• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.301-304
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• 2002

Powertrain simulation is important fur the analysis of a vehicle performance. Automotive powertrain has been considered as the unified system and should be remodeled, whenever a powertrain system is changed. In this study, a new method is proposed for the synthetic modeling for the automotive powertrain. Components are separated from the powertrain system and constructed the matrix through dynamic relationships. The dynamic equation of the total powertrain system can be driven from the combination of each component. In order to combine each component, the superposition method is modified for the powertrain composition.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.439-442
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• 2002

Powertrain simulation is important far the analysis of a vehicle performance. Automotive powertrain has been considered as the unified system and should be remodeled, whenever a powertrain system is changed. In this study, a new method is proposed far the synthetic modeling for the automotive powertrain. Components are separated from the powertrain system and constructed the matrix through dynamic relationships. The dynamic equation of the total powertrain system can be driven from the combination of each component. In order to combine each component, the superposition method is modified for the powertrain composition.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2946-2951
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• 2008

Combustion instability is a major issue in design of gas turbine combustors for efficient operation with low emissions. Combustion instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to develop a technique to predict self-excited combustion instability of gas turbine combustors, a new stability analysis method based on the transfer matrix method is developed. The method views the combustion system as a one-dimensional acoustic system with a side branch and describes the heat source as the input to the system. This approach makes it possible to use the advantages of not only the transfer matrix method but also well-established classic control theories. The approach is applied to a simple gas turbine combustion system to demonstrate the validity and effectiveness of the approach.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.10
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• pp.475-479
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• 2005

Nowadays large-scale blackout was occurred in many developed countries. The do-regulation and competition in power industry might have an effort on the disaster. The demand response algorithm for protecting it is needed, and developed introducing the concept of transient stability by nonlinear transition matrix. Two case studies are carried out.

• Proceedings of the KIEE Conference
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• summer
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• pp.150-152
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• 2004

Nowadays large-scale blackout was occurred in many developed countries. The dereguration and competition in power industry might have an effort on the disaster The demand response algorithm for protecting it is needed. and developed introducing the concept of transient stability by nonlinear transition matrix Two case studies are carried out.

• Applied Microscopy
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• v.45 no.3
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• pp.177-182
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• 2015

The boiler tubes of X20CrMoV12.1 used in fossil-fired power plants were obtained and analyzed for the effect of water treatment on the steam corrosion-induced oxide scale in an effort to better understand the oxide formation mechanism, as well as pertinent method of maintenance and lifetime extension. The specimens were analyzed using various microscopy and microanalysis techniques, with focuses on the effect of water treatment on the characters of scale. X-ray diffraction analysis showed that the scales of specimens were composed of hematite ($Fe_2O_3$), magnetite ($Fe_3O_4$), and chromite ($FeCr_2O_4$). Electron backscatter diffraction analysis showed that the oxides were present in the following order on the matrix: outer $Fe_2O_3$, intermediate $Fe_3O_4$, and inner $FeCr_2O_4$. After all volatile treatment or oxygenated treatment, a dense protective $Fe_2O_3$ layer was formed on the $Fe_3O_4$ layer of the specimen, retarding further progression of corrosion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1149-1158
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• 2002

An improved hydrostatic unit(HSU) model is proposed by considering the flow loss in order to analyze the power flow characteristics of a hydromechanical transmission(HMT) and a network analysis algorithm is presented to determine the torque and speed of each element of the HMT. To calculate the torque and flow loss of a pump and a motor in HSU, an effort and flow concept is introduced, which can be used to establish a torque and speed matrix in the network analysis. It is found from the network analysis that magnitude of the HSU stroke increases to maintain the same output speed in order to compensate the flow Boss in the HSU and the efficiency of the HMT shows the lowest value in the 1st speed since the HSU has the largest flow loss in the 1st speed and the flow loss decreases as the speed ratio upshifts.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.586-591
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• 2010

Solar cells have been more intensely studied as part of the effort to find alternatives to fossil fuels as power sources. The progression of the first two generations of solar cells has seen a sacrifice of higher efficiency for more economic use of materials. The use of a single junction makes both these types of cells lose power in two major ways: by the non-absorption of incident light of energy below the band gap; and by the dissipation by heat loss of light energy in excess of the band gap. Therefore, multi junction solar cells have been proposed as a solution to this problem. However, the $1^{st}$ and $2^{nd}$ generation solar cells have efficiency limits because a photon makes just one electron-hole pair. Fabrication of all-silicon tandem cells using an Si quantum dot superlattice structure (QD SLS) is one possible suggestion. In this study, an $SiO_x$ matrix system was investigated and analyzed for potential use as an all-silicon multi-junction solar cell. Si quantum dots with a super lattice structure (Si QD SLS) were prepared by alternating deposition of Si rich oxide (SRO; $SiO_x$ (x = 0.8, 1.12)) and $SiO_2$ layers using RF magnetron co-sputtering and subsequent annealing at temperatures between 800 and $1,100^{\circ}C$ under nitrogen ambient. Annealing temperatures and times affected the formation of Si QDs in the SRO film. Fourier transform infrared spectroscopy (FTIR) spectra and x-ray photoelectron spectroscopy (XPS) revealed that nanocrystalline Si QDs started to precipitate after annealing at $1,100^{\circ}C$ for one hour. Transmission electron microscopy (TEM) images clearly showed SRO/$SiO_2$ SLS and Si QDs formation in each 4, 6, and 8 nm SRO layer after annealing at $1,100^{\circ}C$ for two hours. The systematic investigation of precipitation behavior of Si QDs in $SiO_2$ matrices is presented.

• Journal of Ship and Ocean Technology
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• v.5 no.3
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• pp.1-13
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• 2001

Present-day rules and regulations for the design and construction of ships are almost without exemption of a prescriptive and deterministic nature. Often it is argued that this situation is far from ideal; it does no right to the advances, which have been made during the past decades in engineering tools in marine technology, both in methodology and in computational power. Within IMO this has been realized for some time and has resulted in proposals to use Formal Safety Assessment(FSA) as a tool to improve and to modernize the rule making process. The present paper makes use of elements of the FSA methodology, but instead of working towards generic regulations or requirements, a Risk Assessment Approach, not unlike a 'safety case'; valid for a certain ship or type of ship is worked out. Delft University of Technology investigated the application of safely assessment procedures in ship design, in co-operation with Anthony Veder Shipowners and safety experts from Safely Service Center BV. The ship considered is a semi-pressurized-fully refrigerated LPG carrier. On the basis of the assumption that a major accident occurs, various accident, scenarios were considered and assessed, which would impair the safety of the carrier. In a so-called Risk Matrix, in which accident frequencies versus the consequence of the scenarios are depicted, the calculated risks all appeared lo be in the ALARP('as low as reasonable practicable') region. A number of design alternatives were compared, both on safety merits and cost-effectiveness. The experience gained with this scenario-based approach will be used to establish a set of general requirements for safety assessment techniques in ship design. In the view that assessment results will be most probably presented in a quasi-quantified manner, the requirements are concerned with uniformity of both the safety assessment. These requirements make it possible that valid comparison between various assessment studies can be made. Safety assessment, founded on these requirements, provides a validated and helpful source of data during the coming years, and provides naval architects and engineers with tools experience and data for safety assessment procedures in ship design. However a lot of effort has to be spent in order to make the methods applicable in day-to-day practice.