• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.804-809
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• 2008

In this study, the cooling performance of a C/C composite material structure with metallic cooling tubes fixed by elastic force without chemical bonding was evaluated experimentally using combustion gas in a rocket combustor. The C/C composite chamber was covered by a stainless steel outer shell to maintain its airtightness. Gaseous hydrogen as a fuel and gaseous oxygen as an oxidizer were used for the heating test. The surface of these C/C composites was maintained below 1500 K when the combustion gas temperature was about 2900 K and heat flux to the combustion chamber wall was about 9 $MW/m^2$. No thermal damage was observed on the stainless steel tubes which were in contact with the C/C composite materials. Results of the heating test showed that such a metallic-tube-cooled C/C composite structure is able to control the surface temperature as a cooling structure(also as a heat exchanger), as well as indicating the possibility of reducing the amount of the coolant even if the thermal load to the engine is high. Thus, application of the metallic-tube-cooled C/C composite structure to reusable engines such as a rocket-ramjet combined cycle engine is expected.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.251-252
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• 2015

Enough school facility maintenance data should be accumulated in a database or data warehouse in order to supply information about school facility correct maintenance budget plan, budget assignment, and cycle and rate of maintenance or replacement. For those, this research analyze the present school facility maintenance practice and budget and construction cost structure. In order to solve the problems, this study analyze the present practice of maintenance and replacement and obtain LCC(Life cycle cost) data, perform expert interview and then establish construction work breakdown structure of maintenance of educational facility by combining work breakdown structure(WBS) and cost breakdown structure(CBS).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.2
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• pp.288-292
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• 2013

This paper presents the result of life-cycle cost (LCC) estimation for domestic products propulsion control system (motor block unit) of KTX-1 considering periodic maintenance. Life cycle costing is one of the most effective approaches for the cost analysis of long-life systems such as the KTX-1. Life cycle costing includes the cost of concept design, development, manufacture, operation, maintenance and disposal. To estimate LCC for domestic products motor block unit, it was analyzed physical breakdown structure (PBS) on motor unit in view of maintenance cost and unit cost etc. As a results, life cycle cost on motor block unit increased moderately expect for periodical time when major parts are replaced at the same time. hereafter this results will be reflected in the domestic products being developed.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.447-452
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• 2014

This paper presents the effects of pulse plasma parameters such as duty cycle and pulse frequency on the properties of TiAlN coatings deposited by asymmetric bipolar pulsed DC magnetron sputtering systems. The results show that, with decreasing duty cycle and increasing pulse frequency, the coating morphology changes from a columnar structure to a dense structure with finer grains. Pulsed sputtered TiAlN coatings showed higher hardness, higher residual stress, and smaller grain sizes than did DC prepared TiAlN coatings. Moreover, residual stress and nanoindentation hardness of pulsed sputtered TiAlN coatings increased with increasing pulse frequency. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 50 kHz.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.148-153
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• 2023

A digital controller uses a microprocessor and is a controller implemented as a program. This method has the advantage of being more maintenance-friendly than existing analog controllers. However, it inevitably requires computation time to execute the internal program. Therefore, the digital controller uses a method of controlling the system at a certain cycle by considering this time, and this cycle is very closely related to the performance of the microprocessor used. In other words, in the case of very high performance, this control cycle can be shortened to near real time, but this may result in a disadvantage in terms of cost. In this paper, we propose a method to solve this problem by implementing two processors with slightly lower performance in a control system in a series-parallel structure. For this purpose, we will use a digital distributed control system and implement an experimental system to examine its effectiveness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.19-25
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• 2016

Engineering structures including civil infrastructures require a life-cycle cost and benefit during their service lives. The service life of a structure can be extended through appropriate inspection and maintenance actions. In general, this service life extension requires more life-cycle cost and cumulative benefit. For this reason, structure managers need to make a rational decision regarding the service life management considering both the cost and benefit simultaneously. In this paper, the probabilistic decision tool to determine the optimal service life based on cost-benefit analysis is presented. This decision tool requires an estimation of the time-dependent effective cost-benefit under uncertainty to formulate the optimization problem. The effective cost-benefit is expressed by the difference between the cumulative benefit and life-cycle cost of a deteriorating structure over time. The objective of the optimization problem is maximizing the effective cost-benefit, and the associated solutions are the optimal service life and maintenance interventions. The decision tool presented in this paper can be applied to any deteriorating engineering structure.

• Journal of Korean Institute of Industrial Engineers
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• v.42 no.3
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• pp.241-248
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• 2016

Plant life cycle consists of design, construction, certification, operation, and maintenance phases, and various and enormous plant life cycle data is involved in each phase. Plant life cycle data should be linked with each other based on its proper relationships, so that plant operators can access necessary plant data during their regular operations and maintenance works. Currently, the relationships of plant life cycle data may not be defined explicitly, or they are scattered over several plant information systems. This paper proposes high level design of a plant life cycle data management system based on pre-defined plant life cycle database design. ISO-15926 standard is adapted for the database design. User-interface designs of the plant life cycle data management system are explained based on analysis of plant owners' requirements. A conceptual design of the database is also described with the entity-relationship diagram.

• Nuclear Engineering and Technology
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• v.45 no.5
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• pp.653-664
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• 2013

The design of computer-based instrumentation and control (I&C) systems is determined by the allocation of I&C functions to I&C systems and components. Due to the characteristics of computer-based technology, component failures can negatively affect several I&C functions, so that the reliability proof of the I&C systems requires the accomplishment of I&C system design analyses throughout the I&C life-cycle. On one hand, this paper proposes the restructuring of the sequential IEC 61513 I&C life-cycle according to the V-model, so as to adequately integrate the concept of verification and validation. On the other hand, based on a metamodel for the modeling of I&C systems, this paper introduces a method for the modeling and analysis of the effects with respect to the superposition of failure combinations and event sequences on the I&C system design, i.e. the temporal change of physical structure is analyzed. In the first step, the method is concerned with the modeling of the I&C systems. In the second step, the method considers the analysis of temporal change of physical structure, which integrates the concepts of the diversity and defense-in-depth analysis, fault tree analysis, event tree analysis, and failure mode and effects analysis.

• Journal of the Korea Society of Computer and Information
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• v.25 no.9
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• pp.63-69
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• 2020

Image-image translation is a technology that creates a target image through input images, and has recently shown high performance in creating a more realistic image by utilizing GAN, which is a non-map learning structure. Therefore, there are various studies on image-to-image translation using GAN. At this point, most image-to-image translations basically target one attribute translation. But the data used and obtainable in real life consist of a variety of features that are hard to explain with one feature. Therefore, if you aim to change multiple attributes that can divide the image creation process by attributes to take advantage of the various attributes, you will be able to play a better role in image-to-image translation. In this paper, we propose Multi CycleGAN, a dual attribute transformation structure, by utilizing CycleGAN, which showed high performance among image-image translation structures using GAN. This structure implements a dual transformation structure in which three domains conduct two-way learning to learn about the two properties of an input domain. Experiments have shown that images through the new structure maintain the properties of the input area and show high performance with the target properties applied. Using this structure, it is possible to create more diverse images in the future, so we can expect to utilize image generation in more diverse areas.

• Journal of Embryo Transfer
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• v.24 no.3
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• pp.159-167
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• 2009

Ultrasonographic examination was performed to observe the ultrasonographic image of Korean native cows' normal uterus in condition of in vitro and in vivo. The experiment was done 28 slaughtered cows' uterus using immersed in water in vitro, and 41 healthy breeding cows taken rectal ultrasonography in vivo. Ultrasonographic examination of uterine was taken on the reference of cross section of intercornual ligaments' cranial. Each uterus on the experiments was compared by estrous cycle and ultrasonographic frequency. The uterine structure using ultrasonography was 5 layers of uterine horn in vivo as well as in vitro. Uterine horn was observed to be distinguished from inside to outside as endometrium to inner echogenic layer, circular muscle layer to slightly echogenic elliptical layer, stratum vasculare to central echogenic layer, longitudinal muscle layer to slightly echogenic arched layer, and perimetrium to outer echogenic layer, respectively. According to the observation of uterus related to estrous cycle and ultrasonographic examination, uterine endometrium in vitro was constantly founded irrespective of estrous cycle and ultrasonographic frequency. On the low frequency, endometrium and circular muscle layer in estrus were prone to distinguished than in diestrus. On the high frequency, endometrium and circular muscle layer were always distinguished regardless of estrous cycle. In vivo, uterine endometrium and circular muscle layer were observed regardless of estrus and ultrasonographic frequency. On the low frequency, stratum vasculare and longitudinal muscle layer were not likely to be distinguished in diestrus, but estrus. On the high frequency, stratum vasculare and longitudinal muscle layer were observed regardless of estrous cycle. Also, every uterine structure was easily distinguished on high frequency than low frequency owing to precision of distinction in layers. The difference of results followed by the experiments conditions between in vitro and in vivo was that uterine endometrium and circular muscle layer in diestrus in vitro were difficult to be distinguished and uterine lumen was observed during whole estrous cycle. In vivo, It was founded that the distinction of stratum vasculare and logitudinal muscle layer in diestrus was complicated and uterine lumen was observed during only estrus. In view of the result so far achieved, normal uterine structure divided in 5 layers on ultrasonography was accorded with microscopic organization, uterine structure was likely to be observed during estrus than diestrus, high frequency checkup than low frequency, and uterine endometrium, circular muscle, stratum vasculare was easily observed regardless of estrous cycle and ultrasonographic frequency.