• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.216-224
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• 2009

The endless scaling down of the semiconductor process made the impact of the power network noise on the performance of the state-of-the-art chip a serious design problem. This paper compares the performances of two popular circuit reduction approaches used to improve the efficiency of power network noise analysis: moment matching-based model order reduction (MOR) and node elimination-based MOR. As the benchmarks, we chose PRIMA and R2Power as the matching-based MOR and the node elimination-based MOR. Experimental results indicate that the accuracy, efficiency, and memory requirement of both methods very strongly depend on the structure of the given circuit, i.e., numbers of the nodes and sources, and the number of moments to preserve for PRIMA. PRIMA has higher accuracy in general, while the error of R2Power is also in the acceptable range. On the other hand, PRIMA has the higher efficiency than R2Power, only when the numbers of nodes and sources are small enough. Otherwise, R2Power clearly outperforms PRIMA in efficiency. In the memory requirement, the memory size of PRIMA increases very quickly as the numbers of nodes, sources, and preserved moments increase.

• Journal of Nutrition and Health
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• v.31 no.7
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• pp.1174-1182
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• 1998

The purpose of this study was to compare the nutritional status and the immunocompetence of elderly women residing in urban and rural areas. Dietary food records and anthropometric measurements were used to evaluate the nutritional status of subjects. The immune function of subjects was assessed by total and differential white blood cell(WBC) counts. Total B and T Lymphocytes, and T cell subsets were quantified by flow-cytometer. Immunoglobulin G, A, and M concentrations were also measured as an index of humoral immunity. Elderly women in rural area showed a relatively lower dietary intake of total energy, protein, and iron than did urban elderly women. Total WBC, neutrophil counts, eosinophil counts, and the percentage of neutrophils among total leukocytes were significantly higher in urban elderly women than in rural women. Although the numbers of lymphocytes were not significantly different, the percentage of Lymphocytes among total leukocytes as greater in rural elderly women than in urban. Both groups did not show any significant differences in numbers of T cell subsets and NK cells. Immunoglobulin G, A, and M levels were not significantly different between the two groups, but the numbers of subjects placed under the deficient range of immunoglobulins were greater in rural than in urban elderly women. from the present study, it could be suggested that poor nutritional intake may selectively affect the number of immune cells, thereby influencing the immunocompetence of elderly women. (Korean J Nutrition 31(7) 1174-1182, 1998)

• Smart Structures and Systems
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• v.29 no.5
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• pp.747-755
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• 2022

Hierarchical structure parameters, proposed in She-Leveque model, are investigated for velocity components obtained from different flow types over a large range of Reynolds numbers 255 < Re_𝜆 < 720. The values of intermittency parameter 𝛽, with respect to a fixed velocity component, are observed nearly same for all four types of turbulence. The parameter 𝛾, for streamwise velocity components is nearly the same but significantly different for vertical components in different flows. It is also observed that for both parameters, an obvious relation between the longitudinal and transverse components 𝛽_T < 𝛽_L (and 𝛾_T < 𝛾_L) always holds. However, the difference between 𝛽_L and 𝛽_T is found very small in all types of turbulent flows, we studied here. It is evidenced that at low Reynolds numbers, the deviations from K41 scaling are mainly due to the most intense structures and slightly because of more heterogeneous hierarchy of fluctuation structures. However, at higher Reynolds numbers the deviations seem as a consequence of the most intense structures only. Over all, the study suggests that the hierarchy parameter 𝛽 may be consider as a universal constant.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.3
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• pp.296-303
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• 2016

In this paper, a numerical experiment on a tidal turbine was performed based on a water wheel design using the commercial CFD code ANSYS-CFX to contribute to the development of water wheels. The water wheel type tidal turbine was studied with different numbers of rotor blades (including ten, twelve and twenty blades types) and with different blade shapes (Straight, Curved and Zuppinger types) for comparison at several values of tip speed ratio (TSR) ranging from 0.7 to 1.2. The numerical results indicated that the 10-bladed type and the Straight-bladed type turbines absorb the highest power efficiency, up to 43 % at TSR 0.9. In addition, the 20-bladed and the Curved-bladed types showed the lowest performances in all cases of TSRs comparing with the others. Besides that, it was found that this turbine operates much effectively at low range of TSR, especially at TSRs 0.9 and 1 for all cases of blade shapes and all numbers of blades.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.6 s.237
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• pp.653-661
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• 2005

The present study numerically investigates two-dimensional fluid flow and heat transfer ir the confined jet flow in the presence of applied magnetic field. For the purpose of controlling vortex shedding and heat transfer, numerical simulations to calculate the fluid flow and heat transfer in the confined jet are performed for different Reynolds numbers in the absence and presence of magnetic fields and for different Prandtl numbers of 0.02 (liquid metal), 0.7 (air) and 7 (water) in the range of $0{\le}N{\le}0.05$, where N is the Stuart number (interaction parameter) which is the ratio of electromagnetic force to inertia force. The present study reports the detailed information of flow and thermal quantities in the channel at different Stuart numbers. As the intensity of applied magnetic fields increases, the vortex shedding formed in the channel becomes weaker and the oscillating amplitude of impinging jet decreases. The flow and thermal fields become the steady state if the Stuart number is greater than the critical value. Thus the Nusselt number at the stagnation point representing the heat transfer characteristics also vary as a function of Stuart number.

• Korean Journal of Plant Taxonomy
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• v.41 no.3
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• pp.215-222
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• 2011

Various aneuploidy and polyploidy have been reported in the genus Aconitum L. (ca. 300 species worldwide, Ranunculaceae), and there is a demonstrated association between major lineage diversification and polyploidy. This study reports chromosome counts of eight Aconitum from Korea, including the first counts for A. japonicum Thunb. subsp. napiforme ($H. L{\acute{e}}v.$ & Vaniot) Kadota (2n = 32) and A. longecassidatum Nakai (2n = 16). The study also includes chromosome numbers for two taxa on the Critically Endangered species list in Korea. Among Korean native species, chromosome numbers in Aconitum subgenus Aconitum range from 2n = 16 to 2n = 64 with diverse levels of polyploidy (2x, 4x, and 8x), whereas Aconitum subg. Lycoctonum exhibits only diploids (2n = 16). Greater chromosome number diversity in subg. Aconitum than subg. Lycoctonum might explain higher species diversity within the former subgenus (more than 250 species worldwide). Investigating chromosome number diversity of Aconitum in a phylogenetic framework will be a critical step to understand species richness of the genus.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.903-910
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• 2002

The present study aims to investigate the heat transfer characteristics of a pulsating axisymmetric air jet impinging on a heated wall. An axisymmetric contraction nozzle is used to obtain uniform profiles for the mean velocity and turbulence intensity at the nozzle exit. Measurements of the time averaged temperature on the impingement surface are conducted using a Thermochrornatic Liquid Crystal(TLC) technique for steady and pulsating jets at the jet Reynolds numbers of 20000, 30000 and 40000. Considered are pulsation frequencies of 10 and 20 Hz, corresponding to Strouhal numbers below 0.06 based on nozzle width and jet discharge velocity. In addition, the effect of nozzle-to-plate distances in the range of 2 to 10 on heat transfer characteristics is assessed. The pulsating impinging jet provides more uniform heat transfer coefficient near the impingement region, irrespective of H/D. Based on the measured data, a good correlation as a function of the jet Reynolds and Nusselt numbers is reported. It is also found that an exponent m in the relation of Nu ${\propto}\;Re^m$ depends on both r/D and H/D, by which the impinging jet flows are highly affected.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.561-575
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• 1996

The interaction of turbulent mixed convection and surface radiation in a three-dimensional channel with the heated blocks is analyzed numerically. Two blocks are maintained at high temperature and the other bottom and horizontal walls are insulated. S-4 method is employed to calculate the effect of the radiative heat transfer. The low Reynolds number k-$\varepsilon$ model proposed by Launder and Sharma is used to estimate the turbulent influence on the heat transfer enhancement. From above modeling, the effects of various channel specifications on the flow and heat transfer characteristics are investigated. The variables used for the present study are Reynolds number, block spacing, the channel height spacing for block and the emissivity. Average Nusselt numbers along the block surfaces are correlated and presented in terms of Reynolds number, emissivity and dimensionless geometric parameters. For the range of conditions in this study, average Nusselt numbers along the block surfaces are strongly influenced by the Reynolds numbers and channel height spacing for block but weakly influenced by the block spacing and the emissivity of the adiabatic walls.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.7
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• pp.869-875
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• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9 ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.

• Journal of the Korean Society of Visualization
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• v.10 no.3
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• pp.16-20
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• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.