• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.3
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• pp.214-219
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• 2013

This paper proposes the robust high-gain observer based SOC estimatro for uncertain RC model of Li-Ion batteries. In general, RC battery model has inevitable uncertainties and it cause some negative effect to estimate the accurate SOC of Li-Ion batteries. The proposed estimator overcomes such weakness with two techniques; high-gain observer design technique and sliding mode control technique. A high-gain observer provides the robustness against model uncertainties to the proposed estimator. A sliding mode control technique helps the proposed estimator by reducing the side effect of adopting a high-gain observer such as peaking phenomenon and perturbation. The performance of the proposed estimator is verified by some simulation.

• Korean Journal of Human Ecology
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• v.22 no.1
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• pp.231-243
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• 2013

This study intends to suggest basic data for the activation of rural activities in dietary life education, through a survey of adolescents on rural activities in dietary life education. It was found that 63.2% of subject students had the experience of rural activities; and that as many as 35.2% among the students who experienced rural activities participated in the activities 5 times or more. And the survey showed that rural activities were led most frequently by a teacher in charge (37.9%), and rather rarely by a nutrition teacher (15.4%) or an expert in dietary life education (7.7%). As for food ingredients that adolescents experienced during rural activities, they were composed of easily available good cookers that are common in the Korean diet, and, among them, vegetables were experienced most, followed by cereals and fruits. On the other hand, as for food ingredients preferred by adolescents, it was found that boy students preferred meat, while girl students preferred fruits. And as for improvements in dietary life, it was found that making efforts to have good dietary habits had the highest score, which shows that rural activities contributed to the improvement in adolescents' dietary life. Therefore, given the fact that rural activities go some way towards improving adolescents' dietary life, it is advisable that more opportunities for experiencing rural activities be provided to adolescents in the future so as to help them have good dietary habits.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.45-49
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• 2001

We have investigated physical and electrical properties of the Hf $O_2$/HfS $i_{x}$/ $O_{y}$ thin film for alternative gate dielectrics in the metal-oxide-semiconductor device. The oxidation of Hf deposited directly on the Si substrate results in the H $f_{x}$/ $O_{y}$ interfacial layer and the high-k Hf $O_2$film simultaneously. Interestingly, the post-oxidation N2 annealing of the H102/H1Si70y thin films reduces(increases) the thickness of an amorphous HfS $i_{x}$/ $O_{y}$ layer(Hf $O_2$ layer). This phenomenon causes the increase of the effective dielectric constant, while maintaining the excellent interfacial properties. The hysteresis window in C-V curves and the midgap interface state density( $D_{itm}$) of Hf $O_2$/HfS $i_{x}$/ $O_{y}$ thin films less than 10 mV and ~3$\times$10$^{11}$ c $m^{-2}$ -eV without post-metallization annealing, respectively. The leakage current was also low (1$\times$10-s A/c $m^2$ at $V_{g}$ = +2 V). It is believed that these excellent results were obtained due to existence of the amorphous HfS $i_{x}$/ $O_{y}$ buffer layer. We also investigated the charge trapping characteristics using Fowler-Nordheim electron injection: We found that the degradation of Hf $O_2$/HfS $i_{x}$/ $O_{y}$ gate oxides is more severe when electrons were injected from the gate electrode.e electrode.e.e electrode.e.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2170-2174
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• 2010

The surfaces of $TiO_2$ and ZnO nanoparticles have been modified by gold (Au) nanoparticles by a reduction method in solution. Their interfacial electronic structures and optical absorptions have been studied by depth-profiling X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectroscopy, respectively. Upon Au-modification, UV-vis absorption spectra reveal a broad surface plasmon peak at around 500 nm. For the as-prepared Au-modified $TiO_2$ and ZnO, the Au $4f_{7/2}$ XPS peaks exhibit at 83.7 and 83.9 eV, respectively. These are due to a charge transfer effect from the metal oxide support to the Au. For $TiO_2$, the larger binding energy shift from that (84.0 eV) of bulk Au could indicate that Au-modification site of $TiO_2$ is different from that of ZnO. On the basis of the XPS data with sputtering depth, we conclude that cationic (1+ and 3+) Au species, plausibly $Au(OH)_x$ (x = 1-3), commonly form mainly at the Au-$TiO_2$ and Au-ZnO interfaces. With $Ar^+$ ion sputtering, the oxidation state of Ti dramatically changes from 4+ to 3+ and 2+ while that (2+) of Zn shows no discernible change based on the binding energy position and the full-width at half maximum (FWHM).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.870-875
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• 2011

The $(Na_{0.52}K_{0.44})(Nb_{0.9}Sb_{0.06})O_3-0.04dLiTaO_3$ (NKNS-LT) ceramics with various $Cu_2O$ concentration were prepared by the conventional solid state reaction method. The $Cu_2O$ content was varied in the range of 0.1~0.4 wt%. The effects of Cu on microstructure, crystallographic phase transition, and piezoelectric properties were investigated. The material with perovskite structure had a tetragonal phase (T1) when $Cu_2O$ concentration was less than 0.3 wt% and it transformed to another tetragonal phase (T2) when the $Cu_2O$ amount was greater than 0.3 wt%. The phase boundary between T1 and T2 phases appeared at around 0.3 wt% of $Cu_2O$ concentration. The piezoelectric properties were shown the maximum values at the composition of the phase boundary. The electro-mechanical coupling factor ($k_p$) was 0.42 and the piezoelectric charge constant ($d_{33}$) was 245 pC/N at the 0.3 wt% of $Cu_2O$ concentration.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.199-208
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• 2017

Lithium polymer batteries are used in energy storage systems (ESS), electric vehicles (EVs), etc. due to their high safety, fast charging and long lifecycle, and now they are used in agricultural drones. However, when overcharging and overdischarging, the lithium-polymer battery is destroyed in the gap structure in the lithium-ion battery and the battery life is reduced. In order to prevent overcharge and overdischarge, uneven cell voltage Cell balancing system is needed. In this paper, a fuzzy controller suitable for nonlinear systems is proposed by detecting the unbalanced cells by detecting the voltage difference between charging and discharging of each cell, and suggesting the applied cell balancing algorithm. In this paper, we have designed the cell balancing of the battery pack of agricultural drones by fuzzy control and it is designed for equal control between cells. As a final result, we checked whether cell balancing is good, and when there are two cells, Cell balancing was confirmed. We tested whether it could be used for other products. As a result, we confirmed that cell balancing is good regardless of the number of cells used.

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.100-105
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• 2001

An all solid-state thin film battery (TFB) was fabricated by growing, undoped and Pt-doped vanadium oxide cathode film ( $V_2$ $O_{5}$ ) on I $n_2$ $O_3$: Sn coated glass, respectively. Room temperature charge-discharge measurements based on Li/Lipon/ $V_2$ $O_{5}$ full-cell structure with a constant current clearly shows that the Pt-doped $V_2$ $O_{5}$ cathode film is superior, in terms of cyclibility. X-ray diffraction (XRD) results indicate that the Pt doping process induces a more random amorphous structure than an undoped $V_2$ $O_{5}$ film. In addition to its modified structure, the Pt-doped $V_2$ $O_{5}$ film has a smoother surface than the undoped sample. Compared to an undoped $V_2$ $O_{5}$ film, the Pt doped $V_2$ $O_{5}$ cathode film has a higher electron conductivity. We hypothesize that the addition of Pt alters electrochemical performance in a manner of making more random amorphous structure and gives an excess electron by replacing the $V^{+5}$. Possible mechanisms are discussed for the observed Pt doping effect on structural and electrochemical properties of vanadium oxide cathode films, which are grown on I $n_2$ $O_3$: Sn coated glass.

• Journal of Korean Society of Archives and Records Management
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• v.18 no.2
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• pp.29-59
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• 2018

The purpose of this study is to examine the management status of domestic presidential SNS records and to propose a management plan. Thus, the researchers examined cases of SNS records management in foreign countries, interviewed records officers in Presidential Archives, as well as conducted a status analysis of the presidential SNS records management status and the SNS accounts of former and current presidents. Based on the analysis, the current state of the domestic and international situations was analyzed. The researchers subsequently interviewed the staff in charge and found out what the problems in the current presidential SNS records management were. To solve the problems reflecting the characteristics of SNS records, a collection, management, and service plan was thus proposed. This study is meaningful in that it tried to discuss the management of the presidential SNS records and could be used as basic research of presidential SNS records.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.72-83
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• 2000

This paper presents the implementation of the position control system for 3 phase induction motor using reaching mode controller and neural networks. The reaching mode controller is used to bring the position error and speed error trajectories toward the sliding surface and to train neural networks at the first time. The structure of the reaching mode controller consists of the switch function of sliding surface. And feedforward neural networks approximates the equivalent control input using the reference speed and reference position and actual speed and actual position measured form an encoder and, are tuned on-line. The reaching mode controller and neural networks are applied to the position control system for 3 phase induction motor and, are compared with a PI controller through computer simulation and experiment respectively. The results are illustrated that the output of reaching mode controller is decreased and feedforward neural networks take charge of the main part for the control action, and the proposed controllers show better performance than the PI controller in abrupt load variation and the precise control is possible because the steady state error can be minimized by training neural networks.

• Journal of IKEEE
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• v.21 no.1
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• pp.66-69
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• 2017

In recent year, energy harvesting technologies from the ambient environments such as light, motion, wireless waves, and temperature again a lot of attraction form research community [1-5] due to its efficient solution in order to substitute for conventional power delivery methods, especially in wearable together with on-body applications. The drawbacks of battery-powered characteristic used in commodity applications lead to self-powered, long-lifetime circuit design. Thermoelectric generator, a solid-state sensor, is useful compared to the harvesting devices in order to enable self-sustained low-power applications. TEG based on the Seebeck effect is utilized to transfer thermal energy which is available with a temperature gradient into useful electrical energy. Depending on the temperature difference between two sides, amount of output power will be proportionally delivered. In this work, we illustrated a low-input voltage energy harvesting circuit applied discontinuous conduction mode (DCM) method for getting an adequate amount of energy from thermoelectric generator (TEG) for a specific wearable application. With a small temperature gradient harvested from human skin, the input voltage from the transducer is as low as 60mV, the proposed circuit, fabricated in a $0.6{\mu}m$ CMOS process, is capable of generating a regulated output voltage of 4.2V with an output power reaching to $40{\mu}W$. The proposed circuit is useful for powering energy to battery-less systems, such as wearable application devices.