• Ocean and Polar Research
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• 제32권2호
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• pp.97-111
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• 2010

Phytoplankton production is affected by various physico-chemical factors of environment. However, one of the most critical factors generally accepted as controlling primary production of phytoplankton is nutrients. It has recently been found that the succession of phytoplankton groups and species are closely related to the chemical properties of ambient water including nutrient limitation and their ratios. In Jangmok Bay, silicate and nitrate are primarily supplied by rainfall, while phosphate and ammonia are supplied by wind stress. Typhoons are associated with rainfall and strong wind stress, and when typhoons pass through the South Sea, such events may induce phytoplankton blooms. When nutrients were supplied by heavy rainfalls during the rainy season and by summer typhoons in Jangmok Bay, the dominant taxa among the phytoplankton groups were found to change successively with time. The dominant taxon was changed from diatoms to flagellates immediately after the episodic seasonal events, but returned to diatoms within 3~10 days. Pseudo-nitzschia spp. were dominant mainly in the presence of low phosphate levels during the first of the survey which included the rainy season, while Skeletonema costatum was dominant when phosphate concentrations were high due to the strong wind stress during the latter half of the survey as a result of the typhoon. The competition between S. costatum and Chaetoceros spp. appeared to be regulated by the silicate concentration. S. costatum preferred high silicate and phosphate concentrations; however, Chaetoceros spp. were able to endure low silicate concentrations. These results implied that, in coastal ecosystems, the input patterns of each nutrient supplied by rainfall and/or wind stress appeared to contribute to the summer succession of phytoplankton groups and species.

• 한국지반공학회논문집
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• 제30권4호
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• pp.101-106
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• 2014

관입시험은 한정된 범위에서 1차원적 정보를 얻을 수 있으나, N치는 다양한 지반설계정수와 실험적으로 연관되어 있다. 탄성파를 이용한 비파괴 검사는 역산 과정을 통해 비용 및 시간에 효율적으로 2차원 및 3차원 물성에 대한 지도를 얻을 수 있으며, N치와 탄성파 속도는 간극비, 포화도, 유효응력 등에 의해 좌우된다. 따라서 N치와 탄성파 속도간의 경험적 관계들이 제안되어 왔다. 본 연구는 다양한 간극비와 포화도를 갖는 주문진사에 대해 정지토압조건에서 탄성파를 실험적으로 측정하였다. 그 결과 하중 조건이 간극비 및 포화도에 비하여 가장 영향을 주는 요소로 나타났으며, 간극비와 포화도는 응력-속도 관계의 경향에 영향을 주었다. 각 영향인자간의 관계를 다중회귀분석을 통해 상관식으로 나타내었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1998년도 터널.암반역학위원회 박사학위 논문집
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• pp.3-34
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• 1998

The stability condition of rock slopes is greatly affected by the geometry and strength parameters of discontinuities in the rock masses. Rock slopes Involving movement of rock blocks on discontinuities are failed by one or combination of the three basic failure modes-plane, wedge, and toppling. In rock mechanics, practically all the parameters such as the joint set characteristics, the rock strength properties, and the loading conditions are always subject to a degree of uncertainty. Therefore, a reasonable assessment of the rock slope stability has to include the excavation of the multi-failure modes, the consideration of uncertainties of discontinuity characteristics, and the decision on stabilization measures with favorable cost conditions. This study was performed to provide a new numerical model of the deterministic analysis, reliability analysis, and reliability-based optimization for rock slope stability. The sensitivity analysis was carried out to verify proposed method and developed program; the parameters needed for sensitivity analysis are design variables, the variability of discontinuity properties (orientation and strength of discontinuities), the loading conditions, and rock slope geometry properties. The design variables to be optimized by the reliability-based optimization include the cutting angle, the support pressure, and the slope direction. The variability in orientations and friction angle of discontinuities, which can not be considered in the deterministic analysis, has a greatly influenced on the rock slope stability. The stability of rock slopes considering three basic failure modes is more influenced by the selection of slope direction than any other design variables. When either plane or wedge failure is dominant, the support system is more useful than the excavation as a stabilization method. However, the excavation method is more suitable when toppling failure is dominant. The case study shows that the developed reliability-based optimization model can reasonably assess the stability of rock slopes and reduce the construction cost.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.71-74
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• 1996

Ta$_2$O$_{5}$ film ale recognized as promising capacitor dielectric for future DRAM\`s. The electrical properties of Ta$_2$O$_{5}$films greatly depend on the heating condition. In the practical fabrication process, several annealing process, such as the annealing of Al in H$_2$(about 40$0^{\circ}C$) and reflow of BPSG (borophosphosilicate glass) film in $N_2$(about 80$0^{\circ}C$), exist after deposition of Ta$_2$O$_{5}$ film. In this paper, we describe the temperature effect on the electrical properties of W/Ta$_2$O$_{5}$/Si structure. The thin film of Ta$_2$O$_{5}$ and tungsten have been deposited on p-si(100) wafer using the sputtering system. The heating temperature was varied from 500 to 90$0^{\circ}C$ in $N_2$for 30min and The degree of temperature is 100\`C. In a log(J/E$^2$) Vs 1/E plot of typical I-V data, we find a linear relationship for the temperature of 500, $600^{\circ}C$ and as deposition. This could indicate Fowler-Nordheim tunneling as the dominant mode of current transports. However, we can not find a linear relationship for the temperature above $700^{\circ}C$. This could not indicate Fowler-Nordheim tunneling as the dominant mode of current transport. The high frequency (1MHz) capacitance-voltage (C-V) of W/Ta$_2$O$_{5}$/Si Capacitor were investigated on the basis of shift in the threshold voltage and dielectric constant. The magnitude of the threshold voltage and dielectric constant depends on the heating temperature, and increases with heating temperature.temperature.

• 한국자기학회지
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• 제8권6호
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• pp.369-373
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• 1998

본 연구에서는 마그네트론 스퍼터링 법으로 제작한 Ni-Fe/NiO 이층 박에서, NiO 증착 중 Ar 압력에 따른 교환이 방성의 변화를 고찰하엿으며 이를 미세조작과 관련시켜 해석하고자 하였다. 낮은 Ar 압력에서 증착한 Ni-Fe/NiO 이층막은 우수한 교환이방성 특성을 나타내었으나 Ar 압력이 증가함에 따라 교환이방성은 급격하게 감소하였다. 낮은 Ar 압력에서 증착한 시편은 NiO와 Ni-Fe 계면에서 epitaxy 경향을 나타내었으며 그 계면은 평범하고 그 경계는 두렷하게 구분하였다. 그러나 높은 Ar 압력에서 증착한 시편은 NiO와 Ni-Fe의 경계가 뚜렷하게 구분되지 않고 그 계면 또한 평활하지 않았다. 한편 NiO의 조성은 Ar압력의 증가에 따라 산소의 조성이 점점 증가하였다.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.2171-2175
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• 2013

The electronic structure and elastic properties of the 4d transition metal carbides MC (M = Y, Zr, Nb, Rh) were studied by means of extended H$\ddot{u}$ckel tight-binding band electronic structure calculations. As the valence electron population of M increases, the bulk modulus of the MC compounds in the rocksalt structure does not increase monotonically. The dominant covalent bonding in these compounds is found to be M-C bonding, which mainly arises from the interaction between M 4d and C 2p orbitals. The bonding characteristics between M and C atoms affecting the variation of the bulk modulus can be understood on the basis of their electronic structure. The increasing bulk modulus from YC to NbC is associated with stronger interactions between M 4d and C 2p orbitals and the successive filling of M 4d-C 2p bonding states. The decreased bulk modulus for RhC is related to the partial occupation of Rh-C antibonding states.

• 한국염색가공학회지
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• 제15권1호
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• pp.48-55
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• 2003

As the polyester fiber becomes thinner, thermomigration that is the most important factor deteriorating the washfastness, is more dominant. For improving the washfastness of ultrafine polyester dyed with disperse dye, it is necessary either to decrease the amount of thermomigrated dyes on the fiber surface, or to use a disperse dye containing diester group in the coupling component. This paper is concerned to investigate the relation between the chemical structure of three disperse dyes and their dyeing properties and washfastness. The disperse dye whose molecular size is big, can dye ultrafine polyester with good build-up, and its washfastness is reasonably good. Other disperse dye which has diester group, shows the same dyeing properties as the standard disperse dye, and its washfastness is better than that of the standard disperse dye.

• 소음진동
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• 제1권1호
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• pp.45-52
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• 1991

The dynamic properties of primary-secondary structural systems are examined using analytical expressions for the modal properties. The analysis begins with a Lagrange multiplier formulation to develop a characteristic equation in terms of primary system mobilities and secondary system impedances. The complexity of the characteristic equation by developing new method, frequency window method. It is shown that the reduction of complexity can only be obtained by a reduction of accuracy, but by retaining the dominant effects of the dynamics problem, the loss of accuracy is not excessive. The reduced problem is examined further to develop simple expressions for the modal properties which provide insight into the resonance characteristics of the primary-secondary system problem. The results are useful as a complement to existing computational techniques for understanding and interpreting dynamic analysis results.

• 한국지구과학회지
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• 제36권5호
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• pp.427-436
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• 2015

We classified Abell clusters using the magnitude differences between two or three bright member galaxies and investigated how such classification was correlated with the properties of brightest cluster galaxies (BCGs). S-type BCGs being clearly brighter than the rest of the member galaxies were likely to be red, luminous, and evolved as early type galaxies. On the other hand, T-type BCGs being not dominant at all were less luminous than early type galaxies. A small fraction of BCGs was currently forming stars, and all of the star-forming BCGs were T-type BCGs. Active galactic nuclei were most frequent for S-type BCGs. Through these quantitative analyses of the BCG properties, we discussed the possible scenario of BCG formation and the differences between S-type and T-type of BCGs.

• Management Science and Financial Engineering
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• 제18권1호
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• pp.13-20
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• 2012

This paper considers a revenue maximization problem on a single processor. Each job is identified as its processing time, initial reward, reward decreasing rate, and preferred start time. If the processor starts a job at time zero, revenue of the job is its initial reward. However, the revenue decreases linearly with the reward decreasing rate according to its processing start time till its preferred start time and finally its revenue is zero if it is started the processing after the preferred time. Our objective is to find the optimal sequence which maximizes the total revenue. For the problem, we characterize the optimal solution properties and prove the NP-hardness. Based upon the characterization, we develop a branch-and-bound algorithm for the optimal sequence and suggest five heuristic algorithms for efficient solutions. The numerical tests show that the characterized properties are useful for effective and efficient algorithms.