• Computers and Concrete
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• 제20권5호
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• pp.545-553
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• 2017

A pounding tuned mass damper (PTMD) can be considered as a passive device, which combines the merits of a traditional tuned mass damper (TMD) and a collision damper. A recent analytical study by the authors demonstrated that the PTMD base on the energy dissipation during impact is able to achieve better control effectiveness over the traditional TMD. In this paper, a PTMD prototype is manufactured and applied for seismic response reduction to examine its efficacy. A series of shaking table tests is conducted in a three-story building frame model under single-dimensional and two-dimensional broadband earthquake excitations with different excitation intensities. The ability of the PTMD to reduce the structural responses is experimentally investigated. The results show that the traditional TMD is sensitive to input excitations, while the PTMD mostly has improved control performance over the TMD to remarkably reduce both the peak and root-mean-square (RMS) structural responses under single-dimensional earthquake excitation. Unlike the TMD, the PTMD is found to have the merit of maintaining a stable performance when subjected to different earthquake loadings. In addition, it is also indicated that the performance of the PTMD can be enhanced by adjusting the initial gap value, and the control effectiveness improves with the increasing excitation intensity. Under two-dimensional earthquake inputs, the PTMD controls remain outperform the TMD controls; however, the oscillation of the added mass is observed during the test, which may induce torsional vibration modes of the structure, and hence, result in poor control performance especially after a strong earthquake period.

• Journal of Radiation Protection and Research
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• 제41권4호
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• pp.378-383
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• 2016

Background: Radiation dose rates in PRIDE facility is evaluated quantitatively for assessing radiation safety of workers because of large amounts of depleted uranium being handled in PRIDE facility. Even if direct radiation from depleted uranium is very low and will not expose a worker to significant amounts of external radiation. Materials and Methods: ORIGEN-ARP code was used for calculating the neutron and gamma source term being generated from depleted uranium (DU), and the MCNP5 code was used for calculating the neutron and gamma fluxes and dose rates. Results and Discussion: The neutron and gamma fluxes and dose rates due to DU on spherical surface of 30 cm radius were calculated with the variation of DU mass and density. In this calculation, an imaginary case in which DU density is zero was added to check the self-shielding effect of DU. In this case, the DU sphere was modeled as a point. In case of DU mixed with molten salt of 50-250 g, the neutron and gamma fluxes were calculated respectively. It was found that the molten salt contents in DU had little effect on the neutron and the gamma fluxes. The neutron and the gamma fluxes, under the respective conditions of 1 and 5 kg mass of DU, and 5 and $19.1g{\cdot}cm^{-3}$ density of DU, were calculated with the molten salt (LiCl+KCl) of 50 g fixed, and compared with the source term. As the results, similar tendency was found in neutron and gamma fluxes with the variation of DU mass and density when compared with source spectra, except their magnitudes. Conclusion: In the case of the DU mass over 5 kg, the dose rate was shown to be higher than the environmental dose rate. From these results, it is concluded that if a worker would do an experiment with DU having over 5 kg of mass, the worker should be careful in order not to be exposed to the radiation.

• 한국식품과학회지
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• 제29권1호
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• pp.51-56
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• 1997

겨자의 항균성 및 식품보존제로의 이용가능성을 조사하기 위하여 겨자의 첨가에 따른 냉면육수의 보존 중 그 효과를 조사하고, 대장균의 형태변화를 현미경으로 관찰한 결과는 다음과 같다. 겨자를 첨가시킨 냉면육수의 적정산도는 처음에 겨자 무첨가 육수에 비하여 높았으나 24시간 보존 후에는 겨자 무첨가 육수보다 낮게 나타났으며, 겨자 첨가 냉면육수의 생균수 및 대장균수는 처음에 겨자 무첨가시보다 감소하였으며, 겨자 첨가농도가 높을수록 감소하는 폭이 크게 나타났고, VBN 함량은 보존기간이 지남에 따라 증가하였고, 겨자가 첨가된 냉면육수가 겨자 무첨가보다 낮게 나타났으며, 겨자첨가 농도가 높을수록 더욱 낮게 나타났다. 겨자 물추출물로 처리한 대장균을 전자현미경으로 관찰한 결과 균체표면이 수축되고 표층구조가 허물어져 심한 형태학적 변화를 나타내었다.

• 한국미생물·생명공학회지
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• 제48권3호
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• pp.316-321
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• 2020

송이버섯이 첨가된 전통주를 제조한 후 송절편을 첨가하여 첨가량과 숙성 기간에 따른 향기 성분의 변화를 기체 크로마토그래피 질량분광법을 통해 조사하였다. 송절편을 첨가하지 않은 대조구에서는 총 3종의 향기 성분이 검출되었으나, 송절편을 첨가한 송이주에서는 총 15종의 향기 성분이 검출되었다. 송절편을 5% 첨가한 실험구에서 송이버섯 특유의 향기 성분인 β-fenchyl alcohol과 2-octanol, methyl cinnamate은 숙성기간 동안 상대적인 함량이 증가하여 8주 후에는 각각 67.57%, 2.14%와 0.94%를 나타냈다. 주성분 분석 결과 송절편 첨가에 의한 β-fenchyl alcohol의 상대적 함량 증가가 송이주의 향미 특성에 영향을 미치며, 송이주의 향미 특성은 송절편의 첨가량 보다 숙성 기간에 의해 더 큰 영향을 받는 것으로 판단된다.

• 산업식품공학
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• 제13권4호
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• pp.275-281
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• 2009

참기름은 높은 항산화활성 및 항암작용 등의 우수한 영양학적 가치를 지니는 반면 비싼 가격으로 인하여 가짜 참기름의 유통이 범람하여 이를 판별할 수 있는 분석 방법의 확립이 요구되는 실정이다. 따라서 본 연구에서는 질량분석기를 바탕으로 한 전자코를 이용하여 대두유가 혼합된 참기름을 제조하여 진위 판별을 시도하기위하여 각각의 유지를 전자코를 이용하여 분석, 통계처리하였다. 혼합 참기름의 휘발성 향기성분으로부터 생성되는 ion fragment 중 40-160 amu에서 각 시료 간에 차별성이 높은 fragment (m/z)를 선택하여 해당 intensity값을 판별 분석한 결과, 참기름 및 대두유는 뚜렷하게 구분되었다. 참기름 및 대두유, 옥수수유, 들기름을 각각의 순수한 상태로 향기성분 분석을 한 결과 서로 다른 위치에서 정확하게 분리됨을 알 수 있었고, 대두유와 옥수수유의 경우 타 기름과는 달리 순수한 공기 성분과 비슷한 위치에서 확인되는 것으로 휘발성향기성분의 감응도가 상대적으로 낮은 것으로 판단된다. 미량의 대두유가 혼합된 참기름은 첨가된 대두유의 농도에 비례하여 제1판별함수값(DF1)과 높은 상관관계를 나타내었다. 참향후 참기름의 위조 여부를 검증하는 방법에 하나로 활용될 수 있을 것이다.

• Smart Structures and Systems
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• 제15권2호
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• pp.335-353
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• 2015

Previous long-term measurements of the Uldolmok tidal current power plant showed that the structure's natural frequencies fluctuate with a constant cycle-i.e., twice a day with changes in tidal height and tidal current velocity. This study aims to improve structural health monitoring (SHM) techniques for offshore structures under a harsh tidal environment like the Uldolmok Strait. In this study, lab-scale experiments on a simplified offshore structure as a lab-scale test structure were conducted in a circulating water channel to thoroughly investigate the causes of fluctuation of the natural frequencies and to validate the displacement estimation method using multimetric data fusion. To this end, the numerical study was additionally carried out on the simplified offshore structure with damage scenarios, and the corresponding change in the natural frequency was analyzed to support the experimental results. In conclusion, (1) the damage that occurred at the foundation resulted in a more significant change in natural frequencies compared with the effect of added mass; moreover, the structural system became nonlinear when the damage was severe; (2) the proposed damage index was able to indicate an approximate level of damage and the nonlinearity of the lab-scale test structure; (3) displacement estimation using data fusion was valid compared with the reference displacement using the vision-based method.

• Journal of Microbiology and Biotechnology
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• 제30권3호
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• pp.404-416
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• 2020

Bacteria that are resistant to high temperatures and alkaline environments are essential for the biological repair of damaged concrete. Alkaliphilic and halotolerant Bacillus sp. AK13 was isolated from the rhizosphere of Miscanthus sacchariflorus. Unlike other tested Bacillus species, the AK13 strain grows at pH 13 and withstands 11% (w/v) NaCl. Growth of the AK13 strain at elevated pH without urea promoted calcium carbonate (CaCO₃) formation. Irregular vaterite-like CaCO₃ minerals that were tightly attached to cells were observed using field-emission scanning electron microscopy. Energy-dispersive X-ray spectrometry, confocal laser scanning microscopy, and X-ray diffraction analyses confirmed the presence of CaCO₃ around the cell. Isotope ration mass spectrometry analysis confirmed that the majority of CO₃^2- ions in the CaCO₃ were produced by cellular respiration rather than being derived from atmospheric carbon dioxide. The minerals produced from calcium acetate-added growth medium formed smaller crystals than those formed in calcium lactate-added medium. Strain AK13 appears to heal cracks on mortar specimens when applied as a pelletized spore powder. Alkaliphilic Bacillus sp. AK13 is a promising candidate for self-healing agents in concrete.

• 한국해양공학회지
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• 제28권4호
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• pp.261-267
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• 2014

Because a change in the natural frequencies of a structure indicates structural health problems, monitoring the natural frequencies crucial. Long-term measurement for the Uldolmok tidal current power plant structure has shown that its natural frequencies fluctuate with a constant cycle twice a day. In this study, lab-scale tests to investigate the causes of these natural frequency fluctuations were carried out in a circulating water channel. Three independent variables in the tests that could affect the fluctuation of the natural frequencies were the water level, current velocity, and boundary condition between the specimen and the bottom of the circulating water channel. The experimental results were verified with numerical ones using ABAQUS. It was found that the fluctuation of the natural frequencies was governed by a decrease in stiffness due to the boundary condition much more than the effect of added mass. In addition, it was found that the natural frequency would decrease with an increase in the tidal current velocity because of its nonlinearity when the boundary condition was severely deteriorated due to damage.

• 한국염색가공학회지
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• 제21권5호
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• pp.51-57
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• 2009

Since heavy metal pollution is a significant global environmental problem and very dangerous to human health, the improved methods for detecting heavy metals are required recently. Colorimetric chemosensors are now considered as one of the most effective analytical method used in the environment monitoring. New direct dyes having the function of colorimetric chemosensors were synthesized. When metal ions such as $Al^{3+}$, $Ca^{2+}$, $Cd^{2+}$, $Cr^{3+}$, $Cu^{2+}$, $Fe^{2+}$, $Fe^{3+}$, $Hg^{2+}$, $Li^+$, $Mg^{2+}$, $Na^+$, $Ni^{2+}$, $Pb^{2+}$ and $Zn^{2+}$ were added each solution of new direct dyes, the color of solution was changed and can be easily detected with naked eyes without expensive experimental equipment such as atomic absorption spectrometer (AAS) or inductively coupled plasma?mass spectrometer (ICP-MS). The new benzidine analogues were diazotized and reacted with couplers such as H-acid, J-acid, Chromotropic acid, Nevill-winther acid and gamma acid to synthesize new direct dyes. The structures of the new direct dyes were confirmed by high resolution mass spectrometer (FAB ionization) and evaluated with UV-Vis spectroscopy. The UV-VIS spectroscopy was measured for the dye solutions by adding various concentrations of metal ions. It was observed that the absorbance in UV-Vis spectra was changed as the heavy metal ions were added.

• Ocean Systems Engineering
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• 제3권3호
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• pp.219-236
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• 2013

The accurate prediction of motion in waves of a marine vehicle is essential to assess the maximum sea state vs. operational requirements. This is particularly true for small crafts, such as Autonomous Surface Vessels (ASV). Two different numerical methods to predict motions of a SWATH-ASV are considered: an inviscid strip theory initially developed at MIT for catamarans and then adapted for SWATHs and new a hybrid strip theory, based on the numerical solution of the radiation forces by an unsteady viscous, non-linear free surface flow solver. Motion predictions obtained by the viscous flow method are critically discussed against those obtained by potential flow strip theory. Effects of viscosity are analyzed by comparison of sectional added mass and damping calculated at different frequencies and for different sections, RAOs and motions response in irregular waves at zero speed. Some relevant conclusions can be drawn from this study: influence of viscosity is definitely non negligible for SWATH vessels like the one presented: amplitude of the pitch and heave motions predicted at the resonance frequency differ of 20% respectively and 50%; in this respect, the hybrid method with fully non-linear, viscous free surface calculation of the radiation forces turns out to be a very valuable tool to improve the accuracy of traditional strip theories, without the burden of long computational times requested by fully viscous time domain three dimensional simulations.