• Journal of the Korean Institute of Gas
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• v.28 no.2
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• pp.47-55
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• 2024

More than 100 liquefied hydrogen tanks are expected to be introduced in Korea by 2030. Since liquefied hydrogen is stored in a vacuum insulation structure tank at -253℃, there is a possibility of a major disaster in which the tank bursts if there is a problem with insulation. Therefore, the law stipulates that PRV should be installed as the last bastion. It is important to note that in the case of liquefied hydrogen, it becomes useless if the pressure drop of the pipe is ignored and the capacity is calculated incorrectly. In CGA S-1.3, the pressure drop rate of the PRV inlet and outlet pipes is set to less than 3% and less than 10%, respectively. However, there is an interdependence between the amount of pressure drop and the flow rate of the pipe, making it impossible to calculate these values at once. Therefore, we developed a simulator that calculates the pressure loss rate of PRV system using MATLAB/Simulink and evaluated the sensitivity of the pressure drop rate to design elements.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.463-467
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• 2014

In this paper, the thermal behaviors of expanded graphite(EG)/erythritol composites with different contents of EG were studied. The surface and structure properties of the composites were determined by using scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD), respectively. The thermal properties were investigated by differential scanning calorimetry (DSC) and thermal conductivity (TC). As experimental results, the thermal conductivity of the composites increased with increasing the EG content. However, the latent heat was somewhat decreased in the presence of EG. We could concluded that EG was highly promising materials for improving the heat transfer enhancement and energy storage capacity of phase change materials (PCMs).

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.6
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• pp.359-368
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• 2017

As the BadUSB is a vulnerability, in which a hacker tampers the firmware area of a USB flash drive. When the BadUSB device is plugged into the USB port of a host system, a malicious code acts automatically. The host system misunderstands the act of the malicious behavior as an normal behaviour for booting the USB device, so it is hard to detect the malicious code. Also, an antivirus software can't detect the tampered firmware because it inspects not the firmware area but the storage area. Because a lot of computer peripherals (such as USB flash drive, keyboard) are connected to host system with the USB protocols, the vulnerability has a negative ripple effect. However, the countermeasure against the vulnerability is not known now. In this paper, we analyze the tampered area of the firmware when a normal USB device is changed to the BadUSB device and propose the countermeasure to verify the integrity of the area when the USB boots. The proposed method consists of two procedures. The first procedure is to verify the integrity of the area which should be fixed even if the firmware is updated. The verification method use hashes, and the target area includes descriptors. The second procedure is to verify the integrity of the changeable area when the firmware is updated. The verification method use code signing, and the target area includes the function area of the firmware. We also propose the update protocol for the proposed structure and verify it to be true through simulation.

• Journal of computational fluids engineering
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• v.10 no.3 s.30
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• pp.9-18
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• 2005

During a hypothetical severe accident in a nuclear power plant (NPP), hydrogen is generated by the active reaction of fuel-cladding and steam in the reactor pressure vessel and released with steam into the containment. In order to mitigate hydrogen hazards possibly occurred in the NPP containment, hydrogen mitigation system (HMS) is usually adopted. The design of the next generation NPP (APR1400) designed in Korea specifies 26 passive autocatalytic recombiners and 10 igniters installed in the containment for the hydrogen mitigation. in this study, the analysis of the hydrogen and steam behavior during a total lose of feed water (TLOFW) accident in the APR1400 containment has been conducted by using the CFD code GASFLOW. During the accident, a huge amount of hot water, steam, and hydrogen is released in the in-containment refueling water storage tank (IRWST). The current design of the APR1400 includes flap-type dampers at the IRWST vents which are operated depending on the pressure difference between inside and outside of the IRWST. it was found that the flaps strongly affects the flow structure of the steam and hydrogen in the containment. The possibilities of a flame acceleration and transition from deflagration to detonation (DDT) were evaluated by using Sigma-Lambda criteria. Numerical results indicate the DDT possibility could be heavily reduced in the IRWST compartment when the flaps are installed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.6
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• pp.381-387
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• 2017

Dehydrogenation from the hydrolysis of a sodium borohydride ($NaBH_4$) solution has been of interest owing to its high theoretical hydrogen storage capacity (10.8 wt.％) and potentially safe operation. An experimental study has been performed on the catalytic reaction rate and pressure drop of a $NaBH_4$ solution over both a single microchannel with a hydraulic diameter of $300{\mu}m$ and a staggered array of micro pin fins in the microchannel with hydraulic diameter of $50{\mu}m$. The catalytic reaction rates and pressure drops were obtained under Reynolds numbers from 1 to 60 and solution concentrations from 5 to 20 wt.％. Moreover, reacting flows were visualized using a high-speed camera with a macro zoom lens. As a result, both the amount of hydrogenation and pressure drop are 2.45 times and 1.5 times larger in a pin fin microchannel array than in a single microchannel, respectively.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.21-26
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• 1997

This paper presents the numerical results of six corrugation models which compute the stress behaviours and stress levels of the membrane structure under the hydrostatic pressure of cryogenic liquids and thermal loadings using a non -linear finite element analysis program. A three-dimensional analysis of various corrugation geometries was performed on the maximum mean normal stress distributions along the upper surface of the membrane sheet. Comparisons of the FEM results for various geometry models of the corrugation are presented, which shows that the corrugated configuration of the ring knot model can be effectively performed for the combined forces such as the hydrostatic pressure and thermal loading in comparison with the Technigaz type corrugation which has small comer and apex curvatures. The FEM results show that the ring knot corrugation can be used for the deepest depth, 180m of the LNG storage tank in comparison with other corrugation models.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.49-55
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• 1997

Destruction phenomena of structure by gas explosion is due to the explosion pressure and heat. Explosion pressure is a kind of energy converted from the gas mixture explosion. In this paper, we tried to find the relationship between explosion characteristics and combustion heat of the hydrocarbon-oxygen mixtures. Experiment were carried out with the volume of $5916cm^3$ cylindrical explosion vessel. Hydrocarbon gases which used in this study were methane, ethylene, propane, and buthane Experimental parameter was the concentration of the gas mixtures. Explosion characteristics were measured with strain type pressure transducer through the digital storage oscilloscope. From the experimental result, it was found that explosion pressure depend upon the combustion heat.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.161-166
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• 2003

In this paper, we propose a novel method of design and implementation for the multimedia monitoring system using Web Camera. Recently WebCam is variously applied to many different areas and implemented as an improved performance using convenient functions of Web in this Internet era. Multimedia moving pictures has been popularly used in a variety of ways in different areas of monitoring systems in order to enhance the performance and the service with their data compression capability and the speed of the communication network these days. The design method of WebCam system presented in this paper might offer not only a convenient function of the monitoring system but great application capabilities. It can be used for a real time application of the multimedia picture and audio transmission so that the monitoring system can manage the security information in the sense for the reality. Tn addition, the monitoring system may be used as an inreal-time application using data storage and retrieval features of the Web. We offer both functions of monitoring in this structured form of implemented system.

• Korean Journal of Food Science and Technology
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• v.22 no.3
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• pp.266-271
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• 1990

Yukwa(Korean traditional puffed rice snack) puffed by vegetable oil was evaluated its shelf-life and monitored its physicochemical changes during long term storage. And air puffing instead of oil was tested for substitution of puffing medium. The shelf-life of oil puffed Yukwa was less than 4 weeks at $30^{\circ}C$ by peroxide value and negligible changes in physical texture was detected after 9 weeks storge. There was a possibility to apply air puffing method for Yukwa making and its optimum temperature was around $250^{\circ}C$. Air puffed Yukwa was a little less expansion rate, same level of hardness and high brittleness compared with oil puffed . Sensory evaluation of air puffed Yukwa was as same as air puffed in odour, firmness and texture but overall taste was less score probably causing by oil used which need a impovement for air puffed Yukwa. No differences in structure of both Yukwa observed by SEM was showed.

• Polymer(Korea)
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• v.39 no.2
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• pp.293-299
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• 2015

Conductive microcellular foams consisted of polystrene (PS) and polydopamine-coated carbon nanotube (PDA-CNT) were prepared via high internal phase emulsion (HIPE) polymerization and their morphology and electrical conductivity were investigated. CNT as a conductive nanofiller was modified to PDA-CNT by coating with hydrophilic PDA on the surface of CNT to increase aqueous phase dispersion and emulsion stability. It was possible to prepare the HIPEs having higher PDA-CNT content and the resultant foams having improved conductivity due to its good dispersion. The foams showed the morphology of interconnected cell structure. As PDA-CNT content increased, yield stress and storage modulus increased and cell size reduced. The PDA-CNT content showing electrical percolation threshold was ca. 0.58 wt% and the conductivity at PDA-CNT content of 5 wt% was increased to $10^{-3}S/m$.