• Journal of the Korean institute of surface engineering
• /
• v.56 no.6
• /
• pp.386-392
• /
• 2023

In this work, we describe the reduction kinetics of gold nanoparticles synthesized by plasma discharge in aqueous solutions with varied voltages and precursor (HAuCl₄) concentrations. The reduction rate of [AuCl₄]^- was determined by introducing NaBr to the gold colloidal solution synthesized by plasma discharge, serving as a catalyst in the reduction process. We observed that [AuCl₄]^- was completely reduced when its characteristic absorption peak at 380 nm disappeared, indicating the absence of [AuCl₄]^- for ligand exchange with NaBr. The reduction rate notably increased with the rise in discharge voltage, attributable to the intensified plasma generated by ionization and excitation, which in turn accelerated the reduction kinetics. Regarding precursor concentration, a lower concentration was found to retard the reduction reaction, significantly influencing the reduction kinetics due to the presence of active H⁺ and H radicals. Therefore, the production of strong plasma with high plasma density was observed to enhance the reduction kinetics, as evidenced by optical emission spectroscopy.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.50 no.3
• /
• pp.166-169
• /
• 2024

Ankylosis of the temporomandibular joint (TMJ) is a condition in which the mandibular condyle fuses with the mandibular fossa through fibrous or bone tissue. It is a debilitating pathology that interferes with chewing, speaking, and oral hygiene. Currently, alloplastic reconstruction is considered the gold standard for treating severely compromised TMJs, such as in ankylosis. The article describes a patient with a history of facial trauma, with bilateral ankylosis of the TMJs, inability to open his mouth, and poor dental condition. Due to a long period of immobilization of approximately 40 years, the initial treatment plan was to remove the ankylosis bilaterally and install customized PMMA (polymethylmethacrylate) spacers. The patient gained mouth opening and improved chewing quality with one year of customized spacer use prior to definitive alloplastic replacement with stock-type TMJ prostheses. Customized joint spacers are a provisional treatment option when definitive alloplastic reconstruction is not indicated. Spacers provide the patient with progressive jaw function and mobility gains.

• Progress in Superconductivity and Cryogenics
• /
• v.26 no.2
• /
• pp.19-23
• /
• 2024

3D printing has the advantage of being able to process various types of parts by layering materials. In addition to these advantages, 3D printing technology allows models to be processed quickly without any special work that can be used in different fields to produce workpieces for various purposes and shapes. This paper deals to not only increase the utilization of 3D printing technology, but also to revitalize 3D printing technology in applications that require similar cryogenic environments. The goal of this study is to identify the mechanical properties of polylactic acid and photopolymer resin processed by Fused Deposition Modeling (FDM) and Digital Light Processing (DLP) respectively. The entire process is meticulously examined, starting from getting the thermal contraction using an extensometer. A uniaxial tensile test is employed, which enables to obtain the mechanical properties of the samples at both room temperature (RT) and cryogenic temperature of 77 K. As the results, photopolymer resin exhibited higher tensile properties than polylactic acid at RT. However, at cryogenic temperatures (77 K), the photopolymer resin became brittle and failure occurred due to thermal contraction, while polylactic acid demonstrated superior tensile properties. Therefore, polylactic acid is more suitable for lower temperatures.

• Transactions of Materials Processing
• /
• v.33 no.4
• /
• pp.241-247
• /
• 2024

The triply periodic minimum surface (TPMS) shape with a complex geometry can easily manufactured from additive manufacturing processes. The TPMS shape has a high surface-to-volume ratio. In addition, the TPMS shape increases the possibility of the self-circulation when the fluid flows inside the TPMS structure. Due to these reason, the performance of the fluid flow filter can be greatly improved when the TPMS structure is applied to the filter. The aim of this paper is to investigate the influence of the design of the unit cell for TPMS on self-circulation characteristics of air using computational fluid dynamics (CFD). From the results of the CFD, the effects of the shape and the dimension of the unit cell for TPMS on the self-circulation pattern and the pressure difference are examined. Finally, a proper design of the TPMS is discussed from the viewpoint of self-circulation of air.

• Journal of the East Asian Society of Dietary Life
• /
• v.18 no.5
• /
• pp.692-701
• /
• 2008

This study was conducted with 150 adults of 20 years or older, all of whom lived in Seoul. The awareness of traditional Hangwa (Korean cookies) was shown to be relatively low, with 2.9 points on average, and the intake of traditional Hangwa for a month was 2.1 times. For the reason that traditional Hangwa couldn't become popular, and the opinion that the reason was because the price is expensive was the highest, at 3.8. The next highest reasons given were because it is difficult to buy, and because it is inconvenient to eat, at 3.0. The traditional Hangwa was shown to enjoy positive awareness as opposed to negative awareness, while the manufacturing sanitation was also recognized to be relatively clean, with 2.6 points assigned to the opinion that it doesn't taste good, and 2.7 points assigned to the opinion that the manufacturing sanitation is unclean. With regard to the excellence of traditional Hangwa, the response that 'our tradition can be handed down' was the most often encountered, with a score of 3.9. The traditional Hangwa was appraised as excellent, with 3.6 points assigned to the opinion 'it suits our body because it is made with our agricultural products' and 3.4% for each opinion 'safe ingredients are used' and 'all ingredients are good for health'. With regard to the level of agreement for the development of functional traditional Hangwa, the positive group was higher than 25.3% of the negative group, with 27.3% for 'agree very much' and 22.0% for 'agree'. When converted into a 5-point scale for the development of functional traditional Hangwa, the group that was positive toward its development was high, with 3.4 points on average. All categories of excellence awareness were correlated with the level of agreement for the development of a functional food product (p<0.001). Consumer awareness toward the addition of traditional Hangwa functionality was generally positive, with 3.3 points or higher on average, and awareness of the aging suppression and diabetes control effects of Hangwa was also high, with 3.5 points. Next were Hangwa for diet, Hangwa for blood pressure control, Hangwa for mineral supple-mentation and vitamin additive-type Hangwa, with 3.4 for each, and Hangwa for health preservation, with 3.3 in order. With regard to the degree of interest toward functional traditional Hangwa for the treatment of diseases, obese patients cited aging suppression, at 3.2, and vitamin additive Hangwa, at 3.0, while Hangwa for dieting was assigned 2.8 points. Patients with high blood pressure, blood circulation, and diabetes were all shown as having a high degree of interest in all items, while evidencing particular interest toward Hangwa for diabetes control and Hangwa for blood pressure control. With regard to intention to purchase while developing functional traditional Hangwa, the group asserting intention to purchase was higher than 60% for all items except for Hangwa for diabetes control (58.7%). The Hangwa for aging suppression was highest, at 68.6%, and shown as having intention to purchase during development in the order of vitamin additive Hangwa at 68.0%, Hangwa for mineral supplementation at 64.6%, each of Hangwa for health preservation and Hangwa for blood pressure control at 62.7%, Hangwa for diet at 62.6% and Hangwa for diabetes control at 58.7%. The considerations during the development of functional traditional Hangwa were in the following order: storage at 4.1 points, taste and level of function at 3.9 points, size at 3.5 points, and packing at 3.4 points.

• Journal of Food Hygiene and Safety
• /
• v.23 no.2
• /
• pp.98-107
• /
• 2008

The ozone has the oxidizing power which is powerful the fluorine and the antimicrobial spectrum of wide scope. Researches were carried out to use the merits that ozone has in various fields including the food industry, and many studies are also conducted nowadays for more efficient use of ozone. The ozone was permitted legally as a food additive and was practically used in the United States, Australia, Japanese etc. In November 2007, ozone water was permitted as a food additive in Korea and the interest in the use of ozone water has been on the rise in the Korea's food industry. As a olisinfectant method, ozone has many advantages. The maintenance and management expenses of ozone are lower than the installation cost at early stages and no by-products are generated after use it compared to others. Recently the demand of ozone as a olisinfectant method is increasing drastically. Although ozone water is popularly used to sterilize raw foods like fruits, vegetables and meats, the cases are still limited and were verified by the survey results. However, the use of ozone water is gradually being increased and is focused on food services. Ozone water refers to a state where ozone is dissolved into water to more conveniently use ozone. Accordingly, ozone water should be managed in regards with the amount and time of water-dissolved ozone, and the control of discharged ozone concentration is required for safe use of ozone water. The items to control mentioned above are directly related to the performance of the devices, and therefore, it is required to newly establish the performance criteria of ozone water manufacturing devices.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.33 no.4
• /
• pp.260-268
• /
• 2017

Purpose: Manufacturing with AM (Additive manufacturing) technique has many advantages; but, due to insufficient study in the area, it is not being widely used in the general clinic. In this study, differences of flexural strength among various materials of 3 unit fixed dental prosthesis were analyzed. Materials and Methods: A metal jig for specimens that had a 3-unit-fixed dental prosthesis figure were fabricated. The jigs were made appropriately to the specifications of the specimens. Three different kinds of materials of specimens which were NC (mathacrylic esther based), DP-1 (Bisphenol A epoxy acrylate type oligomer based), and DT-1 (urethane acrylate based) were printed with DLP machine. Five specimens for each kind of material were printed with an angle of $30^{\circ}$ from the horizontal surface. The specimens were placed on the jig and the flexural strength was measured and recorded using Universal testing machine. The recorded data was analyzed in SPSS using One-way ANOVA and Tukey HSD to determine the significance of the differences of flexural strength among the groups. Results: The flexural strengths of each group were the followings: NC, $1119{\pm}305$ N; DP-1, $619{\pm}150$ N; DT-1, $413{\pm}65N$. Using One-way ANOVA and Tukey Honestly Significant Difference test, significant difference was found between NC and the other groups (P < 0.05), but there was no significant difference between DP-1 and DT-1 (P > 0.05). Conclusion: Higher flexural strength was shown in 3-unit-fixed dental prosthesis that were 3D printed using a DLP machine with NC material.

• Journal of Intelligence and Information Systems
• /
• v.11 no.1
• /
• pp.35-51
• /
• 2005

The wide spread of Internet and rapid development of e-commerce-related technology have brought sweeping changes on the traditional commercial transactions. Accordingly, many efforts to transform these transactions electronically under e-commerce environment have been carried out. As most transactions are usually made through negotiations, the function of automated negotiation is also required in the e-commerce environment. This paper aims to develop the method to generate and evaluate the multi-attribute negotiation proposals for automated negotiation systems. To this end the related articles are reviewed and the method dealing with e-negotiation strategy is suggested. In this method, the seller generates his or her own negotiation proposal and then evaluates the buyer's proposal based on SAW (Simple Additive Weighting Method), one of the MADM (Multi Attribute Decision Making) methods. To verify the suggested method, a case study is conducted in the order-based manufacturing environment.

• Applied Chemistry for Engineering
• /
• v.24 no.5
• /
• pp.499-506
• /
• 2013

As the usuage of tempered glass for touch panel increased rapidly with the development of industry, the amount of UV curable coating solution used to protect glass surfaces during a tempered glass manufacturing process increased as well. The UV curable coating has advantages compared to thermal curing such as shortened curing time and non-solvent. Appropriated polymer and monomer were used as an acid polymer to grant an alkali peeling ability. The monomers were 2-hydroxyl methylacrylate, 1,6-hexanediol diacrylate and dipentaerythritol hexaacrylate which have acryl groups of 1, 2, and 6, respectively. The combination of three different types of photoinhibitors were used and bisphenol A epoxy diacrylate was used as an oligomer. In this study, experiments were carried out by controlling the amount of photoinitiator, oligomer, and additive while maintaining the constant content of the acid polymer and the acrylic monomer. The changes in physical properties according to the additive content were investigated. It was found that the combination of photoinitiators was necessary to achieve the hardness above 4H and it was possible to control the delamination type of the coating film from a sheet to pieces by the addition of TPO as an initiator. The increase in oligomer contents increased the hardness and adhesiveness alongside dissection time. Talc content of 20 wt% showed the best results.

• Membrane Journal
• /
• v.24 no.6
• /
• pp.463-471
• /
• 2014

While poly(styrene)-based anion exchange membranes have the advantage like easy and simple manufacturing process, they also possess the disadvantage of poor durability due to their brittleness. Acrylonitrile-butadiene rubber was used here as an additive to make the membranes have improved flexibility and durability. For the preparation of the anion exchange membranes, a PP mesh substrate was immersed into monomer solutions with vinylbenzyl chloride, styrene, divinylbenzene and benzoyl peroxide, then thermally polymerized & crosslinked. The prepared membranes were subsequently post-aminated using trimethylamine to result in $-N+(CH_3)_3$ group-containing composite membranes. Various contents of vinylbenzyl chloride and acrylonitrile-butadiene rubber were investigated to optimize the membrane properties and the prepared membranes were evaluated in terms of water content, ion exchange capacity and electric resistance. It was found that the optimized composite membranes showed higher IEC and lower electric resistance than a commercial anion exchange membrane(AMX) and have excellent flexibility and durability.