• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.99-111
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• 1999

The purpose of this study was to evaluate crystalline silica contents in airborne respirable dusts from various manufacturing industries and to compare analytical ability of two different methods of quantifying crystalline silica, X-ray diffraction(XRD) and Fourie transform infrared spectroscopy(FTIR). Various manufacturing industries with a history of having pneumoconiosis cases and also known to generate dusts containing crystalline silica were investigated. These industries include: ceramics, brick, concrete, and abrasive material etc. The personal respirable dust samples were collected using l0mm, Dorr-Oliver nylon cyclone equipped with 37mm, $5{\mu}m$ pore size. polyvinylchloride (PVC) filters as collection media. All samples were weighed before and after sampling and were pretreated according to the NIOSH sampling and analytical methods 7500, and 7602 for dust collection and quartz analysis. A total of 48 samples were collected from these industries. Initial analyses of these samples showed log-normal distributions for dust and quartz concentrations. Some results from ceramics and stone exceeded current Korean Occupational Exposure Limits. The average concentrations of personal respirable dust by cyclone were 0.43, 0.24, 0.26, 0.42, 0.53 and $0.29mg/m^3$ in ceramics, stone, concrete, glass, briquets, and others, respectively. A comparison of performance of two analytical methods for quantifying crystalline silica was performed using data from ceramics. The results showed that no significant difference was found between two methods for ceramics. The mean crystalline silica contents determined by XRD were 3.41 % of samples from briquets and 7.18 % from ceramics and were 2.58 % from concrete and 10.33 % from ceramics by FTIR. For crystalline silica analysis, two analytical techniques were highly correlated with $r^2=0.81$ from ceramics. Both cristobalite and tridymite were not detected by XRD and FTIR.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.1
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• pp.1-15
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• 2021

Additive manufacturing (AM) for dental materials can produce more complex forms than conventional manufacturing methods. Compared to milling processing, AM consumes less equipment and materials, making sustainability an advantage. AM can be categorized into 7 types. Polymers made by vat polymerization are the most suitable material for AM due to superior mechanical properties and internal fit compared to conventional self-polymerizing methods. However, polymers are mainly used as provisional restoration due to their relatively low mechanical strength. Metal AM uses powder bed fusion methods and has higher fracture toughness and density than castings, but has higher residual stress, which requires research on post-processing methods to remove them. AM for ceramic use vat polymerization of materials mixed with ceramic powder and resin polymer. The ceramic materials for AM needs complex post-processing such as debinding of polymer and sintering. The low mechanical strength and volumetric accuracy of the products made by AM must be improved to be commercialized. AM requires more research to find the most suitable fabrication process conditions, as the mechanical properties and surface of any material will vary depending on the processing condition.

• Korean Journal of Occupational Health Nursing
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• v.22 no.3
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• pp.179-190
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• 2013

Purpose: Regular cancer screening for workers can help prevent cancer or allow early treatment, and is thus beneficial in improving health, reducing costs, and increasing companies' productivity. However, there has been little research on cancer screening rates of workers and related factors. The purpose of this study was to identify cancer screening rates and relevant factors among manufacturing workers. Methods: Using a questionnaire, data were collected from 335 workers aged over 40 years recruited from seven manufacturing companies. The collected information included cancer screenings (stomach, colorectal, breast, and cervical), attitude towards cancer screening, and demographic and job characteristics. Results: 72.5% of workers received stomach cancer screening (SCS), and 43% received colorectal cancer screening (CRCS). Among 86 women, 68.6% received breast cancer screening and cervical cancer screening. The attitude towards cancer screening was $29.5{\pm}3.78$. Workers aged over 51, married, and those working in mobile manufacturing were more likely to have undergone SCS. Workers aged over 51, married, those working in mobile manufacturing, those in workplaces with more than 1,001 employees, and those with more positive attitudes toward cancer screening were more likely to have undergone CRCS. Finally, attitude affected cervical cancer screening. Conclusion: Workers in small-sized workplaces had lower cancer screening rates. Thus, follow-up research should assess the health environment of workplaces and develop educational programs on cancer screening that reflect attitudes towards screening.

• Proceedings of the Korea Contents Association Conference
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• 2017.05a
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• pp.103-104
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• 2017

Objectives: The manufacturing industry was the one with the most repeated occurrence industrial disasters, and it is important to study the safety environment known by workers in the industry in order to prevent industrial accidents. Methods: Research objects were 1,123 male among members of employees who responded to 2015 PSWCI panel report. Research objects underwent affected subjective health and then categorized subjects into some groups according to changes in employment condition during one year. Statistical analyses were performed using the SAS version 9.4 (SAS Institute Inc., Cary, NC, USA). Results: According to results of analysis, manufacturing industry had differences in economic activity and health conditions based on employees conditions. Dynamic change aspects of manufacturing industry condition had differences between sex and cases where going back and forth between temporary condition and unemployment status had higher percentage in male. Conclusions: The results of this study may serve as the refer to taking a bill to improve the level of safety of the work environment felt by employees in the manufacturing industry.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.3
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• pp.310-321
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• 2019

Objectives: The purpose of this study was to investigate types and characteristics of chemical substances used in LCD(Liquid crystal display) panel manufacturing process. Methods: The LCD panel manufacturing process is divided into the fabrication(fab) process and module process. The use of chemical substances by process was investigated at four fab processes and two module processes at two domestic TFT-LCD(Thin film transistor-Liquid crystal display) panel manufacturing sites. Results: LCD panels are manufactured through various unit processes such as sputtering, chemical vapor deposition(CVD), etching, and photolithography, and a range of chemicals are used in each process. Metal target materials including copper, aluminum, and indium tin oxide are used in the sputtering process, and gaseous materials such as phosphine, silane, and chlorine are used in CVD and dry etching processes. Inorganic acids such as hydrofluoric acid, nitric acid and sulfuric acid are used in wet etching process, and photoresist and developer are used in photolithography process. Chemical substances for the alignment of liquid crystal, such as polyimides, liquid crystals, and sealants are used in a liquid crystal process. Adhesives and hardeners for adhesion of driver IC and printed circuit board(PCB) to the LCD panel are used in the module process. Conclusions: LCD panels are produced through dozens of unit processes using various types of chemical substances in clean room facilities. Hazardous substances such as organic solvents, reactive gases, irritants, and toxic substances are used in the manufacturing processes, but periodic workplace monitoring applies only to certain chemical substances by law. Therefore, efforts should be made to minimize worker exposure to chemical substances used in LCD panel manufacturing process.

• Journal of Korea Technology Innovation Society
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• v.22 no.3
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• pp.283-306
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• 2019

This study empirically analyzes the effects of non-technical innovation activities on employment growth. The study estimates the effects of organizational innovation and marketing innovation on employment growth using the data on manufacturing and service firms from the 2016 Korea Innovation Survey. The estimation results suggest that the detailed types of organizational innovation and marketing innovation have different effects on employment growth. In the case of organizational innovation, changes in business practices and changes in workplace organization do not have any significant impact on employment growth in both manufacturing and service firms. On the other hand, new external relationships have a positive employment effect in the manufacturing firms. Marketing innovations such as new methods in product placement and product promotion also have an effect of increasing employment in the manufacturing sector. However, the study finds that marketing innovation does not have any positive employment effect in the service firms.

• Design & Manufacturing
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• v.15 no.1
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• pp.48-56
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• 2021

The quality of products produced by injection molding process is greatly influenced by the process variables set on the injection molding machine during manufacturing. It is very difficult to predict the quality of injection molded product considering the stochastic nature of manufacturing process, because the process variables complexly affect the quality of the injection molded product. In the present study we predicted the quality of injection molded product using Artificial Neural Network (ANN) method specifically from Multiple Input Single Output (MISO) and Multiple Input Multiple Output (MIMO) perspectives. In order to train the ANN model a systematic plan was prepared based on a combination of orthogonal sampling and random sampling methods to represent various and robust patterns with small number of experiments. According to the plan the injection molding experiments were conducted to generate data that was separated into training, validation and test data groups to optimize the parameters of the ANN model and evaluate predicting performance of 4 structures (MISO1-2, MIMO1-2). Based on the predicting performance test, it was confirmed that as the number of output variables were decreased, the predicting performance was improved. The results indicated that it is effective to use single output model when we need to predict the quality of injection molded product with high accuracy.

• Korean Journal of Construction Engineering and Management
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• v.23 no.1
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• pp.113-117
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• 2022

Additive manufacturing (AM, also known as 3D printing) technology is digitalized technology, making it easy to predict and manage quality and also, have design freedom ability. With these advantages, AM technology is applied to various industries. In particular, a method of manufacturing buildings and infrastructure with AM technology is being proposed to the construction industry. However, the application of AM technology is restricted due to problems such as insufficient history and quality of technology, lack of construction management methods, and certification of manufacturing products. Therefore, the manufacture of architectural products is implemented with indirect AM technology. In particular, it manufactures formwork using AM and injecting building materials to implement the architectural product. In this study, hybrid type material extrusion AM is used to manufacture large-sized formwork and implement building products. Moreover, we identify factors that can predict productivity and economic feasibility in the additive manufacturing process. As a result, design optimization results are proposed to reduce the production cost and time of architecture buildings.

• Journal of Preventive Medicine and Public Health
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• v.32 no.1
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• pp.17-29
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• 1999

Objectives. This study was carried out to analyze the hearingthreshold levels and relating factors of 1,048 workers with noiseinduced hearing loss$(D_1)$. Methods. We analyzed the hearing-threshold levels and relating factors of 1,048 workers with noise-induced hearing loss$(D_1)$ examined by the summary reports of specific health examination results of industries and personal reports of specific health examination results reported by 58 specific health examination institutes and 8 secondary pneumoconiosis examination institutes in 1996. Results. Among 1,048 workers at 510 workplaces, male workers were 1,009 (96.3%) and female workers were 39 (3.7%). The mean ages of workers initially exposed to noise and at present were 28.7 and 47.2, respectively. The duration of total exposure was 16.5 years. Average hearing-threshold levels analyzed by three-divided classification of the study subjects were 43.7dB(Lt) and 42.6dB(Rt). Those analyzed by six-divided classification were 50.5dB(Lt) and 48.6d8(Rt). Among workers with noise-induced shearing loss$(D_1)$, 16.3% was unilateral hearing loss and 84.6% was classified to compensation case. 8.8%(Rt) and 10.2%(Lt) of them were suspected to be conductive hearing loss by differences of air-bone hearing-threshold levels. Hearing-threshold levels of workers in manufacturing industry were significantly increased during the short exposure compared with the levels in mining industry. Among manufacturing industries, hearing-threshold levels of workers in trailer and other transportation equipment manufacturing industry were significantly increased. Age and duration of total noise exposure were not significantly related to the average hearing-threshold levels analyzed by three-divided classification. Hearing-threshold levels of female workers were significantly increased during the short exposure compared with those of male workers. Hearing-threshold levels of workers at the high risk group, ages of 20s, 30s and total exposure duration of less than 10 years, were not significantly increased compared with those of the other groups. However, they were exposed at young ages. The 3 leading industries of workers at high risk group were trailer and other transportation equipment manufacturing, automobile manufacturing and assemble-metal manufacturing industries. Conclusions. This study was the first nationwide analysis of the hearing-threshold levels and relating factors of workers with noise. induced hearing loss$(D_1)$. We found the differences of the real number by the statistics of the department of labour and the expected number of worker' s compensations for occupationally-induced hearing loss estimated by this study. According to the results of this study, we should carefully examine the methods to narrow this difference.

• Journal of the Korean Society of Safety
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• v.37 no.5
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• pp.42-55
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• 2022

In this study, an accident at an in-house maintenance subcontractor of a manufacturing company was analyzed using representative systemic analysis methods, and the results were compared to determine the socio-technical and organizational structure causal factors. Systemic accident analyses were performed using AcciMap, STAMP-CAST, and a method that utilizes work processing procedures. The causal factors derived from the three methods were classified according to HFACS classification criteria. AcciMap and STAMP-CAST analyses were able to derive legal problems and defects in organizational structure between the company and the subcontractors. The method that utilized the work processing procedures drew the most causal factors of the three methods but showed some limitations in deriving legal and facility-related problems. Most of the causal factors identified through the systemic methods could be classified according to the HFACS classification criteria, except for the legal and organizational structure matters. Socio-technical and organizational problems with a holistic perspective of the company and subcontractors could be found using systemic analysis methods. However, it is necessary to conduct analysis using various methods in order to derive more comprehensive measures to prevent accidents because each analysis method showed some limitations in the derivation or expression of some causal factors. The results of this study can be helpful in selecting and using an appropriate method for accident analysis.