• Ocean and Polar Research
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• v.36 no.4
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• pp.319-326
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• 2014

Mineral dust in the polar snow plays an important role both in the climate system of the Earth and in global biogeochemical cycles. Analysis of the concentration and the particle size distribution of mineral dust has been carried out in the snow from the Antarctic surface snow and the Greenland snowpit. Among the various particle size determination techniques, a Multisizer 3 Coulter Counter in a class 100 clean bench counted all particles between 1.1 and $30.0{\mu}m$ with a $50{\mu}m$ aperture tube. The aperture tube size, the concentration of electrolytes and the accuracy of the particle size distribution were determined in this study. The number concentrations from the Antarctic surface snow were 81,843 particles $mL^{-1}$, but those from the Greenland snowpit were 10,666 particles $mL^{-1}$. In the volume distribution, the distributions of mineral dust in both the Antarctic surface snow and the Greenland snowpit showed lognormal distribution in the size interval 1.1 to $6.0{\mu}m$ with the mode, 3.562 and $3.836{\mu}m$, respectively. The analysis technique using a coulter counter for mineral dust could be used for reconstructing paleoclimates from polar ice cores.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1015-1022
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• 2023

In this paper, we propose DLP(Dual Linear Polarization) antenna with aperture coupled feeding structure for private network. The proposed antenna has general aperture coupled structure and design two port between top and bottom layer to obtain the enhanced isolation. Also, The size of each substrate(top and bottom layer) is 34.0 mm(W)×34.0 mm(L), which is designed on the FR-4 substrate which thickness (h) is 1.0 mm, and the dielectric constant is 4.4. Also, the size of patch antenna is 12.70 mm(W2)×14.60 mm(L3), and it is located on the top layer. The size of feeding line is 24.0 mm(W2)×1.6 mm(L3), and is located at the bottom layer Also, rectangular slot is located on the ground plane between top layer and bottom layer. From the fabrication and measurement results, bandwidths of 300 MHz (4.52 to 4.82 GHz) for feeding port 1, and 170 MHz (4.65 to 4.82 GHz) for feeding port 2 are obtained on the basis of -10 dB return loss and transmission coefficient S21 is got under the -30 dB. Also, cross polarization isolation between each feeding port obtained

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.70-74
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• 2015

In this paper, satellite communication based video surveillance system that consisted of ultra-small aperture terminals with small-size smart vision sensor is proposed. The events such as forest fire, smoke, intruder movement are detected automatically in field and false alarms are minimized by using intelligent and high-reliable video analysis algorithms. The smart vision sensor is necessary to achieve high-confidence, high hardware endurance, seamless communication and easy maintenance requirements. To satisfy these requirements, real-time digital signal processor, camera module and satellite transceiver are integrated as a smart vision sensor-based ultra-small aperture terminal. Also, high-performance video analysis and image coding algorithms are embedded. The video analysis functions and performances were verified and confirmed practicality through computer simulation and vision sensor prototype test.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.122-132
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• 1999

In this paper, a shaped small-size ADE(Axially Displaced Ellipse) reflector antenna of 30 cm in diameter operating from 37 to 40 GHz was designed. The experimental antenna was manufactured, and the radiation characteristics evaluated. In the procedure of antenna design, aperture field distribution was assumed to uniform + parabolic distribution. And the variations of beam width, aperture efficiency, and sidelobe level as functions of aperture field distributions were investigated, and these results presented to be used in antenna design. The measured gain and sidelobe level of experimental antenna were found 39.9 dBi(efficiency : 61.9%) and -18.8 dB for 40 GHz. These values show good agreement in design goal of efficiency more than 60% and sidelobe level less than -20 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.11
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• pp.1161-1169
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• 2003

In this paper, ADE(Axially Displaced Ellipse) Gregorian dual reflector antennas, which are the special form of Gregorian dual reflector antennas, were analyzed. In the procedure of antenna analysis, the aperture field distribution was obtained by using the geometrical optics and their far-field radiation characteristics were analyzed by using the aperture field method. The analysis results such as antenna efficiency, HPBW(Half Power Beam Width), FNBW(First Null Beam Width), and FSL(First Sidelobe Level) were presented as functions of edge taper and size of main reflector and subreflector. From the results in this paper, we could confirm that ADE reflector antennas have the different radiation characteristics from the classical dual reflector antennas.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.104-109
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• 2014

Purpose: Conventional pinhole scintigraphy offers a high resolution and generally use for thyroid scan or bone scintigraphy. the aim of this study is to evaluate performance of each aperture according to the diameter size. Materials and Methods: In this study 2 mm, 4 mm, 6 mm, 8 mm diameter pinhole collimators were mounted on Siemens E.CAM systems. In order to evaluate performance evaluation of each aperture, we acquired projection image by using SPECT for evaluating FWHM, resolution test and static image for evaluating thyroid phantom test. Results: As a result of FWHM showed 2.2 mm FWHM, 3.2 mm FWHM, 5.4 mm FWHM, 7.5 mm FWHM per each aperture in the resolution test. SNR, uniformity, contrast were acquired result from thyroid phantom test comparing general image and delayed image. as a result of SNR showed 6.55, 8.47, 6.2, 5.23 in case of general image and 5.25, 5.01, 5.38, 5.82 in case of delayed image per each aperture. as a result of uniformity showed 0.152, 0.118, 0.161, 0.19 in case of general image and 0.19, 0.199, 0.185, 0.171 in case of delayed image per each aperture. as a result of contrast showed 1.31, 1.19, 1.15, 1.01 in case of general image and 1.09, 1.08, 1.04, 1 in case of delayed image per each aperture. Conclusion: Resolution and sensitivity were heavily influenced by aperture size. and also we found advantage of delayed image as a result of thyroid phantom test.

• The Journal of Engineering Geology
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• v.6 no.1
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• pp.1-13
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• 1996

The fracture transmissivity($T_f$) is the most important parameter of fracture in assessing groundwater flow in fractured rock masses by using the DFN(Discrete Fracture Network) modeling. $T_f$, the most sensitive parameter m DFN modeling, is dependent upon aperture, size and filling characteristics of each fracture set. In the field test, the accuracy of $T_f$ can be increased with Borehole Acoustic Scanning (Televiewer) and Fixed Interval Length(FIL) test in constant head. $T_f$ values measured from FIL test was modified and estimated by each fracture set on the basis of the Cubic Law and the information of aperture and filling characteristics obtained from Televiewer. The modified $T_f$ results in the increase of confidence and reliability of modeling results including the amount of tunnel inflow.And, this approach would reduce the uncertaintity of the assessment for groundwater flow in fractured rock masses using the DFN modeling.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.950-967
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• 1995

Acoustic holography makes it possible to reconstruct the acoustic field based on the measurement of the pressure distribution on the hologram surface. Because of the merit that one can obtain an entire three-dimensional wave field from the data recorded on a two-dimensional surface, the holographic method has been widely studied. Being an experimental method, holography has an unavoidable error which is generate by sampling in space and frequency domain and finite aperture size. Its magnitude is dependent on the space and frequency domain and finite aperture size. Its magnitude is dependent on the shape of hologram surface, acoustic holography may be classified into four types of holography : rectangular type planeholography, circular type plane holography, cylindrical holography and spherical holography. In this paper, four types of holography are studied by modal summation method. Numerical simulation is performed using a monopole source with varying parameters to find out effects to the estimation error in each holography. Experiments of circular type plane holography and cylindrical holography explain strong relation between the shape of hologram surface and the acoustic field.

• The Journal of the Acoustical Society of Korea
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• v.16 no.6
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• pp.12-18
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• 1997

Beamforming method has a limited spatial resolution because of finite aperture size, so that the estimated source distributions are smoothed within the resolution. Especially for low frequency noise such as mechanical noise, this limitation often diminishes the direct use of beamforming method. In this study, the relation between smoothed beamforming and radiation power distribution of plate has been addressed. By adjustment of aperture size of array, the smoothed beamforming power shows radiation power distribution of plate. Numerical simulations are carried for simply supported plate.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.72.3-72.3
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• 2019

The observation of transient objects such as supernovae or variable stars requires a survey of the wide sky and quickly extracting the results. In accordance with this purpose, we have been developing an automatic observing software, KAOS (Kyung Hee University Automatic Observing Software) as a series. KAOS30 was the first series of KAOS and it was applied to the 30-inch platform at the McDonald Observatory in the United States of America. KAOS76 controls the 76-cm telescope at Kyung Hee Astronomical Observatory. In this poster, we introduce KAOS10 for controlling a portable telescope with a small aperture size attaching a guiding camera as QHY-5L II. Kyung Hee University auto-guiding package which includes the auto-guiding function for small aperture size telescope was also developed. Additionally, the Telescope Control Package(TCP) can communicate with the main server to do astrometry for pointing and identifying targets efficiently. KAOS10 has a universal interface that will be useful for the research of both amateurs and professionals.