• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.151-156
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• 2000

A vibration in a high-speed machine may lead to machinery malfunction and even catastrophic failure. So solving the vibration problem is a fundamental requirement for the stability of the high-speed machine. The flywheel energy storage system using superconducting magnetic bearings is a device to store electrical energy as rotational kinetic energy by motor and to convert it to electrical by generator when necessary. The high-speed rotating flywheel has large amplitude at a critical speed. And it has an unstable behavior by the electric torque at the first stage of the energy generation. In this paper, the stability analysis is performed with an analytical model and equations of motion-which is considered the effect of the electric torque-to identify the stable driving condition and the dynamic behavior.

• International Journal of Reliability and Applications
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• v.1 no.1
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• pp.65-79
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• 2000

This research considers a system which has an ultimate terminal event such as death, critical failure, bankruptcy together with a certain indicative events (temporary malfunction, special treatment, kind of defaults) that frequently occurs before the terminal event comes to the system. Some investigation of a model for the corresponding bivariate data of the system have been done with an explanation of the situation in terms of two continuous variables instead of continuous-discrete variables and some other properties. Also an analysis has been carried out to evaluate the effect of intermediate observation of occurrence of indicative event so that the result can be used for a possible suggestion of an intermediate observing schedule.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.245-253
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• 2004

There has been recent demand for extending the life of age-degraded structures and equipment by such techniques as diagnosis, maintenance, safety assessment, and estimating residual life on iron-making plants and hydraulic, thermal, and nuclear power plants. These techniques take into account comprehensive scenarios that may cause malfunction and structural damage and allow an assessment of risk based on the likely scenarios. In particular the safety assessment and residual life estimation of age-degraded ships and equipment facilities require consideration of various factors such as mechanical and thermal stresses, corrosion, hardness, load variation due to changes of operating condition, crack generation and strength reduction of material by fatigue. In this study, a detail thermal stress analysis, one of useful techniques of safety assessment and maintenance, is performed on a blast furnace by using general FEM code (MSC/NASTRAN).

• Toxicological Research
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• v.17 no.4
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• pp.249-253
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• 2001

Fumonisin B1, a mycotoxin, is thought to induce esophageal cancer in humans and apoptosis in animal cells by inhibiting ceramide synthase. Dumonisin Bl may also generate reactive oxygen species directly or indirectly, leading to DNA damage and lipid peroxidation. In this study, a DNA fragmentation assay, dichlorofluorescein (DCF) analysis, and single cell gel electrophoresis (SCGE) were used to investigate the involvement of cellular free radicals, specifically hydrogen peroxide, in the DNA damaging activity of fumonisin B1. From an in vitro DNA fragmentation assay, E. coli DNA, damage by fumonisin Bl was increased by the addition of superxide dismutase (SOD) and decreased by catalase. SCGE and DCF analysis in vivo showed that the nuclear DNA damage and intracellular free radicals in cultured rat hepatocytes treated with fumonisin B1 were increased with the concentration of fumonisin Bl . DNA damage and free radical generation were inhibited by the addition of catalase. Fumonisin Bl , in the presence of SOD, produces hydrogen peroxide causing oxidative DNA damage and protein malfunction, leading to genotoxicity and cytotoxicity of the toxin.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.9
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• pp.1351-1363
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• 1990

In this paper, a reliable control system structured with dual CPU modules and dual I/O modules is implemented as a means of achieving a highly reliable fault tolerant control system. For this, faults in the system modules are first examined, and a fault detection technique consisting of self diagnostic, comparison process, and exception processing is applied. Self diagnostic is used to locate which components in the modules have been failed, while comparison process is to cmpare control outputs computed by both CPU modules and protect the plant from malfunction by blocking failed control outputsin advance. Finally exception processing is used to determine the faults that are not detected immediately by the self diagnostic and comparison process, e.g. bus error processing when acknowledge signal for data transfer is not activeted in the I/O modules. Also reliability analysis is conducted for the discrete time Markov model with dual structure. It is shown quantitatively that the reliability is improved in the control system with dual structure in comparison with a system with single module structure.

• Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.42-45
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• 2008

Under the non-operating exposure condition in the hot area, the T-50 cockpit temperature is expected over the requirement according to T-50 environmental criteria. So it is necessary to protect the cockpit from the high temperature condition during the non-operating exposure because the high temperature of the cockpit may result in the cockpit equipment malfunction. In this study, the transparency coating is selected as the method for protecting the cockpit from the high temperature exposure and analyzed the effect on the cockpit heat load attenuation. Some kinds of cockpit coating were reviewed and selected and the analysis was performed about the effect before and after coating application under 1% hot day condition based on the T-50 FSD hot soaking test data. The result of analysis show transparency coating is so effective to attenuate the heat load of T-50 cockpit.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.2 s.25
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• pp.5-10
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• 2006

The heavy thermal load to battle tanks can cause electronic components' malfunction and crew to be put out of action. The thermal load is generated from Internal heat sources such as electronic devices installed in the room as well as extremely hot weather. In this study, heat and flow analysis for the cabin room of a battle tank was performed to deal with this thermal problem. This study presented the validation of simulation results in comparison with those of test, the investigation of optimal flow design for effective cooling in cabin room and finally the evaluation of thermal comforts to crew.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.1
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• pp.34-38
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• 2016

Recently, electric propulsion systems are been increasingly used in large cruise ships and merchant vessels. When abnormal electrical conditions occur in the motor of an electric propulsion ship, they can cause serious damage to the motor and propeller shaft. Research on abnormal conditions of propulsion motors used in electric propulsion vessels and electric ships difficult to find. In this study, a mathematical model of the electric propulsion system is proposed to analyze transient phenomena that occur in the case of electric propulsion motor or propeller shaft malfunction. A synchronous motor was used in the MATLAB computer simulation of this study. In the event of electrical malfunction of the electric propulsion motor at rated operation, over current occurs in the condition of 1 phase ground, over torque occurs at 3 and 2 phases ground and over current and torque occur when exciting power fails at rated operation.

• Journal of the Korean Institute of Gas
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• v.24 no.2
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• pp.36-43
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• 2020

Gas system fire extinguishing equipment is a very economically useful facility, but if it is not used for a long period of time after installing the equipment, there is possibility of rupture due to corrosion of containers and operation errors of equipment systems, and this is very dangerous. However, it is impossible to experiment to check whether the equipment is operating normally. If gas is temporarily released into the enclosed space due to rupture and malfunction, it can cause serious human damage due to gas suffocation. In this study, based on the suffocation death accident of gas system fire extinguishing facility, the inflow path of released gas and the possibility of death and time to death were estimated using a 3D scan and FLACS.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.90-95
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• 2012

To prevent similar accidents with the basis of industrial accidents already occurred in industrial plants, it would be possible only after true causes are grasped. Unfortunately, however, most accident investigation carried out with the basis of legal regulation failed to grasp them so that similar accidents have been repeated without cease. This research aimed to find out differences between results from conventional accident investigation and those from human error analysis, and to draw out effective and practical counter-plans against industrial accidents occurred repeatedly in an autoglass manufacturing company. As for analysis, about 110 accident cases that occurred for last 7 years were collected, and by adopting the Comprehensive Human Error Analysis Technique developed by the previous researchers, not direct causes but basic fundamental causes that might induce workers to human errors were sought. In consequence, the result showed that facility factors or environmental factors such as improper layout, mistakes in engineering design, and malfunction of interlock system were authentic major accident causes as opposed to managerial factors such as personal carelessness or failure to wearing personal protective equipments, and/or improper work methods.