• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.139-143
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• 2011

금속분말을 청정 에너지원으로 이용하기 위해 금속분말 소형 연소기의 구현이 필요하다. 이를 위한 기초 연구로서 점화성이 뛰어나면서도 경제적인 수십 마이크로 크기의 마그네슘(Mg) 분말을 대상으로 고온 증기(steam)와의 연소 현상 대해 연구하였다. 본 연구에서는 연소실 내 체류시간 및 혼합 효율을 증가시키기 위해 와류 유동을 연소기에 적용하였고 아르곤(Ar) 이송가스를 이용해 마그네슘 분말을 공급하였다. 안정한 화염을 유지시키기 위하여 이송가스의 유량을 변화시켜 공급되는 마그네슘의 양을 조절하였고, 고온 증기의 공급량은 니들 밸브의 개도를 조정하거나 우회시킨 관로로 증기의 일부를 배출함으로써 조절하였다. 고온의 점화원을 사용하여 증기 분위기 내 마그네슘 분말을 점화시켜, 대기압 환경에서 마그네슘/증기/아르곤의 지속적인 화염을 구현하였다.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.3
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• pp.280-287
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• 2009

High-tech microelectronics industry is known as one of the most chemical-intensive industries. In Korea, Microelectronics industry occupied 38% of export and 16% of working employees work in microelectronics industry. But, chemical information and health hazards of high-tech microelectronics manufacturing are poorly understood because of rapid development and its penchant for secrecy. We need to investigate on chemical use and exposure control. We Site-visits to 6 high-tech microelectronics manufacturing company which have cleanroom work using over 1,000kg organic solvents (5 semi-conductor chips and its related parts company, 1 liquid crystal display (LCD)). We reviewed their data on chemical use and ventilation system, and measured TVOCs (Total Volatile Organic Compounds) and carbon dioxide concentration. All cleanroom air passed through hepa filters to acheive low particle levels and only 1 cleanroom uses carbon filters to minimize the organic solvents exposures In TVOC screening test, Cleanroom for semi-conductor chips and its related parts company with laminar down flow system (e.g. class 1~100) showed nondetectable level of TVOCs concentration, but Cleanroom for liquid crystal display (LCD) with conventional flow system (e.g. class 1,000~10,000) showed 327 ppm as TVOCs. Acetone concentration in cleanroom for Jig cleaning, LC Injection, Sealing processes were 18.488ppm (n=14), 49.762 ppm (n=15), 8.656 ppm (n=14) as arithmetric mean. Acetone concentration in cleanroom for LCD inspection process was 40ppm (n=55) as geometric mean, where the range was 7.8~128.7ppm and weakly correlated with ventilation rate efficiency(r=0.44, p<0.05). To control organic solvents in cleanrooms, chemical and carbon filters should be installed with hepa filters. Even though their volatile organic compounds concentration was not exceed to occupational exposure limits, considering of entrance limited cleanroom environment, long-term period exposure effects and adverse health effects of cleanroom worker need further reseach.

• Clean Technology
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• v.19 no.2
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• pp.113-120
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• 2013

The treatment of chemically stable perflourocompounds (PFCs) requires a large amount of energy. An energy efficient arc plasma system has been developed to overcome such disadvantage. $CF_4$, $SF_6$ and $NF_3$ were injected into the plasma torch directly, and net plasma power was estimated from the measurement of thermal efficiency of the system. Effects of net plasma power, waste gas flow rate and additive gases on the destruction and removal efficiency (DRE) of PFCs were examined. The calculation of thermodynamic equilibrium composition was also conducted to compare with experimental results. The average thermal efficiency was ranged from 60 to 66% with increasing waste gas flow rate, while DRE of PFCs was decreased with increasing gas flow rate. On the other hand, DRE of each PFCs was increased with the increasing input power. Maximum DREs of $CF_4$, $SF_6$ and $NF_3$ were 4%, 15% and 90%, respectively, without reaction gas at the fixed input power and waste gas flow rate of 3 kW and 70 L/min. A rapid increase of DRE was found using hydrogen or oxygen additional gases. Hydrogen was more effective than oxygen to decompose PFCs and to control by-products. The major by-product in the arc plasma process with hydrogen was hydrofluoric acid that is easy to be removed by a wet scrubber. DREs of $CF_4$, $SF_6$ and $NF_3$ were 25%, 39% and 99%, respectively, using hydrogen additional gas at the waste gas flow rate of 100 L/min and the input power of 3 kW.

• Journal of dental hygiene science
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• v.4 no.1
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• pp.7-11
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• 2004

The purpose of this study was to investigate the distribution of microorganisms and the degree of contamination in the air of the dental clinics and to offer basic data as to the contamination of medical equipment and the prevention of the clinics. With this in mind, the researcher gathered air samples from the waiting rooms and medical offices of nine dental clinics in the city of J, South Korea with the use of a method of natural inattention and an air sampler and cultivated the samples on the plain table and drew from it bacteria falling and separated and sorted out the colony with the help of ATB and detected the distribution of the germs. The results are following, The number of bacteria falling in the air of the dental clinics was less than 10(CFU/Plate) with the exception of one dental clinic. This implies that they fit in with standards for hygiene. The number of bacteria falling in the air of the medical offices was less than 10(CFU/Plate) with the exception of one dental clinic. This implies that they fit in with standards for hygiene. The survey on the detection of staph. aureus reveals that all the dental clinics with the exception of B dental clinic proving to be positive had non-pathogenic staphylococci detected. The survey on the detection of pathogenic gram negative bacilli indicates that all the dental clinics but one were none detected. The survey on the distribution of germs shows that germs in 7 out of 9 dental clinics were none detected, and that they in four out of 9 waiting rooms were none detected. All the germs detected in the others were mostly non-pathogenic. The study shows that all the subject dental clinics but one were hygienically controlled and that there was a difference in accordance with cleaning and sterilization. This means that dental clinics should be equipped with systematic programs for cleaning and sterilization designed to prevent infection.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.1
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• pp.18-23
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• 1985

내연기관은 자동차용 기관에 의하여 일반대중과 접촉하게 되었으며, 특히 20세기 중반에 이르러 자동차라는 기계가 일반가정에서 사용되는 가구로 탈피하는 과정에서 그 중요장치의 하나인 자동차용 기관도 전문가가 취급하는 기계로부터 일반인이 취급하는 가구로의 탈피를 요구함에 따라 크게 발전해 온 것이 사실이다. 종래, 내연기관의 설계에 있어서 그 출력과 연료소비를 가장 중요한 성능평가의 요소로 삼아왔지만, 가구로서의 자동차의 최적화를 위해서는 더욱 중요한 많은 성능평가의 요소가 있다는 것을 인식할 필요가 있다고 생각한다. 실은 최적화에 필요한 많은 요소의 균형을 어떻게 할 것인가 하는 것이 자동차용 기관의 설계에 있어서 가장 중요한 일이라 생각되며, 자동차용 기관을 계획할 때의 목표는 다음과 같은 3가지로 생각된다. (1) 고성능일 것 (2) 우수한 기능을 가질 것 (3) 공해가 없을 것 (1)의 고성능을 추구하는데 있어서는 비출력, 연료소비율 및 양호한 응답성이 중요한 요소로 된다. 이중 응답성의 문제는 연료공급기구나 조속기 등의 기능적인 요소와 깊은 관련이 있다. 그리고 내구성, 신뢰성, 정비점검의 무용성이라는 것이 (2)의 우수한 기능을 보장하기 위한 가장 중요한 배경으로 된다. 또한 진동이나 소음이 없고 정숙할 것이 (3)의 무공해성의 목표와도 관 련되는 중요한 요소이다. 배출가스의 무공해화가 자동차에 의한 공해방지의 입장으로부터 중요한 요소가 되는 것은 주지의 사실이다. 그리고 이 배출가스의 청정화의 문제는 성능향상을 위한 비출력증대의 방향에 대한 방해가 되는 문제이다. 이상 기술한 바와 같은 설계단계에 있어서의 계획목표를 3가지로 설정하고, 이 3가지 목표에 관련되는 요소의 균형을 어떻게 위해야 할 것인가 하는 점에 초점을 맞추어 되도록 쉽게 기술하고자 하였으나, 미비한 점이 많았을 것으로 생각하여, 다만 이 분야에 종사하는 기술자 여러분에게 약간의 도움이라도 되었으면 하는 것이 소망이다.

• Korean Journal of Computational Design and Engineering
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• v.21 no.1
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• pp.69-77
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• 2016

The purpose of this study is to estimate the energy expenditure of working in a clean room for manufacturing embedded needles by ergonomic programs. Embedding needle is one of medical devices and it should be manufactured in a clean room. 3D static strength prediction program was used to analyze the slow movements during embedding needle manufacturing in a clean room. Also the energy expenditure prediction program was used to estimate energy expenditure rates for materials handling tasks to help assure worker safety and health in clean room. The energy expenditures of the tasks were calculated using prediction equations derived from empirical data. The energy expenditure rate of 3.09 kcal/min in a clean room didn't exceed the 3.5 kcal/min action limit guideline for an average 8-hour day set by the National Institute for Occupational Safety and Health (NIOSH). Energy consumption was calculated on the same working conditions as EEPP program, using an average body weight of female 20 years old to 59 years who would be the candidates of the real workers.

• The Journal of Korean Medicine
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• v.22 no.3
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• pp.81-91
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• 2001

Objectives : This study was prepared for investigating the clinical features of stroke patients. Methods : We retrospectively reviewed the medical records of 177 patients who were admitted to the Dept. of Internal Medicine, College of Oriental Medicine, Kyungwon University with a diagnosis of stroke from Jan. I, 1999 to Dec. 31, 1999. Results : Ischemic stroke (74.0%) was more common than hemorrhagic stroke (19.8%). The proportion of males was 53.7%, of females was 46.3%, and the most prevalent age group is those in their sixties. Cerebral infarction was most frequently noticed in MCA territory, hemorrhage in putamen. Hypertension was the most common preceding disease, followed by diabetes mellitus. The rate of recurrence was high in cerebral infarction. The onset mode of cerebral infarction was sleeping and rising and of cerebral hemorrhage was acting. Most patients visited the hospital within 24 hours. The most common symptoms at admission were motor weakness and speech disorder. The most common complication was urinary tract infection. Admission period was 29.5 days. Physical treatment from onset in cerebral infarction and in cerebral hemorrhage was 17.4 and 22.0 days, respectively. Conclusions : Our study of CVA patients was similar to previous studies from 1994 to 1998. In most cases, western and oriental treatment and medicine were given synthetically. Prescription of sasang constitutional medicine had wide application.

• Clean Technology
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• v.28 no.1
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• pp.46-53
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• 2022

The agglomeration characteristics of coal and silica sand were investigated under various conditions using mixed samples consisting of coal, silica sand, and potassium hydroxide, which is an agglomeration accelerator. The samples were prepared by either physically mixing or using aqueous solutions. The experiments using the physically mixed powder samples were performed with a two hour reaction time. The results showed that the number of aggregates generated increased as the reaction temperature and the total potassium content increased. The experiments using aqueous solutions were performed at 880 ℃, which is the operating temperature of a fluidized bed boiler, and at 980 ℃, which assumes a local hot spot. The amount of agglomeration generated as the reaction time increased and the total potassium content increased was identified. In the experiment performed at 880 ℃, the amount of aggregate generated clearly increased with the reaction time, and in the experiment performed at 980 ℃, assuming a local hot spot, a large amount of aggregate was generated in a relatively short time. The aggregates became harder as the potassium content increased. When the total potassium content was less than 1.37 wt.%, the aggregates were weak at both temperatures and collapsed even with a slight impact. Additionally, the surface characteristics of the silica sand and ash aggregates were observed by SEM-EDS analysis. The analysis revealed a large amount of potassium at the bonding sites. This result indicates that there is a high possibility of aggregation in the form of a eutectic compound when the alkali component is increased.

• Journal of Food Hygiene and Safety
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• v.27 no.4
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• pp.420-426
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• 2012

The purpose of this study was to identify control points through microbiological hazard analysis in the manufacturing processes of starch noodles. Samples were collected from the ingredients, manufacturing processes, equipment and environment. Microbiological hazard assessments were performed using aerobic plate counts (APC), Enterobacteriaceae (EB), E. coli and five pathogens including B. cereus, E. coli O157:H7, L. monocytogenes, Salmonella spp., and S. aureus. The APC levels in raw materials were from 2.12 to 3.83 log CFU/g. The contamination levels after kneading were 4.31 log CFU/g for APCs and 2.88 log CFU/g for EB counts. APCs decreased to 1.63 log CFU/g and EB were not detected after gelatinization, but their levels slightly increased upon cooling, cutting, ripening, freezing, thawing, and separating. The reuse of cooling and coating water would be a critical source of microbial increase after cooling. After drying, APCs and EB counts decreased to 5.05 log CFU/g and 2.74 log CFU/g, respectively, and the levels were maintained to final products. These results suggest that the cooling process is a critical control point for microbiological safety, and the cooling water should be treated and controlled to prevent cross contamination by pre-requisite program.

• Analytical Science and Technology
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• v.28 no.5
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• pp.309-316
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• 2015

The analytical method of lead in plasma by ICP-MS was validated after securing environment within class 1,000 classification. We tested specificity and accuracy of within-run and between-run. According to measurement of the amount of suspended particulates in a clean room, 0.3~62 particles were detected in 0.3 µm size while 0.0~28.3 particles were observed in 0.5 µm size. Total suspended particulates met required environment with up to 90.3 particles. The MDL (Method detection limit) of the sample which has been fabricated using fetal bovine serum (FBS) blank was 1.77 ng/L, and LOQ (Limit of quantification) was 5.55 ng/L. The slope, intercept and correlation coefficient of the calibration curve were y=1.09×10⁻³x+4.88×10⁻² and r=0.9999, which showed good correlation. The specificity, within-run and between-run accuracy satisfied the standard at more than 50 ng/L. The average lead concentration in plasma of the general people, current workers and retired workers was 55.4 ng/L, 440 ng/L, and 132 ng/L.