• Journal of The Korean Astronomical Society
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• v.34 no.4
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• pp.293-295
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• 2001

A numerical scheme that incorporates a self-consistent cosmic-ray (CR, hereafter) injection model into the combined gas dynamics and CR diffusion-convection code has been developed. The hydro/CR code can follow in a very cos-effective way the evolution of CR modified shocks by adopting subzone shock-tracking and multi-level Adaptive Mesh Refinement techniques. The injection model is based on interactions of the suprathermal particles with self-generated MHD waves in quasi-parallel shocks. The particle injection is followed numerically by filtering the diffusive flux of suprathermal particles across the shock to upstream region according to a velocity-dependent transparency function, which represents the fraction of leaking suprathermal particles. In the strong shock limit of Mach numbers $\ge$20, significant physical processes such as the injection and acceleration seem to become independent of M, while they are sensitively dependent on M for M < 10. Although some particles injected early in the evolution continue to be accelerated to higher energies, the postshock CR pressure reaches a time asymptotic value due to balance between acceleration and diffusion of the CR particles.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.5
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• pp.72-79
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• 2000

On the other hand, the fiber orientation at the surface and middle layer of the sheet controls the bending stiffness of paperboard. Therefore, a reliable measurement of paper surface fiber orientation gives us a magnificent tool to investigate and predict paper curling and cockling tendency, and provides the necessary information to fine-tune the manufacturing process for optimum quality. Many papers, especially heavily calendered and coated grades, do resist liquid and gas penetration very much, being beyond the measurement range of the traditional instruments or resulting inconveniently long measuring time per sample. The increased surface hardness and use of filler minerals and mechanical pulp make a reliable, non-leaking sample contact to the measurement head a challenge of its own. Paper surface coating causes, as expected, a layer which has completely different permeability characteristics compared to the other layers of the sheet. The latest developments in sensor technologies have made it possible to reliably measure gas flow n well controlled conditions, allowing us to investigate the gas penetration of open structures, such as cigarette paper, tissue or sack paper, and in the low permeability range analyze even fully greaseproof papers, silicon papers, heavily coated papers and boards or even detect defects in barrier coatings! Even nitrogen or helium may be used as the gas, giving us completely new possibilities to rank the products or to find correlation to critical process or converting parameters. All the modern paper machines include many on-line measuring instruments which are used to give the necessary information for automatic process control systems. Hence, the reliability of this information obtained from different sensors is vital for good optimizing and process stability. If any of these on-line sensors do not operate perfectly as planned (having even small measurement error or malfunction), the process control will set the machine to operate away from the optimum, resulting loss of profit or eventual problems in quality or runnability. To assure optimum operation of the paper machines, a novel quality assurance policy for the on-line measurements has been developed, including control procedures utilizing traceable, accredited standards for the best reliability and performance.

• Journal of the Korea Safety Management & Science
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• v.26 no.3
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• pp.51-57
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• 2024

The purpose of this study is to compare and analyze the impact range of explosion damage due to gas leaks at LPG filling stations, focusing on propane and butane, which are components of vehicle LPG. The scenarios were designed based on the explosion incident at an LPG filling station in Gangwon-do, where an actual gas leak accident occurred, resulting in Scenario I and Scenario II. The ALOHA program, developed by the U.S. National Oceanic and Atmospheric Administration (NOAA), was used as the tool to analyze the impact range of the explosion damage for both substances. The results of the study indicated that, under identical conditions, propane had a wider impact range of damage than butane. This is presumed to be due to the greater explosion energy of propane, attributable to its physicochemical properties. Therefore, when preparing for LPG leak accidents, measures for propane need to be prioritized. As safety measures for propane, two suggestions were made to minimize human casualties. First, from a preventive perspective, it is suggested to educate workers about propane. Second, from the perspective of response measures and damage minimization, it is suggested to thoroughly prepare emergency evacuation and rescue plans, evacuation routes, designated shelters, and emergency response teams. This study compares and analyzes the impact range of radiative heat damage based on LPG components. However, hazardous accidents are critically influenced by the type of leaking substance, the form of the leak, and meteorological factors affecting the diffusion pattern of the substance. Therefore, for future research, it is proposed to model various leakage scenarios for the same substance to conduct a comprehensive risk assessment.

• Journal of the Korean Institute of Gas
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• v.17 no.5
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• pp.64-68
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• 2013

Non destructive testing(NDT) methods of electrofusion(EF) joints of thermoplastics pipes are required for fusion joint safety and for the long term reliability of a pipe system. Electrofusion joints, which are joined at the proper fusion process and procedures, may encounter defects due to the difference of ovality between pipes and coupling, improper fusion process or porosity result from electrofusion joining. These defects can cause the failure of pipeline and by extension, they can be caused the limit to expand the use of plastics pipes. This paper studies inspection results using ultrasonic imaging method for damaged polyethylene electrofusion joints. Gas was leaking from 250mm diameter polyethylene electrofusion joints at February 2004 which was electrofused at December 1994 and operation pressure was 2.45kPa. First, surface inspection was conducted and then in order to find the types of defects examination using ultrasonic imaging method was performed. Lack of fusion and inappropriate inserting for polyethylene pipes into electrofusion coupling were found and causes of the gas leak were judged that misalignment and insert defect. Cutting inspection was performed and each inspection results were compared to. Results of ultrasonic imaging method and cutting inspection were the same.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.17-27
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• 2019

In recent years, dangerous materials and gas leak accidents have been frequently occurred. The hazardous materials storage facility accidents are not rapidly controlled when a leak is detected, unlike other chemical plants can be controled. Externally, the human has to approach and respond to the source of leaking directly. As a result, the human and material damage are likely to larger result in the process. The current approach has been passive response after ringing the alarm. In this study, the suggested tracking system of the leak resource is designed system to track the resource actively by utilizing the mobile sensor robot platform, which can be made easily through recent rapid development technology, is verified through prototype system. Thus, a suggested system should pave the way for minimizing the spread and damage of the accident based on the exact site situation of the initial leak and quick and early measures.

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.37-42
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• 2016

The purpose of this paper is to study for the emission gas control of passenger car. The first example, the PCSV never open when operating condition, but it opened by causing malfunction because of trouble. As a result, the purge gas entered into surge tank, a mount of fuel was displayed with excessive supply on tester. Therefore, it certified the bad-condition of the engine when idling by decreasing of fuel injection quantity from engine ECU. The second example, the hose activating a EGR valve didn't supply the vacuum pressure because of assembling the other part. Thus, it knew the bad-condition of engine that the EGR valve would not work normally by leaking with the other port. The third example, as the rear oxygen sensor of two sensor were fault-installing by changing the sensor of other a car it could not detect of oxygen quantity. Finally, it found the phenomenon of abruptly decreasing vehicle speed when braking a car. Therefore, the system including with emission control has to drastically manage by maximizing condition to role decreasing the emission gas.

• Journal of the Korean Institute of Gas
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• v.26 no.1
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• pp.1-6
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• 2022

This paper is a purpose to study and analyze the engine starting failure examples for LPG car. The first example, the researcher verified the phenomenon that didn't supply the fuel because of filter clogging by fine alien substance in the gas valve line when he inspected the emergency cutting valve. The second example, there was no the influence of gas leakage when the solenoid operated at first. But the damage part of solenoid assemblying face wad downed a durability according to running a valve. Eventually, the researcher checked on the phenomenon of engine stopping by no gas feeding in solenoid because of leaking of gas. The third example, the researcher sought that the wiring sheaths of connector fin between EGR 10A fuse and LPG switch verified the burn-out phenomenon due to the bad contacting as tension damage produced the overheating. Therefore, the manager of a car has to do pre-inspection no producing electric failure and he must maintain his car with optimum condition.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.106-108
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• 2005

The instrumented fuel irradiation test at a research reactor is needed to evaluate the performance of the developed nuclear fuel. The fuel elements can be designed to measure the center line temperature of fuel pellets during the irradiation test by using temperature sensor. The thermal sensor was composed of thermocouple and sensor sheath. Micro-laser welding technology was adopted to seal between seal tube and sensor sheath with thickness of 0.15 mm. The soundness of welding area has to be confirmed to prevent fission gas of the fuel from leaking out of the element during the fuel irradiation test. In this study, fundamental data for micro-laser welding technology was proposed to seal temperature sensor sheath of the instrumented fuel element. And, micro-laser welding for dissimilar metals between sensor sheath and seal tube was characterized by investigating welding conditions. Moreover, the micro-laser welding technology is closely related to advanced industry. It is expected that the laser material processing technology will be adopted to various a pplications in the industry.

• Corrosion Science and Technology
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• v.20 no.2
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• pp.69-76
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• 2021

In this work, we have performed a corrosion failure analysis of a leaking tube connected to an upper header of a condensate pre-heater in a heat recovery steam generator. It was revealed that the leakage position in the tube was the location where the materials were easily vulnerable due to tensile residual stresses induced by the material manufacturing process and welding process. In addition to an imbalance in the module induced by temperature difference during operation of the pre-heater, the weight of the modules and thermal fatigue provoked a type of stress of tensile-tensile fatigue on the tube. Thus, the leakage position of the pre-heater was exposed to the tensile stress on the inner surface of the tube facing the gas, which rendered the unstable oxide layer susceptible to corrosion and the formation of pits on the water side. The cracks propagated along with the degraded microstructure in a transgranular cracking mode under fatigue loading and finally resulted in water leakage.

• Journal of the Korean Institute of Gas
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• v.19 no.3
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• pp.49-53
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• 2015

The purpose of this paper is to study and analyze the failure examples for fire by friction on clutch, manual transmission and tire system in a car. In the first example, the driver took the pedal with foot to act the clutch. But the clutch disk did not return from flywheel by leakage of clutch hydraulic line. The heat was produced between clutch disk and flywheel by surface contacting. As a result, it was produced the fire by oil sludge sticked with transmission. In the second example, the transmission system was operated to transfer power of engine by contacting with gear and gear. But, as if the oil of transmission was caused the oil insufficiency because of leaking by crack of transmission case, it found the fact that was produced the fire by deposit material on transmission case. In the third example, when the car's driver continuously pushed an accelerator pedal for escaping from dry pit, the tire took the heat by the friction force between tire and surface of road. As a result, it became the direct cause for the fire. Therefore the driver must manage not to produce the fire with friction parts by heating during running.