• Journal of applied mathematics & informatics
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• 제8권2호
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• pp.519-530
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• 2001

A two commodity continuous review inventory system with independent Poisson processes for the demands is considered in this paper. The maximum inventory level for the i-th commodity fixed as $S_i$(i = 1,2). The net inventory level at time t for the i-th commodity is denoted by $I_i(t),\;i\;=\;1,2$. If the total net inventory level $I(t)\;=\;I_1(t)+I_2(t)$ drops to a prefixed level s $[{\leq}\;\frac{({S_1}-2}{2}\;or\;\frac{({S_2}-2}{2}]$, an order will be placed for $(S_{i}-s)$ units of i-th commodity(i=1,2). The probability distribution for inventory level and mean reorders and shortage rates in the steady state are computed. Numerical illustrations of the results are also provided.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 International Symposium
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• pp.165-172
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• 2003

Wafer-level packaging technology has become established with increase of demands for miniaturizing and realizing lightweight electronic devices evolution. This packaging technology enables the smallest footprint of packaged chip. Various structures and processes has been proposed and manufactured currently, and products taking advantages of wafer-level package come onto the market. The package enables mounting semiconductor chip on print circuit board as is a case with conventional die-level CSP's with BGA solder bumps. Bumping technology is also advancing in both lead-free solder alternative and wafer-level processing such as stencil printing using solder paste. It is known lead-free solder bump formation by stencil printing process tend to form voids in the re-flowed bump. From the result of FEM analysis, it has been found that the strain in solder joints with voids are not always larger than those of without voids. In this paper, characteristics of wafer-level package and effect of void in solder bump on its reliability will be discussed.

• 환경위생공학
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• 제18권2호
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• pp.60-66
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• 2003

This study was carried out to elucidate the preventive mechanism of molybdenum on lead-induced neuropathy, An animal model of lead neuropathy was induced by feeding diet containing lead to Sprague-Dawley rat for three weeks. Four weeks aged Sprague-Dawley rats were divided into four groups : normal control group, 10ppm-lead treated group, 1mg/kg-molybdenum treated group, 10ppm-lead and 1mg/kg-molybdenum treated group. The parameters on neuropathy were examined by measuring concentration of myo-inositol and myo-inosito uptake in sciatic nerve. In the lead-treated rats, myo-inositol concentration and myo-inositol uptake rate were reduced by from 54% to 33% respectively. This deficit results from that myo-inositol uptake system which is carrier mediated and sodium-potassium dependent was inhibited by the lead treatment. However, the molybdenum administration significantly eliminated the impairment and maintained myo-inositol concentration to about 82% of normal level. These results suggest that lead-induced neurotoxicity was significantly reduced by administration of molybdenum and the mechanism might be partly normalization of myo-inositol uptake system in sciatic nerve.

• 환경위생공학
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• 제18권1호
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• pp.30-40
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• 2003

The study subjects included the workers who were estimated to have been exposed in a low density of lead-laden glaze from pottery manufacturers. They were evaluated in terms of PbB and PbU as indices of lead concentration in the body, and Hb, Hct, ALAD, and FEP as indices of biochemical lead poisoning. Consequently, the study results revealed the relationship between each of indices and its effectiveness to indicate the degree of occupational lead exposure. 1. The mean of PbB was $22.85{\;}{\mu}g/d{\ell}$(range; $4.2~44.7{\;}{\mu}g/d{\ell}$) and PbU $45.69{\mu}g/d{\ell}$(range; $6.7~87.5{\mu}g/d{\ell}$), to indicate the level of lead exposure in the subjects. 2. While there was a high, linear correlation between PbB, PbU and FEP (r=0.835, r=0.855, respectively), a low correlation existed between PbB and ALAD(r=-0.240). 3. While there was a high, linear correlation between PbU and FEP(r=0.825), a low correlation existed between PbU and ALAD(r=-0.352). The above results suggest that FEP can be used as a highly useful biochemical index of lead poisoning, based on its high correlation with PbB and PbU indicating lead concentration in the body.

• 한국산업보건학회지
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• 제6권2호
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• pp.265-271
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• 1996

This study was conducted to investigate distribution of lead particles by operation of industry, to evaluate the effect of particle size on the absorption to workers, and to recommend the Occupational Health Standard for lead. Total lead concentrations in the secondary smelting industry were higher than those in the battery and litharge manufacturing industry. Total lead concentrations in other industries except radiator manufacturing industry exceeded the standard of $50{\mu}g/m^3$. Only radiator manufacturing industry indicated lead concentrations significantly lower than those in other industries(p<0.05). Average blood lead level of workers was $85.1{\mu}g/dl$ in secondary smelting manufacturing, $51.3{\mu}g/dl$ in the battery manufacturing, and below $40{\mu}g/dl$ in the litharge and radiator manufacturing industry. Blood lead levels of workers by industry were significantly different(p<0.05). From relationship between airborne lead concentrations by size and lead in blood, confidence limits of airborne lead concentration equivalent to $40{\mu}g/dl$ of permissible limit in blood, was $147.9-489.8{\mu}g/m^3$ as total lead and $28.8-79.4{\mu}g/m^3$ as ACGIH-RPM. It is recommended that two separate occupational health standards for lead should be established by particle size. Airborne concentration of $150{\mu}g/m^3$ as fatal lead dust and $30{\mu}g/m^3$ as respirable lead dust was recommended.

• Journal of Nutrition and Health
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• 제17권3호
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• pp.193-198
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• 1984

Rice, the staple food in Korea, is deficient to some extent in protein, lipid and vitamins. This study was carried out in order to investigate the effects of dietary supplementation to the rice diet of cellulose, ginseng, and ${\alpha}$-tocopherol on lead toxicity in rats. Using male rats fed the rice diet with the distilled drinking water containing 750mg of lead as nitrate per liter, for 11 weeks, organ weights, hemoglobin levels, serum glutamic pyruvic transaminase activity and accumulation of lead in liver, blood and kidney were observed. Supplementation of cellulose, ginseng and ${\alpha}$-tocopherol to the lead groups showed the protective effect significantly in the weight of liver but no influence in hemoglobin levels. Ginseng especially decreased the serum glutamic pyruvic transaminase activity to normal level. The three supplemented diets reduced the lead accumulation in kidney and blood, but not in liver.

• 대한의생명과학회지
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• 제12권4호
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• pp.371-374
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• 2006

This study was carried out to investigate the relationship of the cadmium and lead levels in blood by age, gender and smoking status among 181 students in Gyeongnam province from June 2005 to July 2006. The cadmium and lead levels in blood was analyzed by atomic absorption spectrophotometer. Subjects were classified for the investigation according to smoking status as smokers and nonsmokers, age and gender. Mean blood cadmium level in male and female was $1.65{\mu}g/dl,\;1.10{\mu}g/dl$ respectively. Male was significantly higher than that of female. Blood cadmium levels in heavy smokers ($11{\sim}20\;ea/day$) and light smokers ($1{\sim}10\;ea/day$) were $2.34{\mu}g/dl,\;1.10{\mu}g/dl$ respectively. Heavy smokers were significantly higher than those of light smokers. In the comparison of age, gender and smoking status in blood Lead levels were no significant differences. In conclusion, heavy smoking was the most significant risk factor to increase blood cadmium levels. The further study will need analysis of the other factors related to the elevation of the cadmium and lead levels.

• Environmental Analysis Health and Toxicology
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• 제9권1_2호
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• pp.1-8
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• 1994

Nerve conduction impairment in lead neuropathy has been empirically linked to altered nerve myo-inositol metabolism. In most cases of neuropathy, abnormal myo-inositol metabolism is associated with abnormal $Na^+/K^+$ATPase provides a potential mechanism to relate defects of the myo-inositol metabolism in the peripheral nerve treated with lead. Therefore, the effect of lead on the rat sciatic nerve $Na^+/K^+$ATPase and other ATPase of sciatic nerve was studied. ATPase activity was measured enzymatically in sciatic nerve homogenates from 2-wk lead treated neuropathy rats and age-mached controls administered myo-inositol. $Na^+/K^+$ATPase components were assessed by ouabain inhibition or the omission of sodium and potassium ions. Lead reduced 50% reduction in the $Na^+/K^+$ATPase activity in homogenates of sciatic nerve. The 50% reduction in the $Na^+/K^+$ ATPase activity was selectively prevented by myo-inositol treatment. This study suggests that the toxic mechanism of the lead on peripheral nerve may be through reduction in $Na^+/K^+$ATPase activity which has been linked to axonal transport slowing in the rat model of lead neuropathy, via direct changes by the perturbation of the intracelluar sodium or potasium level.

• 한국환경보건학회지
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• 제37권6호
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• pp.418-428
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• 2011

Objectives: The purpose of this study was to examine the cross-sectional relationship between low blood lead levels and increasing blood pressure among Korean adults using a nationally representative sample of the Korean population: the Korea National Health and Nutrition Examination Survey (KNHANES) 2008. Methods: A total of 918 subjects aged 40 and older and not currently being treated for hypertension participated in this study. Information about age, gender, smoking status, alcohol consumption, education level, and the use of anti-hypertensive medication was collected. The blood pressure was defined as the mean of the second and the third measurements after three time measurements. Lead levels were determined by an analysis of blood samples. Multiple linear and logistic regression analyses were implemented after adjusting for covariates including age, gender, educational level, smoking status, alcohol consumption, and BMI. Results: This study showed that the average differences in systolic and diastolic blood pressure comparing the lowest to highest quintile of blood lead were 4.33 mmHg (95% CI, 0.66-8.00; p for trend = 0.027) and 2.66 mmHg (95% CI, 0.26-5.06; p for trend = 0.021), respectively. After multivariate adjustment for covariates, the prevalence odds ratio (POR) of subjects in the highest quintile was associated with a 1.70-fold increase in the risks of hypertension (95% CI, 0.83-3.49; p for trend test = 0.112) over those in the lowest quintile of blood lead concentration, However, it was not statistically significant. Conclusions: This study provided evidence for an association between low- levels of blood lead and elevations in blood pressure and risk for hypertension in the general population of Korea.

• 대한지역사회영양학회지
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• 제12권6호
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• pp.773-781
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• 2007

The objective of this study was to investigate the nutritional and health status of women industrial workers by working fields. One hundred forty eight (105 lead and 43 office) workers were recruited from March 2005 to October 2005. Information on age, education, smoking and drinking status were collected using questionnaire and nutrient intake and diet quality of workers were assessed by average of two-day 24 hr recall method. Biochemical indexes including blood lead level (PbB), indexes for iron status, serum calcium (Ca) and serum lipid profiles were analyzed from fasting venous blood or serum. Results showed that education level of lead workers was lower than that of office workers (p<0.05), but nutrient intake levels were not significantly different by working fields. Overall nutritional status of the subject were good except for calcium, vitamin $B_2$, C and folic acid intakes. PbB of lead workers were significantly higher than that of office workers while mean corpuscular hemoglobin concentration (MCHC) and serum Ca levels were significantly lower in lead workers. MCHC was positively correlated with zinc intake (r=0.166) and serum Ca was positively correlated with vitamin C intake (r=0.179). This study confirms that lead workers need extra care to keep their health and nutritional management especially for the nutrients known to interact with lead. Tailored nutrition education for workers at specific working fields needs to be more focused for the improvement of health status of industrial workers.