• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.378-382
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• 2008

A 50 N monopropellant thruster being developed for attitude control in a variety of aerospace application systems is described in this paper. Ninety percent hydrogen peroxide was selected as a propellant, since it is much less hazardous than hydrazine. A scaled down thruster with aluminum oxide loaded with the platinum in the reaction chamber was tested to determine propellant decomposition onto a catalyst. A scaled up 50 N thruster, with a catalyst bed of 3 cm in diameter and 4 cm in length, was evaluated by decomposition efficiency based on temperature, ${\eta}_T$, efficiency of characteristic velocity, ${\eta}_{C^*}$, and measurement of thrust. The performance of a 50 N thruster was 40.5 Newton in thrust, about 100 % in ${\eta}_T$, and 98 % in ${\eta}_{C^*}$, and 125 sec in specific impulse at sea level.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.906-911
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• 2006

Since railway system has been developed, the interface system which is interfaced with various sub-systems of railway including rolling stock, SIG, COM, catenary system came out more complicated and mixed-up. For the purpose of improving the management techniques about interface system among the sub-systems of railway, this paper proposes method of management by using of SE(system engineering) that makes structure of data system through describing and separating the user's requirements, functional analysis and interface of the train control system in its degree. This study is focused on the ATC signaling sub-system, a important part of SE, to analysis of the system.

• Journal of the Korean Society of Systems Engineering
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• v.11 no.2
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• pp.13-29
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• 2015

With the era of big data, the big data has been expected to have a large impact in the NPP safety areas. Although high interests of the big data for the NPP safety, only a limited researches concerning this issue are revealed. Especially, researches on the logical/physical structure and systematic design methods for the big data platform for the NPP safety were not dealt with. In this research, we design a new big data pilot platform for the NPP safety especially focusing on health monitoring and early warning services. For this, we propose a tailored design process based on SE approaches to manage inherent high complexities of the platform design. The proposed design process is consist of several steps from elicitate stakeholders to integration test via define operational concept and scenarios, and system requirements, design a conceptual functional architecture, select alternative physical modules for the derived functions and assess the applicability of the alternative modules, design a conceptual physical architecture, implement and integrate the physical modules. From the design process, this paper covers until the conceptual physical architecture design. In the following paper, the rest of the design process and results of the field test will be shown.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.432-435
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• 2002

The ultimate study of this research is to improve the properties of digital X-ray receptor based on amorphous selenium. There are being two prominent studying for Digital Radiography. Direct and Indirect method of Digital Radiography are announced for producing high quality digital image. But each two systems have strength and weakness. This is a basic research for developing of Hybrid digital radiography which is a new type X-ray detector. ln this study, we investigated the electrical characteristic of multi-layer$(CaWO_4+a-Se)$ as a photoconductor according to the changing iodine composition ratio. The iodine composition ratio of a-Se compound is classified into 5 different kinds which have 30ppm, 100ppm, 300ppm, 500ppm, 700ppm and were made test sample throught thermo-evaporation. The phosphor layer of $CaWO_4$ was overlapped on a-Se using EFIRON optical adhesives. We measured the dark and photo current about the test sample and compared the electrical characteristic of the net charge and signal-to-noise ratio. Among other things, test sample of compound material of 700ppm iodine showed good characteristic of $2.53nA/cm^2$ dark current and $479nC/cm^2{\cdot}mR$ net charge at $3V/{\mu}m$.

• Journal of the Korean Society of Systems Engineering
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• v.13 no.2
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• pp.34-41
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• 2017

The Pyro project, one of the large national R&D project to construct Korea Advanced Pyroprocessing Facility (KAPF), which has many goals such as development of pyro technology and process equipment, design of equipment and facility, construction, and test operation, is now under research and development. To reduce uncertainty and risk of such complex project, the technical management processes in systems engineering standards and NASA handbook were reviewed, and then the ten common technical management processes were selected for the large national R&D project to meet its goal successfully. And the essential technical management processes were finally suggested for Pyro project in consideration of current situation of the project.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.4
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• pp.433-444
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• 2008

With development of RFID technology, medicine and national defense as well as logistics and distribution industries have tried to adopt RFID system. Small projects as well as large national projects have planned to adopt the new technology. However, a lot of companies that have promoted a RFID-based project have confronted many problems due to a lack of information about demonstration projects and absence of systematic guideline. Therefore, it's urgent to develop a practical and useful guideline for companies that have considered to adopt the RFID system. In this paper, a practical framework to adopt RFID system is suggested by five phases : establishment of project plan, analysis of objectives, selection of equipments, development/installation, and operation/post management phases. Besides, a detail method by each stages is also given. A systematic RFID system adoption procedure has been defined through an analysis on demonstrated projects and interview with an expert and the adoption method by stage has been suggested. The purpose of this paper is to minimize the entry barriers by suggesting a practical RFID adoption procedure.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.6
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• pp.562-576
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• 2013

Power TAC (Power Trading Agent Competition) is an agent-based simulation for competitions between electricity brokering agents on the smart grid. To win the competition, agents obtain electricity from the electricity wholesale market among the power plants. In this operation, a key to success is balancing the demand of the customer and the supply from the plants because any imbalance results in a significant penalty to the brokering agent. Given the bidding on the wholesale market requires the price and the quantity on the electricity, this paper proposes four different price estimation strategies: exponentially moving average, linear regression, fuzzy logic, and support vector regression. Our evaluations with the competition simulation show which strategy is better than which, and which strategy wins in the free-for-all situations. This result is a crucial component in designing an electricity brokering agent in both Power TAC and the real world.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.27 no.4
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• pp.1-6
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• 2004

For a given plant design, improved decisions on when to shutdown an existing plant may be obtained by making better predictions of failure rates, by exerting efforts to collect more relevant information or by improving decision making models which put that information to best use. It is important that the models include the value of possible loss of lives and fear along with cleanup, decommissioning, relocation if the decisions derived from the model are to be useful. The decision model we have described enables us to investigate a class of optimal decisions on whether to shutdown or continue operating one period of time. The analysis and decision process is repeated at the end of each period with additional information about new costs and risks.

• Journal of the Korean Society of Systems Engineering
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• v.18 no.2
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• pp.75-93
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• 2022

Machine learning (ML) data-driven meta-model is proposed as a surrogate model to reduce the excessive computational cost of the physics-based model and facilitate the real-time prediction of a nuclear power plant's transient response. To forecast the transient response three machine learning (ML) meta-models based on recurrent neural networks (RNNs); specifically, Long Short Term Memory (LSTM), Gated Recurrent Unit (GRU), and a sequence combination of Convolutional Neural Network (CNN) and LSTM are developed. The chosen accident scenario is a control element assembly withdrawal at power concurrent with the Loss Of Offsite Power (LOOP). The transient response was obtained using the best estimate thermal hydraulics code, MARS-KS, and cross-validated against the Design and control document (DCD). DAKOTA software is loosely coupled with MARS-KS code via a python interface to perform the Best Estimate Plus Uncertainty Quantification (BEPU) analysis and generate a time series database of the system response to train, test and validate the ML meta-models. Key uncertain parameters identified as required by the CASU methodology were propagated using the non-parametric Monte-Carlo (MC) random propagation and Latin Hypercube Sampling technique until a statistically significant database (181 samples) as required by Wilk's fifth order is achieved with 95% probability and 95% confidence level. The three ML RNN models were built and optimized with the help of the Talos tool and demonstrated excellent performance in forecasting the most probable NPP transient response. This research was guided by the Systems Engineering (SE) approach for the systematic and efficient planning and execution of the research.

• Smart Structures and Systems
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• v.10 no.3
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• pp.271-298
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• 2012

Researchers have made significant progress in recent years towards realizing effective structural health monitoring (SHM) utilizing wireless smart sensor networks (WSSNs). These efforts have focused on improving the performance and robustness of such networks to achieve high quality data acquisition and distributed, in-network processing. One of the primary challenges still facing the use of smart sensors for long-term monitoring deployments is their limited power resources. Periodically accessing the sensor nodes to change batteries is not feasible or economical in many deployment cases. While energy harvesting techniques show promise for prolonging unattended network life, low power design and operation are still critically important. This research presents the WiSeMote: a new, fully integrated ultra-low power wireless smart sensor node and a flexible base station, both designed for long-term SHM deployments. The power consumption of the sensor nodes and base station has been minimized through careful hardware selection and the implementation of power-aware network software, without sacrificing flexibility and functionality.