• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.384-389
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• 2009

KEPRI (Korea Electric Power Research Institute) has studied planar type solid oxide fuel cell (SOFC) stacks using anode-supported cells and kW class co-generation systems for residential power generation. In this work, a 1 kW SOFC system consisted of a hot box part, a cold BOP (balance of plant) part, and a hot water reservoir. The hot box part contained a SOFC stack made up of 48 cells, a fuel reformer, a catalytic combustor, and heat exchangers. Thermal management and insulation system were especially designed for self-sustainable operation in that system. A cold BOP part was composed of blowers, pumps, a water trap, and system control units. When the 1 kW SOFC stack was tested using hydrogen at $750^{\circ}C$, the stack power was about $1.2\;kW_e$ at 30 A and $1.6\;kW_e$ at 50 A. Turning off an electric furnace, the SOFC system was operated using hydrogen and city gas without any external heat source. Under self-sustainable operation conditions, the stack power was about $1.3\;kW_e$ with hydrogen and $1.2\;kW_e$ with city gas respectively. The system also recuperated heat of about $1.1\;kW_{th}$ by making hot water.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.187-207
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• 1999

The thermal distributions near the growth interface of 150mm CZ crystals were measured by three thermocouples installed at the center, middle (half radius) and edge (10m from surface) of the crystals. The results show that larger growth rates produced smaller thermal gradients. This contradicts the widely used heat flux balance equation. Using this fact, it si confirmed in CZ crystals that the type of point defects created is determined by the value of the thermal gradient (G) near the interface during growth, as already reported for FZ crystals. Although depending on the growth systems the effective lengths of the thermal gradient for defect generation are varied, were defined the effective length as 10mm from the interface in this experiment. If the G is roughly smaller than 20C/cm, vacancy rich CZ crystals are produced. If G is larger than 25C/cm, the species of point defects changes dramatically from vacancies to interstitial. The experimental results which FZ and CZ crystals are detached from the melt show that growth interfaces are filled with vacancy. We propose that large G produces shrunk lattice spacing and in order to relax such lattice excess interstitial are necessary. Such interstitial recombine with vacancies which were generated at the growth interface, next occupy interstitial sites and residuals aggregate themselves to make stacking faults and dislocation loops during cooling. The shape of the growth interface is also determined by the distributions of G across the interface. That is, the small G and the large G in the center induce concave and convex interfaces to the melt, respectively.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.4
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• pp.145-151
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• 2011

Evapotranspiration (ET) is an important process acrossa wide range of disciplines, including ecology, hydrology and meteorology.In this study, daily actual evapotranspiration (ETa) is based energy balance equation and considering high surface roughness length to estimate. This study was used variety of satellite data and ground observation data in Korea Peninsula from 1 January to 31 December 2009. In this study, sensible heat flux is one of the important parameters of ETa. Measurements of sensible heat flux are, however, complex and can't be easily obtained. So this study was used an empirical coefficient B to simplify estimate of sensible heat flux. The coefficient B in the ETa model requires a careful definition of aerodynamic resistance. So this study proposed ETa model considering aerodynamic resistance and high surface roughness length. This study was conducted validation in comparison of the proposed daily ETa results with Priestley-Taylor ETp.

• Journal of the Korean Society for Heat Treatment
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• v.10 no.2
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• pp.109-120
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• 1997

Microstructure and mechanical properties of Fe-Si-Mn-P high strength steel sheet have been investigated by controlling the cooling rate. Bainite and ferrite were obtatined by annealing in the ferrite pluse austenite region, and ferrite and austenite were obtatined after annealing in the fully austenite region. Ferrite and pearlite were obtained when the cooling rate was controlled from the annealing temperature above $760^{\circ}C$ and bainite showed with increasing cooling rate, however below $760^{\circ}C$ ferrite and bainite were obtained. Tensile strengths and hardness nearly unchanged with increasing cooling rate after control the cooling rate from the temperature above $760^{\circ}C$, while tensile strengths increased and elongation decreased with increasing cooling rate when the cooling rate was controlled from the tempeature below $760^{\circ}C$. Without regard to annealing temperature, tensile strength increased and elongation decreased with increasing cooling rate. Tensile strengths and elongation values heat treated in the ferrite plus austenite region were higher than those in the fully austenite region. Retained austenite and strength-elongation balance showed the maximum value at $780^{\circ}C$ and decreased with increasing annealing temperature. Strength-elongation balance value was controlled by the retained austenite.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.1
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• pp.15-19
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• 1988

Heat energy distribution forming net radiation above corn canopy was determined by means of the Bowen ratio-energy balance method. Total-global solar radiation above crop canopy during the growing season was $1,559MJm^{-2}$ and total latent heat flux density was $960MJm^{-2}$. The data showed that 61.6% of the global solar radiation was used for a heat source of evapotranspiration (ETa) above corn canopy. Mean daily ETa ranged from 2.7 to 5.6mm. Total ETa, total drymatter, and water use efficiency were 394mm, $2,214gm^{-2}$, and $5.6gm^{-2}mm^{-1}$, respectivively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.5
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• pp.259-268
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• 2017

This paper proposes a hydrogen-based social economy derived from fuel cells capable of replacing fossil fuels and resolving global warming, It thus provides an entry for developing economically feasible social configurations to make use of bio-hydrogen production systems. Bio-hydrogen production works from the principle that microorganisms decompose water in the process of converting CO to $CO_2$, thereby producing hydrogen. This study parts from an analysis of an existing 157-ton class NA1 bio-hydrogen reactor that identifies the state of feedstock and reactor conditions. Based on this analysis, we designed a 1-ton class bio-hydrogen reactor process simulator. We carried out thermal analyses of biological heat reactions, sensible heat, and heat radiation in order to calculate the thermal load of each system element. The reactor temperature changes were determined by modeling the feed mixing tank capacity, heat exchange, and heat storage tank. An analysis was carried out to confirm the condition of the feed mixing tank, heat exchanger, heat storage tank capacity as well as the operating conditions of the system so as to maintain the target reactor temperature.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.81.2-81.2
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• 2010

고체 산화물 연료전지(SOFC) 시스템은 스택과 기계적 주변 장치인 MBOP(Mechanical Balance of Plant), 그리고 전기적 주변장치인 EBOP(Electrical Balance of Plant)로 구성되어있다. SOFC는 일반적으로 $700^{\circ}C$ 이상의 고온에서 작동되기 때문에 효율적인 열 이용 및 열 관리가 중요하다. SOFC 시스템의 MBOP에는 상온의 연료가스들을 고온으로 가열하여 스택에 유입 시기키 위한 열교환기 및 촉매연소기 등의 장치들이 필요하며, 효율적인 열관리를 위해서는 고온에서 작동하는 장치들을 한곳에 통합하여 구성하는 것이 필수적이다. 본 연구에서는 SOFC 시스템의 MBOP(Mechanical Balance of Pant) 중 고온부에 해당하는 촉매연소기, 열교환기 및 스택이 통합된 스택 모듈을 제작에 앞서 개념 검증을 위해 열교환기 및 촉매연소기로 이루어진 프로토타입(prototype)의 SOFC 모듈평가 장치를 제작하였다. 열교환기는 Plate형으로 총 6개로 구성되어 있으며, 연료극과 공기극 가스라인에 각각 3개씩 배치하여 스택에 유입되는 연료 및 공기가 촉매연소기에서 나오는 고온의 배가스와 열교환되어 가열되도록 구성하였다. 촉매연소기는 honeycomb 타입의 촉매를 사용하였고, 촉매연소기로 유입되는 연료극 배가스와 공기의 균일혼합과 hot spot을 방지하기 위한 장치를 삽입하여 제작하였다. 제작된 SOFC 모듈평가장치는 시운전을 통해 각 장치의 성능 확인 후 반응면적이 $20{\times}20cm^2$ 인 단전지를 적층하여 연계 운전을 수행하였다.

• Mycobiology
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• v.38 no.4
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• pp.302-309
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• 2010

Formic acid is a representative carboxylic acid that inhibits bacterial cell growth, and thus it is generally considered to constitute an obstacle to the reuse of renewable biomass. In this study, Saccharomyces cerevisiae was used to elucidate changes in protein levels in response to formic acid. Fifty-seven differentially expressed proteins in response to formic acid toxicity in S. cerevisiae were identified by 1D-PAGE and nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS/MS) analyses. Among the 28 proteins increased in expression, four were involved in the MAP kinase signal transduction pathway and one in the oxidative stress-induced pathway. A dramatic increase was observed in the number of ion transporters related to maintenance of acid-base balance. Regarding the 29 proteins decreased in expression, they were found to participate in transcription during cell division. Heat shock protein 70, glutathione reductase, and cytochrome c oxidase were measured by LC-MS/MS analysis. Taken together, the inhibitory action of formic acid on S. cerevisiae cells might disrupt the acidbase balance across the cell membrane and generate oxidative stress, leading to repressed cell division and death. S. cerevisiae also induced expression of ion transporters, which may be required to maintain the acid-base balance when yeast cells are exposed to high concentrations of formic acid in growth medium.

• Agricultural and Biosystems Engineering
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• v.1 no.2
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• pp.73-80
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• 2000

Aerodynamics in a naturally ventilated multi-span greenhouse with plants was analyzed numerically by the computational fluid dynamics (CFD) simulation. To investigate the potential application of CFD techniques to greenhouse design and analysis, the numerical results of the CFD model were compared with the results of a steady-state mass and energy balance numerical model. Assuming the results of the mass and energy balance model as the standard, reasonably good agreement was obtained between the natural ventilation rates computed by the CFD numerical model and the mass and energy balance model. The steady-state CFD model during a sunny day showed negative errors as high as 15% in the morning and comparable positive errors in the afternoon. Such errors assumed to be due to heat storage in the floor, benches, and greenhouse structure. For a west wind of 2.5 m s$^{-1}$ , the internal nonporous shading screens that opened to the east were predicted to have a 15.6% better air exchange rate than opened to the west. It was generally predicted that the presence of nonporous internal shading screens significantly reduced natural ventilation if the horizontal opening of the screen for each span was smaller that the effective roof vent opening.

• Journal of Biomedical Engineering Research
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• v.18 no.1
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• pp.37-44
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• 1997

In this paper, the power spectral analysis of heart rate variability(HRV) was performed to evaluate effects of orthostatic stress with head-up tiIt on autonomic nervous system(ANS) for 25 healthy male subjects(age : 24 $\pm$ 5 yr.) and a new method was proposed to assess the autonomic balance. The ECG and respiration signals were recorded at tiIt angles of $0^{\circ}$, $45^{\circ}$, $90^{\circ}$and $0^{\circ}$ successively for 10 minutes per each stage under the condition of frequency controlled respiration(0.25Hz). Heat rate(HR) gradually increased ils the angle increased Similarly, according to the increment of angle, normalized low frequency component(0.05-0.15Hz) gradually increased, whereas normalized high frequency component (0.20-0.30Hz) was reduce4 From these results it is speculated that orthostatic stress head-up tiLt, results in the prevalence of sympathetic tone in autonomic balance with the increment of sympathetic tone and the decrement of parasympathetic tone, which seems to meanthat autonomic nervous system plays a major role in compensating for disturbances of cardiovascular system due to it.