• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.47.2-47.2
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• 2016

The protons and helium ions in the solar wind are observed to possess anisotropic temperature profiles. The anisotropy appears to be limited by various marginal instability conditions. One of the efficient methods to investigate the global dynamics and distribution of various temperature anisotropies in the large-scale solar wind models may be that based upon the macroscopic quasi-linear approach. The present paper investigates the proton and helium ion anisotropy instabilities on the basis of comparison between the quasi-linear theory versus particle-in-cell simulation. It is found that the overall dynamical development of the particle temperatures is quite accurately reproduced by the macroscopic quasi-linear scheme. The wave energy development in time, however, shows somewhat less restrictive comparisons, indicating that while the quasi-linear method is acceptable for the particle dynamics, the wave analysis probably requires higher-order physics, such as wave-wave coupling or nonlinear wave-particle interaction. We carried out comparative studies of proton firehose instability, aperiodic ordinary mode instability, and helium ion anisotropy instability. It was found that the agreement between QL theory and PIC simulation is rather good. It means that the quasilinear approximation enjoys only a limited range of validity, especially for the wave dynamics and for the relatively high-beta regime.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.233-236
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• 2000

Bacillus thuringiensis (Bt) is the most widely used microbial insecticide in the biological control market. Cultivation of the microorganism to high cell densities offers potential for enhancing the rate of formation as well as the concentration of the desired products In the fermentation broths in bioreactor. With this objective, we developed the new bioreactor incorporating ceramic membrane module for the retention of cell mass. Cell yield and spore formation of Bacillus thuringiensis was improved markedly by adopting this new bioreactor based on glucose -limited feeding operation. It was possible to grow the cell and the heat-resistant spore to above $1.2\;{\times}\;10^{10}\;CFU/ml$ density. With glucose-limited operation, we studied the growth behavior of Bacillus thuringiensis during the cell retention culture. Linear growth of Bacillus thuringiensis was observed under glucose-limited culture, which matched well with simple mathematical model of cell retention culture.

• Journal of computational fluids engineering
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• v.5 no.1
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• pp.14-21
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• 2000

A method of two and three dimensional orthogonal grid generation with control of spacing by using the covariant Laplace equation is presented. An important feature of the methodology is its ability to control effectively the grid spacing especially near the boundaries still maintaining good orthogonality in whole field. The method is based on the concept of decomposition of the global transformation into consecutive transformation of an approximate conformal mapping and an auxiliary orthogonal mapping to have linear and uncoupled equations. Control of cell spacing is based on the concept of reference arc length, and orthogonal correction is peformed in the auxiliary domain. It is concluded that the methodology can successfully generate well controlled orthogonal grids around bodies of 2 and 3 dimensional configurations.

• Journal of the Korea Society of Computer and Information
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• v.21 no.1
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• pp.59-64
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• 2016

This paper suggests heuristic algorithm with O(mn) polynomial time complexity using Excel for partially survivable networks optimization problem of cellular telecommunication systems with m cells and n hubs. This problem only can be get the solution using linear programming or LINGO software package. The proposed algorithm connects the cell to hubs in ring network with minimum cost as the connection diversity of each cell. If the traffic of ring network (T) is T>2K for ring capacity (K), we adjust the maximum cost hub to MTSO that has a ascending order of (D/DC)/${\Delta}^+$ cell with each cell traffic demand (D) and ${\Delta}^+$=(MTSO cost-maximum cost hub) than we get the $T{\leq}2K$. Finally, we adjust MTSO to the removed maximum cost hub for the cell with 2K-$T{\geq}$(D/DC) and $_{max}{\Delta}^-$. While we using like this simple method, the proposed algorithm can be get the same optimal solution for experimental data as linear programing and LINGO software package.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.505-511
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• 2015

Solid oxide fuel cell operate at high temperature ($800{\sim}1000^{\circ}C$). High temperature have an advantage of system efficiency, but a weak durability. In this study, linear state space controller is designed to handle the temperature of solid oxide fuel cell system for proper thermal management. System model is developed under simulink environment with Thermolib$^{(R)}$. Since the thermally optimal system integration improves efficiency, very complicated thermal integration approach is selected for system integration. It shows that temperature response of fuel cell stack and catalytic burner are operated at severe non-linearity. To control non-linear temperature response of SOFC system, gain scheduled linear quadratic regulator is designed. Results shows that the temperature response of stack and catalytic burner follows the command over whole ranges of operations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.530-538
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• 2010

In this paper, estimation methods of cell searching and DoA (Direction of Arrival) for mobile relay stations with a uniform linear array are proposed. The proposed methods can improve the performance of cell searching and DoA estimation by removing the effect of STOs when there exist symbol timing offsets (STOs) between the signals received from adjacent base stations,. Also, the proposed methods can improve the performance of DoA estimation significantly when there exists Doppler frequency shift caused by movement of the mobile relay station. The performances and computational complexities of the proposed cell searching and DoA methods are evaluated by computer simulation under Mobile WiMAX environments.

• Journal of Microbiology and Biotechnology
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• v.8 no.4
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• pp.409-411
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• 1998

The effects of iron and EDTA on the growth of Chlorella sp. KR-1, a highly$CO_2$tolerant fresh water micro alga, have been determined. The algal growth was significantly affected not only by iron concentrations in the medium but by the ratio of iron to EDTA. The linear growth rate and the final cell concentration are increased with the supplementation of EDTA. Enhanced growth of Chlorella sp. KR-1 by the supplementation of EDTA was mainly due to the fact that the supply of iron to the algal culture had been possible for a longer time. When Chlorella sp. KR-1 is cultured in the medium of iron-15H-EDTA, the linear growth rate and the final cell concentration are at their maximum, 0.88 g/l${\cdot}$day and 9.1 g/l, respectively. The results show that Chlorella sp. KR-1 may be used for mass cultivation to fix$CO_2$from stack gases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.496-499
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• 2002

In this paper, a phase shifter with shifting photonic bandgap(PBG) cell in linear feedforward amplifier is designed and fabricated in 5GHz wireless LAN band. Now a day, the phase shifter has been fabricated with hybrid type. In this paper, a portion of PBG cell is shifted for the tuning phase. The phase shift was achieved maximum 80o in our PBG structure. Shifting PBG cell has been applied in feedforward main loop to cancel the main two tone signal.

• Journal of Communications and Networks
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• v.18 no.6
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• pp.873-883
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• 2016

In this paper, we focus on maximizing weighted sum energy efficiency (EE) for a multi-cell multi-user channel. In order to solve this non-convex problem, we first decompose the original problem into a sequence of parallel subproblems which can optimized separately. For each subproblem, a base station employs dirty paper coding to maximize the EE for users within a cell while regulating interference induced to other cells. Since each subproblem can be transformed to a convex multiple-access channel problem, the proposed method provides a closed-form solution for power allocation. Then, based on the derived optimal covariance matrix for each subproblem, a local optimal solution is obtained to maximize the sum EE. Finally, simulation results show that our algorithm based on non-linear precoding achieves about 20 percent performance gains over the conventional linear precoding method.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.27-33
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• 2011

HCPV(High Concentrated PV) systems have well known for CPV market all over the world. Low concentration type silicon based modules have been introduced in the market. But low cost of standard flat silicon modules made them useless nowadays. High cost of compound semiconductor solar cell reduced cost effective cpv module production than that of recently silicon solar cell. In order to overcome increasing cost of CPV module, we study middle concentration type fresnel lens simulation using concentrated type silicon based solar cell. Linear type fresnel lens made production of CPV module without secondary optics such as light pipe or light tunnel. This type of fresnel lens design makes more cost effective solution for cpv niche market.