• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.634-643
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• 2004

In this paper are presented a concept of a new supersonic air inlet, which is designated a Multi-Row Disk (MRD) inlet, aiming at performance improvement under off-design conditions, and results of wind tunnel tests examined performance characteristics of the MRD inlet. The MRD inlet is frequently called ‘a skeleton inlet’ because of its appearance. The performance of a conventional axisymmetric inlet with a solid center body (spike) deteriorates under off-design Mach number conditions. It is due to the fact that total pressure recovery (TPR) governed by the throat area of inlet and mass capture ratio (MCR) governed by an incidence position of an oblique shock from the spike tip into the cowl can not be controlled independently in such air inlet. The MRD inlet has the spike that is composed of a tip cone and several disks arranged downstream of it, based on the experimental fact that several deep cavities on a conical surface have little negative effect on the boundary layer growth. The overall spike length of the MRD inlet is adjustable to the given flight speed by changing space between disks so that a spillage flow can be controlled independently from controlling the throat area. It could be made clear from the result of wind tunnel tests that the MRD inlet improves TPR by 10% compared with a conventional inlet with a solid spike under off-design conditions.

• 천문학논총
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• 제32권1호
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• pp.225-230
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• 2017

The extragalactic background suggests half the energy generated by stars was reprocessed into the infrared (IR) by dust. At z~1.3, 90% of star formation is obscured by dust. To fully understand the cosmic star formation history, it is critical to investigate infrared emission. AKARI has made deep mid-IR observation using its continuous 9-band filters in the NEP field ($5.4deg^2$), using ~10% of the entire pointed observations available throughout its lifetime. However, there remain 11,000 AKARI infrared sources undetected with the previous CFHT/Megacam imaging (r ~25.9ABmag). Redshift and IR luminosity of these sources are unknown. These sources may contribute significantly to the cosmic star-formation rate density (CSFRD). For example, if they all lie at 1< z <2, the CSFRD will be twice as high at the epoch. We are carrying out deep imaging of the NEP field in 5 broad bands (g, r, i, z, and y) using Hyper Suprime-Camera (HSC), which has 1.5 deg field of view in diameter on Subaru 8m telescope. This will provide photometric redshift information, and thereby IR luminosity for the previously-undetected 11,000 faint AKARI IR sources. Combined with AKARI's mid-IR AGN/SF diagnosis, and accurate midIR luminosity measurement, this will allow a complete census of cosmic star-formation/AGN accretion history obscured by dust.

• 천문학논총
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• 제27권4호
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• pp.321-324
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• 2012

Using extensive mid-IR datasets from AKARI, i.e. 9-band photometry covering the wavelength range from $2{\mu}m$ to $24{\mu}m$ and the unbiased spectroscopic survey for sources with $S_{\nu}$($9{\mu}m$)>0.3 mJy, we study starburst galaxies specifically at the redshift of z ~ 0.5, whose mid-IR spectra are clearly dominated by the PAH emission features. PAH-selected galaxies, selected with extremely red mid-IR colour due to PAHs, have high rest-frame PAH-to-stellar luminosity ratios, comparable to those in the most active regions in nearby starburst galaxies. Thus, they seem to have active starburst regions spreading over the whole body. Furthermore, some of PAH-selected galaxies are found to have peculiar rest-frame 11-to-$8{\mu}m$ flux ratios, which is systematically smaller than nearby starburst/AGN spectral templates. This may indicate a systematic difference in the physical condition of ISM between nearby and distant starburst galaxies.

• 천문학논총
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• 제27권4호
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• pp.357-360
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• 2012

This paper presents $H{\alpha}$ emission line detections for four galaxies at z > 3.5 made with AKARI as part of the FUHYU mission program. These are the highest-redshift $H{\alpha}$ detections to date in star-forming galaxies. AKARI's unique near-infrared spectroscopic capability has made these detections possible. For two of these galaxies, this represents the first evidence of their redshifts and confirms their physical association with a companion radio galaxy. The star formation rates (SFRs) estimated from the $H{\alpha}$ lines under-predict the SFRs estimated from their far-infrared luminosities by a factor of ~ 2 - 3. We have also detected broad $H{\alpha}$ components in the two radio galaxies which indicate the presence of quasars.

• International Journal of Aeronautical and Space Sciences
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• 제9권2호
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• pp.48-57
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• 2008

The noise is one of the serious problems concerning helicopters operations. The issue of helicopter external noise generated mainly from a helicopter rotor has always affected the use of rotorcrafts, especially in the urban environment. The noise sources depend on the flight configurations. In particular, a noise generated by the interaction between blades and tip vortices mainly occurs during descent flight. This noise is called blade-vortex interaction (BVI) noise, and this BVI noise is particularly penalizing for helicopters. In this paper, a numerical study to capture the BVI noise is carried out. The numerical study is performed in two phases. In the first phase, a 2D simulation based on parallel BYI event of Kitapliglu et al experiment is performed. In the second phase, 3D simulation based on HART Ⅱ experiment is performed. Several experimental data such as thrust, torque, blade sectional load, its derivative and vortex location are compared with calculation results and the comparison showed reasonably good agreement.

• 천문학회보
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• 제36권2호
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• pp.93.2-93.2
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• 2011

Japan Aerospace Exploration Agency (JAXA) has measured space environment and its effects on spacecraft and astronaut since 1987. At present, we have operated space environment monitors onboard one GEO spacecraft, one QZO spacecraft, and two LEO spacecrafts. The obtained space environment data has been gathered into the Space Environment and Effects System database (SEES, http://sees.tksc.jaxa.jp/). In this presentation, measurement result of space environment in low earth orbit obtained by the Daichi satellite from 2006 through 2011 is reported as well as recent activities in space environment engineerings in JAXA. The Technical Data Acquisition Equipment (TEDA) on board the Daichi satellite (Advanced Land Observing Satellite: ALOS) had been operated in low earth orbit at 700 km altitude with 98 degree inclination from February 2006 until April 2011. The TEDA consists of the Light Particle Telescope and the Heavy Ion Telescope. The operation period of the Daichi satellite was through the solar-activity minimum period. The space radiation environment around the Daichi satellite had been almost stable. However, large solar flares followed by CMEs sometimes disturbed the space radiation environment in the orbit of the Daichi satellite. In addition, high speed solar wind often flowed and modulated the electron flux in the horn region. On the other hand, a little variation was seen in the SAA region.

• 항공우주정책ㆍ법학회지
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• 제28권2호
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• pp.349-384
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• 2013

1957년 스푸트니크 1호 발사 이후 세계는 우주활동에 대한 국제적 규범의 필요성을 인식하였으며, 유엔은 우주의 평화적 이용위원회를 설립하여 이러한 문제들을 검토하여 왔다. 1960년대는 미소가 군사적 우주활동을 중심으로 하여왔으나, 최근에는 민간의 우주활동들도 상당히 증가되고 있다. 특히, 우주활동으로 인한 사회적, 경제적 혜택은 더욱 가시화됨에 따라, 각국은 우주 활동에 대한 민간 지출을 계속 증가 시키고 있다. 거의 모든 새로운 우주활동에 참여하는 국가들은 사회 및 경제 개발을 지원하기 위해 우주기반 활동에 더욱 중점을 두고 있다. 위성 항법 및 지상관측과 같은 우주활동들은 기존의 민간 우주 프로그램의 핵심이다. 이와 더불어 달 탐사는 중국, 러시아, 인도, 일본 등 우주력이 있는 국가들에게 우선순위가 되어가고 있다. 최근 위성 및 지상 장비를 제조하는 회사들은 상당한 성장을 하고 있다. 중국은 2012년 2월 25일 자체 개발한 지구항법 위성시스템을 위한 열한 번째 위성을 성공적으로 발사하였다. 중국은 1986년에 중국 만리장성 산업주식회사에 부여된 우주활동으로부터 발전하기 시작했다. 중국 항천공사는 1993년 중국의 국가우주국의 설립에 이어, 창설되었다. 일본의 민간우주활동은 1960년에 창설된 국가우주활동위원회에 의해 이루어졌다. 대부분의 활동은 동경대학, 국립항공 우주 연구소 항공과학연구소 및 국립 우주 개발 기구에 의해 수행 되었다. 2003년에 이 모든 활동들은 일본 우주항공개발연구기구(JAXA)로 통합되었다. 일본은 군사적인 우주개발에 대한 제한을 완화하였다. 2012년 6월 일본은 우주기본법을 수정하여 JAXA을 포함한 일본의 우주 정책과 예산을 통제할 수 있는 권한과 조직을 개편하였다. 과거 문화체육부에 소속되어 있던 우주 프로그램의 개발에 대한 책임을 수상직할로 변경하였다. 그리고 JAXA를 규율하던 우주기본법 제4조의 "평화적인 목적으로만 사용" 한다는 조항을 삭제함으로써 비공격적인 군사적 우주활동을 할 수 있게 되었다. 이로써 동아시아의 긴장이 증대되는 시점에서 국가방위를 강화하기 위한 목적에서 우주를 이용하기 위한 가능성을 열어놓았다. 이러한 점에서 아시아의 상업적 우주활동을 발전시키기 위한 협력적 기구 창설이 필요하다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.702-702
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• 2004

• 항공우주
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• 통권96호
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• pp.38-41
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• 2007

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.1-1
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• 2009