• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.556-566
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• 2019

Recently, as the supply of residential polymer electrolyte membrane fuel cells (PEMFCs) increases, the durability and lifetime of the PEMFC system are becoming important. The related studies have been mainly focused on the durability and lifetime of materials while the research on the durability and maintenance of the system level is insufficient. In this paper, a model-based fault detection method is developed considering an air supply system that is dominant to the system performance and efficiency. A commercial 1 kW residential fuel cell system is built, and experiments are conducted under various operation loads and states (normal, 6 faults). From the experimental data, nominal models and residuals are generated. With the residual pattern obtained from real-time data, the detection and classification of various faults can be possible. The technical importance of this paper is to minimize extra sensor installation by using the empirical model rather than a complex mathematical model, and to decrease the number of models by using the applicable model at three loads. Finally, the model-based fault detection method for the air supply system of a PEMFC is established and is expected to be applicable to other subsystems.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.293-296
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• 2004

The objective of this study was to decide the designing factor for remediaton of the contaminated site. The soil and ground-water samples were analyzed and hydro- geological characteristics was assayed for the survey of pollution level. Also air-permeability test and MPN(most probable number) test were conducted for selecting the designing factor. The contaminants were mainly found in north-west part of the site and were expected to move toward the south. Ex-situ technology was expected more useful than in-situ one with the results of air-permeability test saying that air permeability was relatively low. Additional microbes were expected for remediation efficiency because residual microbes were loosely populated. The choosing of the designing factor was requisite for remediation of contaminated site.

• Journal of Institute of Convergence Technology
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• v.3 no.1
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• pp.9-14
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• 2013

Recently, the development of renewable energy sources in Mongolia has been needed due to climate change and air pollution in Ulaanbaatar as rapid economic growth. Biodiesel can be considered as an alternative fuel for petroleum based diesel in order to decrease air pollution in Ulaanbaatar because of its no emission of particle materials from internal combustion engine in automobile. Rapeseed oil having low cloud point and pour point was suggested as a promising raw material for biodiesel production in Mongolia. Considering high population density and severe air pollution by particle materials and SOx in Ulaanbaatar, prior supplying site of biodiesel in Mongolia was the capital region including Ulaanbaatar. In the production of biodiesel in Mongolia, adsorption process was a effective alternative to washing process for the removal of residual alkali catalyst and reactants due to long winter time in Mongolia. For the stable supply of biodiesel, subsidy and no tax policy is needed in the early stage of biodiesel supply in Mongolia.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.185-192
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• 2002

A laboratory scale thermogravimetric analyser was developed to investigate the combustion characteristics of selected solid fuel(wood) in the highly preheated air. The aims are to introduce in the means of experimental determination of the solid fuel particle characteristics through the combustion process in the environment of highly preheated air. A nearly single particle combustion condition was reproduced in a thermogravimetric analyser and regenerating combustor. For a fuel particle whose characteristic length was a few centimeter, the sub-processes of fuel drying, pyrolysis as well as the combustion of residual carbon were identified. Fluidized environment of carrier gas was selected as the major parameter which affect the combustion process.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.5
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• pp.316-325
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• 2010

Harmonic analyses are carried out in order to obtain the major frequency components of the air temperature (AT) and surface water temperature (SWT) data monitored in the Middle Area of the Yellow Sea (Yellow Sea monitoring buoy). The analysis shows the annual and semi-annual components are predominant and the higher frequency components are relatively weak with contribution to the short fluctuations, i.e. below $0.2{\sim}0.5^{\circ}C$, in the AT and SWT. The standard deviation of the AT residual is 2.4 times larger than that of the SWT residual and the occurrence frequency distributions of the AT and SWT residual components are both closely fitted to a normal-distribution function. The variation pattern on the AT-SWT plane forms the clear continuous hysteresis loop in anti-clockwise direction which is composed of the AT-SWT rising period, AT-SWT falling period, and the constant SWT period in winter season.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.15 no.2
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• pp.49-54
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• 2009

The effects of filling temperatures of broth and degassing method on the residual oxygen content and gas composition in the pouch and physical strength of packaging material for Samgyetang depending on the contamination of broth on the sealing layer and sterilization process were investigated. The residual oxygen content in the broth and the oxygen proportion in the headspace of package were decreased with the increase of broth temperature at filling into the pouch from 50 to 100. When the products were packaged as air-contained (Air), manually squeezed the upper side of package out to minimize the headspace (Degas) and flushed with nitrogen gas ($N_2$-Flushing) while maintaining the broth temperatures of Samgyetang at 50 or 85. The residual oxygen content and oxygen proportion were increased in the order of $N_2$-Flushing

• The KSFM Journal of Fluid Machinery
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• v.19 no.2
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• pp.49-54
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• 2016

A conceptual study of an air-cooled heat exchanger is conducted to achieve the long-term passive cooling of an integral reactor. A newly designed air-cooled heat exchanger is introduced in the present study and preliminary thermal sizing is demonstrated. This study mainly focuses on feasibility of an innovative air-cooled heat exchanger to extend the cooling period of the passive residual heat removal system(PRHRS) only in passive manners. A vertical shell-and-tube air-cooled heat exchanger is installed at the top of the emergency cooldown tank(ECT) to collect evaporated steam into condensate, which enables water inventory of the ECT to be kept. Finally, thermal sizing of an air-cooled heat exchanger is presented. The length and the number of tubes required, and also the height of a stack are calculated to remove the designated heat duty. The present study will contribute to an enhancement of the passive safety system of an integral reactor.

• Geomechanics and Engineering
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• v.20 no.5
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• pp.411-420
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• 2020

Numbers fitting-curve equations have been proposed to predict soil-water retention curve (SWRC) whose parameters have no definitude physical meaning. And these methods with precondition of measuring SWRC data is time-consuming. A simplified directly method to estimate SWRC without parameters obtained by fitting-curve is proposed. Firstly, the total SWRC can be discretized into linear segments respectively. Every segment can be represented by linear formulation and every turning point can be determined by the pore-size distribution (PSD) of Mercury Intrusion Porosimetry (MIP) tests. The pore diameters governing the air-entry condition (AEC) and residual condition (RC) can be determined by the PSDs of MIP test. The PSD changes significantly during drying in SWR test, so the determination of AEC and RC should use the PSD under corresponding suction conditions. Every parameter in proposed equations can be determined directly by PSD without curve-fitting procedure and has definitude physical meaning. The proposed equations give a good estimation of both unimodal and bimodal SWRCs.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.236-241
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• 2017

Electrohydraulic forming is a high-speed forming process that deforms a blank using electric discharge in liquid. When high voltage is discharged in the water, a shock wave is propagated from the tip of the electrodes to the blank, causing the blank to be deformed into the die. Electrohydraulic forming has many advantages including improved formability and reduced bouncing effect and springback. The objective of this paper was to conduct a feasibility study to identify the electrohydraulic effect. An electrohydraulic forming apparatus was developed and experiments were carried out. The results of the experiment showed that the developed apparatus had sufficient energy to deform the blank into the die. Using the hole to emit residual air in the die was more effective than using the vacuum pump in terms of saving on experiment time.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.457-464
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• 2006

Controlled auto ignition (CAI) combustion, also known as HCCI (homogeneous charge compression ignition), offers the potential to simultaneously improve fuel economy and reduce emission. CAI-combustion was achieved in a single cylinder gasoline DI engine, with a cylinder running in a CAI mode. Standard components were used the camshafts which had been modified in order to restrict the gas exchange process. The effects of air-fuel ratio, residual EGR rate and injection timing such as early injection and late injection on the attainable CAI combustion region were investigated. The effect that injection timings on factor such as start of combustion, combustion duration and heat release rate was also investigated. From results early injection caused the mixture to ignite earlier and burn more quickly due to the exothermic reaction during the recompression and gave rise to good mixing of the fuel-air.