• Journal of The Korean Astronomical Society
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• v.34 no.2
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• pp.59-66
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• 2001

In this paper, we investigate the correlation between the radial ultraviolet color distribution and the shapes of the ultraviolet isophote for elliptical galaxies (M32, NGC 1399) and spiral bulges (of M31, M81) by using their archival UIT images. For M31, M81, and NGC 1399, the radial ultraviolet color distributions show a two-component trend; as the distance from the galactic center increase the color becomes redder in the inner region while it becomes bluer in the outer region. On the other hand, the color of M32 continues to become bluer with the increasing galactocentric distance. We also find, unlike the optical/IR images, significant variations of the position angle and the ellipticity in the ultraviolet isophotes of M31, M81, and NGC 1399 through the inner regions. For M32, the variation is significant in the outer region. Since these variation implies the triaxiality of their intrinsic shapes, we suggest that the early-type galaxies and spiral bulges with a radial color gradient in ultraviolet tend to have a triaxiality. On the other hand, the shape parameter characterized by the fourth order cosine Fourier coefficient of the isophote, a(4)/a, indicates that the systematic deviations of the ultraviolet isophotes of the four galaxies are smaller than $\~0.2\%$ in units of the semi-major axis. The latter result implies that the ultraviolet isophotes of the galaxies have a pure elliptical shape rather than the boxy or disky shapes. Therefore, there is no clear evidence of correlation between the radial ultra-violet color gradient and the boxy/disky shapes of isophotes.

• Publications of The Korean Astronomical Society
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• v.25 no.4
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• pp.113-118
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• 2010

The Henyey-Greenstein (H-G) phase function, which is characterized by a single parameter, has been generally used to approximate the realistic dust-scattering phase function in investigating scattering properties of the interstellar dust. Draine (2003) proposed a new analytic phase function with two parameters and showed that the realistic phase function is better represented by his phase function. If the H-G and Draine's phase functions are significantly different, using the H-G phase function in radiative transfer models may lead to wrong conclusions about the dust-scattering properties. Here, we investigate whether the H-G and Draine's phase functions would indeed produce significant differences in radiative transfer calculations for two simple configurations. For the uniformly distributed dust with an illuminating star at the center, no significant difference is found. However, up to ~ 20% of difference is found when the central star is surrounded by a spherical-shell dust medium and the radiation of $\lambda$ < $2000\;{\AA}$ is considered. It would mean that the investigation of dust-scattering properties using the H-G phase function may produce errors of up to ~ 20% depending on the geometry of dust medium and the radiation wavelength. This amount of uncertainty would be, however, unavoidable since the configurations of dust density and radiation sources are only approximately available.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.118.2-118.2
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• 2012

In particle-in-cell (PIC) simulation studies related to ion-ion two-stream instability, a reduced ion-to-electron mass ratio is often employed to save computation time. But it was not clearly verified how electrons dynamics are coupled with the slower evolution of ion-ion interactions under the external electric field. We have studied the ion beam driven instability using a 1D electrostatic PIC code by comparing different rescaling of parameter with real ion mass from the reference simulation with reduced ion mass. As the external electric field is stronger, the excited unstable mode range was more sensitively affected by the system size with the real mass ratio than the reduced ion mass. The results show that the reduced mass ratio should be used cautiously in PIC code as the electron dynamics can modify the ion instabilities. Additionally we found the formation of electron flat-top distribution in the final saturation stage. Simulation results show that in the early phase electrostatic solitary waves are quasi-periodically formed, but later they are fully dissipated resulting in heated, flat-top distributions. New electron beam components are occasionally formed. These are a consequence of the interaction with solitary wave structures. We parametrically investigate the development of electron phase space distributions for various drift speeds of ion beams and temperature ratios between ions and electrons

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.36.1-36.1
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• 2011

It is generally believed that eruptive phenomena in the solar atmosphere such as solar flares and coronal mass ejections (CMEs) occur in the solar active regions with complex magnetic structures. Magnetic helicity has been recognized as a useful parameter to measure the complexity such as twists, kinks, and inter-linkages of magnetic field lines. The objective of this study is to understand a long-term (a few days) variation of magnetic helicity in active regions and its relationship with the energy buildup and instability leading to flares and CMEs. Statistical studies of flare productivity and magnetic helicity injection in about 400 active regions were carried out. The temporal variation of magnetic helicity injected through the photosphere of active regions was also examined related to 46 CMEs. The main findings in this study are as follows: (1) the study of magnetic helicity for active regions producing major flares and CMEs indicates that there is always a significant helicity injection through the active-region photosphere over a long period of 0.5 - a few days before the flares and CMEs; (2) for the 30 CMEs under investigation, it is found that there is a fairly good correlation (linear correlation coefficient of 0.71) between the average helicity injection in the CME-productive active regions and the CME speed. Beside the scientific contribution, a major impact of this study is the observational discovery of a characteristic variation pattern of magnetic helicity injection in flare/CME-productive active regions which can be used for the improvement of solar eruption forecasting.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1402-1413
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• 2004

In non-rigid image registration, the Jacobian determinant of the estimated deformation should be positive everywhere since physical deformations are always invertible. We propose a constrained optimization technique at ensures the positiveness of Jacobian determinant for cubic B-spline based deformation. We derived sufficient conditions for positive Jacobian determinant by bounding the differences of consecutive coefficients. The parameter set that satisfies the conditions is convex; it is the intersection of simple half spaces. We solve the optimization problem using a gradient projection method with Dykstra's cyclic projection algorithm. Analytical results, simulations and experimental results with inhale/exhale CT images with comparison to other methods are presented.

• Journal of Microbiology and Biotechnology
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• v.16 no.4
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• pp.647-650
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• 2006

D-Psicose 3-epimerase (DPE) catalyzes the interconversion of D-fructose to D-psicose by epimerizing the carbon-3 position. The DPE from Agrobacterium tumefaciens was cloned and expressed in Escherichia coli. The expressed enzyme was purified by affinity chromatography on an IMAC, gel filtration chromatography on a Sephacryl S-300 HR, and anion-exchange chromatography on a RESOURCE Q. The molecular mass of the purified enzyme was estimated to be about 135 kDa by Superdex 200 gel filtration chromatography, corresponding to a homotetramer. The enzyme produced crystals suitable for X-ray diffraction to a $2.0{\AA}$ resolution at 100 K. The crystals were found to belong to the orthorhombic space group $P2_12_12_1$, with unit-cell parameters a=102.4, b=113.0, and $c=131.8{\AA}$. In addition, the calculated packing parameter $(V_m)$ was $2.79{\AA}^3/Da$, the solvent content was 55.92%, and an asymmetric unit consisted of four monomers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.578-582
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• 2005

This paper describes MAC schemes for QoS enhancement taking into account the traffic characteristics and network states over IEEE 802.11 wireless networks. Our approach uses AR as a Backoff parameter and to slide IFS adaptively for increasing the medium utilization ratio and throughput, and providing fairness. In addition, we evaluate through simulations using NS-2 the performance of proposed MAC scheme and compare it with other MAC schemes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.8
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• pp.1955-1961
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• 2013

Paranasal sinuses of the empty space is filled with air that exists in the bones in the face. However, the pus becomes inflamed paranasal sinuses sinusitis onset brings the voice of change, and complained of headaches and lethargy. Therefore, in this paper, paranasal sinuses related diseases to predict voice analysis parameter as measured by changes in paranasal sinuses through external stimuli is investigated and carried out a study to analysis the function consisting of the frontal sinus, ethmoid sinus, maxillary sinus, sphenoid sinus. From this, cold pack stimulation in the paranasal sinus area for stimulation before and after voice was performed by measuring formant frequency and external stimuli through correlation analysis of the mutual impact on paranasal sinuses were analyzed.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.1
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• pp.20-23
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• 2006

This paper presents a new approach to the problem of designing a cascaded three-parameters controller for a given linear time invariant (LTI) plant in unity feedback system. We consider a proportional-integral-derivative (PID) and a first-order controller with the specified overshoot and settling time. This problem is difficult to solve because there may be no analytical solution due to the use of low-order controller. Furthermore, the zeros of controller just appear in the zeros of feedback system. The key idea of our method is to impose a constraint on the controller parameters so that the zeros of resulting controller are distant from the dominant pole of closed-loop system to the left as far as the given interval. Two methods realizing the idea are suggested. We have employed the characteristic ratio assignment (CRA) in order to deal with the time response specifications. It is noted that the proposed methods are accomplished only in parameter space. Several illustrative examples are given.

• Transactions of the Society of Information Storage Systems
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• v.10 no.2
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• pp.50-54
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• 2014

Object image using DRPE(Double Random Phase Encryption) in 4f system is encrypted by space-division method using amplitude mask. However, this method has the weakness for the case of having partial data of amplitude mask which can access the original image. To improve the security, we propose the method using the 2-dimension logistic chaos function which shuffles the encrypted data. It is shown in simulation results that the proposed method is highly sensitive to chaos function parameters. To properly decrypt from shuffled encryption data, below 1e-5 % errors of each parameter should be required. Thus compared with conventional method the proposed shows the higher security level.