• Journal of KIISE:Software and Applications
• /
• v.36 no.6
• /
• pp.451-461
• /
• 2009

The Adaptive Random Testing(ART) aims to improve the performance of traditional Random Testing(RT) by reducing the number of test cases to find the failure region which is located in the input domain. Such enhancement can be obtained by efficient selection algorithms of test cases. The ART through Iterative Partitioning(IP-ART) is one of ART techniques and it uses an iterative input domain partitioning method to improve the performance of early-versions of ART which have significant drawbacks in computation time. And the IP-ART with Enlarged Input Domain(EIP-ART), an improved version of IP-ART, is known to make additional performance improvement with scalability by expanding to virtual test space beyond real input domain of IP-ART. The EIP-ART algorithm, however, have the drawback of heavy cost of computation time to generate test cases mainly due to the virtual input domain enlargement. For this reason, two algorithms are proposed in this paper to mitigate the computation overhead of the EIP-ART. In the experiments by simulations, the tiling technique of input domain, one of two proposed algorithms, showed significant improvements in terms of computation time and testing performance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.390-397
• /
• 2019

A mechanical model of band sawing saw frame was established according to an analysis of a commonly used saw-frame structure diagram to overcome the problems of low service life, substandard cutting precision and efficiency, and high manufacturing cost caused by the unreasonable design of saw frame. Taking a particular type of sawing machine as an example, stress cycle analysis of the saw blade was carried out according to the mechanical model of the saw frame, and the fatigue analysis model of the most dangerous cross-section point that was most prone to fatigue failure of the saw blade was then established. The fatigue analysis result was used as the basis for the improved design of the saw frame, and the improved detailed saw-frame design parameters were obtained. The results suggested that the saw frame system is much more compact and the saw blade force met the fatigue strength requirements through the improved design. In addition, the service life of the saw blade and the cutting precision were increased. The established mechanical model of the saw frame in this paper is used widely and has high practical application values.

• Journal of the Korea Concrete Institute
• /
• v.17 no.2 s.86
• /
• pp.171-177
• /
• 2005

Even though the cost associated with the repair and rehabilitation of existing structures are rapidly increasing, vast number of the repaired and rehabilitated structures do not function properly as expected during their remaining service lives. This paper focused on the flexural behavior of reinforced concrete slabs repaired and reinforced by PS strand and polymer mortar in the tension face. The slabs have the size of 700${\times}120{\times}$2200 m and 700${\times}120{\times}$1300 mm. Variables of experiment were space of strengthening, chipping, the number of strand, the kind of mortar in this experimental study. Attention is concentrated upon overall bending capacity, deflection, ductility and failure mode of repaired and reinforced slabs. Test results show that deflection of repaired and reinforced slabs reduced to approximately $40 \%$ comparison to standard slabs. Boundary cracking of chipping slab started ultimate load afterward. Concrete-mortar interface cracked 64.5 kN in repaired slab with AP mortar and 36.0 kN in repaired slab with general polymer mortar. Reinforcement effect increased with reducing space of strand. Also, Reinforcement effects are more by strand than by polymer mortar.

• Journal of the Korea Society for Simulation
• /
• v.32 no.3
• /
• pp.55-66
• /
• 2023

In recent years, naval vessels have been developed to fulfill a variety of missions by being equipped with various cutting-edge equipment and ICT technologies. One of the main missions of Korean naval vessels is anti-ballistic missile warfare to defend key units and areas against the growing threat of ballistic missiles. Because the process of detection and interception is too complex and the cost of failure is much high, a lot of preparation is required to effectively conduct anti-ballistic missile warfare. This paper describes the development of a simulation model of anti-ballistic missile warfare with combat systems and equipment to be installed on future naval vessels. In particular, the DEVS formalism providing a modular and hierarchical modeling manner was applied to the simulation model, which can be utilized to efficiently represent various anti-ballistic missile warfare situations. In the simulation results presented, experiments were conducted to analyze the effectiveness of the model for effective detection resource management in anti-ballistic missile warfare. This study is expected to be utilized as a variety of analysis tools necessary to determine the optimal deployment and configuration of combat resources and operational tactics required for effective anti-ballistic missile warfare of ships in the future.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.6
• /
• pp.26-32
• /
• 2016

Usually, there are many uncertainties regarding the error of an assumed load, material properties, member size, and structure analysis in a structure, and it may have a direct influence on the qualities of optimal design of structures. Probabilistic analysis has developed rapidly into a desirable process and structural reliability analysis is an increasingly important tool that assists engineers to consider uncertainties during the design, construction and life of a structure to calculate its probability of failure. This study deals with the applications of two optimization techniques to solve the reliability-based optimization problem of structures. The reliability-based optimization problem was formulated as a minimization of the structural volume subject to the constraints on the values of componential reliability index determined by the AFOSM approach. This presented method may be a useful tool for the reliability-based design optimization of structures.

• Management & Information Systems Review
• /
• v.28 no.4
• /
• pp.27-44
• /
• 2009

Economic value of a certain technology is of great interest and importance in a wide variety of investment circumstances. These vary from companies considering investing in R&D projects, to venture capitalists funding start-up companies. However, such valuation is extremely difficult in any case, and the cost of failure can be very high. Many techniques have been proposed to assist managers facing this issue, from traditional discounted cash flow analysis to more recent methods based on real options. In the meantime, the discounted cash flow method has limitations in applying the valuation of technology. At the same time, there have been various solutions to overcome theoretical problems of the method. Real options have been thought as a solution. However, there are another problems in using them in real world. This paper reviews the previous studies on the valuation of technology in several aspects, discusses the practicability of the various methods available, and explore the application of a hybrid model, which aims to make these rather aore the ideas more accessible to practicing managers.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.3
• /
• pp.290-297
• /
• 2017

The flexural behavior tests of UHPC segmental U-girder and composite U-girder which has 160MPa compressive strength and 15.4m length were carried out. The test variables are volume fraction of steel fibers and slab over the U-girder. Each U-girder has longitudinal re-bars in web and lower flange. PS tendons which has 2 of 15.2mm diameter in upper flange and PS tendons which has 7 of 15.2mm diameter in lower flange were arranged and prestressed at onetime in U-girder connection stage. Enough strong prestressing force which applied to U-girder due to ultra high performance concrete strength can withstand the self weight and dead load in U-girder stage. By comparison with the brittle behavior of U-girder, composite U-girder showed the stable and ductile behavior. After the construction of slab over U-girder, flexural load capacity of composite U-girder can bear the design load in final construction stage with only one time prestressing operation which already carried out in U-girder stage. This simple prestressing method due to the ultra high strength concrete have the advantage in construction step and cost. The shear key which has narrow space has the strong composite connection between ultra high strength concrete U-girder and high strength concrete slab didn't show any slip and opening right before failure load.

• Environmental and Resource Economics Review
• /
• v.23 no.4
• /
• pp.583-615
• /
• 2014

Including the rolling black out in 2011, Korea has suffered from rapid increase of electricity consumption and demand forecasting failure for last five years. In addition, because of the Fukushima disaster, high fuel prices, and introduction of new generation sources such as renewables, the uncertainty on a power supply strategy increases. Consequently, a stable power supply becomes the new agenda and a revisino of strategy for new power generation sources is needed. In the light of this, we appraises the sixth basic plan for long term electricity demand and supply considering the changes of foreign and domestic conditions. We also simulate a strategy for the new power generation sources using a portfolio analysis method. As results, a diversity of power generation sources will increase and the share of renewable power generation will be surged on the assumptions of a cost reduction of renewable power sources and an increase of fuel costs. Particularly, on the range of a risk level(standard deviation) from 0.06 and 0.09, the efficient frontier has the most various power sources. Besides, the existing power plan is not efficient so that an improvement is needed. Lastly, the development of an electricity storage system and energy management system is necessary to make a stable and efficient power supply condition.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.2
• /
• pp.71-78
• /
• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• Journal of the Korea Concrete Institute
• /
• v.17 no.3 s.87
• /
• pp.335-342
• /
• 2005

In this paper, fundamental properties of Polymer Concrete(PC), made from unsaturated polyester resin based on recycled PET and recycled aggregate were investigated. Mechanical properties include strength, modulus of elasticity, and chemical resistance. Resins based on recycled PET and recycled aggregate offer the possibility of low source cost for forming useful products, and would also help alleviate an environmental problem and save energy. The results of test for resin contents and recycled aggregate ratio we, first, the strength of Polymer Concrete made with resin based on recycled PET and recycled aggregate increases with resin contents relatively, however beyond a certain resin contents the strength does not change appreciably, Second, the relationship between the compressive strength and recycled aggregate ratio at resin $9\%$ has a close correlation linearly whereas there is no correlation between the compressive strength and the flexural strength of RPC with recycled aggregate ratio. Third, the effect of acid resistance at resin $9\%$ was found to be nearly unaffected by HCI, whereas the PC with $100\%$ recycled aggregate showed poor acid resistance. Unlike acid, alkali nearly does not seem to attack the RPC as is evident from the weight change and compressive strength. And last, In case of stress-strain curve of polymer concrete with $100\%$ of natural aggregate and $100\%$ recycled aggregate it is observed the exceptional behavior resulting in different failure mechanisms of the material under compression.