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Characterization of aluminized RDX for chemical propulsion
여재익,김유천,김보훈,김민성,이경철,박정수,양승호,박홍래 한국항공우주학회 2015 International Journal of Aeronautical and Space Sc Vol.16 No.3
The chemical response of energetic materials is analyzed in terms of 1) the thermal decomposition under the thermal stimulus and 2) the reactive flow upon the mechanical impact, both of which give rise to an exothermic thermal runaway or an explosion. The present study aims at building a set of chemical kinetics that can precisely model both thermal and impact initiation of a heavily aluminized cyclotrimethylene-trinitramine (RDX) which contains 35% of aluminum. For a thermal decomposition model, the differential scanning calorimetry (DSC) measurement is used together with the Friedman isoconversional method for defining the frequency factor and activation energy in the form of Arrhenius rate law that are extracted from the evolution of product mass fraction. As for modelling the impact response, a series of unconfined rate stick data are used to construct the size effect curve which represents the relationship between detonation velocity and inverse radius of the sample. For validation of the modeled results, a cook-off test and a pressure chamber test are used to compare the predicted chemical response of the aluminized RDX that is either thermally or mechanically loaded.
여재익,함휘찬,김용현,육승근 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.6
A microjet with a velocity of approximately 140 m/s and 150 μm diameter is injected into a narrow nozzle by a pressure wave delivered by laser-induced bubble expansion. The driving force of such an injector is a discontinuous pulse of a 10 Hz period. Every time a pulse ends, unnecessary air bubbles are introduced into the injector due to the decrease in its internal pressure. Such air bubbles interfere with the flow inside the injector, deteriorating its performance. Therefore, we developed a nozzle closure that reacts automatically to the driving force with a pulse shape. When the flow occurs, the nozzle is opened; when it does not, the nozzle is closed to prevent unnecessary air inflow. In this study, a microjet injector was applied to needle-free drug injection. We compared and analyzed the drug penetration performance of the injector with and without the nozzle closure attached to the injector.
여재익(Jai-ick Yoh),김기홍(Ki-Hong Kim),이경철(Kyung-Cheol Lee),이현희(Hyun-Hee Lee),박경진(Kyoung-Jin Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
??Recent advances in energetic materials modeling and high-resolution hydrocode simulation enable enhanced computational analysis of bio-medical treatments that utilize high-pressure shock waves. Of particular interest is in designing devices that use such technology in medical treatments. For example, the generated micro shock waves with peak pressure on orders of 10 ㎬ can be used for treatments such as kidney stone removal, trans-dermal micro-particle delivery, and cancer cell removal.<br/> ??In this work, we present a new computational methodology for applying the high explosive dynamics to bio-medical treatments by making use of high pressure shock physics and multi-material wave interactions. The preliminary calculations conducted by the in-house code, GIBBS2D, captures various features that are observed from the actual experiments under the similar test conditions. We expect to gain novel insights in applying explosive shock wave physics to the bio-medical science involving drug injection. Our forthcoming papers will illustrate the quantitative comparison of the modeled results against the experimental data.
레이저 펄스 에너지를 이용한 무통증 마이크로젯 약물전달시스템
여재익(Jai-ick Yoh),한태희(Tae-hee Han),하정무(Jung-moo Hah) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
A laser based needle-free liquid drug injection device has been developed. A laser beam is focused inside the liquid contained in the rubber chamber of micro scale. The focused laser beam causes explosive bubble growth, and the sudden volume increase in a sealed chamber drives a microjet of liquid drug through the micronozzle, The exit diameter of a nozzle is less than 100 11m and we verify the injected microjet is fast enough to penetrate human soft tissue. In the experiment, the microjet penetrated 5% gelatin-water solution, which replicates human thrombus, and pork fat tissue.
레이저 펄스 에너지를 이용한 무통증 마이크로젯 약물전달시스템
여재익(Jai-ick Yoh),한태희(Tae-hee Han),하정무(Jung-moo Hah) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.5
레이저 기반의 무바늘 액체 약물전달장치는 계속해서 개발되어왔다. 레이저 빔이 고무 챔버 내부의 액체에 모이게 된다. 초점이 맞춰진 레이저 빔은 공기방울을 생성시키고 급격히 팽창하게 된다. 밀봉된 챔버 안쪽에서의 급격한 부피변화는 액체약물을 마이크로 노즐을 통해 빠르게 밀어내어 마이크로 약물젯을 생성한다. 노즐의 출구지름은 100 ㎛ 이하이며 본 연구팀은 생성된 마이크로 약물젯의 속도가 인체의 연조직으로 침투시키기에 충분함을 확인하였다. 이 실험에서는 사람의 혈전을 모사한 무게 비 5%의 젤라틴 수용액을 냉각시킨 샘플과 돼지 지방층을 사용하여 침투실험을 수행하였다. We have developed a laser-based needle-free liquid drug-injection device. A laser beam is focused inside the liquid contained in the rubber chamber of a micro-scale. The focused laser beam causes explosive bubble growth, and the sudden volume increase in a sealed chamber drives a microjet of liquid drug through the micronozzle. The exit diameter of a nozzle is less than 100 ㎛, and we verify that the injected microjet is fast enough to penetrate soft human tissue. In the experiment, the microjet penetrated a 5% gelatin-water solution that replicates the human thrombus and pork-fat tissue.