• Journal of the Korean Wood Science and Technology
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• v.49 no.3
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• pp.226-233
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• 2021

This article aimed at thermally treating and charactering the Eucalyptus grandis wood under three different temperatures. For this, pristine eucalypt samples were treated by heating in a laboratory oven at 160 ℃, 200 ℃ and 240 ℃, always for 2 h. Treatment parameters (based on weight percentage loss and specific gravity), as well as mechanical (by hardness tests), chemical (by infrared spectroscopy), thermal (by thermogravimetry), and colorimetric (by CIELab method) features were evaluated. Compared to the pristine ones, the treated woods have there was a drop in apparent density at 12 % and consecutively greater thermal stability which is probably related to a previous partial degradation of some major amorphous components (namely cellulose, hemicellulose and lignin), as suggested by the treatment parameters and infrared spectra. Besides of that, the higher the temperature treatment, the higher the loss in surface hardness and the higher the colour darkening.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.402-406
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• 2013

In this study, a pitch for melt-electrospinning was prepared from naphtha cracking bottom (NCB) oil by the modification with heat treatment. The softening point and property of the modified pitch was influenced by modification conditions such as nitrogen flow rate, heat treatment temperature, and reaction time. Among these, the heat treatment temperature had a very strong influence on the distribution of molecular weight and softening point of the pitch. The C/H mole ratio and average molecular weight increased with increasing the heat treatment temperature due the decomposition and cyclization reaction of surface-functional groups. In addition, the values of benzene insoluble and quinoline insoluble also tends to decrease, and the width of molecular weight distribution seems to get more narrow. The carbon fiber with a diameter of $4.8{\mu}m$ was prepared from a modified pitch at the softening point of $155^{\circ}C$ by melt-electrospinning. It is believed that the melt-electro spinning method is much more convenient to get the thinner fiber than the conventional melt spinning method.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.12
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• pp.835-839
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• 2012

In recent decades, a lot of noise barriers have been installed along paved road in order to reduce the road induced noise, which increases as traffic volume grows. For better range of sight, transparent noise barriers are widely installed despite of reflecting noise. In this study, the effect of surface shape and pattern of noise barriers on the reduction of reflecting noise was analyzed to maximize the noise reduction. According to the number of shape and pattern, it was observed that there were noise reduction effect as of 0.9~1.5 dB(A). It was found that the spatial field where the noise concentrates or disperses changes according to the width of blocks on the barriers as well. It suggests that there might be possibility of surface shape modification to optimize the noise reduction technology.

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.141-148
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• 2012

In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hydrophobic silica aerogel. The surface modification of silica aerogel was performed to obtain UV curable urethane acrylate hybrid coating sols with good compatibility by using surfactant(Brij 56). The polycarbonate substrates were coated by the prepared composites and cured under UV radiation. The incorporation of aerogel with only 10 vol% of content resulted in remarkable improvement by about 28% in the thermal insulation property of the coated film, as compared with substrate. In addition, increasing aerogel content was found to give minor effect on the variation of optical transparency, adhesion, and surface hardness of the coated film.

• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.51-59
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• 2007

A polyelectrolyte chain confined in a slit nanochannel exhibits a structural transition from the one in free space. In this paper, the effect of the long-range electrostatic interactions between the xanthan polyelectrolyte and the slit wall on the confined xanthan conformation is investigated via the Brownian dynamics simulation. A neutral and two negatively charged surfaces of polydimethylsiloxane (PDMS) and glass are combined to make four kinds of slit channels with different charge characteristics: i) neutral-neutral, ii) glass-glass, iii) neutral-PDMS and iv) neutral-glass walls. Their walls are characterized by uniform surface charge densities determined from experimental data of zeta potential. Both the nonmonotonic chain size variation and the loss of long-range bond vector correlation, previously observed under confinement in the PDMS-PDMS slit, are also found in the neutral slit, demonstrating the nonelectrostatic origin of such crossover behaviors. As expected, the effect of wall charges is negligible at sufficiently high medium ionic strength of 100mM but it becomes significant in the opposite limit of 0.01mM. In the latter case, the high charge density of glass walls strengthens the effective confinement of a negatively charged polyelectrolyte and produces a xanthan structure comparable to that confined in a much narrower neutral slit. The obtained structural data suggest the possibility of controlling the structure of confined polyelectrolytes by the modification of surface charge characteristics of micro/nanofluidic devices in combination with the adjustment of the medium ionic strength.

• Macromolecular Research
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• v.14 no.5
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• pp.565-572
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• 2006

Recombinant human bone morphogenic protein-2 (rhBMP-2), which is known as one of the major local stimuli for osteogenic differentiation, was immobilized on the surface of hyaluronic acid (HA)-modified poly$(\varepsilon-caprolactone)$ (PCL) (HA-PCL) scaffolds to improve the attachment, proliferation, and differentiation of human bone marrow stem cells (hBMSCs) for bone tissue engineering. The rhBMP-2 proteins were directly immobilized onto the HA-modified PCL scaffolds by the chemical grafting the amine groups of proteins to carboxylic acid groups of HA. The amount of covalently bounded rhBMP-2 was measured to 1.6 pg/mg (rhBMP/HA-PCL scaffold) by using a sandwich enzyme-linked immunosorbant assay. The rhBMP-2 immobilized HA-modified-PCL scaffold exhibited the good colonization, by the newly differentiated osteoblasts, with a statistically significant increase of the rhBMP-2 release and alkaline phosphatase activity as compared with the control groups both PCL and HA-PCL scaffolds. We also found enhanced mineralization and elevated osteocalcin detection for the rhBMP-2 immobilized HA-PCL scaffolds, in vitro.

• Journal of the Korean Wood Science and Technology
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• v.48 no.1
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• pp.32-40
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• 2020

While the utilization of wood as a raw material in related industries has been increasing with the population increasing, the availability of wood from natural forests has continued to decline. An alternative to this situation is the manufacture of particleboard from non-wood lignocellulose materials through the modification of sandwich particleboard (SPb) using bamboo strands as reinforcement. In this study, strandsof belangke bamboo (Gigantochloa pruriens W) and tali bamboo (Gigantochloa apus) were utilized. The non-wood particles included sugar palm fibers, cornstalk, and sugarcane bagasse. The board was made in a three-layer composition of the face, back, and core in a ratio of 1: 2: 1. The binder used was 8% isocyanate resin. The sheet was pressed at a temperature of 160℃ for 5 min under a pressure of 3.0 N/㎟. Testing included physical and mechanical properties based on the JIS A 5908 (2003) standard, while acoustic testing was based on ISO 11654 (1997) standards. The results showed that using bamboo strands as reinforcement has an effect on the mechanical and physical properties of SPb. Almost all the types of boards met the JIS A 5908 (2003) standards, with the exception of thickness swelling (TS) and internal bond (IB) parameters. Based on the thickness swelling parameter, the C-type board exhibited the best properties. Overall, the B-type board thatused a belangke bamboo strand for the surface and sugarcane bagasse as the core underwent the best treatment. Based on the acoustical parameter, boards using a tali bamboo strand for the surface and sugar palm fiber as the core (E-type board) exhibited good sound absorption properties.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.2
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• pp.160-168
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• 2022

The new IFF mode, Mode-5 replacing Mode-4, has already been established by the US DoD for its allies and NATO forces. A IFF retrofit program for replacing the Mark XII Mode-4 with Mark XIIA Mode-5 is in progress in order to overcome the security limitations of the former in R.O.K. IFF certification test for the new mode, Mode-5, has been performed on medium range surface to air missile platform of the Korean armed forces for the first time in R.O.K and this is regarded as a monumental event in Korean defense industry. The present paper is a discussion on the procedures applied to the IFF system retrofit and integration, lessons learned from AIMS test with the US AIMS PO as observer. The minimum modification from the existing Mark XII Mode-4 to Mark XIIA Mode-5 and evolutional adaption from previous design including interoperability are required for the system retrofit. Letter of Certification was received from the US AIMS PO after the tests. The authors propose that the lessons learned and know-how acquired during the tests are managed by the R.O.K Government as the standard structure of a database. It is expected that the use of the database will reduce the developmental difficulties and risk, also increase efficiency in future developments and other projects.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.409-416
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• 2012

Recently, surface modification technology is of importance to improve the wear resistance and the corrosive resistance for high accurate mechanical parts such as LM guide, Ball Screw and Roller Bearing etc., Those has generally featured on rolling contact mechanism to improve not only the wear and the friction, but also the accuracy and the corrosion performances. For surface modifications of high accurate mechanical parts, normally thermal spray, PVD, CVD and E.P. processes have been used with many materials such as DLC, raydent, W, Ni, Ti etc. Diamondlike carbon (DLC) films possess a combination of attractive properties and have been largely employed to modify the tribological behaviors such as friction, wear, corrosion, fretting fatigue, biocompatibility, etc. However, for rolling contact mechanism mechanical parts DLC films are needed to study for commercial benefit. Rolling contact mechanism has features on effects of cyclic motions and stresses, and also not simply sliding motions. The papers focused on the performance test of wear and corrosive resistance according to Me-DLC film thickness. And also, its thickness effect of wear analysis was carried out through the simulation of the maximum shear stress under the rolling contact surface. As the results, Me-DLC films have more potential to improve the wear resistance for high precision mechanical parts than raydent films.

• Membrane Journal
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• v.23 no.3
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• pp.220-225
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• 2013

Hydrophilic monomers were polymerized for lamination on polyvinylidene fluoride (PVDF) membrane surface for hydrophilization of the membranes. Hydrophilization reduced the contact angle from $95^{\circ}$ to $55^{\circ}$ and enhanced the water flux by 10 times while it reduced the bovine serum albumin (BSA) adsorption amount to 1/4 level. Thermal polymerization process was optimized by examining several operation parameters. Dimethyl oxobuthyl acrylamide (DOAA) showed the best effect due to its better hydrophilicity than others. Increase of amount of monomer enhanced the performance until the optimum concentration of 30 wt%, beyond which excess amount of monomer resulted in homopolymerization to deteriorate the performance. Azobis (isobutyronitrile)(AIBN) initiator has greater activation temperature range than benzoyl peroxide (BPO) and it showed better hydrophilation performance. Two stage lamination process, application of initiator followed by monomer addition, was more effective than one stage process, addition of initiator and monomer at once, which still reduced the contact angle but also reduced the water flux by pore blocking phenomena.