• Geomechanics and Engineering
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• v.16 no.5
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• pp.495-501
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• 2018

Geogrid application that has proved to be an effective and economic method of reinforcing particles, is widely used in geotechnical engineering. The discrete element method (DEM) has been used to investigate the micro mechanics of the geogrid deformation and also the interlocking mechanism that cannot be easily studies in laboratory tests. Two types of realistically shaped geogrid models with square and triangle apertures were developed using parallel bonds in PFC3D. The calibration test simulations have demonstrated that the precisely shaped triangular geogrid model is also able to reproduce the deformation and strength characteristics of geogrids. Moreover, the square and triangular geogrid models were also used in DEM pull-out test simulations with idealized shape particle models for validation. The simulation results have been shown to provide good predictions of pullout force as a function of displacement especially for the initial 30 mm displacement. For the granular material of size 40 mm, both the experimental and DEM results demonstrate that the triangular geogrid of size 75 mm outperforms the square geogrid of size 65 mm. Besides, the simulations have given valuable insight into the interaction between particle and geogrid and also revealed similar deformation behavior of geogrids during pullout. Therefore, the DEM provides a tool which enable to model other possible prototype geogrid and investigate their performance before manufacture.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.5
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• pp.38-43
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• 2015

In this paper, we present novel dual-band microstrip antennas using inverted-L-shaped parasitic elements vertically at radiation apertures for GPS L1(1.575 GHz) and L2(1.227 GHz) bands. For making dual band which has large interval, the inverted-L-shaped parasitic element was loaded at the radiation aperture of a half-wavelength patch antenna(GPS L1) in opposite direction of the feeding point for receiving the low frequency(GPS L2). The low frequency occurs by perturbation and coupling between the patch and parasitic. Next, due to use circular polarizations at the GPS applications, two inverted-L-shaped parasitic elements were loaded at radiation apertures of each polarizations and the feeding point was moved at diagonal part of the patch. The dimensions of the designed circularly polarized antenna were $88.5{\times}79{\times}10.4mm^3$ ($0.36{\lambda}L{\times}0.32{\lambda}L{\times}0.04{\lambda}L$, ${\lambda}L$ is the free-space wavelength at 1.227 GHz). Measured -10 dB bandwidths were 116.3 MHz(7.4%) and 64.3 MHz(5.2%) at GPS L1 and L2 bands, respectively. All of these cover the respective required system bandwidths. The measured 3 dB axial ratio bandwidths were 11.7 MHz(0.74%) and 14 MHz(1.14%), respectively. Within each of the designed bands, broadside radiation patterns were observed.

• Korean Journal of Environmental Biology
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• v.18 no.2
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• pp.263-268
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• 2000

The effect of $Cd^{2+}$ on stomatal apertures of epidermal strips and intact leaves in Commelina communis L. was investigated. Cadmium stimulated stomatal opening. The stomata, treated with 100 $\mu$M $Cd^{2+}$ opened to a degree of about 8.38 fm, but the stomata, treated with no cadmium opened to 3.74 ${\mu}{\textrm}{m}$. In order to show that there was no mechanical or osmotic impediment preventing the stomata in the epidermal strips, salicylic acid (SA) and abscisic acid (ABA) were used. The treatment of 100 $\mu$M SA and 1 $\mu$M ABA inhibited 14% and 28% of stomatal opening, respectively. Other heavy metals such as $Al^{3+} and Ag^{2+}$ were also used to investigate the effect of the stomatal apertures. The treatment of $Al^{3+} and Ag^{2+}$ also stimulated 19% and 41% of stomatal opening. To understand how cadmium open stomata, the effect of cadmium on the K+ influx into the epidermal strips was investigated. $Cd^{2+}$, SA, ABA inhibited 98%, 28%, 34% of K+ uptake respectively. 3-weeks old Commelina was transferred to and grown in Hoagland solution (0,5 mM $Cd^{2+}$, 10 mM $Cd^{2+}$) for 4 days and stomatal conductance were measured. The treatment of 5 mM $Cd^{2+}$ and 10 mM $Cd^{2+}$ showed about 51% and 70% inhibition of stomatal conductance, respectively Therefore, it could be concluded that stomata in epidermal strips and intact leaves behaved differently and cadmium- stimulated stomatal opening was due to the result of cadmium uptake into the epidermal strips instead of K+. [cadmium, stomata, stomatal conductance]

• Journal of Plant Biology
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• v.37 no.2
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• pp.245-252
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• 1994

Pollens of 20 species of Sedum were investigated with a scanning electron microscope. The pollen morphology of Sedum was rather variable, within particular species or even within a single inflorescence. Differences occurred in the number and shape of apertures and surface sculpture. Besides 3-colporate, various aperture types including 2-syncolporate, 3-syncolporate, 40stephanocolporate, 5-stephanocolporate, zonate, and irregular types were found in a single specimen. Also, striate-rugulose and psilate sculpture were found in S. viviparum. No correlation was found between the pollen morphology and the floral formula. Pollen characters appeared to be not useful for infrageneric classification of Korean Sedum.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.473-476
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• 2006

Microcavity plasma devices having characteristic dimensions below $100\;{\mu}m$ have been investigated as a candidate for the next generation of plasma displays. Arrays of inverted pyramid microcavity devices, fabricated in Si with emitting apertures of $(50\;{\mu}m)^2$ and designed for AC or bipolar excitation, demonstrate a luminous efficacy above 6 lm/W at pressures up to and beyond one atmosphere of Ne/Xe mixtures. Also the design of analogous microplasma devices in ceramic multilayer structures or plastic substrates is disccussed.

• 보존과학연구
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• s.16
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• pp.139-154
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• 1995

In this paper the fundamental elements relevant to schematic daylighting design for museum are discussed and suggested. The illuminance difference between outdoor and exhibition space in consideration of the constraints necessary for the conservation of artifacts can be solved by conversion into Luminance. Also it is considered that transition zone in two stages should be provided for adaption before entering exhibition space and overall luminance within the visual field along viewing circulation should be balanced including the apertures designed for introducing the daylight or visual linking.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.28.3-29
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• 2015

$Ly{\alpha}$ nebulae, or "$Ly{\alpha}$ blobs", are extended (~100 kpc), bright (L[$Ly{\alpha}$] ~ 1044 erg/s) clouds of $Ly{\alpha}$-emitting gas. The origin of the $Ly{\alpha}$ emission remains unknown, but recent theoretical work suggests that measuring the polarization could discriminate among powering mechanisms. we will discuss current status of $Ly{\alpha}$ polarization observations at high-redshift and our on-going survey program. We will present the first narrow-band, imaging polarimetry of a $Ly{\alpha}$ blob, B3 J2330+3927 at z=3.09, with an embedded, radio-loud AGN (C. You et al. in prep.). The AGN lies near the blob's $Ly{\alpha}$ emission peak and its radio lobes align roughly with the blob's semi-major axis. With the SPOL polarimeter on the MMT telescope, we map the polarization in a grid of circular apertures of radius 0.6" (4.4 kpc), detecting a significant (>$2{\sigma}$) polarization fraction P% in 10 apertures and achieving strong upper-limits (as low as 2%) elsewhere. The degree of the polarization map increases from P% ~ 5% at ~5 kpc from the blob center to ~20% at the outer part (~30 kpc). The detections are distributed asymmetrically, roughly along the blob's major axis. The polarization angles (${\Theta}$) are mostly perpendicular to this axis. These results are consistent with the picture that $Ly{\alpha}$ photons produced at the AGN (or the host galaxy) are resonantly scattered away from the center. Higher polarization fraction on the radio jet suggests that the gas is more optically thin along the jet than the off-axis region.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.328-336
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• 1999

To characterize the hydro-mechanical behavior of a rock joint, a rotary shear testing apparatus was devised in this study. Shear stress was driven by twisting the end of a sample in the rotary shear testing apparatus. The test results show that the rotary shear test underestimates the peak shear strength of a rock joint. The torque is known as a function of the radial distance from the axis of rotation, resulting in the radial variation of the shear stress. Fluid flow through rock joints is mainly dependent on the Joint roughness, contact area, initial aperture. To examine the dependency, the relationship between the hydraulic and the mechanical apertures for shear-flow was established by measuring the initial aperture. It shows that the mechanical aperture and the hydraulic aperture increase linearly with the dilatancy. The difference between the hydraulic and mechanical apertures describes the deviation from the behavior predicted by the parallel plate model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.675-682
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• 2011

This paper presents two ground plane effects due to the size of two rectangular apertures for two-wire transmission line with equal line length crossing the changeable rectangular apertures in infinite ground planes. The CST MWS is used to determine the characteristics of the insertion loss of the transmission line from the load section in accordance with the ground plane aperture size. The results show that the insertion gain and the insertion loss are periodically observed for the multiple frequency of the half wavelength resonance by the wire length when the transmission line is nearby to horizontal side or vertical side of the aperture. The measurements of the insertion loss are performed to verify the theoretical analysis.

• Journal of Biomedical Engineering Research
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• v.23 no.6
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• pp.419-430
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• 2002

In this paper. we propose an efficient method for implementing hi-directional pixel-based focusing(BiPBF) based on a sparse array imaging technique. The proposed method can improve spatial resolution and frame rate of ultrasound imaging with reduced hardware complexity by synthesizing transmit apertures with a small number of sparsely distributed subapertures. As the distance between adjacent subapertures increases, however. the image resolution tends to decrease due to the elevation of grating lobes. Such grating lobes can be eliminated in conventional synthetic aperture imaging techniques. On the contrary, grating lobes arisen from employing sparse synthetic transmit apertures can not be eliminated, which has been shown analytically in this paper. We also propose the condition and method for suppressing the grating lobes below -40dB, which is generally required in practical imaging. by placing the transmit focal depth at a near depth and properly selecting the subaperture distance in Proportion to receive aperture size. The results of both the Phantom and in vivo experiments show that the proposed method implements two-wav dynamic focusing using a smaller number of subapertures, resulting in reduced system complexity and increased frame rate.