• Asian-Australasian Journal of Animal Sciences
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• v.29 no.10
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• pp.1398-1406
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• 2016

In general, the seminiferous tubule basement membrane (STBM), comprising laminin, collagen IV, perlecan, and entactin, plays an important role in self-renewal and spermatogenesis of spermatogonial stem cells (SSCs) in the testis. However, among the diverse extracellular matrix (ECM) proteins constituting the STBM, the mechanism by which each regulates SSC fate has yet to be revealed. Accordingly, we investigated the effects of various ECM proteins on the maintenance of the undifferentiated state of SSCs in pigs. First, an extracellular signaling-free culture system was optimized, and alkaline phosphatase (AP) activity and transcriptional regulation of SSC-specific genes were analyzed in porcine SSCs (pSSCs) cultured for 1, 3, and 5 days on non-, laminin- and collagen IV-coated Petri dishes in the optimized culture system. The microenvironment consisting of glial cell-derived neurotrophic factor (GDNF)-supplemented mouse embryonic stem cell culture medium (mESCCM) (GDNF-mESCCM) demonstrated the highest efficiency in the maintenance of AP activity. Moreover, under the established extracellular signaling-free microenvironment, effective maintenance of AP activity and SSC-specific gene expression was detected in pSSCs experiencing laminin-derived signaling. From these results, we believe that laminin can serve as an extracellular niche factor required for the in vitro maintenance of undifferentiated pSSCs in the establishment of the pSSC culture system.

• IE interfaces
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• v.17 no.spc
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• pp.122-130
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• 2004

Since the cost of software maintenance occupies about 50~75% in a general successful organization, the software maintenance plays an important role in software life cycle. In particular, if the managed system needs to be operated in a long term or the system is very large and complex, then the maintenance is especially more important. Software maintenance is defined as software modification activities after customer delivery, such as improvement of performance or functionality, error correction, adaptation to environmental changes, etc. In this paper, software cost estimation models are proposed, that is based on productivity of manpower in maintenance projects. In order to do this, the activities of maintenance are classified into function change, non-function change, user support and application operation. The proposed models are constructed and verified based on the real size and cost information of projects in the real world. The approach in this paper is to discriminate the heterogeneous activities in maintenance projects, and then to calculate the respective cost of each discriminated activity. By using the proposed models, the total cost of maintenance project is summed from the costs of four activities. In addition the number of conflicts between owner and order receiver about the amount of cost will be reduced and the reasonable cost estimation system will be established.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.935-940
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• 2006

Present periodic maintenance activities are carried on electric rolling stock in Korea based on predetermined inspection intervals. And this can be seen as a first generation of maintenance techniques without taking into consideration a degree of aging or degradation of the componets. In this study, we have analyzed the current status of maintenance being used in the techniques in various activities such as overseas railway operation organization, and good cases for the advanced country's maintenance system being carried out effectively. Based on the analysis, we would derive implications for efficient application and improvement guidance of maintenance system in electric rolling stock.

• Communications for Statistical Applications and Methods
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• v.13 no.3
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• pp.651-656
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• 2006

Wu and Clements-Croome (2005) investigate the optimization problem of PM policies for situations where the quality of PM is a random variable with a certain probability distribution. However, they assume that the cost of preventive maintenance is constant, not depending on the quality of PM. Thus, this paper considers a periodic PM model when PM cost depends on the quality of PM activity. The optimal PM policy are presented for the extended PM model and the numerical examples are presented for illustrative purpose.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.443-450
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• 2003

Our country is constructed the digital map in the first NGIS plan. Through digital map construction, it was had the potentiality that can more easily activate GIS. But these data included numerous problems from user's view. In the second NGIS plan, our government try to construct the framework data for the maximization of GIS utilization. This paper is showed a step of update that considered relationship between the national framework data themes, suggested the structure of maintenance activity for national framework data.

• Biomedical Science Letters
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• v.12 no.3
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• pp.185-190
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• 2006

Lysyl oxidase (LOX) catalyzes the lysine-derived cross-links of fibrillar collagens and elastin in the extracellular matrix. Recent molecular cloning has revealed existence of a LOX family consisting of LOX and four lysyl oxidase-like proteins (LOXL, LOXL2, LOXL3 and LOXL4). Pathological conditions associated with impaired LOX activity in several heritable and acquired disorders lead to severe structural and functional abnormalities of cardiovascular tissues, such as occlusion of coronary arteries and aneurysms, suggesting an essential role for the LOX family proteins in the maintenance of the cardiovascular system. However, the specific roles of the lysyl oxidase-like proteins in normal and pathological conditions of the cardiovascular tissues have not been established yet. Here, I report that LOXL3, a novel member of the LOX family, is predominantly expressed in the aorta, with an amine oxidase activity toward collagen and elastin, suggesting an essential role of LOXL3 in the development and maintenance of the aorta.

• YAKHAK HOEJI
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• v.30 no.6
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• pp.334-342
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• 1986

The relationship between the maintenance of hypertension and the central noradrenergic nervous system activity in spontaneously hypertensive rats (SHR) was studied. The norepinephrine turnover rates in 5 brain areas; telencephalon, hypothalamus/thalamus, midbrain, pons/medulla, cerebellum as a measure of noradrenergic neuronal activity were measured at the ages of 14 weeks in SHR and normotensive Wistar rats. In 14-week old SHR, blood pressure was significantly higher than in normotensive rat, and central norepinephrine turnover rates were significantly greater in telencephalon, hypothalamus/thalamus, midbrain. There were no differences between norepinephrine turnover rates in pons/medulla, cerebellum of SHR and those of normotensive rats.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1463-1472
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• 2008

The present paper to relate with the maintenance of the high-speed vehicle, KTX and is to treat a reliability evaluation. The reliability of the high-speed vehicle while operating between-failure average mileage (MKBSF) and parts between-failure average mileage (MKBF), 1,000,000 per km service failure number of items and availability and per km evaluated a maintenance expense. The reliability evaluation results and 2007 year reliability management indexes compared in 2006 years and they improved, per km the maintenance expense compared at 2006 and 36.6% was decreased. Reliability management activity leads and availability of the high-speed vehicle, safety improves and with the fact that will be able to decrease the maintenance expense which is an economic scale of railroad service is expected.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1-5
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• 2009

Recently, as a method of green-development and reduction of carbon dioxide emission, increased interest has been focused on a railway. Furthermore, an intensive study has been processed on capabilities of maintenance activities, economic efficiency of maintenance on rail structure and a design of railway structure as well as the development of materials. The purpose of this paper is to develop a deteriorated model of PC Beam Bridge due to timely changes and maintenance activities. Typically, there is definite difference between maintained bridges and non-maintained bridges. As a result of proper maintenance activity, a life time of a structure can be enhanced. In this study, we will research and analyze structures with ongoing maintenance. We will also process same procedures on structures without maintenance. Therefore, we can establish the significant role in a conditional change of a structure. Based on a study, we accomplish the development of a condition-deteriorated model. To develop deteriorated model of PC Beam Bridge, We apply Marcov Theory and develop a transition probability to show the life time of bridge. This study will provide a great benefit to decision making for maintenance activities on the railway bridges for future.

• 대한약리학회:학술대회논문집
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• 2006.10a
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• pp.108.2-108.2
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• 2006