• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.4
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• pp.231-236
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• 2011

When the Fukushima nuclear power plant accident occurred in March of 2011, a hydrogen explosion in the reactor building at the 4th unit of Fukushima plants led to a big surprise because the full core of the unit 4 reactor had been moved and stored underwater at the spent nuclear fuel storage pool for periodic maintenance. It was because the possible criticality in the fuel storage pool by coolant loss may yield more severe situation than the similar accident happened inside the reactor vessel. Fortunately, it was assured to be evitable to an anxious situation by a look of water filled in the storage pool later. In the paper, the safety state of the spent fuel storage pool and rack structures of the domestic nuclear plants would be roughly reviewed and compared with the Fukushima plant case by engineering viewpoint of potential severe accidents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.939-949
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• 2017

Prognostics and health management(PHM) is actively utilized by industry as an essential technology focusing on accurately monitoring the health state of a system and predicting the remaining useful life(RUL). An effective PHM is expected to reduce maintenance costs as well as improve safety of system by preventing failure in advance. With these advantages, PHM can be applied to the battery system which is a core element to provide electricity for devices with mobility, since battery faults could lead to operational downtime, performance degradation, and even catastrophic loss of human life by unexpected explosion due to non-linear characteristics of battery. In this paper we mainly review a recent progress on various models for predicting RUL of battery with high accuracy satisfying the given confidence interval level. Moreover, performance evaluation metrics for battery prognostics are presented in detail to show the strength of these metrics compared to the traditional ones used in the existing forecasting applications.

• Journal of Hydrogen and New Energy
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• v.27 no.6
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• pp.764-772
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• 2016

This paper presents on the evaluation of numerical analysis model of a ball valve used for a gas pipeline. The ball valve has important role to control the gas flow of the pipeline as well as safety operation to prevent gas explosion at the emergency. For the validation of numerical simulation, the computational domains are introduced three different types: a hexahedron chamber connected to a pipeline outlet without considering the geometry of pressure tubes, a pipeline only considered the geometry of pressure tubes, and a pipeline connected both of the a hexahedron chamber and pressure tubes. The commercial code, SC/Tetra, is introduced to solve the three-dimensional steady-state Reynolds-averaged Navier-Stokes analysis in the present study. The valve flow coefficient and valve loss coefficient with respect to the valve opening rate of 30%, 50%, and 70% are compared with experimental results. Throughout the numerical analysis for the three analysis domains, pressure computed along the pipeline is affected by computational domains. It is noted pressure obtained by the computational model considering both of the a hexahedron chamber and pressure tubes has a relatively good agreement to the experimental data.

• Convergence Security Journal
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• v.15 no.5
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• pp.61-70
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• 2015

North Korea invaded South Korea on June 25, 1950 and the armistice agreement was reached on July 27, 1953. After that, there have been about 5,000 provocations large and small. In particular, North Korea attacked a naval vessel called "Cheonanham" on March 26, 2010. After the attack, Korean government announced the sanctions against North Korea, so called "May 24 sanctions". North Korea bombarded Yeonpyeong provocation on November 23, 2010 and they planted wood box mines in the DMZ on August 4, 2015. The explosion of them resulted in injuring two Korean soldiers. In response to this accident, Korean government resumed loudspeaker broadcasting against North Korea in 11 years which had developed as the psychological warfare. After this, North Korea declared "being a state of war" and intensified tension. Suddenly North Korea suggested talks and two countries reached an agreement through inter-Korean high-level contacts. But we should review whether the agreement was reached with ease and in haste. This paper focuses on the North Korea's negotiating tactics and suggests our corresponding directions for the future.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.98-103
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• 2015

Liquefied petroleum gas can be charged up to 85% of cylinder volume by enforcement regulations of safety control and business of liquefied petroleum gas act. The charged mass by enforcement regulations is considered by liquid expansion of internal liquefied petroleum gas at $65^{\circ}C$. But the temperature of liquid would not be suspended under $65^{\circ}C$ in a cylinder or portable vessel at certain situation. In the thermodynamics view point, the cylinder can be exposed to high pressure by liquid expansion. Consequently, it can be possible to potential risk such as physical explosion. Hence, this paper will offer a method of estimated internal pressure by liquid expansion at critical state in the closed system. Also, the structural factor which is given rise to volume increasement of cylinder is offered by experiment. This paper is expected as crucial reference for a cylinder design of liquefied petroleum gas.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1147-1154
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• 2022

Now that the development of autonomous driving is progressing, LiDAR has become an indispensable element. However, LiDAR is a device that uses lasers, and laser side effects may occur. One of them is the much-talked-about eye-safety, and developers have been satisfying this through laser characteristics and operation methods. But eye-safety is just one of the problems lasers pose. For example, irradiating a laser with a specific energy level or higher in a dusty environment can cause deterioration of the dust particles, leading to a sudden explosion. For this reason, the dust ignition proof regulations clearly state that "a source with a pulse period of less than 5 seconds is considered a continuous light source, and the average energy does not exceed 5 mJ/mm 2 or 35 mW" [2]. Energy of output optical power is limited by the law. In this way, the manufacturer cannot define the usage environment of the LiDAR, and the development of a LiDAR that can be used in such an environment can increase the ripple effect in terms of use in application fields using the LiDAR. In this paper, we develop a LiDAR with low optical power that can be used in environments where high power lasers can cause problems, evaluate its performance. Also, we discuss and present one of the directions for the development of LiDAR with laser power limited by dust ignition proof regulations.

• Journal of the Korean Society of Safety
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• v.38 no.1
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• pp.70-77
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• 2023

Gas has replaced coal or petroleum as primary fuel because of its convenience. However, gas has risk of fire, explosion, or poisoning. To reduce gas-related accidents, many strategic projects have been being carried based on 'Gas Safety Management Basic Plans' on a domestic scale. In spite of those projects, the gas-related accident rate did not decrease over past decades. Thus, this study was conducted to analyze the effectiveness of ongoing projects, and to find out ways to make improvements. Conventional statistical analyses on accident data published by gas-related institutions were not useful to determine meaningful attributes to predict future. Whereas, accident case analyses adopted in the present study discovered differences in the type of people and their unsafe acts for each gas type. Meanwhile, the overall average priority of projects was not high in the aspect of System Safety Precedence. If the current trend is maintained, with sigmoid functions, it can be estimated that mean annual accident rate will decrease by only 2.0% in the next two decades. To improve the current trend, the present study made conclusions as followings: (1) safety projects should be designed with careful consideration of accident traits including gas type, unsafe acts, and persons involved and (2) alternative strategies should include system considerations such as minimum hazard design and safety devices prior to mere education or training. To summarize briefly, the present state related with gas accidents highlights the necessity of a system-based multidisciplinary approach.

• Korean Journal of Construction Engineering and Management
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• v.24 no.3
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• pp.31-41
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• 2023

This study is a study to develop a configuration management methodology for efficient and systematic management in the event of configuration changes such as deformation, explosion, and remodeling of launch vehicle development test facilities, which are emerging as important national facilities in the era of full-scale space competition. Through the analysis of international standards for configuration management, a configuration management process framework to be applied to launch vehicle development test facilities is extracted, a survey was conducted on experts who performed life cycle engineering of launch vehicle development test facilities, and a configuration management methodology optimized for operation/management of domestic launch vehicle development test facilities was proposed. Identify the configuration for launch vehicle development test facilities, the configuration management manager, configuration management organization, and configuration management board approve/process the configuration changes, and after construction is completed according to design requirements, launch vehicle development test facilities try to manage the configuration in a controlled state.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.727-730
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• 2023

The operation of electric automatic windows is used in harsh environments, and the energy density decreases as charging and discharging are repeated, and as soundness deteriorates due to damage to the internal separator, the vehicle's mileage decreases and the charging speed slows down, so about 5 to 10 Batteries that have been used for about a year are classified as waste batteries, and for this reason, as the risk of battery fire and explosion increases, it is essential to diagnose batteries and estimate SOH. Estimation of current battery SOH is a very important content, and it evaluates the state of the battery by measuring the time, temperature, and voltage required while repeatedly charging and discharging the battery. There are disadvantages. In this paper, measurement of discharge capacity (C-rate) using a waste battery of a Tesla car in order to predict SOH estimation of a lithium-ion battery. A Support Vector Machine (SVM), one of the machine models, was applied using the data measured from the waste battery.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.1
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• pp.28-33
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• 2016

Batteries are used for main power engine in the fields such as mobiles, electric vehicles and unmanned submarines, for starter and lamp driver in general automotive, for emergency electric source in ship. These days, lead-acid and the lithium ion batteries are increasingly used in the fields of the secondary battery, and the lead-acid battery has a low price and safety comparatively, The lithium ion battery has a high energy density, excellent output characteristics and long life, whereas it has the risk of explosion by reacting with moisture in the air. But Recently, due to the development of waterproof, fireproof, dustproof technology, lithium batteries are widely used, particularly, because their usages are getting wider enough to be used as a power source for hybrid ship and electric propulsion ship, it is necessary to manage more strictly. Hybrid ship has power supply units connected to the packets to produce more than 500kWh large power source, and therefore, A number of the communication modules and wires need to implement the wire inspection and monitor system(WIIMS) that allows monitoring server to transmit detecting voltage, current and temperature data, which is required for the management of the batteries. This paper implements a low price type wireless inspection and monitoring system(WILIMS) of the lithium ion battery for hybrid vessels using BLE wireless communication modules and power line modem( PLM), which have the advantages of low price, no electric lines compared to serial communication inspection systems(SCIS). There are state of charge(SOC), state of health(SOH) in inspection parts of batteries, and proposed system will be able to prevent safety accidents because it allows us to predict life time and make a preventive maintenance by checking them at regular intervals.