• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.259-270
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• 2007

This paper presents an analytical method of evaluating the flexural behavior of RC (reinforced concrete) beams strengthened with high-strengh bars. The former experimental results were used to compare with the analytical results. The experimental results also outline the advantages of externally strengtheng method with high-strenght bars. To evaluate the flexural behavior of RC beams strenghtend with unbonded high-strength bars, this paper proposes a method involving a simple strength-summation method. This method basically assumes that the total strength of RC beams strengthened with high-strength bars is equal to the sum of the strengths of the RC beams and the high-strength bars. This analytical method also includes the effects of compressive force due to the tension from high-strength bars. A comparison of the analytical and experimental results leads to the conclusion that the simple strength-summation mothod can simulate the flexural behavior of RC beams strengthened with high-strength bars with a good level of accuracy.

• Journal of Korean Association for Spatial Structures
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• v.8 no.5
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• pp.67-74
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• 2008

Multi-layered stone masonry monuments, such as stone pagoda can be modeled as a multi-degrees of freedom system. The dynamic behavior of these structures are mainly influenced by contour condition of contacting surface of stones. In this case the mass of the system can be easily estimated, mean while the estimation of stiffness at junction is not simple. In this paper a method for estimating the spring constant at the contacting surface of stone in proposed. This paper describes a method of computational modelling technique for structural analysis of stone pagodas using measurement of natural frequency and eigenvalue analysis. For this purpose Five story stone pagoda in Cchongnimsa site was selected as a model.

• Journal of the Korean Chemical Society
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• v.30 no.4
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• pp.352-358
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• 1986

An extensive experimental survey on the retention behaviors of phenols in the binary solvent system such as methanol-water, acetonitrile-water and tetrahydrofuran-water as well as the ternary solvent system such as methanol-acetonitrile-water and methanol-tetrahydrofuran-water is presented. A linear equation, which describes the capacity factor as a function of the solvent composition in the mobile phase and is able to predict the retention behaviors of phenols, was obtained. The iso-eluotropic lines for the binary and ternary solvent system are based on the equal strength of the methanol-water solvent which shows an optimum separation of the phenols used. The specific effect of each solute in the binary solvent system appeared to be larger than those in the ternary system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.1
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• pp.25-33
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• 2008

Water waves are generated mainly by winds in open seas and large lakes. They carry a significant amount of energy from winds into near-shore region. Thereby they significantly contribute to the regional hydrodynamics and transport process, producing strong physical, geological and environmental impact on coastal environment and on human activities in the coastal area. Furthermore an accurate prediction of the hydrodynamic effects due to wave interaction with offshore structures is a necessary requirement in the design, protection and operation of such structures. In the present paper surface and internal waves scattering by thin surface-piercing and bottom-standing vertical barriers in a two-layer fluid is analyzed in two-dimensions within the context of linearized theory of water waves. The reflection coefficients for surface and internal waves are computed and analyzed in various cases. It is found that wave reflection is strongly dependent on the interface location and the fluid density ratio apart from the barrier geometry.

• Journal of Korean Society of Transportation
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• v.15 no.4
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• pp.53-71
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• 1997

This paper presents a methodology for estimating average travel speed using volume and occupancy data from single magnetic loop detectors for signalized arterials. Three methods were developed and evaluated using field data: VPLUSKO method, fuzzy control method, and neural network method. While the VPLUSKO method is easy to apply, it results poor performances compared to other methods. The neural network method showed the best performances among the candidate methods. This method revealed the weakness in transferability, however. From limited cases of field test, it was concluded that the method of the fuzzy control application showed reasonable performance of estimation. It was also demonstrated that the fuzzy control method has the capability of transferability.

• Journal of Korean Association for Spatial Structures
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• v.11 no.1
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• pp.121-130
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• 2011

Space frame structures have the advantage of constructing a large space structures without column and it may be considered as a shell structure. Nevertheless, with the characteristics of thin and long term of spacing, the unstable problem of space structure could not be set up clearly, and there is a huge difference between theory and experiment. Therefore, in this work, the tangential stiffness matrix of space frame structures is studied to solve the instability problem, and the nonlinear incremental analysis of the structures considering rise-span ratio(${\mu}$) and the ratio of load($R_L$) is performed for searching unstable points. Basing on the results of the example, global buckling can be happened by low rise-span ratio(${\mu}$), nodal buckling can be occurred by high rise-span ratio(${\mu}$). And in case of multi node space structure applying the ratio of load($R_L$), the nodal buckling phenomenon occur at low the ratio of load($R_L$), the global buckling occur a1 high the ratio of load($R_L$). In case of the global buckling, the load of bifurcation is about from 50% to 70% of perfect one's snap-through load.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.157-165
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• 2011

With respect to the trend of highway traffic accident, highway accident is in decline, whileas, the fatality is on an increasing trend. Thus, many efforts to decrease highway traffic accidents and improve the safety, are required. In particular, in case of highway, the management standard by grade for accident black spot is designated. Thus, investing the effect factors by grade for highway traffic accident is required in detail. Thus, in this study, the factors affecting the traffic accidents among the environmental factors based on the graded data for the accident black spot in the applicable section targeting the Seoul-Pusan Express Highway, were reviewed; accident forecasting model which would analyze the characteristics of the accidents for determining the accident grade, was developed. As a result of establishing a model by using Quantification Theory of Type II, considering the characteristics of the dependent and independent variables based on the geometric structure, 'the fixed variable' among the variables relating to the accident, for the variables influencing over the accident grade, 'the type of vans, a chassis and people', 'the trailers, special vehicles and chassis people' and 'the negligence of watching and cloudy weather' were analyzed as common factors, in case of 'horizontal alignment', 'longitudinal slope' and, 'barricade' respectively.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.151-160
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• 1999

A series of laboratory tests for the marine clay sampled under the sea of Kwangyang bay have been conducted. The main types of tests are the general index property tests, the oedometer tests and the triaxial compression tests in both undrained(CIU) and drained(CID) conditions. The clayey samples, classified as CL, CH with natural water content of 38.3~84.6% and liquidity index of 0.71~0.98, are in the normally consolidated state with O.C.R. of 1.0l~l.60. The undrained stress path from CIU tests can be normalized with isotropic consolidation pressure$(p_0)$ and equal shear strain contour is linear passing through the origin in the (q, p) plot. The undrained shear strain is found to be the only function of the stress ratio($\eta$) and linear with intercept in the ($\varepsilon/\eta,\eta$) plot. The built-up pore pressure normalized with pc is also linear with respect to $\eta$. and its slope is defined by ´C´ as a pore pressure parameter. Equations to predict the undrained stress path and the shear strain are proposed. It is proved that the proposed equations give better agreements to the measured values than the Cam-clay theories. The failure points of the stress path are located on the same C.S.L. in (q, p) plot during both CIU and CID tests, which justifies the concept of critical state theory.

• The Journal of the Acoustical Society of Korea
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• v.24 no.2
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• pp.78-86
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• 2005

This study considers the magnitude of the harmonic components radiated from the ultrasonic contrast agents (UCA) activated by a typical diagnostic ultrasound. The nonlinear dynamic response of UCA to a 2 MHz diagnostic ultrasound pulse was predicted using Gilmore Model. The elastic property of the shell membrane of the UCA was ignored in the numerical model. Simulation was carried out for the UCA varying from 1 - 9 $\mu$m in its initial radius and the driving diagnostic ultrasound whose mechanical index (MI) ranges from 0.125 to 8. The powers of the sub. ultra and second harmonics of the acoustic signal from the UCA activated were compared with that of the fundamental component. The results show that. if the UCA is bigger than its resonant size (2 $\mu$m in radius for the present case) the sub harmonic power was much bigger than the fundamental. In particular, the 2nd harmonic component currently used as an imaging parameter for the harmonic imaging, was predicted to be lower in power than both the sub and the ultra harmonic component. This study indicates that, for obtaining harmonic imaging with UCA, the sub or ultra harmonics could be taken as imaging parameters better than the 2nd harmonic component.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.337-346
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• 2014

This study aimed to understand the mode characteristics of a droplet subject to periodic forced vibration and the detachment of a droplet placed on a plate surface. An surface was coated with Teflon to clearly observe the behavior of a droplet. The contact angle between the droplet and surface and the hysteresis were found to be approximately $115^{\circ}C$ and within $25^{\circ}C$, respectively. The coating process was performed in a clean room that had an environment with a low level of contaminants and impurities such as air dust, detergents, and particles. To predict the resonance frequency of a droplet, theoretical and experimental approaches were applied. Two high-speed cameras were configured to acquire side and top views and thus capture different characteristics of a droplet: the mode shape, the detachment, the separated secondary droplet, and the waggling motion. A comparison of the theoretical and experimental results shows no more than 18 discrepancies when predicting the resonance frequency. These differences seem to be caused by contact line friction, nonlinear wall adhesion, and the uncertainty of the experiment. For lower energy inputs, the contact line of the droplet was pinned and the oscillation pattern was axisymmetric. However, the contact line of the droplet was de-pinned as the oscillation became more vigorous with increased energy input. The size of each lobe at the resonance frequency is somewhat larger than that at the neighboring frequency. A droplet in mode 2, one of the primary mode frequencies, exhibits vertical periodic movement as well as detachment and secondary ejection from the main droplet.