• 한국재료학회지
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• 제22권12호
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• pp.717-721
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• 2012

Manganese dioxide ($MnO_2$) is one of the most important cathode materials used in both aqueous and non-aqueous batteries. The $MnO_2$ polymorph that is used for lithium primary batteries is synthesized either by electrolytic (EMD-$MnO_2$) or chemical methods (CMD-$MnO_2$). Commonly, electrolytic manganese dioxide (EMD) is used as a cathode mixture material for dry-cell batteries, such as a alkaline batteries, zinc-carbon batteries, rechargeable alkaline batteries, etc. The characteristics of lithium/manganese-dioxide primary cells fabricated with EMD-$MnO_2$ powders as cathode were compared as a function of the parameters of a manufacturing process. The flexible primary cells were prepared with EMD-$MnO_2$, active carbon, and poly vinylidene fluoride (PVDF) binder (10 wt.%) coated on an Al foil substrate. A cathode sheet with micro-porous showed a higher discharge capacity than a cathode sheet compacted by a press process. As the amount of EMD-$MnO_2$ increased, the electrical conductivity decreased and the electrical capacity increased. The cell subjected to heat-treatment at $200^{\circ}C$ for 1 hr showed a high discharge capacity. The flexible primary cell made using the optimum conditions showed a capacity and an average voltage of 220 mAh/g and 2.8 V, respectively, at $437.5{\mu}A$.

• 대한치과보철학회지
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• 제41권5호
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• pp.551-564
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• 2003

Statement of problem : Magnesium oxide may increase pH of alginate, and supply magnesium ions to the polymerization reaction of alginate. Purpose : This study was designed to evaluate the influence of incorporation of magnesium oxide to alginate composition. Material and Method : Seven kinds of experimental alginates were prepared and used for the experiments. Components with unchanging concentrations were sodium alginate 15%, calcium sulfate 14%, sodium phosphate 2%, and zinc fluoride 3%. Contents of magnesium oxide were varied as 0%, 1%, 2%, 3%, 4%, 5%, 6%. Diatomaceous earth were added to each experimental groups as balance to be 100%. Control group was a MgO 0% group. Working time, setting time, elastic recovery strain in compression, compressive strength and tear resistance were measured were measured. Sample size for each groups were 10. Arithmetic means were used as each groups representative values. Regression test between MgO contents and results, Duncan's multiple range test, and One-way ANOVA test were done between groups at level of 0.05. Results : 1 Magnesium oxide made the working time and setting time as longer(p<0.0001). 2 Magnesium oxide did not alter the elastic recovery(p>0.05). 3. Magnesium oxide contents between 2% and 4% exhibited the lowest strain in compression on alginates(p<0.0001). 4. Magnesium oxide made the compressive strength and the tear resistance stronger(p<0.0001). Conclusion : These results mean that setting time of alginate maybe controlled and that mechanical properties maybe improved by the incorporation of magnesium oxide into alginate, without any reduction of elasticity.

• 대한치과보철학회지
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• 제41권2호
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• pp.243-257
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• 2003

The purpose of this study was to search the influences of the increase of the contents of sodium alginate in the experimental alginates on the some mechanical properties. 3 commercial alginates were selected for the purpose of comparison of the results of experiments. 7 experimental alginates were manufactured with the rise of contents of sodium alginate from 8.8% to 18.3% with the decrease of contents of diatomaceous earth and with the constant contents of calcium sulfate 12.5%. sodium phosphate 2.2%, zinc fluoride 2.0%. Splitable metal mold with 12.5mm diameter and 20.0mm height was filled with mixed alginate to prepare the cylinder shaped specimens. Strain in compression, elastic recovery, compressive strength were tested using the ISO specification number 1563, alginate impression material. Experimental groups were 7, and 10 specimens were used for each test items and each groups. Following results were obtained ; 1. Strain in compression was decreased with the increase of sodium alginate contents (p=0.0077, r2 = 0.6302). 2. Elastic recovery was decreased with the increase of sodium alginate contents but was not significant(p=0.0639, r2=0.7449). 3. Compressive strength was increased with the increase of sodium alginate contents (p<0.0001, r2 = 0.9617). These results mean that the increase of sodium alginate contents make alginate harder but may result the increased permanent deformation.

• 한국환경보건학회지
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• 제45권5호
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• pp.487-496
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• 2019

Objective: The purpose of this study was to create soil contamination maps using QGIS (Quantum Geographic Information System) and suggest selection methods for soil pollution sources for preferential investigation in a soil contamination survey. Method: Data from soil contamination surveys over five years in Gyeonggi-do Province, South Korea (2013-2017) were used for making soil contamination maps and analyzing the density of survey points. By analyzing points exceeding the concern level of soil contamination, soil pollutant sources for priority management were identified and selection methods for preferred survey points were suggested through a study of the model area. Results: A soil contamination survey was conducted at 1,478 points over five years, with the largest number of surveys conducted in industrial complex and factory areas. Soil contamination maps for copper, zinc, nickel, lead, arsenic, fluoride, and total petroleum hydrocarbons were made, and most of the survey points were found to be below concern level 1 for soil contamination. The density of the survey points is similar to that of densely populated areas and factory areas. The analysis results of points exceeding the criteria showed that soil pollutant sources for priority management were areas where ore and scrap metals were used and stored, traffic-related facilities areas, industrial complex and factory areas, and areas associated with waste and recycling. According to the study of the model area, the preferred survey points were traffic-related facilities with 15 years or more since their construction and factories with a score of 10 or more for soil contamination risk. Conclusion: Soil contamination surveys should use GIS for even regional distribution of survey points and for the effective selection of preferred survey points. This study may be used as guidelines to select points for a soil contamination survey.

• 한국수산과학회지
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• 제18권6호
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• pp.538-544
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• 1985

부산시내에 산재하고 있는 약수터 중에서 시민의 이용 빈도가 높은 5개 지점을 선정하여 이들의 수질관리에 필요한 기초자료를 얻고자 1983년 12월에서 1984년 8월 사이에 5회에 걸쳐 총 25개 시료를 취하여 내용물에 대한 변화범위와 평균치를 나타내면 다음과 같다. pH $5.80{\sim}7.25$,6.60, 수온 ; $6.0{\sim}23.0^{\circ}C,\;12.9^{\circ}C$, 총증발잔류물 $33.0{\sim}325mg/l$, 121.2mg/l ; 알카리도 $4.75{\sim}51.6mg/l$, 24.lmg/l ; 경도 $9.47{\sim}85.0mg/l$, 30.3mg/l, 전기전도도 $0.495{\sim}2.750{\times}^2{\mu}{\mho}/cm,\;1.239{\times}10^2{\mu}{\mho}/cm$ ; 탁도$0.54{\sim}7.80$ NTU, 2.04 NTU ; 과망간산칼륨 소비량 $0.51{\sim}8.47mg/l$, 1.96mg/l ; 염화이온 농도 $4.91{\sim}36.0mg/l$, 12.53mg/l ; 불소이온 ND-0.30ppm, 0.08ppm ; 질산성 질소 ND-8.94mg/l, 1.94mg/l ; 아질산성 질소 ND-0.10mg/l, 0.03mg/l ; 암모니아성 질소 ND-0.16mg/l, 0.03mg/l ; 인산성 인 ND-0.09mg/l, 0.03mg/l ; 규산성 규소 $0.42{\sim}22.7mg/l$, 7.96mg/l ; 구리 ND-10.5ppb, 2.46ppb ; 납 ND-22.7ppb, 3.54ppb ; 아연 ND-103ppb, 21.33ppb ; 철분 $20.3{\sim}2,800ppb$, 801.72ppb 였었다. 비소, 시안, 카드뮴, 마그네슘, 수은, 육가크롬, 페놀 등은 검출되지 않았다. 특히, 지점 1은 총증발잔류물 178.1mg/l, 전기전도도 $2.127{\times}10^2{\mu}{\mho}/cm$, 탁도 3.16NTU, 염화이온 16.32mg/l로서 다른 지점들 보다 월등히 높았다. 영양염류중 규산성 규소의 함량은 강우에 크게 영향을 받았다. 또 불소이온농도는 상수도 수질기준치 1ppm 보다 0.08ppm으로 훨씬 낮았으며, 철분의 농도는 801.72ppb로서 2.7배나 초과하였다.

• 청정기술
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• 제18권2호
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• pp.200-208
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• 2012

본 연구는 공단지역 주민들의 환경오염물질에 의한 건강피해를 예방하기 위한 기초연구의 일환으로 수행되었다. 이를 위하여 공단지역 및 대조지역에 대한 토양 중의 환경오염물질과 다환방향족탄화수소화합물(PAHs)의 농도수준 및 분포특성을 조사하였다. 시료채취는 공단지역과 대조지역의 토양을 대상으로 실시하였으며, 토양 중의 중금속, VOCs(휘발성 유기화합물), PAHs 및 PCB(폴리클로리 네이티드비페닐) 등 토양오염물질 농도를 분석하였다. 직접노출군에 속하는 가까운 거리의 송도동, 해도동, 제철동 등은 거리가 먼 장기면에 비하여 비교적 높은 농도를 나타났다. 특히 배출원 주변의 직접노출지역(제철동)이 대조지역(장기면) 보다 오염물질의 농도가 높은 것으로 조사되었다. 토양 중의 중금속 농도는 제1지역 우려기준에 비해 대체로 낮은 것으로 나타났으나, 아연은 전 지역이 제1지역 우려기준(300 mg/kg)의 약 20.8~58.9% 수준으로 비교적 높은 농도를 나타내었다. 불소는 모든 지점에서 기준치 이하로 나타났으나, 직접노출지역인 제철동의 경우 제1지역의 우려기준(400 mg/kg)의 약 74% 수준으로 조사되어, 불소에 대한 모니터링과 배출원 관리가 필요한 것으로 판단된다. 또한, 유기인, PCB, 페놀류와 VOCs인 벤젠, 톨루엔, 에틸벤젠, 자일렌 등은 분석기기의 검출한계 이하로 나타났고, 석유계총탄화수소(TPH)의 경우에는 송도동이 높게 나타났다. 한편, 토양 중 PAHs 화합물의 농도 수준은 18.71~1744.59 ng/g이었으며, 발암가능물질 6종에 대한 PAHcarc의 농도수준은 6.54~695.94 ng/g을 나타내었다. 송도동에서 가장 높은 농도수준을 나타내어, 직접노출지역인 공업단지로부터 근거리 지점에서의 PAHs 농도가 원거리 지점인 간접노출지역보다 비교적 높은 농도를 나타내었다.

• 한국산학기술학회논문지
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• 제21권6호
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• pp.411-416
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• 2020

본 연구는 적외선 광학재료의 중적외선 영역의 굴절률을 파악하기 위해 반사율을 측정하고 굴절률과 반사율의 관계로부터 굴절률을 추정하는 방법을 제안한다. 전반사 거울 4개를 일정한 간격으로 배열하고 적외선 광원으로부터 연속 파장의 평행광이 45°로 입사되도록 광 경로를 구성한다. 광 경로를 따라 4개의 전반사 거울에 반사되어 온 광강도 I_B를 측정한 후, 광 경로의 마지막에 놓이는 거울을 시편으로 교체하고 광강도 I_s를 측정한다. I_B와 I_s, 전반사 거울의 비를 이용하여 재료의 반사율을 계산한다. 계산된 반사율과 Fresnel의 굴절률과 반사율 관계식에 넣고 시행착오법으로 굴절률을 추정한다. 이 방법을 적용하여 사파이어(Al₂O₃), 게르마늄(Ge), 불화마그네슘(MgF₂), 황화아연(ZnS)재료를 대상으로 실험하고 굴절률을 추정하여 참고문헌자료들과의 비교를 통하여 모든 재료에 대해 파장범위 3 - 5㎛에서 최대 차이 2% 이하로 잘 일치하는 결과를 얻을 수 있었으며, 이를 통해 본 굴절률 측정방법의 타당성을 확인할 수 있다. 본 연구에서 제시된 방법은 연속 파장의 적외선 광원을 사용하기 때문에 한 번의 측정으로 여러 파장에 대한 굴절률을 추정 할 수 있는 장점이 있다.

• 한국표면공학회지
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• 제13권3호
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• pp.146-154
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• 1980

The effects of various electrodeposition conditions (deposition temperature and cathode current density) on preferred orientation and microhardness of electrodeposited Ni-Sn and Sn-Zn alloys were studied. At deposition temperatures from 25$^{\circ}$ to 95$^{\circ}C$ and constant cathode current density of 270 and 530 A/$m^2$ Ni-Sn and Sn-Zn were codeposited in chloride-fluoride acid and stannate-cyanide alkaline electrolyte bath respectively. Ni-Sn alloy deposited at temperatures from 25$^{\circ}$ to 35$^{\circ}C$ was composed of single phase of $Ni_3Sn_4$ with 73 wt.% Sn and the one deposited at temperatures from 45$^{\circ}$ to 95$^{\circ}C$ was made of multiphase mixture of NiSn, $Ni_3Sn_2$ and $Ni_3Sn_4$ with nearly equiatomic composition (65.5 wt.% Sn). The random orientation of thermody-namically metastable NiSn phase (hexagonal structure) predominated at deposition temperature range 25$^{\circ}$-45$^{\circ}C$, and the strong (110) preferred orientation was found at 65$^{\circ}$-85$^{\circ}C$ and then disappeared again at 95$^{\circ}C$. The microhardness of Ni-Sn deposits increased with deposition temperature up to 85$^{\circ}C$, and then decreased at constant cathode current density. The preferred orientation and the maximum microhardness were discussed in terms of lattice contractile stress which result from desorption of hydrogen atom absorbed in deposit lattice. The Sn content of Sn-Zn alloy deposits increased with deposition temperature up to 75$^{\circ}C$, and then decreased at constant cathode current density of 530 A/$m^2$. It also decreased with cathode current density up to 530 A/$m^2$, and then increased at constant deposition temperature of 25$^{\circ}C$. Sn-Zn alloy deposits were composed of two-phase mixture of ${beta}$-Sn and Zn. The preferred orientations of ${beta}$-Sn (tetragonal structure) changed with deposition temperature. The microhardness of Sn-Zn deposits decreased with deposition temperature. It also increased with cathode density up to 530 A/$m^2$, and then decreased at constant deposition temperature of 25$^{\circ}C$. The microhardness of Sn-Zn deposits was observed to be determinded more by the Sn content than by the preferred orientation.

• Composites Research
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• 제34권6호
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• pp.357-372
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• 2021

에너지 수확장치는 석유자원의 고갈로 인한 자원난을 해결할 수 있는 대안으로 유망하다고 알려져 있다. 기계적 움직임을 전기 에너지로 전환할 수 있는 압전 소자들의 한계(환경오염 및 낮은 기계적 특성)를 극복하기 위하여, 고분자 기지재 기반 복합재료 압전 에너지 수확장치에 대한 많은 연구들이 수행되었다. 본 논문에서는 사용된 재료 및 공정에 기초하여, 보고된 압전 복합재료의 출력 성능 및 관련된 응용 분야를 검토하였다. 압전 필러는 티탄산 지르콘산 연 및 티탄산바륨 기반의 세라믹 필러뿐만 아니라, 친환경, 생체적합성 및 유연성 측면에서 유리한 산화아연을 검토하였다. 기지재는 폴리비닐리덴플로오라이드 및 공중합체로 구성된 압전 고분자 및 에폭시 및 폴리디메틸실록산 기반의 유연한 고분자로 분류하여 복합재료의 압전 시너지 및 높은 외력 적용에 의한 압전 출력 향상을 논의하였다. 또한, 금속 혹은 탄소 소재 기반 2차 필러의 적용에 의한 복합재료의 전도성 혹은 기계적 특성의 향상이 압전 수확장치의 출력 성능에 미치는 영향을 복합재료의 구조 측면에서 검토하였다. 향상된 성능으로 소형 전자기기, 스마트 센서, 의학 분야 등에 응용 가능한 복합재료 기반 압전 수확장치는 미래의 일상에서 접할 수 있는 무선 전자 장치의 전원으로써 잠재적인 통찰을 제공할 수 있다.

• 한국환경복원기술학회지
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• 제27권3호
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• pp.45-56
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• 2024

Heavy metals emitted from urban development do not decompose in the soil and remain for long periods, continually impacting the environment. Since the mid-1990s, there has been increasing societal concern in South Korea regarding soil contamination, prompting various legislative revisions to reduce pollution. This study utilizes the Environmental Impact Assessment Support System (EIASS) to investigate projects in the metropolitan area that have exceeded the Ministry of Environment's soil contamination concern levels from 1989 to 2022 and to examine improvements in the environmental impact assessment (EIA) process. The results reveal that the average concentrations of nine contaminants-cadmium (Cd), copper (Cu), arsenic (As), mercury (Hg), lead (Pb), hexavalent chromium (Cr6+), zinc (Zn), nickel (Ni), and fluoride (F)-have all increased over the years. Among these, Zn had the highest relative proportion, with 37.5% of the 40 sites exceeding environmental concern levels. Investigation of 19 specific projects at these exceedance sites showed that only 7 had documented analyses of contamination causes and remediation plans, and just one had contracted additional remediation services, though results from these efforts were found to be lacking. Furthermore, since 2019, a significant proportion of these sites were involved in residential developments, likely due to government initiatives in new city development and extensive housing supply plans. This research emphasizes the importance of public disclosure of the processes and outcomes of remediation efforts on historically contaminated soils prior to project development. It discusses improvements to the EIA by reviewing current legislation and international examples. The findings of this study are expected to heighten public awareness about heavy metal contamination and enhance transparency in soil remediation efforts, contributing to sustainable environmental management and development.