• Korean Journal of Optics and Photonics
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• v.2 no.4
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• pp.186-192
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• 1991

For the micro-lithography using a excimer laser beam $(\lambda\leq0.248$\mu\textrm{m})$. a mirror system consisting of four spherical surfaces with reductlon magnification 5X is designed. Initially the aplanat, flat field and the distortion free condition of the system are analytically investigated within Seidel 3rd order aberrations. And the computer-aided optimization technique has been employed for the further improved performance of the system. The final system has N.A. of 0.15 and image field diameter 3.3 mm, and has the diffraction-limited performance for KrF eximer laser beam.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.876-885
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• 2000

A new and simple method is presented for determining the parasitic resistances of MESFET and HEMT from the measured S-parameters under normal active bias without depending on additional DC measurements or iteration or optimization process. The presented method is based on the fact that the difference between source resistance(Rs) and drain resistance(Rd) can be obtained from the measured Z-parameters under zero bias condition. It is possible to define the new internal device including intrinsic device and 3 parasitic resistances by elimination the parasitic inductances and capacitances from the measured S-parameters. Three parasitic resistances are calculated easily from the fact that the real parts of Yint,11 and Yint,12 of intrinsic Y-parameters are zero theoretically and the relations between S-,Z-, Y-matrices. The calculated parasitic resistances using the presented method and successively calculated equivalent circuit parameters give modeled S-parameters which are in good agreement with the measured S-parameters up to 400Hz.

• Journal of Ginseng Research
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• v.46 no.3
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• pp.367-375
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• 2022

Background: Short-term hydroponic-cultured ginseng (sHCG), which is 1-year-old ginseng seedlings cultivated for 4 weeks in a hydroponic system, is a functional food item with several biological effects. However, the optimal extraction conditions for sHCG, and the bioactivity of its extracts, have not been evaluated. Methods: Chlorogenic acid (CGA) and ginsenoside contents were evaluated in sHCG, white ginseng (WG), and red ginseng (RG) using high-performance liquid chromatography. Response surface methodology (RSM) was used to optimize the extraction conditions (temperature and ethanol concentration) to maximize the yield of dry matter, CGA, and four ginsenosides (Re, Rg₁, Rb₁, and Rd) from sHCG. The optimal extraction conditions were applied to pilot-scale production of sHCG extracts. The expression levels of tumor necrosis factor (TNF)-α/interferon (IFN)-γ-induced thymic and activation-regulated chemokines (TARC/CCL17) were measured after treatment with sHCG, WG, and RG extracts, and the effects of their bioactive compounds (CGA and four ginsenosides) on human skin keratinocytes (HaCaTs) were evaluated. Results: CGA and four ginsenosides, which are bioactive compounds of sHCG, significantly inhibited TNF-α/IFN-γ-induced TARC/CCL17 expression. The optimal sHCG extraction conditions predicted by the RSM models were 80 ℃ and 60% ethanol (v/v). The sHCG extracts produced at the pilot scale under optimal conditions greatly alleviated TNF-α/IFN-γ-induced TARC/CCL17 production compared with WG and RG extracts. Conclusions: Pesticide-free sHCG extracts, which contain high levels of CGA and the ginsenosides Re, Rg₁, Rb₁, and Rd as bioactive compounds, may have therapeutic potential for atopic diseases.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.514-521
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• 2016

The High Efficiency Video Coding (HEVC) standard provides superior coding efficiency by utilizing highly flexible block structure and more diverse coding modes. However, rate-distortion optimization (RDO) process for the decision of optimal block size and prediction mode requires excessive computational complexity. To alleviate the computation load, this paper proposes a new moment-based fast CU size decision algorithm for intra coding in HEVC. In the proposed method, moment values are computed in each CU block to estimate the texture complexity of the block from which the decision on an additional CU splitting procedure is performed. Unlike conventional methods which are mostly variance-based approaches, the proposed method incorporates the third-order moments of the CU block in the design of the fast CU size decision algorithm, which enables an elaborate classification of CU types and thus improves the RD-performance of the fast algorithm. Experimental results show that the proposed method saves 32% encoding time with 1.1% increase of BD-rate compared to HM-10.0, and 4.2% decrease of BD-rate compared to the conventional variance-based fast algorithm.

• Journal of Communications and Networks
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• v.13 no.4
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• pp.345-359
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• 2011

Decode-and-forward relaying is a promising enhancement to existing radio access networks and is already standardized in 3rd generation partnership project (3GPP) as a part of long term evolution (LTE)-Advanced Release 10. Two inband operation modes of relay nodes are supported, namely type 1 and type lb. Relay nodes promise to offer considerable gain for system capacity or coverage, depending on the deployment prioritization, in a cost-efficient way. Yet, in order to fully exploit the benefits of relaying, the inter-cell interference which is increased due to the presence of relay nodes should be limited. Moreover, large differences in the received power levels from different users should be avoided. The goal is to keep the receiver dynamic range low in order to retain the orthogonality of the single carrier-frequency division multiple access system. In this paper, an evaluation of the relay based heterogeneous deployment within the LTE-Advanced uplink framework is carried out by applying the standardized LTE Release 8 power control scheme both at evolved node B and relay nodes. In order to enhance the overall system performance, different power control optimization strategies are proposed for 3GPP urban and suburban scenarios. A comparison between type 1 and type 1b relay nodes is as well presented to study the effect of the relaying overhead on the system performance in inband relay deployments. Comprehensive system level simulations show that the power control is a crucial means to increase the cell edge and system capacities, to mitigate inter-cell interference and to adjust the receiver dynamic range for both relay node types.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.468-475
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• 2012

A proper stacking force and assembly are important to the performance of fuel cell. Improper assembly pressure may lead to leakage of fuels and high interfacial contact resistance, excessive assembly pressure may result in damage to the gas diffusion layer and other components. The pressure distribution of gas diffusion layer is important to make interfacial contact resistance less for stack performance. To analyze the influence of design parameter factors for pressure distribution, and to optimize stack design, DOE (Design of Experiment) was used for polymer electrolyte membrane fuel cell stack pressure test. As commonly known, the higher clamping force improves the fuel cell stack performance. However, non-uniformity of stress distribution is also increased. It shows that optimization between clamping force and stress distribution is needed for well designed structure of fuel cell stack. In this study, stack design optimization method is suggested by using FEM (Finite Element Methode) and DOE for light-weighted fuel cell stack.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.6
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• pp.459-464
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• 2004

The objective of this study is to improve cephalosporin C (CPC) production byoptimization of medium and culture conditions. A statistical method was introduced to optimize the main culture medium. The main medium for CPC production was optimized using a statistical method. Glucose and corn steep liquor (CSL) were found to be the most effective factors for CPC production. Glucose and CSL were optimized to 2.84 and $6.68\%$, respectively. CPC produc­tion was improved $50\%$ by feeding of $5\%$ rice oil at day 3rd and 5th day during the shake flask culture of C acremonium M25. The effect of agitation speeds on CPC production in a 2.5-L bio­reactor was also investigated with fed-batch mode. The maximum cell mass (54.5 g/L) was obtained at 600 rpm. However, the maximum CPC production (0.98 g/L) was obtained at 500 rpm. At this condition, the maximum CPC production was improved about $132\%$ compared to the re­sult with batch flask culture.

• Earthquakes and Structures
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• v.5 no.2
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• pp.225-237
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• 2013

Excessive vibrations induced by earthquake excitation and wind load are an obstacle in design and construction of tall and super tall buildings. An innovative vibration control structure system (Mega-Sub Controlled Structure System-MSCSS) was recently proposed to further improve humans comfort and their safeties during natural disasters. Preliminary investigations were performed using a two dimensional equivalent simplified model, composed by 3 mega-stories. In this paper, a more reasonable and realistic scaled model is design to investigate the dynamical characteristics and controlling performances of this structure when subjected to strong earthquake motion. The control parameters of the structure system, such as the modulated sub-structures disposition; the damping coefficient ratio (RC); the stiffness ratio (RD); the mass ratio of the mega-structure and sub-structure (RM) are investigated and their optimal values (matched values) are obtained. The MSCSS is also compared with the so-called Mega-Sub Structure (MSS) regarding their displacement and acceleration responses when subjected to the same load conditions. Through the nonlinear time history analysis, the effectiveness and the feasibility of the proposed mega-sub controlled structure system (MSCSS) is demonstrated in reducing the displacement and acceleration responses and also improving human comfort under earthquake loads.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.361-365
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• 1991

The problem being considered here is the determination of optimal guidance laws for a launch vehicle for scientific missions. The optimal guidance commands are determined in the sense that the least amount of fuel is used. A numerical solution was obtained for the case where the position and velocity state variables satisfy a specified constraint at the time of thrust cutoff. The method used here is based on the Pontryagin's maximum principle. This is the method of solving a problem in the calculus of variations. In particular, it applies to the problem considered here where the magnitude of the control is bounded. Simulations for the optimal guidance algorithm, during the 2nd and the 3rd-stage flight of the Japanese rocket M-3H-3, are carried out. The results show that the guided trajectory that satisfying the terminal constraints is optimal, and the guidance algorithm works well in the presence of some errors during the 1st-stage pre-programmed guidance phase.

• The KSFM Journal of Fluid Machinery
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• v.4 no.4 s.13
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• pp.22-27
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• 2001

The pump/motor selection program for optimized selection of regional water supply facilities was developed based on a flowchart compiled from basic operational data, total head requirement, initial pump/motor specification selection etc. This program was developed in Visual Basic. The program accepts, as in the flowchart, operational requirements of pumps and other system requirements, and calculates specific speed based on flow rate, total head and rotational speed. Then the calculated specific speed is used to select pump types and speed prior to determining likelihood of cavitation occurring at the calculated NPSH. Power requirement is then calculated for safe operation of pump to assist final pump selection. Test results of the program match very closely to the design values of Paldang intake pump station(3rd stage) proving that the program can be used as an effective and practical aid for designing new regional water supply systems.