• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.303-314
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• 2004

In this paper we report some properties of inner magnetospheric structure inferred from the T01_s code, one of the latest magnetospheric models by Tsyganenko. We have constructed three average storms representing moderate, strong, and severe intensity storms using 95 actual storms. The three storms are then modelled by the T01_s code to examine differences in magnetic structure among them. We find that the magnetic structure of intense storms is strikingly different from the normal structure. First, when the storm intensity is large, the field lines anchored at dayside longitudinal sectors become warped tailward to align to the solar wind direction. This is particularly so for the field lines anchored at the longitudinal sectors from postnoon through dusk. Also while for the moderate storm the equatorial magnetic field near geosynchronous altitude is found to be weakest near midnight sector, this depression region expands into even late afternoon sector during the severe storm. Accordingly the field line curvature radius at the equator in the premidnight geosynchronous region becomes unusually small, reaching down to a value less than 500 km. We attribute this strong depression and the dawn-dusk asymmetry to the combined effect from the enhanced tail current and the westward expansion/rotation of the partial ring current.

• Journal of Astronomy and Space Sciences
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• v.38 no.2
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• pp.135-143
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• 2021

We report, for the first time, the afternoon (i.e., from noon to sunset time) observations of the northern mid-latitude E-region field-aligned irregularities (FAIs) made by the very high frequency (VHF) coherent backscatter radar operated continuously since 29 December 2009 at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude) in South Korea. We present the statistical characteristics of the mid-latitude afternoon E-region FAIs based on the continuous radar observations. Echo signal-to-noise ratio (SNR) of the afternoon E-region FAIs is found to be as high as 35 dB, mostly occurring around 100-135 km altitudes. Most spectral widths of the afternoon echoes are close to zero, indicating that the irregularities during the afternoon time are not related to turbulent plasma motions. The occurrence of afternoon E-regional FAI is observed with significant seasonal variation, with a maximum in summer and a minimum in winter. Furthermore, to investigate the afternoon E-region FAIs-Sporadic E (E_s) relationship, the FAIs have also been compared with E_s parameters based on observations made from an ionosonde located at Icheon (37.14°N, 127.54°E, 27.7°N dip latitude), which is 100 km north of Daejeon. The virtual height of E_s (h'E_s) is mainly in the height range of 105 km to 110 km, which is 5 km to 10 km greater than the bottom of the FAI. There is no relationship between the FAI SNR and the highest frequencies (f_tE_s) (or blanket frequencies (f_bE_s)). SNR of FAIs, however, is found to be related well with (f_tE_s-f_bE_s).

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.450-453
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• 2000

In this paper, an automated segmentation algorithm is proposed for MR brain images using T1-weighted, T2-weighted, and PD images complementarily. The proposed segmentation algorithm is composed of 3 steps. In the first step, cerebrum images are extracted by putting a cerebrum mask upon the three input images. In the second step, outstanding clusters that represent inner tissues of the cerebrum are chosen among 3-dimensional (3D) clusters. 3D clusters are determined by intersecting densely distributed parts of 2D histogram in the 3D space formed with three optimal scale images. Optimal scale image best describes the shape of densely distributed parts of pixels in 2D histogram. In the final step, cerebrum images are segmented using FCM algorithm with it’s initial centroid value as the outstanding cluster’s centroid value. The proposed segmentation algorithm complements the defect of FCM algorithm, being influenced upon initial centroid, by calculating cluster’s centroid accurately And also can get better segmentation results from the proposed segmentation algorithm with multi spectral analysis than the results of single spectral analysis.

• The Pure and Applied Mathematics
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• v.20 no.4
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• pp.269-276
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• 2013

We find an explicit $C^{\infty}$-continuous path of Riemannian metrics $g_t$ on the 4-d hyperbolic space $\mathbb{H}^4$, for $0{\leq}t{\leq}{\varepsilon}$ for some number ${\varepsilon}$ > 0 with the following property: $g_0$ is the hyperbolic metric on $\mathbb{H}^4$, the scalar curvatures of $g_t$ are strictly decreasing in t in an open ball and $g_t$ is isometric to the hyperbolic metric in the complement of the ball.

• Journal of Korean Neurosurgical Society
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• v.47 no.6
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• pp.437-441
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• 2010

Objective : The precise intra- vs. extradural localization of aneurysms involving the paraclinoid internal carotid artery is critical for the evaluation of patients being considered for aneurysm surgery. The purpose of this study was to investigate the clinical usefulness of T2-weighted threedimensional (3-D) fast spin-echo (FSE) magnetic resonance (MR) imaging in the evaluation of unruptured paraclinoid aneurysms. Methods : Twenty-eight patients with unruptured cerebral aneurysms in their paraclinoid regions were prospectively evaluated using a T2- weighted 3-D FSE MR imaging technique with oblique coronal sections. The MR images were assessed for the location of the cerebral aneurysm in relation to the dural ring and other surrounding anatomic compartments, and were also compared with the surgical or angiographic findings. Results : All 28 aneurysms were identified by T2-weighted 3D FSE MR imaging, which showed the precise anatomic relationships in regards to the subarachnoid space and the surrounding anatomic structures. Consequently, 13 aneurysms were determined to be intradural and the other 15 were deemed extradural as they were confined to the cavernous sinus. Of the 13 aneurysms with intradural locations, three superior hypophyseal artery aneurysms were found to be situated intradurally upon operation. Conclusion : High-resolution T2-weighted 3-D FSE MR imaging is capable of confirming whether a cerebral aneurysm at the paraclinoid region is intradural or extradural, because of the MR imaging's high spatial resolution. The images may help in identifying patients with intradural aneurysms who require treatment, and they also can provide valuable information in the treatment plan for paraclinoid aneurysms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.9
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• pp.752-759
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• 2018

This paper presents methods and results of nonlinear simulations for a guided munition for verifying stability at slow spin. The munition is launched by an artillery and it deploys the rear fins to reduce its spin. While the spin speed command is set to 1 rps and 3 rps, wind gusts of 3m/s, 7m/s, 10m/s, and 15m/s in amplitude, and 26 different directions were generated as disturbance for each simulation run. Whereas the munition with the spin speed of 3 rps didn't flip, that with 1-rps spin flipped under some gusts. However, the gusts which increase airspeed in the flight direction didn't introduce harmful effect. Most importantly, all the flips of the munition was observed near the end of the simulation where the munition is going down. No problem was observed near the summit of trajectory.

• Journal of Fashion Business
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• v.17 no.2
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• pp.63-81
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• 2013

A Study using compare and analyze about differences among three patterns(shape and size of pattern, fitting and amount of air gap and so on) through 3D simulation. This study use 3D simulation program, DC Suite version 3.0. The results are as a follows: The results of estimation about total appearance, the pattern of Bunka is best of all pattern about total fitting and silhouette of front and back side. The pattern of armstrong and on&on stand low in estimation. As the total fitting, the pattern of Bunka is 4.40, the pattern of Armstrong is 2.60 and the pattern of On&on is 1.60. The result show better pattern of Bunka than pattern of Armstrong and On&on. When we examine about space between body and cloth, the pattern of Bunka is best. The pattern of Armstrong don't have problems about back side but front side have some problem of getting loose. Because it only have a waist dart so dart size is too big. The pattern of On&on have so much space because it don't have a waist dart. On the amount of air gap, the pattern of Bunka squash up body so it have the amount of air gap 0.08 at bust circumference and underbust circumference. Next is the pattern of Armstrong, amount of air gap is 0.14 at bust circumference and 0.23 at underbust circumference. The pattern of On&on's amount of air gap is 0.30 at bust circumference and 0.37 at underbust circumference. So the pattern of Bunka is bodice block of the best closing adhesion and the On&on is a loose-fitting pattern.

• Bulletin of the Korean Chemical Society
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• v.19 no.3
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• pp.340-344
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• 1998

A facile synthesis of 4,5-(1',2'-diphenylethylenedithio)-1,3-dithiole-2-thione (dPhEDT-DTT) is carried out via a Diels-Alder type [2+4] cycloaddition reaction of 1,3-dithiol-2,4,5-trithione oligomer and t-stilbene. Molecular structure of dPhEDT-DTT is determined by x-ray crystallography: space group P1, a=11.694(3) Å, b=12.117(3) Å, c=14.688(3) Å, α=113.12(2)°, β=102.23(2)°, γ=107.02(2)°, V= 1699.1(7) Å3, Z=2. It turns out that dPhEDT-DTT crystallizes as a racemic compound consisting of (R,R) and (S,S) enantiomers. Coupling reaction of dPhEDT-DTO undergone in neat P(OEt)3 yields TTF(SEt)4 instead of ET derivative. When PR3 (R=OEt, OPh, Ph) is used in benzene, toluene or xylene, however, dPhEDT-DTO is decomposed.

• Journal of The Korean Astronomical Society
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• v.42 no.6
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• pp.135-144
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• 2009

We present JHK near-infrared photometric study for the old open cluster (OC) Trumpler 5 (Tr 5), based on the 2MASS data. From the color-magnitude diagrams of Tr 5, we have located the position of the red giant clump (RGC) stars, and used the mean magnitude of the RGC stars in K-band to estimate the distance to Tr 5, d = $3.1{\pm}0.1$ kpc ($(m-M)_0$ = $12.46{\pm}0.04$). From fitting the theoretical isochrones of Padova group, we have estimated the reddening, metallicity, and age : E(B-V) = $0.64{\pm}0:05$, [Fe/H] = $-0.4{\pm}0.1$ dex, and t = $2.8{\pm}0.2$ Gyr (log t = $9.45{\pm}0.04$), respectively. These parameters generally agree well with those obtained from the previous studies on Tr 5 and confirms that this cluster is an old OC with metallicity being metal-poorer than solar abundance, located in the anti-Galactic center region.

• Journal of applied mathematics & informatics
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• v.29 no.5_6
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• pp.1549-1556
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• 2011

In this paper, we give an estimate on the difference between $x^n(t)$ and x(t) and it clearly shows that one can use the Picard iteration procedure to the approximate solutions to stochastic functional differential equations with infinite delay at phase space BC(($-{\infty}$, 0] : $R^d$) which denotes the family of bounded continuous $R^d$-valued functions ${\varphi}$ defined on ($-{\infty}$, 0] with norm ${\parallel}{\varphi}{\parallel}={\sup}_{-{\infty}<{\theta}{\leq}0}{\mid}{\varphi}({\theta}){\mid}$ under non-Lipschitz condition being considered as a special case and a weakened linear growth condition.