• The KSFM Journal of Fluid Machinery
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• v.17 no.4
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• pp.19-29
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• 2014

In addition to the development of micro hydro turbine, the challenge in micro hydro turbine design as sustainable hydro devices is focused on the optimization of turbine runner blade which have decisive effect on the turbine performance to reach higher efficiency. A multi-objective optimization method to optimize the performance of runner blade of propeller turbine for micro turbine has been studied. For the initial design of planar blade cascade, singularity distribution method and the combination of the Bezier curve parametric technology is used. A non-dominated sorting genetic algorithm II(NSGA II) is developed based on the multi-objective optimization design method. The comparision with model test show that the blade charachteristics is optimized by NSGA-II has a good efficiency and load distribution. From model test and scale up calculation, the maximum prototype efficiency of the runner blade reaches as high as 90.87%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1016-1019
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• 2002

This paper deals with a fundamental and classical scattering problem by a finite strip. For the analysis of scattered acoustic field, a “single” integral equation is derived. Firstly, the complexity by considering the effect of the mean flow is alleviated by the introduction of Prandtl-Glauert coordinate and the new dependent variable. Secondly, the difficulty of solving the resultant strongly-coupled integral equations which always appear in this kind of 3-part mixed boundary value problem is solved by observing some good properties of the functions in complex domain and manipulating the equations and variables for the use of those properties. The solution can be obtained asymptotically in terms of gamma function and Whittaker function. One aim of this study is the improvement of methodology for the research using integral equations. The other is the basic understanding of scattering by a finite strip related to the linear cascade model of rotating fan blades.

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1755-1761
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• 2008

The present study revealed that Lrp, a leucine-responsive regulatory protein, is involved in the regulation of cadBA transcription through activation of $P_{cadBA}$. The influence of Lrp on $P_{cadBA}$ was mediated by CadC, and thereby, CadC was able to compensate for the lack of Lrp in the activation of $P_{cadBA}$. Western blot analyses and EMSA demonstrated that the cellular level of CadC was not significantly affected by Lrp, and that Lrp exerted its effect by directly binding to $P_{cadBA}$. These combined results suggested that CadC and Lrp function cooperatively to activate the $P_{cadBA}$ rather than sequentially in a regulatory cascade.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.439-449
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• 1998

In this paper, error performance of DS-CDMA communication system has been analyzed in a radio channel which is characterized by multi-user interference (MUI). Also, performance improvement has been obtained by both numerical analysis and simulation techniques when 3-element array antenna and co-channel interference (CCI) canceller are employed as a means for overcoming an MUI effect. The MUI was modelled as a gaussian random process. In array antenna scheme we only considered a directivity of antennal. The results show that there is a substantial enhancement in performance by employing an array antenna or a CCI canceller. CCI canceller gives better improvement in performance than the array antenna with D=2.67. Additional improvement can be obtained when the array antenna and the CCI canceller are adopted in cascade form. In this case the error performance approaches that of AWGN environment.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.813-824
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• 2004

The paper studies the effect of neighboring blade rows on flutter characteristics of cascading blades. For this purpose the computation program to calculate the unsteady blade loading based on the un-steady lifting surface theory for contra-rotating annular cascades was formulated and coded. Then a computation program to solve the coupled bending-torsion flutter equation for the contra-rotating annular cascades was also developed. Some results of the flutter analysis are presented. The presence of the neighboring blade row gives rise to significant change in the critical flutter condition when the main acoustic duct mode is of cut-on state.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.391-397
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• 2004

The performance characteristics of partial admission supersonic turbines are analyzed by using the commercial CFD program FLUENT6.0. The governing equations were discretized with Euler implicit method in time and 2nd-order upwind scheme of FVM in space. The k-$\varepsilon$ turbulence model was utilized to describe the turbulent flow field. In order to investigate the nozzle--rotor interactions and the effect of partial admission, the flows in supersonic turbine rotor cascades with a nozzle are computed. Extensive computations of partial admission supersonic turbines provide the shock structures and flow patterns in the nozzle and rotor. It is clearly shown that the nozzle flow is highly affected by the shocks or expansion waves propagated from the rotor leading edge. And the rotor flow is also affected by the shocks or wakes originated from the nozzle.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.1-7
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• 2004

This paper deals with the performance analysis of the impulse turbine for a owe type wave energy conversion device. Numerical analysis was performed using the commercially-available software FLUENT. This parametric study includes variation of the setting angle of the guide vane. Since parametric study at various flow coefficients requires a tremendous amount of computing time, two-dimensional cascade flow approximation was employed to determine the optimum principal particulars in a rather simple manner. A Full three-dimensional calculation was also performed for several cases to confirm the validity of the two-dimensional approach. Results were compared to other experimental data, such as Setoguchi et al. (2001)'s extensive set of data, and found that the usefulness of 2-D analysis was well demonstrated. The advantages of each method were also evaluated.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.79.1-79.1
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• 2003

Aster scaber T. (Asteraceae) has been used in traditional Korean and Chinese medicine to treat bruises, snakebites, headaches and dizziness. (-) 3,5-Dicaffeoyl-muco-quinic acid (DQ) isolated from Aster scaber induced neurite outgrowth in PC12 cells. It has been reported that the activation of the extracellular signal regulated kinase1/2 (Erk 1/2) and phosphoinositide 3 (P13) kinase plays a crucial role in the NGF-induced differentiation of PC12 cells. This study showed that the effect of DQ on neurite outgrowth is mediated via the Erk 1/2 and PI3 kinase-dependent pathways like NGF. (omitted)

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.1-9
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• 2003

The electromagnectic modal analysis method for the multiscreen structure with periodic slot array with including conductor thickness effect is presented. The multiscreen structure is seen to be exactly equivalent to a microwave guide closed by phase-shift walls. From this viewpoint, the entire generalized scattering matrix of the multiscreen structure is calculated by the cascade connection of the scattering matrices obtained by the modal analysis at guide junctions and the transmission matrices of guide region. The present method is verified in comparison with the results calculated by the previous method of moment for single screen structure. As an application example of the present method, the spatial filter having multiscreen structure is designed and the interesting characteristics such as transmission and reflection coefficient versus frequency & angle are investigated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1074-1083
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• 2006

In the present study, the effect of blade rotation on blade heat transfer is investigated by comparing with the heat transfer results for the stationary blade. The experiments are conducted in a low speed annular cascade with a single stage turbine and the turbine stage is composed of sixteen guide vanes and blades. The chord length and the height of the tested blade are 150 mm and about 125 mm, respectively. The blade has a flat tip and the mean tip clearance is 2.5% of the blade chord. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. For the experiments, the inlet Reynolds number is $Re_c=1.5{\times}10^5$, which results in the blade rotation speed of 255.8 rpm. Blade rotation induces a relative motion between the blade and the shroud as well as a periodic variation of incoming flow. Therefore, different heat/mass transfer patterns are observed on the rotating blade, especially near the tip and on the tip. The relative motion reduces the tip leakage flow through the tip gap, which results in the reduction of the tip heat transfer. However, the effect of the tip leakage flow on the blade surface is increased because the tip leakage vortex is formed closer to the surface than the stationary case. The overall heat/mass transfer on the shroud is not affected much by the blade rotation.