• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.101-107
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• 2013

Environmental-friendly and economical construction are the recent issues for civil structures and soilbag as facing wall is widely used for cut-slope remediation projects. However, the stability of structures is an important issue for the use of environmental-friendly and economical materials. In order to understand the stability of soilbag reinforced retaining wall, tensile resistance, rupture, tensile strength, and internal/external safety factor of the wall were analyzed with MSEW program and the results were compared to the safety factor of block-type reinforced walls. The stability of retaining wall was analyzed with reduction coefficients of connection strength to check the connection stability. Because it is possible to move between soilbag and geogrid connector for soilbag retaining wall, the safety factor of the wall was analyzed with different inclination angles of soilbag. The analysis result shows that the connection strength and internal/external stability of soilbag reinforced wall satisfy the stability criteria.

• Journal of Energy Engineering
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• v.14 no.1
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• pp.54-61
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• 2005

The APR1400 is an Advanced Pressurized Water Reactor with 3983 MWt power, 2×4 loops, and direct vessel injection system. The Fluidic Device (FD) is adopted to regulate the safety injection flow rate in a Safety Injection Tank (SIT) of APR1400. The performance of a newly designed fluidic Device is evaluated by analyzing a Large Break Loss-of-Coolant Accident (LBLOCA) using TRAC-M/F90, version 3.782. The analysis results show that the TRAC-M code reasonably predicts the important phenomena of blowdown, refill and reflood phases of LBLOCA. The sensitivity studies about gas/water volume changes in a SIT and K factor changes in a SI system were also done to understand the important phenomena with a Fluidic Device in APR1400.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.99-105
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• 2005

To evaluate structural safety factor of the jet vane for the thrust deflection system under the dynamic pressure and very high temperature($2700^{\circ}C$) of the combustion gas flow, the high temperature tension tests of refractory metals and 3-D nonlinear numerical simulations are performed. Through the analysis of high temperature structural behavior for jet vane, the structural safety of jet vane is evaluated, and numerical results are compared with static pound tests of jet vanes. It has been found that most of structural and thermal loading is concentrated on the vane shaft which worked as safe under $1400^{\circ}C$. From the comparison of static ground tests and numerical results, the evaluation criterion using the vane load and shaft displacement is more useful to estimate the structural safety than using the equivalent stress.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.3
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• pp.18-24
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• 2005

To evaluate structural safety factor of the jet vane for the thrust deflection system under the dynamic pressure and very high temperature(2700$^{\circ}C$ ) of the combustion gas flow, the high temperature tension tests of refractory metals and 3-D nonlinear numerical simulations are performed. Through the analysis of high temperature structure behavior for jet vane, the structure safety of jet vane is evaluated, and numerical results are compared with static ground tests of jet vanes. It has been found that most of structural and thermal loading is concentrated on the vane shaft which worked as safe under 1400$^{\circ}C$. From the comparison of static ground tests and numerical results, the evaluation criterion using the vane load and shaft displacement is more useful to estimate the structural safety than using the equivalent stress.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.2
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• pp.193-205
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• 2008

The construction of underground structures such as oil and food storage caverns are recently increasing in our country. The stability of those underground caverns are greatly influenced by their shape and size. In this study therefore, the effect that the shape of an underground cavern have on its stability were analyzed in terms of safety factor. To this end, caverns with 5 different shapes were investigated and sensitivity analyses were performed based on rock class, overburden, and lateral earth pressure coefficient. The proper amount of shotcrete and rockbolt as supports of a cavern was also assumed based on the shape and site of the cavern and rock conditions. This study is expected to be helpful in designing and evaluating the stability of caverns in future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.1
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• pp.75-82
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• 2011

Marine current energy is one of the most interesting renewable and clean energy resources that have been less exploited. Especially, Korea has worldwide outstanding tidal current energy resources and it is highly required to develop tidal in-stream energy conversion system in coastal area. The objective of study is to investigate harnessing techniques of tidal current energy and to design the a 100 kW horizontal axis tidal turbine using blade element momentum theory with Prandtl's tip loss factor for optimal design procedures. In addition, Influence of Prandtl's tip loss factor at local blade positions as a function of tip speed ratio was studied, and the analysed results showed that power coefficient of designed rotor blade using NACA 63812 was 0.49 at rated tip speed ratio.

• Journal of the Korean Society of Safety
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• v.5 no.1
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• pp.19-29
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• 1990

The objective of this paper is to investigate the effect of residual stresses on the $\Delta$K$\sub$th/ and fatigue crack growth behavior of butt weldments. For this purpose, transverse butt sutmerged arc welding was performed on SM50A steel plate and CT(compact tension) specimens which loading direction is perpendicular to weld bead were selected. Welding residual stresses distribution on the specimen was determined by hole drilling method. The case of crack located parallel to weld bead, the states of as weld and PWHT, $\Delta$K$\sub$th/ of specimens(HAZ, weld zone) was higher than that of the base metal probably because of the compressive residual stresses of crack tip. In low $\Delta$K region, it is estimated that the effects of residual stresses for da/dN are great. In region II, the da/dN of weldments in as weld state was lower than that of the base metal. Though da/dN of Weldments in PWHT state was similar to that of the base metal. The constant of power law, m in two states consisted with the base metal. Therefore , it is estimated that the value of m is not affected by residual stresses. Fatigue crack growth behavior of weldments consisted with the base metal considering the effective stress intensity factor range($\Delta$K$\sub$eff/) included the effect of initial residual stress(Kres). Thus, we can predict the fatigue crack growth behavior of weldment by knowing the distribution of initial residual stress at the crack tip.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.34 no.1
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• pp.67-76
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• 2024

Objectives: Direct reading instruments (DRIs) are widely used by industrial hygienists and other experts for preliminary survey and identifying source locations in many industrial fields. Photoionization detectors (PIDs), which are a form of hand-held portable DRIs, have been used for a variety of airborne vaporized chemicals, especially evaporated hydrocarbon solvents. The benefits of PIDs are high sensitivity between each chemical, competitive price, and portability. With the goal of increasing the accuracy of logged PID concentrations, previous studies have performed tests for the assessment of single chemical compounds, not mixtures. The purpose of this preliminary study was to measure mixtures with a PID and charcoal tube at the same time and compare the accuracy between them. Methods: A chamber test was implemented with different mixtures of hydrocarbon chemicals (acetone, isopropyl alcohol, toluene, m-xylene) and levels in the range of 14 to 864 ppm. Three PIDs and charcoal tubes were connected to the chamber and measured the chemical mixtures simultaneously. A comparison of accuracy and the PID group of concentrations with manufacture correction factor (M_CF) and field correction factor (F_CF) applied was performed. Results: The accuracy of the PID concentrations data-logged from the PID did not meet the accuracy criteria except for the mixture level B and C logged from PID No. 2, which was 18% of all tests for meeting accuracy criteria. The mean and standard deviation (SD) of concentration (ppm) of the charcoal tube followed by each mixtures' level were 10.37±0.26, 155.33±5.28, 300.80±11.65, and 774.93±22.65, respectively. When applying F_CF into the PID concentrations, the accuracy increased by nearly 82%. However, in the case of M_CF, none met the accuracy criterion. Between the PID there were differences of logged concentrations. Conclusions: In this preliminary study, the concentration of a logged PID with F_CF applied was a better way to increase accuracy compared to applying M_CF. We suggest that additional research is necessary to consider environmental factors such as temperature and humidity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.397-405
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• 2015

In the past, expressways focused on mobility. However, the paradigm of expressways fuction today has been changed from fast expressways to safe expressways as people's quality of living and consciousness level heightened. In 2012, 3,550 traffic accidents occurred on expressways and 371 people died. The fatality rate of traffic accidents on expressways is almost twice that on general national roads. This study developed accident forecast models (safety performance functions) based on the number of traffic accidents and traffic volumes on six major lines on expressways. It is difficult to forecast safety performance functions for each expressway line because the lines and the scales of expressways are different from each other; therefore, integrated safety performance functions of six lines were determined first, and the coefficients, which can correct the traffic accidents on each line, were calculated. It is believed that this study will contribute in the safer management of expressways by being used as basic information in the establishment of traffic safety strategies for each expressway line in prevention of traffic accidents. Moreover, more studies would be required in the future, which would suggest reliable accident forecasts by calculating correction coefficients by line through integrated models by groups dependent on the characteristics of each line.

• Journal of Ocean Engineering and Technology
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• v.16 no.1
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• pp.52-57
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• 2002

본 논문은 고온 고압의 유체를 수송하는 해저 파이프의 좌굴 현상에 대해서 논하였다. 고온 고압의 유체를 해저 파이프로 수송 할 때, 수송되는 고온 고압의 유체와 수위 해저의 온도와 압력들의 차에 의해서 유체 수송 파이프는 축 방향으로 압축력을 받게 되고 이 압축력을 견디지 못하면 수송 파이프는 수직 방향의 좌굴 현상이 발생하게 된다. 논문에서는 "semi-empirical design method"를 사용하여 수송 유체의 온도와 압력의 여러 가지 변화에 따라 파이프의 축 방향 압축력을 계산하고 수직 좌굴 현상에 따른 안전계수를 구하여 파이프의 초기 설계 결정에 도움을 주고자 했다.