• Journal of Welding and Joining
• /
• v.32 no.5
• /
• pp.44-49
• /
• 2014

The effect of weldbond hybrid joining process on the mechanical behavior of single lap and L-tensile joints was investigated for the newly developed 1.2GPa grade ultra high strength TRIP(transformation induced plasticity) steel. In the case of single lap shear behavior, the weldbond joint of 1.2GPa TRIP steel showed lower maximum tensile load and elongation than that of the adhesive bonding only. It was considered to be due to the reduction of real adhesion area, which was caused by the degradation of adhesive near the spot weld, and the brittle fracture behavior of the spot weld joint. In the case of L-tensile behavior, however, the maximum tensile load of the weldbond joint of 1.2GPa TRIP steel was dramatically increased and the fracture mode was change to the base metal fracture which is desirable for the spot weld joint. These synergic effect of the weldbond hybrid joining process in 1.2GPa TRIP steel was considered to be due to the stress dissipation around the spot weld joint by the presence of adhesive which resulted in the change of crack propagation path.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.6
• /
• pp.575-581
• /
• 2015

The drill bit, which directly transmits percussive forces and torque to the rock, is the core part of a rock drilling machine. For effective drilling, the button arrangement of a drill bit should be optimized because it is the most important design factor in determining drilling efficiency. Furthermore, a quantitative method is necessary to evaluate the button arrangement for the optimization of the drill bit button. Therefore, we propose a new method for the evaluation of the drill bit button arrangement using new evaluation indices, which include the overlapped impact area, blank area, and moment. Moreover, we verify the suitability of the proposed evaluation method by applying it to the conventional button arrangement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.10
• /
• pp.844-848
• /
• 2012

Encapsulant curing in terms of convection oven leads to thermal induced stress due to nonuniform thermal conductivity in LED package. We have adopted infrared (IR) light for silicone curing in order to release the stress. The light uniformity irradiated on an encapsulant surface is confirmed to be uniform by optical simulation. Shear strength of die paste using IR compared to convection oven is increased 19.2% at the same curing time, which indicates curing time can be shortened. The indentation depth difference between center and edge of silicone encapsulant in terms of convection oven and IR are 14.8% and 3.4%, respectively. Curing by IR also shows 2.3% better radiant flux persistency rate of LED at $85^{\circ}C$ after 1,000 h reliability test compared to convection curing.

• The Korean Journal of Physiology and Pharmacology
• /
• v.13 no.6
• /
• pp.425-429
• /
• 2009

Intracranial headaches, including migraines, are mediated by nociceptive activation of the trigeminal nucleus caudalis (TNC), but the precise mechanisms are poorly understood. We previously demonstrated that selective blockage of spinal sigma-1 receptors (Sig-1R) produces a prominent antinociceptive effect in several types of pain models. This study evaluates whether the Sig-1R antagonist (BD1047) has an antinociceptive effect on capsaicin (a potent C-fiber activator) induced headache models in rats. Intracisternal infusion of capsaicin evoked pain behavior (face grooming), which was significantly attenuated by BD1047 pretreatment. BD1047 consistently reduced capsaicin-induced Fos-like immunoreactivity (Fos-LI), a neuronal activator, in the TNC in a dose-dependent manner. Moreover, capsaicininduced phosphorylation of N-methyl-D-aspartate receptor subunit 1 was reversed by BD1047 pretreatment in the TNC. These results indicate that the Sig-1R antagonist has an inhibitory effect on nociceptive activation of the TNC in the capsaicin-induced headache animal model.

• Korean Journal of Microbiology
• /
• v.49 no.1
• /
• pp.46-50
• /
• 2013

Some rhizobacteria producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase can make plant to continue growth under the stress conditions through lowering the level of phytohormone, ethylene which inhibits the plant growth and accelerates plant aging. In this study, some rhizobacteria producing ACC deaminase have been isolated from the rhizosphere of plants grown at sand beaches, and identified as Escherichia hermannii m-2, Enterobacter asburiae m-4, Pseudomonas thivervalensis BD2-26 and Pseudomonas brassicacearum subsp. neoaurantiaca BD3-35 through sequencing of 16S rRNA genes. Strain BD3-35 showed the highest activity of ACC deaminase among the isolates, 20.26 ${\alpha}$-ketobutyrate ${\mu}M/mg$ protein/h. Strains BD3-35 and BD2-26 secreted a phytohormone cytokinin, and strains m-4 and m-2 could produce auxin and abscisic acid, respectively. When these bacteria were applied to the 7-day old tomato plant under drought stress for 7 days, strains BD3-35, m-2, and m-4 increased the length of tomato root by 14, 15, and 35%, respectively, and strains m-2, BD2-26 and BD3-35 increased the dry weight of tomato plant by 22, 33, and 68%, respectively compared to the uninoculated control tomatoes. Therefore, these rhizobacteria may be utilized as a microbial fertilizer for the plants under drought stress.

• Transactions of the Society of Information Storage Systems
• /
• v.8 no.2
• /
• pp.50-55
• /
• 2012

Optical disks are widely used in libraries and archives as digital data media due to their long-term storage stability. Though archive-grade optical disks are already available on the market, there is a relative less focusing on the reliable recording conditions. Commercial BD-R media were recorded at various recording speeds with the maximum speed of 6X, and tested at the acceleration aging conditions. Through the evaluation of long-term storage features by the data stability test, lower recording speed of 2x resulted in better long-term storage stability. In addition, degradation aspects of unstable long-term storage feature at outer region of disk were discussed.

• Journal of Welding and Joining
• /
• v.32 no.6
• /
• pp.35-40
• /
• 2014

The contact tip for gas metal arc welding has important functions to transmit the welding current to the wire and to guide the wire to molten pool. If the contact tip is damaged, it is a cause of lowering the welding productivity due to removal of welding defects and replacement of contact tip. In case of the use of a contact tip for a long time the arc is unstable because the processed hole in the contact tip center is larger, and the variation of aiming position of the welding wire causes a seam tracking error. In this study, gas metal arc welding experiments using contact tip of three different materials were performed. The contact tips with Cu-P, Cu-Cr, and Cu-ODS were used at the experiments, and the welding characteristics by each contact tip were evaluated. After welding contact tip appearance, welding spatter adhesion amount of the nozzle, and weld bead appearance were evaluated. The welding current and welding voltage were measured to verify arc stability during arc welding.

• Korean Journal of Materials Research
• /
• v.24 no.11
• /
• pp.591-598
• /
• 2014

In this research, magnesium powder was prepared by gas atomizing. Refinement behaviors of magnesium powder produced under different conditions were investigated using a mechanical milling (attrition milling) process. Analyses were performed to assess the characterization and comparison of milled powder with different steel ball sizes and milling times. The powders were analyzed by field emission scanning electron microscope, apparent density and powder fluidity. The particle morphology of the Mg powders changed from spherical particles of feed metals to irregular oval particles, then plate type particles, with an increasing milling time. Because of the HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, which results in producing plate-type powders. An increase in ball size and the impact energy of the magnesium powder maximizes the effect of refinement. Furthermore, it is possible to improve the apparent density and fluidity according to the smoothness of the surface of the initial powder.

• Elastomers and Composites
• /
• v.51 no.3
• /
• pp.188-194
• /
• 2016

In this study, novel quaternary plastomers consisting of ethylene, 1-hexene, high ${\alpha}$-olefin, and divinylbenzene were prepared using Zr metallocene catalyst, borate type cocatalyst, and tri-isobutylaluminium. The molar ratio changes of 1-hexene and high ${\alpha}$-olefin (1-octene, 1-decene, and 1-dodecene) had an effect on the properties of the quaternary plastomers. The structure of the quaternary plastomers was characterized using $^1H$ NMR. Molecular weight properties, crystallinity, and thermal properties of the plastomers were determined by GPC, WAXS, and DMA, respectively. Compared with the terpolymers prepared in our previous study, molecular weight and molecular weight distribution of the quaternary polymers were very similar, whereas glass transition temperature ($T_g$) was very low. Also, hardness and tensile properties of the quaternary plastomers were measured.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.12
• /
• pp.1067-1076
• /
• 2014

To date, biomedical application of three-dimensional (3D) printing technology remains one of the most important research topics and business targets. A wide range of approaches have been attempted using various 3D printing systems with general materials and specific biomaterials. In this review, we provide a brief overview of the biomedical applications using 3D printing techniques, such as surgical tool, medical device, prosthesis, and tissue engineering scaffold. Compared to the other applications of 3D printed products, the scaffold fabrication should be performed with careful selection of bio-functional materials. In particular, we describe how the biomaterials can be processed into 3D printed scaffold and applied to tissue engineering area.