• Applied Science and Convergence Technology
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• v.23 no.3
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• pp.139-144
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• 2014

GaN deposition equipment and processes for the fabrication of white LEDs (Light Emitting Diode) using MOCVD (Metal Organic Chemical Vapor Deposition) were numerically modeled to analyze the effects of a reactive gas introduction strategy. The source gases, TMGa and $NH_3$, were injected from a shower head at the top of the chamber; the carrier gases, $H_2$ or $N_2$, were introduced using two types of injection structures: vertical and horizontal. Wafers sat on the holder at a radial distance between 100 mm and 150 mm. The non-uniformity of the deposition rates for vertical and horizontal injection were 4.3% and 3.1%, respectively. In the case of using $H_2$ as a carrier gas instead of $N_2$, the uniform deposition zone was increased by 20%.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.6
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• pp.795-802
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• 2022

Korea is showing its appearance as a leading country in the hydrogen economy by establishing policies for revitalizing the hydrogen economy and enacting the 「Hydrogen Economy Promotion and Hydrogen Safety Management Act」 for the first time in the world. In addition, domestic hydrogen facilities are using hydrogen energy safely through world-class safety management compared to overseas advanced countries. However, in order to enhance the safety of the rapidly diversifying hydrogen industry and rapid technology development, such as the introduction of liquefied hydrogen, some institutional improvements are needed. In this regard, this paper intends to analyze the results of safety inspections on 13 representative facilities and prepare safety improvement plans to establish preemptive safety measures.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.253-261
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• 2024

The impact of temperature on electrode reactions in 100 cm² molten carbonate cells operating as Fuel Cells (FC) and Electrolysis Cells (EC) was examined using the Reactant Gas Addition (RA) method across a temperature range of 823 to 973 K. The RA findings revealed that introduction of H₂ and CO₂, reduced the overpotential at Hydrogen Electrode (HE) in both the modes. However, no explicit temperature dependencies were observed. Conversely, adding O₂ and CO₂ to the Oxygen Electrode (OE) displayed considerable temperature dependencies in FC mode which can be attributed to increased gas solubility due to the electrolyte melting at higher temperatures. In EC mode, there was no observed temperature dependence for overpotential. Furthermore, the addition of O₂ led to a decrease in overpotential, while CO₂ addition resulted in an increased overpotential, primarily due to changes in the concentration of O₂ species.

• Analytical Science and Technology
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• v.15 no.1
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• pp.7-14
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• 2002

Laser ablation ion trap mass spectrometry (LAITMS) was developed for the analysis of metal and ceramic samples. For this study, XeCl excimer laser (308 nm) was used for ablating the samples and ITMS was used as a detector. Samples were introduced from outside of a ring electrode and this way of sample introduction was very effective for solid samples when laser ablation was employed. Helium gas was used as a buffer gas, and its effect on sensitivity and some parameters (buffer gas pressure, ion storage time, and cut-off RF voltage) were studied. The optimized conditions were $1{\times}10^{-4}$ Torr of buffer gas pressure, 100 ms of ion storage time and $1150V_{p-p}$ of cut-off RF voltage. From that results, copper (Cu) and molybdenum (Mo) metals were tested with LAITMS and the mass spectra of these pure metals were compared with the natural abundance of isotope ratio. We also examined ceramic samples ($Al_2O_3$, $ZrO_2$) and represented the result of elemental analysis.

• Journal of Energy Engineering
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• v.28 no.4
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• pp.48-60
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• 2019

After the Paris Agreement in 2015, the government has been promoting various policies such as 'Hydrogen-Economy Roadmap(2019)' to supply hydrogen. As part of this, the government announced the goal of building 310 hydrogen refueling stations(HRS) until 2022. To this end, special case standard for the introduction of complex, packaged, and mobile hydrogen refueling stations(MHRS) have been enacted and promulgated. The MHRS has the advantage of being able to supply hydrogen to multiple regions. However, due to the movement and close distance between facilities, it is necessary to secure proper installation standards and operational safety through safety analysis. In this study, the possibility of introduction was investigated by designing a standard model and quantitative risk assessment(QRA). As a result of QRA, personal and social risk were acceptable, and the empirical test direction and implications were derived.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.2
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• pp.123-137
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• 2014

The aviation gas turbine is composed of many expensive and highly precise parts and operated in high pressure and temperature gas. When breakdown or performance deterioration occurs due to the hostile environment and component degradation, it severely influences the aircraft operation. Recently to minimize this problem the third generation of predictive maintenance known as condition based maintenance has been developed. This method not only monitors the engine condition and diagnoses the engine faults but also gives proper maintenance advice. Therefore it can maximize the availability and minimize the maintenance cost. The advanced gas turbine health monitoring method is classified into model based diagnosis (such as observers, parity equations, parameter estimation and Gas Path Analysis (GPA)) and soft computing diagnosis (such as expert system, fuzzy logic, Neural Networks (NNs) and Genetic Algorithms (GA)). The overview shows an introduction, advantages, and disadvantages of each advanced engine health monitoring method. In addition, some practical gas turbine health monitoring application examples using the GPA methods and the artificial intelligent methods including fuzzy logic, NNs and GA developed by the author are presented.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.301-305
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• 2010

Cutting procedures where qualities are determined by various demand factors largely influences shipbuilding productivity. Particularly, defects in cutting shapes and cutting surface results in delay for post shipbuilding stages such as in welding and assemblage lines which could become factors for reduced economic viability of the project. Existing cutting procedures utilize fossil fuels such as propane or ethylene as the main fuel component and these methods applied particularly to ship plate cutting gives relatively slow cutting speed and generates large quantities of harmful and sometimes poisonous polluting fumes of which warrants an urgent need to look for alternative cutting methods. Recent introduction of hydrox gas generated by electrically dissociating water into hydrogen and oxygen components to be utilize as an alternative cutting fuel has resulted not just in visible improvement on cutting quality and speed over the existing methods but it has also been welcomed as an environmentally friendly clean fuel source. This paper has been prepared to serve as the basis for accommodating this environmentally friendly hydrox gas cutting method into actual working environment by observing and recording hydrox gas cutting thermal characteristics.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.71-72
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• 2014

The current paper introduce the flame transfer function calculation results using CFD in order to quantify the heat release fluctuations in a lean premixed gas turbine combustor. Comparisons of the modeled and measured flame shapes were made using the optimized heat transfer conditions.

• Tunnel and Underground Space
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• v.2 no.1
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• pp.123-151
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• 1992

“Norwegian Tunnelling in General" will cover the following subjects : - Short introduction to the geology of Norway - Major considerations in rock installations - Hydropower plants, roads, tunnels, oil and gas storage in rock, drinking water storage, sewage plants, frozen food storage, defence and civil defence projects, including sports arenas and swimming pools, etc.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.65-65
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• 2010