• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.666-670
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• 2013

Recovery method of silicon wafer from defective products generated from manufacturing process of silicon solar cells was studied. The removal effect of the N layer and antireflection coating (ARC) of the waste solar cell were investigated at room temperature ($25^{\circ}C$) by variation of concentration of $H_3PO_4$, $NH_4HF_2$, and concentration and types of chelating agent. Removal efficiency was the best in the conditions; 10 wt% $H_3PO_4$ 2.0 wt% $NH_4HF_2$, 1.5 wt% Hydantoin. Increasing the concentration of $H_3PO_4$, the surface contamination degree was increased and the thickness of the silicon wafe became thicker than the thickness before surface treatment because of re-adsorption on the silicon wafer surface by electrostatic attraction of the fine particles changed to (+). The etching method by mixed solution of $H_3PO_4$-$NH_4HF_2$-chelating agents was expected to be great as an alternative to conventional RCA cleaning methods and as the recycle method of waste solar cells, because all processes are performed at room temperature, the process is simple, and less wastewater, the removal efficiency of the surface of the solar cell was excellent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.485-493
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• 2017

Rearing knowledge is a significant factor of relevance for rearing practice, and assessment of rearing knowledge and practice is important for infant parents. The author adopted the Child Rearing Knowledge Scale (CRKS) and Child Rearing Practice Scale (CRPS) that were developed and validated by Saramma & Thomas. According to the international linguistic validation process, pilot testing was done based on 20 infant's mothers in one Oketani massage center and one public health center. Descriptive statistic methods and Wilcoxon Rank Sum Test were employed to evaluate the level and compare the mean score according to general characteristics of subjects of the tools. Reliability and validity were tested by Cronbach's alpha and Spearman Correlations. The mean age of the subjects was 33.94 (${\pm}2.99$) years and the mean age of babies was 3.35 (${\pm}0.58$) months. The understanding level of the Korean version of the CRKS and CRPS was 1.80 (${\pm}0.65$) and 1.33 (${\pm}0.54$), respectively. In addition, the CRKS and CRPS were relatively easy to use. The mean score of the CRKS was 22.50 (${\pm}4.89$), which was a moderate score, while the mean score of the CRPS was 30.75 (${\pm}2.04$), which was high. The Cronbach's alpha values of the CRPS were as follows: feeding, 0.71; growth and development, 0.64; cleaning and protection 0.68; infant stimulation, 0.77. There was a significant correlation between infant stimulation of the CRPS and growth and development of the CRKS (r=0.530, p=0.016). The CRKS score of medical staff was significantly higher than that of non-medical staff (p=0.04). The CRKS and CRPS are expected to be used in clinical or community care practice as easy-to-use tools that are easy to respond to.

• Journal of Conservation Science
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• v.27 no.4
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• pp.441-450
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• 2011

This study investigated potential damages and conservation methods for the ceramics (without glaze) by examination of physical and chemical effects from the burial environments. For this study, pottery samples excavated from Daejeon Hakha, Asan Eumbong, Hwasung Sogeunsan and Kongju Haengbokdosi were examined with released ions and extraction through desalination. The result showed that the ion inflow into the ceramics was dependent upon the porosity and the absorption of ceramics. The high temperature fired ceramics (over $1,000^{\circ}C$) have low porosity and absorption, therefore almost no salt infiltration during the burial period. However, low temperature fired ceramics (under $800^{\circ}C$) have high porosity and absorption, and most of salts were removed during the desalination. The 40 to 60% of salts were removed in two days and 60 to 80% of slats were released in a week. Furthermore, fertilizer residues such as $K_2SO_4$, in soils were detected in the ceramcis. Also the characteristics of buried soil affected ion infiltration into ceramics. Ceramics buried in sandy soil had relatively less ion contents from buried environments than those in clayey soil. Therefore, low temperature fired ceramics could do not only cleaning but also desalination if it is necessary, and the period could be decided to the condition of ceramics.

• Journal of Food Hygiene and Safety
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• v.12 no.3
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• pp.240-253
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• 1997

The main problems contributing to food poisoning outbreaks in institutional settings and a home were reviewed and analyzed through the epidemiological investigations of food poisoning. The major documented factors included improper holding temperatures, inadequate cooking, poor personal hygiene, cross-contamination and contaminated equipment, food from unsafe sources, failure to follow food hygiene policies, and lack of education, training, monitoring and superivision. Usually more than one factor contributed to the development of an outbreak. (1) Use of improper holding temperatures was the single most important factor contributing to food poisoning. They included improper cooling, allowing a laps of time (12 hours or more) between preparing food and eating it, improper hot holding, and inadequate or improper thawing. Food thermometers were not used in most of the instances. (2) In inadequate cooking, the core temperature of food during and after cooking had not been measured, and routine monitoring was limited to recording the temperature of plated meals. Compared with conventional methods of cooking, microwave ovens did not protect against food poisoning as effectively. Centralized food preparation potentially increased the risk of food poisoning outbreaks. (3) Poor personal hygiene both at the individual level (improper handwashing and lack of proper hygienic practices) and at the institutional level (poor general sanitization) increased the risk of transmission. Person to person transmission of enteric pathogens through direct contact and via fomites has been noted in several instances. (4) Obtaining food from unsafe sources was a risk factor in outbreaks of food poisoning. Food risks were high when food was grown or harvested from contaminated areas. Possibilities included contamination in the field, in transport, at the retail site, or at the time it was prepared for serving. (5) Cross-contamination and inadequate cleaning/handling of equipment became potential vehicles of food poisoning. Failure to separate cooked food from raw food was also a risk factor. (6) Failure to follow food hygiene policies also provided opportunities for outbreaks of food poisoning. It included improper hygienic practices during food preparation, neglect of personnel policies (involvement of symptomatic workers in food preparation), poor results on routine inspections, and disregarding the results and recommendations of an inspection. (7) Lack of formal and in-service education, training, monitoring, and supervision of food handlers or supervisors were critical and perhaps neglected elements in occurrences of food poisoning.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.28-34
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• 2005

The aim of this article is to assess the application characteristics of the site by remediating oil-contaminated area using DSB (Deep-site Biopile) system. In the contaminated area, the soil was composed of penetrable sand and the leaked oil was spread widely (total 7,201 cubic meters) through 2.5 meter deep underground water flow. DSB system was operated for 30 minutes intervals for 24 hours in a day (30 minutes opεration and 30 minutes stop). To check contamination level change in the contaminated area after DSB system was operated, samples were taken. The result from the site shows that BTEX/TPH contamination level was dropped 50% after 30-day operation of DSB system, and that contamination level was dropped below contamination level check standard after 165 days and the remediation was completed. Unlike traditional biological remediation methods DSB system could efficiently process soil and water which were contaminated by high levels of oil compounds.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.369-379
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• 2011

The application of appropriate rehabilitation works can improve productivity and water quality of clogged wells, with extending the operation of the wells for a certain period. This study verified rehabilitation effect of the clogged wells by means of explosive method and air brush surging and by using hydraulic tests, water quality, and geophysical logs (optical and acoustic televiewer logs) before and after the cleaning works on the two wells drilled in bedrock in Mt. Geumjeong, Busan City. Air-brush surging method resulted in maximum 273% increase of the productivity with the concentration of $F^-$, $SiO_2$, and a decrease of turbidity and the concentration of $Cl^-$, $NO_3^-$. The explosive method resulted in maximum 156% increase of the productivity with an increase of the concentration of $F^-$, $SiO_2$ and a decrease of turbidity, $Cl^-$, $NO_3^-$.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.51-56
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• 2009

Safety and quality assessment systems are very important in manufacture, storage, transportation, and handling of hazardous materials(hazmat) to prevent hazmat disasters. At present, hazardous materials exist everywhere in our daily lives with various forms of plastics, household products of cleaning and washing detergents, fertilizers or petroleum-related products. However, hazardous materials are dangerous substances when they are released to human or environment. Hazardous materials become very widely used substances in the age of oil-based industrial economy. The Korean Ministry of Environment (KMOE) describes about one hundred thousand types of chemicals are produced and used worldwide. Over four hundred new chemicals are introduced in every year. A crucial question for the Korean hazardous material management may have been raised: Will you be safe from hazardous material incidents? The gas leak disaster at Union Carbide's Bhopal, India in 1984 that made over 6,400 people killed and 30,000 to 40,000 people seriously injured is the representative case for the safety of hazmat. Korea becomes vulnerable to hazmat disaster due to the development of high-tech industry. Thus, the risk assessment system is required to Korea for transferring abandoned hazmat management systems to self-correcting safety systems. This research analyzed characteristics of various hazmat incidents applying statistical analysis methods including frequency analysis or analysis of category data to hazmat incidents for ten years. All of three analyses of category data indicate the significance of causality between hazmat incident site groups and seasons, regional groups, and incident casualty groups.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.661-673
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• 2007

Rock materials of the three-storied stone pagoda in the Cheongryongsa temple in Korea are mainly composed of gneissose two-mica granite and fine-grained granite. This stone pagoda shows structural instability due to cracks and breaking-out of the stones. The surface properties of the stone is highly degraded by various inorganic pollutants and epilithic biospecies. Therefore, this study carried out comprehensive deterioration diagnosis by non-destructive methods, and some conservation treatments base on the diagnosis were carried out to reduce weathering progress. As the treatments, the biospecies and lichen that covering on the stone surfaces were removed by dry and wet cleaning, and degraded concrete applied to the pagoda for restoration in the past was removed and repaired with epoxy resin. Oxidized iron plates inserted between the rock properties were also substituted titanium stainless steels. After all processes are completed, we sprayed consolidant on the rock surface. Finally, the ground of the stone pagoda was rearranged using small rock aggregates, and the fence was established for control of artificial deterioration by visitors and environmental maintenance.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.3
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• pp.284-294
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• 2006

Statement of problem. Proliferation of Candida albicans is primarily within the plaque on the fitting surface of the denture rather than on the inflamed mucosa. Consequently, the treatment of the denture is equally important as treatment of the tissue. Cleansing and disinfection should be efficiently carried-out as the organisms can penetrate into the voids of the acrylic resin and grow in them, from which they can continue to infect and reinfect bearing tissues. Purpose. The purpose of this study was to evaluate the applicability of photocatalytic reaction to eliminate Candida albicans from acrylic resin denture base, and to investigate the anti-fungal effect with various UVA illumination time. Materials and Methods. The specimens were cured by the conventional method following the manufacturer's instruction using thermal polymerized denture base resin (Vertex RS: Dentimex, Netherlands). $TiO_2$ photocatalyst sol(LT), which is able to be coated at normal temperature, was made from the Ti-alkoxide progenitor. The XRD patterns, TEM images and nitrogen absorption ability of the $TiO_2$ photocatalyst sol(LT) were compared with the commercial $TiO_2$ photocatalyst P-25. The experimental specimens were coated with the mixture of the $TiO_2$ photocatalyst sol(LT) and binder material (silane) using dip-coater, and uncoated resin plates were used as the control group. Crystallinity of $TiO_2$ of the specimen was tested by the XRD. Size, shape and chemical compositions were also analyzed using the FE-SEM/ EDS. The angle and methylene blue degradation efsciency were measured for evaluating the photocatalytic activity of the $TiO_2$ film. Finally, the antifungal activity of the specimen was tested. Candida albicans KCTC 7629(1 ml, initial concentration $10^5$ cells/ ml) were applied to the experiment and control group specimens and subsequently two UVA light source with 10W, 353 nm peak emission were illuminated to the specimens from 15cm above. The extracted $2{\mu}l$ of sample was plated on nutrient agar plate ($Bacto^{TM}$ Brain Heart Infusion; BD, USA) with 10 minute intervals for 120 minute, respectively. It was incubated for 24 hours at $37^{\circ}C$ and the colony forming units (CFUs) were then counted. Results. Compared the characteristics of LT photocatalyst with commercial P-25 photocatalyst, LT were shown higher activity than P-25. The LT coated experimental specimen surface had anatase crystal form, less than 20 nm of particle size and wide specific surface area. To evaluate the photocatalytic activity of specimens, methylene blue degradation reaction were used and about 5% of degradation rate were measured after 2 hours. The average contact angle was less than $20^{\circ}$ indicating that the LT photocatalyst had hydrophilicity. In the antifungal activity test for Candida albicans, 0% survival rate were measured within 30 minute after irradiation of UVA light. Conclusion. From the results reported above, it is concluded that the UVA-LT photocatalytic reaction have an antifungal effect on the denture surface Candida albicans, and so that could be applicable to the clinical use as a cleaning method.

• Safety and Health at Work
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• v.4 no.3
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• pp.142-148
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• 2013

Background: To elucidate the relationship between seven occupational dermatoses (ODs) and 20 types of work in Greece. Methods: This was a prevalence epidemiologic study of certain ODs among 4,000 workers employed in 20 types of enterprise, in 104 companies, in 2006-2012, using data from company medical records, questionnaires, occupational medical, and special examinations. The ${\chi}^2$ test was applied to reveal statistically significant relationships between types of enterprises and occurrence of ODs. Results: A high percentage (39.9%) of employees included in the study population suffered from ODs. The highest prevalence rates were noted among hairdressers (of contact dermatitis: 30%), cooks (of contact dermatitis: 29.5%), bitumen workers (of acne: 23.5%), car industry workers (of mechanical injury: 15%), construction workers (of contact urticaria: 29.5%), industrial cleaning workers (of chemical burns: 13%), and farmers (of malignant tumors: 5.5%).We observed several statistical significant correlations between ODs (acute and chronic contact dermatitis, urticaria, mechanical injury, acne, burns, skin cancer) and certain types of enterprises. There was no statistically significant correlation between gender and prevalence of ODs, except for dermatoses caused by mechanical injuries afflicting mainly men [${\chi}^2(1)=13.40$, p < 0.001] and for chronic contact dermatitis [${\chi}^2(1)=5.53$, p=0.019] afflicting mainly women. Conclusion: Prevalence of ODs is high in Greece, contrary to all official reports by the Greek National Institute of Health. There is a need to introduce a nationwide voluntary surveillance system for reporting ODs and to enhance skin protection measures at work.