• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.7-14
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• 2008

• Journal of the Korean Society of Environmental Restoration Technology
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• v.15 no.5
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• pp.115-127
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• 2012

This study was conducted on the measurement of soil hardness through a hardness testing machine in slopes of natural environments and artificial environments which is generally known as slope revegetation. The soil hardness as one of physicochemical soil properties is significantly associated with plant growth. Although another studies related to the slope revegetation was focused on herbaceous plants, studies related to soil properties for arbor appearance is lack. It was focused on the correlation analysis between the soil hardness and the plant appearance. the results were as follows : The higher the soil hardness is, the less the appearance of plants is as a result of survey. Species appearing in the high levels of the soil hardness represented mugwort and grass. The levels of the soil hardness in the slope of natural environments was good environmental conditions with various plants in the range of 6 to 12mm. The levels of the soil hardness in the slope revegetation was in the 6.88-30mm range. The soil hardness below 21mm showed a variety of plants with arbors and herbaceous plants, whereas it above 21mm represented a monotonous style of plant structure including Artemisia princeps, Lolium perenne, Poa pratensis L and Setaria viridis. The result of the correlation analysis between the soil hardness and the plant appearance was negatively correlated with justifiable significance levels. The result of a logistic regression analysis for tree appearance was statistically proved when the numerical value of the soil hardness is lower.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.6
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• pp.767-775
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• 1999

The purpose of this study was to evaluate the effect of wattage and curing time on surface hard-ness, three-point bending strength and internal porosity of microwave curing denture base resin. Two sizes of resin specimens were made of Acron $MC^{(R)}\;;\;3.5{\times}10{\times}60mm$ for surface hardness and three-point bending strength measurement and $5{\times}12{\times}60mm$ for internal porosity measurement. They were cured by microwave energy at varing wattages(500W, 700W) and curing times(2min., 3min., 4min.) to determine if a certain wattage/curing time combination would improve physical properties. Surface hardness was measured with Vikers hardness tester, three-point bend-ing strength with universal testing machine and internal porosity was calculated by measuring the weight in air and in water. The results obtained were as follows: 1. There was no significant difference in percent porosity among experimental groups(p>0.05). 2. 500W/3min. group showed the higher surface hardness than 700W/2, 3, 4min. groups(p<0.05), and 700W/4 min. group showed the lower surface hardness than 500W/2, 3, 4min. groups(p<0.05), but there was no significant difference among others(p>0.05). 3. 500W/3min. group yielded the higher value of bending strength than 500W/2min., 700W/3, 4min. groups(p<0.05), but there was no significant difference among others(p>0.05).

• Journal of the Korean Society of Food Culture
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• v.30 no.2
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• pp.206-212
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• 2015

The purpose of this study was to investigate the quality characteristics of cookies containing Ligularia fischeri powder (0, 1, 2, 3, 4%) substituted for flour. This study measured the density, pH, spread ratio, volume, color values, hardness, and sensory properties of cookies. The pH of cookie dough significantly decreased in response to addition of Ligularia fischeri powder (LFP) at all levels. The spread factor of cookies also significantly increased with higher LFP content. In addition, Hunter's color L, a, and b values significantly decreased with increasing LFP content. According to hardness measurement, substitution of 1~4% LFP resulted in increased hardness compared to the control. In the sensory evaluation, sensory scores for color, flavor, and overall acceptability were highest in 2% Ligularia fischeri powder cookies. Thus, our results suggest that the optimum amount of Ligularia fischeri powder added to cookies was 2%. These results suggest that Ligularia fischeri powder can be applied to cookies to achieve high quality and functionality.

• Journal of the Korean institute of surface engineering
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• v.45 no.1
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• pp.31-36
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• 2012

In order to improve the mechanical roperties of the Gangjin celadon $BaTiO_3$ was added into the raw materials of celadon matrix. Through SEM and XRD analysis the structural changes were observed and the hardness values were measured. We could confirm that the mechanical strength considerably increased in the $BaTiO_3$ added celadon through the measurement of hardness values. The increase of mechanical strength values in the celadon may result from the compositional change in the microstructure such as grain boundary area through EDAX analysis. We might suggest a fundamental idea to improve the mechanical intensity of the celadon.

• Laser Solutions
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• v.15 no.3
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• pp.11-15
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• 2012

The laser weld of AZ31 magnesium alloy was characterized with OM, EBSD and micros vickers hardness tester in experiment. EBSD analysis and micro-hardness measurements were carried out at the three regions (Equiaxed Zone, Columnar Dendrite Zone, Base Metal) of the welded AZ31Mg alloy sheets. The magnesium alloy show the rectangular shape bead in laser weld. EBSD analysis revealed that the three regions show the heterogeneous distribution of grain size and microtexture. Micro-hardness measurement also revealed that the heterogeneous distribution of microstructure contributed to the heterogeneous micro-hardness distribution in the three regions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.11
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• pp.916-921
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• 2012

This research measured the dielectric properties of silicone rubber with various hardness in 100 Hz~3 MHz, $30{\sim}170^{\circ}C$ conditions. When the hardness increases from 65 degree to 75 degree, the dielectric loss increased within frequency range of 100 kHz~3 MHz and was a little change in dielectric loss within temperature range of $90^{\circ}C{\sim}170^{\circ}C$. Thermogravimetric Analysis (TGA) showed the weight change rate increased a little while heated until $800^{\circ}C$. Scanning Electron Microscope (SEM) measurement showed that Aluminium Trihydroxide($AlOH_3$) which acts as a reinforcement agent reduced the size of the particles as the hardness increased.

• Corrosion Science and Technology
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• v.5 no.4
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• pp.123-128
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• 2006

It was analyzed the causes of boiler tube rupture due to a degradation and corrosion on the boiler tubes in fossil power plant. The experiments were carried out among samples taken from the operating facilities. The result were analyzed based on experimental results from mechanical strength, microstructure observation, and hardness measurement in order to determine the cause of local rupture on boiler tubes. In general, 2.25Cr-1Mo steel generates carbides, it is coarsened, its ductility and strength abruptly decreased as degradation is in progress, In order to confirm this phenomenon, we observed changes of the mount of Cr and Mo of carbide by carrying out EDX chemical composition analysis. The amount of Cr and Mo in the degraded material or service exposed material gradually increased the amount of Mo but initially they were almost maintained at the same amount. Furthermore, we observed that the carbide become coarsened both in the grain and at the grain boundary. Tensile test was carried out to measure a material hardness and to recognize a drop-off of hardness. Overall result for tensile strength and hardness turned out to be lower than new material and mechanical strength and hardness was degraded as the material degradation was in progress.

• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.127-133
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• 2001

There are several factors affecting the effectiveness of polymerization of the esthetic restorative materials. Among those factors, the initiator. camphoroquinone has the unique characteristic. of which the light sensitivity is very dependent on the wavelength of blue light. Camphoroquinone shows the most light absorption ability in the wavelength range of 470nm. So most of clinically used light curing systems adopt this phenomenon as their polymerization mechanism. The most popular way of light curing system is standard 40 second curing. But the problem of standard curing technique shows the rapid increase of resin viscosity followed by the acceleration of polymerization and the limited resin flow, resulted in reduction of the physicalproperty of restoration by retained stress. The object of this study was to verify the effects of narrow-banded wavelength on the microhardness of the esthetic restorative materials. a composite resin and a compomer, using filters which have peak wave length of 430nm, 450nm, 470nm, respectively. The results were as follows: 1. All the experimental groups showed lower hardness value than the control group. 2. In DyractAP, the hardness value by wavelength showed the same changing pattern on both upper and lower surfaces. 3. In DenFil, the hardness value by wavelength showed different changing pattern on upper and lower surfaces. 4. The hardness ratio showed similar pattern to the hardness variation of lower surface. but there was no significant difference between measurement in 10 minutes and 3 days later, besides the increase of hardness value.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.2
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• pp.47-53
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• 1991

Recrystallization behaviors of ordered and disordered structures in $Ll_2$ type $Ni_3Fe$ alloy were studied through hardness measurement and differential thermal analysis. When the disordered structure was isothermally aged at $480^{\circ}C$ below order-disorder transition temperature, the hardness of the structure was increased due to progressive ordering with increasing aging time. The hardness of the disordered structure was increased rapidly with increasing deformation degree up to 10%, and then gradually increased with further deformation degree. while the hardness of the ordered structure was increased rapidly with increasing deformation degree up to 10%, showing a constant hardness value up to 50% and gradually decreased with further deformation degree. The hardness of the ordered structure was higher than that of the disordered structure at all same deformation degrees. The recrystallization temperature of the ordered and disordered structures were decreased with increasing deformation degree. At the same deformation degrees, the recrystallization temperature of the ordered structure was lower than that of the desordered structure.