• Journal of the Korean Wood Science and Technology
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• v.38 no.1
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• pp.1-10
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• 2010

In this study, to study an effective use and improve strength performances of woods and wood-based materials, three-ply hybrid laminated woods which are composed of spruce in the face and three kinds of wood-based boards (MDF, PB, OSB) in the core were manufactured, and the effect of constitution elements used for the core laminae on bending creep performances was investigated. The shape of creep curves showed exponential function plots which the upper right side was increased, and differed among the kinds of wood-based boards used for the core laminae of hybrid laminated wood. The creep deformation perpendicular to the grain of faces of hybrid laminated woods was in order $C_{\perp}$(P) > $C_{\perp}$(M) > $C_{\perp}$(O) with PB, MDF and OSB in the core, respectively. It was found that the creep deformation arranged with OSB in the core had 2 times smaller than those arranged with MDF and PB in the core. By hybrid laminating, the creep deformation of spruce perpendicular to the grain was markedly decreased. On the other hand, the creep deformation parallel to the grain of the faces ($C_{\parallel}$ type) of hybrid laminated woods was in order $C_{\parallel}$(P) > $C_{\parallel}$(O) > $C_{\parallel}$(M) with PB, OSB and MDF in the core. The ratios among three hybrid laminated woods were considerably decreased, especially the difference between $C_{\parallel}$(P) and $C_{\parallel}$(O) hybrid laminated woods arranged with PB and OSB in the core was very small. These values showed 0.108~0.464 times smaller than creep deformation of three wood-based boards and it was found that creep deformation of three wood-based boards was considerably decreased by hybrid laminating. Creep anisotropy of hybrid laminated woods was greater in creep deformation than in initial deformation, whereas it was found that the values was much smaller than that of spruce parallel laminated woods.

• Journal of Broadcast Engineering
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• v.15 no.4
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• pp.563-581
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• 2010

In this paper, we perform subjective visual quality assessments on UHD video for UHD TV services and analyze the assessment results. Demands for video services have been increased with availabilities of DTV, Internet and personal media equipments. With this trend, the demands for high definition video have also been increasing. Currently, 2K-HD ($1920{\times}1080$) video have been widely consumed over DTV, DVD, digital camcoders, security cameras and other multimedia terminals in various types, and recently digital cinema contents of 4K-UHD($3840{\times}2160$) have been popularly produced and the cameras, beam projects, display panels that support for 4K-UHD video start to come out into multimedia markets. Also it is expected that 4K-UHD service will appear soon in broadcasting and telecommunications environments. Therefore, in this paper, subjective assessments of visual quality on resolutions, color formats, frame rates and compression rates have been carried to provide basis information for standardization of signal specification of UHD video and viewing environments for future UHDTV. As the analysis on the assessments, UHD video exhibits better subjective visual quality than HD by the evaluators. Also, the 4K-UHD test sequences in YUV444 shows better subjective visual quality than the 4K-UHD test sequences in YUV422 and YUV420, but there is little perceptual difference on 4K-UHD test sequences between YUV422 and YUV420 formats. For the comparison between different frame rates, 4K-UHD test sequences of 60fps gives better subjective visual quality than those of 30fps. For bit-depth comparison, HD test sequences in 10-bit depth were little differentiated from those in 8-bit depth in subject visual quality assessment. Lastly, the larger the PSNR values of the reconstructed 4K-UHD test sequences are, the higher the subjective visual quality is. Against the viewing distances, the differences among encoded 4K-UHD test sequences were less distinguished in longer distances from the display.

• The Journal of Engineering Geology
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• v.26 no.2
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• pp.277-290
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• 2016

Deep geological cross-sectional data is generally not common nor easy to construct, because it is expensive and requires a great deal of time. As a result, geological interpretations at depth are limited. Many scientists attempt to construct geological cross-sections at depth using geological surface data and geophysical data. In this paper, we suggest a method for constructing cross-sections from limited geological surface data in a target area. The reason for this study is to construct and interpret geological cros-sections at depth to evaluate heat flow anomaly along the Yangsan fault. The Yangsan Fault passes through the south-eastern part of the Korean Peninsula. The cross-section is constructed from Sangbukmyeon to Unchonmyeon passing perpendicularly through the Yangsan Fault System trending NW-SE direction. The geological cross-section is constructed using the following data: (1) Lithologic distributions and main structural elements. (2) Extensity of sedimentary rock and igneous rock, from field mapping. (3) Fault dimension calculated based on geometry of exposed surface rupture, and (4) Seismic and core logging data. The Yangsan Fault System is composed of the Jain fault, Milyang fault, Moryang fault, Yangsan fault, Dongnae fault, and Ingwang fault which strike NNE-SSW. According to field observation, the western section of the Yangsan fault bounded by igneous rocks and in the eastern section sedimentary rocks are dominant. Using surface fault length we infer that the Yangsan Fault System has developed to a depth of kilometers beneath the surface. According to seismic data, sedimentary rocks that are adjacent to the Yangsan fault are thin and getting thicker towards the east of the section. In this study we also suggest a new method to recognize faults using core loggings. This analysis could be used to estimate fault locations at different scales.

• Restorative Dentistry and Endodontics
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• v.31 no.5
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• pp.344-351
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• 2006

The purpose of this study was to evaluate the thermal expansion characteristics of injectable ther-moplasticized gutta-perchas and a Resilon. The materials investigated are Obtura gutta-percha, Diadent gutta-percha, E&Q Gutta-percha Bar and Epiphany (Resilon). The temperature at the heating chamber orifice of an Obtura II syringe and the extruded gutta-percha from the tip of both 23- and 20-gauge needle was determined using a Digital thermometer. A cylindrical ceramic mold was fabricated for thermal expansion test, which was 27 mm long, with an internal bore diameter of 3 mm and an outer diameter of 10 mm. The mold was filled with each experimental material and barrel ends were closed with two ceramic plunger. The samples in ceramic molds were heated in a dilatometer over the temperature range from $25^{\circ}C$ to $75^{\circ}C$. From the change of specimen length as a function of temperature, the coefficients of thermal expansion were deter-mined. There was no statistical difference between four materials in the thermal expansion in the range from $35^{\circ}C$ to $55^{\circ}C$ (p > 0.05). However, Obtura Gutta-percha showed smaller thermal expansion than Diadent and Metadent ones from $35^{\circ}C$ to $75^{\circ}C$ (p < 0.05). The thermal expansion of Epiphany was similar to those of the other gutta-percha groups.

• Journal of the Korean Geophysical Society
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• v.3 no.2
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• pp.99-112
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• 2000

The Iksan Jurassic Granite shows relatively less fractures and homogeneous rock fabrics, and is one of the most popular stone materials for architectures and sculptures. Almost mutually perpendicular rift, grain, and halfway in the Iksan Jurassic Granite are well known to quarrymen based on its splitting directions, and therefore it should exhibit orthorhombic symmetry. Theoretically, there are 9 independent elastic stiffness coefficients $(C_{1111},\;C_{2222},\;C_{3333},\;C_{2323},\;C_{1313},\;C_{1212},\;C_{1122},\;C_{2233},\;and\;C_{1133})$ for orthorhombic anisotropy. In order to characterize the static and dynamic elastic properties of the Iksan Jurassic Granite, triaxial strains under uniaxial compressive stresses and ultrasonic velocities of elastic waves in three different polarizations are measured. Both experiments are carried out with six directional core samples from massive rock body. Using the results of experiments and the densities measured independently, the static and dynamic elastic coefficients are computed by simple mathematical manipulation derived from the governing equations for general anisotropic media. The static elastic coefficients increase ar uniaxial compressive stress rises. Among those, the static elastic coefficients at uniaxial compressive stress of a 24.5 MPa appear to be similar to the dynamic elastic coefficients under ambient condition. Although some deviations are observed, the preferred orientations of microcracks appear to be parallel or subparallel to the rift, the grain, and the hardway from microscopic observation of thin sections. This indicates that the preferred orientations of microcracks cause the elastic anisotropy of the Iksan Jurassic Granite. The results are to be applied to the effective use of the Iksan Jurassic Granite as stone materials, and can be used for the non-destructive safety test.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.180-188
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• 2014

It is very important accurate diagnosis and quick treatment in cerebrovascular disease, i.e. stenosis or occlusion that could be caused by risk factors such as poor dietary habits, insufficient exercise, and obesity. Time-of-flight magnetic resonance angiography (TOF-MRA), it is well known as diagnostic method without using contrast agent for cerebrovascular disease, is the most representative and reliable technique. Nevertheless, it still has measurement errors (also known as overestimation) for length of stenosis and area of occlusion in celebral infarction that is built by accumulation and rupture of plaques generated by hemodynamic turbulence. The purpose of this study is to show clinical trial feasibility for 3D-SPACE T2, which is improved by using signal attenuation effects of fluid velocity, in diagnosis of cerebrovascular disease. To model angiostenosis, strictures of different proportions (40%, 50%, 60%, and 70%) and virtual blood stream (normal saline) of different velocities (0.19 ml/sec, 1.5 ml/sec, 2.1 ml/sec, and 2.6 ml/sec) by using dialysis were made. Cross-examinations were performed for 3D-SPACE T2 and TOF-MRA (16 times each). The accuracy of measurement for length of stenosis was compared in all experimental conditions. 3D-SPACE 2T has superiority in terms of accuracy for measurements of the length of stenosis, compared with TOF-MRA. Also, it is robust in fast blood stream and large stenosis than TOF-MRA. 3D-SPACE 2T will be promising technique to increase diagnosis accuracy in narrow complex lesions as like two cerebral small vessels with stenosis, created by hemodynamic turbulence.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.229-237
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• 2012

Phosphorus was incorporated into Co/$Al_2O_3$ catalyst for FTS by impregnating an acidic precursor, phosphoric acid, in ${\gamma}-Al_2O_3$ support to improve the mechanical strength, the hydrothermal stability of the catalyst particle, and the catalytic performance as well. Surface characterization techniques such as FT-IR revealed that $AlPO_4$ phase was generated on the surface of the P-modified catalyst. The addition of phosphorus was found to alleviate the interaction between cobalt and alumina surface, and to increase reducibility of catalyst. The catalytic activity such as $C_{5+}$ productivity and turnover frequency (TOF) was calculated to evaluate catalytic performance. The influence of calcination temperature of the $Al_2O_3$ containing 2 wt.% P on the catalytic performance was also investigated. Through hydrothermal stability test and XRD analysis, the P-modified catalyst had strong resistant to the pressurized and hot $H_2O$. The mechanical strength of the P-modified catalyst was also examined through an in-house fluidized-bed vessel, and it was found that the catalyst fragmentation could be successfully suppressed with P. Taken as a whole, the best performance was shown to be at 1~2 wt.% P in alumina and at the calcination temperature of $500^{\circ}C$.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.656-662
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• 2007

Fuel reformer using plasma and shift reactor for CO oxidation were designed and manufactured as $H_2$ supply device to operate a polymer electrolyte membrane fuel cell (PEMFC). $H_2$ selectivity was increased by non-thermal plasma reformer using GlidArc discharge with Ni catalyst simultaneously. Shift reactor was consisted of steam generator, low temperature shifter, high temperature shifter and preferential oxidation reactor. Parametric screening studies of fuel reformer were conducted, in which there were the variations of the catalyst temperature, gas component ratio, total gas ratio and input power. and parametric screening studies of shift reactor were conducted, in which there were the variations of the air flow rate, stema flow rate and temperature. When the $O_2/C$ ratio was 0.64, total gas flow rate was 14.2 l/min, catalytic reactor temperature was $672^{\circ}C$ and input power 1.1 kJ/L, the production of $H_2$ was maximized 41.1%. And $CH_4$ conversion rate, $H_2$ yield and reformer energy density were 88.7%, 54% and 35.2% respectively. When the $O_2/C$ ratio was 0.3 in the PrOx reactor, steam flow ratio was 2.8 in the HTS, and temperature were 475, 314, 260, $235^{\circ}C$ in the HTS, LTS, PrOx, the conversion of CO was optimized conditions of shift reactor using simulated reformate gas. Preheat time of the reactor using plasma was 30 min, component of reformed gas from shift reactor were $H_2$ 38%, CO<10 ppm, $N_2$ 36%, $CO_2$ 21% and $CH_4$ 4%.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.239-246
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• 2017

There are various transversal structures (small dams or drop structures) in median and small streams in Korea. Most of them are concrete structures and it is so hard to exclude low-level water. Unless drainage valves and/or gates would not be installed near bottom of bed, sediment from upstream should be deposited and also contaminants attached to the sediments would devastatingly threaten the water quality and ecosystem. One of countermeasures for such problem is the bypass pipe installed underneath the transversal structure. However, there is still issued whether it would be workable if the gravels and/or stones would roll into and be not excluded. Therefore, in this study, the conditions to exclude the rip stone which enter into the bypass pipe was reviewed. Based on sediment transport phenomenon, the behavior of stones was investigated with the concepts from the critical shear stress of sediment and d'Alembert principle. As final results, the basis condition (${\tau}_c{^*}$) was derived using the Lagrangian description since the stones are in the moving state, not in the stationary state. From hydraulic experiments the relative velocity could be obtained. In order to minimize the scale effect, the extra wide channel of 5.0 m wide and 1.0 m high was constructed and the experimental stones were fully spherical ones. Experimental results showed that the ratio of flow velocity to spherical particle velocity was measured between 0.5 and 0.7, and this result was substituted into the suggested equation to identify the critical condition wether the stones were excluded. Regimes about the exclusion of stone in bypass pipe were divided into three types according to particle Reynolds number ($Re_p$) and dimensionless critical shear force (${\tau}_c{^*}$) - exclusion section, probabilistic exclusion section, no exclusion section. Results from this study would be useful and essential information for bypass pipe design in transveral structures.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.685-695
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• 2004

The aim of this study was to evaluate the resistance to degradation and to compare the wear resistance characteristics of four composite resins in an alkaline solution. The resistance to degradation was evaluated on the basis of mass loss(%), degradation depth(${\mu}m$), Si loss(ppm) and wear depth. The brands studied were Heliomolar flow, Filtek supreme, Point4, Tetric flow. The results were as follows: 1. The sequence of the mass loss was in descending order by Heliomolar flow, Filtek supreme, Point4, Tetric flow. There was significant differences among the materials except Heliomolar flow and Filtek supreme. 2. The sequence of the degree of degradation layer depth was in descending order by Filtek supreme, Heliomolar flow, Tetric flow, Point4. There were significant differences among the materials except Heliomolar flow and Tetric flow. 3. The sequence of Si loss was in descending order by Filtek supreme, Heliomolar flow, Point4, Tetric flow. There were significant differences among the materials except Point 4 and Tetric flow. 4. The sequence of maximum wear depth was in descending order by Heliomolar flow, Point4, Fillet supreme, Tetric flow and there was increasing wear depth on soaking in 0.1N NaOH solution. 5. When observed with SEM, destruction of bonding between matrix and filler was observed and when observed with CLSM, the depth of degradation layer of specimen surface was observed. There results indicate that wear and hydrolytic degradation could be considered to be evaluation factors of composite resins.