• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.94-103
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• 2020

This study investigated the effects of ultrasonic nanocrystal surface modification (UNSM) on the deteriorated surface of AISI SUS316L additively manufactured (AM) using the powder bed fusion (PBF) technique. Specifically, the effects of UNSM conditions on surface topology, hardness, and anti-corrosion were examined. Before UNSM treatment, the stainless steel 316L powder was processed via the PBF machine to prepare a substrate. We observed surface changes due to UNSM treatments in PBF SUS316L substrates and examined the correlation between topology changes, roughness, hardness, and anti-corrosion. After UNSM treatment, the coarse as-built surface was refined, and a regular micro-profile was implemented. Compared to the non-treated PBF sample, the waviness and roughness of the surfaces after UNSM treatment decreased by up to 56.0% and 94.5%, respectively, and decreased further as the interval decreased. The hardness improved by up to 63.0% at a maximum depth of 500 ㎛ from top surface by the UNSM treatment. The results of the corrosion test showed that the corrosion resistance of the UNSM specimens was moderately improved compared to that of the untreated surface. This study confirmed that UNSM is an effective post-processing technique for additively manufactured parts.

• Design & Manufacturing
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• v.8 no.2
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• pp.23-29
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• 2014

Salt bath heat treatment is usually used but recently vacuum heat treatment is increased for the heat treatment of hot work die steels. The differences in two heat treatment processes were compared by testing the mechanical properties of heat treated products. With two different features of processes, mechanical properties such as hardness, tensile strength and impact strength of products show very different results. In this study salt bath heat treated products showed higher tensile strength and impact strength than vacuum heat treated products but hardness was not much different. These lower mechanical properties of vacuum heat treated products are due to differences in heating and quenching process.

• The Journal of the Korean dental association
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• v.58 no.10
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• pp.640-648
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• 2020

The aim of this article is to provide major announcements within the last decade or so about possible medical emergencies in dentistry. This would be helpful to improve the knowledge on first aid suitable for dental environment. Syncope was the most common medical emergencies in dentistry. Medical emergency situations can be divided into urgency and true emergency. Urgency situations can be solved well if proper treatment is taken. However, even in an urgency, if the correct treatment is not performed, it may soon turn into an emergency. With the joint efforts of the Korean Dental Anesthesiology Society and the Korean Cardiopulmonary Resuscitation Association, dental advanced life support (DALS) has been prepared since 2015. Through 17 training experiences until January 2020, scenarios and textbooks were developed. Dentists and dental care teams need to be prepared to strengthen their competence as professionals and to increase their team-level response capabilities..

• Fibers and Polymers
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• v.4 no.2
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• pp.84-88
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• 2003

The properties of a woven fabric made of poly(trimethylene terephthalate) (PTT) were investigated. The PTT fab-ric of draw textured yarn (DTY) showed excellent stretch as good as a fabric containing spandex. However, the unique stretch of the PTT fabric reduced dramatically by simple heat-treatment even at as low as $80^{\circ}C$. To understand the phenomenon, the crimp rigidity of the DTY was observed by SEM. It was found that the drastic reduction of stretch was caused by irreversible uncrimping of PTT DTY after heat-treatment. Conclusively, it is of importance to optimize the texturing conditions for PTT DTY to make the crimp more stable.

• Membrane Journal
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• v.27 no.5
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• pp.375-388
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• 2017

Wastewater treatment (WWT) technology has been developing from simple pollutant treatment to energy and resource-saving advanced technology, and various technologies combined with IT and BT are developed to minimize the amount of pollutant and toxic substance discharge to the public water areas and to improve operational efficiency. To examine the development trend of domestic wastewater treatment technology, the registered patent technologies were surveyed, classified and analyzed by year and sector. This paper considers the status of patent registration related to WWT from 2010.1 to 2017.5 in terms of the number of specific technical areas, and the trends are analyzed based on the 10 categorization field such as biological and physicochemical treatment process, equipment and device, material, sludge treatment, membrane, process control and 42 specific technical areas. A total of 3,356 patents have been registered since 2010, and the number of patents has been decreasing since the peak at 2013 and maintains 3~400 per year. The total number of patents has not yet been less than other countries, but the number of patents of more advanced technologies, which can lead the global market, such as process monitoring, new concept processing and equipment technologies is still insufficient compared to developed countries.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.16
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• pp.7309-7313
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• 2015

Background: The organ preservation approach of choice for the treatment of locally advanced head and neck cancers is concurrent chemoradiation with three weekly high doses of cisplatin. Although this is an efficacious treatment policy, it has high acute systemic and mucosal toxicities, which lead to frequent treatment breaks and increased overall treatment time. Hence, the current study was undertaken to evaluate the efficacy of concurrent chemoradiation using 40 mg/m2 weekly cisplatin. Materials and Methods: This is a single institutional retrospective study including the data of 266 locally advanced head and neck cancer patients who were treated with concurrent chemoradiation using 40 mg/m2 weekly cisplatin from January 2012 to January 2014. A p-value of < 0.05 was taken to be significant statistically for all purposes in the study. Results: The mean age of the study patients was 48.8 years. Some 36.1% of the patients had oral cavity primary tumors. The mean overall treatment time was 57.2 days. With a mean follow up of 15.2 months for all study patients and 17.5 months for survivors, 3 year local control, locoregional control and disease free survival were seen in 62.8%, 42.8% and 42.1% of the study patients. Primary tumor site, nodal stage of disease, AJCC stage of the disease and number of cycles of weekly cisplatin demonstrated statistically significant correlations with 3 year local control, locoregional control and disease free survival. Conclusions: Concurrent chemoradiotherapy with moderate dose weekly cisplatin is an efficacious treatment regime for locally advanced head and neck cancers with tolerable toxicity which can be used in developing countries with limited resources.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.4055-4068
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• 2010

In this study, validity of wastewater treatment system with advanced treatment processes was evaluated by studying its operational conditions by applying the advanced treatment to the wastewater treatment system which was operating for last several years. Study indicated a fair result for the removal efficiencies of BOD, T-P, and T-N for each unit operation. BOD removal efficiencies for primary clarifier, bioreactor, final effluent are 35, 87, and 48 % respectively. T-P(T-N) removal efficiencies for primary clarifier, bioreactor, final effluent are 18(23), 40(38), and 25(25) % respectively. Further investigation of bioreactor showed that various microorganism such as bacteria, protozoa, and metazoa is present in the bioreactor, and the main function of the media, adhesion (adsorption) of microorganism onto the media, is stabilized. Final effluent quality was lower than the regulation, and BOD, COD, SS, T-N, T-P were 5.5, 9.9, 4.6, 11.8, 0.99 mg/L respectively.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.10-19
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• 2008

To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

• 한국초전도학회:학술대회논문집
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• 2007.07a
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• pp.73-73
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• 2007

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.90-95
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• 2008

We studied the effect of thermal annealing and hydrofluoric (HF) acid treatment on the field emission properties of carbon nanotube field emitter arrays (CNT-FEAs) grown with the resist-assisted patterning (RAP) process. After thermal and HF treatment, it was observed that the electron emission properties were remarkably improved. The enhanced electron emission was also found to depend strongly on the sequence of the treatments; the electronemission current density is 656 $mA/cm^2$ with the process of thermal treatment prior to HF treatment while the current density is reduced by 426 $mA/cm^2$ with the reversal processes. This is due to the increased crystalline structure by thermal annealing and then strong fluorine bond was formed by HF treatment.