• Journal of the Korean Magnetics Society
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• v.6 no.1
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• pp.36-39
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• 1996

We have constructed a disp1acerrent sensor for measuring dynamic magnetostriction of an arrvrphous ribbon under alternating magnetic field using fiber optic Fabry-Perot interferorreter. The signal of the sensor was depen¬dent on the index matching oil and the optical isolator. The resolution of the sensor was $30{\AA}$ and the measured peak to peak magnetostriction of the amorphous ribbon $Fe_{81}B_{13.5}Si_{3.5}C_{2}$ was $28{\times}10^{-6}$.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.250-256
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• 2002

Resistivity tomography has become an important tool to image underground resistivity distribution. This method has been widely applied to site investigation for engineering and environmental purpose. In resistivity tomography, various electrode arrays can be used and each array has both merits and demerits. For example, the pole-pole array has high signal to noise ratio (S/N ratio), but its resolution is too low. The dipole-dipole array has low S/N ratio, but its resolution is very high. The Pole-dipole may has intermediate Snf ratio and resolution. The modified Pole-dipole array, recently proposed, shows reasonable S/N ratio and resolution, which are comparable to the pole-dipole array. These electrode arrays except the pole-pole array, however, have the problem that the apparent resistivity can diverge at some special electrode Positions. Also, the Pole-Pole array may not reflect the doe resistivity of an anomalous body. In this study, we propose a new electrode array, mixed array, where pole-dipole and modified pole-dipole ways are selectively used with the relative positions of current and potential electrodes. The mixed array has the same level of S/N ratio and resolution as the pole-dipole array and the apparent resistivity does not diverge in the receiver hole. Furthermore, the apparent resistivity using the array can reflect the true resistivity of the anomalous body.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.2
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• pp.152-158
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• 2022

The purpose of this study is to investigate experimentally the compressive strength and tensile behavior of cement composites reinforced by selvedge short fiber from high performance fabric. Four types of mixtures according to the types of selvedge short fibers were prepared and compressive strength and tension tests were performed. Test results showed that the compressive strength values of composites investigated in this study ranged from 64 MPa to 66 MPa and all composites showed strain-hardening behavior. The tensile strain capacity values of composites ranged from 2.6 % to 2.8 % and multiple cracking behavior was observed in all composites.

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.87-94
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• 2004

The effects of pretreatment of GAC and dissolved oxygen (DO) on the sorption capacity for ο-cresol were investigated using pretreated GAC under oxic and anoxic conditions. Virgin GAC was used with pretreated GACs by $O_2$, acid and base as sorbents. Sorption capacity of GAC was dependent on the oxygen conditions according to the pretreatment methods. Virgin GAC showed increased sorption capacity when DO was present in the solution, while $O_2$-pretreated GAC did not show any considerable capacity change. Acid- and base-pretreated GACs were relatively more influenced by presence of DO as compared with virgin GAC. Both acid and base-pretreated GACs showed a rapid sorption rate at the initial stage, but as contact time became longer the sorption was slower. Sorbed ο-cresol was extracted with micro-Soxhlet extraction apparatus using the GAC separated from the rate experiments. Within 1 hour both acid and base-pretreated GACs showed the decrease in extraction efficiencies under both oxic and anoxic conditions. After 1 hour such a trend (the increase as contact time was longer) was not observed and showed relatively constant efficiencies of 35∼50%. According to the results of this study $O_2$contacted with GAC before sorption as well as DO present in the solution during sorption could influence the GAC sorption capacity.

• The Korean Journal of Applied Statistics
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• v.20 no.1
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• pp.133-145
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• 2007

Local linear estimator has a number of advantages over the traditional kernel estimators. The better performance near boundaries is one of them. However, local linear estimator can produce erratic result in sparse regions in the realization of the design and to solve this problem much research has been done. Local linear quasi-likelihood estimator has many common properties with local linear estimator, and it turns out that sparse design can also lead local linear quasi-likelihood estimator to erratic behavior in practice. Several methods to solve this problem are proposed and their finite sample properties are compared by the simulation study.

• Geophysics and Geophysical Exploration
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• v.4 no.3
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• pp.59-69
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• 2001

Five kinds of modified electrode arrays were proposed to overcome the weak points of the commonly used arrays using dipole and/or pole in two-dimensional resistivity surveys. The modified pole-pole array was suggested to overcome the inefficiency caused by distant earthing in pole-pole array. Four kinds of modified arrays using dipole were designed to enhance the signal-to-noise ratio of the conventional dipole-dipole and pole-dipole arrays through boosting up the measured potential difference. In the numerical experiments using the two-dimensional modeling and inversion, the effects of the ambient electrical noise and the resolving power were examined and the results showed the validity of the modified arrays proposed in this study.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.200-207
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• 2021

The purpose of this study is to investigate experimentally the effects of type of superplasticizer on tensile behavior and cracking pattern of alkali-activated slag-based cementless composite. Three mixtures were prepared according to type of superplasticizer, and the compressive strength and tension tests were performed. Test results showed that differences of tensile strength, tensile strain capacity, and toughness of composites were up to 28.1%, 39.1%, and 66.2%, respectively, according to type of superplasticizer, although fiber balling or poor dispersion of fibers in fresh composites was not observed. It was also observed that the type of superplasticizer influenced number of cracks and maximum fiber bridging stress.

• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.109-116
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• 2016

The market share of high-speed railway vehicles is increasing across the world. A high-performance impact energy absorption factor is essential to satisfy the safety standards of railway vehicles. A deformed tube assembly is a typical energy absorption factor in railway vehicles. The tube assembly comprises a deformed tube and a press-fitting punch, its performance depends on the absorption energy characteristics in the plastic zone of the tube. In this study, a deformed tube assembly of a railway vehicle is designed that can absorb a maximum impact energy of 200kJ under plastic deformation. Slab method and finite element analysis are used to estimate the reaction force of the punch in the initial stage, the performance of the designed tube assembly is confirmed experimentally.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.205-211
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• 2006

The objective of this study was to evaluate the durability of low shrinkage high performance concrete(LSHPC), which was combined with expansive additives and shrinkage reducing admixtures. We tested for not only LSHPC but also high performance concrete(HPC) and normal concrete(NC) to be compared with the durability of LSHPC. HPC was made in the same water-binder ratio of LSHPC without expansive additives and shrinkage reducing admixture. As a result, it was found that LSHPC had higher compressive and tensile strength than that of HPC. LSHPC showed more excellent performance than HPC and NC in the case of resistance to chloride ion penetration and resistance to carbonation and also showed nearly 100 durability factor in the freeze-thawing test with 500 cycles. From the examination about the watertightness and the pore distribution, it was found that the durability of LSHPC was improved because its hardened cement paste is organized closer. So we can conclude that when LSHPC is applied to structures in field, it is possible to reduce the shrinkage and crack in concrete and improve the durability.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.12
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• pp.1793-1798
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• 2015

Antioxidant activities of various solvent extracts from Coriolus versicolor were investigated for their total polyphenol content, total flavonoid content, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical scavenging activity. C. versicolor extracts were produced by organic solvents such as ethanol, ethyl acetate, and methanol. Total polyphenol and flavonoid contents in the ethanol and ethyl acetate extracts were higher than those in the methanol extract. DPPH radical scavenging activity of methanol extract showed the highest value of 80.3%, which was similar to that of ascorbic acid (85.5%). All extracts showed good (>90.0%) ABTS cation radical scavenging activity. The antimicrobial activities of these extracts from C. versicolor were evaluated against six strains of bacteria using the disc diffusion method. All extracts showed antimicrobial activities against all tested bacteria except Staphylococcus aureus. These results indicate that various extracts from C. versicolor could be useful as natural antioxidant and antimicrobial agents.