• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.207-215
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• 2015

In the last decade, increasing national research fund for recycling the waste FRP (fiber reinforced plastics) ships which has caused environmental problems, improves the technology making concrete-reinforcing fibers out of the waste FRP. Furthermore, the concrete with recycled FRP fiber was tested for the structural performance. Experimental strength tests show that use of recycled FRP powder does not reduce the compressive strength of high strength concrete, and does increase the fire resistance performance of high strength concrete significantly. But, the study in investigating the properties of recycled fiber powder from waste FRP has not been completed because of the absence of the method of separation of mat layer from the waste FRP. This study is to propose a new extracting method of the mat layer from waste FRP, which is the efficient and environment friendly system. and thus it is considered to be the useful recycling method for fire resistance high concrete products or structures.

• Journal of the Korean Society of Safety
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• v.9 no.2
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• pp.18-25
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• 1994

In this thesis, the fatigue tests were performed on a series of reinforced concrete to Investigate the variation of strength and the safety of reinforced concrete structures under fatigue load. The specimens were of the same rectangular cross-section, of effective height 24cm and width 30cm and their span was 330cm. The three point loading system is used in the fatigue tests. In these tests, the fracture mode of reinforced concrete structures under fatigue load, relationship between the repeated loading cycles and the mid-span displacement of the specimens were observed. According to the test results, the following fatigue behavior of reinforced concrete specimens were observed. By increasing of the number of repeated loading cycles, the mid-span displacement became greater, however the Incremental amounts of the displacement were reduced. It could be also known that the inelastic strain energy of the doubly reinforced rectangular beams was larger than that of the singly reinforced rectangular beams as increasing the number of repeated loading cycles. Compliance of reinforced concrete structures tended to be reduced as increasing the repeated loading cycles, and the compliance of the doubly reinforced rectangular beams was generally smaller than that of the singly reinforced rectangular beams. Based on the above investigation, it could be concluded that the doubly reinforced rectangular beams under fatigue load were more efficient to resist the brittle fracture than the singly reinforced rectangular beams.

• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.380-387
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• 2015

A lead slowing-down spectrometer (LSDS) system is a promising nondestructive assay technique that enables a quantitative measurement of the isotopic contents of major fissile isotopes in spent nuclear fuel and its pyroprocessing counterparts, such as $^{235}U$, $^{239}Pu$, $^{241}Pu$, and, potentially, minor actinides. The LSDS system currently under development at the Korea Atomic Energy Research Institute (Daejeon, Korea) is planned to utilize a high-flux ($>10^{12}n/cm^2{\cdot}s$) neutron source comprised of a high-energy (30 MeV)/high-current (~2 A) electron beam and a heavy metal target, which results in a very intense and complex radiation field for the facility, thus demanding structural shielding to guarantee the safety. Optimization of the structural shielding design was conducted using MCNPX for neutron dose rate evaluation of several representative hypothetical designs. In order to satisfy the construction cost and neutron attenuation capability of the facility, while simultaneously achieving the aimed dose rate limit (< $0.06{\mu}Sv/h$), a few shielding materials [high-density polyethylene (HDPE)eBorax, $B_4C$, and $Li_2CO_3$] were considered for the main neutron absorber layer, which is encapsulated within the double-sided concrete wall. The MCNP simulation indicated that HDPE-Borax is the most efficient among the aforementioned candidate materials, and the combined thickness of the shielding layers should exceed 100 cm to satisfy the dose limit on the outside surface of the shielding wall of the facility when limiting the thickness of the HDPE-Borax intermediate layer to below 5 cm. However, the shielding wall must include the instrumentation and installation holes for the LSDS system. The radiation leakage through the holes was substantially mitigated by adopting a zigzag-shape with concrete covers on both sides. The suggested optimized design of the shielding structure satisfies the dose rate limit and can be used for the construction of a facility in the near future.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.102-105
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• 2006

Nowadays, increase of demands on efficient utilization of resources while construction process stimulates structural engineers to select remodeling to improve old buildings. To analyze the effects of openings that may be installed in the course of remodeling old buildings, an experimental research was carried out using four approximately half scale of specimens subjected to constant axial forces, and cyclic loading to simulate seismic conditions. Consequently, the existence of opening was verified to induce different observed damages, which caused by reduction of compression strut support formed on the surface of wall. Especially, the maximum force was revealed to decrease approximately 35% as openings were existed. As this tendency was appeared with stiffness and energy dissipation capacity.

• Advances in concrete construction
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• v.8 no.2
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• pp.91-100
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• 2019

In this paper three damaged exterior RC beam-column joints made of recycled aggregate concrete (RAC) were repaired. The aim of the study was to restore back the lost capacity of the beam-column joint to the original state or more. A relatively cheap material locally available galvanized steel welded wire mesh (GSWWM) of grid size 25 mm was used to confine the damaged region and then jacketed with cement mortar. Repaired specimens were also subjected to similar cyclic displacement as those of unrepaired specimens. Seismic parameters such as load carrying capacity, ductility, energy dissipation, stiffness degradation etc. were analyzed. Results show that repaired specimens exhibited better seismic performance and hence the adopted repairing strategies could be considered as satisfactory. These findings would be helpful to the field engineers to adopt a suitable rapid and cost efficient repairing technique for restoring the damaged frame structural joints for post earthquake usage.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.1
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• pp.53-59
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• 2013

Since 1990s, the major recycling methods for mechanical recycling of FRP(Fiber Reinforced Plastics)boats has involved shredding and grinding of the scrap FRP in a new recycled product. But still it leads to secondary problem such as air pollution, unacceptable shredding noise level and few limited applications. This study is to propose a newly advanced method which is more efficient and environment friendly waste FRP regenerating system. As extracting FRP layer and making the recycled fiber for recycled-fiber reinforced concrete(RFRC) from waste FRP, the recycling process has some merits in a sense of the recycling energy and the environmental effects. In this study, for those tasks, spectro-chemical differentiation method and coloring water-soluble dye treatment makes the roving layer more distinguishable photophysically. Also that has remarkably reduced safety hazards and energy. Using the mechanical properties of polymers and composite, FRP with the orthotropic and laminated plastic structure has been easily separated in the new extracting system. Also the new method has introduced five kind of separating manuals for the some different compositions of FRP boats. The roving fiber of laminated glass-fiber layer is as good as the polyvinyl fiber which is cost-high commercial fiber to increasing strength of concrete products. The early study has shown the effectiveness of laminated glass-fiber layer which also is chemical-resistant due to the resin coating. These results imply that more efficient and environment friendly recycled glass fiber can be better applied to the fiber reinforced concrete(FRC) substitute and this study also has shown wide concrete applications with RFRC from the waste FRP boat.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.513-520
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• 2018

Since Paris Climate Change Conference in 2015, many policies to reduce the emission of greenhouse gas have been accelerating, which are mainly related to renewable energy resources and micro-grid. Presently, the technology development and demonstration projects are mostly focused on diversifying the power resources by adding wind turbine, photo-voltaic and battery storage system in the island-type small micro-grid. It is expected that the large-scaled micro-grid projects based on the regional district and town/complex city, e.g. the block type micro-grid project in Daegu national industrial complex will proceed in the near future. In this case, the economic cost or the carbon emission can be optimized by the efficient operation of energy mix and the appropriate construction of electric and heat supplying facilities such as cogeneration, renewable energy resources, BESS, thermal storage and the existing heat and electricity supplying networks. However, when planning a large residential town or city, the concrete plan of the energy infrastructure has not been established until the construction plan stage and provided by the individual energy suppliers of water, heat, electricity and gas. So, it is difficult to build the efficient energy portfolio considering the characteristics of town or city. This paper introduces an energy mix optimization(EMO) method to determine the optimal capacity of thermal and electric resources which can be applied in the design stage of the real large-scaled residential town or city, and examines the feasibility of the proposed method by applying the real heat and electricity demand data of large-scale residential towns with thousands of households and by comparing the result of HOMER simulation developed by National Renewable Energy Laboratory(NREL).

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.225-231
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• 2007

In the recent construction industry, FRP is highly interesting in strengthening members of structures because it has superior material properties. This paper is an experimental study on the structural behavior of reinforced concrete beam when in using various amount of CFRP and the ductility of beams using various type of CFRP. In the experiment, when it makes an experiment using various amount of CFRP, strengthening width is more efficient than strengthening layer. The failure of CFRP strengthened beams presented brittle modes with having flexural failures. Also, It represented that most of beams classify brittle failure in the side of energy ratio. Energy ratio of CFRP sheet comparing with CFRP plate exceeds overall 50% and it represents about 70% in case of beams without strengthening layer.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1783-1790
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• 2023

Barium Bismuth Oxide Borate (BBOB) has been synthesized for the first time using solution combustion technique. SEM analysis reveal flower shape of the nanoparticles. The formation of the nanoparticles has been confirmed through XRD & FTIR studies which gives the physical and chemical structure of the novel material. The UV light absorption is observed in the range 200-300 nm. The present study highlights the radiation shielding ability of BBOB for different radiations like X/Gamma rays, Bremsstrauhlung and neutrons. The gamma shielding efficiency is comparable to that of lead in lower energy range and lesser than lead in the higher energy range. The bremsstrauhlung exposure constant is comparably larger for BBOB NPs than that of concrete and steel however it is lesser than that of lead. The beauty of BBOB nanoparticles lies in, high absorption of radiations and low emission of secondary radiations when compared to lead. In addition, the neutron shielding parameters like scattering length, absorption and scattering cross sections of BBOB are found to be much better than lead, steel and concrete. Thus, BBOB nanoparticles are highly efficient in absorbing X/Gamma rays, neutrons and bremsstrauhlung radiations.

• Earthquakes and Structures
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• v.16 no.5
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• pp.625-639
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• 2019

The concept of the combined seismic and energy retrofitting of existing reinforced concrete (RC) buildings was examined in this paper through a number of case studies conducted on model buildings (simulating buildings of the '60s-'80s in southern Europe) constructed according to outdated design standards. Specifically, seismic and thermal analyses have been conducted prior to and after the application of selected retrofitting schemes, in order to quantify the positive effect that retrofitting could provide to RC buildings both in terms of their structural and energy performance. Advanced materials, namely the textile reinforced mortars (TRM), were used for providing seismic retrofitting by means of jacketing of masonry infills in RC frames. Moreover, following the application of the TRM jackets, thermal insulation materials were simultaneously provided to the RC building envelope, exploiting the fresh mortar used to bind the TRM jackets. In addition to the externally applied insulation material, all the fenestration elements (windows and doors) were replaced with new high energy efficiency ones. Afterwards, an economic measure, namely the expected annual loss (EAL) was used to evaluate the efficiency of each retrofitting method, but also to assess whether the combined seismic and energy retrofitting is economically feasible. From the results of this preliminary study, it was concluded that the selected seismic retrofitting technique can indeed enhance significantly the structural behaviour of an existing RC building and lower its EAL related to earthquake risks. Finally, it was found that the combined seismic and energy upgrading is economically more efficient than a sole energy or seismic retrofitting scenario for seismic areas of south Europe.