• Journal of Community Nutrition
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• v.3 no.2
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• pp.96-102
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• 2001

A cross-sectional study was performed to estimate the nutritional status of Korean male lead workers and to assess the relationship between calcium nutritional status and blood lead levels. A flood consumption survey was conducted by the 24-hr recall method with 118 lead workers and 63 non-lead exposed controls. Blood lead levels were analyzed from whole blood and serum calcium concentrations were also assessed. Results of dietary analysis showed Korean lead workers consumed relatively sufficient nutrients (more than 75% of RDA) except, calcium. Mean dietary calcium intake of lead workers was 502.2mg(72% of RDA) while that of the non-lead workers was estimated as 600.8mg(86% of RDA). Intakes of protein, iron, niacin and vitamin C of lead workers were significantly lower than those of non-lead workers. There was a wide range of blood lead levels(5.5 to 73.5$\mu\textrm{g}$/㎗) observed while mean blood lead level of lead workers was 30.9$\mu\textrm{g}$/㎗. However, 98% of lead workers showed normal serum ca1cium concentrations (range ; 8.9 to 10.7mg/㎗, mean ; 9.77mg/㎗) while 66% of lead workers were estimated to intake a dietary calcium lower than 75% of RDA. Mean blood lead levels of non-1ead workers were significantly lower(mean ; 5.1$\mu\textrm{g}$/㎗, p ＜ 0.001) and the serum calcium concentration was significantly higher(mean ; 10.20mg/㎗, p ＜ 0.001) than lead workers. Results of unadjusted correlation showed that serum calcium level and dietary calcium intake were negatively correlated with blood lead concentration. In a multiple regression of blood lead levels with variables known as affecting blood lead 1eve1 such as age, body mass index and occupational lead exposure, serum calcium was insignificant while dietary calcium intake showed statistically significant(p ＜ 0.05) relation. Since calcium is a very important nutrient to reduce hazardous effects of lead, it should be strongly recommended that lead workers need to increase dietary calcium intake.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.60
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• pp.11-22
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• 2000

The main objective of this research is to analyze an order point and an order quantity of a distribution center and each branch to attain a target service level in multi-level inventory distribution system. In case of product item, we use the item with low volume of average monthly demand. Under the continuous review method, the distribution center places a particular order quantity to an outside supplier whenever the level of inventory reaches an order point, and receives the order quantity after elapsing a certain lead time. Also, each branch places an order quantity to the distribution center whenever the level of inventory reaches an order point, and receives the quantity after elapsing a particular lead time. When an out of stock condition occurs, we assume that the item is backordered. For considering more realistic situations, we use generic type of probability distribution of lead times. In the variable lead time model, the actually achieved service level is estimated as the expected service level. Therefore, this study focuses on the analysis of deciding the optimal order point and order quantity to achieve a target service level at each depot as a expected service level, while the system-wide inventory level is minimized. In addition, we analyze the order level as a maximum level of inventory to suggest more efficient way to develop the low demand item model.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.42
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• pp.31-38
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• 1997

The main objective of this research is to develop a model to select the optimal input service level for a distribution center - multi branch inventory distribution system. With the continuous review policy, the distribution center places an order for specific order quantity to an outside supplier, and the order quantity is replenished after a certain lead time. Also, each branch places an order for particular order quantity to the distribution center to satisfy the customer demands, and receives the replenishment after a lead time. When an out of stock condition occurs during an order cycle, a backorder is placed to the upper level to fill the unfilled demands. With these situation, variable demand and variable lead time are used for better industrial practice. Further, actual lead times with a generic lead time distribution are used in developing the control model. Under the actual lead time model, the customer service measures actually attained for the distribution center and each branch are explained as the effective customer service measures. Thus, throughout the optimal control (using computer search procedures), we can select the optimal input service levels for the distribution center and each branch to attain the effective service level for each branch which is consistent with the goal level of service for each branch. At the same time, the entire distribution system keeps minimum inventories.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.179-179
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• 2023

This study suggests a new approach of water level forecasting for extended lead times using original data preprocessing with variational mode decomposition (VMD). Here, two machine learning algorithms including light gradient boosting machine (LGBM) and random forest (RF) were considered to incorporate extended lead times (i.e., 5, 10, 15, 20, 25, 30, 40, and 50 days) forecasting of water levels. At first, the original data at two water level stations (i.e., SW173 and SW269 in Bangladesh) and their decomposed data from VMD were prepared on antecedent lag times to analyze in the datasets of different lead times. Mean absolute error (MAE), root mean squared error (RMSE), and mean squared error (MSE) were used to evaluate the performance of the machine learning models in water level forecasting. As results, it represents that the errors were minimized when the decomposed datasets were considered to predict water levels, rather than the use of original data standalone. It was also noted that LGBM produced lower MAE, RMSE, and MSE values than RF, indicating better performance. For instance, at the SW173 station, LGBM outperformed RF in both decomposed and original data with MAE values of 0.511 and 1.566, compared to RF's MAE values of 0.719 and 1.644, respectively, in a 30-day lead time. The models' performance decreased with increasing lead time, as per the study findings. In summary, preprocessing original data and utilizing machine learning models with decomposed techniques have shown promising results for water level forecasting in higher lead times. It is expected that the approach of this study can assist water management authorities in taking precautionary measures based on forecasted water levels, which is crucial for sustainable water resource utilization.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.3
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• pp.97-110
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• 2017

This study investigates the efficiencies of machine learning models, including artificial neural network (ANN), generalized regression neural network (GRNN), adaptive neuro-fuzzy inference system (ANFIS) and random forest (RF), for reservoir water level forecasting in the Chungju Dam, South Korea. The models' efficiencies are assessed based on model efficiency indices and graphical comparison. The forecasting results of the models are dependent on lead times and the combination of input variables. For lead time t = 1 day, ANFIS1 and ANN6 models yield superior forecasting results to RF6 and GRNN6 models. For lead time t = 5 days, ANN1 and RF6 models produce better forecasting results than ANFIS1 and GRNN3 models. For lead time t = 10 days, ANN3 and RF1 models perform better than ANFIS3 and GRNN3 models. It is found that ANN model yields the best performance for all lead times, in terms of model efficiency and graphical comparison. These results indicate that the optimal combination of input variables and forecasting models depending on lead times should be applied in reservoir water level forecasting, instead of the single combination of input variables and forecasting models for all lead times.

• The Journal of Engineering Geology
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• v.3 no.3
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• pp.241-252
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• 1993

Lead bas been found in the groundwater in Door County, Wiscorsin, with temporally and spatially irregular distribution in concentration. Correlation coeffidents were calculated among lead indicators in groundwater(frequency of lead detections, mean and maximum concentration of lead detections) and seven independent variables(stucture and geographic factors of wells, hydrogeological factors at lead-arsenate mixing sites and the level of soil contamination) which are possibly related to the lead level in groundwater. The significance of relationships was determined statistically by a t-test at the 90% confidence level, and indicated that the spatially located lead-arsenate mixing sites provided the lead in groundwater in the study area. A total of 112 groundwater samples were collected from 5 house wells with previous lead detects. Lead was detected in partides on ifiter papers with $0.45{\;}\mu\textrm{m}$ pore size, but not in filtrates. The result of chemical analysis for lead indicates that lead is associated with partides in groundwater in Door County. Subsequently, the irregular distribution of lead in the county results from the transport of particulate lead along the advective groundwater movement through the preferential pathways sucn as vertical and bedding-plane joints.

• Journal of Environmental Health Sciences
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• v.22 no.3
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• pp.8-16
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• 1996

Effects of water extract of aloe vera on lead-induced neurotoxicity were investigated in sciatic nerve isolated from rat. The mechanism on toxicity reduction by measuring activities of axonal enzymes, metabolism of myo-inositol in nerve, lead concentration in several organs and so on were further examimed. In the lead-treated rats, the transport rate of axonal enzyme, such as acetyl cholinesterase and choline acetyltransferase, was reduced by from 50% to 30% respectively. Reduction in myo-inositol concentration and $Na^+/K^+$ ATPase activity were also observed in sciatic nerve from lead-treated rat. However, the aloe extract administration significantly eliminated the impairment and maintained myo-inositol concentration to about 85% of normal level. Also aloe extract promoted the excretion rate of lead which is accumulated in blood, sciatic nerve and kidney. These results suggest that lead-induced neurotoxicity was significantly reduced by administration of aloe extract and the mechanism might be partly increase in kidney excretion rate of lead and parity normalization of $Na^+/K^+$ ATPase activity which is critical factor in order to keep nerve maintaining normal myo-inositol level.

• Safety and Health at Work
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• v.3 no.3
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• pp.216-223
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• 2012

Objectives: The objectives of this study were to determine the lead levels in blood samples from nielloware workers, to determine airborne lead levels, to describe the workers' hygiene behaviors, and to ascertain and describe any correlations between lead levels in blood samples and lead levels in airborne samples. Methods: Blood samples and airborne samples from 45 nielloware workers were collected from nielloware workplaces in Nakhon Sri Thammarat Province, Thailand. Lead levels were determined by flame atomic absorption spectrometry (FAAS), at a wavelength of 283.3 nm. FAAS was used especially adequate for metals at relatively high concentration levels. Results: The geometric mean of the 45 airborne lead levels was 81.14 ${\mu}g/m^3$ (range 9.0-677.2 ${\mu}g/m^3$). The geometric mean blood lead level of the 45 workers was 16.25 ${\mu}g/dL$ (range 4.59-39.33 ${\mu}g/dL$). No worker had a blood lead level > 60 ${\mu}g/dL$. A statistically significantly positive correlation was found between airborne lead level and blood lead levels (r = 0.747, p < 0.01). It was observed that personal hygiene was poor; workers smoked and did not wash their hands before drinking or eating. It was concluded that these behaviors had a significant correlation with blood lead levels (p < 0.001). Conclusion: Improvements in working conditions and occupational health education are required due to the correlation found between blood leads and airborne lead levels.

• Journal of Yeungnam Medical Science
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• v.3 no.1
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• pp.73-79
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• 1986

This study was conducted to evaluate the effects of lead on the incidence of anemia and to find cases with lead poisoning early among female workers who have been exposed to lead occupationally, for one year from August, 1985. The level of blood lead and hemoglobin concentration were observed for 284 female lead workers and 123 female non-lead workers of industries in the Gumi industrial complex in Kyungpook Province. The average age was $20.3{\pm}2.9$years and $21.1{\pm}3.5$ years in lead workers and non-lead workers, respectively. The average working duration was $26.46{\pm}19.26$ months in lead workers. The mean value of blood lead was $30.11{\pm}6.61{\mu}g/100ml$ and $21.86{\pm}3.75{\mu}g/100ml$ in lead workers and non-lead workers, respectively. There were significant differences between two groups. The mean value of hemoglobin concentration was $14.00{\pm}0.57g/100ml$ and $14.03{\pm}0.64g/100ml$ in lead workers and non-lead workers, respectively. Anemia cases were not observed at Hb concentration below 12g/100ml. The percentages of lead workers at Hb concentration ranged 12.0~13.0g/100ml were 4.5%. There was no dose-response relationship between blood lead level and the incidence of anemia. There were no remarkable differences between age and blood lead level as well as Hb concentration, and between working duration and the level of blood lead and hemoglobin.

• Journal of the Korea Safety Management & Science
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• v.3 no.3
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• pp.55-64
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• 2001

The main objective of this research is to develop a model to select the optimal input service level for a distribution center-multi branch inventory distribution system. With the continuous review policy, the distribution center places an order for specific order quantity to an outside supplier, and the order quantity is replenished after a certain lead time Also, each branch places an order for particular order quantity to the distribution center to satisfy the customer demands, and receives the replenishment after a lead time. When an out of stock condition occurs during an order cycle, a backorder is placed to the upper level to fill the unfilled demands. With these situation, variable demand and variable lead time are used for better industrial practice. Further, actual lead times with a generic lead time distribution are used in developing the control model. Under the actual lead time model, the customer service measures actually attained for the distribution center and each branch are explained as the effective customer service measures. Thus, throughout the optimal control (using computer search procedures), we can select the optimal input service levels for the distribution center and each branch to attain the effective service levels for each branch which is consistent with the goal level of service for each branch. At the same time, the entire distribution system keeps minimum inventories.