• Geomechanics and Engineering
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• v.31 no.5
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• pp.461-476
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• 2022

Research studies on the scale effect on triaxial strength of intact rocks are scarce, being more common those in uniaxial strength. In this paper, the authors present and briefly interpret the peak and residual strength trends on a series of triaxial tests on different size specimens (30 mm to 84 mm diameter) of an intact granitic rock at confinements ranging from 0 to 15 MPa. Peak strength tends to grow from smaller to standard-size samples (54 mm) and then diminishes for larger values at low confinement. However, a slight change in strength is observed at higher confinements. Residual strength is observed to be much less size-dependent. Additionally, this study introduces preliminary modelling approaches of these laboratory observations with the help of three-dimensional particle flow code (PFC3D) simulations based on bonded particle models (BPM). Based on previous studies, two modelling approaches have been followed. In the first one, the maximum and minimum particle diameter (D_max and D_min) are kept constant irrespective of the sample size, whereas in the second one, the resolution (number of particles within the sample or ϕ_v) was kept constant. Neither of these approaches properly represent the observations in actual laboratory tests, even if both of them show some interesting capabilities reported in this document. Eventually, some suggestions are provided to proceed towards improving modelling approaches to represent observed scale effects.

• Korean Journal of Oriental Medicine
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• v.12 no.3 s.18
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• pp.101-115
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• 2006

The purpose of this study was to introduce the differential standard of the types of Angelicae Pubescentis Radix. We established the classificatory standard according to the external and internal morphology and the physicochemistrical pattern for the four types of Aucklandiae Radix. The results follow: 1. At the external shape, Angelica pubescens f. biserrata has rising lenticel and dark brown surface, Its section is light gray and its xylem is yellow gray. Aralia continentalis has big stem mark in upper portion, its section has no dense tissue with yellow gray. Heracleum hemsleyanum has dark brown surface and little lenticel, its cortical layer is white yellow and xylem is isabella and powdered. 2. At the internal shape, Angelica pubescens f. biserrata has phloem with half of the root and rare vessel. Aralia continentalis has phloem with two-thirds of the root and it has broad cutting and putting vessel that formed 1-2 row. Heracleum hemsleyanum also has phloem with half of the root and wide scattered latex tube and many large vessel. 3. At the TLC pattern, Heracleum hemsleyanum has remarkable dark spot at $R_{f}$ 0.23 on the sulphuric acid color pattern test, but others have faint. 4. At the HPLC pattern, all samples have generally patterns. But Angelica pubescens f. biserrata shows diminutive continentalic acid content and the peak at Rt 20.278min comes out on Heracleum hemsleyanum, but do not come out on Aralia continentalis and Angelica pubescens f. biserrata. Heracleum hemsleyanum has remarkable peak at Rt 20.278min, but shows no peak at Rt 29.023min unlike Aralia continentalis or Angelica pubescens f. biserrata. Also Aralia continentalis and Angelica pubescens f. biserrata show one remarkable peak at Rt 29.023, but Heracleum hemsleyanum do not show. Consequently, Aralia continentalis and Angelica pubescens f. biserrata are comparable whit continentalic acid content and Heracleum hemsleyanum is comparable with the peak at Rt 20.273 and Rt 29.023. So it is thought that content of continentalic acid and the peaks at Rt 20.278 and Rt 29.023 can apply to differentiate a species from other. It is considered the results of this study will be furnished the basis to succeeding studies and it is needed to extensive comparative study for the same genus-degree of relatedness.

• Journal of the Korean Ceramic Society
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• v.44 no.1 s.296
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• pp.52-57
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• 2007

We synthesized $(La_{1-x}Sr_x)MnO_3$ as a cathode for SOFC by glycine nitrate process (GNP) and knew the different properties of $(La_{1-x}Sr_x)MnO_3$ by using nitrate solution and oxide solution as a starting material. In case of using nitrate solution as a starting material, main crystal phase peak of $LaMnO_3$ increased as Sr content added up and a peak of $Sr_2MnO_4\;and\;La_2O_3$ was showed as a secondary phase. We added Mn excess to control a crystal phase. In this case, the electrical conductivity had a high value 210.3 S/cm at $700^{\circ}C$. On the other side, when we used oxide solution as a starting material, we found main crystal phase of $LaMnO_3$ to increase as Sr content added up and a peak of $La_2O_3$ as a secondary phase. Similary, we added Mn excess to control a crystal phase in this case. We knew $(La,Sr)MnO_3$ powder to sinter well and the electrical conductivity of the sintered body at $1200^{\circ}C$ for 4 h was 152.7 S/cm at $700^{\circ}C$. The sintered $(La,Sr)MnO_3$ powder at $1000^{\circ}C$ for 4 h got the deoxidization peak, depending on the temperature and in case of using nitrate solution as a starting material, the deoxidization peak was showed at $450^{\circ}C$ which is lower than used a oxide solution as a starting material. As a result, when $(La,Sr)MnO_3$ powder was synthesized to add Mn excess and to use nitrate solution as a starting material, we found it to have the higher deoxidization property and considered it as a cathode for SOFC properly. And we found it to have different electrical conductivity the synthesized $(La,Sr)MnO_3$ powder by using different starting materials like nitrate solution and oxide solution which influence a sintering density and crystal phase.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.818-824
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• 2003

Capillary electrophoresis (CE) and near-infrared spectroscopy (NIRS) were performed to discriminate astragalus roots (Astragalus membranaceus) according to geographical origin (domestic or foreign). Two-hundred-and-four astragalus roots were extracted with 30% methanol in 0.1 M phosphate buffer (pH 2.5) and separated in a uncoated fused-silica $(50\;{\mu}m{\times}27\;cm)$ capillary. Conditions for optimal analysis included: temperature $-45^{\circ}C$, voltage -14 kV, and pressure injection time -8 sec. The optimal separation buffer was 0.1 M phosphate buffer (pH 2.5) containing 40 mM hexane sulfonic acid with 20% 2-methoxy ethanol. Raw NIR spectra were obtained using NIRS, and modified partial least square regression was used to develop the prediction model. The correlation coefficient and standard error of prediction were 0.915 and 14.3%, respectively. Under the optimal conditions established for CE and NIRS, the geographical origins of the astragalus roots were correctly identified in 80 and 97%, respectively. Astragalus roots that were not discriminated by NIRS were correctly discriminated by CE. Hence, CE and NIRS are potential methods for discriminating the geographical origins of astragalus roots that complement one another.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.1
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• pp.16-29
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• 2008

Nitrous acid (HONO) can be produced by heterogenous reactions of nitrogen dioxide on surface materials and direct emission from combustion sources. However, a little is known of indoor HONO levels or the relationship between residential HONO, NO, and $NO_2$ concentrations in occupied houses. Therefore, we measured simultaneously NO, $NO_2$, and HONO concentrations in living room of an apartment using continuous analyzers to study the production of HONO (June $22{\sim}30$, 2006). The 4-min average concentrations of indoor NO, $NO_2$, and HONO were 4.3 (range: $0.4{\sim}214.3$), 10.3 ($2.0{\sim}87.3$), and 1.8 ppb ($0.3{\sim}7.7$), respectively. Peak levels of HONO up to 7.7 ppb and 24-hr averages as high as 1.7 ppb were measured. In agreement with previous studies, indoor HONO concentrations increased during operation of an unvented gas range. Examination of the observed kinetics suggests that the secondary production of indoor HONO, possibly as a result of heterogeneous reactions involving $NO_2$ and $H_2O$ is associated with $[NO_2]^2[H_2O]\;(r^2=0.88)$ rather than with $[NO][NO_2][H_2O]\;(r^2=0.75)$. Three combustion experiments at nighttime were also carried out to investigate the effects of vented combustion on the HONO, NO, and $NO_2$ concentrations. It was found to release HONO for $10{\sim}15$ minutes after NO and $NO_2$ source was turned off, and peak values were finally attained. Compared to unvented combustion, peak $NO_2$ and HONO concentrations were 3.2 and 2.0 times lower at weak vented combustion (air flow: $340\;m^3/hr$) and 4.9 and 2.4 times lower at strong vented combustion (air flow: $540\;m^3/hr$), respectively, emphasizing importance of operating ventilation hood fan during combustion to improve indoor air quality.

• Korean Journal of Materials Research
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• v.8 no.3
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• pp.189-194
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• 1998

The redistribution behavior of boron during Co silicidation annealing in the Co/metal/Si system was investigated using SIMS. Ti, Nb and Hf films were used as epitaxy promoting metal layers. After annealing treatment the boron peak height was about 1 order lowered in Co/Ti/Si and Co/Nb/Si systems but the relative peak position from the surface did not change. The distribution of boron was very similar to those of Ti and Nb, because of the strong affinities of boron with them. Also, the position of the main boron peak in the Co/Hf/Si system was almost the same as that of Hf, but the distribution feature of the Co/Hf/Si system somewhat differed from those of Co/Ti/Si and Co/Nb/Si systems. This implies that the affinity between B and Hf is weaker than those of B-Ti and B-Nb. Boron tends to be depleted at the silicidelsi interface while it tends to be piled-up at the Co-metal/Co silicide interface during silicidation annealing.

• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.121-128
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• 2019

Objective: The aim of this study was to examine the relation between swing phase and airborne phase of Tkatchev motion which was successfully performed with following motion by excellent middle and high school athletes in horizontal bar. Method: The subjects for this study were 8 male middle and high school top athletes. After their Tkatchev motions were filmed by two digital highspeed camcorders setting in 90 frames/sec at the 44th National Gymnastics against Cities and Provinces, the % lapse time lapse time of each instant, inferred maximum force acting on horizontal bar, and other kinematical variables were calculated through DLT method. After the relations among the % lapse times of each instants of downswing-start, downswing-finish, whipswing-finish, release, peak-height, and lapse time of regrasp, the relation among maximum force acting on bar, % lapse time, peak height, and the relation between % lapse time and release height were examined, the biomechanical timing characteristics of Tkatchev motion were as follows. Results: Firstly, it was revealed that the whole lapse time was $1.62{\pm}.06s$ and the correlation between the % lapse time of downswing-start and % lapse time of release was .819. Secondly, it was revealed that the pattern of COG path was shifted forwardly and tilted 11 clockwise from origin. Thirdly, it was revealed that maximum force acting on bar was inferred in $2,283{\pm}425N$ ($4.7{\pm}.6BW$) and the correlation between maximum force and peak height was r = .893. Lastly, it was revealed that the horizontal and vertical component of body COG velocity was $-2.14{\pm}.29m/s$, $2.70{\pm}.43m/s$ respectively, release height was $.49{\pm}.12m$, and shoulder angle was $139{\pm}5deg$, and that the later the % lapse time of release, the higher the release height (r = .935). Conclusion: It is desired that the gymnastic athletes should delay the downswing-start near the horizontal plane on $2^{nd}$ quadrant because the later the % lapse time of downswing, the higher the release height. After all the higher release height could ensure the athletes to regrasp the bar safely, the athletes should exercise to make downswing-start delay.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.173-180
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• 2019

This study was conducted to understand factors affecting TSS and heavy metals transport on the road, parking lot and roof. During storm events, heavy metals, which were mostly attached to TSS, were also transported when TSS was washed off in the road, parking lot and roof. This finding may be supported by the significant correlations between TSS load and total and soluble heavy metals load including Cr, Fe, Cu, and Pb (Pearson r value: 0.52 to 0.73; probability p value<0.01). Generation and transport of TSS and heavy metals were greater in the road and parking lot compared to the roof due to vehicular activities, slope and greater catchment areas of these sites. It was found that TSS transport during peak flows of storm events ranges from 65% to 75% implying that by controlling peak flows, TSS transportation to nearby water bodies may be decreased. Depending on the target TSS and heavy metal reduction, sizing of low impact development (LID) technologies and green infrastructures (GI) such as infiltration trench, tree box filter, and rain garden may be calculated. Future researchers were recommended to assess the limitations of the systems and determine the design considerations for these types of facilities.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.568-573
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• 2010

Adhesive strength was evaluated for the polyester fabric treated with various concentration of polymeric isocyanate to introduce functional group on the surface. Also experiments were performed to find out the type of latex, F/R mole ratio, and FR resin/latex weight ratio for the RFL solution to optimize adhesion between HNBR compound and the treated polyester fabric. Optimum adhesion strength was obtained when 7 wt% of the concentration of polymeric isocyanate, NBR latex because of the compatibility of HNBR compound, 1/1 of F/R mole ratio, and 20 wt% of FR resin/latex were applied. Optimum cure temperature for the RFL solution was $200^{\circ}C$ according to the results of peel test and the reason was determined by analyzing the ATR FTIR spectra of the RF resin according to the curing temperature.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.17-26
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• 2001

In order to estimate peak ground motions and frequency characteristics of strong ground motions in southern korea, we employed the stochastic simulation method with the moment magnitude(M$_{w}$) and the hypocentral distance(R). We estimated same input parameters that account for specific properties of source and propagation processes, and applied them to the stochastic simulation method. The stress drop($\Delta$$\sigma$) of 100-bar was estimated considering results of research in ENA, China, and southern korea. The attenuation parameter x was calculated by analyzing 57 seismograms recorded from September 1996 to October 1997 and the estimation result of the attenuation parameter x is 0.00112+0.000224 R where R is hypocenter distance. We estimated strong ground motion relations using the stochastic simulation method with suitable input parameters(e.g. $\Delta$$\sigma$, x, and so on). At last, we derived relations between hypocentral distances and ground motions(seismic attenuation equation) using results of the stochastic prediction.esults of the stochastic prediction.n.