• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.11
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• pp.8-15
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• 2020

The government has announced its Hydrogen Economy Roadmap to strengthen global competitiveness on the hydrogen economy by focusing on hydrogen fuel cell electric vehicles and fuel cells. In this regard, the interest on the economics and safety of the infrastructure of hydrogen stations has also increased. In this study, a test bed similar to an actual hydrogen charging facility was built, and a prototype of a piston-type compressor was modeled. In this model, the piston was hydraulically compressed to progressively test leakage, leakage rate, and durability and to check for any malfunction. Moreover, the leakage rate, cylinder leak performance, and compressor operation durability were evaluated for safety; it was confirmed that there were no abnormalities. Nevertheless, an investigation of the long-term use and operating pressure of the compressor is necessary to verify the safety of developing a100-MPa domestic compressor in the future.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.184-187
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• 2007

Hydrogen could be produced from any substance containing hydrogen atoms, such as water, hydrocarbon (HC) fuels, acids or bases. Hydrocarbon fuels couold be converted to hydrogen-rich gas through reforming process for hydrogen production. Even though fuel cell have high efficiency with pure hydrogen from gas tank, it is more beneficial to generate hydrogen from city gas (mainly methane) in residential application such as domestic or office environments. Thus hydrogen is generated by reforming process using hydrocarbon. Unfortunately, the reforming process for hydrogen production is accompanied with unavoidable impurities. Impurities such as CO, $CO_2$, $H_2S$, $NH_3$, and $CH_4$ in hydrogen could cause negative effects on fuel cell performance. Those effects are kinetic losses due to poisoning of electrode catalysts, ohmic losses due to proton conductivity reduction including membrane and catalyst ionomer layers, and mass transport losses due to degrading catalyst layer structure and hydrophobic property. Hydrogen produced from reformer eventually contains around 73% of $H_2$, 20% or less of $CO_2$, 5.8% of less of $N_2$, or 2% less of $CH_4$, and 10ppm or less of CO. Most impurities are removed using pressure swing adsorption (PSA) process to get high purity hydrogen. However, high purity hydrogen production requires high operation cost of reforming process. The effect of carbon dioxide on fuel cell performance was investigated in this experiment. The performance of PEM fuel cell was investigated using current vs. potential experiment, long run (10 hr) test, and electrochemical impedance measurement when the concentrations of carbon dioxide were 10%, 20% and 30%. Also, the concentration of impurity supplied to the fuel cell was verified by gas chromatography (GC).

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.991-996
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• 1995

Effects of high hydrostatic pressure on microorganisms and browning enzymes in Angelica keiskei juice were investigated using response surface methodology. The optimum process condition for maximum reduction of total aerobes was $5700\;kg_f/cm^2$ (558.6 MPa) pressure and 7.16 min process time, and 3.44 log cycle reduction of total aerobes was predicted at the optimum condition. E. coli, initially $8.8{\times}10^3\;CFU/ml$, was completely inactivated by high hydrostatic pressure at all process conditions ($3800{\sim}6700\;kg_f/cm^2\;pressure;\;3{\sim}17\;min\;process\;time$). Polyphenol oxidase and peroxidase were partly inactivated by the high hydrostatic pressure. It was also indicated that inactivation of microorganisms and browning enzymes by hydrostatic pressure is dependent on pressure rather than process time.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.4
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• pp.362-372
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• 2000

The causal message logging is a low-cost technique of building a distributed system that can tolerate process crash failures. Previous research in causal message logging protocol assumes that the number of processes in a fault-tolerant system is fixed. This assumption makes all processes modify their data structures when a new process is added or an existing process terminates. However, the proposed approach in this paper allows to each process retain identifiers of only the communicating processes instead of all processes. This mechanism enables the fault-tolerant system to operate at many different scales. Using this mechanism, we develop a new algorithm that can be adapted for recovery in existing causal message logging protocols. Our recovery algorithm is 1) a distributed technique which does not require recovery leader, 2) a nonblocking protocol which does not force live processes to block while recovery is in progress, and 3) a novel mechanism which can tolerate failures of an arbitrary number of processes. Earlier causal message logging protocols lack one or more of the above properties.

• Journal of Convergence for Information Technology
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• v.10 no.11
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• pp.177-184
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• 2020

The objective of this study was to investigate the effect of cold-pressed flaxseed oil through the roasting temperature (unroasted and roasted at 150℃ and 200℃) and time (10 and 20 min) on the chemical changes. Cold-pressed flaxseed oil extraction yield was calculated with respect to the roasted process and total phenolic content, fatty acid composition, and volatile compound were analyzed. The extraction yield was increased in the roasted oil compared to the unroasted oil. Total phenolic content was significantly higher in oil from the roasted at 150℃ for 20 min compared to other roasting condition. Fatty acid composition was not affected by the extraction process. The content of aldehyde, ketone, furan, and pyrazine was higher than in the roasted at 200℃ compared to the unroasted and roasted at 150℃. These findings suggest that cold-pressed flaxseed oil extracted from the roasted at 150℃ for 20 min may be considered acceptable for safe extraction process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.6
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• pp.100-107
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• 2021

As a significant technology in the smartization era promoted by the Fourth Industrial Revolution, the secondary battery industry has recently attracted significant attention. The demand for lithium-ion batteries (LIBs), which exhibit excellent performance, is considerably increasing in different industrial fields. During the manufacturing process of LIBs, it is necessary to join the cathode and anode sheets with thicknesses of several tens of micrometers to lead taps of the cathode and anode with thicknesses of several hundreds of micrometers. Ultrasonic welding exhibits excellent bonding when bonded with very thin plates, such as negative and positive electrodes of LIBs, and dissimilar and highly conductive materials. In addition, ultrasonic welding has a small heat-affected zone. In LIBs, Cu is mainly used as the negative electrode sheet, whereas Cu or Ni is used as the negative electrode tab. In this study, one or two electrode sheets (t0.025 mm Cu) were welded to one lead tab (t0.1 mm Cu). The welding energy and pressure were used as welding parameters to determine the welding strength of the interface between two or three welded materials. Finally, the effects of these welding parameters on the welding strength were investigated.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.107-117
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• 2019

Because shipbuilding is single-product production with limited resources, production management technology is essential to manage the resources effectively and maximize the productivity of ship-process. Therefore, many shipbuilding companies are conducting research on ship production plan and process considering various constraints in the field by applying modeling and simulation. However, it is difficult to provide accurate production plan on sudden schedule and process changes, and to understand the interconnectivity between the processes that produce blocks in existing research. In addition, there are many differences between the production planning and field planning because detailed processes and quantity of blocks can not be considered. In this research, we propose the integrated process-based modeling method considering process-operation sequences, BOM(Bill of materials) and resource constraints of all the scheduled blocks in the indoor system. Through the integrated process-based model, it is easy for the user to grasp the assembly relationship, workspace and preliminary relationship of assembly process between the blocks in indoor system. Also, it is possible to obtain the overall production plan that maximizes resource efficiency without the separate simulation and resource modeling procedures because resource balancing that considers the amount of resource quantity shared in the indoor system is carried out.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.279-284
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• 2005

We investigated the impedance matching characteristics of UHF-band RFID tag antenna and tag chip for increased reading range. A voltage multiplier designed using 0.4 $\mu$m zero-$V_T$ MOSFET showed that DC output voltage of about 2 V can be obtained using standard CMOS process. The input impedance of the voltage multiplier was examined to achieve impedance matching to the RFID tag antenna using analytical and numerical approaches. The input impedance of the voltage multiplier could be varied in a wide range by selecting the size of MOSFET and the number of multiplying stages, and thus can be impedance matched to a tag antenna in presence of other tag circuit blocks. A meander line inductively-coupled RFID tag antenna operating at UHF band also shows the feasibility of impedance matching to tile RFID tag chip.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.386-394
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• 2012

Recent trends in the flexible manufacturing systems are morphing cell control for the shop-wide production operation system and providing the integrated operation and execution system together with vendor-specific FMC/FMS platform. In these requirements, the shop-floor level operation system plays a role of coordinating the control activity of each cell, and has to provide flexibility for the complexity of mixed operations of various cells. This paper suggests a system architecture for the mixed environments of multi-cells and job shop, its corresponding enabling technologies based on comparative studies with other related studies and commercialized systems. This approach includes a process definition model considering the integration with upper BOM-BOP and external service modules, and reconfigurable device-level interface which provides dynamic interconnections with machine tools and cell controllers. The function modules and their implementation results are also described to provide the feasibility of the proposed approaches as the flexible shop-floor operation system for the multi-cell environments.

• IE interfaces
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• v.10 no.1
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• pp.209-222
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• 1997

The paper provides a methodology to obtain the automaticity indicator of a factory and the sequence of enabling technologies of factory automation. The automaticity indicator is the measure of the current automation status of a factory and can be used as a crucial criteria for the future automation schedule and investment. Although most industries have their own computation methods which usually consider the number of workers in the shop floor, this research covers five evaluation items of automation, such as, production facility, material transfer system, inspection and test system, information system, and flexibility. The detailed evaluation models are developed for each item. Automation sequencing prioritizes the enabling technologies of factory automation on the basis of several criteria which consist of two phases. The first phase includes the automation indicator and the second phase includes six sub-criteria such as production rate, quality, number of workers, capital investment, development duration, development difficulty. For this evaluation, AHP(Analytical Hierarchy Process) is introduced to prevent the decision maker's subject intention. As results of the automaticity indicator and automation sequence, the manager can save time and cost in building constructive and transparent automation plans.