• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.9 no.2
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• pp.109-114
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• 1998

Background and Objectives : Aerodynamic investigation is valuable information about the efficiency of the larynx in translating air pressure to acoustic signal. The normal data of the Korean has been reported, but there is no basic data of professional western classical singers who have learned how to control the flow of expiratory air for singing. The purpose of this study was to investigate the normal aerodynamic data of korean professional western classical singers and compare this with that of the Korean Materials and Methods : 50 Korean western classical singers were studied. Expiratory lung pressure combined with measurements of the mean air flow rate, voice frequency and intensity were measured with the aerodynamic test using airway interruption method. These data were compared with normal data of untrained normal adults. Results and Conclusions : The voice frequency and the voice intensity were increased in the western classic singers, but the mean air flow rate and the expiratory air pressure of the classical singers were within the same range of the untrained normal adults. This result means that western classical singers can change the loudness and pitch with a little increased or decreasing the mean air flow and the expiratory air pressure.

• 유체기계공업학회:학술대회논문집
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• 1998.02a
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• pp.128-135
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• 1998

Procedures and results of aerodynamic design of a centrifugal compressor are presented for development of a 40kW class turbogenerator gas turbine. Specification of higher level of total pressure ratio of 4 and total efficiency of $80\%$ requires advanced methods of design and analysis. In the meanline design/analysis, a method with conventional loss modeling and a method with the two-zone model are alternately used for more reliable prediction. In the impeller blade generation, a series of Bezier curve are combined to produce meridional contours and distributions of blade camber angle and blade thickness. Intermediate profiles of blades are repeatedly produced and changed to be finally fixed through quasi-three dimensional Euler flow analysis. Three dimensional compressible turbulent flow analysis is then performed for the impeller to be confirmed in the final step of design. Satisfactory results in the aerodynamic performance are obtained, which assures that there is no need of aerodynamic re-design.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.473-473
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• 2009

There have been many academic researches on the aerodynamic design of wind turbine based on blade element method (BEM) and momentum theory (MT, or actuating disk theory). However, in the real world, the turbine blade design requires many additional constraints more than theoretical analysis. The standard procedure is studied in the present paper to design new blades for the wind turbine system ranged from the small size from 1 to 10 kW. From the experience of full design of a 10 kW blade, the authors tried to set up a standard procedure for the aerodynamic design based on IEC 61400-2. Wind-turbine scale, rotating speed, and geometrical chord/twist distribution at the segmented span positions are calculated with a suitable BEM/MT code, and the geometrical shape of tip and root should be modified after considering various parameters: wing-tip vortex, aerodynamic noise, turbine efficiency, structural safety, convenience of fabrication, and even economic factor likes price, etc. The evaluated data is passed to the next procedure of structural design, but some of them should still be corresponded with each other: the fluid-structure interaction is one of those problems not yet solved, for example. Consequently, the design procedure of small wind-turbine blades is set up for the mass production of commercial products in this research.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.1
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• pp.58-63
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• 2012

In general, a conventional flap on an aircraft wing can reduce the aerodynamic efficiency due to geometric discontinuity. On the other hand, the aerodynamic performance can be improved by using a shape-morphing wing instead of a separate flap. In this research, a new flap morphing mechanism that can change the wing shape smoothly was devised to prevent aerodynamic losses. Moreover, a prototype wing was fabricated to demonstrate the morphing mechanism. A shape memory alloy (SMA) wire actuator was used for the morphing wing. The specific current range was measured to control the SMA actuator. The deflection angles at the trailing edge were also measured while various currents were applied to the SMA actuator. The trailing edge of the wing changed smoothly when the current was applied. Moreover, the deflection angle also increased as the current increased. The maximum frequency level was around 0.1 Hz. The aerodynamic performance of the deformed airfoil by the SMA wire was analyzed by using the commercial program GAMBIT and FLUENT. The results were compared with the results of an undeformed wing. It was demonstrated that the morphing mechanism changes the wing shape smoothly without the extension of the wing skin.

• Particle and aerosol research
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• v.7 no.4
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• pp.123-130
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• 2011

Previous designs of conventional aerodynamic lenses have a limitation of narrow range of focusable particle size, e.g. 30 to 300nm or 3 to 30nm. To enlarge the focusable size range to 30-3000nm, it is necessary to avoid a significant loss of particles larger than 300nm inside the lenses. From numerical simulations on size-resolved particle trajectories, we confirmed that the traveling losses of such large particles could be avoided only when the radial position of particles approaching the orifice lens was near the lens axis. Hence, we designed the lens system consisting of a converging-diverging nozzle and 7 orifices to fulfill the requirement. In particular, the orifices were aligned in a way that their diameters were descending and ascending to the downstream. As a result, 30-2800nm particles can be focused to the particle beam of 0.2mm or less in radius with above 85% transmission efficiency. Even $10{\mu}m$ particles can be focused with 74% of transmission efficiency.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.8 no.2
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• pp.178-184
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• 1997

Vocal nodule due to vocal hyperfunction is one of the representative chronic diseases of vocal folds, and it can be cured by surgical movement, and/or voice therapy. The present study is, focusing on the latter, to compare the acoustic and aerodynamic results of the pretreatment with those of posttreatment, and then to investigate the objective date on the efficiency of the voice therapy for the patients with vocal nodules. 11 females(age : 7-49) and 5 males(age : 8-40), total 16 patients wi vocal nodules treated by voice therapy were participated as subjects. Six measurements and comparisons of pretreatment and posttreatment of the results were performed : litter, shimmer, and noise-to-harmonic ratio as acoustic analyses ; maximum phonation time, mean flow rate, and the subtraction of mean flow rate from maximum flow rate as aerodynamic analyses. As a result, 14 of 16 subjects showed improvement at more than 4 of 6 measurements, and in group data, every measurements of posttreatment was improved significantly than the pretreatment. On the whole, the improvement of aerodynamic aspects was more statistically significant than that of acoustic ones.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.3
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• pp.44-51
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• 2021

PIP is an abbreviation of 'Performance Improvement Package', which is a package that can improve performance by applying some design changes to existing aircraft. Boeing provides PIP applicable to B777-200, and Airbus provides PIP applicable to A350-900 as standard. PIP provided by Boeing and Airbus is a separate task, but it is expected to reduce fuel consumption by reducing drag through aerodynamic improvements. The PIP applied to the A350-900 includes work such as increasing Winglet Height and re-twisting Outboard Wing. This study is to verify the effect of PIP application of the A350-900 aircraft and use it as basic data for economic analysis. The aerodynamic improvement studies and expected effects of the PIP application were examined, and the actual flight data of the PIP-applied and the non-applied aircraft were compared to confirm the PIP application effect. This paper provides empirical results for the aviation industry on the PIP application efficiency as a method of improving fuel efficiency and reducing carbon emission.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.315-323
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• 2016

This paper deals with experimental investigation of active flow control via synthetic jets using an unmanned combat air vehicle (UCAV) planform. Fourteen arrays of synthetic jets, mounted along both leading edges, were fully or partially activated to increase aerodynamic efficiency and reduce pitch-up moment. The measurements were carried out using a six-component external balance, a pressure scanner, and tuft flow visualization. It was observed that aerodynamic efficiency (L/D) and pitching moment were clearly affected by the location of jets. In particular, inboard and outboard actuation could effectively increase L/D. Moreover, inboard actuation showed a reduction in the pitch-up, even more than that generated by the full actuation. These results suggest that inboard actuation not only effectively increases L/D but also reduces the pitch-up using only a few actuators.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.143-149
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• 2016

In this study, a method for the multi-objective optimization of an impeller for a centrifugal compressor using fluid-structure interaction (FSI) and response surface method (RSM) was proposed. Numerical simulation was conducted using ANSYS CFX and Mechanical with various configurations of impeller geometry. Each design parameter was divided into 3 levels. A total of 15 design points were planned using Box-Behnken design, which is one of the design of experiment (DOE) techniques. Response surfaces based on the results of the DOE were used to find the optimal shape of the impeller. Two objective functions, isentropic efficiency and equivalent stress were selected. Each objective function is an important factor of aerodynamic performance and structural safety. The entire process of optimization was conducted using the ANSYS Design Xplorer (DX). The trade-off between the two objectives was analyzed in the light of Pareto-optimal solutions. Through the optimization, the structural safety and aerodynamic performance of the centrifugal compressor were increased.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.21-26
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• 2009

Ice accretion is one of the potential hazards in airplane flight, adversely affecting aircraft aerodynamic. There are two distinct icing analysis that can be simulated. One is predicting the effect of ice on the aerodynamic performance of airfoils when ice geometry is known. The other is simulating ice accretion. This work presents the method of icing accretion analysis. This work presents an Eulerian approach to calculate the droplet collection efficiency on the 2D airfoil. The initial flow solution are obtained the FLUENT and copled with droplet motion in the ambient condition.