• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.547-559
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• 2012

The concrete structural design in domestic has based on the allowable stress design (ASD) method and ultimate strength design (USD) method. Recently limit state design (LSD) method has issued and attempted to adopt in geotechnical design. Because ASD method and USD method have restriction in economic design. In this study, the generated member forces were calculated about high strength concrete segment lining based on japanese LSD code. And it compared with domestic USD code for identifying the economic design possibility of LSD and domestic applicability. In analysis results, the aspect of moment had generated similarly each other but the member forces of japanese LSD code were decreased (26.0% of moment and 26.7% of shear force) comparing with USD method. For that reason, possibility of economic segment design with stable condition were identified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1379-1386
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• 2013

The present work reports the mismatch limit loads for a V-groove welded pipe for a circumferential crack using finite element (FE) analyses. To integrate the effect of groove angles on mismatch limit loads, one geometry-related slenderness parameter was modified by relevant geometric parameters including the groove angle, crack depth, and root opening based on plastic deformation patterns in the theory of plasticity. Circumferential through-wall cracks are located at the centre of the weldments with two different groove angles ($45^{\circ}$, $90^{\circ}$). With regard to the loading conditions, axial (longitudinal) tension and bending are applied for all cases. For the parent and weld metal, elastic-perfectly plastic materials are considered to simulate and analyze under- and over-matching conditions in plasticity. The overall results from the proposed solutions are found to be similar to the FE results.

• Membrane Journal
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• v.6 no.4
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• pp.203-212
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• 1996

The operating parameters influencing on limiting flux was investigated in the ultrafiltration of PVA, and a new model, which is based on the Amiar model using the concept of heat transfer coefficient, was devised to overcome the limitation of gel-layer model. Using polysulfone plate-unit membrane (MWCO=20,000) and hollow-fiber membrane (MWCO= 30,000), ultrafiltration characteristics of PVA was examined with the variation of operating parameters such as cross flow velocity, transmembrane pressure, temperature, and PVA concentration. According to experimental results, the ultrafiltration of PVA through polysulfone membrane is mainly controlled by well-known phenomena of concentration polarization caused by gel-layer formation. On the contrary, in hollow fiber membrane was observed upward limiting flux which can not be explained by gel-layer model. New model was applied to predict the upward limiting flux behavior with partial satisfaction. The application of new model including viscosity correction factor, however, revealed that PVA ultrafiltration is closely related to the viscosity of permeating fluid.

• Plant Journal
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• v.14 no.1
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• pp.47-51
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• 2018

This study analyzed the effect of power output reduction in coal fired power generation on the change of system marginal price and green house gas emissions. Analytical method was used for electricity market forecasting system used in korea state owned companies. Operating conditions of the power system was based on the the 7th Basic Plan for Electricity Demand and Supply. This as a reference, I analyzed change of system marginal price and green house gas emission by reduced power output in coal fired power generation. The results, if the maximum output was declined as 29 [%] to overall coal-fired power plant, system marginal price is reduced 12 [%p] compared to before and decreasing greenhouse gas emissions were 9,966 [kton]. And if the low efficiency coal fired power plant that accounted for 30 [%] in overall coal-fired power plant stopped by year, system marginal price is reduced 14 [%p] compared to before and decreasing greenhouse gas emissions were 12,874 [kton].

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.19-29
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• 2008

The main purpose of this study is to introduce Hauer's(2004) approach that overcomes current accident prediction models' limitation and to apply this approach to Korean situation using fatal accident data on motorways. After developing accident prediction models according to this approach, it is found that AADT and vertical grade could improve fitness of the model, whereas a radius of roads is not related to the number of accidents. The advantage of Hauer's approach is to reduce possibility to eliminate critical variables and to keep uncritical variables when we consider many variables to develop accident prediction models.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.309-312
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• 2005

High altitude ignition test was performed to understand high altitude ignition characteristics of slinger combustor. To verify ignition limits, test was carried out with variation of altitude and fuel nozzle rotational speed using AETF(Altitude Engine Test Facility) in KARI(Korea Aerospace Research Institute). From the result, the effect of major factors which affect on ignition characteristics was observed. The reduction of ignition limit with increasing altitude and expansion of ignition limit with increasing rotational speed of fuel nozzle was verified. Also minimum rotational speed of fuel nozzle at high altitude must be greater than that of seal level condition.

• Journal of the Korean GEO-environmental Society
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• v.3 no.1
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• pp.5-12
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• 2002

The effects of ground water level, shear strength parameters of refuse, and geological condition of ground on the slope stability of uncontrolled waste landfill were studied. The Janbu method of slices based on the limit equilibrium method was used to calculate the minimum factor of safety with respect to slope stability of landfill. The analytical results showed that the factor of safety for a fully dried condition of landfill increased 2.4~2.8 times as great as that for a fully saturated condition of landfill. Under the condition of actual ground water level, the factor of safety linearly increased with increasing both cohesion and internal friction angle of refuse. Also, when the potential failure surface passed through the underlying layer, the factor of safety and shape of potential failure surface were found to depend on geological conditions of underlying layer.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.208-215
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• 2006

A simply prepared graphite, pencil-type working electrode was utilized to monitor fenitrothion concentrations, using the cyclic voltammetry (CV) and square-wave (SW) stripping voltammetry methods. The optimum conditions for analysis were sought. A very low detection limit was obtained compared to that obtained when other common voltammetry methods are used. The optimal parameters of the pencil-type electrode were found to be as follows: a pH of 3.7, a frequency of 500 Hz, an SW amplitude of 0.1 V, an increment potential of 0.005 V, an initial potential of -0.9V, and a deposition time of 500 sec. The analytical detection limit was determined to be 6.0 ngL-1 (2.16410-11 molL-1) fenitrothion at SW anodic and CV, and the relative standard deviation at the fenitrothion concentration of SW anodic 10 ugL-1 was 0.30% (n = 15) under the optimum conditions. Analysis was directly conducted through in-vivo real-time assay.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.341-352
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• 2017

Well designed group bolted connections can exhibit excellent ductile behavior through the bearing mechanism until the occurrence of shear rupture in the bolt or in the connecting plate. This excellent ductility can be utilized in favor of economical connection design. In this study, comprehensive tests on single-bolt bearing connections were conducted and analyzed considering bearing boundary conditions. The primary objective was to propose a generalized bearing strength and load-deformation relationship that can be used for designing group-bolted connections. To this end, new bearing strength formula, deformation limits as well as new load-deformation relationship were first proposed. Especially the proposed load-deformation relationship can reflect the stiffness, strength, and geometrical boundary conditions of the joint. The proposed formula and relationship are validated based on test results.

• Journal of Korea Water Resources Association
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• v.44 no.5
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• pp.417-427
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• 2011

The open-channel flow with submerged vegetation shows distinct features in two separate regions, namely upper and vegetation layers. In the upper layer, the flow is akin to the open-channel flow, while the flow in the vegetation layer is relatively uniform with suppressed turbulence due to vegetation stems. This paper presents laboratory experiments to investigate the characteristics of turbulent flows and suspended sediment transport in open-channel flows with submerged vegetation. An open-channel facility, 0.5 m wide and 12 m long, was used for laboratory experiments. Various discharges were employed with depth ratios of 2~3, and wooden cylinders were used for vegetation. To make equilibrium suspension, sediment particles of median diameter of 75 ${\mu}M$ were fed until capacity condition. Laser Doppler velocimeter was used to measure instantaneous velocity, and direct sampling with vinyl tube was used to measure the concentration of suspended sediment. Using the sampled data, the mean flow and turbulence structures were provided and characteristics of suspended sediment concentration with Rouse number were presented.