• 대한치과교정학회지
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• 제47권4호
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• pp.238-247
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• 2017

Objective: The aim of this study was to compare recycled and unused orthodontic miniscrews to determine the feasibility of reuse. The comparisons included both miniscrews with machined surfaces (MS), and those with etched surfaces (ES). Methods: Retrieved MS and ES were further divided into three subgroups according to the assigned recycling procedure: group A, air-water spray; group B, mechanical cleaning; and group C, mechanical and chemical cleaning. Unused screws were used as controls. Scanning electron microscopy, energy-dispersive X-ray spectrometry, insertion time and maximum insertion torque measurements in artificial bone, and biological responses in the form of periotest values (PTV), bone-implant contact ratio (BIC), and bone volume ratio (BV) were assessed. Results: Morphological changes after recycling mainly occurred at the screw tip, and the cortical bone penetration success rate of recycled screws was lower than that of unused screws. Retrieved ES needed more thorough cleaning than retrieved MS to produce a surface composition similar to that of unused screws. There were no significant differences in PTV or BIC between recycled and unused screws, while the BV of the former was significantly lower than that of the latter (p < 0.05). Conclusions: These results indicate that reuse of recycled orthodontic miniscrews may not be feasible from the biomechanical aspect.

• 한국군사과학기술학회지
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• 제19권5호
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• pp.618-628
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• 2016

The development of new concepts of liners is required in order to effectively neutralize the enemy's attack power concealed in the armored vehicles. A multiple-layer liner is one of possibilities and has a mechanism for explosion after penetrating the target which is known as "Behind Armor Effect." The multiple-layer explosive liner should have sufficient kinetic energy to penetrate the protective structure and explosive material react after target penetration. With this in mind, double-layer liner materials were obtained by cold spray coating methods and these material properties were experimentally characterized and used in this simulation for double-layer liners. In this study, numerical simulations in the three different layer types, i.e., single, A/B, A/B/A in terms of the layer location were verified in terms of finite element mesh sizes and numerical results for the jet tip velocity, kinetic energy, and the corresponding jet deformation characteristics were analysed in detail depending on the structure of layer types.

• 한국산림과학회지
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• 제76권4호
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• pp.357-360
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• 1987

1) 다(茶)나무 엽수병(葉銹病)의 침입경로(侵入經路)는 다엽(茶葉)의 이면(裏面)에 있는 모용세포(毛茸細胞)임이 확인(確認)되었다. 2) 다(茶)나무중(中) 엽수병(葉銹病)이 가장 많이 발병(發病)되는 부위(部位)는 신초부위(新梢部位)로부터 1~5엽(葉) 범위(範圍)에 있는 유엽(幼葉) 부위(部位)였다. 3) 다(茶)나무잎에 포자(胞子)가 발아(發芽)되는 가장 적당(適當)한 온도(溫度)는 $25^{\circ}C{\sim}27^{\circ}C$일 때였으며, 수분(水分)이 12시간(時間) 젖어 있을 때였다. 4) 따라서 다(茶)나무 엽수병(葉銹病)의 예방(豫防) 방제(防除) 약제(藥劑)의 살포시기(撒布時期)는 이 시기(時期)에 살포(撒布)하는 것이 가장 효과적(效果的)일 것이며 또한 모초(毛茸)의 수량(數量)이 적은 다(茶)내무의 품종(品種)을 선발증식(選拔增植)하는 것이 가장 좋은 방법(方法)이라고 생각한다. 5) 분생포자(分生胞子)의 형성(形成)에 대(對)한 볼드액(液)의 조지효과(阻止效果)는 무살포구(無撒布區)에 비(比)하여 살포구(撒布區)에서 48.3%의 효과(效果)가 있었다. 6) 볼드액살포(液撒布)에 의(依)한 효과(效果)의 지속성(持續性)은 접종당시(接種當時)에는 28.5%였던 것이 접종(接種) 7일(日) 이후(以後)에는 22.0%로 감소(減少)되었다.