• Communications of the Korean Mathematical Society
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• v.10 no.4
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• pp.907-916
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• 1995

The unilateral weighted shift operator $W_r$ with the weighted sequence ${r^n}^\infty_{n=0}$ is unicellular if $0 < r < 1$. In general, A + B is not unicellular even if A and B are unicellular. We will prove that $W_r + W^2_r$ is unicellular if $0 < r < 1$.

• Bulletin of the Korean Mathematical Society
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• v.37 no.3
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• pp.411-418
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• 2000

In this paper, we want to give an operator which is not unicellular. We try to prove the non-unicellularity of the operator by using the method given in [8].

• Journal of Plant Biology
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• v.38 no.3
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• pp.289-295
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• 1995

Trichomes found in the genus Cimicifuga were examined with scanning electron microscopy. Four basic types of trichomes were found in the genus; (1) filiform unicellular trichomes, (2) saccate unicellular trichomes, (3) pyriform unicellular trichomes, and (4) uniseriate multicellular trichomes. All the taxa examined develop at least two different types of trichomes, and many taxa are distinguished by differences in type, microornamentation, density, and position of trichomes. In addition, trichome features appear to be very useful in recognizing species relationships in the genus.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.8
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• pp.755-762
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• 2000

Natural convection of air in a horizontal annulus with the inner cylinder cooled by the application of a constant heat flux and the isothermally heated outer cylinder is considered. The bifurcation phenomenon of flow patterns and the heat transfer characteristics are numerically investigated. The zero initial condition induces a unicellular flow in a half annulus. A bicellular flow consisting of two counter-rotating eddies in a half annulus can be obtained above a certain critical Rayleigh number. A transition from the bicellular to the unicellular flow occurs with a decrease in Rayleigh number. Hysteresis phenomena have not been observed. In the regime of dual flows, the overall Nusselt number of the bicellular flow is greater than that of the unicellular flow.

• Korean Journal of Plant Taxonomy
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• v.34 no.4
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• pp.273-285
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• 2004

A comparative micromorphology of petal and sepal of 15 species of Lycopus was undertaken to assess their usefulness in species identification and to evaluate their significance in the taxonomy using scanning electron microscope and stereo microscope. Five types of trichome are found within the genus: unicellular cylindrical trichome, unicellular trichome with papillae, simple multicellular trichome, capitate glandular trichome, and peltate glandular trichome. The types, distribution, and density of the trichomes show considerable variation among the taxa. The distributional pattern of the unicellular cylindrical trichomes on inner side of corolla is differed among the investigated taxa, and can be classified into four patterns. The apex shape of sepal and the incised position of calyx are also various and be recognizedas four patterns. The shape of cell composing in both outer and inner sides of petal and sepal are shown variously. Finally, the taxonomic significance of micromorphology of the petal and sepal in identification and elucidation of the genus Lycopus, especially among the species is also briefly discussed.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.1
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• pp.63-68
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• 2009

Among various microscopic organisms producing photobiological hydrogen, cyanobacteria have long been recognized as the promising biological agents for hydrogen economy in 21 century. For photobiological production of hydrogen energy, marine unicellular $N_2$-fixing cyanobacteria have been evaluated as an ideal subgroup of Cyanophyceae. To develope the hydrogen production technology using unicellular $N_2$-fixing cyanobacteria, 3 important factors are pre-requisite: 1) isolation of the best strain from marine natural environment, 2) exploration on the strain-specific optimal conditions for the photobiological hydrogen production, and finally 3) application of the molecular genetic tools to improve the natural ability of the strain to produce hydrogen. Here we reviewed the recent research & development to commercialize photobiological hydrogen production technology, and suggest that intensive R&D during next 10-15 years should be imperative for the future Korean initiatives in the field of the photobiological hydrogen production technology using photosynthetic marine unicellular cyanobacterial strains.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.104-110
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• 2010

Photobiological hydrogen production by nitrogen-fixing unicellular cyanobacteria has long been considered to be an environmentally sound and very promising method for the future supply of renewable clean energy. We tried to find out the optimum cell concentration for $H_2$ production in each of the two new Korean nitrogen-fixing unicellular cyanobacterial strains to compare with Synechococcus sp. strain Miami BG043511. The two Korean strains, Cyanothece sp. KNU CB MAL-031 and KNU CB MAL-058, were isolated from Korean west coasts. Cell concentrations up to 17 billion cells $ml^{-1}$ were applied to the tests. High cell concentration over 15 billion cells $ml^{-1}$ resulted in drastically reduced $H_2$ production in all the three strains. The two domestic strains, however, produced 2-3 time more hydrogen than Synechococcus sp. Miami BG043511 at cell concentrations of 5-10 billion cells $ml^{-1}$. At lower cell concentrations than 2 billion cells $ml^{-1}$, MAL-031 exhibited highest $H_2$ production followed by Miami BG043511, with far less production in MAL-058. Present result suggests that Cyanothece sp. MAL-CB031 might be one of the ideal nitrogen-fixing unicellular cyanobacterial strains for the photobiological hydrogen production.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.20-28
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• 2013

Photobiological hydrogen production by nitrogen-fixing unicellular cyanobacteria has long been considered to be an environmentally sound and very promising method for the future supply of renewable clean energy. Using six Korean nitrogen-fixing unicellular cyanobacterial strains and the Synechococcus sp. strain Miami BG043511 we performed cultivation experiments to find out the strain-specific optimal temperature for population growth and $H_2$ production. Under $20^{\circ}C$ the population growth of all the tested strains was significantly retarded in contrasts to the faster and higher growth under 25, 30 or $35^{\circ}C$. The highest growth rates in all the 7 strains were measured under $30^{\circ}C$ while the maximal biomass yields were under $30^{\circ}C$ (strains CB-MAL 026, 054, and 055) or $35^{\circ}C$ (strains 002, 031, 058, and Miami BG043511). The difference between the maximal biomass yields at $30^{\circ}C$ and $35^{\circ}C$ was not greater than 10%. The quantity of photobiologically produced $H_2$ was only slight larger under $35^{\circ}C$ than that under $20^{\circ}C$. Our result may suggest a two-step process of $H_2$ production which includes rapid and sizable production of biomass at $30^{\circ}C$ and the following high $H_2$ production at $20^{\circ}C$ by the test strains of marine nitrogen-fixing unicellular cyanobacteria.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.169-176
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• 2000

Natural convection in a wide-gap horizontal annulus is considered, and the transition of flows and the bifurcation phenomenon are investigated for the fluids with Pr=0.2 and 0.3. At Pr=0.2, a bicellular flow pattern is observed at high Rayleigh number, and the solution is unique. At Pr=0.3, both the steady unicellular and bicellular flows exist above a certain critical Rayleigh number. For the fluids of Pr=0.2, the bicellular flow can be obtained by the impulsive heating of the inner cylinder, but it is not obtained from the zero initial condition for Pr=0.3. Hysteresis phenomena have not been observed. A transition from a bicellular flow to a unicellular flow occurs for Pr=0.3.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.622-628
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• 2002

Numerical analysis has been carried out for two-dimensional steady and unsteady mixed convection in the annulus between co-rotating horizontal cylinders with a heated inner cylinder. The ratio of annulus gap($\sigma$) is taken from 1 to 10 and the order of mixed-convection parameter B(=Gr/(1+Re)$^2$) varies from 10$^4$to $10^0$. The flow patterns over this parameter range are steady multicellular, oscillatory multicellular or steady unicellular. The addition of co-rotating of both cylinders stabilizes the flow in the annulus and weakens the unsteadiness. Even in the large values of rotating parameter such as of $10^0$/($\sigma$=2) and 10$^2$($\sigma$=10), the flow pattern becomes asymptotic to the steady unicellular flow, like as in the rigid-body rotating flow.