• Journal of the Institute of Convergence Signal Processing
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• v.6 no.4
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• pp.198-205
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• 2005

In this paper, the miniaturization of aperture-coupled RHCP patch antenna for the GPS system is treated. Circularly polarization characteristics is implemented by truncating diagonal corners of the square patch. Antenna size is reduced by inserting four uniform slits at the patch edges, which was equivalently lengthened the surface current by meandering it, This antenna uses aperture-coupled feeding structure with crossed-slot shape in order to give easy miniaturization of RHCP patch antenna. Simulated and measured results show that $42.7\%$ lower antenna size is obtained, and also $56\%$ lower -10dB bandwidth and $38.5\%$ lower 3dB AR bandwidth are obtained. when the proposed design scheme is applied to a commercial GPS antenna structure, $42.9\%$ lower patch size and $56\%$ lower 3dB AR bandwidth compared to commercial antenna at the same frequency are obtained.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.113-120
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• 2007

The 5kWt dish solar collector is designed and the preliminary performance test for this is carried out. The diameter of the parabolic dish is 3.2 m, and its focal length is 2 m. It consists of 10 small reflectors which have their own curvatures, and the effective reflecting area is $5.9\;m^2$, and the rim angle of the dish is $43.85^{\circ}$. The reflectivity of reflectors is 0.95, and the thermal capacity of the system is about 5 kW thermal. The aperture diameter of the cylindrical-shape receiver which is made of stainless steel is 100 mm, and the height is 210 mm. A quartz window is installed at the receiver aperture to minimize the convective heat loss and prevent air leakage. In order to increase the heat transfer area, porous materials (nickel-alloy) are inserted into the receiver. Air flows into the upper part of the receiver which is the opposite side of the aperture. After the air flows through the inside of the receiver, that goes out of the receiver through 3 exits which are located near the aperture. The volumetric flow rates of air are varied from 600 to 1200 L/min. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.56.2-56.2
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• 2016

We present a multi-aperture photometry pipeline for DEEP-South (Deep Ecliptic Patrol of the Southern Sky) time-series data, written in C. The pipeline is designed to do robust high-precision photometry and calibration of non-crowded fields with a varying point-spread function, allowing for the wholesale search and characterization of both temporal and spatial variabilities. Our time-series photometry method consists of three parts: (i) extracting all point sources with several pixel/blind parameters, (ii) determining the optimized aperture for each source where we consider whether the measured flux within the aperture is contaminated by unwanted artifacts, and (iii) correcting position-dependent variations in the PSF shape across the mosaic CCD. In order to provide faster access to the resultant catalogs, we also utilize an efficient indexing technique using compressed bitmap indices (FastBit). Lastly, we focus on the development and application of catalog-based searches that aid the identification of high-probable single events from the indexed database. This catalog-based approach is still useful to identify new point-sources or moving objects in non-crowded fields. The performance of the pipeline is being tested on various sets of time-series data available in several archives: DEEP-South asteroid survey and HAT-South/MMT exoplanet survey data sets.

• Laser Solutions
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• v.6 no.3
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• pp.19-28
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• 2003

The manufacturing process for the microfluidic device can include sequential steps such as master fabrication, electroforming, and injection molding. The laser ablation, using masks, has been applied to the fabrication of channels in microfluidic devices. In this research, an excimer laser was used to engrave microscopic channels on the surface of PET (polyethylene terephthalate), which shows a high absorption ratio for an excimer laser beam with a wavelength of 248 m. When 50-${\mu}{\textrm}{m}$-wide rectangular microscopic channels are ablated with a 500 ${\times}$ 500 ${\mu}{\textrm}{m}$ square mask at a magnification ratio of 1/10, ditch-shaped defects were found in both corners. The measurement of laser beam intensity showed that a coherent image in the PET target caused such defects. Analysis based on the Fourier diffraction theory enabled the prediction of the coherent shape at the image surface as well as the diffraction beam shape between the mask and the image surface. It also showed that the diameter of the aperture had a dominant effect. The application of aperture with a diameter of less than 3 mm helped to eliminate such defects in the ablated rectangular microscopic channels on PET without such ditch-shaped defects.

• 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.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.299-304
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• 1996

We numerically determined the direction of ray and the average ray-crossing position from the shape of the wavefront on the exit pupil of optical system which had aberrations and apodized aperture. This position was calculated easier and closer to the position of the maximum intensity than that calculated by Safa's method when the aberration is greater than about 2λ.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.383-386
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• 2002

The goal of this study is to realize the PBG lowpass filter using novel PBG structure modification both upper layer and ground layer. It has been designed three aperture slots of ground layer for PBG structure which the center slot shape of ground is two type, rectangular and dumbbell. This PBG LPF llas the character of the broader stopband and smaller size than typical LPF. The measurement results have matched the simulated ones. It has the cutoff frequency of each 4.4650Hz and 3.520Hz and at least -2OdB of the signal suppression at the stopband.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.502-507
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• 2013

In this paper, a circular dual mode horn with modified aperture is proposed to improve a E/H-plane radiation pattern symmetry of a conventional oversized circular dual mode horn. The proposed antenna consists of a feeding section, a mode generation section and a phase matching section which has aperture shape transition from circle to ellipse or rectangle to improve a E/H-plane radiation pattern symmetry. To compare the performances between the proposed antenna and the convenional circular dual mode horn, the conventional circular dual mode horn and the proposed circular dual mode horn with rectangular aperture are fabricated and researched at 15 GHz. The measured results show that the conventional circular dual mode horn has 3.394 dB difference while the proposed antenna has only 0.539 dB difference between E and H-plane radiation patterns within the -11 dB beamwidth($53^{\circ}$) which is required beamwidth of the feed horn for the maximum aperture efficiency where f/d ratio of reflector antenna is 1.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.99-101
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• 2000

The fabrication of the submicron size hole has been interesting due to the potential application of the near field optical sensor or liquid metal ion source. The 2 micron size dot array was photolithographically patterned. After formation of the V-groove shape by anisotropic KOH etching, dry oxidation at $1000^{\circ}C$ for 600 minutes was followed. In this procedure, the orientation dependent oxide growth was performed to have an etch-mask for dry etching. The reactive ion etching by the inductively coupled plasma (ICP) system was performed in order to etch ~90 nm $SiO_2$ layer at the bottom of the V-groove and to etch the Si at the bottom. The negative ion energy would enhance the anisotropic etching by the $Cl_2$ gas. After etching, the remaining thickness of the oxide on the Si(111) surface was measured to be ~130 nm by scanning electron microscopy. The etched Si aperture can be used for NSOM sensor.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.133-141
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• 2007

The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition, displacement, groundwater flow conditions have been altered due to the processes induced by the excavation. Various studies have been carried out on EDZ, but most studies have focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the 'hydraulic EDZ' was defined as the rock zone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation by using H-M coupling analysis. Fundamental principles of distinct element method (DEM) were used in the analysis. In the same groundwater level, the behavior of hydraulic aperture near the cavern was analyzed for different stress ratios, initial apertures, fracture angles and fracture spacings by using a two-dimensional DEM program. We evaluate the excavation induced hydraulic aperture change. Using the results of the study, hydraulic EDZ was defined as an elliptical shape model perpendicular to the joint.