• Journal of Institute of Control, Robotics and Systems
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• v.9 no.11
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• pp.868-873
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• 2003

$H_{\infty}$ control has been applied to the design of practical control systems widely because of its robustness. It can minimize $H_{\infty}$ norm of the transfer function between the desired output and the disturbances. The SMC(Sliding Mode Control) is more robust and give the better performance than the $H_{\infty}$ control if the matching condition is satisfied. A controller which can have the advantages of $H_{\infty}$ control and the SMC is proposed to add the robustness of the SMC to the $H_{\infty}$ controller. Its design is based on the augmented system of which dynamics have one higher order than that of the original system and has the same dynamic as the desired system in spite of uncertainties. The dynamic of proposed sliding surface is the same dynamic as the system controlled by $H_{\infty}$ controller without the uncertainties which satisfy the matching condition.

• Journal of the Korean Electrochemical Society
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• v.23 no.1
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• pp.18-23
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• 2020

Antimony telluride (Sb_xTe_y) thin films were synthesized by an electrodeposition method with a control of applied potential at room temperature. Characterization of electrical and thermoelectric properties such as conductivity, Seebeck coefficient, and power factor (P.F.) were conducted as a function of the chemical composition of the electrodeposited films. Morphology of thin films were dense and uniform and the composition was tailored from 25 to 60 at.% of the Sb content by altering the applied potential from -0.13 to -0.27 V (vs. SCE). The conductivity of the films were ranged from 2 × 10^-4 ~ 5 × 10^-1 S/cm indicating their amorphous behavior. The meaured Seebeck coefficient of films were relatively high compared to that of bulk single cyrstal Sb_xTe_y due to their low carrier concentration. The variation of the Seebeck coefficient of the films was also related to the change of chemical composition, showing the power factor of ~10 ㎼/mK².

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.7
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• pp.578-583
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• 2002

This paper presents a method for designing fuzzy $H_2/H_{\infty}$ controllers of nonlinear systems with time varying delay. Takagi-Sugeno fuzzy model is employed to represent nonlinear systems with time varying delay. Using a single quadratic Lyapunov function, the globally exponential stability and $H_2/H_{\infty}$ performance problem are discussed. A sufficient condition for the existence of fuzzy $H_2/H_{\infty}$ controllers is then presented in terms of linear matrix inequalities(LMls). The proposed fuzzy $H_2/H_{\infty}$ controllers minimizes the upper bound on the linear quadratic performance measure.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1697-1701
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• 2016

The leakage conduction and critical voltage characteristic of ZnO ceramic were investigated as a function of $Sb_2O_3$ concentration. Leakage conduction in the ohmic region increased with increasing $Sb_2O_3$ concentration and was attributed to the potential barrier height. The nonlinear coefficient increased with an increasing amount of $Sb_2O_3$. It was found that increases in the apparent critical voltages were associated with the lowered donor concentration in the grain boundary of between two ZnO grains. And the decrease of donor concentration on doping with $Sb_2O_3$ additive was attributed to the lowered capacitance in the grain boundary layer.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.3
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• pp.105-109
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• 2011

Drift Velocity of Electrons in pure $CF_4$, $CH_4$ and mixtures of $CF_4$ and Ar. Have been analyzed over a range of the reduced electric field strength between 0.1 and 350[Td] by the two-term approximation of the Boltzmann equation (BEq.) method and the Monte Carlo simulation (MCS). The results of the Boltzmann equation and the Monte Carlo simulation have been compared with the data presented by several workers. The deduced transport coefficients for electrons agree reasonably well with the experimental and simulation data obtained by Nakamura and Hayashi. The energy distribution function of electrons in $CF_4$-Ar mixtures shows the Maxwellian distribution for energy. That is, f(${\varepsilon}$) has the symmetrical shape whose axis of symmetry is a most probably energy. The measured results and the calculated results have been compared each other.

• Journal of the Korean Professional Engineers Association
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• v.19 no.3
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• pp.23-30
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• 1986

This study summarizes the results of tests on 18 two-slab push out specimens. The main purpose of tile survey was to evaluate the capacity and behavior of stud shear connectors embedded in high strength normal concrete (F$\sub$c/=260～390kg/$\textrm{cm}^2$). The normal concrete was made with crushed stones and natural sand near the Han River. Two different diameters (ø19mm, ø16 mm) of stud shear connectors were used for push out specimens. The following conclusions were drawn from this study. 1) The shear strength of stud connectors embedded in high strength concrete (F$\sub$c/=260～390kg/$\textrm{cm}^2$) was influenced by tensile stress of the stud shear connectors. The following empirical function described the test results: q$\sub$u/=0.5A$\sub$s/√F$\sub$c/E$\sub$c/$\leq$0.7A$\sub$u/F$\sub$u/ 2) The maximum load in this study was reached at slips varying from 2.5～6mm.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.255-260
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• 2005

Direct solid state synthesis by hot pressing has been applied in order to produce high efficiency $Zn_4Sb_3$ bulk specimens. Single phase $Zn_4Sb_3$ with 98.5% of theoretical density was successfully produced by direct hot pressing of elemental powders containing 1.2 at.% excess Zn. Thermoelectric properties as a function of temperature were investigated from room temperature to 600 K and compared with results of other studies. Transport properties at room temperature were also evaluated. Thermoelectric properties of single phase $Zn_4Sb_3$ materials produced by direct synthesis were measured and are comparable to the published data. Direct solid state synthesis by hot pressing provides a promising processing route in this material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.205-208
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• 1999

We have studied properties(crystal structure, density, absorption, contraction, initial permeability, and permeability) of Ba$\sub$0.2/Me$\sub$0.31/Fe$\sub$0.49/(Me:Ni$\sub$1-x/, Cu$\sub$x/ x=0~1) ferrites with various Me site, because of development of magnetic materials for inductor. As a results of the density, absorption rate, and shrinkage rate, the sintering temperature of Ba$\sub$0.2/ Me$\sub$0.31/ FEesub 0.49/(Me:Ni$\sub$1-x/ x=0.25, 0.75) had got over 1100$^{\circ}C$ for 3 hours. According to SEM images, the configurations of grain were hexagonal, Increasing the sintering temperature, initial Permeability increased. The complex permeabilities as a function of for several MHz showed constants.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.267-268
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• 2015

The multi-environment probability density function model has been applied to simulate the turbulent $CH_4/H_2$ flames under MILD conditions. The direct quadrature method of moments (DQMOM) has been adopted to solve the transport PDF equation due to its computational efficiency and robustness. The IEM model represents the micromixing process. The numerical results obtained in this study are precisely compared with experimental data in terms of unconditional means and conditional means for scalar field including temperature and species mass fraction.

• Journal of the Korean Mathematical Society
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• v.58 no.5
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• pp.1147-1180
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• 2021

By considering the polynomial function 𝜙_car(z) = 1 + z + z²/2, we define the class 𝓢^*_car consisting of normalized analytic functions f such that zf'/f is subordinate to 𝜙_car in the unit disk. The inclusion relations and various radii constants associated with the class 𝓢^*_car and its connection with several well-known subclasses of starlike functions is established. As an application, the obtained results are applied to derive the properties of the partial sums and convolution.