• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.442-454
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• 2021

The porous transport layer (PTL) is essential to effectively remove oxygen and hydrogen gas from the electrode surface at high current density operation conditions. In this study, the effect of PTL with different characteristics such as pore size, pore gradient, interfacial coating was investigated by multi-layered sintered mesh. A water electrolysis single cell of active area of the 34.56 cm² was constructed, and IV performance and impedance analysis were conducted in the range of 0 to 2.0 A/cm². It was confirmed that the multi-layered sintered mesh PTL, which have an average pore size of 25 to 57 ㎛ and a larger pore gradient, removed bubbles effectively and thus seemed to improve IV performance. Also, it was confirmed that the catalytic metals such as Ni, NiMo coating on the PTL reduced activation overpotential, but increased mass transport overpotential.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.165-173
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• 1994

Purpose : Metastatic cancer to the brain is a major problem for the patients with bronchogenic carcinoma, and most of these patients have a limited survival expectancy. To increase tumor control and / or to decrease late morbidity with possible shortening in over-all treatment period, multiple daily fraction technique for brain metastasis was performed. The author reperesented the results of accelerated fractionation radiotherapy in patients with brain metastases from non-small cell lung cancer. Materals and Methods : Twenty-six patients with brain metastases from non-small cell lung cancer between 1991 and 1993 received brain radiotherapy with a total dose of 48 Gy, at 2 Gy per fraction, twice a day with a interfractional period of 6 hours, and delivered 5 days a week. The whole brain was treated to 40 Gy and boost dose escalated to 8 Gy for single metastatic lesion by reduced field. Twenty-four of the 26 patients completed the radiotherapy. Radiotherapy was interupted in two patients suggesting progressive intracerebral diseases. Results : This radiotherapy regimen appears to be comparable to the conventional scheme in relief from symptoms. Three of the 24 patients experienced nausea and or vomiting during the course of treatment because of acute irradiation toxicity. The author observed no excessive toxicity with escalating dose of irradiation. An increment in median survival, although not statistically significant(p>0.05), was noted with escalating doses(48 Gy) of accelerated fractionation(7 months) compared to conventional treatment(4.5 months). Median survival also increased in patients with brain solitary metastasis(9 months) compared to multiple extrathoracic sites(4 months), and in patients with good performance status(9 months versus 3.5 months), they were statistically significant (p<0.01). Conclusion : The increment in survival in patients with good prognostic factors such as controlled primary lesion, metastasis in brain only and good perfomance status appeared encouraging. Based on these results, a multi-institutional prospective randomized trial should be initiated to compare the twice-a-day and once-a-day radiotherapy schemes on patients with brain metastasis with careful consideration for the patients' quality of life.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.6
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• pp.346-361
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• 2013

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2012. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. The conclusions are as follows : (1) The research works on thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and valves, fuel cells and power plants, ground-coupled heat pumps, and general heat and mass transfer systems. Research issues are mainly focused on new and renewable energy systems, such as fuel cells, ocean thermal energy conversion power plants, and ground-coupled heat pump systems. (2) Research works on the heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, and industrial heat exchangers. Researches on heat transfer characteristics included the results for natural convection in a square enclosure with two hot circular cylinders, non-uniform grooved tube considering tube expansion, single-tube annular baffle system, broadcasting LED light with ion wind generator, mechanical property and microstructure of SA213 P92 boiler pipe steel, and flat plate using multiple tripping wires. In the area of pool boiling and condensing heat transfer, researches on the design of a micro-channel heat exchanger for a heat pump, numerical simulation of a heat pump evaporator considering the pressure drop in the distributor and capillary tubes, critical heat flux on a thermoexcel-E enhanced surface, and the performance of a fin-and-tube condenser with non-uniform air distribution and different tube types were actively carried out. In the area of industrial heat exchangers, researches on a plate heat exchanger type dehumidifier, fin-tube heat exchanger, an electric circuit transient analogy model in a vertical closed loop ground heat exchanger, heat transfer characteristics of a double skin window for plant factory, a regenerative heat exchanger depending on its porous structure, and various types of plate heat exchangers were performed. (3) In the field of refrigeration, various studies were executed to improve refrigeration system performance, and to evaluate the applicability of alternative refrigerants and new components. Various topics were presented in the area of refrigeration cycle. Research issues mainly focused on the enhancement of the system performance. In the alternative refrigerant area, studies on CO2, R32/R152a mixture, and R1234yf were performed. Studies on the design and performance analysis of various compressors and evaporator were executed. (4) In building mechanical system research fields, twenty-nine studies were conducted to achieve effective design of mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, renewable energy systems, and lighting systems in buildings. New designs and performance tests using numerical methods and experiments provide useful information and key data, which can improve the energy efficiency of buildings. (5) In the fields of the architectural environment, studies for various purposes, such as indoor environment, building energy, and renewable energy were performed. In particular, building energy-related researches and renewable energy systems have been mainly studied, reflecting interests in global climate change, and efforts to reduce building energy consumption by government and architectural specialists. In addition, many researches have been conducted regarding indoor environments.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.288-294
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• 2007

The LSCF cathode far Solid Oxide Fuel Cell was investigated to develop high performance unit cell at intermediate temperature by modified oxalate method with different electrolytes and different pH. The LSCF powders employed La, Sr, Co and Fe oxides, oxalic acid, ethanol and $NH_4OH$ solution were synthesized with pH controlled as 2, 6, 7, 8, 9 and 10 at $80^{\circ}C$ Single crystalline phase was obtained from pH $2{\sim}9$. on the other hand, $La_2O_3$ appeared from pH 10. Very fine powder with particle size of 50 nm was obtained at calcination temperature of $800^{\circ}C$ for 4 hours. LSCF cathode synthesized at pH 7 showed the highest electric conductivity in the temperature range of $600^{\circ}C$ to $900^{\circ}C$ its value was 950 S/cm at $900^{\circ}C$ Under same synthesis conditions, polarization resistance of each LSCF cathode was changed with different calcination temperatures. As-prepared powder presented 2.52, 1.54 and $2.58\;{\Omega}$ at $600^{\circ}C$ with ScSZ, 8Y-YSZ and GDC as its electrolyte respectively after calcination at $800^{\circ}C$ for 4 hours.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.14-20
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• 2018

Electric vehicles are environmentally friendly because they emit no exhaust gas, unlike gasoline automobiles. However, since they are driven by the electric power from batteries, the distance they can travel based on a single charge depends on their energy density. Therefore, the lithium-ion battery having a high energy density is a good candidate for the batteries of electric vehicles. Since the electrode is an essential component that governs their efficiency, the electrode manufacturing process plays a vital role in the entire production process of lithium-ion batteries. In particular, the coating process is a critical step in the manufacturing of the electrode, which has a significant influence on its performance. In this paper, we propose an innovative process for improving the efficiency and productivity of the coating process in electrode manufacturing and describe the equipment design method and development results. Specifically, we propose a design procedure and development method in order to improve the core plate coating quality by 25%, using a technology capable of reducing the assembly margin due to its high output/high capacity and improving the product capacity quality and assembly process yield. Using this method, the battery life of the lithium-ion battery cell was improved. Compared with the existing coating process, the target loading level is maintained and dispersed to maintain the anode capacity (${\pm}0.4{\rightarrow}{\pm}0.3mg/cm^2r$ reduction).

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.21-27
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• 2016

Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.1
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• pp.63-70
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• 2018

Objective: The aim of the study was to isolate gossypol-degrading bacteria and to assess its potential for gossypol degradation. Methods: Rumen liquid was collected from fistulated cows grazing the experimental pasture. Approximately 1 mL of the rumen liquid was spread onto basal medium plates containing 2 g/L gossypol as the only source of carbon and was then cultured at $39^{\circ}C$ to isolate gossypol-degrading bacteria. The isolated colonies were cultured for 6 h and then their size and shape observed by microscope and scanning electron microscope. The 16S rRNA gene of isolated colonies was sequenced and aligned using National Center for Biotechnology Information-Basic Local Alignment Search Tool. The various fermentation conditions, initial pH, incubation temperature, inoculum level and fermentationperiod were analyzed in cottonseed meal (CSM). The crude protein (CP), total gossypol (TG), and free gossypol (FG) were determined in CSM after fermentation with isolated strain at $39^{\circ}C$ for 72 h. Results: Screening results showed that a single bacterial isolate, named Rumen Bacillus Subtilis (RBS), could use gossypol as a carbon source. The bacterium was identified by 16S rDNA sequencing as being 98% homologous to the sequence of Bacillus subtilis strain GH38. The optimum fermentation conditions were found to be 72 h, $39^{\circ}C$, pH 6.5, moisture 50%, inoculum level $10^7cell/g$. In the optimum fermentation conditions, the FG and TG content in fermented CSM decreased 78.86% and 49% relative to the control. The content of CP and the essential amino acids of the fermented CSM increased respectively, compared with the control. Conclusion: The isolation of a gossypol-degrading bacterium from the cow rumen is of great importance for gossypol biodegradation and may be a valuable potential source for gossypol-degradation of CSM.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.3
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• pp.156-162
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• 2007

The parallel beam SPECT system acquires projection data by using collimators in conjunction with photon detectors. The projection data of the parallel beam SPECT system is, however, blurred by the point response function of the collimator that is used to define the range of directions where photons can be detected. By increasing the number of parallel holes per unit area in collimator, one can reduce such blurring effect. This approach also, however, has the blurring problem if the distance between the object and the collimator becomes large. In this paper we consider correction methods for artifacts caused by non-circular orbit of parallel beam SPECT with many parallel holes per detector cell. To do so, we model the relationship between the object and its projection data as a linear system, and propose an iterative reconstruction method including artifacts correction. We compute the projector and the backprojector, which are required in iterative method, as a sum of convolutions with distance-dependent point response functions instead of matrix form, where those functions are analytically computed from a single function. By doing so, we dramatically reduce the computation time and memory required for the generation of the projector and the backprojector. We conducted several simulation studies to compare the performance of the proposed method with that of conventional Fourier method. The result shows that the proposed method outperforms Fourier methods objectively and subjectively.

• Journal of Microbiology and Biotechnology
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• v.27 no.2
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• pp.321-334
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• 2017

Process surveillance within agricultural biogas plants (BGPs) was concurrently studied by high-throughput 16S rRNA gene amplicon sequencing and an optimized quantitative microscopic fingerprinting (QMF) technique. In contrast to 16S rRNA gene amplicons, digitalized microscopy is a rapid and cost-effective method that facilitates enumeration and morphological differentiation of the most significant groups of methanogens regarding their shape and characteristic autofluorescent factor 420. Moreover, the fluorescence signal mirrors cell vitality. In this study, four different BGPs were investigated. The results indicated stable process performance in the mesophilic BGPs and in the thermophilic reactor. Bacterial subcommunity characterization revealed significant differences between the four BGPs. Most remarkably, the genera Defluviitoga and Halocella dominated the thermophilic bacterial subcommunity, whereas members of another taxon, Syntrophaceticus, were found to be abundant in the mesophilic BGP. The domain Archaea was dominated by the genus Methanoculleus in all four BGPs, followed by Methanosaeta in BGP1 and BGP3. In contrast, Methanothermobacter members were highly abundant in the thermophilic BGP4. Furthermore, a high consistency between the sequencing approach and the QMF method was shown, especially for the thermophilic BGP. The differences elucidated that using this biphasic approach for mesophilic BGPs provided novel insights regarding disaggregated single cells of Methanosarcina and Methanosaeta species. Both dominated the archaeal subcommunity and replaced coccoid Methanoculleus members belonging to the same group of Methanomicrobiales that have been frequently observed in similar BGPs. This work demonstrates that combining QMF and 16S rRNA gene amplicon sequencing is a complementary strategy to describe archaeal community structures within biogas processes.

• KSBB Journal
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• v.21 no.2
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• pp.133-139
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• 2006

In 'solid-phase' PEGylation, the conjugation reaction occurs as the proteins are attached to a solid matrix, and thus it can have distinct advantages over the conventional, solution-phase process. We report a case study: rhIFN-${\alpha}$-2a was first adsorbed to cation exchange resin and then N-terminally PEGylated by aldehyde mPEG of 5, 10, and 20 kD through reductive alkylation. After the PEGylation, salt gradient elution efficiently recovered the mono-PEGylate in a purified form from the unwanted species such as unmodified IFN, unreacted PEG, and others. The mono-PEGylation and its purification were integrated in a single chromatographic step. Depending on the molecular weight of the mPEG aldehyde used, the mono-PEGylation yield ranged 50-64%. We could overcome the major problems of random, or uncontrollable, multi-PEGylation and the post-PEGylation purification difficulties associated with the solution-phase process. N-terminal sequencing and MALDI-TOF MS confirmed that a PEG molecule was conjugated only to the N-terminus. Compared with the unmodified IFN, the mono-PEGylate showed the reduced anti-viral activity as measured by the cell proliferation assay. The bioactivity was reduced more as the higher molecular weight PEG was conjugated. Immunoreactivity, evaluated indirectly by antibody binding activity using a surface plasmon resonance biosensor, also decreased. Nevertheless, trypsin resistance as well as thermal stability was considerably improved.