• 대한방사선기술학회지:방사선기술과학
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• 제2권1호
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• pp.95-99
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• 1979

When the ${\gamma}-ray$ of average energy 375KeV emitted by Ir-192 is exposed to each film through lead foil with various thickness, the film sensitivity will be different according to the thickness of lead foil and film type. The results on the study, different density and sensitive ratio appeared depending on exposed time and film type, but was made on the following common points. 1. The effect of film sensitivity by the front lead foil showed rapid increase up to the thickness of more or less 0.03mm, and the thicker lead foil was decreased more in the thickness of about $0.05{\sim}0.09mm$. 2. The effect of film sensitivity by the back lead foil was increased up to around of $0.03{\sim}0.08mm$ thickness, the maximum sensitivity was obtained in the thickness of more than $0.03{\sim}0.08mm$ without any change in the above effect. 3. The sensitivity of front lead foil was higher than that of back lead foil in thin lead foil with about 0.127mm thickness, but the sensitivity of back lead foil was higher than that of front lead foil when thickness became thicker.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2001년도 추계학술대회 및 정기총회
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• pp.91-91
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• 2001

Nramp2, also known as DMT1 and DCT1, is a 12-transmembrane domain protein responsible for dietary iron uptake as well as metal ions such as lead, manganese, zinc, copper, nickel, cadmium, and cobalt. High expression of DMT1 increase lead uptake, and DMT1-dependent lead transport was H -dependent and inhibited by iron ions. The molecular mechanism of lead transport in CNS is as yet unknown. although interactions between iron and lead at the level of absorption have been known for some time. The process of lead uptake into astrocytes was not known yet. Nramp2 may mediate transport of heavy metal into astrocytes. We investigated whether Nramp2 mediate transport of lead into astrocytes. And we do whether Nramp2 was expressed highly by deprivation of iron in Astrocytes, and lead uptake into astrocytes was influenced by expression of Nramp2. Immortalized human fetal astrocyte(SV-FHA) cells were cultured in medium containing Dulbecco's modified Eagle's medium and treated with Deferoxamine. Northern blot analysis was done for determining mRNA level of DMT1 and lead uptake assay was done in incubation condition of pH 5.5 and 7.4.

• 동의생리병리학회지
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• 제16권2호
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• pp.373-379
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• 2002

This paper was the design of aerosol generator for inhalation toxicology study of lead and evaluation with real time monitoring, and applied several engineering methodology to classical aerosol generator to cope with it's disadvantages. According to the testing conditions, source temperature 50℃ and inlet-duct band heater temperature 150℃, aerosol generation results for sodium chloride and lead acetate were as followings: CPM(Count Per Minute) for Sodium chloride that used for the testing material in aerosol generation and inhalation system was decreased in the 2nd and the 3rd hour's serial trials, but CVs(coefficient of variation) were maintained within 10%. CPMs for 5 and 2.5 gram of lead acetate that used for aerosol generation and inhalation exposure of lead showed similar results because of the sedimentation of lead acetate on piezoelectric crystal with time. For that reason, heating and mixing of nebulizing solution will be needed to generate lead aerosol with stable profile and maximum generation efficiency. Fluctuations of 10 and 5 gram lead acetate were low but 2.5gram was high. However, CVs for 10, 5, and 2.5gram lead acetate were within 10%. Considering the theoretical efficiencies for sodium chloride and lead acetate, 5gram sodium chloride and 2.5gram lead acetate were appropriate choice. Aerosol generation characteristics for two materials with 1 hour interval were different with respect to the fluctuation of CPM and the decrease to 10gram in it's material. For that reason, sodium chloride can not be used to estimate the aerosol generation and it's related parts for lead acetate. According to the testing conditions, source temperature 20, 50, 70℃, and inlet-duct band heater temperature 20, 50, 100, 150, 200℃, aerosol generation results for sodium chloride and lead acetate were as followings: Excluding inlet-duct band temperature 200℃, maximum CPM for sodium chloride was manifested in source temperature 70℃ with each inlet-duct band temperature conditions. We suggest that this condition was the optimum in the design of aerosol generator, inhalation system, and the testing. Maximum CPMs for 10, 5, and 2.5gram sodium chloride were from source temperature 70℃ and inlet-duct band temperature 20℃. Excluding inlet-duct band temperature 50, 200℃, maximum CPMs for lead acetate were indicated in source temperature 50℃ with each inlet-duct band temperature conditions. We suggest that this condition was the optimum in the design of aerosol generator, inhalation system, and the testing for lead inhalation study. Source and inlet-duct band temperatures for 10, 5, 2.5gram lead acetate were 50 and 100℃, 50 and 100℃, 50 and 150℃, respectively. In conclusion, considering above 2 paragraphs of results for aerosol generation, 5gram efficiencies for sodium chloride, lead acetate were higher than 2.5gram's. If inlet-duct band temperature was same, aerosol generation was increased with increase of source temperature. To get maximum aerosol generation will be the conditions that set the appropriate inlet-duel band temperature for each materials and increase the source temperature.

• 한국경영과학회지
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• 제20권2호
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• pp.23-38
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• 1995

In manfacturing systems, to overcome the inherent complexities and uncertainties, due-dates are usually decided by some simple rules. This study proposes a computational procedure for estimating production lead time for computerized manufacturing systems. Based on the current system status stored in the computers, the procedure estimates production lead time for an incoming order. The result is more accurate than the ones produced by old rules, and yet the procedure is fast in computation speed enough to use in real time. Simulations are used to prove these.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4093-4097
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• 2021

This study presents a new dead-time measurement method using the gamma attenuation law and generalized dead-time models for nuclear gamma-ray detectors. The dead-time of the NaI(Tl) detection system was obtained to validate the new dead-time determination method using very thin lead and polyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 ㎲, and paralyzing dead-time was found to be 8.35 ㎲ using lead absorber for NaI(Tl) scintillator detection system. These dead-time values are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin material was used.

• 한국시뮬레이션학회논문지
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• 제20권2호
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• pp.19-27
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• 2011

본 연구에서는 스무딩된 주문정책이 리드타임, 만족율, 재고비용에 미치는 영향을 연구한다. 이를 위해 스무딩된 order up to 주문정책을 사용하는 하류업체와 make to order 방식을 사용하는 상류업체로 구성된 공급사슬을 사용한다. 스무딩을 하면 리드타임이 예상하는 바와 같이 감소된다. 그러나 스무딩에 의해 하류업체에서의 만족율이 감소하며 재고비용이 증가된다. 한편 상류업체 제조시간의 분산이 평균 제조시간보다 만족율 및 재고비용에 미치는 영향이 더 크므로, 상류업체 제조시간의 변동성을 최소화해야 한다.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2005년도 추계학술대회
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• pp.511-515
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• 2005

기업은 고객이 원하는 시기에 원하는 제품을 구매할 수 있도록 항상 준비가 되어 있어야 한다. 고객의 수요를 만족시키기 위하여 기업은 다양한 수요예측방법을 통하여 적절한 재고 수준과 수요예측을 하고 있다. 제조 기업의 경우에는 다른 산업에 비하여 정확한 수요예측과 낮은 재고 수준의 유지가 비용과 직접적인 연관이 있기 때문에 제조 기업은 경제적인 주문량 결정(Economic Order Quantity: EOQ)이 매우 중요한 문제이다. 주문량을 결정하는 방법에는 여러 가지가 있지만, 본 논문에서는 고객 지연을 방지하기 위하여 경제적 주문량 결정에 고객 지연과 관련된 비용을 포함시키는 것은 물론 고객 지연이라는 상황을 방지하는 노력의 한 방법으로 가격 할인(discount system)을 이용하고자 한다. 가격 할인을 이용하여 고객으로 하여금 빠른 주문을 유도하고 그로 인하여 고객 지연 상황의 발생을 줄여보려고 한다.

• 대한산업공학회지
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• 제2권1호
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• pp.79-83
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• 1976

This paper deals with a computer simulation for the stochastic inventory system in which the decision rules are associated with the problem of forecasting uncertain demand, lead time, and amount of shortages. The model consists of mainly three parts; part I$\cdots$the model calculates the expected demand during lead time through the built-in subrou tine program for random number generator and the probability distribution of the demand, part II$\cdots$the model calculates all the possible expected shortages per lead time period, part III$\cdots$finally the model calculates all the possible total inventory cost over the simulation period. These total inventory costs are compared for searching the optimal inventory cost with the best ordering quantity and reorder point. An application example of the simulation program is given.

• 대한산업공학회지
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• 제31권1호
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• pp.27-35
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• 2005

Due to the importance of lead time demand in the design of inventory management systems, researchers and practitioners have paid continuous attention and a few analytic models using the compound distribution approach have been reported. However, since the nature of compound distributions is hardly amenable, the analytic models have been done by non‐recognition of the compound nature of some components to reduce the analytic task. This study concerns some of the important aspects in the analytic models. Through the theoretic examination of the analytic model approach and the comparison with the rigid compound stochastic process approach, this study clarifies the assumptions implicitly made by the analytic models and provides some precautions in using the analytic models. Illustrative examples are also presented.

• 한국정밀공학회지
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• 제19권12호
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• pp.142-149
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• 2002

In this paper, the metal forming process is caused of rise of the unit cost of production in increase of the lead-time and cost because of manufacturing final product through a few the number of processes. Flow control complex forming is proposed to put into formulation in order to apply cold forging from conventional approximate similarity theory, and the forming loads of the real material(AISI 1008) can be calculated by put at the new similarity formula the load by plasticine model material experiment through hub clutch. In order to reduce lead-time and cost the technology is used to manufacture with lower die of this product. By the application synthetic resin as the raw material, it is have the merit such short lead-time, low cost, good surface finish etc., as compared with the machine work.