• International Journal of Aerospace System Engineering
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• v.6 no.2
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• pp.11-16
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• 2019

A system analysis program has been developed for a gas generator cycle liquid rocket engine of 30 ton class. Numerical models have been proposed for a combustor, a turbopump, a gas generator and pressure drop through a regenerative cooling system. Numerical algorithm has been validated by comparing with the published data of MC-1. The major source of error is not the numerical algorithm but the imperfect performance models of subsystems. So the precision of the program can be improved by revising the performance models using experimental data. The sea level specific impulse and vacuum specific impulse have been demonstrated for a 30 ton class gas generator engine. The optimal condition of combustor pressure and mixture ratio for specific impulse which is a typical characteristic of a gas generator cycle engine has been illustrated.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.18-24
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• 2018

This paper focuses on systematic design about the membership ranges of the main design factors such as control error, control error rate, and sampling time for the fuzzy logic control of the variable speed drive refrigeration cycle. The upper and the lowest limit of the membership ranges are set up from the data of static characteristics obtained by experiments. Three kinds of membership ranges on the control error and the control error rate are tested by experiments. Especially, an effect of sampling time on control performance is also investigated in the same way. Experimental data showed the control error rate and the sampling time strongly effected on the control performance of the refrigeration cycle with a variable speed drive.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.387-392
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• 2002

It is very important to measure linear cycle plane positioning accuracy of NC lathes as they affect those of all other machines machined by them in industries. For example, if the linear cycle plane positioning accuracy of each axes directions is bad, the accuracy of works will be wrong and the change-ability will be bad in the assembly of machine parts. In this paper, computer software systems are organized to measure linear displacements of ATC(Automatic tool changer) of NC lathes using linear scale and time pulses comming out from computer in order to get data at constant time intervals from the sensors. And each sets of error data gotten from the test is expressed to plots by computer treatment and the results of linear cycle plane positioning error motion estimated to numerics by statistical treatments.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.2
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• pp.220-230
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• 2005

The purpose of this study was to compare clothing benefits and the types of fashion information sources according to family life cycle. Subjects were selected through stratified sampling technique in Seoul and suburban area. Collection of the research data was made using a self-administered questionnaire survey. Factor analysis, ANOVA, and Duncan test were used to conduct the data analysis on 562 out of 600 questionnaires. Clothing benefit variables were reduced to five factors : fashion/social status, individuality, function/comfort, figure flaws compensation, and economic value. The result showed significant differences on 3 clothing benefits(fashion/social status, individuality, and function/comfort) and 5 fashion information soures (celebrities, street fashion, T.V commercial, Internet/home shopping, fashion catalog) according to family life cycle.

• Journal of KIISE:Databases
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• v.35 no.3
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• pp.257-271
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• 2008

Wireless broadcast environments has character that a number of mobile client can receive data streaming from central server no matter how they are so many. Because it is asymmetric bandwidth in that uplink and downlink bandwidth are different. This advantage helps wireless broadcast environments is used in many applications. These applications work almost read operation and need control concurrency using transaction unit. Previous concurrency control scheme in single channel is not adapted in multi channel environments because consistency of data are broken when a mobile client tunes in a broadcast cycle in a channel and then move into another channel and listen to different broadcast cycle with already accessed broadcast cycle. In this paper, we propose concurrency control for read-only mobile transactions in multiple wireless broadcast channel. First of all, we adapt index and data dedicated channel and propose LBCPC(Longest Broadcast Cycle Per Channel) as new unit of consistency. In index dedicated channel, it is repeatedly broadcasted data in same BCPC(Broadcast Cycle Per Channel) until LBCPC. And mobile transaction executes validation using control information every LBCPC. As a result, consistency of data is kept and average response time is shorter than one in single channel because waiting time for restart reduces. And as control information is broadcasted more frequently than in single channel, it is guaranteed currency about data accessed by transaction. Finally, according to the simulation result, we verify performance of our scheme in multi channel as comparing average response time with single channel.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.584-589
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• 2006

In this paper, a test apparatus for reliability evaluation of a rotary compressor has been suggested with a short-cycle concept. $CO_2$ refrigerant is adopted for this cycle to avoid phase change during cycle operation. Evaporator is not necessary in short-cycle. Utilizing a short-cycle, the test apparatus was built on the purpose of evaluating the reliability of each rotary compressor on the conveyer belt of the factory. The primary validation of the test apparatus is discussed by analyzing the experimental heat balance data. Additional validation was performed through the overload continuous operation test where the wear rate of the $CO_2$ short-cycle was found to similar to that of the R22 normal-cycle. The reliability evaluation test apparatus with a short-cycle in present investigation was found simple and efficient in the view of reducing sample numbers, costs, and test time in analyzing the reliability of rotary compressors.

• Journal of the Korean Society of Systems Engineering
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• v.13 no.2
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• pp.9-17
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• 2017

Concept development of a real-time Field Programmable Gate Array (FPGA)-based switched Ethernet data communication network for the Man-Machine Interface System (MMIS) is presented in this paper. The proposed design discussed in this research is based on the systems engineering (SE) approach. The design methodology is effectively developed by defining the concept development stage of the life-cycle model consisting of three successive phases, which are developed and discussed: needs analysis; concept exploration; and concept definition. This life-cycle model is used to develop an FPGA-based time-triggered Ethernet (TTE) switched data communication network for the non-safety division of MMIS system to provide real-time data transfer from the safety control systems to the non-safety division of MMIS and between the non-safety systems including control, monitoring, and information display systems. The original IEEE standard 802.3 Ethernet networks were not typically designed or implemented for providing real-time data transmission, however implementing a network that provides both real-time and on-demand data transmission is achievable using the real-time Ethernet technology. To develop the design effectively, context diagrams are implied. Conformance to the stakeholders needs, system requirements, and relevant codes and standards together with utilizing the TTE technology are used to analyze, synthesize, and develop the MMIS non-safety data communication network of the APR1400 nuclear power plant.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1035-1036
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• 2010

• The Journal of Bigdata
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• v.1 no.2
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• pp.91-102
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• 2016

In traditional environments we have called the data life cycle DIKW, which represents data-information-knowledge-wisdom. In big data environments, on the other hand, we call it DIA, which represents data-insight-action. The difference between the two data life cycles results in new architecture of data resource management. In this paper, we study data resource management architecture for big data environments. Especially main components of the architecture are proposed in this paper.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.161-168
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• 2015

Recently, due to various environmental problems such as global warming, increases of international oil prices, exhaustion of resource, a paradigm of world automobile market is rapidly changing from conventional vehicles using internal combustion engine to eco-friendly vehicles using electric power such as EV, HEV, PHEV and FCEV. Generally, in order to measure fuel consumption and pollutant emissions of cars, chassis dynamometer tests are performed on various driving cycles before actual driving test. There are many driving cycles for performance evaluation of conventional vehicles. However, there is a lack of researches on driving cycle for EV. In this study, the urban driving cycle for performance evaluation of electric vehicles was developed. This study is composed of two parts. In the part 1, the urban driving cycle 'GUDC-EV(Gwacheon-city Urban Driving Cycle for Electric Vehicles)' was developed by using driving data, which were obtained through actual driving experiment, and statistic analysis with chronological table. In this paper part 2, in order to verify the developed driving cycle GUDC-EV, virtual EV platforms were configured and simulations were performed with actual driving data using In addition, simulation results were compared with existing driving cycles such as FTP-72, NEDC and Japan 10-15.