• Nuclear Engineering and Technology
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• 제50권3호
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• pp.462-469
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• 2018

The background spectrum of a $3^{{\prime}{\prime}}{\times}3^{{\prime}{\prime}}$ NaI(Tl) well-type scintillation SILENA detector was measured without shielding, in 6 cm thick lead shielding, and with 2 mm thick electrolytic copper covering the detector inside the lead shielding. The relative remaining background of the lead shield lined with copper was found to be ideal for low-level environmental radioactive spectroscopy. The background total count rate in the (20-2160 KeV) was reduced 28.7 times by the lead and 29 times by the Cu + Pb shielding. The effective reduction of background (1.04) by the copper mainly appeared in the energy range from X-ray up to 500 KeV, while for the total energy range the ratio is 1.01 relative to the lead only. In addition, a strong relation between the full-energy peak absolute efficiency and the detector well height was found using gamma-ray isotropic radiation point sources placed inside the detector well. The full-energy peak efficiency at a midpoint of the well (at 2.5 cm) is three times greater than that on the detector surface. The energy calibrations and the resolution of any single energy line are independent of the locations of the gamma source inside or outside of the well.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2003년도 추계학술대회 및 정기총회
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• pp.342-345
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• 2003

Due to the rapid development of manufacturing and information technology, traditional supply chain scheme has been changed dramatically Most companies have been forced to relocate or redesign their logistics network in different countries. A supply chain partnership is a relationship formed between two independent members in supply chain through information sharing to achieve specific objectives and benefits in terms of reductions in total costs and inventories. This study illustrates the benefits of supply chain partnerships based on information sharing and lead-time patterns. We consider three level of information sharing: (1) immediate order information; (2) demand information; (3) inventory information. Given a fixed total lead-time, how lead-time distribution will affect the bullwhip effect and inventory cost under information sharing strategies. The results can help improving supply chain performance and selecting suitable direction for the re-configuration of supply chain network.

• 한국정보시스템학회지:정보시스템연구
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• 제10권2호
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• pp.129-150
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• 2001

In this study, we model a decentralized supply chain system which is managed by four types of centers, sequentially located: Retailer, Wholesaler, Distributor, and Factory Each center contributes to enhancing the performance of the supply chain system individually with its own local inventory information. Through experiments which are performed with a programmed simulation (like the MIT beer game), we investigate how the information lead time improvement in each center affects the whole system. And we show that the impact of the lead time improvement in the downstream, like retailers, affects more to the system than the one in the upstream, like factories, in a cost-effective way. Moreover, by using information lead time for each center, we analyze how much the extent of the improvement affects the whole system, especially for the total cost and the order level.

• 한국경영과학회지
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• 제17권2호
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• pp.91-106
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• 1992

It an inventory control system, the demand over time are often assumed to be independently identically distributed (i. i. d.). However, the demands may well be correlated over time in many situations. The estimation of reorder points is not simple for correlated demands with variable lead time. In this paper, a general class of autoregressive and moving average processes is considered for modeling the demands of an inventory item. The first four moments of the lead-time demand (L) are derived and used to approximate the distribution of L. The reorder points at given service level are then estimated by the three approximation methods : normal approximation, Charlier series and Pearson system. Numerical investigation shows that the Pearson system and the Charlier series performs extremely well for various situations whereas the normal approximation show consistent underestimation and sensitive to the distribution of lead time. The same conclusion can be reached when the parameters are estimated from the sample based on the simulation study.

• 자원환경지질
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• 제27권1호
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• pp.93-100
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• 1994

이 연구는 위스컨신주 도어지역의 지하수계에서의 남성분의 이동과 불규칙한 검출에 대한 메카니즘을 규명하였다. 1991년 봄 충진기간 동안에, 세개씩의 수위정(piezometers)을 내장한 두곳의 관측정과 다섯군데의 가정우물에서 수위와 수질의 변화를 측정하였다. 충진현상에 대한 수위의 변화는 지하수의 충진이 약 4일에서 10일 정도 연체되면서 비교적 빠르게 일어남을 보여주며, 이것은 지하수의 충진이 실루리안 돌로마이트 대수층 내에서 높은 수리전도율(K)을 가진 지대를 통해서 일어나고 있음을 지시해준다. 지하수내의 납성분은 미립자에서만 발견되었고, 용융된 상태로는 검출되지 않았다. 그 농도는 0.2에서 $7.1{\mu}g/mg$인데, 이는 지하수내 총 납성분으로는 0.3에서 $4.7{\mu}g/l$이다. 충진사건부터 최대의 미립자가 가정우물까지 이동하는데 걸리는 연체시간은 약 19일에서 22일 이었다. 지하수내에서 납성분이 미립자와 더불어 있으므로, 가정우물 중에서도 높은 수리전도대와 연결된 우물에서만 납성분이 검출되고, 결과적으로 지역적 불규칙성을 유발한다. 또한 우물에서는, 충진사건에 의한 지하수계로의 미립자의 유입량의 변화, 미립자의 이동에 따른 연체현상, 그리고 이동중의 분산 등으로 인해서 납성분의 농도가 채취하는 시간에 따라서 다르게 나타난다.

• Journal of Nutrition and Health
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• 제44권6호
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• pp.518-526
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• 2011

To determine blood heavy metal concentrations by seafood consumption in Korean adults, blood cadmium, mercury, and lead concentrations in a representative sample of 1,709 Koreans participated in the Fourth Korea National Health and Nutrition Examination Survey (KHANES IV-2) in 2008 were analyzed by age and seafood consumption frequency. The mean blood cadmium, mercury, and lead concentrations were $1.14{\pm}0.73{\mu}g/L$, $5.50{\pm}3.83{\mu}g/L$, and $2.56{\pm}1.22{\mu}g/dL$, respectively. The subjects aged ${\geq}$ 50 years had significantly higher blood cadmium concentrations than the subjects aged 20~39 years. Blood mercury concentrations of the 50's were significantly higher than those of the 20's and 30's (p < 0.05). Approximately, 43% of males and 22% of females had blood mercury concentrations > $5.8{\mu}g/L$ which is a blood mercury level equivalent to the current Reference Dose. Only 2 subjects had lead concentrations > $10{\mu}g/dL$, the standard lead level by the Centers for Disease Control and Prevention, USA. The subjects consuming pollack, mackerel, anchovy, corvina, shellfish, and salted seafood at least once a week had significantly higher mercury concentrations than the subjects consuming those seafoods less than once a month. However, there were no clear relationships between blood cadmium and lead concentrations and seafood consumption frequencies.

• Applied Microscopy
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• 제36권2호
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• pp.57-72
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• 2006

본 연구는 급성 납 독성에 대한 활성탄의 방어효과를 알아보기 위하여 시도되었다. 30g 내외의 생쥐를 대상으로 대조군, 납(60mg/kg)투여군, 납 투여후 활성탄(40mg/kg)투여군으로 구분하여 구강투여 한 후 신장 손상억제 효과를 알아보기 위하여 생화학적 및 조직학적 실험을 실시하였다. 혈액 중 blood urea nitrogen(BUN) 그리고 creatinine (Cre)의 활성도는 활성탄 투여군이 납 투여군보다 감소되었다. 전자현미경적 관찰 결과, 신장의 근위세뇨관에서 납 투여군은 미세융모의 소실이 나타나고, 핵이 함입되어 불규칙해졌으며, 미토콘드리아는 팽대되고, 그 수가 감소하였다. rER의 수조가 확장되고 공포화 현상이 관찰되었으며 리보솜의 탈락이 관찰되었다. 활성탄 투여군은 핵은 거의 원형의 상태이고, 다수의 미토콘드리아가 관찰되었으며, rER은 리보솜이 부착된 상태로 관찰되었다. 이상과 같은 결과, 활성탄이 납 중독된 생쥐에서 납을 흡착시킴으로서 손상된 신장에 보호 효과가 있는 것으로 사료된다.

• Clinical and Experimental Reproductive Medicine
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• 제47권3호
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• pp.161-167
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• 2020

Objective: Oxidative stress has been suggested as a possible mechanism for the adverse effects of heavy metal toxicity on male reproduction. Cichorium intybus L. is used in Iranian folk medicine as a hepatoprotective agent as well as for its supposed fertility-enhancing properties. The present study was performed to investigate whether the ethanolic extract of C. intybus leaves could protect male rats against lead-induced testicular oxidative stress. Methods: In this experimental study, adult Wistar rats were treated with 0.1% lead acetate in drinking water alone or with 50, 100, or 200 mg/kg body weight of C. intybus extract via gavage once daily for 70 days. The weight of their reproductive organs, levels of serum hormones, histometric parameters of the seminiferous tubules, epidydimal sperm quality, and oxidative stress status were evaluated. Results: The testis weight, seminiferous tubule diameter, epididymal sperm count, serum testosterone level, and testicular levels of superoxide dismutase and glutathione peroxidase were significantly reduced (p< 0.05) in the lead-treated rats. Moreover, significantly (p< 0.05) higher levels of malondialdehyde were observed in the lead-exposed group compared to the control. However, the co-administration of C. intybus ethanolic extract in lead-treated rats was associated with a significant improvement in reproductive parameters. Conclusion: We conclude that C. intybus leaf extract has the potential to prevent lead-induced testicular toxicity and to suppress the adverse effects of lead on male reproductive health.

• Journal of Preventive Medicine and Public Health
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• 제16권1호
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• pp.19-24
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• 1983

In order to study the effects of iron and zinc on the lead poisoning of rats, lead with iron and zinc, or lead alone were administered orally to a total of 98 adult rats of Sprague-Dawley Species. The concentrations of lead, zinc, and iron were measured by atomic absorption spectrophotometer at every 20 days intervals of 20th, 40th, 60th, 80th and 120th day as a final measurement. Those datas were analysed and compared with those of control groups. The results were summarized as follows; 1. The concentration of lead in blood, bone. and liver tissues kept increasing in case of lead exposure group whereas it started decreasing at 60-80th day when concentration of zinc started increasing in case of combined exposure group. However, in kidney tissue, the concentration of lead in combined exposure group kept increasing up to the end of observation showing special high concentration at the final measurement at 120th day. 2. Concentration of zinc in blood and liver tissues had increased from 60-80th day in case of combined exposure group. 3. Concentration of iron in blood showed decreasing from $44.15{\pm}9.67\;to\;32.44{\pm}2.69{\mu}g/ml$ in case of lead exposure group, whereas it showed constant level of $47.50{\sim}45.65{\mu}g/ml$. However, in liver tissue it kept constant as control did from 40th to 60th days, but from 100th day on it started increasing to show much higher concentration than control.

• 한국치위생학회지
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• 제12권4호
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• pp.695-705
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• 2012

Objectives : The purpose of this study is to evaluate the appearance of having relationship between the exposure to lead and cadmium and the dental caries targeting adults in the Republic of Korea. Methods : The study was designed as a cross-sectional study, using the data of the Fourth Korea National Health and Nutrition Examination Survey. The subjects as 1,966 people, who were confirmed the appearance of dental caries among 1,991 people of having been offered the heavy-metal concentration in blood. Statistical analysis was conducted using SPSS 19.0, according to complex sampling design. Results : As a result of multi-variate analysis on factors of dental caries, in Model I without correction, the gender, age, educational level, appearance of lifelong smoking, daily toothbrushing frequency, appearance of using dental floss, and subjective oral health status were recognized as important factors. In Model II with correction of gender and age, the educational level, daily toothbrushing frequency, and subjective oral health status were recognized as statistically significant factors. In Model III with correction of all factors, the gender, age, educational level, appearance of using dental floss, and subjective oral health status were functioning as statistically significant factors. As a result of statistically analyzing relationship between the exposure to lead and cadmium and the dental caries targeting adults, it was analyzed that there is no significant correlation. However, in case of lead, the tendency of being grown the cross ratio of dental caries could be examined in model I, which didn't correct disturbance factor, model II, which corrected gender and age, and model III, which corrected all variables of disturbance factor. Conclusions : The exposure to lead and cadmium was indicated to have no relationship with adults' dental caries. However, a continuous research of relationship was considered to be necessary by using Korea National Health and Nutrition Examination Survey, which is surveyed in the future.