• Bulletin of the Korean Chemical Society
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• v.26 no.4
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• pp.619-628
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• 2005

We attempted to replace a benzopyran ring of 4-[(N-imidazol-2-ylmethyl)-4-chloroanilino]benzopyran, previously discovered as anti-angiogenic agent with antitumor activity, with pyranopyridines. The [3,2-c]-, [3,2-b]-, [2,3-c]-, and [2,3-b]-pyranopyridines with -(imidazol-2-ylmethyl)aniline moiety at the 4-position, were synthesized respectively, and evaluated for primary anti-angiogenic properties through primary cultured HUVEC tube formation assay. From this study, we found that the pyranopyridine ring, especially [3,2-b]- and [2,3-c]-isomer, can replace the benzopyran ring of the compound 1 and can be optimized through the introduction of substituents both on the pyranopyridine ring and the aniline moiety for the identification of a novel anti-angiogenic agent.

• Current Optics and Photonics
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• v.7 no.4
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• pp.457-462
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• 2023

Quantitative measurement of trace ethane is important in environmental science and biomedical applications. For these applications, we typically require a few tens of part-per-trillion level measurement sensitivity. To measure trace-level ethane, we constructed a cavity ring-down spectroscopy setup in the 3.37 ㎛ mid-infrared wavelength range, which is applicable to multi-species chemical analysis. We demonstrated that the detection limit of ethane is approximately 300 parts per trillion, and the measured concentration is in agreement with the amounts of the injected sample. We expect that these results can be applied to the chemical analysis of ethane and applications such as breath test equipment.

• Communications of the Korean Mathematical Society
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• v.35 no.4
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• pp.1087-1093
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• 2020

The aim of this paper is to show that every Engel quasinormal subgroups of the unit group of a division ring with uncountable center is central.

• Kyungpook Mathematical Journal
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• v.63 no.2
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• pp.187-198
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• 2023

The motivation for this study comes from a question posed by I.N. Herstein in the Israel Journal of Mathematics in 1978. Specifically, let D be a division ring with center F. The aim of this paper is to demonstrate that every quasinormal subgroup of the multiplicative group of D, which is radical over some proper division subring, is central if one of the following conditions holds: (i) D is weakly locally finite; (ii) F is uncountable; or (iii) D is the Mal'cev-Neumann division ring.

• Journal of information and communication convergence engineering
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• v.14 no.4
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• pp.246-251
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• 2016

In this study, we developed a reduced 94 GHz hybrid ring coupler on a GaAs substrate in order to demonstrate the possibility of the integration of various passive components and MMICs in the millimeter-wave range. To reduce the size of the hybrid ring coupler, we used multiple open stubs on the inside of the ring structure. The chip size of the reduced hybrid ring coupler with multiple open stubs was decreased by 62% compared with the area of the hybrid ring coupler without open stubs. Performance in terms of the loss, isolation, and phase difference characteristics exhibited no significant change after the use of the multiple open stubs on the inside of the ring structure. The reduced hybrid ring coupler showed excellent coupling loss of $3.87{\pm}0.33dB$ and transmission loss of $3.77{\pm}0.72dB$ in the measured frequency range of 90-100 GHz. The isolation and reflection were -48 dB and -32 dB at 94 GHz, respectively. The phase differences between two output ports were $180^{\circ}{\pm}1^{\circ}$ at 94 GHz.

• Bulletin of the Korean Mathematical Society
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• v.55 no.3
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• pp.837-849
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• 2018

In this paper, we study the closedness such as seminomality and t-closedness, and Noetherian-like properties such as piecewise Noetherianness and Noetherian spectrum, of Hurwitz polynomial rings and Hurwitz series rings. To do so, we construct an isomorphism between a Hurwitz polynomial ring (resp., a Hurwitz series ring) and a factor ring of a polynomial ring (resp., a power series ring) in a countably infinite number of indeterminates.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.5
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• pp.1-7
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• 2004

A regular logical topology requires little processing time for routing purposes which may be a desirable property for high-speed networks. Asymmetric bilayered ShuffleNet, proposed by us as a logical topology, can be used to a wavelength division multiplexing ring network to increase the network capacity compared to ShuffleNet. In this paper, asymmetric bilayered ShuffleNet is imbedded on a wavelength division multiplexing ring with the objective of minimizing the total number of wavelengths assigned.

• Bulletin of the Korean Mathematical Society
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• v.46 no.5
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• pp.867-871
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• 2009

A module M over a ring R is said to satisfy (P) if every generating set of M contains an independent generating set. The following results are proved; (1) Let $\tau$ = ($\mathbb{T}_\tau,\;\mathbb{F}_\tau$) be a hereditary torsion theory such that $\mathbb{T}_\tau$ $\neq$ Mod-R. Then every $\tau$-torsionfree R-module satisfies (P) if and only if S = R/$\tau$(R) is a division ring. (2) Let $\mathcal{K}$ be a hereditary pre-torsion class of modules. Then every module in $\mathcal{K}$ satisfies (P) if and only if either $\mathcal{K}$ = {0} or S = R/$Soc_\mathcal{K}$(R) is a division ring, where $Soc_\mathcal{K}$(R) = $\cap${I 4\leq$ $R_R$ : R/I$\in\mathcal{K}$}.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.3
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• pp.115-120
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• 2022

A brown ring (hereinafter referred to as BR) on the inner surface of a quartz glass crucible used in the manufacturing process of a silicon ingot for semiconductor wafers was studied. BR is 20~30 ㎛ in size and has an asymmetric brown ring shape. The size and distribution of BR were different depending on the crucible location, and the size and distribution of BR were the largest and most abundant in the round part with the highest crucible temperature during Si ingot growth. BR contains cristobalite, which has a higher coefficient of thermal expansion than quartz glass, so it is considered that surface cracks appear. The color development of BR and pin holes are presumed to be due to oxygen vacancies.

• International Journal of Fluid Machinery and Systems
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• v.9 no.3
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• pp.194-204
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• 2016

Floating ring seals offer an opportunity to reduce leakage flows significantly in rotating machinery. Accordingly, they have been applied successfully to rotating machinery within the last several decades. For rocket turbopump applications, fundamental behavior and design philosophy have been revealed. However, further work is needed to explore the rotordynamic characteristics associated with rotor vibrations. In this study, rotordynamic forces for floating ring seals under rotor's whirling motions are calculated to elucidate rotordynamic characteristics. Comparisons between numerical simulation results and experiments demonstrated in our previous report are carried out. The three-dimensional Reynolds equation is solved by the finite-difference method to calculate hydrodynamic pressure distributions and the leakage flow rate. The entrance loss at the upstream inlet of the seal ring is calculated to estimate the Lomakin effect. The friction force at the secondary seal surface is also considered. Numerical simulation results showed that the rotordynamic forces of this type of floating ring seal are determined mainly by the friction force at the secondary seal surface. The seal ring is positioned almost concentrically relative to the rotor by the Lomakin effect. Numerical simulations agree quite well with the experimental results.