• Communications of the Korean Mathematical Society
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• v.34 no.3
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• pp.743-755
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• 2019

For every inverse semigroup S with subsemigroup E of idempotents, necessary and sufficient conditions are obtained for the weighted semigroup algebra $l^1(S,{\omega})$ and its second dual to be $l^1(E)$-module amenble. Some results for the module Arens regularity of $l^1(S,{\omega})$ (as an $l^1(E)$-module) are found. If S is either of the bicyclic inverse semigroup or the Brandt inverse semigroup, it is shown that $l^1(S,{\omega})$ is module amenable but not amenable for any weight ${\omega}$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6A
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• pp.609-616
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• 2011

The Delay/Disruption Tolerant Network (DTN) is a network designed to operate effectively using the mobility and storage of intermediate nodes under no end-to-end guaranteed network. This new network paradigm is well-suited for networks which have unstable path and long latencies (e.g. interplanetary network, vehicular network). In this paper, we first found that each taxi has its own regularly visiting area and define this property as spatial regularity. We analyze 4000 taxi trace data in Shanghai and show the existence of spatial regularity experimentally. Based on a spatial regularity in urban environment, we present a new DTN routing method. We introduce a Weighted Center (WC) which represents spatial regularity of each node. Through the association with evenly distributed access points (APs) in urban environment, most of vehicles get their grid locations and calculate their WCs. Since our routing method only uses neighbors' WCs for building routing paths, it can be regarded as distributed and practical protocols. Our experiments involving realistic network scenarios created by the traces of about 1500 Shanghai taxies show that our routing method achieves the higher performance compared to ECT, LET by 10%~110%.

• Korean Parent-Child Health Journal
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• v.2
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• pp.83-110
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• 1999

The purpose of this study was to identify the sleep/activity patterns of neonates and to provide a baseline data for the development effective mother-infant relationship. Subjects of this study were 36 newborns aged 1-21 days and stayed in Postpartum Care Center in Taejon during the period of October 28th, 1999 to February 10th, 2000. The data were collected using NCASA developed by Barnard et al. and were analyzed with SPSS 7.5 for window program. The results of this study were as follows: 1. An average day sleep of neonates was 8.0 hours, night sleep was 3.6 hours, and total sleep was 11.6 hours. A longest period of day sleep was 3.8 hours and a longest period of night sleep was 3.4 hours. The regularity of day sleep was 22.1%, night sleep was 23.3%, and total was 22.1%. 2. The frequency of daytime feeding was 6.9, nighttime fee ding was 3.4, resulting in total of 10.3. The regularity of feeding was 37.4%, and the frequency of night awakening was 2.4. 3. Associations among variables related to neonate's sleep/activity records were as follows : - The regularity of total sleep was positively correlated with the frequencies of day sleep(r=.57, P=.00), night sleep (r=.40, P=.01), and total sleep(r=.65, P=.00). - The frequency of total feeding was negatively correlated with the frequencies of day sleep(r=-.29, P=.04), night sleep(r=-.39, P=.02), and total sleep(r=-.42, P=.00), as well as longest day sleep(r=-.50, P=.00). - The regularity of feeding was negatively correlated with the frequency of night sleep(r=-.35, P=.02), longest period of day sleep(r=-.32, P=.04), and longest period of night sleep(r=-.30. P=.04), whereas positively correlated with frequencies of daytime feeding (r=.29, P=.02) and nighttime feeding (r=.32, P=.05). - The frequency of night awakening was negatively correlated with amount of night sleep(r=-.39, P=.02) and frequency of daytime feeding(r=-.42, P=.01) while positively correlated with frequencies of nighttime feeding(r=.68, P=.00) and total feeding(r=.50, P=.00). 4. Although there was no statistical significant difference between sleep pattern and infant's age, following tendency was noted: - As baby gets older, total amount of sleep and longest period of day sleep decreased while longest period of night sleep increased. - As baby gets older, the regularity of day sleep decreased while the regularity of night sleep and total sleep slightly increased. - The frequencies of daytime and total feedings increased while the frequency of nighttime feeding decreased. In conclusion, the author found that the neonates of this study showed less amount of sleep, more night awakening, and more night time feedings than NCAST sample. There was a certain sleep/activity pattern existed: If babies were fed more frequently, daytime or nighttime sleeping hours became shorter, and if babies had longer daytime sleep, frequent nighttime awakenings were noted. This pattern illustrated the significant influence of feeding and sleep periods on each other. Awakening in the night is natural and normal patterns in the newborn period. The result of this study will provide information to parents about what to expect their infants.

• Honam Mathematical Journal
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• v.27 no.4
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• pp.665-672
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• 2005

By its simplicity and efficiency, subdivision is a widely used technique in computer graphics, computer aided design and data compression. In this paper we prove a regularity theorem for ternary interpolatory subdivision scheme that can be applied to non-stationary subdivision. This theorem converts the convergence of the limit curve of a ternary interpolatory subdivision to the analysis of the rate of the contraction of differences of the polygons.

• Bulletin of the Korean Mathematical Society
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• v.50 no.1
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• pp.143-159
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• 2013

This paper is concerned with the long time behavior for the solution semiflow of the coupled two-compartment Gray-Scott equations with the homogeneous Neumann boundary condition on a bounded domain of space dimension $n{\leq}3$. Based on the regularity estimates for the semigroups and the classical existence theorem of global attractors, we prove that the equations possesses a global attractor in $H^k({\Omega})^4$ ($k{\geq}0$) space.

• Journal of the Korean Mathematical Society
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• v.54 no.3
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• pp.909-943
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• 2017

This paper is devoted to studying abstract stochastic semilinear evolution equations with additive noise in Hilbert spaces. First, we prove the existence of unique local mild solutions and show their regularity. Second, we show the regular dependence of the solutions on initial data. Finally, some applications to stochastic partial differential equations are presented.

• Journal of the Korean Mathematical Society
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• v.37 no.6
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• pp.1059-1070
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• 2000

Under the critical assumption that ▽u$\in$L(sub)loc(sup)${\alpha}$,${\beta}$, 3/${\alpha}$ + 2/${\beta}$ $\leq$ 2 with ${\alpha}$ $\geq$ 3/2, a boundary L(sup)$\infty$ estimate for the solution is derived if the pressure on the boundary is bounded. Here, our estimate is local.

• Bulletin of the Korean Mathematical Society
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• v.47 no.3
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• pp.653-661
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• 2010

Let R be a ring, and let $\Psi$(R) be the ideal generated by the set {x $\in$R | 1 + sxt $\in$ R is unit-regular for all s, t $\in$ R}. We show that $\Psi$(R) has "radical-like" property. It is proven that $\Psi$(R) has stable range one. Thus, diagonal reduction of matrices over such ideal is reduced.

• Bulletin of the Korean Mathematical Society
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• v.44 no.1
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• pp.151-156
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• 2007

A connection between weak ${\pi}-regularity$ and the condition every prime ideal is maximal will be investigated. We prove that a certain 2-primal ring R is weakly ${\pi}-regular$ if and only if every prime ideal is maximal. This result extends several known results nontrivially. Moreover a characterization of minimal prime ideals is also considered.

• Journal of the Korean Mathematical Society
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• v.49 no.6
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• pp.1273-1299
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• 2012

We prove the global regularity of weak solutions to a conormal derivative boundary value problem for quasilinear elliptic equations in divergence form on Lipschitz domains under the controlled growth conditions on the low order terms. The leading coefficients are in the class of BMO functions with small mean oscillations.