• Journal of the Korea Society for Simulation
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• v.24 no.4
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• pp.119-125
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• 2015

This research has conducted high availability system modeling to assure the reliability of shipboard combat systems. Shipboard combat system is a way for efficient execution of duty and a crucial battlefield management system that determines the outcome of battle in the modern war. Especially in regard to a network-centric operational environment in the future, even 1% of malfunction can lead to fatal consequences for the outcome of war. So combat system should be designed by high availability system which is a "always-on" service. In this point of view, This work describes an architecture-based various high availability model and proposed alternative high available systems that can achieve more than 99.9999% accuracy at a minimum. This paper also provides an applicable model with which system engineers analyze out system failure and recovery process by employing computerized tools.

• Journal of Computational Design and Engineering
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• v.3 no.2
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• pp.140-150
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• 2016

Normally all manufacturing and fabrication processes introduce residual stresses in a component. These stresses exist even after all service or external loads have been removed. Residual stresses have been studied elaborately in the past and even in depth research have been done to determine their magnitude and distribution during different manufacturing processes. But very few works have dealt with the study of residual stresses formation during the casting process. Even though these stresses are less in magnitude, they still result in crack formation and subsequent failure in later phases of the component usage. In this work, the residual stresses developed in a shifter during casting process are first determined by finite element analysis using ANSYS(R) Mechanical APDL, Release 12.0 software. Initially the analysis was done on a simple block to determine the optimum element size and boundary conditions. With these values, the actual shifter component was analyzed. All these simulations are done in an uncoupled thermal and structural environment. The results showed the areas of maximum residual stress. This was followed by the geometrical optimization of the cast part for minimum residual stresses. The resulting shape gave lesser and more evenly distributed residual stresses. Crack compliance method was used to experimentally determine the residual stresses in the modified cast part. The results obtained from the measurements are verified by finite element analysis findings.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.809-815
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• 2011

An experimental investigations on the bond-slip properties of the steel and Glass Fiber Reinforced Polymer(GFRP) bars in engineered cementitious composite (ECC) with Polyvinyl Alcohol (PVA) fibers are presented. Total of 8 beam specimens prepared according to the Rilem procedures with 2% of PVA and PE fiber volume percentage and steel and GFRP reinforcements significantly changed the failure mechanism and slightly improved bond strength. The main objective of the tests was to evaluate the load versus displacement and load versus slip behaviors and the bond strength for the following parameters: concrete type (normal and fiber concrete) and bar diameter (10 and 13 mm). The study results showed that ordinary concrete and ECC specimens showed similar behavior for steel reinforced specimen. However, GFRP reinforced specimen showed different behavior that the steel specimen. The code analytical results showed more accuracy compared to the experimental results as expected in conservative code provisions. Based on the obtained results, it is safe to conclude that the new parameters need to be adopted to ensure safe usage of ECC for construction applications.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.227-239
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• 2006

Reliability prediction provides a rational basis for design decisions such as the choice between alternative concepts, choice of part quality levels, derating factors to be applied, use of proven versus state-of-the-art techniques, and other factors. For this reasons, reliability prediction is essential functions in developing space systems. The worth of the quantitative expression lies in the information conveyed with the numerical value and the use which is made of that information and reliability prediction should be initiated early in the configuration definition stage to aid in the evaluation of the design and to provide a basis for item reliability allocation (apportionment) and establishing corrective action priorities. Reliability models and predictions are updated when there is a significant change in the item design availability of design details, environmental requirements, stress data, failure rate data, or service use profile. In this paper, the procedure, selection of reliability data and methods for space system reliability prediction is presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1069-1072
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• 2008

As embedded reinforcing suffer from corrosion process, the bond strength and stiffness are reduced, and the structure proceed, eventually, to the deterioration of the concrete, shortening the service life of concrete structures rapidly. In order to deal with these problems, a multitude of researches have been carried out up to this date to evaluate the bond characteristics of RC members, i.e. by artificially inducing rapid corrosion of the reinforcing bar. These artificial corrosion methods, however, could not represent the real condition, resulting in the possibility of overestimation for the RC members in real situation. Accordingly, the purpose of this paper is to investigate the difference in the bond characteristics for RC members corroded by different corrosion methods (artificial rapid method, natural method). For the case of natural corrosion, the brittle failure was observedeven for the case of the area ofcorrosion of 50%. And, the bond strength decreased by about 10% or more for the caseofspecimens with the area of corrosion of 80% or above. Especially, the deterioration of concrete starts at the state of low corrosion level for the case of natural corrosion. Thus, the safety of RC members must be assessed and evaluated more carefully for the naturally corroded members than for the RC concrete members corroded rapidly by artificial method.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.333-336
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• 2008

CFRP tendons have been attempted in concrete structures as a substitute for steel tendons considering their many advantages such as the corrosion-resistance, light weight etc. However, the elastic behavior up to failure is likely to result in ductility problems. To overcome such problems, prestress concrete beams with partially bonded tendons have been developed and suggested. In this new system, the un-bonded part near the mid-span contributes to the improvement of ductility. And the bonded parts at both ends play a role as a safe anchorage. According to the previous research on the static behavior, the suggested method has demonstrated enough ductility and strength. However it is essential to verify the long-term safety for repetitive fatigue loads under service states. For this purpose, flexural fatigue loading tests were carried out in this research. This paper includes an experimental investigation on the static load-carrying capacities of the beams with or without fatigue tests. The results showed that the beams prestressed with partially bonded CFRP tendons possessed good fatigue capacity under the constant cyclic loads.

• Journal of the HCI Society of Korea
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• v.7 no.2
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• pp.11-16
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• 2012

R&D Strategic Planning plays a crucial role in determining success or failure of R&D. However, current automatic services for supporting the purpose merely provide fragmentary quantitative/qualitative analytics, and force domain experts to carry out further manual analysis by themselves. Thus, this study aims at automatically supporting R&D strategic planning with efficiency and effectiveness. To achieve the goal, we design major services in the viewpoint of the relationship between technology and R&D actor, which are essential elements in R&D. 'Trends and Predictions', 'Technology Levels', 'Relationship Paths', 'Roadmaps', and 'Competitors and Collaborators' services were designed and implemented on about 15 millions papers and patents. Future works will include the support of higher level in the hierarchy of strategic intelligence.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.4
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• pp.655-667
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• 2014

A disaster is the time-excess case that computerized service can tolerate a failure and financial industry is being set up the disaster recovery system based on the disaster recovery plan and the business continuity plan for preparing these disasters. However, existing system can not guarantee the business continuity when it comes to cyber terror. This paper analyzes the building type and building technology of disaster recovery system for the financial fields. Also this paper explain the type of data backup using online redo log and type of archive log backup using WORM storage. And this paper proposes the model of improved data recovery combining above two types. Lastly this paper confirm the effectiveness and reliability for proposal rocovery model through the implementation of the test environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2508-2519
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• 1994

In this thesis, two possible schemes for power feeding are considered. The first one is the network power feeding, and the other is the power feeding from the rechargeable battery. Though each scheme has its merits and demerits, the domestic network operator has proposed the latter due to the large deviation of line resistance, high power loss, and safety. This scheme, however, has several problems. The usage is limited by the life of battery leading to the failure of minimal voice service for many hours. The space occupation of that battery is another serious problem. Moreover, the network opeator should have overhead of maintenance and repair. In order to alleviate such the difficulties, the sealing current is introduced through the subscriber loop. Flowing the current into the loop prevents from rusting. This thesis designs a power controller using PEB2025 to control various amount, duration, and period of this sealing current, to achieve the optimum current supply for sealing.

• Smart Structures and Systems
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• v.17 no.6
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• pp.917-933
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• 2016

In a prestressed concrete bridge, the magnitude of the prestress force (PF) decreases with time. This unexpected loss can cause failure of a bridge which makes prestress force identification (PFI) critical to evaluate bridge safety. However, it has been difficult to identify the PF non-destructively. Although some research has shown the feasibility of vibration based methods in PFI, the requirement of having a determinate exciting force in these methods hinders applications onto in-service bridges. Ideally, it will be efficient if the normal traffic could be treated as an excitation, but the load caused by vehicles is difficult to measure. Hence it prompts the need to investigate whether PF and moving load could be identified together. This paper presents a synergic identification method to determine PF and moving load applied on a simply supported prestressed concrete beam via the dynamic responses caused by this unknown moving load. This method consists of three parts: (i) the PF is transformed into an external pseudo-load localized in each beam element via virtual distortion method (VDM); (ii) then these pseudo-loads are identified simultaneously with the moving load via Duhamel Integral; (iii) the time consuming problem during the inversion of Duhamel Integral is overcome by the load-shape function (LSF). The method is examined against different cases of PFs, vehicle speeds and noise levels by means of simulations. Results show that this method attains a good degree of accuracy and efficiency, as well as robustness to noise.