• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제17권5호
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• pp.61-69
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• 2017

The study on interference channel is very important information theoretically and many studies have been done on it. However, even in the simplest case, even in the case of two user interfering channels, the channel capacity is not yet known except in special cases. Recently, research on the multiplexing gain that shows the tendency of the transmission rate in the high signal to noise ratio (SNR) band has been actively carried out, instead of accurately grasping the channel capacity. Obtaining optimal multiplexing gain can reveal trends in channel capacity at high signal-to-noise ratio bands. In an interfering channel with two users, the best multiplexing gain can be obtained by eliminating the interference. However, recent research shows that when the number of users is more than three, the optimal multiplexing gain can not be obtained only by zero forcing and a new technique called interference sorting is needed. There are two types of interference sorting techniques. Beamforming A method of effectively separating signals and interference by properly selecting matrices and constructing structured codes using rational numbers and irrational numbers. The interference alignment technique can achieve optimal multiplexing gain in various environments such as interference channel, X channel, compound broadcast channel, and multi hop network for multi source multi destination. In recent years, it has also been applied to distributed storage. Lee et al., "Lattice Code Interference Alignment in Cooperative Multipoint Transmission (COMP) for Interference Channels of Three Users", Journal of the Institute of Electronics Engineers, vol.49-TC,no.6,2012. In this paper, the DoF of delayed channel information is obtained.

• Journal of Biomedical Engineering Research
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• 제37권2호
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• pp.90-103
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• 2016

This research was aimed to analyze load sharing ratios between cortical shell and trabecular bone of a degraded lumbar vertebra with aging, and also evaluate elastic moduli assigned into an FE model, using finite element method. For the better analysis of trabecular bone, effective elastic moduli, that is, nominal elastic moduli divided by the volumetric porosities was used. The elastic moduli of the cortical shell suitable for the trabecular bone were obtained from the equations on the basis of idealized stress-strain relations, including areal porosities. To minimize numerical errors, p-element was used. Using eight parameters that refer to some published papers, the geometry of L3 with a removed posterior part. After the constant compressive displacement was applied, the load sharing ratios were obtained by using both every elastic strain energy and every vertical force between two bones in each 8-volume. As results, 1) according to an increase in age from 20-year to 80-year, load sharing ratios of trabecular bone decreased from 55% to 49%; 2) the maximal ratios of each bone were occurred in the mid-plane of centrums and the endplate of cortical shells, respectively; 3) effective elastic moduli assigned into a porous centrum/cortex were found to be adequate; 4) for load sharing ratios, the difference of two methods showed that the total ratios were almost same within less than 1% but the partial ratios at every depth were more or less different each other.

• Journal of the Korean Vacuum Society
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• 제14권3호
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• pp.138-142
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• 2005

We tested performance of the 4C1 beamline for analyzing structures of proteins in solution using small angle X-ray scattering (SAXS) at the Pohang Light Source(PLS). Structurally well-known proteins such as lysozyme and $Bcl-XL(\vartriangle TM/\vartriangle loop)$ were used for the study. Low resolution solution structures of lysozyme and $Bcl-XL(\vartriangle TM/\vartriangle loop)$ were obtained at a resolution of at least i.2 nm, and the structures were basically same as those calculated from the crystal structures of the proteins. We also used $Bcl-XL(\vartriangle TM/\vartriangle loop)$ with a long flexible loop attached [$Bcl-XL(\vartriangleTM))$] and obtained significantly different data from $Bcl-XL(\vartriangle TM/\vartriangle loop)$, although the electron density map of the loop is known to be invisible from the crystal structure of $Bcl-XL(\vartriangleTM))$. We confirm that SAXS experiment is a powerful tool for the structural study of proteins in solution and the 4Cl beamline at the PLS is well-equipped and suitable for the protein solution SAXS experiment.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제5권4호
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• pp.777-790
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• 2001

Theoretical analyses have been tried to design high power and stable operating SLD at 1.55${\mu}{\textrm}{m}$ wavelength range which is the lowest absorption wavelength in optical fiber. The materials of active layer and SCH layer were chosen as conventional In1-xGaxAsyPl-y quaternary composition systems. From the transverse mode and the lateral mode analyses of waveguide, the optical power distributions and the optical confinement factor have been studied for single-mode high power operation. According to these analyses, it was calculated the composition and the thickness of SCH layer to obtain the maximum optical confinement factor. In order to obtain low values of the reflectivity, we used the window region and the lateral tilted angle between tile active region and window region. And the reflectivity of SLD was calculated with the gaussian beam approximation and mode analysis. From these researches, it was confirmed for several results to fabricate the efficient and stable SLD. In case of using $1.3\mum$, InGaAsP SCH layer, the layer thickness was obtained $0.08\mum$, to get the maximum optical confinement factor. Using $0.2\mum$, active layer thickness and $0.08\mum$, SCH layer thickness, the window region length is about $100\mum$ without An coating, $10\mum$ in 1% AR coating to obtain about 10-4 reflectivity. When the tilted angle is about $10~15^{\circ}$, the reflectivity is about 10-3. From these results, if the window region length and tilted angle were controlled appropriately in given device structure, it was confirmed that it is possible to fabricate the stable SLD without AR coating analytically.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제20권4호
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• pp.489-496
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• 2019

This paper is a study on the evaluation of loss factor of damping treatment materials to reduce the noise and vibration for panels of railway vehicles and automobiles. In order to determine the modal parameters of damping materials, beam excitation tests were carried out using different type PVC coated aluminum and steel base beam specimens. The specimens were excited from 10 Hz to 1000 Hz frequency range using sinusoidal force, and transfer mobility data were measured by using an accelerometer. The loss factors were determined by using integrated program, based on theories of Half Power Method, Minimum Tangent Error Method, Minimum Angle Error Method and Phase Change Method, which enable to evaluate the parameters using modal circle fit and least squares error method. In the case of lower loss factor and data of linear characteristics, any method could be applied for evaluation of parameters, however the case of higher loss factor or data including non-linear characteristics, the minimum angle error method could reduce the loss factor evaluation. The obtained dynamic properties of the coating material could be used for application of Finite Element Method analyzing the noise control effects of complex structures such as carbody or under-floor boxes of rolling stock. The damping material will be very useful to control the structural noise, because the obtained modal loss factors of each mode show very good effect on over $2^{nd}$ mode frequency range.

• Korean Journal of Optics and Photonics
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• 제33권5호
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• pp.201-209
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• 2022

The previously developed microspot spectroscopic ellipsometer (SE) is upgraded to a microspot SE compatible with the atomic force microscope (AFM). The focusing optical system of the previous microspot SE is optimized to incorporate an AFM head. In addition, the rotating compensator ellipsometer in polarizer-sample-compensator-analyzer configuration is adopted in order to minimize the negative effects caused by beam wobble. This research leads to the derivation of the expressions needed to get spectro-ellipsometric constants despite the fact that the employed rotating compensator is far from the ideal achromatic quarter-wave plate. The spot size of the developed microspot SE is less than 20 ㎛ while the AFM head is mounted. It operates in the wavelength range of 190-850 nm and has a measurement accuracy of δΔ ≤ 0.05° and δΨ ≤ 0.02°, respectively. Fast measurement of ≤3 s/sp is realized by precisely synchronizing the azimuthal angle of a rotating compensator with the spectrograph. The microspot SE integrated with an AFM is expected to be useful in characterizing the structure and optical properties of finely patterned samples.

• Journal of the Korean Society of Radiology
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• 제16권6호
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• pp.719-725
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• 2022

This study aimed to measure, quantitatively evaluate, and set the criteria for the minimum lead(Pb) shield thickness per level of clinically applied electron beam energy. The lead shield thickness per electron beam energy was measured using the primary field 95% reduction based on the open field at the depth of maximum dose (d_max) and depth from the surface as the reference depth of tissue dose(10 mm). The measured values were 1.906 mmPb and 1.992 mmPb at the d_max and 10 mm, respectively, regarding the lead shield thickness for 6 MeV electron beam; 2.746 mmPb and 3.743 mmPb for 9 MeV electron beam, 3.718 mmPb and 6.093 mmPb for 12 MeV electron beam, 7.300 mmPb and 15.270 mmPb for 16 MeV electron beam, and 16.825 mmPb and 25.090 mmPb for 20 MeV electron beam. Consequently, a thicker lead shield was required if the measurement was at 10 mm. The required lead shield thickness was also higher than that of the theoretical formula for electron beams of ≥ 16 MeV.

• Progress in Medical Physics
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• 제20권4호
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• pp.290-297
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• 2009

In case of radiation treatment using small field high-energy photon beams, an accurate dosimetry is a challenging task because of dosimetrically unfavorable phenomena such as dramatic changes of the dose at the field boundaries, dis-equilibrium of the electrons, and non-uniformity between the detector and the phantom materials. In this study, the absorbed dose in the phantom was measured by using an ion chamber and a diode detector widely used in clinics. $GAFCHROMIC^{(R)}$ EBT films composed of water equivalent materials was also evaluated as a small field detector and compared with ionchamber and diode detectors. The output factors at 10 cm depth of a solid phantom located 100 cm from the 6 MV linear accelerator (Varian, 6 EX) source were measured for 6 field sizes ($5{\times}5\;cm^2$, $2{\times}2\;cm^2$, $1.5{\times}1.5\;cm^2$, $1{\times}1\;cm^2$, $0.7{\times}0.7\;cm^2$ and $0.5{\times}0.5\;cm^2$). As a result, from $5{\times}5\;cm^2$ to $1.5{\times}1.5\;cm^2$ field sizes, absorbed doses from three detectors were accurately identified within 1%. Wheres, the ion chamber underestimated dose compared to other detectors in the field sizes less than $1{\times}1\;cm^2$. In order to correct the observed underestimation, a convolution method was employed to eliminate the volume averaging effect of an ion chamber. Finally, in $1{\times}1\;cm^2$ field the absorbed dose with a diode detector was about 3% higher than that with the EBT film while the dose with the ion chamber after volume correction was 1% lower. For $0.5{\times}0.5\;cm^2$ field, the dose with the diode detector was 1% larger than that with the EBT film while dose with volume corrected ionization chamber was 7% lower. In conclusion, the possibility of $GAFCHROMIC^{(R)}$ EBT film as an small field dosimeter was tested and further investigation will be proceed using Monte Calro simulation.

• Journal of Korean Tunnelling and Underground Space Association
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• 제11권1호
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• pp.57-70
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• 2009

Considerable advance has been made on research on effect of steel pipe Umbrella Arch Method (UAM) and mechanical reinforcement mechanism through numerical analyses and experiments. Due to long analysis time of three-dimensional analysis and its complexity, un-quantitative two-dimensional analysis is dominantly used in the design and application, where equivalent material properties of UAM reinforced area and ground are used, For this reason, development of reasonable, theoretical, quantitative and easy to use design and analysis method is required. In this study, both field UAM tests and laboratory tests were performed in the residual soil to highly weathered rock; field tests to observe the range of reinforcement, and laboratory tests to investigate the change of material properties between prior to and after UAM reinforcement. It has been observed that the increase in material property of neighboring ground is negligible, and that only stiffness of steel pipe and cement column formed inside the steel pipe and the gap between steel pipe and borehole contributes to ground reinforcement. Based on these results and concept of Convergence Confinement Method (CCM), two dimensional axisymmetric analyses have been performed to obtain the longitudinal displacement profile (LDP) corresponding to arching effect of tunnel face, UAM effect and effect of supports. In addition, modified load distribution method in two dimensional plane-strain analysis has been suggested, in which effect of UAM is transformed to internal pressure and modified load distribution ratios are suggested. Comparison between the modified method and conventional method shows that larger displacement occur in the conventional method than that in the modified method although it may be different depending on ground condition, depth and size of tunnel, types of steel pipe and initial stress state. Consequently, it can be concluded that the effect of UAM as a beam in a longitudinal direction is not considered properly in the conventional method.