• Journal of computational fluids engineering
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• v.21 no.3
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• pp.1-7
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• 2016

In the present study, the homogeneous model is used to simulate the natural convection heat transfer of the CuO-water nanofluid in a concentric annular enclosure. Simulations have been carried while the Rayleigh number ranges from $10^3$ to $10^6$, solid volume fraction ranges from 0.01 to 0.04 and the radius ratio varies between 0.1 and 0.7. Results are presented in the form of streamlines, isotherm patterns and averaged Nusselt numbers for different values of solid volume fraction, radius ratio of the annulus and Rayleigh numbers. The results show that by decreasing the radius ratio and/or increasing the Rayleigh number, the averaged Nusselt number increases. Also the heat transfer rate increases as increased solid volume fractions.

• ALGAE
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• v.32 no.3
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• pp.189-197
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• 2017

To quantify the abundance of the harmful dinoflagellate Cochlodinium polykrikoides in natural seawaters, we developed the innovative procedure using a droplet digital PCR (ddPCR) with C. polykrikoides-specific primers targeting the internal transcription sequence (ITS). The abundance of C. polykrikoides was estimated by the specific copy number of target ITS DNA segments per cell in cultures and natural water samples. The copy number per C. polykrikoides cell as acquired by ddPCR was $157{\pm}16$, which was evaluated against known cell numbers through a simplified protocol preparing DNAs. The abundances of C. polykrikoides in the waters of different locations estimated by ddPCR agreed with the number of cells visually counted under a microscope. This protocol was used to measure the abundance of C. polykrikoides close to and further off the southern coast of Korea in August of 2016 and 2017. The practical application showed that this method can reduce time for analysis and increase accuracy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.528-537
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• 1995

Natural convective flow and heat transfer characteristics in a partially opened enclosure fitted with a horizontal divider are investigated numerically. The enclosure is composed of a lower hot and a upper cold horizontal walls and adiabatic vertical walls. A divider is attached perpendicularly to the vertical insulated wall. The governing equations are solved by using the finite element method with Galerkin method. The computations have been carried out by varying the length of divider, the opening size, and the Rayleigh number based on the temperature difference between two horizontal walls and the enclosure height for air(Pr=0.71). As result, when the opening size is fixed, the intensity of the secondary flow is weaken as the length of divider increases. The maximum heat transfer rate over the upper cold wall occurs at a position bounded on the opening. However, when the length of divider is increased considerably, its maximum occurs at the right wall. The stability and frequency of oscillation are affected by the Rayleigh number and length of divider. The Nusselt number is increased with the increase of the opening size and the increase of Rayleigh number.

• Animal cells and systems
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• v.1 no.4
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• pp.609-617
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• 1997

Polygenic variation of sternopleural bristle number was investigated at the whole chromosome level in a natural population of Drosophila melanogasfer. Fifty pairs of second and third chromosomes were analyzed at $25^\circ{C}$. Since environmental factors such as temperature influence polygenic expression of quantitative traits, whole chromosomal effects of 28 pairs from the larger original sample were measured under cycling temperature, a $10-30\circ{C}$ cycle in 24 hours, to reveal any polygenic alleles whose effects might be masked under the constant temperature. While third chromosomes typically showed a larger contribution to polygenic variation in both environments, second chromosomes showed greater sensitivity to environmental changes. Cluster analyses of second and third chromosomes produced a limited number of clusters. Such a small number of cluster's implies that there may be a small number of genes, or quantitative trait loci (QTLs), having large effects on phenotypic variation. The genetic structure assessed under constant temperature, however, did not show any correlation with the structure under cycling temperature. The discrepancy could be caused by independent response of each polygenic allele to temperature changes. Thus, polygenic structure in natural populations should be thought of as a temporally changing profile of interactions between gene and ever-changing environment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.3
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• pp.147-154
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• 1992

Laminar natural convection heat transfer from a hot body in a square enclosure has been studied for various center positions of a hot square at Grashof number $Gr=1.5{\times}10^5$, Prandtl number Pr=0.71 and dimensionless thermal conductivity $k_g/k_f=14710$. The natural convection at the center position of a hot square; $X_c$, $Y_c=0.5$, 0.2 shows the most strong and at $X_c$, $Y_c=0.5$, 0.7 the most weak. The total mean Nusselt number at $X_c$, $Y_c=0.5$, 0.2 was 7.4% higher than that at $X_c$, $Y_c=0.2$, 0.5. The total mean Nusselt number at $X_c$, $Y_c=0.5$, 0.7 was 5.0% lower than that at $X_c$, $Y_c=0.3$, 0.5.

• Journal of Forest and Environmental Science
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• v.35 no.1
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• pp.1-5
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• 2019

Species diversity is one of the most important indices that used to evaluate the sustainability of forest communities. In the present study, three variables including number of individuals (frequency of species), basal area and volume of tree species were compared to estimate tree species diversity in broadleaves forests of Iran. Based on systematic random design, 30 plots (circle plot, $1000m^2$) was selected. Type of species, number of species, DBH and height of trees were measured. Simpson (1-D), Hill ($N_2$), Shannon-Wiener (H'), Mc Arthur ($N_1$), Smith-Wilson ($E_{var}$) and Margalef ($R_1$) indices used to estimate tree species diversity. Species diversity was calculated in each plot. ANOVA test showed that there was a significant difference between of three variables used for estimation of species diversity. Number of trees variable has more precision than basal area and volume variables to estimate of species diversity. But Duncan test revealed that there were significant difference between of basal area and volume variables with number of trees. Therefore, basal area and volume variables were selected as more suitable variables in order to estimate of biodiversity indices in northern forests of Iran.

• 대한공업교육학회지
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• v.33 no.2
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• pp.300-311
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• 2008

This study investigates the natural convection of air(Pr=0.7) between two walls having a small- wave- number sinusoidal temperature distributions with a phase difference. The wave number and the phase difference of wall temperatures are k=0.5 and ㄱ/2, respectively. In the conduction-dominated regime at small Rayleigh number, two slightly inclined cells are formed over one wave length. At higher Rayleigh number, however, multicellular convection occurs in thermally unstable region. A spatial symmetry is intermittently broken in the transient period at the Rayleigh number near the critical value. The steady-state flows always satisfy the spatial symmetry. A steep increase of Nusselt number occurs near the Rayleigh number at which transition of flow pattern occurs.

• Journal of computational fluids engineering
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• v.18 no.4
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• pp.25-34
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• 2013

A numerical study of a laminar natural convection of the CuO-water nanofluid in a square cavity using the Buongiorno's nonhomogeneous model is presented. All the governing equations including the volume fraction equation are discretized on a cell-centered, non-uniform grid employing the finite-volume method with a primitive variable formulation. Calculations are performed over a range of Rayleigh numbers and volume fractions of the nanopartile. From the computed results, it is shown that both the homogeneous and nonhomogeneous models predict the deterioration of the natural convection heat transfer well with an increase of the volume fraction of nanoparticle at the same Rayleigh number, which was observed in the previous experimental studies. It is also shown that the differences in the computed results of the average Nusselt number at the wall between the homogeneous and nonhomogeneous models are very small, and this indicates that the slip mechanism of the Brown diffusion and thermophoresis effects are negligible in the laminar natural convection of the nanofluid. The degradation of the heat transfer with an increase of the volume fraction of the nanoparticle in the natural convection of nanofluid is due to the increase of the viscosity and the decrease of the thermal expansion coefficient and the specific heat. It is clarified in the present study that the previous controversies between the numerical and experimental studies are owing to the different definitions of the Nusselt number.

• The Mathematical Education
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• v.41 no.2
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• pp.227-231
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• 2002

The Pythagorean theorem and Pythagorean triple are well known. We know some Pythagorean triples, however we don't Cow well that every natural number can belong to some Pythagorean triple. In this paper, we show that every natural number, which is not less than 2, can be a length of a leg(a side opposite the acute angle in a right triangle) in some right triangle, and list some Pythagorean triples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.784-787
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• 2004

Modified version of subspace iteration method using accelerated starting vectors is proposed to efficiently calculate free vibration modes of structures. Proposed method employs accelerated Lanczos starting vectors that can reduce the number of iterations in the subspace iteration method. Proposed method is more efficient than the conventional method when the number of required modes is relatively small. To verify the efficiency of proposed method, two numerical examples are presented.