• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.25-30
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• 2000

The relation between the phase-shift profile for the intermediate frequencies and the Langmuir adsorption isotherm at the poly-$Pt/0.1\;M\;H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The suggested interfacial equivalent circuit consists of the serial connection of the electrolyte resistance ($R_S$), the faradaic resistance $(R_F)$ and the equivalent circuit element $(C_P)$ of the adsorption pseudocapacitance $(C_\varphi)$. The delayed phase shift $(\varphi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\varphi=-tan^{-1}[1/2{\pi}f(R_s+R_F)C_p]$. The phase-shift profile $(\varphi\;vs.\;E)$ for the intermediate frequency (ca. 6Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm (9 vs. E). The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-$Pt/0.1\;M\;H_2SO_4$ electrolyte interface are $1.8\times10^{-4}\;and\;21.4kJ/mol$, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.2
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• pp.86-97
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• 2005

Accurate estimation of the wave-induced pore water pressure in the seabed is key factor in studying the stability of the seabed in the vicinity of coastal structure. Most of the existing numerical models for wave structure seabed interaction have been linked through applying hybrid numerical technique which is analysis method separating the wave field and seabed regime. Therefore, it is necessary to develope a numerical model f3r simulating accurately wave$\cdot$structure$\cdot$ seabed interaction under wave loadings by the single domain approach for wave field and seabed regime together. In this study, direct numerical simulation is newly proposed. In this model, modeled fluid drag has been used to detect the hydraulic properties according to the varied geometrical shape inside the porous media by considering the turbulence resistance as well as laminar resistance. Contrary to hybrid numerical technique, direct numerical simulation avoids the explicit formulation of the boundary conditions at the fluid/porous media interface. A good agreement has been obtained by the comparison between existed experimental results by hydraulic model test and direct numerical simulation results far wave $\cdot$structure$\cdot$seabed interaction. Therefore, the newly proposed numerical model is a powerful tool for estimating the nonlinear dynamic responses among a structure, its seabed foundation and water waves.

• Korean Journal of Environmental Agriculture
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• v.15 no.4
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• pp.455-463
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• 1996

Studies were carried out to determine the effect of sulfur dioxide on leaf injury and yield of ten soybean cultivars. Plants were fumigated with 2.0 ppm of $SO_2$ for 4 or 8 h in a closed-top field chamber. In the comparison of foliar injury, Paldalkong and Eunhakong were more susceptible to $SO_2$ than Bogwangkong, Jangsukong, and Jangkeungkong. Correlations between chlorophyll contents, peroxidase activity, and stomatal resistance of leaves and foliar susceptibility were insignificant. However, significant correlations $(r=-0.611^{\ast})$ were found between superoxide dismutase activity and foliar injury rates. Dry weight, number of pods and total grains were significantly reduced by $SO_2$ fumigation but plant height, number of nods and weight of 100 grains were not affected. Yield reduction rates were higher in Eunhakong and Paldalkong than in Bogwangkong and Jangkeungkong. A liniar relationship was found between foliar injury rate and the percent crop loss with a significant coefficient of b=-1.17 in the susceptible cultivar of Paldalkong, but Bogwangkong, insusceptible cultivar, showed lower value of -0.165.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.241-252
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• 1998

The objective of the research stated herein is to observe the actual responses of a low-rise nonseismic moment-resisting reinforced concrete frame subjected to varied levels of earthquake ground motions. First, the reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used and the model was manufactured according to the similitude law. This model was, then, subjected to the shaking table motions simulating Taft N21E component earthquake ground motions, whose peak ground accelations (PGAs) were modified to 0.12g, 0.2g, 0.3g, and 0.4g. The lateral accelerations and displacements at each story and local deformations at the critical reginos of the structure were measured. The base shear was measured by using self-made load cells. Before and after each earthquake simulation test, free vibration tests were performed to find the change in the natural period and damping ratio of the model. The test data on the global and local behaviors are interpreted. The model showed the linear elastic behavior under the Taft N21E motion with the PGA if 0.12g, which represents the design earthquake in Korea. The maximum base shear was 1.8tf, approximately 4.7 times the design base shear. The model revealed fairly good resistance to the higher level of earthquake simulation tests. The main components of its resistance to the high level of earthquakes appeared to be 1) the high overstrength, 2) the elongation of the fundamental period, and 3) the minor energy dissipation by inelastic deformations. The drifts of the model under these tests were approximately within the allowable limit.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.569-575
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• 2007

The repair of concrete surfaces does not normally take into account structural tolerance for longer service lift and better capabilities of concrete structures. In particular, the repair of surface spelling completes as mortar is applied, which does not display additional structural performances. The use of crimped wire mesh for better construction and fracture resistance, however, expects to have some reinforcement effects. Particularly, it is also expected that the repair of bottom part in structures built between bridges like irrigation structures results in the increase of flexural resistance. Therefore, this study is intended to perform the repair using crimp wire mesh and examine strength depending on the repair section and depth. For this, a slab with 150 mm in depth, 3,000 mm in length and 600 mm in width and total 8 objects to experiment such as upper part, upper whole, bottom part, bottom whole and crimp wire mesh reinforced are manufactured to perform flexural performance. The results of the analysis show that yield strength and failure load increase as the depth of repair materials in the experiment reinforced with crimp wire mesh get bigger. In the same condition, repair of bottom part is able to increase internal force of bending force. Besides, the results show that partial repair of structures under bending force cannot produce flexural performance. Consequently, the repair method with crimp wire mesh results in the increase of flexural resistance.

• Journal of the Korean Institute of Landscape Architecture
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• v.36 no.3
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• pp.21-28
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• 2008

The management of soil organic matter(SOM) is a key component of golf course green maintenance. As part of a major project examining the sustainable management of SOM on golf course greens, the SOM status of different age greens maintained in the same root zone composition and management were compared. Then the microbial activity, tiller number, bulk density, water content, pH, EC, and T-N in the soil were measured. In the 0${\sim}$5cm depth SOM accumulation showed no significant difference between greens. Below 5cm SOM showed a strong significance between greens and had a positive(+) correlation with year and negative(-) correlation with depth. when regression equations were used to predict SOM accumulation with year and depth, SOM below 5cm tended to increase with a rate of 0.061% . year$^{-1}$ and decrease with a rate of 0.079% . $cm^{-1}$(R2==0.841). Soil microbial activity was investigated with age and depth by using a dehydrogenase assay. Results showed a sharp drop with depth in all greens. The soil microbial activity below 5cm showed no difference between greens. The accumulated SOM below 5cm may be very resistant to decomposition in the long-term. Five years after establishment, the bulk density did not significantly change. The water content, EC, and T-N had a significant correlation with SOM. The pH decreased with the year, which may influence SOM accumulation. Organic matter accumulation was mainly affected by the pH decrase，low soil microbial activity, and high organic matter resistant to decomposition, but the effects of water content, EC, and T-N were obscure.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.97-107
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• 2005

Since the purpose of wheel tracking test is to find out relative difference of mixture's rut resistance, the wheel is an important part in the test for obtaining a consistent output. This study is performed to examine efficiency of different wheel material, rubber and steel in wheel tracking test. The rubber was inserted as a ring on the outer face of the steel wheel, and thickness of rubber ring was 15mm and 7.5mm and 0mm (steel wheel without rubber), making the total outer diameter 200mm. The objective of this study was to select reliable wheel material type in wheel tracking test at $60^{\circ}C$ based on variance in output (rut depth and dynamic stability) and correlation with SD (deformation strength). The result of regression analysis of rut depth with Sd showed that $R^2$ values of wheel rubber thickness of 15mm, 7.5mm and 0mm were 0.7, 0.8 and over 0.9, respectively. In a case of steel wheel (0mm), the highest $R^2$ value was 0.9569. Therefore, the wheel without rubber ring was the best in output consistency level and coefficient of determination $(R^2)$ with deformation strength. Therefore, the steel wheel without rubber ring is suggested as the best choice for wheel tracking test of asphalt concrete.

• Journal of the Korean Institute of Gas
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• v.9 no.1 s.26
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• pp.1-8
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• 2005

In this study, the FE analysis has been presented for the leakage safety of $9\%$ nickel type LNG storage tank based on the thermal resistance effects between insulation panels, comer protection and prestressed concrete(PC) structures. The FEM calculated results show that the leakage safety of fiber glass blanket, perlite powder and cellular glass insulators does not guarantee any more due to a strength failure of the insulation structure. But the corner protection and PC structure of outer tank may delay or sustain the leaked LNG of 10 days even though the inner tank and insulation structure are simultaneously failed. This means that $9\%$ nickel steel type LNG storage tank may be safe because of a high strength of the corner protection and outer tank structures.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.819-825
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• 2006

The objective of the present study is to verify the validity of a new truss model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. The new truss model is based on the relationship between shear and bending moment in a beam subjected to combined shear and bending. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. On the basis of the analytical results, the contribution by the web to shear resistance can be constant and have an excellent linear correlation with the web reinforcement ratio. The present decoupling approach may provide a simple way for the assessment of the role of each parameter or mechanism that affects the ultimate shear behavior of reinforced concrete beams.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.455-462
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• 2013

The effects of earthquakes can be devastating especially to existing structures that are not based on earthquake resistant design. This study proposes a steel grid shear wall that can provide a sufficient lateral resistance and can be used as a seismic retrofit method. The pushover analysis was performed on RC structure with and without the proposed steel grid shear wall. Obtain the performance point that the target structure for seismic loads applied to evaluate the response and performance levels. The capacity spectrum at performance point is nearly elastic range, so satisfied the performance objectives(LS level). And response modification factor(R factor) were calculated from the pushover analysis. The R factor approach is currently implemented to reflect inelastic ductile behavior of the structures and to reduce elastic spectral demands from earthquakes to the design level. The R factor increases from 2.17 to 3.25 was higher than the design criteria. As a result, according to reinforcement by steel grid shear wall, strength, stiffness, and ductility of the low-rise RC structure has been appropriately improved.