• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1197-1210
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• 2018

Since the first detection of gravitational-wave (GW), GW150914, September 14th 2015, the multi-messenger astronomy added a new way of observing the Universe together with electromagnetic (EM) waves and neutrinos. After two years, GW together with its EM counterpart from binary neutron stars, GW170817 and GRB170817A, has been observed. The detection of GWs opened a new window of astronomy/astrophysics and will be an important messenger to understand the Universe. In this article, we briefly review the gravitational-wave and the astrophysical sources and introduce the basic principle of the laser interferometer as a gravitational-wave detector and its noise sources to understand how the gravitational-waves are detected in the laser interferometer. Finally, we summarize the search algorithms currently used in the gravitational-wave observatories and the detector characterization algorithms used to suppress noises and to monitor data quality in order to improve the reach of the astrophysical searches.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1794-1798
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• 2018

We have grown famatinite $Cu_3SbS_4$ films by using sulfurization of Cu/Sb stack film. Sulfurization at $500^{\circ}C$ produced famatinite $Cu_3SbS_4$ phase, while $400^{\circ}C$ and $450^{\circ}C$ sulfurization exhibited unreacted and mixed phases. The fabricated $Cu_3SbS_4$ film showed S-deficiency, and secondary phase of $Cu_{12}Sb_4S_{13}$. The secondary phase was confirmed by X-ray diffraction, Raman spectroscopy, photoluminescence and external quantum efficiency measurements. We have also fabricated solar cell in substrate type structure, ITO/ZnO/(Zn,Sn)O/$Cu_3SbS_4$/Mo/glass, where $Cu_3SbS_4$ was used as a absorber layer and (Zn,Sn)O was employed as a Cd-free buffer. Our best cell showed power conversion efficiency of 0.198%. Characterization results of $Cu_3SbS_4$ absorber indicates deep defect (due to S-deficiency) and low shunt resistance (due to $Cu_{12}Sb_4S_{13}$ phase). Thus in order to improve the cell efficiency, it is required to grow high quality $Cu_3SbS_4$ film with no S-deficiency and no secondary phase.

• Geomechanics and Engineering
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• v.13 no.3
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• pp.371-384
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• 2017

Physical and mechanical properties of rocks are of interest in many fields, including materials science, petrophysics, geophysics and geotechnical engineering. Uniaxial compressive strength UCS is one of the key mechanical properties, while density and porosity are important physical parameters for the characterization of rocks. The economic interest of carbonate rocks is very important in chemical or biological procedures and in the field of construction. Carbonate rocks exploitation depends on their quality and their physical, chemical and geotechnical characteristics. A fast, economic and reliable technique would be an evolutionary advance in the exploration of carbonate rocks. This paper discusses the ability of ultrasonic wave velocity to evaluate some mechanical and physical parameters within carbonate rocks (collected from different regions within Tunisia). The ultrasonic technique was used to establish empirical correlations allowing the estimation of UCS values, the density and the porosity of carbonate rocks. The results illustrated the behavior of ultrasonic pulse velocity as a function of the applied stress. The main output of the work is the confirmation that ultrasonic velocity can be effectively used as a simple and economical non-destructive method for a preliminary prediction of mechanical behavior and physical properties of rocks.

• Journal of Radiation Protection and Research
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• v.45 no.2
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• pp.81-87
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• 2020

Background: Kori unit #1 is permanently shut down after a 40-year lifetime. The Nuclear Safety and Security Commission recommends establishing initial decommissioning plans for all nuclear and radwaste treatment facilities. Therefore, the Korea Atomic Energy Research Institute (KAERI) must establish an initial and final decommissioning plan for radwaste-treatment facilities. Radiation safety assessment, which constitutes one chapter of the decommissioning plan, is important for establishing a decommissioning schedule, a strategy, and cost. It is also a critical issue for the government and public to understand. Materials and Methods: This study provides a method for assessing external radiation dose to workers during decommissioning. An external dose is calculated following each exposure scenario, decommissioning strategy, and working schedule. In this study, exposure dose is evaluated using the deterministic method. Physical characterization of the facility is obtained by both direct measurement and analysis of the drawings, and radiological characterization is analyzed using the annual report of KAERI, which measures the ambient dose every month. Results and Discussion: External doses are calculated at each stage of a decommissioning strategy and found to increase with each successive stage. The maximum external dose was evaluated to be 397.06 man-mSv when working in liquid-waste storage. To satisfy the regulations, working period and manpower must be managed. In this study, average and cumulative exposure doses were calculated for three cases, and the average exposure dose was found to be about 17 mSv/yr in all the cases. Conclusion: For the three cases presented, the average exposure dose is well below the annual maximum effective dose restriction imposed by the international and domestic regulations. Working period and manpower greatly affect the cost and entire decommissioning plan; hence, the chosen option must take account of these factors with due consideration of worker safety.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.219-219
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• 2006

This study focuses on the effects of dispersion method of a nanoparticle in a polymer matrix such as melt mixing, solution blending, and in-situ polymerization on the physical properties of the nanocomposites. Introduction of a nanoparticle to a polymer resulted in some unusual physical properties. In some cases the nanoparticle played a role of a nucleating agent, leading to decreasing induction time to crystallization. In addition, the dispersion state of the nanoparticle in the polymer matrix also had a significant influence on the physical properties of the nanocomposites. Hence the method of introducing the nanoparticle to the polymer made contribution to the rheological properties of the nanocomposite systems.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.100-100
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• 2013

Among recently discovered 2-dimensional materials, molybdenum disulfide has fascinating physical properties. It is atomically thin and is a semiconductor with with a similar level of bandgap with silicon. Especially, its properties get interesting when it becomes thinner. Its bandgap goes through bandgap transition from indirect to direct gap. Also its gap size increases as its thickness decreases. In this talk, I am going to present our recent work on characterization of its electrical and optical properties. We used Raman and PL spectroscopy to observe its property dependence on thickness. We fabricated electrical devices to study optimal condition for MoS2 devices. Also we synthesized large-area MoS2 films for devices applications.

• Advances in nano research
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• v.10 no.4
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• pp.327-337
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• 2021

In this review, composite structures are used for many industries for at least four decades. Polymeric composites are one of the important structures in the aerospace and aviation industry because of their high strength and low weight. In this comprehensive review, mechanical behaviors, physical and mechanical properties of polymeric composites, different types of reinforcements, different methods to fabricate polymeric composites, historical structural composite materials for aviation and aerospace industries, and also different methods for the characterization are reported. How to use various methods of composite preparation using different nanofillers as reinforcements and its effect on the physical properties and mechanical behavior of composites are discussed as well.

• The Journal of Korean Physical Therapy
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• v.15 no.2
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• pp.146-156
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• 2003

Isolated rat thoracic aorta which is pharmacologically precontracted by phenylephrine induces photorelaxation when exposed to long wave length UV-light. The aim of the present study was to characterize the mechanism of UV-light induced by photorelaxation in the rat aorta. 1. UV light relaxed both endothelium-intact and -denuded rat aortic rings contracted by phenylephrine. The magnitude of relaxation on UV light was dependent on the exposure time and slightly greatly in endothelium-denuded rings than in endothelium-intact preparations. 2. L-NAME (10 nM - 100 $\mu$M) but not D-NAME completely inhibited the photorelaxation in a concentration dependent manner. 3. The UV-induced relaxation was inhibited by methylene blue (1 - 100 uM), and verapamil (100 nM), and removal of extracellular $Ca^{2+}$. In contrast, UV-light induced photorelaxation was potentiated by $N^{w}$-nitro-L-arginine (L-NNA) treatment. These results suggest that UV light-induced photorelaxation may be due to nitric oxide from exogenously administered L-arginine as well as endogenous nitric oxide donors such as amino acid and arginine derivatives

• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.502-522
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• 2022

Clay minerals are natural materials that show widespread applications in various branches of science, including environmental sciences, in particular the remediation of water contaminated with various water pollutants. Modified clays and minerals have attracted the attention of researchers in the recent past since the modified materials are seemingly more useful and efficient for removing emerging water contaminants. Therefore, modified engineered materials having multi-functionalities have received greater interest from researchers. The advanced clay-based materials are highly effective in the remediation of water contaminated with organic and inorganic contaminants, and these materials show enhanced selectivity towards the specific pollutants. The review inherently discusses various methods employed in the modification of clays and addresses the challenges in synthesizing the advanced engineered materials precursor to natural clay minerals. The changes in physical and chemical properties, as investigated by various characterization techniques before and after the modifications, are broadly explained. Further, the implications of these materials for the decontamination of waterbodies as contaminated with potential water pollutants are extensively discussed. Additionally, the insights involved in the removal of organic and inorganic pollutants are discussed in the review. Furthermore, the future perspectives and specific challenges in the scaling up of the treatment methods in technology development are included in this communication.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.234-243
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• 2022

This study aims to characterize the irradiated RBMK-1500 nuclear graphite in terms of both structural and radiological properties. The experimental results of morphological and structural analysis of the irradiated graphite samples by using SEM, Raman spectroscopy as well as the theoretical evaluation of primary displacement damage are presented. Moreover, the experimental and theoretical evaluation of the neutron flux is provided and the presence of several γ emitters in the analyzed graphite samples is assessed. Furthermore, the improved version of rapid analysis method for ¹⁴C activity determination is applied and the experimentally obtained results are compared with calculated ones. Results indicate that structural changes are uniform enough in all the analyzed samples. However, the distribution of radionuclides is non-homogeneous in the irradiated RBMK-1500 reactor graphite matrix. The comprehensive understanding of both structural and radiological characteristics of nuclear graphite is very important when dealing with decision about irradiated graphite waste management strategy or treatment options prior to its final disposal.