• Textile Coloration and Finishing
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• v.32 no.3
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• pp.176-183
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• 2020

In order to study wearable air cushion materials capable of responding to massive impact in high-altitude fall situation, high tenacity woven fabrics were bonded by heat only depending on various type of thermoplastic films and then mechanical properties were measured. Tensile strength, elongation, and 100% modulus measurement results for 4 types of films show that TPU-2 has higher impact resistance and easier expansion than PET-1. After thermal bonding, the combination with the highest tensile strength was a material with a TPU-2 film for nylon and a PET-2 film for PET, so there was a difference by type of fabric. The tear strength of the bonded materials were increased compared to the fabric alone, which shows that durability against damage such as tearing can be obtained through film adhesion. All of the peel strengths exceeded the values required by automobile airbags by about 5 times, and the TPU-2 bonded fabric showed the highest value. The air permeability was 0 L/dm2 /min. For both the film and the bonded material, which means tightness between the fabric and the film through thermal bonding. It is expected to be applied as a wearable air cushion material by achieving a level of mechanical properties similar to or superior to that of automobile airbags through the method of bonding film and fabric by thermal bonding.

• Journal of the Korean Institute of Gas
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• v.14 no.4
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• pp.18-23
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• 2010

After conducting QRA(quantitative risk assessment) for the high pressure urban gas pipelines planned to be installed, RMMs(risk mitigation measures) when the societal risk is outside the acceptable region have been derived in this paper. Also risk reduction rates are calculated for each RMM. As a result of QRA, we find out that damaged distance caused by radiational heat is largely dependent upon the wind velocity and the atmospheric stability. The measure that has the highest risk reduction effect is No. 10 which includes pipeline corrosion monitoring, MOV(motor operated valve) installation and the method to protect pipeline damage caused by third-party mechanical interference, and which shows 75 % of risk reduction effect.

• Nuclear Engineering and Technology
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• v.21 no.1
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• pp.1-11
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• 1989

Numerous losses of decay heat removal capability have occurred at U during stutodwn while its significance to safety is needless to say. A study is carried out as an attempt to assess what could be done to lower the frequency of these events and to mitigate their consequences in the unlikely event that one occurs. The shutdown risk model is developed and analyzed using Event/Fault Tree for the typical pressurized water reactor. The human cognitive reliability (HCR) model, two-stage bayesian approach and staircase function model are used to estimate human reliability, initiating event frequency and offsite power non-recovery probability given loss of offsite power, respectively. The results of this study indicate that the risk of a Pm at shutdown is not much lower than the risk when the plant is operating. By examining the dominant accident sequences obtained, several design deficiencies are identified and it is found that some proposed changes lead to significant reduction in core damage frequency due to loss of cooling events.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.545-550
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• 2012

Steam generator is one of the major components of nuclear power plant and steam generator tubes are the pressure boundary between primary and secondary side, which makes them critical for nuclear safety. As the operating time of nuclear power plant increases, not only damage mechanisms but also scaled deposits on steam generator tubes are known to be problematic causing tube support flow hole blockage and heat fouling. The ability to assess the extent and location of scaled deposits on tubes became essential for management and maintenance of steam generator and eddy current bobbin data can be utilized to measure thickness of scale on tubes. In this paper, tube reference standards with various thickness of scaled deposit has been set up to provide information about the overall deposit condition of steam generator tubes, providing essential tool for steam generator management and maintenance to predict and prevent future damages. Also, methodology to automatically measure scale thickness on tubes has been developed and applied to field data to estimate overall scale amount.

• Fire Science and Engineering
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• v.32 no.3
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• pp.8-13
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• 2018

It was conceived from the realization that there was a lack of studies on the fire risk compared to utility and importance of plastic which is widely used. In this study, the fire hazard of five types of plastic products was measured by Cone Calorimeter (ISO 5660-1). As a result, the time to ignition (TTI) of polyvinyl Chloride (PVC) plate delayed TTI (196 s), and polystyrene (PS) plate had the shortest TTI of 19 s. The total heat release (THR) of PS plate was measured at 213.07 % higher than the lowest measured PVC plate. Also, the PS plate will have 1.45 to 4.21 times higher $CO_2$ than other plastics, resulting in the highest incomplete combustion and the greatest possible damage of life. Thus, assessing the risk of fire revealed that PS plate is the most dangerous and PVC is the safest.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.115-121
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• 2008

A core engine for pre-cooled turbojet engines is designed and its component performances are examined both by CFD analyses and experiments. The engine is designed for a flight demonstration of precooled turbojet engine cycle. The engine uses gas hydrogen as fuel. The external boundary including measurement devices is set within $23cm{\times}23cm$ of rectangular cross section, in order to install the engine downstream of the air intake. The rotation speed is 80000 rpm at design point. Mixed flow compressor is selected to attain high pressure ratio and small diameter by single stage. Reverse type main combustor is selected to reduce the engine diameter and the rotating shaft length. The temperature at main combustor is determined by the temperature limit of non-cooled turbine. High loading turbine is designed to attain high pressure ratio by single stage. The firing test of the core engine is conducted using components of small pre-cooled turbojet engine. Gas hydrogen is injected into the main burner and hot gas is generated to drive the turbine. Air flow rate of the compressor can be modulated by a variable geometry exhaust nozzle, which is connected downstream of the core engine. As a result, 75% rotation speed is attained without hazardous vibration and heat damage. Aerodynamic performances of both compressor and turbine are obtained and evaluated independently.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.23-27
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• 2011

Due to the rapid development of construction technology with effective land utilization in this nation, many tunnels were and are being built across the country. However, the smoke and the heat generated from tunnel fire are the most important critical factors which may results in both massive personal injury and property damage, especially, due to the closed surrounding of the tunnel. Considering this particular nature of the tunnels, this study aims to install a fire detection system using an optic fiber cable to measure the temperature changes, compare, and analyze the resulted values with the times of temperature changes of the sensor by performing fire simulations under the same condition as a real fire test. From the results, it has been found that the temperature sensor detects a fire occurrence and generates an alarm within one minute after ignition for both a real fire test and a fire simulation alike, and also that the characteristics of temperature changes of the sensor has close relations with the speeds of the currents inside the tunnel. In addition, considering the tunnel fires can affect the evacuation efficiency and the fire extinguishing activities of the fire brigade inside the tunnel, the temperature sensor must be able to search and find the locations and directions of the fires correctly.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.15-21
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• 2019

A rack-type warehouse has the advantage of storing a large amount in a small area by loading goods vertically. But in terms of fire risk, the fire load is very high, which can cause massive damage in the event of a fire. In the United States, research has been actively conducted to minimize the spread of vertical fires, and relevant standards have been established and operated. In Korea, research and related standards are insufficient to prevent the vertical spread of rack-type warehouse fires. In this study, an experimental study was conducted to prevent the vertical spread of a rack-type warehouse fire using a horizontal barrier and in-rack sprinklers. As a result of the test, the horizontal barrier considering the continuous flame prevented the vertical spread of the flame for a certain time. However, the horizontal barrier with continuous flame did not show the effect of preventing continuous flame. The combination of the horizontal barrier and the in-rack sprinkler prevented the vertical spread of fire effectively. In addition, the heat collecting effect through the horizontal barrier was shown and helped the early operation of the in-rack sprinklers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.1-10
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• 2021

Recently, the repair and recycling of damaged mechanical parts via metal additive manufacturing processes have been industrial points of interest. This is because the repair and recycling of damaged mechanical parts can reduce energy and resource consumption. The directed energy deposition(DED) process has various advantages such as the possibility of selective deposition, large building space, and a small heat-affected zone. Hence, it is a suitable process for repairing damaged mechanical parts. The shaft is a core component of various mechanical systems. Although there is a high demand for the repair of the shaft, it is difficult to repair with traditional welding processes because of the thermal deformation problem. The objective of this study is to propose a repair procedure for a damaged shaft using the DED process and discuss its applications. Three types of cases, including a small shaft with a damaged surface, a medium-size shaft with a worn bearing joint, and a large shaft with serious damage, were repaired using the proposed procedure. The microstructure and hardness were examined to discuss the characteristics of the repaired component. The efficiency of the repair of the damaged shaft is also discussed.

• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1785-1791
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• 2021

Natural and environmental disasters are recently increasing in frequency and complexity worldwide due to the rapid expansion of overpopulation, industrialization, and urbanization. Thus, analyzing past critical events/disasters in deep and preparing for future disasters in terms of risk identification, assessment and management are imperative requirements. In this special issue, we introduce several interesting studies covering disaster risk management and observation technologies for the heat waves, particulate matters, floods, drought, and earthquake using remote sensing and GIS performed by i-SEED (School of Integrated Science for Sustainable Earth & Environmental Disaster at Pukyong National University). We expect that the results of this special issue provide comprehensive information on the risk management and damage prevention of natural and environmental disasters and offer guidance on the application to future disasters to reduce their risks and impacts.