• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.694-700
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• 2009

In this paper, we propose a RFID tag antenna with low performance degradation due to nearby dielectric materials. The proposed antenna is designed to be appropriate for ink printing fabrication. The antenna is designed to operate in UHF band of $860{\sim}960$ MHz. The antenna uses a T-matching network in the middle of the main body and two parasitic patches in vicinity for complex conjugate matching with a commercial tag chip. In addition, the two parasitic patches induce currents at different dielectric constants of nearby dielectric materials. This can minimize the performance degradation due to nearby dielectric materials. The measured results show the half power matching bandwidth from 844 MHT to 1,268 MHz. It exhibits the reading distance of about 3.5 m in free space when the tag antenna is used with the commercial reader antenna (transmitting power of 20 dBm and the reader antenna gain of 6 dBi). When the tag is attached on dielectric materials of wood and FR4, the resulting reading distances are 2.61 m and 2.51 m, respectively.

• Journal of Soil and Groundwater Environment
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• v.12 no.2
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• pp.37-46
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• 2007

This study developed composition-plastic media with woodchips and plastic as main materials, and examined the performance of media. Compared to the existing commercial media, the media had similar performance in removal efficiency and microbes attaching characteristic, and was evaluated that they are distinguished from economic side. Performance test of media was conducted to examine the removal capacity of toluene and hydrogen sulfide in a gas stream by using a lab-scale biotrickling filter systems packed with them. At a volumetric loading of $1.5\;m^3/hr$ with inlet concentration 260 ppm and empty bed residence time (EBRT) 42s, the toluene removal efficiency was shown over 90%, and the maximum elimination capacity of toluene in the biotrickling filter was $77g/m^3{\cdot}hr$. Effective co-treatments of $H_2S$ and Toluene were observed in the lab-scale biotrickling filters. The maximum elimination capacity of $H_2S$ was $100\;g-S/m^3{\cdot}hr$. Up to 100 ppm, the concentration of $H_2S$ did not have an effect on toluene removal efficiency, but the removal efficiency of toluene decreased with increasing inlet $H_2S$ concentration.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.3-14
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• 2012

This paper describes experimental results on the seismic performance of SHCC (strain-hardening cement composite) infill wall for improving damage tolerance capacity of non-ductile frame. To investigate the effect of tensile strain capacity and cracking behavior of SHCC materials on the shear behavior of SHCC infill wall, three infill walls were fabricated and tested under cyclic loading. The test parameter in this study is a type of cement composites; concrete and SHCCs. The two types of SHCC materials were prepared for infill walls. In order to induce crack damages into the mid-span of the infill wall, each infill wall had two 100-mm-deep-notches on both sides. Test results indicated that SHCC infill walls showed superior crack control capacities and much larger drift ratios at the peak loads than RC (reinforced concrete) infill wall, as expected. In particular, due to the bridging actions of the reinforcing fibers, SHCC matrix used in this study would delay the stiffness degradation of infill wall after the first inclined cracking. Moreover, from the damage classes based on the cracks' maximum width in the infill walls, it was observed that PIW-SHD specimen possessed nearly threefold seismic capacities compared to PIW-SLD specimen. Also, from the results on the strain of diagonal reinforcements, it can be concluded that the SHCC matrix would resist a part of tensile stresses transferred along steel rebar in the infill wall.

• Journal of Korean Society of Steel Construction
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• v.22 no.6
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• pp.553-561
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• 2010

The purpose of this paper is to analytically find the approximate supplement damping ratio of the viscous damper installed in self-centering (SC) single-degree-of-freedom (SDOF) systems with maximum displacements that are similar to those of elasto-plastic (EP) SDOF systems. The behavior of an SC SDOF system under harmonic cyclic loading was first described. Then an analytical model that can capture the behavior of the viscously damped SC SDOF system was introduced. Analysis parameters that characterize the hysteresis of the EP and SC SDOF systems were chosen, and nonlinear time-history analyses were performed using 20 historical accelerograms. Most of the SC SDOF systems with viscous dampers with approximately 10-15% damping ratios presented mean maximum displacement values that were similar to those of the EP SDOF systems. To investigate in detail the seismic performance of both systems, three EP SDOF systems and six corresponding SC SDOF systems were selected. The analyses showed that all the SC SDOF systems eliminated the residual displacements after the end of their shaking, and that the SC SDOF systems with 15% damping ratios performed better than the EP SDOF systems in terms of maximum displacement and acceleration response.

• Journal of Korean Society of Steel Construction
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• v.25 no.3
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• pp.289-297
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• 2013

In this study, the local buckling behavior of steel built-up columns, fabricated with grade 800MPa high performance (HSA800), was investigated to verify the suitability of width-to-thickness ratio limits adopted by the current design code. For this purpose, an experimental program was designed and performed for HSA800 steel column specimens with various width-to-thickness ratios. Then the experimental results were compared and verified with finite element analysis results. The parametric analytical studies with various width-to-thickness ratios were also performed to investigate the missing data from the limited experimental studies. From the experimental and analytical studies, It was found that the finite analysis models could reasonably estimate the test results within the 5.3% average differences. The local buckling behaviors of HSA800 steel columns were found to be largely depend on the values of initial imperfection introduced into finite element analyses.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.3
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• pp.116-121
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• 2004

Treatability tests were conducted to study the feasibility of EMMC process as a recycling-water treatment system in high density seawater aquaculture farm. To study the effect of organic and ammonia nitrogen loading rate on system performance, hydraulic retention time was reduced gradually from 12hr to 10min. The conclusions are can be summarized as follows. When the system HRT was reduced from 12hr to 2hr gradually, there was little noticeable change(reduction) in ammonia nitrogen removal efficiencies. However, removal efficiencies were decreased dramatically when the system was operated under the HRT of less than 2hr. In case of organics(COD), there was no dramatic change in removal efficiencies depending on HRT reduction. COD removal efficiencies were maintained successfully higher than 9％ when the system was operated at tile HRT of 10 min. System performances depending on media packing ratio in the reactors were also evaluated. There were little differences in each reactor performances depending on media packing ratio in reactor when the reactors were operated under the HRT of longer than 1hr. However, differences in reactor performances were considerably evident when the reactors were operated under the HRT of shorter than 1hr. When comparing reactor performance among 25％, 50％,7 5％ packed reactor, it can be judged that media packing ratio more than 50％ plays no significant role in increasing reactor performance. For this reason, packing the media less than 50％ is more reasonable way in view of economic. Such a tendency shown in COD removal efficiencies well agreed with the variation of ammonia-nitrogen removal efficiencies according to the media packing ratio in reactors at each HRT. Difference in effluent ammonia-nitrogen concentration between 50％ media packing reactor and 75％ media packing reactor was negligible. When comparing with the results of 25％ packing reactor, difference was not so great.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.37-44
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• 2015

This paper describes the effect of strain hardening cement composite (SHCC) material on structure performance of reinforced concrete (RC) beams with high-strength reinforcing bar. Also, this paper explores the structure application of SHCC in order to mitigation cracking damage and improve the ductility of flexural RC members. The prediction model for flexural strength of doubly reinforced SHCC beams are investigated in this study. To achieve the these objectives, a total of 6 rectangular beam specimens were tested under four point monotonic loading condition. The main parameters included the types of cement composite and reinforcing bar. Test results indicated that reinforced beam specimens with SHCC material were improved the structure performances and damage characteristics. Specifically, replacement of conventional high-strength concrete with SHCC materials has the potential of high-strength steel bar as flexural reinforcement on RC members. It is remarkable that suggested method of reinforced SHCC beams with high-strength reinforcing bar could be used usefully to the structure design.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.291-298
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• 2015

In this paper, a bundled diagonal reinforcement using high performance steel fiber was proposed to enhance the construct ability and seismic performance. Experiments of coupling beam was composed of four specimens and the hysteretic behavior evaluated for reverse cyclic loading to specimens using high performance steel fiber. The main variables of the experiment is a amount of stirrup and bundled reinforcement, depending on whether the mix of steel fiber. Specimen which criteria was applied 100% of stirrup and bundled diagonal reinforcement of ACI318 criteria. With this, by appling same diagonal reinforcement, two specimens were created by adjusting stirrup of 75%, 50%. So, a total of four specimens were produced. When coupling beam was placed concrete, this experiment was mixed in a content of steel fiber 1%. All the specimens were produced by aspect ratio 3.5(l/h=1050/300) to a half-scale. In this result, two specimens as reduced to stirrup of 75%, 50% was no significant difference in the strength, stiffness and energy dissipation capacity, respectively compared to the stirrup of 100%.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.261-269
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• 2013

In this study, it was developed eco-friendly inorganic binding material concrete using ground granulated blast furnace slag and alkali activator (water glass, sodium hydroxides). Eight reinforced concrete beam using inoganic binding material concrete were constructed and tested under monotonic loading. The major variables were mixture ratio of alkali activator, type of admixture and admixture. Experimental programs were carried out to improve and evaluate the flexural performance of such test specimens, such as the load-displacement, the failure mode, the maximum load carrying capacity, and ductility capacity. All the specimens were modeled in scale-down size. The eco-friendly concrete using inorganic binding material encouraged alkali activation reaction was rapidly hardening speed and showed possibility as a high strength concrete. Also, the RC beams using new materials showed similar behavior and failed similarly with RC beam used portland cement. It is thought that eco-friendly inorganic binding material concrete can be used with construction material and product as a basic research to replace cement concrete. If there is application to structures in PC member as well as production of 2nd concrete product, it could be improved the productivity and reduction of construction duration etc.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.613-621
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• 2012

Steel corrosion is one of the most critical deteriorations in concrete structures due to the problems associated with both durability and structural safety issues. For protection of steel against corrosion problems, researches to improve concrete durability and steel corrosion protection such as rebar coating by hot-dip galvanizing steel have been carried out. This study was performed to quantitatively evaluate anti-corrosion and structural performance of concrete structures reinforced with hot-dip galvanizing steel rebar. Preliminary tests for several metal coatings such as zinc, aluminum, and their alloy (Zn 45% + AL 55%) were performed. After evaluation of corrosive characteristics, Zn was selected for the coating material and the corrosion behaviors in Zn-coated steel were evaluated in various conditions. Furthermore, tensile and adhesive strengths were evaluated for the normal and the hot-dip galvanized steel. The crack patterns and structural behaviors of RC specimens with the normal and coated steel were investigated. Also, corrosion characteristics including corrosion in various coating metal and potential change in metal with notch were evaluated. Structural performances of tensile and adhesive strengths as well as RC beam behavior under flexural/shear loading were evaluated. The test and evaluation results showed that the applicability of hot-dip galvanized steel rebar can be used as corrosion resistant reinforcements for RC structures.