• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.23-26
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• 2005

In this work, effects of oxygen plasma on surfc1ce characteristics of carbon fibers were investigated in impact strength of carbon fibers-reinforced composites. The surface properties of the carbon fibers were determined by acid/base values, FT-IR, and X-ray photoelectron spectroscopy (XPS). Also, the mechanical properties of the composites were studied by impact strength measurements. As experimental results, the $O_{IS}/C_{IS}$ ratio of the carbon fiber surfaces treated by oxygen plasma was increased compared to that of untreated ones, possibly due to development of oxygen-containing functional groups. The mechanical properties of the composites, including impact strength had been improved by the oxygen plasma on fibers. These results could be explained that the oxygen plasma resulted in the increase of the adhesion of between fibers and matrix in a composite system.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.639-646
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• 2019

Ink-jet printing is a manufacturing process technology that directly prints a digitalized design pattern onto a substrate using a fine ink jetting system. In this study, environmentally friendly yellow aqueous ceramic ink is synthesized by mixture of distilled water, yellow ceramic pigment and additives for ink-jet printing. The graft polymer, which combines electrostatic repulsion and steric hindrance mechanism, is used as a surfactant for dispersion stability of aqueous ceramic ink. Synthesized ceramic ink with graft polymer surfactant shows better dispersion stability than did ceramic ink with PAA surfactant; synthesized ink also shows desirable ink-jet printability with the formation of a single ink droplet during printability test. Finally, ceramic ink printed on glass substrate and ceramic ink with graft polymer surfactant shows a high contact angle without surface treatment on glass substrate. Consequently, it is confirmed that the ceramic ink with graft polymer surfactant can achieve high printing resolution without additional surface treatment process.

• Fashion & Textile Research Journal
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• v.18 no.4
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• pp.457-467
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• 2016

This study aimed to develop functional underwear for elderly women in their sixties in terms of good fit, wear comfort and body temperature regulation. To satisfy elderly women's physical and metabolical needs, an automatic temperature control system via PCM treatment was applied. Underwear pattern was produced by producing body surface replica, which was derived from 3D body parametric model. Differential ratios of outline length and area between 3D surface and 2D plane were 1.4% and 0.5%, respectively. The reduction rate was determined as 10% through the expert's evaluation. PCM treated fabric showed higher Q-max, meaning that it can facilitate the thermal transition in hot situation. Moreover, it also showed higher insulation to preserve heat and keep warm microclimate in a cold weather. Heat distribution measurements on various body parts revealed that the temperature after PCM treatment was significantly higher. The clothing pressure after 10% pattern reduction showed higher before reduction, at the same time, even lower than the comfort clothing pressure range of $5{\sim}10gf/cm^2$, implying that experimental garment of this research is acceptable in terms of clothing pressure. Evaluation results on the comfort to move in various motions proved that adequate clothing pressure improved the wear comfort in various motions.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.1
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• pp.1-7
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• 2003

In spite water direct seeding cultivation of rice has advantages in terms of laborsaving and cost-down, it demonstrates uneven seedling establishment and difficult weed management. To select an applicable mat for mulching system of water seeded rice, weed occurrence, growth and yield performances of rice, and soil temperature were evaluated in several kinds of biodegradable mulching material. Field studies were conducted at the experimental farm of National Crop Experiment Station in 1999 and 2000. Among the mats tested in 1999, Safer-mat had the greatest effect on inhibiting weed occurrence and Lawn-mat demonstrated the least efficacy of weed control (EWC) value. In Safer-mat treatment, Ludwigia prostrata was the dominant weed species but Echinochloa crus-galli was not observed. Different kinds of mulching material from the mats studied in 1999 were tested in 2000. Biodegradable polyester (PES) coated on the recycled paper for newspaper press (RP) treatments showed similar or higher EWC values than non-mulched broadcast seed rice with 2 times of herbicide application (BC-herbicide) and Safer-mat that was the most effective mat on preventing weed appearance in 1999. Immediately after mat mulching on the surface of paddy soil, five pregerminated rice seeds were manually sown in each 3cm-hole formerly punctured at 30${\times}$14 cm spacing in 2000. All the 3 kinds of mulching material tested in 2000 had better seedling stand than BC-herbicide treatment. Rice yield in PES coated with 10 thickness on RP (PES10 $\mu\textrm{m}$＋RP) was a little higher than in BC-herbicide treatment but the former produced less panicles in unit land area than the latter. PES10 $\mu\textrm{m}$＋RP demonstrated a great effect on raising soil surface temperature than non-mulching treatment throughout the period of seedling establishment.

• Restorative Dentistry and Endodontics
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• v.43 no.2
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• pp.16.1-16.9
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• 2018

Objectives: Understanding the reason for an unsuccessful non-surgical endodontic treatment outcome, as well as the complex anatomy of the root canal system, is very important. This study examined the cross-sectional root canal structure of mandibular first molars confirmed to have failed non-surgical root canal treatment using digital images obtained during intentional replantation surgery, as well as the causative factors of the failed conventional endodontic treatments. Materials and Methods: This study evaluated 115 mandibular first molars. Digital photographic images of the resected surface were taken at the apical 3 mm level and examined. The discolored dentin area around the root canal was investigated by measuring the total surface area, the treated areas as determined by the endodontic filling material, and the discolored dentin area. Results: Forty 2-rooted teeth showed discolored root dentin in both the mesial and distal roots. Compared to the original filled area, significant expansion of root dentin discoloration was observed. Moreover, the mesial roots were significantly more discolored than the distal roots. Of the 115 molars, 92 had 2 roots. Among the mesial roots of the 2-rooted teeth, 95.7% of the roots had 2 canals and 79.4% had partial/complete isthmuses and/or accessory canals. Conclusions: Dentin discoloration that was not visible on periapical radiographs and cone-beam computed tomography was frequently found in mandibular first molars that failed endodontic treatment. The complex anatomy of the mesial roots of the mandibular first molars is another reason for the failure of conventional endodontic treatment.

• Elastomers and Composites
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• v.40 no.1
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• pp.22-28
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• 2005

In this work, the effect of oxygen plasma treatment of nano-scaled silica on the mechanical interfacial properties and thermal stabilities of the silica/rubber composites was investigated. The surface properties of the silica were studied in X-ray photoelectron spectroscopy (XPS) and contact angles. And, their mechanical interfacial properties and thermal stabilities of the composites were characterized by tearing energy ($G_{IIIC}$) and thermogravimetric analysis (TGA), respectively. As a result, it was found that the introduction rate of oxygen-containing polar functional groups onto the silica surfaces was increased by increasing the plasma treatment time, resulting in improving the tearing energy. Also, the thermal stabilities of the composites were increased by increasing the treatment time. These results could be explained that the polar rubber, such as acrylonitrile butadiene rubber (NBR), showed relatively a high degree of interaction with oxygen-containing functional groups of the silica surfaces in a compounding system.

• Journal of Power System Engineering
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• v.16 no.6
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• pp.59-65
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• 2012

Torque Generator is a product which has function to transform hydraulic energy to mechanical energy of torque and rotating speed, and be used for direction change device of agricultural machines. This study proposes failure analysis and test analysis on torque generator and introduces a process that reliability of a product is enhanced by design improvement. And also it presents improvements of maximum output torque by modifying design and surface treatment. Lastly it verifies reliability improvement by analyzing test results of before and after life test.

• Journal of Korean society of Dental Hygiene
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• v.14 no.5
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• pp.609-615
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• 2014

Objectives : In most developed countries there has been a substantial decrease in the prevalence of dental caries in children of 12 years old over the past 40 years. This change in epidemiology highlights the importance of preventive management in dentistry. For successful management of early caries lesions, it is essential to detect and assess the pathological changes of dental caries. Therefore, the purpose of this study was to investigate the overview of International Caries Detection and Assessment System(ICDAS) criteria for the detection and assessment of early caries lesions by literature reviews. Methods : The author reviewed the MEDLINE search by the key words of 'caries assessment', 'caries detection', 'caries measurement', and 'ICDAS'. Results : This literature review provided an overview of International Caries Detection and Assessment System(ICDAS) criteria for the detection and assessment of early caries lesions. This article showed the principles, concept, and primary caries detection criteria of the ICDAS. The ICDAS can macroscopically measure the enamel surface changes and potential histological depth of caries lesions by the surface characteristics of the teeth. The ICDAS criteria allow researchers and clinicians to choose the stage of dental caries and characteristics for assessment. Conclusions : ICDAS can be an adjunct method to clinical decision making and preventive treatment planning.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.1-8
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• 2020

While dental clinics still use the ultrasonic scaling/surgery tool for teeth scaling and cleaning the tool's use is expanding steadily to include treatment of damaged teeth and bone tissue. In this study, a handpiece moving system (HMS) was developed to evaluate bone scaling and cutting in the field of dentistry. The HMS, through a scaling test of bone using a scaler tip, it was able to identify surface damage. Additionally, a thermos-graphic camera was used to observe the temperature distribution that occurred during the bone scaling and cutting process. Consequently, we found that increasing the working load increased the amount of surface damage. Changes in temperature distribution occurred slowly and were maintained within safety bounds for 10 minutes. Going forward, we will compare the HMS performance on scaling and cutting with other devices.

• Membrane and Water Treatment
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• v.12 no.1
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• pp.23-35
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• 2021

A POM-membrane was fabricated by immobilizing a keggin type polyoxometalate (POM) H5PV2Mo10O40 onto the surface of microporous flat-sheet polymeric polyvinylidene fluoride (PVFD) membrane using a chemical deposition method. The POM-membrane was characterized by FT-IR, SEM and EDX to confirm existing of the POM onto the membrane surface. The POM-membrane was used to remove an anionic textile dye (Reactive Black 5 named as an RB5) from aqueous phases with a cross-flow membrane filtration and a batch adsorption system. The dye removal efficiency of the POM-membrane using the cross-flow membrane filtration system and the batch adsorption system was about 88% and 98%, respectively. The influence factors such as contact time, adsorbent dosage, pH, and initial dye concentration were investigated to understand the adsorption mechanism of the RB5 dye onto the POM-membrane. To find the best fitting isotherm model, Langmuir, Freundlich, BET and Harkins-Jura isotherm models were used to analyze the experimental data. The isotherm analysis showed that the Langmuir isotherm model was found to the best fit for the adsorption data (R2 = 0.9982, qmax = 24.87 mg/g). Also, adsorption kinetic models showed the pseudo second order kinetic model was found the best model to fit the experimental data (R2 = 0.9989, q = 8.29 mg/g, C0 = 15 ppm). Moreover, after four times regeneration with HNO3 acid, the POM-membrane showed high regenerability without losing dye adsorption capacity.