• Tribology and Lubricants
• /
• v.34 no.2
• /
• pp.60-66
• /
• 2018

Graphene is a monolayer of carbon atoms (approximately 0.34 nm), arranged in a honeycomb network. It has been hailed as a next-generation flexible and transparent material because it has high electrical and thermal conductivities, excellent mechanical properties, as well as flexible and transparent properties. The wettability of graphene alters its adhesion or surface energy, and it is therefore an important parameter influencing its application in the fabrication of next-generation flexible and transparent electronics. Studies on the wettability of graphene are numerous and various opinions exist. However, almost all of these studies use the wet transfer method to transfer the graphene. In this study, therefore, we investigated the effect of wet and dry transfer methods on water contact angles of graphene on a substrate. The contact angles of substrates vary depending on the type of substrate. It was found that after graphene is transferred to the substrate, regardless of transfer method, the graphene/substrate contact angle increases to a value. The contact angle of graphene transferred using the dry transfer method is higher than the contact angle of graphene transferred using wet transfer methods. The wet transferred graphene is affected by the poly(methyl methacrylate) (PMMA) residue and the polar surface of substrate. The dry transferred graphene is influenced by the conformal contact between graphene and substrate.

• Journal of Korean Society on Water Environment
• /
• v.21 no.1
• /
• pp.59-65
• /
• 2005

A phosphate recovery system from artificial wastewater was developed using a completely mixed phosphorus crystallization reactor, in which powdered converter slag was used as a seeding crystal. In preliminary test, the optimal pH range for meta-stable hydroxyapatite crystallization for high phosphorus concentration was observed to be 6.0 to 7.0, which was different from the conventionally known pH range (8.0~9.5) for effective crystallization in relatively low phosphorus concentration less than 5 mg/L. The average phosphorus removal efficiency in a lab-scaled completely mixed crystallization system for artificial wastewater with about 100 mg/L of average $PO_4-P$ concentration was shown to be 60.9% for 40 days of lapsed time. XRD analysis exhibited that crystalline of hydroxyapatite formed on the surface of seed crystal, which was also observed in SEM analysis. In EDS mapping analysis, composition mole ratio (=Ca/P) of the crystalline was found to be 1.78, indicating the crystalline on the surface of seed crystal is likely to be hydroxyapatite. Particle size distribution analysis showed that average size of seed crystal increased from $28{\mu}m$ up to $50{\mu}m$, suggesting that phosphorus recycling from wastewater with high phosphorus concentration can be successfully obtained by using the phosphorus crystallization recovery system.

• Journal of the Korean Wood Science and Technology
• /
• v.33 no.6 s.134
• /
• pp.71-78
• /
• 2005

For the utilization of chestnut inner bark as forest biomass, this studies have been carried out cleary investigated about phenolic compounds from the diethyl ether solubles and ethyl acetate solubles of hot water extract from chestnut inner bark. 3 compound were isolated and their structures were identified by spectroscopic methods. They were known compounds, 3,5-dihydroxybenzoic acid, 3,4,5-trihydrixybenzoic acid and catechin. Electron donating ability (EDA) of 3 compounds were investigated. Gallic acid and catechin were found to higher EDA than control, ascorbic acid and $\alpha$-tocopherol in 10 ppm, and especially gallic acid has very higher EDA, 21 times than ascorbic acid. This gallic acid of chemical structure were substituted with free phenolic hydroxyl groups at meta and para position. It was supposed that phenolic hydroxyl groups in chemical structure was a EDA factor.

• Journal of Advanced Navigation Technology
• /
• v.16 no.5
• /
• pp.773-780
• /
• 2012

ZOR(zeroth order resonance) antenna for 2.45GHz WLAN(wireless local area network) is designed by use of CRLH-TL(composite right left handed transmission line) meta-material. The electrical length of conventional antennas is determined generally according to the resonant frequency, whereas that of ZOR antenna can be determined without reference to the resonant frequency. Therefore ZOR antenna has advantage in miniaturization of antenna in comparison with conventional antennas. In order to design such ZOR antenna, first unit cell with electrical length shorter than a quarter wavelength at 2.45GHz is designed to the some characteristics of homogeneous medium. In order to decrease resonant frequency and enhance frequency bandwidth, the proposed antenna is fed by CPW(co-planar waveguide) and short stub between radiation patch and ground plane is used for obtaining both higher inductance and smaller capacitance than previous mush-room type of CRLH-TL.

• Steel and Composite Structures
• /
• v.34 no.4
• /
• pp.467-485
• /
• 2020

Genetic Algorithm (GA) is a meta-heuristic algorithm which is capable of providing robust solutions for optimal design of structural components, particularly those one needs considering many design requirements. Hence, it has been successfully used by engineers in the typology optimization of structural members. As a novel approach, this study employs GA in order for conducting a case study with high constraints on the optimum mechanical properties of reinforced concrete (RC) beams under different load combinations. Accordingly, unified optimum sections through a computer program are adopted to solve the continuous beams problem. Genetic Algorithms proved in finding the optimum resolution smoothly and flawlessly particularly in case of handling many complicated constraints like a continuous beam subjected to different loads as moments shear - torsion regarding the curbs of design codes.

• Restorative Dentistry and Endodontics
• /
• v.26 no.2
• /
• pp.111-120
• /
• 2001

Calcium hydroxide pastes is widely used in conventional endodontics. Along with the expanded clinical use of calcium hydroxide, literatures suggest mixing calcium hydroxide with other substance. Among added substances the vehicle plays the most importance role in the overall process because it is directly related with the velocity of ionic dissociation of $Ca^{2+}$ and OH ion. In this study, we evalutated and compared periapical tissue response and root resorption after canal was filled with mixture of saline and calcium hydroxide(Junsei Chemical Co.. Japan) as a aqueous vehicle, Metapaste(Meta Co., Korea) as a viscous vehicle paste, Vitapex(Neo Dental, Japan) as a oily vehicle paste and IRM(Caulk Dentsply, USA) in replantation of rat molar. A total of 31 maxillary first molars of Sprague-Dawley female rats, 30 days old were used. The upper 1st molar was extracted and the mesiobuccal canal was filled with mixture of saline and calcium hydroxide, Metapaste, Vitapex. IRM and then replanted. Rats were sacrificed 3 weeks after replantation. the maxillae were removed. section of 4 micron were cut and stained with hematoxylin-eosin, Apical tissue response were observed under light microscope. The results were as follows: 1. Saline mixing group and Metapaste group were significant different in fibrous capsule width compared to Vitapex group and IRM group(P<0.05). 2. Saline mixing group. Metapaste group. Vitapex group and IRM group did not prevent root resorption and there were no statistical difference. 3. In saline mixing group and Metapaste group. loss of pastes were observed in all samples. From the results of our study. we observed loss of pastes in saline mixing group and Metapaste group because of water soluble property and assumed it was related to inflammation in apical area and sealing ability of material. So, we should study and develop calcium hydroxide vehicle which is easily removed and more stable and because of only 3 weeks observation we need more evaluation in long period.

• The Journal of the Korea Contents Association
• /
• v.16 no.12
• /
• pp.181-191
• /
• 2016

We analyzed the search word of the media content in the IPTV service, and as a result we found that an important factor is general meta information as well as content(material, plot, etc.) and emotion information in the media content selection criteria of customers. Therefore, in this research, in order to efficiently provide various media contents of IPTV to users, we designed the emotion classification system for utilizing the emotion information of the media content. Next, we proposed 'personalized media contents curation system based on emotion information' for organizing the media contents, through the various processing steps. Finally, to demonstrate the effectiveness of this system, we conducted a user satisfaction survey(72.0 points). In addition, the results of comparing the results based on popularity and the results of the proposed system showed that the ratio leading to the actual users' viewing behavior was 10 times higher.

• Tuberculosis and Respiratory Diseases
• /
• v.69 no.2
• /
• pp.75-80
• /
• 2010

The year of 2009~2010 brought a number of concepts and new ideas were evaluated with promising results. However, some studies that challenged many beliefs. In acute respiratory distress syndrome (ARDS), recent clinical studies took into consideration of pathophysiologic changes of respiratory system compliance. Meta-analysis of positive end-expiratory pressure trials showed survival benefit of high positive end-expiratory pressure in ARDS. Until now, prone positioning did not show survival benefit in patients with ARDS. Extracorporeal membrane oxygenation (ECMO) based management improved survival in patients with severe ARDS. ECMO can be a management option in severe ARDS. Sedation is a standard practice in critically ill patients needing mechanical ventilation. However, Danish group reported less sedation of critically ill patients receiving mechanical ventilation was associated with an increase in days without ventilation. Although this single center study has some limitations, the overall results are promising. Use of maximal sterile barrier precautions (mask, sterile gown, sterile gloves, and large sterile drapes) with chlorhexidine-impregnated dressing reduced central venous catheter related infection. Selective oropharyngeal decontamination (application of topical antibiotics in the oropharynx) reduced the mortality rate of an intensive care unit (ICU) population. Normoglycemia in Intensive Care Evaluation and Survival Using Glucose Algorithm Regulation (NICE-SUGAR) trial reported intensive glucose control increased mortality among adults in the ICU. Some of the results of above papers are promising. However, some ideas may need for more frequent individual assessment and increase the workload of ICU staffs. Before implementation of new practice in ICU, we should take into consideration of individual hospital situation including human and material resources.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.9
• /
• pp.4171-4177
• /
• 2013

Outer tie rod is lighter than other, but there is the trend item weight and the number is increasing due to vehicle performance improvement. Thus, to improve vehicle fuel efficiency, weight lightening is essential. Therefore, this research performed the finite element analysis to investigate the structural performance of the outer tie rod for an electrical vehicle. This study was performed as the preliminary study for a lightweight design of the outer tie rod. The weight of outer tie rod was optimized by adopting the steel material and applying the trial and error method. The strengths due to durability and buckling should be considered in the structural design of an outer tie rod. Furthermore, the meta model-based optimization was applied to obtain its lightweight design, leading to 9 % weigh reduction.

• Advances in concrete construction
• /
• v.12 no.6
• /
• pp.479-490
• /
• 2021

Present research is mainly focused on, microstructural and durability analysis of Graphene Oxide (GO) in Wollastonite (WO) induced cement mortar with silica fume. The study was conducted by evaluating the mechanical properties (compressive and flexural strength), durability properties (water absorption, sorptivity and sulphate resistance) and microstructural analysis by SEM. Cement mortar mix prepared by replacing 10% ordinary portland cement with SF was considered as the control mix. Wollastonite replacement level varied from 0 to 20% by weight of cement. The optimum replacement of wollastonite was found to be 15% and this was followed by four sets of mortar specimens with varying substitution levels of cementitious material with GO at dosage rates of 0.1%, 0.2%, 0.3% and 0.4% by weight. The results indicated that the addition of up to 15%WO and 0.3% GO improves the hydration process and increase the compressive strength and flexural strength of the mortar due to the pore volume reduction, thereby strengthening the mortar mix. The resistance to water penetration and sulphate attack of mortar mixes were generally improved with the dosage of GO in presence of 15% Wollastonite and 10% silica fume content in the mortar mix. Furthermore, FE-SEM test results showed that the WO influences the lattice framework of the cement hydration products increasing the bonding between silica fume particles and cement. The optimum mix containing 0.3% GO with 15% WO replacement exhibited extensive C-S-H formation along with a uniform densified structure indicating that calcium meta-silicate has filled the pores.