• Journal of the Korean Institute of Gas
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• v.20 no.1
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• pp.29-39
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• 2016

Electrical apparatuses for use in the presence of explosive gas atmospheres have to be special designed to prevent them from igniting the explosive gas. Flameproof design implies that electrical components producing electrical sparks are contained in enclosures and withstand the maximum pressure of internal gas or vapours. In addition, any gaps in the enclosure wall have to designed in such a way that they will not transmit a gas explosion inside the enclosure to an explosive gas or vapours atmosphere outside it. In this study, we explained some of the most important physical mechanism of Maximum Experimental Safe Gap(MESG) that the jet of combustion products ejected through the flame gap to the external surroundings do not have an energy and temperature large enough to initiate an ignition of external gas or vapours. We measured the MESG and maximum explosion pressure of propane and acetylene by the test method and procedure of IEC 60079-20-1:2010.When the minimum MESG is measured, the concentration of propane, acetylene in the air is higher than the stoichiometric point and their explosion pressure is the highest value.

• Journal of the Society of Disaster Information
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• v.16 no.2
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• pp.383-391
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• 2020

Purpose: To identify internal self ignition and ignition caused by external flames in energy storage rooms, and to analyze the difference between ignition due to overheating and ignition caused by external heat sources. Method: membrane melting point measurement, battery external hydrothermal experiment, battery overcharge experiment, comparative analysis of electrode plate during combustion by overcharge and external heat, overcharge combustion characteristics, external hydrothermal fire combustion characteristics, 3.4 (electrode plate comparison) / 3.5 (overcharge) /3.6 (external sequence) analysis experiment. Result: Since the temperature difference was very different depending on the position of the sensor until the fire occurred, it is judged that two temperature sensors per module are not enough to prevent the fire through temperature control in advance. Conclusion: The short circuit acts as an ignition source and ignites the mixed gas, causing a gas explosion. The electrode breaks finely due to the explosion pressure, and the powder-like lithium oxide is sparked like a firecracker by the flame reaction.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.444-452
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• 2000

Dense composites of titanium matrix and Al2O3 matrix with reinforcements of carbon or titanium carbide fibers were successfully fabricated by high-pressure self-combustion sintering method or combustion reacton under 30 MPa of uniaxial pressure with an aid of external heating in vaccum. It was found that the fibers were uniformly distributed in the matrix, and aligned in a phase perpendicular to the pressure axis. As a moel ratio of Ti/C or reaction time increased, the density of Ti-matrix composite increased Micro pores around fibers could be removed by using clean carbon fibers without sizing agent on their surface. The evolution of carbide fibers from carbon fibers was observed. The composition of the various phases around fibers were analyzed.

• Structural Engineering and Mechanics
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• v.49 no.5
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• pp.555-568
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• 2014

In this article, stability of composite conical shells subjected to dynamic external pressure is investigated by numerical and experimental methods. In experimental tests, cross-ply glass woven fabrics were selected for manufacturing of specimens. Hand-layup method was employed for fabricating the glass-epoxy composite shells. A test-setup that includes pressure vessel and data acquisition system was designed. Also, numerical analyses are performed. In these analyses, effect of actual geometrical imperfections of experimental specimens on the numerical results is investigated. For introducing the imperfections to the numerical models, linear eigen-value buckling analyses were employed. The buckling modes are multiplied by very small numbers that are derived from measurement of actual specimens. Finally, results are compared together while a good agreement between results of imperfect numerical analyses and experimental tests is observed.

• Steel and Composite Structures
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• v.19 no.1
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• pp.75-92
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• 2015

In this paper, optimization of cylindrical shells under external pressure to minimize its weight has been studied. Buckling equations are based on standard of ABS underwater vehicles. Dimension and type of circumferential stiffeners, and its distance from each other are assumed as variables of optimization problem. Considering the extent of these variables, genetic algorithms have been used for optimization. To study the effect of hydrostatic pressure on the shell and its fabrication according to the existing standards, geometrical and construction as well as stress and buckling constraints have been used in optimization algorithm and also penalty functions are applied to eliminate weak model. Finally, the best model which has the minimum weight considering the applied pressure has been presented.

• Water for future
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• v.27 no.4
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• pp.155-160
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• 1994

External foces acting on a pipe bend change when a transient pressure wave propagates through the bend. Analytical expressions are derived to compute the changes of these forces when the instantaneous pressure wave passes through the bends. This analysis reveals that these forces depend mainly on static pressure rather than fluid momentum. The analysis also reveals that the change of the vertical component of the force acting on a pipe bend with an angle larger than 90$^{\circ}$ may reverse in direction during the passage of a pressure wave through the bend.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1872-1874
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• 2001

This paper presents an implantable telemetry LC resonance-type pressure sensor to measure the cerebral ventricle pressure. The sensor consists of an inductor and a capacitor. The LC resonant circuit consists of the sensor and an external antenna coil that are coupled magnetically. The resonance frequency of the circuit decreases as the applied pressure increases the capacitance of the sensor. The sensor is designed in consideration of the biocompatibility and long lifetime for continuous monitoring of the ventricle pressure. The sensor is simple to fabricate and small in comparison with others reported previously. The inductor is fabricated by electroplating and the variable capacitor is constructed with a flexible p+ diaphragm. Also, the deflection of the diaphragm, the variation of the capacitance and the resonance frequency are analyzed and calculated.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2254-2256
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• 2000

This paper presents an implantable telemetry LC resonance-type pressure sensor for the measurement of the ventricle pressure. This sensor consists of a capacitor and an inductor. This resonant circuit is magnetically coupled with an external antenna coil. The resonance frequency of the circuit decreases as the sensor capacitance is increased by the applied pressure. The inductance and the capacitance are 428nH and 0.98${\mu}F$, respectively. The resonance frequency is 245.7MHz when the differential pressure is zero. The sensitivity of the sensor is 9.477kHz/Pa.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.931-937
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• 2008

A high motive pressure thermal vapor compressor(TVC) for a commercial multi-effect desalination(MED) plant is designed to have a high entraining performance and its robustness is also considered in the respect of operating stability at the abrupt change of the operating pressures like the motive and suction steam pressure which can be easily fluctuated by the external disturbance. The TVC having a good entraining performance of more than entrainment ratio 6.0 is designed through the iterative CFD analysis for the various primary nozzle diameter, mixing tube diameter and mixing tube length. And then for a couple of TVC having a similar entrainment ratio, the changes of the entrainment ratio are checked along the motive and suction pressure change. The system stability is diagnosed through the analyzing the changing pattern of the entrainment ratio.

• Journal of Information Technology Services
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• v.10 no.1
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• pp.135-149
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• 2011

In this paper, we propose the high-risk group detection model for patients with high blood pressure using case-based reasoning. The proposed model can be applied for public health maintenance organizations to effectively manage knowledge related to high blood pressure and efficiently allocate limited health care resources. Especially, the focus is on the development of the model that can handle constraints such as managing large volume of data, enabling the automatic learning to adapt to external environmental changes and operating the system on a real-time basis. Using real data collected from local public health centers, the optimal high-risk group detection model was derived incorporating optimal parameter sets. The results of the performance test for the model using test data show that the prediction accuracy of the proposed model is two times better than the natural risk of high blood pressure.