• 한국태양에너지학회 논문집
• /
• 제21권1호
• /
• pp.1-10
• /
• 2001

Polycrystalline silicon(poly-Si) films are deposited on low temperature glass substrate by Hot-CVD(HWCVD). The structural properties of the poly-Si films are strongly dependent on the temperature$(T_w)$. The films deposited at high $T_w$ of $2000^{\circ}C$ have superior crystalline proper average lateral grain sizes are larger than $1{\mu}m$ and there are no vertical grain boundaries. The sur of the high $T_w$ samples are naturally textured like pyramid shape. These large grain size and text surface are believed to give high current density when applied to solar cells. However, the poly films are structurally porous and contains high defect density, by which high concentration of C and O resulted within the films by air-penetration after removed from chamber.

• 한국전자파학회논문지
• /
• 제16권11호
• /
• pp.1067-1074
• /
• 2005

원형 마이크로스트립 안테나를 기본 구조로 하고 단점인 표면파의 영향을 개선하기 위해 접지면에 광 밴드 갭 구조를 취하여 대역폭을 늘리고 안테나의 후방 방사를 줄였다. 또한 광 밴드 갭의 형태를 각기 달리하여 그에 따른 안테나 특성의 변화를 관찰하였다. 끝으로 유전체 사이에 비유전율이 유전체보다 낮은 공기층을 삽입하여 전체적인 비유전율을 낮게 만들어 작은 크기로 높은 응답 주파수 특성을 보였다.

• Advances in aircraft and spacecraft science
• /
• 제11권1호
• /
• pp.83-103
• /
• 2024

Adhesive bonding is currently widely used in many industrial fields, particularly in the aeronautics sector. Despite its advantages over mechanical joints such as riveting and welding, adhesive bonding is mostly used for secondary structures due to its low peel strength; especially if it is simultaneously exposed to temperature and humidity; and often presence of bonding defects. In fact, during joint preparation, several types of defects can be introduced into the adhesive layer such as air bubbles, cavities, or cracks, which induce stress concentrations potentially leading to premature failure. Indeed, the presence of defects in the adhesive joint has a significant effect on adhesive stresses, which emphasizes the need for a good surface treatment. The research in this field is aimed at minimizing the stresses in the adhesive joint at its free edges by geometric modifications of the ovelapping part and/or by changing the nature of the substrates. In this study, the finite element method is used to describe the mechanical behavior of bonded joints. Thus, a three-dimensional model is made to analyze the effect of defects in the adhesive joint at areas of high stress concentrations. The analysis consists of estimating the different stresses in an adhesive joint between two 2024-T3 aluminum plates. Two types of single lap joints(SLJ) were analyzed: a standard SLJ and another modified by removing 0.2 mm of material from the thickness of one plate along the overlap length, taking into account several factors such as the applied load, shape, size and position of the defect. The obtained results clearly show that the presence of a bonding defect significantly affects stresses in the adhesive joint, which become important if the joint is subjected to a higher applied load. On the other hand, the geometric modification made to the plate considerably reduces the various stresses in the adhesive joint even in the presence of a bonding defect.

• 대한두개안면성형외과학회지
• /
• 제19권4호
• /
• pp.260-263
• /
• 2018

Background: The alar and nasal tip are important subunits of the nose. Determining the optimal procedure for reconstructing a cutaneous defect in a nasal subunit depends on several factors including size, location, and involvement of deep underlying structures. We treated cutaneous defects after tumor ablation in the alar and nasal tip with a local flap, using an S-shaped design and a modified V-Y advancement flap with a croissant shape. Methods: We analyzed 36 patients with skin tumors who underwent flap coverage after tumor ablation. Rotation flaps were used in 26 cases and croissant-shaped V-Y advancement flaps were used in 10 cases. The primary cause of the defects was skin cancer, except for one benign tumor. Results: The mean patient age was 71 years. The size of the defects ranged from $0.49cm^2$ to $3.5cm^2$. No recurrence of skin cancer was noted and all flaps lasted until the end of follow-up. Partial desquamation of the epidermis was noted in one case. The postoperative appearance for most patients was excellent, objectively and subjectively. Conclusion: For cutaneous defects of up to about $4.0cm^2$ of the alar and nasal tip, local flaps using our methods offered a good cosmetic and therapeutic result. The main advantage of our flaps is the minimal dissection required compared to bilobed and other local flap methods. We believe our flaps are a suitable option for alar and nasal tip reconstruction.

• 한국진공학회지
• /
• 제22권5호
• /
• pp.250-256
• /
• 2013

양전자 소멸 분광법으로 발광 박막 시료에 3.0 MeV 에너지를 가진 양성자 빔을 $0.0{\sim}20.0{\times}10^{13}$ protons/$cm^2$의 조사에 의해 생성된 결함을 측정하여 박막구조 특성에 대하여 실험하였다. 동시 계수 도플러 넓어짐 양전자 소멸법 스펙트럼의 수리적 해석 방법인 S-변수를 사용하고, 양전자 수명 측정 방법에 의한 양전자 수명 ${\tau}_1$과 ${\tau}_2$, 이에 따른 세기 $I_1$과 $I_2$를 사용하여, 박막구조에 대한 결함 특성 변화를 측정하였다. 측정된 S-변수는 박막에 조사된 양성자의 빔 조사량에 따라 양성자가 빈자리에 포획되어 감소하는 값을 보였다. 양전자 수명 ${\tau}_1$은 증가하고, ${\tau}_2$은 일정한 값을 나타내었으나, 반면에 세기 $I_1$과 $I_2$는 큰 변화가 없었다. 그 이유는 양성자 조사 빔의 변화에 따라서 단일 빈자리의 크기는 증가하고, 다 결정체 알갱이 빈자리 때문에 양성자에 의한 다수의 빈자리 결함의 양은 큰 차이가 없기 때문이다. 그리고 Bragg 피크로 인하여 박막 시료의 특정 깊이에 결함을 형성하여 박막 전체의 결함으로 잘 나타나지 않기 때문으로 판단된다.