• The Korean Journal of Food And Nutrition
• /
• v.13 no.1
• /
• pp.83-87
• /
• 2000

The effect of commerical bacteriocin(Bc) was studied on some quality changes during fermentation of Kimchi at $25^{\circ}C$. The Bc additon by 1.0, 3.0 and 5.0% was found to be effective in extension of pH decrease to reach the optimal pH of pH 4.0~4.2. Thel effect increased with an increase in bacteriocin concentration. The color values of 'L' and 'b' of the Kimchi liquid increased while 'a' value decreased during fermentation. The hardness also increased until 21 hours and then decreased and a slightly more hardness measured at the late stage of fermentation.

• Journal of the Korean institute of surface engineering
• /
• v.30 no.5
• /
• pp.298-309
• /
• 1997

Hard Tin coating on tool steel substrate were prepared using the pulsed PACVE. An orthogonal experimental design was employed to find the best deposition conditions for TiN coating and to systematically understand the effect of processing parameters. The small size Taguchi matrix called the L16 was used for experiment and ANOVA(ANalysis of VAriance) was followed to study the effect of main parameters on hardness and adhesion TiN coatings. In conclusion, pulse on/off time ratio and pulsing frequency were the major deposition parameters to determine hardness and adhesion of TiN coating in the pulsed DC PACVE process. (200) preferred orientation, columnar growth and dome-shaped surface morphology of the TiN films gave rise to a high hardness and a good adhesion to the substrates.

• Journal of Welding and Joining
• /
• v.30 no.2
• /
• pp.70-75
• /
• 2012

In this study, effect of nitrogen volume in the shielding gas of Ar-$N_2$ mixing gas on the bead shape, hardness and microstructure of GTA welds of 3mm thick Commercial Pure Ti was investigated. As the nitrogen volume increased, the welding current for full penetration was reduced and hardness in the fusion zone significantly increased compared with that of the base metal, but there is no difference in the hardness of HAZ. Microstructure in the fusion zone with pure Ar gas changed from equiaxed alpha of the base metal to serrated alpha. On the other hand, microstructure using Ar-$N_2$ mixing gas changed to acicular alpha. With the increasing of nitrogen content, the amount of acicular alpha increased and the size of that was fine.

• Journal of Biomedical Engineering Research
• /
• v.31 no.1
• /
• pp.33-39
• /
• 2010

During running, the human body experiences repeated impact force between the foot and the ground. The impact force is highly associated with injury of the lower extremity, comfort and running performance. Therefore, shoemakers have developed shoes with various midsole properties to prevent the injury of lower extremity, improve the comfort and enhance the running performance. The purpose of this study is to investigate influence of midsole hardness on shock absorption along the human body during running. Thirty two expert runners consented to participate in the study and ran at a constant speed with three different pairs of shoes with soft, medium and hard midsole respectively. Using accelerometers we measured the shock absorption from shoe heel to cervical vertebral column. In conclusion, at the shoe heel, shock was the greatest with the hard midsole. However because most shock was absorbed between shoe heel and the knee, notable influence of midsole was not detected upper knee. At shoe heel, regardless of midsole hardness, the shock of younger female was the greatest. The authors expect to apply this result for providing a guideline for utilizing proper midsole hardness for manufacturing age and gender-specific shoe.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.2 no.2
• /
• pp.98-105
• /
• 2003

In the experimental study, wire EDM was conducted for cold die steel by changing the Wire electrode, peak discharge current and number of finish cut. From the micro structure analysis of SEM photographs, the size of irregular welded and added component on the EDMed surface is decreasing and size of EDMed plane surface is increasing as the decreasing peak current and increasing number of finish cut. From the analysis of coating effect, Zn component is highly contained in Br and Zn Wire EDMed surface and copper component is highly contained in Br and Al wire EDMed surface. Hardness values are Increasing as the increasing peak current and decreasing the number of finish cut The value of hardness is decreasing as Cu, Al, Zn and Br wire electrode because of the residual austenite effect of solid solution copper on solidification, and finally EDMed surface has the highest hardness values for every wire electrode. Yield strength values becomes larger and bending strength values become smaller due to the increasing the hardness. These results are increased as increasing brittleness with hardness.

• Journal of the Korean institute of surface engineering
• /
• v.44 no.6
• /
• pp.246-249
• /
• 2011

Surface modification before coating nickel by coupling agents and/or etchant of glass did not provide enough adhesive strength of electroless nickel deposits on glass. Effect of heat treatments on hardness as well as adhesion of nickel deposits was studied by using tape test for adhesion, nanoindenter for hardness and glancing angle x-ray diffractometer (GAXRD) for phase characterization. Heat treatment improved hardness as well as adhesion. XRD results give that the improvements of adhesion and hardness are due to the formation of $NiSiO_4$ around the interface between the nickel deposits and the glass and the precipitation of $Ni_3P$ causing precipitation hardening, respectively. The details in effects of heat treatment on adhesion and hardness are described here.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.12
• /
• pp.126-134
• /
• 2003

In order to investigate the effect of surface treatment in Aluminium alloy and Titanium alloy which are used to armor material during ballistic impact, a ballistic testing was conducted. Anodizing was used to achieve higher surface hardness of Aluminium alloy and Iron plating in PVD(Physical Vapor Deposition) method was used to achieve higher surface hardness of Titanium alloy. Surface hardness test were conducted using a Micro victor's hardness tester. Ballistic resistance of these materials was measured by protection ballistic limit(V-50), a statical velocity with 50% probability penetration. Fracture behaviors and ballistic tolerance, described by penetration modes, are respectfully observed from the results of V-50 test and Projectile Through Plates (PTP) test at velocities greater than V-50. PTP tests were conducted with 0$^{\circ}$obliquity at room temperature using 5.56mm ball projectile. V-50 tests were conducted with 0$^{\circ}$obliquity at room temperature with projectiles that were able to achieve near or complete penetration during PTP tests. Surface hardness, resistance to penetration. and penetration modes of surface treated alloy laminates are compared to those of surface non-treated alloy laminates. A high speed photography was used to analyze the dynamic perforation phenomena of the test materials.

• Journal of the Korean Society of Industry Convergence
• /
• v.26 no.1
• /
• pp.79-86
• /
• 2023

This study was investigated the effect of carbon on the micro-structure and hardness of ductile cast iron roll with internal curing capacity. Spheroidal graphite existed at roll body with rapid cooling, but granular graphite existed at roll neck with slow cooling. The volume fraction of graphite increased at roll body with rapid cooling, That of roll neck with slow cooling decreased, but graphite size increased. The volume fraction of cementite decreased, but volume fraction increased. The cementite size was larger at roll neck than roll body. The hardness was decreased at roll body and roll neck due to volume fraction of cementite. The hardness of roll body was higher than roll neck.

• Transactions of Materials Processing
• /
• v.20 no.7
• /
• pp.479-484
• /
• 2011

Dry sliding wear behavior of AISI 52100 steel that has a pearlite or bainite microstructure was characterized to explore the effect of microstructure on the wear of the steel. Isothermal heat treatments were employed to obtain the different microstructures. Pin-on-disk type wear tests of the steel disk were performed at loads of 25~125N in air against an alumina ball. Sliding speed and wear distance used were 0.1m/sec and 300m, respectively. Worn surfaces, wear debris and cross-sections of the worn surfaces were examined with SEM to investigate the wear mechanism of the steel. Hardness of the steel was also evaluated. Wear rate of the steel was correlated with the hardness and the microstructure. On the whole, wear resistance increased with an increase in hardness. However, the pearlite microstructure showed superior wear resistance as compared to the bainite microstructure with a similar hardness. The effect of the microstructure on the wear rate was attributed to the morphological differences of the carbide in the microstructure, which was found to have a significant effect on strain hardening during the wear.

• Journal of Power System Engineering
• /
• v.20 no.5
• /
• pp.14-19
• /
• 2016

This study is about the effect of nitrogen gas pressures during manufacturing process on the mechanical properties of composite materials. $TiO_2$/epoxy resin nanocomposites and carbon fiber reinforced epoxy resin(CFRP) composites were fabricated under various nitrogen gas pressures. Tensile strength test, vicker's hardness test and fracture surface observation were carried out to investigate the effect of nitrogen gas pressure. As a result, the tensile strength of nanocomposite and CFRP composites showed clearly increasing tendency by a change in the nitrogen gas pressure up to 3.0 atm and then the tensile strength decreased a little. However, the vicker's hardness of $TiO_2$/epoxy nanocomposites showed same hardness values regardless of the nitrogen gas pressures.