• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.3
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• pp.19-28
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• 2000

In general the data such as thrust, pressure, temperature and combustion time are measured in developing the propulsion system of solid rocket motor through static firing test. But in the case of personal surface to air missile there are required a severe safety specifications in order to eliminate gunner hazard from the exhaust plume of motors. The safety requirements lead to the design of separation device and safety igniter device. The dynamic firing test for the designed two devices should be conducted under the flight environmental conditions to verify the requirements compliance. In this study the technique for dynamic firing test of propulsion system of personal surface to air missile is proposed and the method to design the dynamic test bench is also studied.

• Structural Engineering and Mechanics
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• v.23 no.5
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• pp.455-468
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• 2006

Smart structural systems are defined as ones that demonstrate the ability to modify their characteristics and/or properties in order to respond favorably to unexpected severe loading conditions. The performance of such a task requires a set of additional components to be integrated within such systems. These components belong to three major categories, sensors, processors and actuators. It is wellknown that all structural systems entail some level of uncertainty, because of their extremely complex nature, lack of complete information, simplifications and modeling. Similarly, sensors, processors and actuators are expected to reflect a similar uncertain behavior. As it is imperative to be able to evaluate the impact of such components on the behavior of the system, it is as important to ensure, or at least evaluate, the reliability of such components. In this paper, a system model for reliability assessment of smart structural systems is outlined. The presented model is considered a necessary first step in the development of a reliability assessment algorithm for smart structural systems. The system model outlines the basic components of the system, in addition to, performance functions and inter-relations among individual components. A fault tree model is developed in order to aggregate the individual underlying component reliabilities into an overall system reliability measure. Identification of appropriate limit states for all underlying components are beyond the scope of this paper. However, it is the objective of this paper to set up the necessary framework for identifying such limit states. A sample model for a three-story single bay smart rigid frame, is developed in order to demonstrate the proposed framework.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.397-400
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• 2006

Most of the civil structures in Korea and abroad have many kinds of damages when they are facing over-loaded traffics, long-term serviceability, and severe environmental conditions. Repair, rehabilitation, and retrofit are important for maintaining the serviceability of structures. In recent year, VES-LMC has been widely used as repair material for bridge deck repair and rehabilitation, because the VES-LMC has a various benefits such as traffic opening after 3 hours of curing, higher durability and bond strength. In case of any structure repaired or rehabilitated with VES-LMC, those were influenced capacity of bond between the base layer of slab and VES-LMC as well as physical properties of each other materials. The capacity of bond depended on purity of interface, micro cracks, curing of VES-LMC and so like. A kind of popular concrete repair technique, High pressure water jetting equipment is extremely efficient at removing damaged concrete. Removing damaged or poor quality concrete from sensitive structures such as bridge, tunnels, multi-story car parking decks and runways, using the high pressure water jetting could remove damaged or poor quality concrete remaining healthy and sound concrete. Accordingly, the purpose of this study is that it was to evaluate effect of hydrodemolition on the bond strength of VES-LMC overlay compared with effects of other method such as breaker, untreated. Also, it was evaluated the effect of surface moisture.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.881-892
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• 2017

Design and management of concrete slabs in concrete-faced rock-fill dams are crucial issues for stability and overall dam safety since cracks in the concrete face induced by stress, shrinkage, and deterioration can cause severe leakage from the reservoir into the dam. Especially, the increase of dam height to a certain level to enhance the storage capacity and to improve hydraulic stability can lead to undesirable deformation behavior and stress distribution in the existing dam body and in the concrete slabs. In such conditions, simulation of a concrete slab with a numerical method should involve the use of an interface element because the behavior of the concrete slab does not follow the behavior of the dam body when the dam body settles due to the increase of dam height. However, the interfacial properties between the dam body and the concrete slab have yet to be clearly defined. In this study, construction sequence of a 125 m high CFRD in South Korea is simulated with commercial FDM software. The proper interfacial properties of the concrete slab are estimated based on a comparison to monitored vertical displacement history obtained from the concrete slab. Possibility of shear strength failure under the critical condition is investigated based on the simplified model. Results present the significance of the interfacial properties of the concrete slab.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.52-58
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• 2019

Marine emissions of Volatile Organic Compounds (VOCs) have received much attention because the International Maritime Organization (IMO) requires the installation of vapour emission control systems for the loading of crude oils or petroleum products onto ships. It was recently recognised that significant corrosion occurs inside these vapour emission control systems, which can cause severe clogging issues. In this study, we analysed the chemical composition of drain water sampled from currently operating systems to investigate the primary causes of corrosion in vapour recovery systems. Immersion and electrochemical tests were conducted under simulated conditions with various real drain water samples, and the impact of corrosion on the marine vapour recovery system was carefully investigated. Moreover, corrosion tests on alternative materials were conducted to begin identifying appropriate substitutes. Thermodynamic calculations showed the effects of environmental factors on the production of condensed sulphuric acid from VOC gas. A model of sulphuric acid formation and accumulation by the characteristics of VOC from crude oil and flue gas is suggested.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.569-574
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• 2020

Though the discontinuous Galerkin (DG) method has been developed and applied to shallow water equations mainly in explicit schemes, they have been criticized for the limitation in treatment of bottom friction terms and severe CFL conditions. In this study, an implicit scheme is devised and applied to some representative benchmark problems. The linear triangular elements were employed and the Roe numerical fluxes were adopted for convective fluxes. To preserve TVD property, the slope limiter was employed. As the case studies, the model is applied to the flow around the cylinders and the dam-break flow. Then, the results are compared with the experimental and numerical data of previous studies and good agreements were observed.

• Steel and Composite Structures
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• v.42 no.2
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• pp.151-159
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• 2022

This study discusses a hypothetical method for tracking the propagation damage of Carbon Reinforced Fiber Plastic (CRFP) components underneath vibration fatigue. The High Cycle Fatigue (HCF) behavior of composite materials was generally not as severe as this of admixture alloys. Each fissure initiation in metal alloys may quickly lead to the opposite. The HCF behavior of composite materials is usually an extended state of continuous degradation between resin and fibers. The increase is that any layer-to-layer contact conditions during delamination opening will cause a dynamic complex response, which may be non-linear and dependent on temperature. Usually resulted from major deformations, it could be properly surveyed by a non-contact investigation system. Here, this article discusses the scanning laser application of that vibrometer to track the propagation damage of CRFP components underneath fatigue vibration loading. Thus, the study purpose is to demonstrate that the investigation method can implement systematically a series of hypothetical means and dynamic characteristics. The application of the relaxation method based on numerical simulation in the Artificial Intelligence (AI) Evolved Bat (EB) strategy to reduce the dynamic response is proved by numerical simulation. Thermal imaging cameras are also measurement parts of the chain and provide information in qualitative about the temperature location of the evolution and hot spots of damage.

• Journal of Integrative Natural Science
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• v.16 no.3
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• pp.75-80
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• 2023

Bipolar disorder is a mental illness characterized by extreme mood and behavioral swings, such as highs of euphoria and lows of depression. It is a socially significant disorder in which people with the disorder experience intense mood swings and, for those with severe bipolar disorder, it is even difficult leading a normal life. High stress levels in people with mental illness can lead to neuroendocrine disruption, and it is strongly linked to aging. When the neuroendocrine system becomes vulnerable to these mental illnesses and stress, it is likely to accelerate aging. And it's the epigenetic clock that can measure the extent of this accelerated aging. The Epi clock, a pan tissue clock, measures aging through DNA methylation, and the degree of methylation is modified and changed by environmental conditions in the body. Therefore we wanted to check the changes in the epigenetic age of the patients with bipolar disorder. While we found no significant differences in epigenetic age, we did confirm the possibility that people with bipolar disorder have different methylation than normal people. We also found that the EPIC array data fit better on the Epi clock than on the Horvath clock with age-accelerated data from normal people.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.845-857
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• 2020

The precise estimation of accelerated soil wind erosion that can cause severe economic and environmental impacts still has not been achieved to date. The objectives of this investigation were to verify the applicability of a Wind Erosion Prediction System (WEPS) that expressed the soil loss as mass per area for specific areas of interest on a daily basis for a single event in arable lands. To this end, we selected and evaluated the results published by Hagen in 2004 and the soil depth converted from the mass of soil losses obtained by using the WEPS. Hagen's results obtained from the WEPS model followed the 1 : 1 line between predicted and measured value for soil losses with only less than 2 kg·m-2 whereas the values between the measured and predicted loss did not show any correlation for the given field conditions due to the initial field surface condition although the model provided reasonable estimates of soil loss. Calculated soil depths of the soil loss by wind for both the observed and predicted ones ranged from 0.004 to 3.113 cm·10 a-1 and from 0 to 2.013 cm·10 a-1, respectively. Comparison of the soil depths between the observed and predicted ones did not show any good relationship, and there was no soil loss in the predicted one while slight soil loss was measured in the observed one. Therefore, varying the essential model inputs and factors related to wind speed and soil properties are needed to accurately estimate soil loss for a given field in arable land.

• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.11-18
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• 2007

Slope failure triggered by rainfall produces severe effects on the serviceability and stability of railway, Therefore, slope stability problem is one of the major concerns on the operation of railway. In this study, the rainfall conditions triggering slopes failure adjacent to railroads are investigated and the numerical analysis approach in consideration of infiltration and limit equilibrium method based upon multiple slip surfaces are proposed. The rainfall conditions triggering slope failure are as follow: cumulative rainfall is in the range of 150~500 mm, and duration is from 3 to 24 hours. Base upon the rainfall conditions, infiltration analysis and limit equilibrium method for infinite slope condition are carried out. The depth of infinite slope is assumed as 2 m and the multiple slip surfaces modeled with 16.7 cm interval from the bottom slip surface located at the 2 m depth. The assumed bottom slip surface is the location at which factor of safety is converging. The proposed approach shows more reasonable results than the results from the general codes assuming water table at slope surface. In addition, three dimensional plot of cumulative rainfall, rainfall duration, and factor of safety shows that slope stability analysis in consideration of rainfalll must account for cumulative rainfall (rainfall duration).