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Sausage oscillations in a plasma cylinder with a surface current
Lim, Daye,Nakariakov, Valery M.,Moon, Yong-Jae Elsevier 2018 Journal of Atmospheric and Solar-Terrestrial Physi Vol.175 No.-
<P><B>Abstract</B></P> <P>Linear sausage oscillations of a cylinder embedded in a plasma with an azimuthal magnetic field, created by a current on the surface of the cylinder, are studied. Such a plasma configuration could be applied to modelling flaring loops, and magnetic ropes in coronal mass ejections. The plasma is assumed to be cold everywhere. Dispersion relations demonstrate that the lowest radial harmonic of the sausage mode is in the trapped regime for all values of the parallel wave number. In the long-wavelength limit, phase and group speeds of this mode are equal to the Alfvén speed in the external medium. It makes the oscillation period to be determined by the ratio of the parallel wavelength, e.g. double the length of an oscillating loop, to the external Alfvén speed, allowing for its seismological estimations. The application of the results obtained to the interpretation of long-period (longer than a minute) oscillations of emission intensity detected in solar coronal structures, gives reasonable estimations of the external Alfvén speed. Cutoff values of the parallel wavenumber for higher radial harmonics are determined analytically. Implications of this finding to the observational signatures of fast magnetoacoustic wave trains guided by cylindrical plasma non-uniformities are discussed.</P>
Seo, Daye,Lim, Sung Yul,Lee, Jihye,Yun, Jeongse,Chung, Taek Dong American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.39
<P>Light addressable/activated electrochemistry (LAE) has recently attracted attention as it can provide spatially resolved electrochemical information without using pre-patterned electrodes whose sizes and positions are unchangeable. Here, we propose hematite (α-Fe<SUB>2</SUB>O<SUB>3</SUB>) as the photoanode for LAE, which does not require any sort of surface modification for protection or facilitating charge transfer. As experimentally confirmed with various redox species, hematite is stable enough to be used for repetitive electroanalytical measurements. More importantly, it offers exceptionally high spatial resolution so that the “virtual electrode” is exactly as large as the light spot owing to the short diffusion length of the minority carriers. Quantitative analysis of dopamine in this study shows that the hematite-based photoanode is a promising platform for many potential LAE applications including spatially selective detection of oxidizable biomolecules.</P> [FIG OMISSION]</BR>
임헌욱 ( Hernwook Lim ),맹승진 ( Seungjin Maeng ),김다예 ( Daye Kim ),박지원 ( Jiwon Park ),서건 ( Geon Seo ) 한국농공학회 2023 한국농공학회 학술대회초록집 Vol.2023 No.0
논의 물관리 현장에서는 한정된 농업용수의 효율적 활용을 위해 윤환관개, 간단관개 등을 실시하고 있다. 일반적인 논의 물관리는 현지 농업인을 수리시설관리원으로 위촉 운영하는 등 용수이용자와 물관리 기관이 역할을 분담하여 체계적으로 실시하고 있다. 그러나 수리시설 유지관리가 이원화 되어 시·군 관리지역과 한국농어촌공사 관리지역 농업인 간의 형평성 문제가 종종 발생하고 있는 실정이다. 또한 수리시설이 소규모로 분산되어 있어 접근이 어려우며 시설수도 많아 체계적인 관리가 미흡한 실정이다. 뿐만 아니라 농업용수 사용량에 대한 근거자료가 매우 부족하여 국가차원의 수자원 계획 수립 시 농업용수 부분에서 항상 아쉬운 점이 따른다. 이들을 해결하기 위한 하나의 방편으로, 효율적인 농업용수의 공급관리를 위한 모니터링 시스템의 구축이 필요한 시점에 이르렀다. 본 연구는 농업용수 공급과 관리를 위한 시설물인 저수지, 용배수로, 급수공 등과 용수관리 장치인 부력식 제수문, 자동물꼬 등을 포함하여 용수공급 및 관리 현황 파악을 위한 디지털트윈 기반의 통합 모니터링 시스템을 개발하였다. 디지털트윈 구축을 위한 대상지역은 상습적으로 가뭄이 발생하는 도서지역인 충남 태안군 고남면 장곡리에 위치한 장곡저수지 일대로 하였으며, 농업용 관개 시설물, 장치 설치에 따른 제어, 계측 상태 및 수위 정보를 실시간으로 시스템 표출할 수 있도록 개발하였다. 본격적인 용수공급 시기에 운영할 수 있도록 수정 보완한다면, 향후 개발된 본 시스템은 한국농어촌공사 및 지자체에서 실시간 상황판으로 활용할 수 있고, 지속적이고 안정적인 용수관리가 가능한 공급자 및 사용자 간 양방향 의사결정이 가능한 스마트 물관리의 표본이 될 것이다.
CORONAL THICK TARGET HARD X-RAY EMISSIONS AND RADIO EMISSIONS
Lee, Jeongwoo,Lim, Daye,Choe, G. S.,Kim, Kap-Sung,Jang, Minhwan IOP Publishing 2013 ASTROPHYSICAL JOURNAL LETTERS - Vol.769 No.1
<P>A distinctive class of hard X-ray (HXR) sources located in the corona was recently found, which implies that the collisionally thick target model (CTTM) applies even to the corona. We investigated whether this idea can be independently verified by microwave radiations which have been known as the best companion to HXRs. This study is conducted on the GOES M2.3 class flare which occurred on 2002 September 9 and was observed by the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Owens Valley Solar Array. Interpreting the observed energy-dependent variation of HXR source size under the CTTM, the coronal density should be as high as 5 x 10(11) cm(-3) over a distance of up to 12 ''. To explain the cutoff feature of the microwave spectrum at 3 GHz, however, we require a density no higher than 1 x 10(11) cm(-3). Additional constraints must be placed on the temperature and magnetic field of the coronal source in order to reproduce the microwave spectrum as a whole. First, a spectral feature called the Razin suppression requires a magnetic field in a range of 250-350 G along with high viewing angles around 75 degrees. Second, to avoid excess fluxes at high frequencies due to the free-free emission that was not observed, we need a high temperature >= 2 x 10(7) K. These two microwave spectral features, Razin suppression and free-free emissions, become more significant at regions of high thermal plasma density and are essential for validating and determining additional parameters of the coronal HXR sources.</P>