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Characterization of aluminized RDX for chemical propulsion
Jai-ick Yoh,Yoocheon Kim,Bohoon Kim,Minsung Kim,Kyung-Cheol Lee,Jungsu Park,Seungho Yang,Honglae Park 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.
Jai-ick YOH,D. Scott STEWART 한국산업응용수학회 2005 한국산업응용수학회 학술대회 논문집 Vol.- No.-
We describe the results in [1,2] concerning a thermomechanical model for an energetic material that uses two independent state variables to represent the phase transformation and the extent of chemical reaction. The presented model is thermodynamically self-consistent and can describe a material that undergoes phase transitions from solid to liquid to gas with exothermic chemical reaction. In various limits, the material is a classical elastic solid, a Newtonian viscous liquid, and a compressible gas.
Innovative Modeling of Explosive Shock Wave Assisted Drug Delivery
Jai-Ick Yoh(여재익),Ki-Hong Kim(김기홍),Kyung-Cheol Lee(이경철),Hyun-Hee Lee(이현희),Kyoung-Jin Park(박경진) 한국연소학회 2006 KOSCOSYMPOSIUM논문집 Vol.- No.-
Recent advances in energetic materials modeling and high-resolution hydroeode 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 fur treatments such as kidney stone removal, trans-dermal micro-particle delivery, and cancer cell removal. 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.
Characterization of aluminized RDX for chemical propulsion
Yoh, Jai-ick,Kim, Yoocheon,Kim, Bohoon,Kim, Minsung,Lee, Kyung-Cheol,Park, Jungsu,Yang, Seungho,Park, Honglae The Korean Society for Aeronautical and Space Scie 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.
Innovative Modeling of Explosive Shock Wave Assisted Drug Delivery
여재익(Jai-Ick Yoh),김기홍(Ki-Hong Kim),이경철(Kyung-Cheol Lee),이현희(Hyun-Hee Lee),박경진(Kyoung-Jin Park) 한국연소학회 2006 한국연소학회지 Vol.11 No.4
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. 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 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.
여재익(Jai-ick Yoh) 한국항공우주학회 2009 韓國航空宇宙學會誌 Vol.37 No.1
정상파 시스템의 구조는 발열반응으로 상변화를 하는 물질의 연속방정식에 의해 타당성을 검증받는다. 1차원 연속체 충격 구조 분석에서의 이론적 배경을 기반으로, 상변화 현상과 관련된 파의 마이크로 두께를 산출하였다. 상변화를 하는 물질로써, n-heptane은 탄화수소 연료의 증발과 응축 분석에 사용하였고, HMX은 고체 로켓 연료의 용융과 응고 분석에 사용하였다. n-heptane의 증발-응축 변의 산출 두께는 10?²마이크론 차수이고, 반면에 HMX의 용융-응고 변의 산출 두께는 1 마이크론 차수 이다. 소개된 상변 두께 산출 이론은 실험적으로 얻을 수 없는 방대한 범위의 에너지 물질까지 계산범위를 확장시킬 수 있다. The structure of steady wave system is considered which is admitted by the continuum equations for materials that undergo phase transformations with exothermic chemical reaction. With its theoretical basis in one-dimensional continuum shock structure analysis, the present approach estimates the micro-width of waves associated with phase transformation phenomena. n-heptane is selected as the hydrocarbon fuel for evaporation and condensation analysis while HMX is used for melting and freezing analysis of solid rocket propellant. The estimated thickness of evaporation - condensation front of n-heptane is on the order of 10?²micron while the HMX melting - freezing front thickness is estimated at 1 micron.