• Journal of the Korea Furniture Society
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• v.23 no.2
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• pp.222-228
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• 2012

Seonreung is the tomb of Seong-jong (A.D. 1457~1494), the 9th king of Joseon Dynasty (1392-1910) and his second queen Jeonghyeon-wanghu (1462~1530). We obtained dendrochronological dates of Jeongjagak (ceremonial hall) of Seonreung. It was known first built in 1495 and reconstructed in October 1706, We obtained tree-ring dates of 20 wood elements (beams, pillars, truss posts, cant strips, roof boards and roof loaders). Their outermost rings were dated from 1630 to 1705. The dates of bark rings in four elements were A.D. 1705 with completed latewoods, indicating that these woods were cut some time between the autumn of 1705 and spring of 1706. The results confirmed the reconstruction date Jeongjagak of Seonreung in 1706, suggesting that there was not so long period for wood drying or storage, i.e., less than 6 months. The dates of outermost rings prior to 1705 in other elements indicated that some outer rings of these elements were removed during wood processing. Tree-ring dating proved that the present Jeongjagak of Seonreung had been well preserved for more than 300 years.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.39.2-39.2
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• 2013

We use grid-based hydrodynamic simulations to study star formation history in nuclear rings of barred-spiral galaxies. In our previous study, we concentrated on bar-only galaxies without spirals, finding that the star formation rate (SFR) in a nuclear ring exhibits a strong primary burst at early time before decreasing to below 1 $M_{\odot}/yr$ at late time. The rapid decline is caused by the paucity of the gas in the bar region, due to early massive gas inflows to the nuclear ring. Since star formation in nuclear rings is observed to be sustained for about 1-2 Gyr, this requires mechanisms to supply the gas to the bar regions. In this work, we study the effect of spiral arms on the radial gas inflows and related star formation in the nuclear rings. We show that spiral arms are efficient to remove angular momentum of the gas to cause significant gas inflows to the bar region, provided the patten speed of the arms is much smaller than that of the bar. The inflowing gas is added to a nuclear ring, making the ring SFR episodic over a long period of time. The time interval of multiple bursts of star formation is a few tens to hundred million years, with the mean peak SFR of ${\sim}5M_{\odot}/yr$, consistent with observations of M100.

• Tribology and Lubricants
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• v.23 no.4
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• pp.170-174
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• 2007

Wear and scuffing tests were conducted using friction and wear measurement of piston rings and cylinder blocks in low friction diesel engine. The frictional forces, wear amounts and cycles to scuffing in boundary lubricated sliding condition were measured using the reciprocating wear tester. The cylinder blocks were used as reciprocating specimens, and the piston rings with several coatings were used as fixed pin. Several coatings were used such as DLC, TiN, Cr-ceramic and TiAlN in order to improve the tribological characteristics. From the tests wear volume of piston ring surfaces applied various coatings were compared. During the tests coefficients of friction were monitored. Test results showed that DLC coatings showed good tribological properties. TiN and Cr-ceramic coated rings showed good wear resistance properties but produced high friction.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.39.1-39.1
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• 2012

Nuclear rings in barred galaxies are sites of active star formation (SF). We investigate SF and its feedback effects occurring in barred galaxies, for the first time, using high-resolution grid-based hydrodynamic simulations. The gaseous medium is assumed to be infinitesimally thin, isothermal, and unmagnetized. The SF recipes include a density threshold corresponding to the Jeans condition, a SF efficiency of 1%, and momentum feedback via Type II supernova events together with stellar-wind mass loss. To investigate various environments, we vary the gas sound speed as well as the efficiency of momentum injection in the in-plane direction. We find that when the sound speed is small, the surface density of a ring becomes largely independent of the azimuthal angle, resulting in star-forming regions distributed over the whole length of the ring. When the sound speed is large, on the other hand, the ring achieves the largest density at the contact points between the dust lanes and the ring where SF occurs preferentially, leading to a clear age gradient of star clusters in the azimuthal direction. Since rings shrink with time, a radial age gradient of star clusters naturally develop regardless of sound speed, consistent with observations. SF persists over 200 Myr, with an average rate of ${\sim}1.3M_{\odot}/yr$ similar to observed values. Rings gradually become hostile to SF as they lose gas into stars and turbulent motions dominate.

• Bulletin of the Korean Mathematical Society
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• v.57 no.1
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• pp.207-218
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• 2020

Some modular representations of reflection groups related to Weyl groups are considered. The rational cohomology of the classifying space of a compact connected Lie group G with a maximal torus T is expressed as the ring of invariants, H*(BG; ℚ) ≅ H*(BT; ℚ)^W(G), which is a polynomial ring. If such Lie groups are locally isomorphic, the rational representations of their Weyl groups are equivalent. However, the integral representations need not be equivalent. Under the mod p reductions, we consider the structure of the rings, particularly for the Weyl group of symplectic groups Sp(n) and for the alternating groups A_n as the subgroup of W(SU(n)). We will ask if such rings of invariants are polynomial rings, and if each of them can be realized as the mod p cohomology of a space. For n = 3, 4, the rings under a conjugate of W(Sp(n)) are shown to be polynomial, and for n = 6, 8, they are non-polynomial. The structures of H*(BT^n-1; 𝔽_p)^A_n will be also discussed for n = 3, 4.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.611-623
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• 1997

This paper provides the results of an experimental and analytical study performed on the beam to Concrete Filled Circular Steel Column connections with the external stiffener rings under the gravity loads. Specimens are modeled as a 1/4 scale of the beam-columns as gravity loads are applied to a multi-story frame. Important parameters in this study are the width of the external rings, the diameter-thickness ratios of column and whether or not the external rings are welded to the circular column. A total of 20 specimens are tested to clarify the structural behavior of the CFT column connections with the external stiffener rings. The test results are summarized for the yield and maximum strength and stiffness. The existing design equations for the allowable and yield load capacities are referred to verify the structural characteristics for the connections.

• Korean Journal of Veterinary Research
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• v.45 no.4
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• pp.485-493
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• 2005

We studied the effects of trazodone on arterial blood pressure in anesthesized guinea pigs, and on vascular responses in isolated thoracic aorta. Trazodone produced a concentration-dependent relaxation in phenylephrine-precontracted endothelium intact (+E) rings, but not in a KCl-precontracted aortic rings. These relaxant effects of trazodone on +E rings were significantly greater than those on denuded (-E) rings. The trazodone-induced relaxation was suppressed by glibenclamide and tetrabutylammonium, but not by N(G)-nitro-L-arginine (L-NNA), N(omega)-nitro-L-arginine methyl ester (L-NAME), methylene blue (MB), nifedipine, indomethacin, 2-nitro-4-carboxyphenyl-n,n-diphenylcarbamate (NCDC) and clotrimazole. In vivo, infusion of trazodone elicited a significant decrease in arterial blood pressure. Trazodone-induced blood pressure lowering was markedly inhibited by intravenous pretreatment of prazosin but not by pretreatment of saponin, L-NNA, L-NAME, MB, nifedipine, glibenclamide, clotrimazole and NCDC. In addition, trazodone produced an increase in twitch force of isolated papillary muscle and left ventricular pressure of perfused heart. These findings suggest that the endothelium-independent vasorelaxant effect of trazodone may be explained by activation of $Ca^{2+}$-activated and ATP-sensitive $K^+$ channels, and the hypotensive effect of trazodone is not associated with cardiac contraction.

• Journal of Ginseng Research
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• v.16 no.3
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• pp.175-182
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• 1992

Intravenous administration of saponin from the root of Panax ginseng (red ginseng) lowered the blood pressure in a dose-dependent manner (10~100 mg/kg B.W) in anesthetized rats. Therefore, experiments were designed to study whether this lowering of blood pressure is associated with the release of endothelium-derived relaxing factor. Rings of thoracic aorta with and without endothelium were suspended for the measurement of isometric tension in organ chamber. All experiments were performed in the presence of indomethacin (10-5 M). Ginseng saponin (10-5~3$\times$10-4 g/ml) relaxed contractions induced by phenylephrine (10-5 M) in the aorta with endothelium but not in that without endothelium. Treatment of aortic rings with NG_monomethyl-L-arginine (L-NMMA 10-4 M for 30 min), a competive inhibitor of nitric oxide synthase and methylene blue (M.B., 3$\times$10-7 M for 30 min), an inhibitor of soluble guanylate cyclase, diminished the relaxation induced by ginseng saponin. In thoracic aortic rings from rats treated with ginseng saponin for 2 weeks intraperitoneally, the relaxation to acetylcholine was increased compared with non-ginseng treated rings. These data suggest that red ginseng saponin evokes hypotension and that vascular relaxations induced by red ginseng saponin are inediatpd by release of endothelium-derived relaxing factor.

• Proceedings of the Ginseng society Conference
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• 1998.06a
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• pp.182-189
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• 1998

Administration of ginsenosides, a mixture of saponin extracted from Panax ginseng, decreased blood pressure in rat. Previous studies have shown that ginsenosides caused endothelium-dependent relaxation, which was associated with the formation of cyclic GMP, suggested that ginsenosides caused release of nitric oxide (NO) from the vascular endothelium. The aim of the present study was to characterize the endothelium-independent relaxation to ginsenosides in the isolated rat aorta. Ginsenosides caused a concentration-dependent relaxation of rat aortic rings without endothelium constricted with 25 mM KCI but affected only minimally those constricted with 60 mM KCI. Ginsenoside Rg3 (Rg3) was a more potent vasorelaxing agonist than total ginsenoside mixture and also the ginsenoside PPT and PPD groups. Relaxation to ginsenosides were markedly reduced by TEA, but not by glibenclamide. Rg3 significantly inhibited Cal'-induced concentration-contraction curves and the "50a2'influx in aortic rings incubated in 25 mM KCI whereas those responses were not affected in 60 mM KCI. Rg3 caused efflux of $"Rb in aortic rings that was inhibited by tetraethy- lammonium (TEA), an inhibitor of Ca"-dependent K'channels, but not by glibenclamide, an inhibitor of AfP-dependent K'channels. These findings indicate that ginsenosides may induce vasorelaxation via activation of Ca2'-dependent K'channels resulting in hyperpolarization of the vas- cular smooth muscle with subsequent inhibition of the opening of voltage-dependent Caf'channels. These effects could contribute to explain the red ginseng-associated vasodilation and the beneficial effect on the cardiovascular system.

• Fashion & Textile Research Journal
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• v.1 no.2
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• pp.166-172
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• 1999

An experimental investigation has done for studying the changes of physical properties of the air-jet textured polyester yarn. Through the experiments of polyester 85/72 drawn yarn and 50/36 partially oriented yarn doubling' the following results are obtained. The tenacity of textured yarn decreased as the number of tension rings increased when the nozzle diameter was 1.2 mm. In the case when the tension ring was not used during the texturing process, the tenacity of textured yarn decreased as the nozzle diameter increased. But this tendency changed according to the number of tension rings used, the diameter of the nozzle, and yarn take-up speed. Breaking elongation decreased as the number of tension rings increased from one to four and the take-up speed increased at diameter 1.2 mm of the nozzle. The higher the diameter of the the nozzle the higher the breaking elongation until 1.4 mm. The number of interlacing went down as the diameter of the nozzle increased and the take-up speed of the yarn increased. The higher the number of tension rings, the lower the number of interlacing.