• The Korean Journal of Nuclear Medicine
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• v.32 no.4
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• pp.365-373
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• 1998

Purpose: The conventional gamma camera is not ideal for scintimammography because of its large detector size (${\sim}500mm$ in width) causing high cost and low image quality. We are developing a small gamma camera dedicated for breast imaging. Materials and Methods: The small gamma camera system consists of a NaI (T1) crystal ($60 mm{\times}60 mm{\times}6 mm$) coupled with a Hamamatsu R3941 Position Sensitive Photomultiplier Tube (PSPMT), a resister chain circuit, preamplifiers, nuclear instrument modules, an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a standard resistive charge division which multiplexes the 34 cross wire anode channels into 4 signals ($X^+,\;X^-,\;Y^+,\;Y^-$). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated ana digitized via triggering signal and used to localize the position of an event by applying the Anger logic. Results: The intrinsic sensitivity of the system was approximately 8,000 counts/sec/${\mu}Ci$. High quality flood and hole mask images were obtained. Breast phantom containing $2{\sim}7 mm$ diameter spheres was successfully imaged with a parallel hole collimator The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We have succesfully developed a small gamma camera using NaI(T1)-PSPMT and nuclear Instrument modules. The small gamma camera developed in this study might improve the diagnostic accuracy of scintimammography by optimally imaging the breast.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.105-117
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• 2001

The characteristics of hydrogeochemistry and fluorine distribution in drinking groundwater from limestone and granite were studied in the Keumsan-Wanju area, where major important fluorite-deposits are distributed. The hydrochemical properties of groundwater from studied area arc commonly characterized as $Ca-HC0_3$ water type. However, some of the groundwater samples collected from Jurassic and Cretaceuus granites belong to $Ca-Na-HC0_3 and Na-HC0_3$ type, respectively. The contamination of drinking groundwater by minewater from the nearby fluorite deposits is not found yet. However, groundwater having high F contents up to 1].4 mgll, which is higher than the drinking water limit, is found from the wells located in Cretaceous granite. The tluorine contents in groundwater generally increase with increasing well depth. The concentrations of F in the groundwater show a positive relationship with the values of Na, $HC0_3, Cl. Si0_2$, pH, whereas a negative relationship with Ca. The positive correlation of F-concentrations to major elements ($Si0_2$, Na, CI) and trace elements (Li, B, Rb) may suggest that the groundwater come from the decomposition of tluoride-bearing silicate minerals within highly differentiated granitic rocks, Therefore, wells for drinking water should not be developed or should be drilled within shallow level in the Cretaceous granite region to reduce the F contents in the groundwater.

• Microbiology and Biotechnology Letters
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• v.8 no.4
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• pp.229-235
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• 1980

Pectin transeliminase (PTE) was produced by Saccharomyces cerevisiae, Schizosaccharomyces pombe 4683, and Aspergillus niger in the media containing 2% pectin and examined for its characteristics. The Production of the enzyme was higher by Asp. niger than by the two yeast strains, showing that the PTE activity was proportional to reducing power. The enzyme was proved to reduce pectin and produce 4, 5- unsaturated galacturonic acid. The optimum activity of the PTE was found to be at pH 6.0 and $50^{\circ}C$. The activities of these enzyme were stable below $50^{\circ}C$ but decreased at the higher temperature. Substrate inhibition of the PTE activities was appeared at high concentrations of pectin. Those PTE activities were increased under 0.6M of KCI and NaCI, but that maximal activities at the concentration of 0.2M MgC $l_2$.

• Journal of Soil and Groundwater Environment
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• v.16 no.6
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• pp.133-142
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• 2011

A total of 247 samples were collected from groundwater being used for drinking-water supply, and hydrogeochemistry and radionuclide analysis were performed. In-situ analysis of groundwaters resulted in ranges of $13.7{\sim}25.1^{\circ}C$ for temperature, 5.9~8.5 for pH, 33~591 mV for Eh, $66{\sim}820{\mu}S/cm$ for EC, and 0.2~9.4 mg/L for DO. Major cation and anion concentrations of groundwaters were in ranges of 0.5~227.6 for Na, 1.0~279.3 for Ca, 0.0~9.3 for K, 0.1~100.1 for Mg, 0.0~3.3 for F, 0.9~779.1 for Cl, 0.3~120.4 for $SO_4$, 0.0~27.4 for $NO_3$-N, and 6~372 mg/L for $HCO_3$. Uranium-238 and radon-222 concentrations were detected in ranges of N.D-$131.1{\mu}g/L$ and 18-15,953 pCi/L, respectively. In case of some groundwaters exceeding USEPA MCL level ($30{\mu}g/L$) for uranium concentration, their pH ranged from 6.8 to 8.0 and Eh showed a relatively low value(86~199 mV) compared to other areas. Most groundwaters belonged to Ca-(Na)-$HCO_3$ type, and groundwaters of metamorphic rock exhibited the highest concentration of Na, Mg, Ca, Cl, $NO_3$-N, U, and those of plutonic rock showed the highest concentration of $HCO_3$, and Rn. Uranium and fluoride from granite areas did not show any correlation. However, uranium and bicarbonate displayed a positive relation of some areas in plutonic rocks($R^2$=0.3896).

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.11a
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• pp.121-125
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• 2005

우리나라 영아 사망은 계속 감소를 보이고 있으나 상대적으로 낮은 출산율이 최근 문제시되고 있다. 영아 사망률은 인구의 사회적 건강의 요인으로서 넓게 인식된다. 따라서 영아 사망률의 사인을 밝히는 것은 낮은 출생률에 대비하고 출생아가 건강한 성인으로 자라날 수 있는 토대를 마련하기 위해서 중요한 연구가 될 것이다. 이에 본 연구에서는 국내에서는 처음으로 Record linkage를 통해 2000년부터 2003년 까지의 출생 자료와 사망 자료를 통합하여 유아 사망에 영향을 미치는 요인을 분석하였다. 다중 로지스틱 회귀분석을 통해 관련 변수들을 보정한 상태에서 조산아의 유아 사망 위험비는 1.42(95%CI =1.25-1.63)로 나타났다. 그 외에 산모의 연령, 부모의 직업, 거주지역 등이 유의한 위험요인으로 나타났고 본 연구에서 저체중은 영아 사망의 위험 요인으로 나타나지 않았다.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.111-117
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• 1995

The alkali-aggregate reaction is a reaction between the alkali metals in the pore water of a concrete and an unstable mineral of the aggregate. There are three types of alkali-aggregate reation which causes deterioration of concrete, such as alkali-silicate reation, alkali-carbonate reaction and alkali-silica reation. Deterioration due to alkali-silica reation is more comon than that due to either the alkali-silicate or alkali-carbonate reaction. The alkali-silica reation is a reaction between the hydroxyl ions in the pore water of a concrete and silica which exists in signigicant quantities in the aggregate. In this PAPER, Alkali-aggregate reactions of mortar made with various abroad aggregate were investigated using XRD, microscope, chemical and physical tests. In additions, the effects of the texture of aggregate, Na, K, CI ion concentrations added to the mortar, on these reactions were studied.

• Journal of Environmental Science International
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• v.18 no.6
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• pp.595-601
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• 2009

The effects of the cation-to-anion resin ratio and bed depth on ion exchange performance of mixed-bed were studied at ultralow solution concentration. Breakthrough curves were experimentally obtained for NaCI solution as functions of resin ratio and bed depth. The bed depth affects the pattern of the sodium breakthrough curve but not the chloride breakthrough curve in beds because of the selectivity difference. Resin selectivity determines the shape of breakthrough curves, Some sodium and chloride breakthrough curves crossed at a point as a function of resin ratio. The lower cation-to-anion resin ratio showed the higher effluent concentration or treated volume of the crossover point regardless of the total resin weight.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.526-531
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• 1996

국내의 방사성 동위원소 (Radioisotope; RI) 사용기관에서 발생, 수거되어 현재 원자력연구소 저장고 내에 보관중인 폐기물중 가연분을 대상으로 소각실증실험을 수행하였다. 폐기물 발생일을 기준하여 최소 2년이상이 경과한 RI 폐기물을 소각한 결과 폐기물의 부피와 무게를 각각 약 1/250, 1/30로 줄일 수 있었으며, 소각운전중 배출기체의 농도는 환경관련법상의 배출허용기준치 이하, 배출방사선량은 검출기의 측정한계 이하였다. 방사성동위원소 추적자로 I-131 ($Na^{131}$ I형태, 총 2mCi)을 사용한 모의 폐기물을 소각한 결과 대부분의 방사능은 소각재에 잔존하기 보다는 휘발되어 배기체와 함께 거동하며 주로 포대여과기의 여과층에서 잡히는 것으로 나타났다.

• Corrosion Science and Technology
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• v.2 no.1
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• pp.30-35
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• 2003

In this study, sand cast AZ91E and zirconium grain refined MEZ are representative of two typical groups of magnesium alloys: those containing aluminium and those containing no aluminium but with zirconium as a grain refiner. The corrosion performance of these two alloys was evaluated and compared in 5%wt NaCI solution through measurements of weight loss and polarisation curves and examination of microstructure. Corrosion damage of AZ91E was deeper and more localised than that of MEZ, while MEZ had a lower rate of cathodic hydrogen evolution and a higher rate of anodic dissolution than AZ91E. These differences in behaviour can be related to the differences in microstructure and chemical composition between the two alloys.

• Journal of the Korean Ceramic Society
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• v.22 no.3
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• pp.19-24
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• 1985

The phtoelectrochemical porperties of $Nb_2O_5$, $Sb_2O_3$ and $V_2O_5$ doped and pure $SrTiO_3$ ceramic electodes were investigated. Shapes of I-V and I-λ characteristics of the pure $SrTiO_3$ ceramic electrode are similar to those of SrTiO3 single crystal electorde ; the anodic current strats at -0.9V (vs. Ag/AgCI) in 1 N-NaOH aqueous solution and the photoresponse appears at a wavelength of about 390nm and the quantum efficiency is about 3.5% at wavelength of 390nm under 0.5V vs. Ag/AgCl. Photocurrents of $Nb_2O_5$, $Sb_2O_3$ and $V_2O_5$ doped electrodes and $V_2O_5$ doped ceramic electrode appears at wavelength of 390nm and 500nm respectively.