• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.53-57
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• 2008

Friction welding was performed to investigate mechanical properties for Ni-base superalloy with 15 mm diameter solid bar. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, impact energy test, Vickers hardness surveys of the bond of area and heat affected zone. And then, the nondestructive technique to evaluate the weld quality was carried out by acoustic emission(AE) and ultrasonic attenuation coefficient. The tensile strength of the friction welded joint was shown up to 90 % of the Alloy718 base metal under the condition of the heating time over 5 sec. The optimal welding conditions were n=2,000 rpm, $P_1=200$ MPa, $P_2=200$ MPa, $t_1=8$ sec and $t_2=5$ sec when the total upset length was 4.4 mm.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.267-271
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• 2000

The influence of photoexcited nonequilibrium carriers on domain switching and photovoltaic current was investigated in two kinds of poled La-modified PbTiO$_3$ferroelectric ceramics, (Pb$_{0.85}$La$_{0.15}$)TiO$_3$and (Pb$_{0.76}$La$_{0.24}$)TiO$_3$, under illumination in the absence of external electric field. Both photovoltaic current and cumulative AE event counts increased with illumination time. The observed nonsteady-state photovoltaic current could be explained on the basis of the cycles of a series of physical events consisting the establishment of space charge field by photoexcited carriers trapped at the grain boundaries, the photoinduced domain switching, and the increase in the remanent polarization. An analysis of energy distribution of the observed AE signals also revealed that the space charge field in (Pb$_{0.85}$La$_{0.15}$)TiO$_3$allowed both 18$0^{\circ}C$ and 90$^{\circ}$domains to be switched during illumination.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.619-630
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• 2014

Two butanol-based Condensation Particle Counters (CPC 3022, CPC 3025), three water-based CPCs (CPC3781, CPC3785${\times}$2), a Gardner Counter, a Fast Mobility Particle Sizer (FMPS), and an Aerosol Electrometer (AE) were deployed to measure the number concentrations from atomized aerosol under six different conditions. Comparisons of particle number concentrations measured by the CPCs, FMPS, and AE were conducted to evaluate the performance of the each CPCs using laboratory generated artificial particles such as NaCl, succinic acid ($C_4H_6O_4$), and particles generated by propane torch & heat gun in the chamber. Good correlation between the CPC3025 and FMPS was observed for the total particle number concentrations in the size range 15 nm to 90 nm. In addition, this paper suggests that photometric mode in water-based CPC3785 could not be used as quantitative of number concentrations for CPC3785.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.107-116
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• 1999

The damage in concrete structures generally starts with microcracking and thus it is important to find and explore these microcracks in concrete in order to ensure appropriate safety and serviceability. The purpose of the present study is to identify the damage characteristics of concrete structures due to cracking by employing the acoustic emission techniques. A comprehensive experimental study has been done. The cracking damage under tensile and flexural loadings have been identified and the bond damage between steel and concrete have been also characterized. It is seen that the amplitudes and energy level of Acoustic Emission(AE) events are found to be relatively small for bond cracking damages and large for tensile cracking damages. The characteristic equations of the AE events for various cracking damages have been proposed based on the present test data. The internal microcracks are progressively developed ahead of a visible actual crack and the present study clearly exhibits these damage mechanism for various types of cracking in concrete. The present study provides useful data which can be used to identify the various types of cracking damages in concrete structures. This will allow efficient maintenance of concrete structures through monitoring of internal cracking based on acoustic emission.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.166-173
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• 2014

In this study, a laminated composite material with dispersing aluminum oxide powder between the CFRP laminate plies, and also CFRP composites without aluminium oxide powder were fabricated for Mode I experiments using the DCB specimen and a tensile test. The behavior of the crack and the change of the interfacial fracture toughness were evaluated. Also in order to evaluate the damage mechanism for the crack extension, the AE sensor on the surface of the DCB test specimen was attached. AE amplitude was estimated for CFRP-alumina and CFRP composite. And the fracture toughness was evaluated by the stress intensity factor and energy release rate. The results showed that an unstable crack was propagated rapidly in CFRP composite specimen along with the interface, but crack propagation in CFRP-alumina specimen was relatively stable. From results, we show that aluminium oxide powder spreaded uniformly in the interface of the CFRP laminate carried out the role for preventing the sudden crack growth.

• Exercise Science
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• v.21 no.2
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• pp.183-190
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• 2012

This study is to evaluate the availability of cardiorespiratory fitness measurement by 20 m shuttle run test based upon energy contribution rates of elite athletes in different sports type. Sixty-seven elite athletes attending K national university participated in this study. They were divided by three groups based upon sports type, composed of Anaerobic Group (sprint, jumps, weightlifting, throw; n=35), Aerobic Group (medium-long distance; n=9), and Combat Sport Group (judo; n=23). 20 m shuttle run test was conducted by Leger et al.(1982) method and calculating acceleration using measured shuttle run repetitions was conducted by Brewer et al.(1988) method. To test the usefulness of VO₂max, graded exercise treadmill test was conducted and standing long jump and 50 m run were measured as power fitness factors. Z-jump was used for measuring power, agility, and muscular endurance. Standing long jump and 50 m run of Anaerobic Group (AnG) was significantly higher than that of Aerobic Group (AeG) and Combat Sport Group (CG) (p<0.05). However, Z-jump of CG was significantly higher than that of AnG and AeG(p<.05). There was a higher correlation of 20 m shuttle run test and VO₂max in AnG(r= 0.577, p<.0001) and CG(r= 0.760, p<.0001). Otherwise, there was a low correlation of 20 m shuttle run test and VO₂max in AeG. There was no significant group difference to test the availability of 20 m shuttle run test and there was a reduced error when converting 20 m shuttle run results into VO₂max. This study examined the usefulness of 20 m shuttle run test by converting 20 m shuttle run repetition results into VO₂max calculation, which showed reduced error. Therefore, this study confirmed that it would be needed to convert 20 m shuttle run results into VO₂max for universal and practical use in the field without dividing sports type.

• Journal of Ginseng Research
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• v.22 no.4
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• pp.252-259
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• 1998

Electron beam, electrically produced from an electron accelerator, was compared with gamma energy in terms of its influence on color and organoleptic qualities of ginseng powders when exposed to the energy used for their microbial decontamination. Hunter color L and b values were suitable for measuring color characteristics of ginseng powders, which were not significantly changed by the exposure to 5 to 7.5 kGy electron beam and gamma energy. Fifty percent ethanol extracts of irradiated ginseng powders at 10 key showed negligible differences from the non-irradiated control in the pattern of absorption spectra at 280∼800 am, but showed increased values in overall color difference (AE) as compared with powdered samples. Irradiation more than 10 kGy and storage at ambient temperature for 4 months caused browning of powdered samples. Irradiation at more than 10 kGy of electron beam was found a critical level to bring about appreciable changes (p<0.05) in or-ganoleptic qualities such as color and odor of sterilized samples, and red ginseng powder was more susceptible than white one to organoleptic changes by irradiation.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1487-1496
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• 2013

In this paper, a novel algorithm for PD localization in power transformers based on wavelet de-noising technique and energy criterion is proposed. Partial discharge is one of the main failures in power transformers. The localization of which could be very useful for maintenance systems. Acoustic signals due to a PD event are transient, irregular and non-repetitive. So wavelet transform is an efficient tool for this signal processing problem that gives a time-frequency demonstration. First, different wavelet based de-noising methods are analyzed. Then, a reasonable structure for threshold value determining and applying manner on signals is presented. Evaluated errors are good evidences for choices. Next, applying the elimination low energy frequency bands is discussed and developed as a de-noising method. Time differences between signals are used for PD localization. Different ways in time arrival detection are introduced and a novel approach in energy criterion method is presented. At the end, the quality of algorithm is verified through the different assays in lab.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.261-263
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• 2007

본 연구는 광전자 촉매시스템을 이용해 $TiO_{2}$ 졸이 코팅된 구형 비드의 광분해 효율에 대해 고찰한 것이다. $TiO_{2}$ 졸이 코팅된 구형 비드인 알루미늄비드, 유리비드, 실리카비드 화이트젤 ($1{\cdot}2{\cdot}3$형) 다섯 가지 비드를 사용하였고 실험은 산화환원지시 약인 메틸렌블루 수용액이 광촉매의 산화환원반웅을 통해 색상 및 홉광도 변화를 통해 환원 청도를 고찰할 목적으로 실행되었다. 소재별 실험 결과, 실험에 사용한 소재 중 실리카비드 화이트첼($1{\cdot}2{\cdot}3$형)만이 반응성을 나타냈다. 이들 $1{\cdot}2{\cdot}3$형은 $TiO_{2}$의 함량을 달리한 비드들이며 1형이 가장 적은 함량을 가지며 3형이 가장 많은 함량을 가지고 있다. 실험 결과 3형이 반응성이 가장 좋은 것을 알 수 있으며, 이 실험에서는 코팅물의 함량과 고정물의 상태가 광촉매 반응에 영향을 주는 것을 알 수 있다.

• Nutrition Research and Practice
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• v.5 no.6
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• pp.527-532
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• 2011

ESR1 has been listed in the Human Obesity Gene Map as candidate gene associated with obesity. Thus, in this study, we investigated the effect of the ESR1 rs1884051 polymorphism on obesity-related variables, together with their modulations by dietary intake in Korean men. The obesity-related variables and dietary intake of 3,039 Korean men aged 40-59 years from KoGES database were analyzed. Body weight (P = 0.007), BMI (P = 0.003), waist-hip ratio (= 0.011), fat body mass (P = 0.010), and body fat percentage (P = 0.040) were significantly lower in subjects with the minor T allele of ESR1 rs1884051 than in subjects carrying the C allele. Moreover, the rs1884051 T allele was associated with a decreased risk of obesity prevalence (P = 0.040). Among the subjects whose total energy intake was below the median, carrier of the minor T allele of ESR1 rs1884051 had a lower BMI (P = 0.003) when compared with subjects carrying the C allele. In addition, among subjects whose plant protein intake was above the median, carrier of the minor T allele of ESR1 rs1884051 had a lower BMI (P = 0.044) compared with subjects carrying the C allele. Our findings demonstrate that there is a significant association between the ESR1 rs1884051 variant and obesity-related variables and this association can be potentially modified by dietary energy and plant protein intake.