• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.1-8
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• 2018

The state of registry issues a type certificate validation (TCV) based on the satisfactory evidence that the product (aircraft, engine, and propeller) is in compliance with the appropriate airworthiness requirements. The Korean government performs an evaluation to determine whether the product complies with Korean airworthiness standards for issuing TCV according to the Korean aviation safety law. Recently, the Validation Principles Working Group (VPWG) has developed a risk-based model for validation of civil aeronautical products. Also, VPWG proposed to incorporate this validation model into the corresponding ICAO Standards and Recommended Practices and guidance material. In this paper, we have reviewed the validation model and discussed improvements in the validation process.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.254-257
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• 2008

For crystalline slags, of which the viscosity rapidly increases at $T_{cv}$ due to the formation of crystalline phases, the Tcv is affected by measurement conditions. In this study, we investigated the effect of cooling rate, and alumina dissolution on the determination of $T_{cv}$. Using synthetic slag samples based on the composition of Alaska Usibelli slag, $T_{cv}$ were determined under a constant cooling rate of $2^{\circ}C$/min, and under rapid cooling with holding time to allow the slag to reach thermal and rheological equilibrium. The effect of alumina dissolution was investigated using platinum lined crucibles. The constant cooling resulted in lower $T_{cv}$ by $33^{\circ}C$ as compared to the equilibrium measurements. Under $2^{\circ}C$/min cooling, the blocking alumina dissolution resulted in lower $T_{cv}$ by $23^{\circ}C$. When the $T_{cv}$ was measured under $2^{\circ}C$/min cooling using an alumina crucible, therefore, the effects of a constant cooling is somewhat offset by the alumina dissolution effect, and bring the measured value closer to the true value.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.238-244
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• 2002

A 5-valve(intake 3-valve) engine has been developed to increase engine performance. These engines have a high power caused by the decrease of inertia mass of an intake valve and the increase of intake effective area. In this study, in-cylinder flow patterns were visualized with laser sheet method and velocity profiles at near intake valves were inspected by using a two-color PIV. In addition, steady flow tests were performed to quantify tumble ratio of flow-fields generated by a tumble control valve(TCV). Experimental results of steady flow test show that the cure of tumble ratio in intake 3-valve engine farmed as a S shape with valve lift changes. This tendency is different from the one in intake 2-valve engine. Using laser sheet method and two color PIV method, we can find that the intake flow through upper valve increases and the velocity gradient also slightly increases as valve lift increases. From this study, the in-cylinder flow characteristics around intake valves were made clearly.

• Journal of the Korean association of regional geographers
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• v.10 no.2
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• pp.252-266
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• 2004

This study analyzes the influence of the construction of a high-speed railroad on territorial organization in France. After development of a new transportation network, the French territorial organization has been largely modified. Many economic urban areas are modified by their position in the territorial hierarchy according to their condition of connection with the TGV network. At first, spatial convergence is the most important effect of the TGV network construction. Second, the development of a transportation network concentrated in the Paris area has influence as an intensified factor on metropolitan areas and as a weakening factor on middle- and small-sized cities. Thus, this system has risk in increasing territorial imbalance in France. Third, to implant an economic activity zone around new TGV stations, a new town or a new economic center starts to develop. This is going to grow into a second core outside of the old city center so that regional spatial organization is transformed from a mono-polarized(mono-centric) organization to a multi-polarized(polycentric) one. Lastly, the integration of the EU railroad system enhances the concentration of economic activity in European metropolitan areas as each metropolitan area tries to develop more competitive space for its rising position in the global urban hierarchical system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.68-74
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• 2005

The electrical arc furnace (EAF) classified as a special waste contains many flux components producing melts during a sintering process, so it decreases the sintering temperature and improves the mechanical properties of specimens. Increasing dust content in a clay-dust system brick, however, may cause the fraction defective higher due to the excessive liquid produced. To control the liquid behavior produced during sintering process for the clay-dust system specimens, the $Al_2O_3$ was added and the physical properties were analyzed. The microstructure for the clay-dust system body sintered with $Al_2O_3$ became homogeneous and the overall size of pores decreased. Adding $Al_2O_3$ to clay-dust system body increased the mechanical properties and the temperature of maximum strength increased as much as $50^{\circ}C$, and the apparent density increased and the absorption decreased. The mullite ($3Al_2O_3{\cdot}2SiO_2$) was produced during sintering process by reaction of $Al_2O_3$ and $SiO_2$ which could participate to liquid-producing-process and the viscosity of melts increased which was proved by measuring a critical viscosity temperature (Tcv) therefore, the refractoriness of specimens were improved to lower the fraction defective.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.623-630
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• 2006

The slag viscosity is an important factor determining the operation temperature of entrained flow type of gasifiers. The temperature of critical viscosity, $T_{cv}$, for 5 crystalline slags was predicted by empirical models and FactSage equilibrium calculations, and the validity of each method was tested. Two empirical models were employed: one using $T_h$ from the ash fusion test, and the other using the concentrations of 5 major components. The first model using $T_h$ over-predicted $T_{cv}$ by $20{\sim}100^{\circ}C$, while the model based on the slag composition under-predicted $T_{cv}$ by $80{\sim}120^{\circ}C$. In the equlibrium calculations, $T_{cv}$ was obtained from the liquidus temperature. When the 4-major component concentrations were used in the calculation, the predicted temperatures were higher than the observed. The liquidus temperature was very sensitive to the concentrations of minor components, and the addition of MgO and $Na_2O$ lowered the liquidus temperature. The results with 4 major and 3 minor components most closely described experimentally observed $T_{cv}$. In the case that a chromia refractory was used, it was shown that $Cr_2O_3$ concentration in the slag also needs to be included for more accurate prediction of $T_{cv}$.