되는 동축 와류형 분사기의 유동특성을 알아보기 위해 closed-type과 open-type 단일 분사기에 대한 수치해석을 수행하였다. ANSYS FLUENT라는 상용프로그램을 이용하여 해석적인 연구를 수행하였다. 분사기는 리세스 길이가 다른 3개의 모델을 선정하였다. 분사기 접선 방향의 입구로 유입되는 질량유량에 따라서 분사기 유동특성이 어떻게 변하는지 알아보기 위하여 수치해석을 수행하였으며, 실험을 통해 측정된 결과를 비교 및 분석하였다. 수치해석을 통해 얻은 결과는 실험을 통해 얻은 분사기 전단에 작용하는 압력과 유량계수와 차이가 크지 않음을 알 수 있었다.

• 대한기계학회논문집A
• /
• 제23권7호
• /
• pp.1231-1237
• /
• 1999

Applying the conjugate contact condition, contact lines of a cylindrical worm gear has been calculated. The characteristics of tooth contact were analyzed and the pitting resistance were also assessed. It has been verified that: i) the length of contact is shortest on the 1st tooth of the front region, ii) the contact region is more narrow in the recess side than in the access side, iii) the contact region is more narrow in worm than in worm wheel. Hence, the pitting resistance is weakest in the recess side of the 1st contacting worm tooth.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
• /
• pp.229-234
• /
• 2004

The objective of the present study is to conduct model combustion tests for double swirl coaxial injectors to identify their combustion stability characteristics. Gaseous oxygen and mixture of methane and propane have been used as simulant propellants. Two model chambers tuned to the If acoustic resonance mode of a full-scale thrust chamber were manufactured to be used as a combustion cylinder. The main idea of the experiment is that the mixing mechanism is considered as a dominant factor significantly affecting combustion instability in a full-scale thrust chamber. Self-excited dynamic pressure values in a model chamber show different combustion stability zones with respect to a recess number. Upon test results, couplings between combustion conditions and the IT acoustic resonance mode become strengthened with the increase of a recess length.

• Journal of Mechanical Science and Technology
• /
• 제17권3호
• /
• pp.321-328
• /
• 2003

The elongation of contact length on the line of action is considered with particular reference for roll forming of gears, and for dynamic behavior of the tooth in meshing. However there is no paper that discuss the elongation of contact length in the load meshing of gears. Based on our investigation, the contact length on the line of action elongates more than the kinematically calculated value. In rolling, as the tool approaches the workpiece, the center distance of the gears decreases by a small amount. But, the elongation of contact length is sensitive. Therefore, the contact point on the line of action is difficult to be determined, which complicates the tooth analysis. In this study, the exact relation between the elongation of contact length and the tooth space over the recess or before the approach are revealed by experiments and kinematic theory. This analytical result applies not only for rolling, but also for the single flank meshing which is done under constant center distance.

• 치과방사선
• /
• 제24권2호
• /
• pp.337-345
• /
• 1994

Arthrography of the temporomandibular joint is a useful method of demonstrating the soft tissue abnormalities related to disc dysfunction. In this study, 19 asymptomatic joints, 31 joints with anterior disc displacement with reduction, 31 joints with anterior disc displacement without reduction which were classified by arthrotomography under fluoroscopy were evaluated to determine the linear measurement of anterior recess of inferior joint space and the relationship between the condylar anterior translation and the severity of the internal derangements. Their fluoroscopic images were also evaluated to describe the characteristics of condylar paths in internal derangements of the temporomandibular joints. The results were as follows; 1. The mean lengths of the anterior recess in asymptomaic group. reduction group. and non-reduction group were 8.7±1.6㎜. 11.2±1.7㎜, 12.8±1.7㎜ respectively. The length of the anterior recess was increased according to the severity of the internal derangements(P<0.05). 2. Linear measurements of anterior movement of condyle on maximum mouth opening were 13.1 ±4.2㎜, 15.9±4.1㎜, 5.0±3.7㎜ in asymptomatic group. reduction group, and non-reduction group respectively. Compared with asymptomatic group, reduction group showed hypermobolity of the condyle and non-reduction group showed hypomobility. 3. Condyles moved beyond the crest of articular eminence in 80% of reduction group and did not reach it in 70% of non-reduction group. 4. The condyle moved mainly superiorly in reduction group(66%) and horizontally in asymptomatic group(47%). There were no cases to move superiorly in non-reduction group.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
• /
• pp.291-293
• /
• 2000

In 64M DRAM, sub-1/4m NMOSFETs with STI(Shallow Trench Isolation), anomalous hump phenomenon of subthreshold region, due to capped p-TEOS/SiN interlayer induced defect, is reported. The hump effect was significantly observed as channel length is reduced, which is completely different from previous reports. Channel Boron dopant redistribution due to the defect should be considered to improve hump characteristics besides consideration of STI comer shape and recess.

• Transactions on Electrical and Electronic Materials
• /
• 제3권3호
• /
• pp.18-20
• /
• 2002

In sub-l/4 ${\mu}{\textrm}{m}$ NMOSFET with STI (Shallow Trench Isolation), the anomalous hump phenomenon of subthreshold region, due to capped p-TEOS/SiN induced defect, is reported. The hump effect was significantly observed as channel length is reduced, which is completely different from previous reports. Channel boron dopant redistribution due to the defect should be considered to improve hump characteristics besides considerations of STI comer and recess. 130