• The Korean Journal of Physiology and Pharmacology
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• 제12권6호
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• pp.337-342
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• 2008

Human bone marrow mesenchymal stem cells (hBM-MSCs) represent a potentially valuable cell type for clinical therapeutic applications. The present study was designed to evaluate the effect of long-term culturing (up to $10^{th}$ passages) of hBM-MSCs from eight individual amyotrophic lateral sclerosis (ALS) patients, focusing on functional ion channels. All hBM-MSCs contain several MSCs markers with no significant differences, whereas the distribution of functional ion channels was shown to be different between cells. Four types of $K^+$ currents, including noise-like $Ca^{+2}$-activated $K^+$ current ($IK_{Ca}$), a transient outward $K^+$ current ($I_{to}$), a delayed rectifier $K^+$ current ($IK_{DR}$), and an inward-rectifier $K^+$ current ($K_{ir}$) were heterogeneously present in these cells, and a TTX-sensitive $Na^+$ current ($I_{Na,TTX}$) was also recorded. In the RT-PCR analysis, Kv1.1,, heag1, Kv4.2, Kir2.1, MaxiK, and hNE-Na were detected. In particular, ($I_{Na,TTX}$) showed a significant passage-dependent increase. This is the first report showing that functional ion channel profiling depend on the cellular passage of hBM-MSCs.

• Journal of the Korean Wood Science and Technology
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• 제43권4호
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• pp.486-493
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• 2015

설치된 데크재에 대한 성능을 평가하기 위하여 초음파 비파괴시험법을 사용하였다. 먼저 3종류의 데크재에 대해 트랜스듀서의 배치에 따른 직접법과 간접법간의 측정방법간의 차이를 검증하였으며 두 번째로 설치된 데크재의 사용시간의 경과에 따른 초음파속도를 측정 비교하였다. 마지막으로 데크재의 사용수명을 파악하기 위하여 사용시간의 경과에 따른 초음파속도의 변화를 조사하였다. 시험결과 직접법과 간접법간의 측정방법간의 차이는 없는 것으로 나타났으며 직접법에 대한 간접법의 비율은 1.02와 1.05로 각각 나타났다. 설치된 데크재에서 시간의 경과에 따라 초음파 속도는 감소하였으며 이들 간의 관계는 선형으로 나타났다. 시험결과로부터 초음파 비파괴시험법은 설치된 데크재의 유지보수에 관한 효율적인 수단이 될 수 있을 것으로 생각된다.

• 천문학회보
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• 제36권2호
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• pp.91-91
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• 2011

The passage of the interplanetary discontinuity (i.e., sudden increases in the solar wind speed, density, and IMF strength) was detected by ACE near GSE (x, y, z) ~ (222, -36, 3) Re upstream of Earth around 22:48 UT on November 24, 2008. About 55 min later, this solar wind discontinuity was observed by Geotail near GSE (x, y, z) ~ (23, 18, -7) Re in front of Earth's bow shock. From the propagation time of the solar wind discontinuity between ACE and Geotail, it is expected that the discontinuity front is aligned with the Parker spiral and strikes the postnoon dayside magnetopause first. Using coordinated multi-point measurements (THEMIS and GOES) at or in geosynchronous orbit, we observed a tailward propagating sudden impulse (SI), excited by the interplanetary discontinuity, around 23:50 UT with its front retaining alignment similar to that of solar wind discontinuity. The SI event appears a negative-then-positive variation in the H component at high latitude Chokurdakh (CHD: MLAT ~ 64.7 deg) in the prenoon sector, which is opposite sense of normal SI event. During the positive deflection at CHD, the SuperDARN Hokkaido radar detected the downward motion of the ionosphere, implying westward electric field enhancement, at subauroral latitudes near CHD meridian. In our study we will discuss magnetospheric and ionospheric responses to the passage of the solar wind discontinuity using multi-point observations in space and on the ground.

• 한국경영과학회지
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• 제19권3호
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• pp.93-109
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• 1994

Even though sojourn time distributions are essential information in analyzing queueing networks, there are few methods to compute them accurately in non-product form queueing networks. In this study, we model the location process of a typical customer as a GMPH semi-Markov chain and develop computationally useful formula for the transition function and the first-passage time distribution in the GMPH semi-Markov chain. We use the formula to develop an effcient method for approximating sojourn time distributions in the non-product form queueing networks under quite general situation. We demonstrate its validity through numerical examples.

• International Journal of Reliability and Applications
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• 제9권2호
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• pp.167-182
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• 2008

The objective of this paper is to discuss the stochastic analysis and the statistical inference of a three-states semi-Markov reliability model. Using the maximum likelihood procedure, the parameters included in this model are estimated. Based on the assumption that the lifetime and repair time of the system are gener-alized Weibull random variables, the reliability function of this system is obtained. Then, the distribution of the first passage time of this system is derived. Many important special cases are discussed. Finally, the obtained results are compared with those available in the literature.

• 대한수학회보
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• 제50권5호
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• pp.1659-1671
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• 2013

In this paper, we are concerned with the analysis of the waiting time distribution in the M/M/m retrial queue. We give expressions for the Laplace-Stieltjes transform (LST) of the waiting time distribution and then provide a numerical algorithm for calculating the LST of the waiting time distribution. Numerical inversion of the LSTs is used to calculate the waiting time distribution. Numerical results are presented to illustrate our results.

• International Journal of Reliability and Applications
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• 제6권1호
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• pp.13-29
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• 2005

This paper deals with the stochastic analysis of a three-states semi-Markov reliability model. Using both the maximum likelihood and Bayes procedures, the parameters included in this model are estimated. Next, assuming that the lifetime and repair time are generalized exponential random variables, the reliability function of this system is obtained. Then, the distribution of the first passage time of this system is discussed. Finally, some of the obtained results are compared with those available in the literature.

• Smart Structures and Systems
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• 제2권4호
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• pp.313-320
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• 2006

The reliability analysis of structures subjected to stochastic loading involves evaluation of time and probability of the system's residence in a reference domain. In this paper, we derive an asymptotic estimate of exit time for multi-degrees-of-freedom structural systems. The system's dynamics is governed by the Lagrangian equations with linear dissipation and fast additive noise. The logarithmic asymptotic of exit time is found explicitly as a sum of two terms dependent on kinetic and potential energy of the system, respectively. As an example, we estimate exit time and an associated structural performance for a rocking structure.

• 대한수학회보
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• 제56권5호
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• pp.1355-1376
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• 2019

We investigate the valuation of participating life insurance policies with default risk under a geometric regime-switching jump-diffusion process. We derive explicit formula for the Laplace transform of the price of participating contracts by solving integro-differential system and then price them by inverting Laplace transforms.

• 한국군사과학기술학회지
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• 제12권2호
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• pp.236-247
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• 2009

In Korea, the driving system restriction criteria is strictly applied(gross weight 400kN, axial load 100kN). Especially after the Seoungsu Bridge accident, safety factor has been strictly applied. The Safety factor is applied to the cumulative results for each steps like design, construction, maintenance of the Bridge. Because of it, the bridge is undervalued compared to its capacity. So, this generates loss for both private and military sector(eg. logistical delays, structural damage, etc.). But analyzing data from many existing researches we have confirmed that the military heavy vehicle may pass through the first class bridges. In consequence, this study have focused on determining whether HETS vehicles can pass over the first class bridge, without safety issues, using MIDAS structural analysis program. The results have confirmed that the military heavy vehicle may pass over the bridge.