• 대한수학회논문집
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• 제10권4호
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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 $0 < r < 1$.

• 대한수학회보
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• 제37권3호
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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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• 제38권3호
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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.

• 설비공학논문집
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• 제12권8호
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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.

• 식물분류학회지
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• 제34권4호
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• pp.273-285
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• 2004

Lycopus속 15종의 화판(petal)과 악편(sepal)의 미세형태를 주사전자현미경과 실체현미경으로 관찰하여 그 분류학적 유용성을 검토하였다. Lycopus속 분류군들의 화관과 악에 분포하는 모용과 선모는 단세포 원주모(unicellular cylindrical trichome), 표면에 돌기가 있는 단세포 모용(unicellular trichome with papillae), 다세포 모용(simple multicellular trichome), 두상선모(capitate glandular trichome) 및 방패형 선모(peltate glandular trichome) 등 5 종류로 나타났으며, 모용의 종류, 분포, 밀도가 분류군마다 다르게 나타났다. 화관 안쪽면에 단세포 원주모(unicellular cylindrical trichome)의 분포 정도가 각 분류군마다 다르게 나타나, 그 분포 부위에 따라 4가지 유형으로 나눌 수 있었다. 악(calyx)은 악편이 갈라지는 정도와 악편 정단(apex)의 모양으로 4가지 형태로 구분할 수 있었다. 화판과 악편의 안쪽 빛 바깥면을 구성하는 세포의 형태는 그 위치와 분류군에 따라 다양하게 나타났다. 끝으로 관찰된 Lycopus속의 화판 및 악편 미세형태를 검토한 결과 종간 식별에 유용하였다.

• 한국해양학회지:바다
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• 제14권1호
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• pp.63-68
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• 2009

광생물학적 수소생산 잠재력을 가진 다양한 미소생물 가운데, 남세균은 21세기의 수소경제 시대에 적합한 생물군으로 오랫동안 알려져 왔다. 광생물학적으로 수소에너지를 생산하게 될 경우, 해양 단세포성 질소고정 남세균은 남세균류의 하부 분류군들 가운데 가장이상적인 종류의 하나로 평가되고 있다. 단세포성 질소고정 남세균을 이용한 수소생산 기술을 개발하기 위해 반드시 고려해야 할 3가지 사항은 1) 자연계에 존재하는 최우수 수소생산 종주의 확립 2) 광생물학적 수소생산을 뒷받침하는 종주-특이적 최적조건의 탐색 3) 유전학적 방법을 이용한 수소생산 종주의 개량 등이다. 본고에서는 광생물학적 수소생산기술의 상업화를 향한 최근의 연구 개발 추세를 돌아보고, 해양 단세포성 남세균 종주를 이용한 광생물학적 수소생산 기술 분야에서 한국의 세계선도적 지위 확보를 위해서는 향후 10-15년간 집중적인 연구 개발이 절실함을 제안하고자 한다.

• 한국수소및신에너지학회논문집
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• 제21권2호
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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.

• 한국수소및신에너지학회논문집
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• 제24권1호
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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.

• 대한기계학회논문집B
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• 제24권2호
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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.

• 대한기계학회논문집B
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• 제26권4호
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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.