• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.6-10
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• 2021

The shorting resistance (SR) of the PEMFC(Proton Exchange Membrane Fuel Cell) polymer membrane is an important indicator of the durability of the membrane. When SR decreases, shorting current (SC) increases, reducing durability and performance. When SR becomes less than about 0.1 kΩ·㎠, shorting occurs, the temperature rises rapidly, and MEA(Membrane Electrode Assembly) is burned to end stack operation. In order to prevent shorting, we need to control the SR, so the conditions affecting the SR were studied. There were differences in the SR measurement methods, and the SR measurement method, which improved the DOE(Department of Energy) and NEDO(New Energy and Industrial Technology Development Organization) method, was presented. It was confirmed that the SR decreases as the relative humidity, temperature and cell compression pressure increase. In the final stage of the accelerated durability evaluation process of the polymer membrane, SR rapidly decreased to less than 0.1 kΩ·㎠, and the hydrogen permeability became higher than 15 mA/㎠. After dismantling the MEA, SEM(Scanning Electron Microscope) analysis showed that a lot of platinum was distributed inside the membrane.

• PNF and Movement
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• v.18 no.1
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• pp.127-132
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• 2020

Purpose: This study aimed to investigate the impact of resistance on the muscle activities of the long and short heads of the biceps brachii, according to the elbow angle in supination, and the difference in muscle activity between the long and the short heads. Methods: This study was conducted with 22 men in their 20s who voluntarily agreed to participate. With the glenohumeral joint neutral in a position of supination, the elbow angle was randomly moved to 0°, 30°, 60°, and 90°. Using an 8-channel surface EMG while the participants held a 2-kg. dumbbell, the muscle activities of the long and the short heads of the biceps brachii were measured. The measured data were statistically processed using SPSS for Windows 12.0. For the activities of the short and the long heads according to the angle, a one-way ANOVA was conducted, and subsequently, to check the results of an analysis of the difference between groups, an LSD post-hoc test was conducted. An independent t-test was used to compare the activities of the long head and the short head according to the angles. Results: The analysis of the impact of the load of the dumbbell at each elbow angle on the muscle activities of the long and short heads of the biceps brachii revealed significant differences in both heads (p < 0.05). The result of the post-hoc analysis showed significant differences in both heads at angles between 0° and 30°, between 0° and 60°, and between 0° and 90°. Analysis of the impact of the load of the dumbbell in supination on the muscle activities of the long and short heads showed a significant difference at the angle between 0° and 30° (p < 0.05). Conclusion: The long head of the biceps brachii mainly acts in supination; however, in supination at elbow-bending angles of 60° and 90°, there was no difference in muscle activity between the short head and the long head.

• Structural Engineering and Mechanics
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• v.73 no.5
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• pp.543-554
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• 2020

This paper aims to investigate the seismic performance of RC short columns and long columns with welding stirrups. Through the low-cyclic horizontal loading test of specimens, the seismic performance indexes such as failure modes, hysteretic curve, skeleton curve, ductility, energy dissipation capacity, stiffness degradation and strength degradation were emphatically analyzed. Furthermore, the effects of shear span ratio, stirrups ratio and axial compression ratio on the performance of specimens were studied. The results showed that the seismic performance of the RC short columns with welding stirrups were basically the same as that of the RC short columns with traditional stirrups, but the seismic performance of RC long columns with welding stirrups was better than that of RC long columns with traditional stirrups. The seismic performance of RC short columns and long columns with welding stirrups could be improved by increasing stirrup ratio and shear span ratio and reducing axial pressure ratio. Moreover, the welding stirrup have the advantages of steel saving, industrialization and standardization production, convenient construction, and reducing time, which indicated that the welding stirrups could be applied in practical engineering.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.89-90
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• 2013

Higher power density, higher operational temperature, lower on state resistance and higher switching frequency capabilities of Silicon Carbide (SiC) technology devices compared to Silicon (Si) devices makes it has higher promising market. One of the most developed SiC devices is the power MOSFET. This study tests the SiC MOSFET under short circuit conditions taking into account the effect of gate voltage characteristics. The results will be compared to IGBT and MOSFET Si devices with similar ratings. A tester circuit was designed to perform the short circuit operation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1001-1010
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• 1999

Thermo-mechanical behavior of discontinuous shape memory alloy(SMA) reinforced polymeric composite has been studied using modified shear lag theory and finite element(FE) analysis with 2-D multi-fiber model. The aligned and staggered models of short-fiber arrangement are employed. The effects of fiber overlap and aspect ratio on the thermomechanical responses such as the thermal expansion coefficient are investigated. It is found that the increase of both tensile stress(resistance stress) in SMA fiber and compressive stress in polymer matrix with increasing aspect ratio is the main cause of low thermal deformation of the composite.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.2
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• pp.85-92
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• 2000

30 kVA rotating-field type Super-Conducting Generator is built and tested with intensive FE(Finite Element) analysis. The generator is driven by VVVF inverter-fed induction motor. Open Circuit Characteristic(OCC) and Short Circuit Characteristic(SCC) are presented in this paper. Also, the test result under the light load(up to 3.6 kW) are given. From the design stage, 2-D FE analysis coupled with the external circuit has been performed. The external circuit includes the end winding resistance and reactance as well as two dampers. When compared with the test data, the FE analysis results show a very good agreement.

• Tribology and Lubricants
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• v.10 no.3
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• pp.39-46
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• 1994

In order to investigate the effect of the ceramic reinforcements on the wear properties of aluminum bronze composites, Cu-8wt%Al aluminum bronze alloys reinforced with the Saffil alumina short fiber were produced by the powder metallurgical method and tested by a pin-ondisc wear testing machine. The wear surfaces of the pin specimens and discs, wear debris, and the cross sections of the wear specimens were observed by SEM. The wear mechanism according to various wear conditions and the change of microstructure in the composites were also discussed. In the results, the reinforcement of the composites with alumina short fiber was very effective at the higher applied load over 10N. The material transportation to the counter disc was observed in the alloy specimens without reinforcements. However, the composites reinforced with ceramic particles and fibers showed the resistance against the material transportation.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.175-178
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• 2006

We present a ring hybrid balun with additional two ${\lambda}/4$ short stubs that offers excellent amplitude and phase balance performance. The phase difference which is essentially occurred in $180^{\circ}$ ring hybrid is compensated by a ${\lambda}/4$ short stub in one output port. To compensate the amplitude imbalance inherent in the ring hybrid, the series resistance will be added to the second stub which is connected to another output port. The measured balun shows that phase imbalance is less than $2.5^{\circ}$ and magnitude imbalance is less than 0.2dB over a 1.75-2.25 GHz.

• Journal of Microbiology and Biotechnology
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• v.33 no.7
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• pp.849-856
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• 2023

Short-chain fatty acids (SCFAs), such as butyrate, propionate, and acetate produced by the gut microbiota have been implicated in physiological responses (defense mechanisms, immune responses, and cell metabolism) in the human body. In several types of cancers, SCFAs, especially butyrate, suppress tumor growth and cancer cell metastasis via the regulation of the cell cycle, autophagy, cancer-related signaling pathways, and cancer cell metabolism. In addition, combination treatment with SCFAs and anticancer drugs exhibits synergistic effects, increasing anticancer treatment efficiency and attenuating anticancer drug resistance. Therefore, in this review, we point out the importance of SCFAs and the mechanisms underlying their effects in cancer treatment and suggest using SCFA-producing microbes and SCFAs to increase therapeutic efficacy in several types of cancers.

• Research in Plant Disease
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• v.21 no.1
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• pp.20-23
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• 2015

A sequential planting method was developed to screen rice plants with durable resistance against rice blast in a short time, and applied for several years in Korean rice breeding program. In this study, we showed the advantages of a sequential planting method compared to other pathogenicity tests. The correlation analysis among three pathogenicity tests and other factors demonstrated that durable resistance depended on the average of diseased leaf area and the number of compatible pathogens. Significant correlations were found in the nursery test but not in the field test result. In addition, we traced changes in the pathogen population during sequential planting stages through re-isolation of the pathogen. The portion of compatible pathogens was increased during sequential planting. Through this study, we provide an effective sequential planting method and direction of durable resistance in a breeding program.