• 한국융합학회논문지
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• 제10권5호
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• pp.51-61
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• 2019

본 연구는 사회경제적 상태의 지표인 교육수준 및 소득수준과 수은, 납, 카드뮴의 혈중 중금속 농도간의 관련성을 살펴보고자 하였다. 국민건강영양조사 2013-2015년 자료를 이용하여 성별에 따른 사회경제적상태와 혈중 중금속 농도간의 관련성을 분석하기 위해 로지스틱회귀분석을 실시하였다. 분석결과 한국성인의 교육과 소득수준이 높을수록 혈중 수은의 농도는 증가하는 경향이 나타났고, 혈중 납과 카드뮴의 농도는 감소하는 경향을 보였다 (P for trend <0.001). 혈중 중금속 농도의 유병률이 증가하고 있는 시점에서 사회경제적수준에 따른 건강불평등을 해결하기 위한 국가차원의 공중보건학적 정책이 필요할 것으로 사료된다.

• Journal of Ecology and Environment
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• 제44권4호
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• pp.212-221
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• 2020

Background: Rapid industrialization has caused various impacts on nature, including heavy metal pollution. However, the impacts of industrialization vary depending on the types of industrializing activity and surrounding environment. South Korea is a proper region because the rapid socio-economical changes have been occurred since the late nineteenth century. Therefore, in this study, we estimate the anthropogenic impacts on an ecosystem from a sediment core of Yonghwasil-mot, an irrigation reservoir on the western coast of Korea, in terms of heavy metal concentrations, nutrient influx, and pollen composition. Results: The sediment accumulation rate (SAR) determined by 210Pb geochronology showed two abrupt peaks in the 1930s and 1950s, presumably because of smelting activity and the Korean War, respectively. The following gradual increase in SAR may reflect the urbanization of recent decades. The average concentrations of arsenic (As), copper (Cu), and lead (Pb) during the twentieth century were > 48% compared to those before the nineteenth century, supporting the influence of smelting activity. However, at the beginning of the twenty-first century, the As, Cu, and Pb concentrations decreased by 19% compared to levels in the twentieth century, which is coincident with the closure of the smelter in 1989 and government policy banning leaded gasoline since 1993. The pollen assemblage and nutrient input records exhibit changes in vegetation cover and water level of the reservoir corresponding to anthropogenic deforestation and reforestation, as well as to land-use alteration. Conclusions: Our results show that the rapid socio-economic development since the twentieth century clearly affected the vegetation cover, land use, and metal pollutions.

• 전기전자학회논문지
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• 제27권3호
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• pp.288-295
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• 2023

본 연구에서는 radio frequency (RF)-스퍼터링을 이용하여 SiC 기판 위에 Ga₂O₃ 박막을 증착하여 Metal-Semiconductor-Metal (MSM) UV photodetector (PD)를 제작하였고, 산소 후열처리에 따른 PD 성능을 연구하였다. 산소 후열처리된 Ga₂O₃ 박막은 외부 광에 대한 전류의 상당한 증가와 시간 의존성 on/off 광 응답 특성에서 측정된 감소시간이 1.21, 1.12 s로 후열처리를 하지 않은 박막의 감소시간인 1.34, 3.01 s 보다 더 빠른 반응을 보여주었다. 이러한 특성은 산소 후열처리 후의 산소 공공 및 결함 분포 변화에 기인한다. 우리의 연구 결과는 산소 후열처리가 PD 성능 향상에 영향을 미칠 수 있다는 것을 확인하였다.

• 동력기계공학회지
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• 제9권4호
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• pp.130-136
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• 2005

The effects of additional Mg content, the size and volume fraction of reinforcement phase on the mechanical properties of ceramic particle reinforced aluminium matrix composites fabricated by pressureless metal infiltration process were investigated. The hardness of $SiC_p/AC8A$ composites increased gradually with an increase in the additive Mg content, while the bending strength of $SiC_p/AC8A$ composites increased with an increase in additive Mg content up to 5%. However, this decreased when the level of additive Mg content was greater than 5% due to the formation of coarse precipitates by excessive Mg reaction and an increase in the porosity level. The hardness and strength of the composites increased with decreasing the size of SiC particle. It was found that the composites with smaller particles enhanced the interfacial bonding than those with bigger particles from fractography of the composites. The hardness of $Al_2O_{3p}/AC8A$ composites increased gradually with an increase in the volume fraction, however, the bending strength of $Al_2O_{3p}/AC8A$ composites decreased when the volume fraction of alumina particle was greater than 40% owing to the high porosity level.

• Journal of Preventive Medicine and Public Health
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• 제38권4호
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• pp.401-407
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• 2005

Objectives : We wanted to investigate the relationship between heavy metal, especially lead and mercury, to the blood pressure and cholesterol level in children. Methods : This study was undertaken in three primary schools and the study subjects were a total of 274 children. The lead in the blood and the urine mercury were analyzed by performing atomic absorption spectroscopy. Results : All of participants' blood lead levels and urine mercury concentrations were below the suggested level of concern according to the criteria of the CDC and ATSDR. We found no significant correlation between lead, mercury and the blood pressure. The blood lead level did not show any relationship with the blood pressure and cholesterol. However, the urine mercury levels were associated with the serum cholesterol. Conclusion : Our study suggests that mercury can induce an increase of cholesterol as a risk factor of myocardial infraction and coronary/cardiovascular disease.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1218-1223
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• 2021

A hydrophobic ionic liquid including an amino moiety ([DiOcAPmim][NTf₂]) was synthesized. Its extraction behaviors towards Pd(II), Ru(III), Rh(III) were investigated in nitric acid aqueous solution as a function of contact time, effect of concentration of nitric acid, effect of temperature, and effect of co-existing metal ions. The extraction kinetics of Pd(II) was fairly fast and extraction equilibrium can be attained within only 5 min under the [HNO₃] = 2.05 M. When [HNO₃]< 1 M, the extraction percentage of Pd(II), Ru(III), Rh(III) were all above 80%. When [HNO₃] reached 2 M, all of the extraction percentage decreased and in an order of Pd(II)>Ru(III)>Rh(III). When [HNO₃]> 2 M, the extraction performance gradually recovered. The effect of temperature can slightly affect the extraction performance of Pd(II). Furthermore, in simulated high-level liquid waste, [DiOcAPmim][NTf₂] showed a better preference towards Pd(II) under the interference of various other co-existing metal ions.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.490-492
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• 2010

Center-tapped termination을 가진 stub series-termination logic (SSTL) 채널을 지원하기 위한 전압모드 송신단을 제안한다. 제안하는 송신단은 진단 모드를 지원하고 신호보전성을 향상시키기 위해 출력레벨 조절수단을 가지며, 가변 병렬 터미네이션을 사용하여 swing level을 조절하는 동안 송신단의 출력 저항을 일정하게 유지시켜준다. 또한 제안하는 송신단의 off-chip 저항은 기생 캐패시터, 인덕터에 의한 termination의 임피던스 부정합을 줄여준다. 제안된 송신단을 검증하기 위해서 $50{\Omega}$의 출력저항을 유지하면서 8-레벨의 출력을 제공하는 전압모드 송신단을 1.5V의 70nm 1-poly 3-metal DRAM공정을 이용하여 구현하였다. 수신단 termination이 존재하지 않는 SSTL 채널에서 제안하는출력레벨 조절이 가능한 송신단을 이용함으로 1.6-Gb/s에서 54%의 jitter 감소가 측정되었다.

• 대한지역사회영양학회지
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• 제3권3호
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• pp.454-465
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• 1998

This study was to investigate the recognition level of food contamination with residual pesticides and hazardous heavy metals from 365 male and female adults in Taejon area using questionnaires. Among the recognizing level of residual pesticides in overall foods, 69.1% were 'serious', 25.6% were 'average' and 5.3% were 'not serious'. Over 94.7% of the subjects recognized residual pesticides pollution infoods. for hazardous heavy metals in food, 47.8% responsed as 'serious', 40.5% as 'average' and 11.8 as ' not serious' . Over 88.3% of the subjects recognized contaminated pesticides seriously in fruits, 72.1% in vegetables and 51.7% in cereals, whereas 55.7% of the subjects recognized hazardous heavy metal contamination seriously in fruits, 53.4% in vegetables, 40.8% in fishes and shellfishes and 35.0% in seaweeds. The subjects recognized residual pesticides contamination more seriously in overall foods, cereal, potatoes and starches, bean, vegetables and fruits, whereas hazardous heavy metal contamination was recognized more seriously in fishes and shellfishes, and seaweeds food groups. Comparisons were shown based on individuial's occupation. Farmer, forester, iner and fisher showed the lowest recognizing level of food contamination in most food groups. The mean score of the dietary effect by mass media's information on food contamination from residual pesticides and hazardous heavy metals were 3.51±0.96 out of 5 points. By Duncan's multiple range test, sex, age, marriage, food cost per month, concerns about health and nutrition knowledge showed significant differences in the mean effect score at p<0.05. According to a pesticides contamination in several food groups were affected by food cost per month, mass media's information on food contamination, health status, and concerns about health, But a recognition level of hazardous heavy metals in food were affected by income and, food cost per month mass media's information on food contamination, health status, concern about health and nutrition knowledge. People who need to take extreme precautions of food contamination were in order of producers, government officials, homemakers, the consumer's association and consumers.

• Journal of Welding and Joining
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• 제13권1호
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• pp.115-126
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• 1995

Vision sensors using the optical triangulation have been widely used for automatic welding systems in various ways, but their reliability is seriously affected by presence of the arc noise. The reliability of vision sensors was analyzed with variation of the arc noise by considering the reflectance of the base metal. first, the properties of the base metal's reflection were modelled by using the Bidirectional Reflectance-Distribution Function(BRDF), and then the variation of the reflected arc intensity was formulated for various configurations of the torch, base metal, and sensor. The experimental data of the gray level of the reflected arc light were obtained for two materials, mild steel and stainless steel. It was found that the results calculated from the proposed model were in good agreement with the experimental data.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.139-142
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• 2000

The SiCp/AC8A composites were fabricated by the pressureless metal infiltration process successfully. The effect of additional Mg, which were mixed with SiC particles to promote interfacial wetting between the reinforcement and matrix alloy, and particle size on the mechanical properties was investigated. By increasing the additional Mg content the hardness of SiCp/AC8A composites was increased due to the hard reaction products, but the bending strength was decreased by the excess reaction of Mg and high porosity level when the additional Mg content is over 7%. The Hardness and bending strength was increased by decreasing the size of SiC particle.