• ETRI Journal
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• v.35 no.5
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• pp.859-868
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• 2013

The active noise control (ANC) technique attenuates acoustic noise in a flexible and effective way. Traditional ANC design aims to minimize the residual noise energy, which is indiscriminative in the frequency domain. However, human hearing perception exhibits selective sensitivity for different frequency ranges. In this paper, we aim to improve the noise attenuation performance in perceptual perspective by incorporating noise weighting into ANC design. We also introduce psychoacoustic analysis to evaluate the sound quality of the residual noise by using a predictive pleasantness model, which combines four psychoacoustic parameters: loudness, sharpness, roughness, and tonality. Simulations on synthetic random noise and realistic noise show that our method improves the sound quality and that ITU-R 468 noise weighting even performs better than A-weighting.

• Structural Engineering and Mechanics
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• v.48 no.6
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• pp.791-807
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• 2013

Ultra High Performance Cementitious Composites with compressive strength 200MPa (UHPCC-200) is proposed for the structural design of super high hybrid wind turbine tower to gain durability, ductility and high strength design objectives. The minimal wall thickness is analyzed using basic bending and compression theory and is modified by a toque influence coefficient. Two cases of wall thickness combination of middle and bottom segment including varied ratio and constant ratio are considered within typical wall thickness dimension. Using nonlinear finite element analysis, the effects of wall thickness combinations with varied and constant ratio and prestress on the structural stress and lateral displacement are calculated and analyzed. The design limitation of the segmental wall thickness combinations is recommended.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.17-31
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• 2015

An experimental program was performed to study the effects of cement stabilization on the geotechnical characteristics of sandy soils. Stabilizing agent included lime Portland cement, and was added in percentages of 2.5, 5 and 7.5% by dry weight of the soils. An analysis of the mechanical behavior of the soil is performed from the interpretation of results from unconfined compression tests and direct shear tests. Cylindrical and cube samples were prepared at optimum moisture content and maximum dry unit weight for unconfined compression and direct shear tests, respectively. Samples were cured for 7, 14 and 28 days after which they were tested. Based on the experimental investigations, the utilization of cemented specimens increased strength parameters, reduced displacement at failure, and changed soil behavior to a noticeable brittle behavior.

• Steel and Composite Structures
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• v.13 no.1
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• pp.1-13
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• 2012

In this study, a new structural bracing system named 'Hat Knee Bracing' (HKB) is presented. In this structural system, a special form of diagonal braces, which is connected to the knee elements instead of beam-column joints, is investigated. The diagonal elements provide lateral stiffness during moderate earthquakes. However the knee elements, which is a fuse-like component, is designed to have one plastic joint in the knee elements for dissipation of the energy caused by strong earthquake. First, a suitable shape for brace and knee elements is proposed through elastic studying of the system and several practical parameters are established. Afterward, by developing applicable and highly accurate models in Drain-2DX, the inelastic behavior of the system is carefully considered. In addition, with inelastic study of the new bracing system and comparison with the prevalent Knee Bracing Frame system (KBF model) in nonlinear static and dynamic analysis, the seismic behavior of the new bracing system is reasonably evaluated.

• Journal of The Korean Astronomical Society
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• v.38 no.1
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• pp.7-12
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• 2005

The frequency distribution of HII regions radii in our galaxy has been investigated. The correlation between the number of these regions and their radii has been re-determined, and could be represented by an exponential function. The size distribution of the HII regions in 10 spiral galaxies has been derived and combined with that of our galaxy to derive the distances of these galaxies. It has been found that the distances derived are in a good agreement with the published ones. The interstellar extinction in the galaxies has no influence on the distance estimate when using this geometrical method.

• Natural Product Sciences
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• v.12 no.2
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• pp.74-78
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• 2006

Two specimens of sponges collected from Red Sea, Egypt, were investigated for their contents of secondary metabolites. The crude extracts of the sponges were tested for their anti-inflammatory and analgesic effects. The toxic effects of the extracts of the two marine sponges were studied. $LD_{50}$ determination revealed that the investigated extracts of 'Igernella and Ircinia spp' were 4.69 and 134.7 mg/l00 g b.wt., respectively, when injected intraperitoneally in mice. The toxic signs were recorded within the first 24 hrs after injection. Also the two marine sponges extracts showed significant anti-inflammatory and analgesic effects.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.39-42
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• 2012

The use of Smiles rearrangement in Ugi-type couplings with tropolone allows very straightforward multicomponent formation of 2-(N,N-dialkylamino)-2,4,6-cycloheptatrien-1-one derivatives. The Ugi four-component reaction of isocyanides with tropolone (2-hydroxy-2,4,6-cycloheptatrien-1-one), primary amines and aldehydes proceeds smoothly and cleanly under mild conditions to afford 2-(N,N-dialkylamino)-2,4,6-cycloheptatrien-1-one derivatives in fairly good yields.

• Journal of the Korean Chemical Society
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• v.56 no.3
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• pp.316-321
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• 2012

Poly(ethylene glycol) (PEG) has been used as a sustainable, non-volatile, and environmentally friendly reaction solvent for the synthesis of functionalized benzene/biaryl and fluoren-9-one derivatives from activated acetylenes and 1,3-diones at $100^{\circ}C$. No additional solvent and catalyst are required.

• Journal of Information Display
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• v.13 no.4
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• pp.167-177
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• 2012

Cold cathode fluorescent lamps (CCFLs) are used to provide lighting for liquid crystal displays (LCDs). This paper presents a set of guidelines for measurement characterization and design to reduce the power consumption of CCFL LCD backlight inverters and panel electronics. The proposed methods aim to reduce the backlight power consumption by fine-tuning a back-light inverter for a specific LCD, using several methods. First, the authors describe their power measurement methodology; and next, they identify different areas for tuning a backlight inverter for a given display. The experiment results showed that power savings can range from 50 to 200mW if the backlight inverter is properly tuned. This paper also proposes an optimized configuration for light-emitting device (LED) panels to reduce power loss by selecting a LED with a specific input voltage and number of cells to help minimize power loss.

• Journal of Power Electronics
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• v.13 no.6
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• pp.919-927
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• 2013

This paper proposes a Boundary Current Mode (BCM) control scheme to realize soft switching on a conventional single phase full bridge DC/AC inverter. This technique with the advantages of no auxiliary components, low cost, high efficiency, and simple in control, is attractive for micro-inverter applications. The operation principle and characteristic waveforms of the proposed soft switching technique are analyzed in theory. A digital controller is provided based on that theory. To balance the requirements of efficiency, switching frequency, and inductor size, the design considerations are discussed in detail to guide in BCM inverter construction. A 150W prototype is built under these guidelines to implement the BCM control scheme. Simulation and experiment results demonstrate the feasibilities of the proposed soft switching technique.