• 한국분무공학회지
• /
• 제28권4호
• /
• pp.169-175
• /
• 2023

Multi-injection scheme is being applied to GDI combustion to reduce PM and PN emission to meet the EU7 regulation. However, very short injection duration encounters the ballistic injection region, which injection quantity does not increase linearly with injection duration when applying multi-injection. In this study, numerical studies were conducted to reveal the cause of ballistic injection and the effect of design parameters on ballistic region using 1-D simulation, AMESim. Injection rate and injection quantity were compared with experiment to validate the established model, which showed the accuracy with 10% error. The model revealed that the tendency of ballistic region coincides with the needle motion behavior, which means that parameters at the upper part of needle such as electro-magnetic force, needle spring force and needle friction force have dominant effect on ballistic injection. To figure out the effect of electro-magnetic and needle friction force on ballistic, those parameters were varied to plus and minus 10% with model. The result showed that those parameters clearly changed the ballistic region characteristics, however, the impact became insignificant for outside of ballistic region, which means that the ballistic injection is mainly influenced by initial motion of injector needle.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제9권1호
• /
• pp.55-60
• /
• 2009

The channel backscattering coefficient and injection velocity have been extracted experimentally in 65nm MOSFETs. Thanks to an experimental extraction methodology taking into account multi-subband population, we demonstrate that the short channel ballistic efficiency is slightly greater than long channel ballistic efficiency.

• Journal of Astronomy and Space Sciences
• /
• 제40권3호
• /
• pp.123-129
• /
• 2023

This paper presents an analysis of the trans-lunar trajectory insertion performance of the Korea Pathfinder Lunar Orbiter (KPLO), the first lunar exploration spacecraft of the Republic of Korea. The successful launch conducted on August 4, 2022 (UTC), utilized the SpaceX Falcon 9 rocket from Cape Canaveral Space Force Station. The trans-lunar trajectory insertion performance plays a crucial role in ensuring the overall mission success by directly influencing the spacecraft's onboard fuel consumption. Following separation from the launch vehicle (LV), a comprehensive analysis of the trajectory insertion performance was performed by the KPLO flight dynamics (FD) team. Both orbit parameter message (OPM) and orbit determination (OD) solutions were employed using deep space network (DSN) tracking measurements. As a result, the KPLO was accurately inserted into the ballistic lunar transfer (BLT) trajectory, satisfying all separation requirements at the target interface point (TIP), including launch injection energy per unit mass (C3), right ascension of the injection orbit apoapsis vector (RAV), and declination of the injection orbit apoapsis vector (DAV). The precise BLT trajectory insertion facilitated the smoother operation of the KPLO's remainder mission phase and enabled the utilization of reserved fuel, consequently significantly enhancing the possibilities of an extended mission.

• EDISON SW 활용 경진대회 논문집
• /
• 제5회(2016년)
• /
• pp.357-361
• /
• 2016

Si와 InAs 두 가지 채널 물질을 가지고 3가지 수송 방향 <100>, <110>, <111>으로 변화시키며 각각의 Nanowire nMOSFETs을 가지고 ballistic quantum transport simulation을 진행하였다. 각각의 경우에 대해 E-k curve를 구한 다음에 band curvature로 캐리어의 유효질량을 계산하고, 이를 통해 MOSFET의 전류 세기를 결정짓는 DOS와 carrier injection velocity를 구하여 어떤 경우에 가장 높은 ON-current를 흐르게 하는지 확인해 보았다. 하지만 예상과 달리 나노와이어의 직경이 1.4nm으로 매우 작기 때문에 valley-splitting이 일어나 Si<110>의 경우에 가장 작은 캐리어 유효 질량을 갖고 있는 사실을 확인할 수 있었다. 결론적으로 Si<100>의 경우에 trade-off 관계에 있는 DOS와 carrier injection velocity가 6가지 경우 중 최적의 조합을 가짐으로써 가장 높은 ON-current를 흐르게 하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2010년도 제35회 추계학술대회논문집
• /
• pp.177-180
• /
• 2010

고압관, 가압관, 발사관으로 구성된 Ballistic Range의 일종인 2단식 경가스 총을 사용하여 초음속 액체 제트의 분무 특성을 연구하였다. 135 bar의 압축공기는 고압관과 가압관 사이에 OHP필름으로 구성된 격막을 파열시킨 후 가압관의 발사체를 약 250 m/s의 속도로 가속하였다. 가속된 발사체는 액체 저장부에 충돌하여 액체를 초고압으로 가압한 후 초음속으로 분사시키며, 특히 초음속 액체 제트는 미립화된 다중 제트의 형태를 나타내고 액체 제트 전방 영역에서 충격파를 수반한다. 다양한 분사 노즐의 기하학적 형상에 대한 분무시험결과 초음속 액체 제트의 속도와 충격파 각도가 각각 다르게 생성되었으며, L/d가 9.9, 11.9, 23.8의 조건에 대하여 L/d가 23.8의 경우에 액체 제트의 분사속도가 마하수 1.53으로 가장 낮게 측정되었다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
• /
• pp.350-355
• /
• 2012

최근 다양한 공학 응용 분야에 Micro Shock Tube의 중요성이 커지고 있다. Pharma Ballistic 기술은 기존의 약물주입방법과 달리 약물입자를 가속하여 피부로 침투시키기 위해 Micro Shock Tube를 적용하는 기술 중 하나이다. 그러나 이러한 장치의 효율적인 설계를 위해서는 Micro Shock Tube 내부유동과 충격특성에 대한 상세한 지식을 필요로 한다. 경계층과 같은 많은 요소들 때문에 Micro Shock Tube 내부의 낮은 Reynolds Number와 높은 Knudsen Number가 형성되며, 이 때의 충격파 전파는 기존의 Macro Shock Tube와 상이하게 나타난다. 본 연구에서는 Micro Shock Tube에서의 충격파 전파와 유동특성을 조사하기 위해 직경 3mm의 Micro Shock Tube를 이용하여 실험을 수행하였으며, 압력은 저압관의 세 지점에서 측정되었다. 충격파 속도와 같은 다른 변수들의 실험값으로부터 충격파 강도를 찾고 충격파 선도를 나타내었다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.490-490
• /
• 2011

Graphene, hexagonal network of carbon atoms forming a one-atom thick planar sheet, has been emerged as a fascinating material for future nanoelectronics. Huge attention has been captured by its extraordinary electronic properties, such as bipolar conductance, half integer quantum Hall effect at room temperature, ballistic transport over ${\sim}0.4{\mu}m$ length and extremely high carrier mobility at room temperature. Several approaches have been developed to produce graphene, such as micromechanical cleavage of highly ordered pyrolytic graphite using adhesive tape, chemical reduction of exfoliated graphite oxide, epitaxial growth of graphene on SiC and single crystalline metal substrate, and chemical vapor deposition (CVD) synthesis. In particular, direct synthesis of graphene using metal catalytic substrate in CVD process provides a new way to large-scale production of graphene film for realization of graphene-based electronics. In this method, metal catalytic substrates including Ni and Cu have been used for CVD synthesis of graphene. There are two proposed mechanism of graphene synthesis: carbon diffusion and precipitation for graphene synthesized on Ni, and surface adsorption for graphene synthesized on Cu, namely, self-limiting growth mechanism, which can be divided by difference of carbon solubility of the metals. Here we present that large area, uniform, and layer controllable graphene synthesized on Cu catalytic substrate is achieved by acetylene-assisted CVD. The number of graphene layer can be simply controlled by adjusting acetylene injection time, verified by Raman spectroscopy. Structural features and full details of mechanism for the growth of layer controllable graphene on Cu were systematically explored by transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy.