• 대한핵의학회지
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• 제27권1호
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• pp.51-58
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• 1993

We have anlayzed the polar maps of dipyridamole stress/rest $^{99m}Tc$-MIBI SPECT and compared the quantitated perfusion defects of dipyridamole stress polar map and the findings of coronary angiography in 56 pateints with coronary artery diseases. We performed the same day dipyridamole stress-rest myocardial SPECT, reconstructed the polar maps according to Cedars-Sinai method and quantitated perfusion detects of total myocardium and the territory of each artery, comparing the polar maps of patients with normal files. Stenosis more than 50 percent was considered significant and myocardial ischemic score was calculated as summed score of percents of main coronary arteries. Positive concordance of myocardial SPECT with coronary angiography were 82.6% with left anterior descending artery (LAD), 85.7% with left circumflex artery (LCx) and 78.6% with right coronary artery (RCA). Perfusion defect of SPECT polar map and the stenosis of coronary artery showed the contingency phi of 0.55 (p<0.0001) with total atreries, 0.38 (p = 0.016) with LAD, 0.50 (p<0.0001) with LCx and 0.40 (p = 0.007) with RCA. Dipyridamole stress percent defect of polar map was correlated with myocardial ischemic score with Spearman's rho of 0.47 (p = 0.001) in total arteries, 0.48 (p=0.001) in LAD, 0.56 (p < 0.001) in LCx and 0.38 (p=0.002) in RCA. These findings revealed that defect of the dipyridamole stress myocardial $^{99m}Tc$-MIBI SPECT and the percent extent of this defect were related with significant artery stenosis of individual arteries and the degree of stenosis. We thought that we could use the defects in the polar map of dipyridamole stress $^{99m}Tc$-MIBI SPECT for the quantification of myocardiasl perfusion decrease.

• Ocean and Polar Research
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• 제25권1호
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• pp.41-52
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• 2003

Sediment trap samples were collected to find out characteristic behaviors of metals in the settling particles by using time-series sediment traps at 678m and 1678m water depths in the Bransfield Strait from December 27th, 1999 to December 26th, 2000. Total mass fluxes at the intermediate water depth (678m water depth) were high in the austral summer and low in the austral winter, whereas at the deep water depth (1678m water depth) they showed high values in both the summer and winter. Total mass fluxes were generally higher in the deep water depth than in the intermediate water depth, which indicates that a substantial amount of sediments are laterally transported by strong currents into the deep basin from the shallow water depths. Aluminium contents also showed large seasonal variations with high values in the winter and low values in the summer. On the contrary, organic carbon contents were high in the summer and low in the winter. Al contents were negatively correlated with organic carbon contents, which may be ascribed that detrital particles are diluted by organic matter produced by phytoplankton in the surface waters. Metals measured in this study exhibited three characteristic behaviors; 1) a positive correlation with Al-Ti, Fe, Mn, V, Co, and Ba, 2) a negative correlation with Al-Cd and Zn, 3) no relationship with Al-Sr, Cu, Cr, Ni. Terrestrial materials may act as a major source fer metals that are positively correlated with Al, and organic matter may be a major source for metals that are negatively correlated with Al. Enrichment factor (EF) of Fe, Mn, Ba, Vi Co, Sr, Cr, and Ni ranged from 0.5 to 1.5, whereas EF of Zn, Cu, and Cd showed much higher values than 1.

• 지구물리
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• 제8권3호
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• pp.159-167
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• 2005

Turbulent fluxes of sensible heat and latent heat were analyzed at King Sejong station in the austral summer of 2002 (December) and 2003 (January and February). Monthly mean air temperatures of January and February (2.2oC) were similar to those averaged over 1988 to 2001. Precipitation was less in January and greater in February than those averaged over last 14 years. In December of 2002 and January, there was precipitation primarily when easterly wind blew usually. The frequency of snowfall was equal to or larger than that of rainfall. In the mean while, precipitation primarily in forms of rainfall occurred with westerly wind in February. In addition, while for easterly wind, temperature and humidity was low, temperature and humidity were high in case of westerly wind. Based on flux footprint, measured flux mainly came from within 300 m with maximum of 40 m upwind, indicating the insignificant role of the sea around the study site. Half-hourly downward short wave radiation amounted up to ∼ 1000 Wm-2 and net radiation ranged from -50 to 600 Wm-2. Half-hourly sensible heat flux was positive at daytime with maximum of ∼ 400 Wm-2, except the 27th and 28th in February of 2003 when it was negative all day despite of positive net radiation at short daytime. Latent heat flux was positive with maximum of ∼ 130 Wm-2. Depending on wind direction, the partitioning of net radiation into the sum of sensible heat flux and latent heat flux was larger than 0.8, indicating the strong source of the land surface for the atmospheric heating. The daytime averaged Bowen ratio (=sensible heat flux /latent heat flux) was significantly greater than 1, indicating that sensible heat flux was the main source to heat the atmosphere over the site.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.30.2-30.2
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• 2010

It is a mistaken impression that the midlatitude ionosphere was a very stable region with well-known morphology and physical mechanism. However, the large disturbances of midlatitude ionospheric contents in response to global thermospheric changes during geomagnetic storms are reported in recent studies using global GPS TEC map and space-born thermospheric UV images, and its importance get higher with the increasing application areas of space navigation systems and radio communication which are mostly used in the midlatitudes. Positive and negative storm phases are used to describe increase and decrease of ionospheric electron density. Negative storms result generally from the enhanced loss rate of electron density according to the neutral composition changes which are initiated by Joule heating in high-latitudes during geomagnetic storms. In contrast, positive ionospheric storms have not been well understood because of rare measurements to explain the mechanisms. The large enhancements of ground-based GPS TEC in Korea were observed on 8 and 10 November 2004. The positive ionospheric storm was continued except for dawn on 8 November, and its maximum value is ~65 TECU of ~3 times compared with the monthly mean TEC values. The other positive phase on 10 November begin to occur in day sector and lasted for more than 6 hours. The O/N2 ratios from GUVI/TIMED satellite show ~1.2 in northern hemisphere and ~0.3 in southern hemisphere of the northeast Asian sector on 8 and 10 November. We suggest the asymmetric features of O/N2 ratios in the Northeast Asian sector may play an important role in the measured GPS TEC enhancements in Korea because global thermospheric wind circulation can globally change the chemical composition during geomagnetic storms.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.23.4-23.4
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• 2008

In March and April 2001, the apogee (~9 Re) of the Polar spacecraft was located near the subsolar magnetopause with its orbital plane nearly parallel to a magnetic meridian plane. Polar electric and magnetic field data acquired during the two-month interval of solar maximum have been used to study fundamental standing Alfven waves near the subsolar meridian plane (magnetic local time = 1000-1400 hours) at magnetic latitudes from the equator to $\pm45$ degrees and at L values between 7 and 12. In the frequency band from 1.5 to 10 mHz, fundamental mode oscillations were identified based on high coherence (more than 0.7) and an approximately 90-degree phase shift between the azimuthal magnetic and radial electric field components. The L dependence of the fundamental frequencies is studied, and the frequencies are compared with those observed near the solar minimum interval (Takahashi et al. 2001). We found that the average frequencies in solar maximum are lower than those in solar minimum by a factor of ~2. This implies that the mass density in solar maximum is higher than that in solar minimum by a factor of ~4. Since there is a positive correlation between solar irradiance and solar activity, we suggest that the ionosphere in solar maximum produces more ions and load magnetic flux tubes with more ions.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권10호
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• pp.553-558
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• 2000

This paper deals with change of contact angle, surface potential decay, surface resistivity and XPS of water-treated epoxy insulator. From the experimental results on the contact angle was reduced from $74^{\circ}$to $24^{\circ}$ due to the formation of polar hydroxyl groups on surface which was associated with intermolecular reaction between epoxy chains of three-dimensional network structure and water molecules. From the experimental results in the surface potential decay of water treated-samples, it was found that the accumulation of charge is decreased and the surface potential decay time is shortened by the interaction of polar hydroxyl groups induced on the treated surface as the increment of treatment time. The positive charging on the treated surface compared with negative charging is relatively lowered by the induction of polar hydroxyl groups. The surface resistivity was changed from $10^{15}[{\Omega}/cm^2$] to $10^{12}[{\Omega}/cm^2$] caused by water treatment. From XPS, it was found that the changes affected by the surface degradation of epoxy were caused by the generation of carboxyl groups through the chain decomposition and recombination with oxygen molecules in the air.

• Bulletin of the Korean Chemical Society
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• 제23권9호
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• pp.1309-1338
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• 2002

The fluorescence and photoisomerization quantum yields of trans-1-(9-anthryl)-2-(4-pyridyl)ethene (t-4-APyE), 1-(10-methyl-9-anthryl)-2-(4-pyridyl)ethene (t-4-MeAPyE), and 1-(10-chloro-9-anthryl)-2-(4- pyridyl)ethene (t-4-ClAPyE) were measured in cyclohexane, acetonitrile, and methanol at room temperature.Polar solvents result in the drastic reduction of fluorescence quantum yield and increase of photoisomerization quantum yield for all three compounds. These results are probably due to the stabilization of intramolecular charge transfer (ICT) excited state in polar solvent. The higher contribution of ICT in the presence of more electron-donating methyl substituent, manifested by largest positive fluorescence solvatochromism, indicates that the pyridine ring acts as an electron acceptor. Protonation or methylation makes pyridine ring stronger electron acceptor and causes long-wavelength ground state charge transfer absorption band and complete quenching of fluorescence. The fluorescence from t-4-APyE derivatives can be switched off responding external stimuli viz. medium polarity, protonation, or methylation.

• The Korean Journal of Ecology
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• 제11권3호
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• pp.131-136
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• 1988

The continuum analyses and polar ordinations were applied for the ordination of forest vegetation in Mt. Naejang, national park in Korea. In the continuum analyses the sequence of Pinus densiflora, Quercus mongolica, Quercus variabilis, Carpinus laxiflora, Carpinus tschonoskii, Lindera erythrocapa and Zelkova serrata community was arranged along the continuum gradient as in moisture gradient analyses. The positive correlation of r=0.83 between continuum index and soil moisture content was observed. In the polar ordinations ten communities of Pinus densiflora, Quercus monogolica, Quercus variabilis, Carpinus laxiflora, Daphniphyllum macropodum, carpinus tschonoskii, Quercus aliena-Carpinus tschonoskii, Torreya nucifera, Cornus controversa-Lindera erythrocarpa and Zelkova serrata were identified. However, continuous distribution pattern of ten communities mentioned above could be regarded as a vegetational continuum. The results of these ordinations also were corresponded to those of phytosociological classification.

• 천문학회보
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• 제37권2호
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• pp.116.1-116.1
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• 2012

When an interplanetary (IP) shock passes over the Earth's magnetosphere, the geosynchronous magnetic field strength near the noon is always enhanced, while the geosynchronous magnetic field near the midnight decreases or increases. In order to understand what determines the positive or negative magnetic field response at nightside geosynchronous orbit to sudden increases in the solar wind dynamic pressure, we have examined 120 IP shock-associated sudden commencements (SC) using magnetic field data from the GOES spacecraft near the midnight (MLT = 2200~0200) and found the following magnetic field perturbation characteristics. (1) There is a strong seasonal dependence of geosynchronous magnetic field perturbations during the passage of IP shocks. That is, the SC-associated geosynchronous magnetic field near the midnight increases (a positive response) in summer and decreases (a negative response) in winter. (2) These field perturbations are dominated by the radial magnetic field component rather than the north-south magnetic field component at nightside geosynchronous orbit. (3) The magnetic elevation angles corresponding to positive and negative responses decrease and increase, respectively. These field perturbation properties can be explained by the location of the cross-tail current enhancement during SC interval with respect to geosynchronous spacecraft position.

• 분석과학
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• 제25권6호
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• pp.350-363
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• 2012

이온크로마토그래피(IC) 시스템을 이용하여 눈 시료의 이온성분을 측정하기 위해 IC 시스템의 성능평가, 시료 병의 세척법, 필터 적용에 따른 문제점을 조사하였다. 이를 바탕으로 이온성분 측정자료의 불확도 산출법을 연구하였다. 본 연구의 IC 시스템 검출한계는 양이온의 경우 0.01~0.26 ${\mu}g/L$, 음이온 성분들은 0.02~0.26 ${\mu}g/L$로 나타났다. 그리고 양이온과 음이온의 재현성을 나타내는 변동계수는 각각 0.4-17.4%, 0.1-27.6%로 조사되었다. BCR$^{(R)}$-408을 이용한 측정자료의 정확도 조사 결과 양이온과 음이온의 상대오차는 각각 4.5-12.0%, 1.3-5.6%로 나타났다. 시료 병에 대한 실험실 바탕시험 결과 유기음이온을 포함한 일부 성분들($CH_3CO_2{^-}$, $HCO_2{^-}$, $NH_4{^+}$)의 경우 다른 성분들에 비해 오염 가능성이 높은 것으로 조사되었다. $NO_3{^-}$ 성분의 바탕시험 결과는 시료 병 세척과정에 사용된 $HNO_3$의 잔류에 따른 오염영향으로 나타났다. 그리고 눈 시료 용융액의 불용성 입자를 제거하기 위해 필터를 사용할 경우 일부 이온 성분들은 필터로부터 직접 용출되는 것으로 조사되었다. 따라서 사용 전에 증류수(~ 6 mL)로 세척하는 것이 필요하고 지역별로 눈 시료의 농도 특성을 고려하여 선별적으로 필터를 적용해야 한다. 마지막으로 그린란드 북서부 내륙의 NEEM 캠프의 풍상 지역에서 채취한 눈 시료의 이온성분 측정 자료의 불확도를 산출하기 위해 이온 성분 가운데 $F^-$ 측정 자료에 대해 불확도를 결정하였다.