• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2009년도 제33회 추계학술대회논문집
• /
• pp.433-438
• /
• 2009

고체 및 액체 추진기괸에 적용하기 위하여 액체 실리콘 함침법(LSI)을 이용한 C/SiC 복합재료를 개발하였다. 연소시험을 통하여 C/SiC 복합재료의 우수한 성능을 확인하였으며 산화에 의한 삭마 모델을 제시 하였다.

• 한국추진공학회지
• /
• 제14권5호
• /
• pp.32-44
• /
• 2010

고체 추진기관 노즐의 2차원 열반응 및 삭마 해석 코드를 활용하여 노즐 부품의 숯 및 삭마현상을 연구하였다. Arrhenius 식을 이용한 내부 열분해 모델 상수는 TGA(열중량분석기) 실험으로 얻었다. 탄소와 $H_2O$, $CO_2$의 산화반응에 의한 화학적 삭마는 Zvyagin이 제안한 삭마모델 과 반응속도 상수를 이용하여 해석을 수행하였다. 삭마에 의한 경계조건 및 격자 이동은 상용해석 프로그램인 MSC-Marc-ATAS에서 적용되는 Rezoning-remeshing 기법을 사용하였다. 해석된 숯 및 삭마 두께는 연소시험 결과 값과 최대 20% 오차를 보였다. 향후 열방호 시스템의 성능을 모사하기 위하여 내부 온도 및 열유속을 실시간 측정하면 3차원 FEM 통합 열구조 해석에 적용될 것으로 기대된다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.282-287
• /
• 2001

The CSCM Upwind method and Material Transport Analysis (MTA) have been used to predict the thermal response and ablation rate for non-charring material to be used as thermal protection material (TPM) in KSR-III test rocket nozzle. The thermal boundary conditions such as cold wall heat-transfer rate and recovery enthalpy for MTA code are obtained from the upwind Navier-Stokes solution procedure. The heat transfer rate and temperature variations at rocket nozzle wall were studied with shape change of the nozzle surface as time goes by. The surface recession was severely occurred at nozzle throat and this affected nozzle performance such as thrust coefficient substantially.

• Nuclear Engineering and Technology
• /
• 제40권4호
• /
• pp.311-318
• /
• 2008

In modem power reactors, nuclear fuels have recently reached 55,000 MWd/MtU from the initial average burnup of 35,000 MWd/MtU to reduce the fuel cycle cost and waste volume. At such high burnups, a fuel pellet produces fission products proportional to the burnup and creates a typical high burnup structure around the periphery region of the pellet, producing the so called 'rim effect'. This rim region of a highly burnt fuel is known to be ca. $200\;{\mu}m$ in width and is known to affect the fuel integrity. To characterize the local burnup in the rim region, solid sampling in the micro meter region by laser ablation is needed so that the distribution of isotopes can be determined by ICP-MS. For this procedure, special radiation shielding is required for personnel safety. In this study, we installed a radiation shielded laser ablation ICP-MS system, and a performance test of the developed system was conducted to evaluate the safe operation of instruments.

• 한국연소학회지
• /
• 제19권1호
• /
• pp.1-10
• /
• 2014

An analytical study on performance evaluation of superdetonative mode ram accelerator was conducted for understanding the experimental result. The quasi-one dimensional continuum, momentum, energy equations were solved under the assumption of inviscid flow. It would be noticeable that experimental result could be analytically simulated with the assumptions of inlet shockwave, temperature dependent specific heat, and additional aluminum combustion due to ablation of aluminum projectile in superdetonative operation mode. The acceleration of ram accelerator was comparable to experimental result with the consideration of the additional aluminum combustion energy by ablation of projectile. As result, the experimental result with the aluminum projectile could be affected by heat of aluminum.

• 한국항공우주학회지
• /
• 제49권5호
• /
• pp.355-363
• /
• 2021

리오셀계 탄소/페놀릭 복합재료의 항공우주용 내열 부품 적용 가능성을 확인하기 위하여 내열성능 평가 및 열 해석을 수행하였다. 탄소/페놀릭의 열반응 평가는 내열성능평가모터(Thermal Protection Evaluation Motor, TPEM)로 수행되었다. 본 논문에서는 열 해석을 위해 유체의 경계층 해석을 고려한 경계층 적분 코드와 삭마 및 열분해를 고려한 MSC-Marc 2018 코드를 사용하였다. 추진기관의 압력 곡선, 연소 시험 후 절개된 목삽입재 시편을 통하여 삭마 및 단열성능을 분석하였고, 리오셀계 탄소/페놀릭 복합재료의 열반응은 레이온계 탄소/페놀릭 재료와 유사하였다. 연소시험을 통한 결과를 바탕으로 국산 리오셀계 탄소/페놀릭의 항공우주용 내열 부품으로의 적용 가능성을 확인하였다.

• 한국항공우주학회지
• /
• 제38권2호
• /
• pp.200-205
• /
• 2010

고온고압, 장시간 연소조건하에서 일정한 추력을 유지하는 로켓 추진기관 개발을 위해 W/$Y_2O_3$ 노즐목 삽입재를 평가하였다. 연소시간 증가에 따른 내열성능 변화를 검토하였으며, 비삭마 소재로 범용되고 있는 CIT의 내열성능과 비교하였다. 연소시간이 증가함에 따라 삭마율은 감소하는 경향을 보였으며, W/$Y_2O_3$의 삭마율은 CIT의 약 55 %이었다. 노즐목 삽입재의 육안검사와 미세조직검사에서 연소시간의 증가로 인한 특이 현상은 발견되지 않았으며, 진공 열처리는 균열 방지에 효과가 있음을 확인하였다.

• 한국정밀공학회지
• /
• 제29권7호
• /
• pp.799-804
• /
• 2012

Recently micro-nano structures has widely been reported to improve the performance of waterproof, heat isolation, sound and light absorption in various fields of electric devices such as mobiles, battery, display and solar panels. A lot of micro-sized holes on the surface of thin film provide excellent sound, or heat, or light transmission efficiency more than solid film and simultaneously nano-sized protrusions around micro hole increase the hydrophobicity of the surface of thin film because of lotus leaf effects as generally known previously. In this paper new rapid fabrication process with 355 nm UV laser ablation was proposed to get micro-nano structures on the surface of thin film, which have only been observed at higher laser fluence. Developed thin micro-nano structured film was also investigated the hydrophobic property by measuring the contact angle and demonstrated the possibility to apply to water droplet separation.

• Journal of Korean Medical Science
• /
• 제33권44호
• /
• pp.279.1-279.16
• /
• 2018

Magnetic resonance-guided focused ultrasound (MRgFUS) is a new emerging neurosurgical procedure applied in a wide range of clinical fields. It can generate high-intensity energy at the focal zone in deep body areas without requiring incision of soft tissues. Although the effectiveness of the focused ultrasound technique had not been recognized because of the skull being a main barrier in the transmission of acoustic energy, the development of hemispheric distribution of ultrasound transducer phased arrays has solved this issue and enabled the performance of true transcranial procedures. Advanced imaging technologies such as magnetic resonance thermometry could enhance the safety of MRgFUS. The current clinical applications of MRgFUS in neurosurgery involve stereotactic ablative treatments for patients with essential tremor, Parkinson's disease, obsessive-compulsive disorder, major depressive disorder, or neuropathic pain. Other potential treatment candidates being examined in ongoing clinical trials include brain tumors, Alzheimer's disease, and epilepsy, based on MRgFUS abilities of thermal ablation and opening the blood-brain barrier. With the development of ultrasound technology to overcome the limitations, MRgFUS is gradually expanding the therapeutic field for intractable neurological disorders and serving as a trail for a promising future in noninvasive and safe neurosurgical care.

• 전기학회논문지
• /
• 제60권7호
• /
• pp.1417-1426
• /
• 2011

Radiofrequency ablation through cardiac catheterization is one of minimally invasive intervention procedures used in drug resistant arrhythmia treatment. To facilitate more accurate and precise catheter navigation, systems for robotic cardiac catheter navigation have been developed and commercialized. The authors have been developing a novel robotic catheter navigation system. The system is a network-based master-slave configuration 3-DOF (Degree-Of-Freedom) robotic manipulator for operation with conventional cardiac ablation catheter. The catheter manipulation motion is composed of the translation (forward/backward) and the roll movements of the catheter and knob rotation for the catheter tip articulation. The master manipulator comprises an operator handle compartment for the knob and the roll movement input, and a base platform for the translation movement input. The slave manipulator implements a robotic catheter platform in which conventional cardiac catheter is mounted and the 3-DOF motions of the catheter are controlled. The system software that runs on a realtime OS based PC, implements the master-slave motion synchronization control in the robot system. The master-slave motion synchronization performance tested with step, sinusoidal and arbitrarily varying motion commands showed satisfactory results with acceptable level of steady state error. The developed system will be further improved through evaluation of safety and performance in in vitro and in vivo tests.