• 천문학회지
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• 제41권6호
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• pp.173-180
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• 2008

Using the MHD coronal seismology technique, we estimated the magnetic field for three spicules observed in 2008 June. For this study, we used the high resolution Ca II H line ($3968.5\;{\AA}$) images observed by the Hinode SOT and considered a vertical thin flux tube as a spicule model. To our knowledge, this is the first attempt to estimate the spicule magnetic field using the Hinode observation. From the observed oscillation properties, we determined the periods, amplitudes, minimum wavelengths, and wave speeds. We interpreted the observed oscillations as MHD kink waves propagating through a vertical thin flux tube embedded in a uniform field environment. Then we estimated spicule magnetic field assuming spicule densities. Major results from this study are as follows : (1) we observed three oscillating spicules having durations of 5-7 minutes, oscillating periods of 2-3 minutes, and transverse displacements of 700-1000 km. (2) The estimated magnetic field in spicules is about 10-18 G for lower density limit and about 43-76 G for upper density limit. (3) In this analysis, we can estimate the minimum wavelength of the oscillations, such as 60000 km, 56000 km, and 45000 km. This may be due to the much longer wavelength comparing with the height of spicules. (4) In the first event occurred on 2008 June 03, the oscillation existed during limited time (about 250 s). This means that the oscillation may be triggered by an impulsive mechanism (like low atmospheric reconnection), not continuous. Being compared with the ground-based observations of spicule oscillations, our observation indicates quite different one, i.e., more than one order longer in wavelength, a factor of 3-4 larger in wave speed, and 2-3 times longer in period.

• 천문학회지
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• 제48권1호
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• pp.21-55
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• 2015

If the Universe is dominated by cold dark matter and dark energy as in the currently popular ${\Lambda}CDM$ cosmology, it is expected that large scale structures form gradually, with galaxy clusters of mass $M{\geq}10^{14}M_{\odot}$ appearing at around 6 Gyrs after the Big Bang (z ~ 1). Here, we report the discovery of 59 massive structures of galaxies with masses greater than a few times $10^{13}M_{\odot}$ at redshifts between z = 0.6 and 4.5 in the Great Observatories Origins Deep Survey fields. The massive structures are identified by running top-hat filters on the two dimensional spatial distribution of magnitude-limited samples of galaxies using a combination of spectroscopic and photometric redshifts. We analyze the Millennium simulation data in a similar way to the analysis of the observational data in order to test the ${\Lambda}CDM$ cosmology. We find that there are too many massive structures (M > $7{\times}10^{13}M_{\odot}$) observed at z > 2 in comparison with the simulation predictions by a factor of a few, giving a probability of < 1/2500 of the observed data being consistent with the simulation. Our result suggests that massive structures have emerged early, but the reason for the discrepancy with the simulation is unclear. It could be due to the limitation of the simulation such as the lack of key, unrecognized ingredients (strong non-Gaussianity or other baryonic physics), or simply a difficulty in the halo mass estimation from observation, or a fundamental problem of the ${\Lambda}CDM$ cosmology. On the other hand, the over-abundance of massive structures at high redshifts does not favor heavy neutrino mass of ~ 0.3 eV or larger, as heavy neutrinos make the discrepancy between the observation and the simulation more pronounced by a factor of 3 or more.

• 한국비블리아학회지
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• 제27권2호
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• pp.193-212
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• 2016

이 연구의 목적은 도서관이용과 도서관예산 사이에 영향관계가 있는지를 알아보고, 이를 통해 잠재적 이용자들을 도서관으로 유인하기 위해서는 적정예산의 확보가 필요하다는 것을 설명하는데 있다. 다시 말해, 도서관예산은 도서관이용을 증진시킬 수 있는 중요한 요인임을 설명하기 위해 시도되었다. 이를 위해 부산광역시 공공도서관 31개관을 대상으로 국가도서관통계시스템으로부터 확보된 2013년 통계데이터를 사용하여 분석을 실시하였다. 분석을 위해 독립변수는 도서관예산을 설명하는 '총비용지수(TFI: Total Funding Indicator) = $\sqrt{인건비{\times}자료구입비}$'와 도서관이용을 나타내는 'LU(Library Usage) = (연간 방문자수) + (연간 대출자료수) / 봉사대상인구'의 개념을 통해 산출된 값을 종속변수로 사용하였다. 연구결과는 도서관총비용지수(TFI)와 도서관이용(LU) 사이에는 영향관계가 존재하는 것으로 나타났으며, 도서관의 예산이 증가할수록 도서관이용은 증가하는 것으로 설명되었다. 본 연구의 결과가 비록 도서관예산과 도서관이용의 긍정적인 관계를 설명하고 있지만, 분석대상 및 분석기간의 제한성 및 한정성으로 인해 정책결정을 위한 도구로서 활용되기 위해서는 대상의 확대 및 분석기간의 다년화를 통한 타당성이 확보되어야 한다.

• 대기
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• 제23권3호
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• pp.321-329
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• 2013

This study examines the effect of aerosols on the vertical invigoration of continental stratiform clouds, using a dataset of Atmospheric Radiation Measurement (ARM) Intensive Operational Period (IOP, March 2000) at the Southern Great Plains (SGP) site. To provide further support to our observation-based findings, the weather research and forecasting (WRF) sensitivity simulations with changing cloud condensation nuclei (CCN) concentrations have been carried out for the golden episode over SGP. First, cross correlation between observed aerosol scattering coefficient and cloud liquid water path (LWP) with a 160-minutes lag is the highest of r = 0.83 for the selected episode, which may be attributable to cloud vertical invigoration induced by an increase in aerosol loading. Modeled cloud fractions in a control run are well matched with the observation in the perspective of cloud morphology and lasting period. It is also found through a simple sensitivity with a change in CCN that aerosol invigoration (AIV) effect on stratiform cloud organization is attributable to a change in the cloud microphysics as well as dynamics such as the corresponding modification of cloud number concentrations, drop size, and latent heating rate, etc. This study suggests a possible cloud vertical invigoration even in the continental stratiform clouds due to aerosol enhancement in spite of a limited analysis based on a few observed continental cloud cases.

• 한국콘텐츠학회논문지
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• 제16권7호
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• pp.513-521
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• 2016

본 연구는 간호대학생의 분만실 실습 중 수행내용을 파악하고 임상실습 환경에 따른 간호대학생의 실습 수행도 및 만족도를 분석하여 실습의 질 향상을 위한 개선방안을 제시하고자 하였다. 연구결과 간호대학생의 분만실 임상실습은 대부분 관찰 위주로 진행되고 있었고, 제한된 영역에서만 직접수행과 보조적 수행을 경험하였다. 간호대학생의 임상수행 만족도는 69%정도의 비교적 낮은 수준을 보였다. 임상실습지에 따른 차이를 분석한 결과 여성전문병원의 분만실에서 실습 한 간호대학생은 종합병원에서 보다 더 많은 관찰을 수행 할 수 있었고, 그에 따라 만족도 점수 또한 높았다. 분만실 임상실습에서 관찰 및 보조적 수행이 많을수록 만족도는 상승하였다. 결과에서 확인된 실습 중 부족한 직접수행은 시뮬레이션기반 임상실습 등을 통해 보완할 수 있을 것이다. 또한 병원 실무자와의 긴밀한 의사소통을 기반으로 실습지를 확보하고, 다양한 간호대상자를 경험하고 관찰할 수 있도록 지도하는 것은 간호대학생의 임상실습 만족도와 질 향상을 위한 전략으로서 제시될 수 있겠다.

• 대기
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• 제18권4호
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• pp.317-338
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• 2008

Analyses of observational data and numerical simulations were performed to understand the mechanism of MCSs (Mesoscale Convective Systems) occurred on 13-14 July 2004 over Jindo area of the Korean Peninsula. Observations indicated that synoptic environment was favorable for the occurrence of heavy rainfall. This heavy rainfall appeared to have been enhanced by convergence around the Changma front and synoptic scale lifting. From the analyses of storm environment using Haenam upper-air observation data, it was confirmed that strong convective instability was present around the Jindo area. Instability indices such as K-index, SSI-index showed favorable condition for strong convection. In addition, warm advection in the lower troposphere and cold advection in the middle troposphere were detected from wind profiler data. The size of storm, that produced heavy rainfall over Jindo area, was smaller than $50{\times}50km^2$ according to radar observation. The storm developed more than 10 km in height, but high reflectivity (rain rate 30 mm/hr) was limited under 6 km. It can be judged that convection cells, which form cloud clusters, occurred on the inflow area of the Changma front. In numerical simulation, high CAPE (Convective Available Potential Energy) was found in the southwest of the Korean Peninsula. However, heavy rainfall was restricted to the Jindo area with high CIN (Convective INhibition) and high CAPE. From the observations of vertical drop size distribution from MRR (Micro Rain Radar) and the analyses of numerically simulated hydrometeors such as graupel etc., it can be inferred that melted graupels enhanced collision and coalescence process of heavy precipitation systems.

• 한국농공학회논문집
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• 제59권3호
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• pp.29-39
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• 2017

In this study, the GPM (Global Precipitation Mission) IMERG (Integrated Multi-satellitE retrievals for GPM) rainfall data was verified and evaluated using ground AWS (Automated Weather Station) and radar in order to investigate the availability of GPM IMERG rainfall data. The SPI (Standardized Precipitation Index) was calculated based on the GPM IMERG data and also compared with the results obtained from the ground observation data for the Hoengseong Dam and Yongdam Dam areas. For the radar data, 1.5 km CAPPI rainfall data with a resolution of 10 km and 30 minutes was generated by applying the Z-R relationship ($Z=200R^{1.6}$) and used for accuracy verification. In order to calculate the SPI, PERSIANN_CDR and TRMM 3B42 were used for the period prior to the GPM IMERG data availability range. As a result of latency verification, it was confirmed that the performance is relatively higher than that of the early run mode in the late run mode. The GPM IMERG rainfall data has a high accuracy for 20 mm/h or more rainfall as a result of the comparison with the ground rainfall data. The analysis of the time scale of the SPI based on GPM IMERG and changes in normal annual precipitation adequately showed the effect of short term rainfall cases on local drought relief. In addition, the correlation coefficient and the determination coefficient were 0.83, 0.914, 0.689 and 0.835, respectively, between the SPI based GPM IMERG and the ground observation data. Therefore, it can be used as a predictive factor through the time series prediction model. We confirmed the hydrological utilization and the possibility of real time drought monitoring using SPI based on GPM IMERG rainfall, even though results presented in this study were limited to some rainfall cases.

• 한국항공우주학회지
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• 제42권9호
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• pp.779-788
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• 2014

저궤도 위성이 제한된 전력 내에서 임무를 성공적으로 수행하기 위해서는 효율적인 전력생산이 중요하다. 이를 위해 저궤도 소형위성의 전력계에서는 주로 MPPT (Maximum Power Point Tracking) 방식을 사용하여 태양전지에서 생산되는 전력을 조절한다. 본 연구에서는 소형 큐브위성(KAUSAT-5)에 적용될 퍼지 로직 기반의 MPPT 알고리즘을 제안하며, 제안된 방법의 유용성을 확인하기 위해 MATLAB/Simulink와 STK (Systems Tool Kit)를 연동하여 시뮬레이션을 수행하였다. Simulink와 STK를 이용하여 위성 궤도와 자세에 따른 태양 광량과 운용모드에 따라 변하는 부하용량에 대해 KAUSAT-5의 두 가지 지향모드에서 EBA(Energy Balance Analysis)를 수행하였고, 이를 통해 제안된 퍼지 로직 기반의 MPPT 알고리즘의 성능을 확인하였다. 제안된 퍼지 로직 기반의 MPPT는 가장 일반적인 방법의 하나인 P&O (Perturbation & Observation)와 성능을 비교하여 유용성을 확인하였다.

• 한국수학교육학회지시리즈C:초등수학교육
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• 제20권1호
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• pp.101-115
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• 2017

본 연구의 목적은 초등 예비교사들의 관점에서 수학 수업을 관찰하면서 동기 유발의 측면을 중심으로 동기 유발의 내용 및 방법, 그리고 예비교사들의 동기 유발에 대하여 분석하는 것이다. 연구 참여자들은 서울 지역의 2학년 또는 3학년에 재학 중인 예비교사 62명이었다. 이 예비교사들이 1주 또는 2주간의 교육실습 중 수학수업의 동기 유발 부분을 집중적으로 관찰한 후, 자신들의 관점에서 수학 수업에서의 동기 유발에 대한 분석한 결과와 의견을 제시하도록 하였다. 연구 결과, 예비교사들은 동기 유발을 주로 학생들의 흥미를 진작하기 위한 것과 주위집중을 위한 것으로 생각하였다. 동기 유발의 시간은 평균 5분 50초이고, 제한된 자료만을 사용하여 동기를 유발하였다. 연구자는 동기 유발 내용 및 방법이 차시의 목표와 세밀하게 연계할 수 있는 방안에 대한 후속 연구를 제언하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.180-185
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• 2001

In order to regulate the physical characteristics of an ocean dumping material in the south-eastern East Sea, the diffusion characteristics with the observation, hydraulic experiment and numerical experiment data are investigated. The main results are as follows; (1) Spying CTD observation result of the area of Jung in the East Sea, the ocean dumping area had influenced the Tsushima warm current of high temperature and salinity. Horizontal turbulent diffusivity is 1.913${\times}$10$^{7}$ $\textrm{cm}^2$/sec by drogue tracking. (2) From the experiment of settling, the initial settling velocity of each material is 1.0∼2.7 cm/sec according to the specific gravity and initial concentration. In the pycnocline, particles didn't settle under the pycnocline any more and accumulated. It is signified that calculation of the sedimentation rate of the ocean dumping material including of vertical diffustion must be regard the pycnocline in the ocean area have well-developed pycnocline. (3) Vertical turbulent diffusivity were 2.219${\times}$10$^{-8}$∼8,874${\times}$10$^{-4}$ $\textrm{cm}^2$/sec from the experiment of settling. And, the pycnocline influenced the vertical turbulent diffusivity. (4) From the result of diffusion simulation in the East Sea, the co-concentration line of 0.05 ppm and 0.1 ppm are limited at dumping area after 200 days. The constant concentration line of 0.01 ppm is distributed to the vicinity of Ulleungdo and Tokdo, but isn't distributed to the coastal area of East Sea and southern area of Jung in the East Sea.