• Journal of Advanced Marine Engineering and Technology
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• v.16 no.5
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• pp.85-96
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• 1992

Engine enclosures are widely adopted to reduce the noise emission in various fields of application. The radiated noise, which is due to the vibration of enclosure's outer surface, is composed of two kinds of sound power with different path of propagation. One is the 'structure-borne sound power' which stems from the engine's vibratory force applied to the structure of enclosure through the mounting parts of engine etc., while the other is the 'air-borne sound power' which is originated by the sound power radiated from the engine surface to the inner space of enclosure that should excite the vibration of enclosure from inside. In order to get a most efficient engine enclosure is required a profound consideration upon the above structure-borne and air-borne noise, since the guiding principle of countermeasure for each noise is quite different. The controlling of input vibration and its isolation are major subject for the structure-borne sound power and the specifications of absorbing member and damping panels are the major interests for the air-borne sound power. Hence it seems very efficient to separate the total sound power into two categories with a great accuracy when one think of further reduction of engine noise from the exciting enclosure, however, its separating methods have not been made clear for many years. Then author proposes a new practical separation method of two propagation path's contribution to the total radiation sound power for the enclosure under the engine operating condition.

• Journal of Power Electronics
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• v.16 no.2
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• pp.480-489
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• 2016

A novel hybrid carrier-based pulse width modulation (CBPWM) scheme that combines unipolar and dipolar modulations is proposed for single-phase three-level rectifiers, which are widely applied in railway traction drive systems. The proposed CBPWM method can satisfy the volt-second balancing principle in the complete modulation index region through overmodulation compensation. The modulation scheme features two modulation modes: unipolar and dipolar. The operation range limits of these modulation modes can be modified by changing the separation coefficient. In comparison with the traditional unipolar CBPWM, the proposed hybrid CBPWM scheme can provide advantageous features, such as lower high-order harmonic distortion of the line current and better utilization of switching frequency. The separation coefficient value is optimized to achieve the maximum utilization of these advantages. The experimental results verify the feasibility and effectiveness of the proposed hybrid CBPWM scheme.

• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.130-136
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• 2002

The growing use of aluminum for castings over the past decade has brought with it the increased scrutiny of component properties. One area that has received much attention is the effect of in inclusions - or impurities particles held in the metal - on casting properties. A new method of electromagnetic separation for removal of inclusions in aluminum alloy melts is proposed. The principle is that as the electromagnetic force induced in metal acts on inclusions due to low electric conductivity, they are moved to the direction opposite to electromagnetic force and can be separated and removed from the melt. Experiments were carried out on A356 melt mixed alumina particles and commercial Al alloys of ADC 10 and 12. In the experiment using A356, it was proved that $Al_2O_3$ particles was separated and removed continuously from matrix melt by electromagnetic force. Based on these results, the continuous separation experiment that used ADC 10, 12 was carried and the cleanliness of melt was assessed by the amount of porosity, hydrogen contents, PoDFA and mechanical properties through tensile test. As the results of analyses, the amount of porosity and hydrogen contents decreased without variation of chemical composition in the specimen that passed the electromagnetic continuous separator. In addition, tensile strength and elongation of this specimen increased by $20{\sim}30%$ because of reduction of inclusions.

• Steel and Composite Structures
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• v.39 no.5
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• pp.543-564
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• 2021

In this study free vibration analysis of a cracked Goland composite wing is investigated. The wing is modelled as a cantilevered beam based on Euler- Bernoulli equations. Also, composite material is modelled based on lamina fiber-reinforced. Edge crack is modelled by additional boundary conditions and local flexibility matrix in crack location, Castigliano's theorem and energy release rate formulation. Governing differential equations are extracted by Hamilton's principle. Using the separation of variables method, general solution in the normalized form for bending and torsion deflection is achieved then expressions for the cross-sectional rotation, the bending moment, the shear force and the torsional moment for the cantilevered beam are obtained. The cracked beam is modelled by separation of beam into two interconnected intact beams. Free vibration analysis of the beam is performed by applying boundary conditions at the fixed end, the free end, continuity conditions in the crack location of the beam and dynamic stiffness matrix determinant. Also, the effects of various parameters such as length and location of crack and fiber angle on natural frequencies and mode shapes are studied. Modal analysis results illustrate that natural frequencies and mode shapes are affected by depth and location of edge crack and coupling parameter.

• Journal of Science and Technology Studies
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• v.15 no.1
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• pp.281-325
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• 2015

In this paper, we continue our previous study on the differences, similarities and interfaces between the various models of scientific governance discussed in STS and those in risk governance developed by risk studies. In the previous paper we illuminated that theoretical differences among STS scholars on scientific governance and public participation goes back to the 1970s and 1980s, during which they first laid down the conceptual basis of STS. In this paper we investigate how these divergent positions among STS scholars influenced their evaluations of precautionary principle and the framework of risk analysis (especially the separation between risk assessment and risk management), which are the two main paradigms in the area of risk regulation. By doing that, this paper will show divergent positions of STS scholars on risk analysis and precautionary principle. Further, we will suggest some theoretical and practical interfaces between STS and risk governance models.

• Journal of Venture Innovation
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• v.6 no.3
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• pp.61-72
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• 2023

In December 2020, the Fair Trade Act related to South Korea's separation of industrial capital was amended, and it was announced that the amendments would come into effect one year later, on December 30, 2021. The amendment's content involved breaking the previous principle of separating industrial capital from financial market penetration, allowing for the ownership of shares in general holding companies, small business startup investment companies, and technology business finance specialist companies. While the previous law was based on total issued shares' ownership, there were fluctuations in the subsequent trends of annual establishment and investment counts, as well as strategic investment counts of CVC (Corporate Venture Capital) before and after the law's amendment. CVC and IVC (Independent Venture Capital) are characterized differently based on their investment purposes, fund management types, and investment types. In this regard, the relaxation of the separation of industrial capital law is expected to have a positive impact on the future of the venture investment ecosystem and innovation ecosystem. In this study, we analyze the trends in the establishment count, investment count, and strategic investment count of domestic CVC from 2018, before the law amendment, to May 2023. Using 2021, the year the amended separation of industrial capital law was implemented, as a reference point, we examine changes in the trend. The analysis results indicate a significant increase in domestic CVC in 2021 compared to the previous year, along with an increase in investment counts, strategic investment counts, and the amount of investment in strategic investments. Based on these findings, this study suggests directions for further research related to future domestic CVC investment, strategic investment, and the activation of the venture investment market.

• Proceedings of the KIEE Conference
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• 1979.08a
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• pp.80-82
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• 1979

While the standard linear-quadratic-Gaussian problem has fixed horizons, this paper considers the LQG problem with moving horizons. By the separation principle the solution will be given by the kalman filter with the approaching horizon and the LQ regulator with the receding horizon. Sufficient conditions on weighting matrices are derived under which the filter and regulator are asymptotically stable. It wall be shown that the computation method of the moving-horizon LQG regulators is better than that of the standard LQG regulator. The performance measure between the two optimal controls will be compared. A simulation result is given in order to show the usefulness of the moving-horizon LQG regulator.s

• Journal of Korea Multimedia Society
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• v.15 no.12
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• pp.1442-1448
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• 2012

The problem of Metal Area Segmentation (MAS) in X-ray CT images is a very hard task because of metal artifacts. This research features a practical yet effective method for MAS in X-ray CT images that exploits both projection image and reconstructed image spaces. We employ the Relevant Neighbor Area (RNA) idea [1] originally developed for projection image inpainting in order to create a novel feature in the projection image space that distinctively represents metal and near-metal pixels with opposite signs. In the reconstructed result of the feature image, application of a simple thresholding technique provides accurate segmentation of metal areas due to nice separation of near-metal areas from metal areas in its histogram.

• Journal of Information Technology Services
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• v.12 no.4
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• pp.125-143
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• 2013

This paper intends to explore the social and cultural implications of convergence media, based on Goffman's situational approach. The situational segregation of regions makes us to re-interpret the current private and public spheres and helps us to reveal the principle and structure hidden in the new middle region. An environment of convergence media is nullifying the separation of private and public spheres, while letting a new middle region appear.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.573-579
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• 2004

Electroflotation, which is used as an alternative to sedimentation, is a separation treatment process that uses small bubbles to remove low-density particulates. Making allowances for recent collision efficiency diagram based on trajectory analysis, it is necessary to tailor zeta potential of bubbles that collide with negatively charged particles. In this paper, the study was performed to investigate the effects of magnesium and aluminium ions on zeta potential of bubbles. And, it was studied to find out factors which could affect the positively charged bubbles. Consequently, zeta potential of bubbles increased both with higher concentration of metal ions and in the acidic pH value. And, a probable principle that explained the procedure of charge reversal could be a combined mechanism with both specific adsorption of hydroxylated species and laying down of hydroxide precipitate. It also depended on the metal ion concentration in the solution to display its capacity to control the bubble surface.