• 대한수학회논문집
• /
• 제16권4호
• /
• pp.567-572
• /
• 2001

Wurful gave a characterization of those rings R which satisfy that for every ring extension $R{\subset}S$. Ho $m_{R}$(S, -) preserves injective envelopes. In this note, we consider an analogous problem concerning injective covers.

• 대한수학회논문집
• /
• 제33권1호
• /
• pp.37-44
• /
• 2018

We prove some theorems showing that a right Jordan ideal or a left Jordan ideal of a 3-prime near-ring must be commutative if it admits a nonzero derivation acting as a homomorphism or an antihomomorphism. Moreover, we give examples proving necessity of the conditions given.

• 대한수학회논문집
• /
• 제34권4호
• /
• pp.1079-1098
• /
• 2019

In this paper we give some branching rules for the fundamental representations of Kac-Moody Lie algebras associated to T-shaped graphs. These formulas are useful to describe generators of the generic rings for free resolutions of length three described in [7]. We also make some conjectures about the generic rings.

• 충청수학회지
• /
• 제33권3호
• /
• pp.307-318
• /
• 2020

In this paper, we extend the notion of a generalized derivation F associated with derivation d to two generalized derivations F and G associated with the same derivation d, as a new idea, to obtain the commutativity of prime rings under certain conditions.

• 대한수학회보
• /
• 제59권2호
• /
• pp.265-276
• /
• 2022

In this paper, we introduce duadic codes over finite local rings and concentrate on quadratic residue codes. We study their properties and give the comprehensive method for the computing the unique idempotent generator of quadratic residue codes.

• 대한수학회보
• /
• 제61권2호
• /
• pp.335-353
• /
• 2024

The objective of this paper is to study some central identities involving generalized derivations and anti-automorphisms in prime rings. Using the tools of the theory of functional identities, several known results have been generalized as well as improved.

• 한국정보과학회논문지:정보통신
• /
• 제37권5호
• /
• pp.409-414
• /
• 2010

무선 센서 네트워크에서 센서노드의 지리적인 위치를 요구하는 응용들이 현저하게 증가하고 있다. 최근 다양한 위치 측위 알고리즘들이 제안 되었지만, 대부분의 알고리즘은 특정한 하드웨어로 얻은 RSSI와 LQI 측정치를 기반으로 위치를 추정하고 있다. 본 논문에서는 이러한 추가적인 정보를 이용하지 않아도 기존 연구와 근사한 측정 결과를 얻을 수 있는 '가중 다중 링을 이용한 측위' 알고리즘 WMRL(Weighted Multiple Rings Localization)을 제안한다. 고정노드(anchor nodes)들이 배치되어 있으며, 각 고정노드는 주기적으로 서로 다른 신호 세기의 비콘(beacon) 신호를 송출한다고 가정한다. 그러면, 비콘 신호는 공간상에 링을 형성하게 되며, 파워 레벨의 세기에 따라 다수의 동심원을 형성하는 동시에 링 간에 교차영역을 생성한다. 본 논문에서는 효율적인 측위 계산을 위해 각 링의 거리 비율에 따른 가중치 모텔을 제안한다. 또한, 센서노드는 수신이 가능한 고정노드로부터 가장 가까운 링을 발견할 수 있으며, 이를 활용하여 센서노드는 자신의 위치를 고정노드 좌표의 가중 합으로 구한다. 제안된 알고리즘은 분산적으로 위치를 계산할 수 있으며, 추가적인 하드웨어를 요구하지 않는다. 추가적으로, 비 신뢰적인 RSSI 및 LQI에 의존하지 않고, 각 링 간의 거리 비율로 측위가 가능한 것이 특정이다. 그럼에도 불구하고, WMRL은 시뮬레이션 결과 2개의 링, 즉 2개의 파워 레벨로 구성하였을 경우에는 기존의 centroid 방식보다 평균 측위 에러가 2배 감소하였고, 3개의 링을 구성하였을 경우에는 WCL(Weighted Centroid Localization)과 대등한 측위 결과를 보였다.

• Bulletin of the Korean Chemical Society
• /
• 제16권10호
• /
• pp.923-929
• /
• 1995

Four crystal structures of M3-A (M3Na9-xHx-A, M=Rb or K and x=1 or 0), Rb3Na8H-A(a=12.228(1) Å and R1=0.046), Rb3Na9-A (a=12.258(3) Å and R1=0.058), K3Na8H-A (a=12.257(3) Å and R1=0.048) and K3Na9-A (a=12.257(3) Å and R1=0.052), have been determined by single crystal x-ray diffraction technique in the cubic space group Pm3^m at 21 ℃. In all structures, each unit cell contained three M+ ions all located at one crystallographically distinct position on 8-rings. Rb+ ions are 3.12 and 3.21 Å away respectively from O(1) and O(2) oxygens, about 0.40 Å away from the centers of the 8-rings, and K+ ions are 2.87 and 2.81 Å apart from the corresponding oxygens. These distances are the shortest ones among those previously found for the corresoponding ones. Eight 6-rings per unit cell are occupied by eight Na+ ions, each with a distance of 2.31 Å to three O(3) oxygens. The twelfth cation per unit cell is found as Na+ opposite 4-ring in the large cavities of M3Na9-A and assumed to be H+ for M3Na8H-A. With these noble non-framework cationic arrangements, larger M+ ions preferably on all larger 8-rings and the compact Na+ ions on all 6-rings, the bond angles in the 8-rings of M3-A, 145.1 and 161.0 respectively for (Si,Al)-O(1)-(Si,Al) and (Si,Al)-O(2)-(Si,Al), turned out to be remarkably stable and smaller, by more than 12 to 17°, than the corresponding angles found in the crystal structures of zeolites A with high concentration of M+ ions. It is to achieve these remarkably relaxed 8-rings, the main windows for the passage of gas molecules, with simultaneously maximized cavity volumes that M3-A have been selected as one of the efficient zeolite A systems for gas encapsulation.

• 한국가구학회지
• /
• 제23권2호
• /
• pp.222-228
• /
• 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.

• 천문학회보
• /
• 제38권2호
• /
• pp.39.2-39.2
• /
• 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.