• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.71-74
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• 2002

In this study, resonant characteristics of $Pb_{0.88}(La_{0.6}Nd_{0.4})_{0.08}(Mn_{1/3}Sb_{2/3})_{0.02}Ti_{0.98}O_3$ ceramics were investigated with the variations of electrode radius size for manufacturing the best 30MHz SMD type ceramic resonator with the size of $3.7{\times}3.1{\times}0.255mm^3$. Physical properties were proper for appling for 30MHz SMD type ceramic resonator. In third overtone thickness vibration mode, with increasing electrode radius size, resonant resistant($Z_r$) was decreased gradually. Mechanical quality factor($Q_{mt3}$) and dynamic range(D.R) showed the maximum value of 2,283, 47.1dB respectively, at 0.74mm electrode radius size.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.156-156
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• 2000

The piezoelectric properties and the doping effect for $0.95Pb(Zr_xTi_{l-x})O_3+0.O5Pb(Mn_{1/3}Nb_{2/3})O_3$compositions were studied. Also, the heat generation and the change of electromechanical characteristics, the important problem in practical usage, were investigated under high electric field driving. As a experiment results under low electric field, the value of $k_p$ and ${\varepsilon}_{33}^T$ were maximized, but $Q_m$ was minimized $(k_p=0.57, Q_m=1550)$ in the composition of x=0.51. In order to increase the values of $Q_m$, $Nb_2O_5$ was used as a dopant. As the result of that, the grain size was suppressed and the uniformity of grain was improved. Also, the values of $k_p$ decreased, and the values of $Q_m$ increased with doping concentration of $Nb_2O_5$ . As a experiment results under high electric field driving, when vibration velocity was ower than 0.6[m/s], the temperature increase was 20[℃], and the change ratio of mechanical quality factor was less than 10[%]. So, its electromechanical characteristics was very stable. Conclusively, piezoelectric ceramic composition investigated at this paper is suitable for application to high power piezoelectric devices.

• Communications of the Korean Mathematical Society
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• v.36 no.1
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• pp.51-62
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• 2021

Variational method has played an important role in solving problems of uniqueness and existence of the nonlinear works as well as analysis. It will also be extremely useful for researchers in all branches of natural sciences and engineers working with non-linear equations economy, optimization, game theory and medicine. Recently, the existence of infinitely many weak solutions for some non-local problems of Kirchhoff type with Dirichlet boundary condition are studied [14]. Here, a suitable method is presented to treat the elliptic partial derivative equations, especially (p(x), q(x))-Laplacian-like systems. This kind of equations are used in the study of fluid flow, diffusive transport akin to diffusion, rheology, probability, electrical networks, etc. Here, the existence of infinitely many weak solutions for some boundary value problems involving the (p(x), q(x))-Laplacian-like operators is proved. The method is based on variational methods and critical point theory.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.106-112
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• 2003

A combined discharge type ozonizer was designed and manufactured. The increase or decrease of temperature greatly influences the characteristics of ozone concentration ( $O_{3con}$), ozone generation ( $O_{3g}$) and ozone yield ( $O_{3Y}$) of a discharge type ozonizer. The characteristics of ozone concentration, ozone generation and ozone yield rate were investigated by varying the gas flow rate (Q), the discharge power ( $W_{d}$) and the temperature (T). At T=25[$^{\circ}C$] the values of $O_{3con}$ were found as 5632, 4200, 2500 and l800[ppm] at Q = 1, 2, 4 and 6[l/min] respectively. At the same temperature the corresponding values of $O_{3g}$ were found as 662, 988, 1176 and l270[mg/h] and those of $O_{3Y}$ were found as 67, 102, 119 and 135[g/kWh] respectively. When the temperature is decreased to -50[$^{\circ}C$], the values of $O_{3con}$ were found as 9000, 6700, 4000 and 2800[ppm] respectively at Q = 1, 2, 4 and 6[l/min]. At the same value of temperature the corresponding values of $O_{3g}$ were found as 1220, 1576, 1882 and 2050[mg/h] and those of $O_{3Y}$ were found as 120, 159, 188 and 202[g/kWh] respectively. Hence as the temperature was decreased from 25 to -50[$^{\circ}C$], the efficiencies of ozone generation were increased by 79, 55, 58 and 49[%] respectively at Q = 1, 2, 4 and 6[l/min].]. 6[l/min].].

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.6 no.3
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• pp.264-269
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• 2006

This paper presents the strategy for searching a hidden object in an unknown area for using by multiple distributed autonomous robotic systems (DARS). To search the target in Markovian space, DARS should recognize th ε ir surrounding at where they are located and generate some rules to act upon by themselves. First of all, DARS obtain 6-distances from itself to environment by infrared sensor which are hexagonally allocated around itself. Second, it calculates 6-areas with those distances then take an action, i.e., turn and move toward where the widest space will be guaranteed. After the action is taken, the value of Q will be updated by relative formula at the state. We set up an experimental environment with five small mobile robots, obstacles, and a target object, and tried to research for a target object while navigating in a un known hallway where some obstacles were placed. In the end of this paper, we present the results of three algorithms - a random search, an area-based action making process to determine the next action of the robot and hexagon-based Q-learning to enhance the area-based action making process.

• Journal of IKEEE
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• v.25 no.4
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• pp.644-649
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• 2021

Self-Imitation Learning is a simple off-policy actor-critic algorithm that makes an agent find an optimal policy by using past good experiences. In case that Self-Imitation Learning is combined with reinforcement learning algorithms that have actor-critic architecture, it shows performance improvement in various game environments. However, its applications are limited to reinforcement learning algorithms that have actor-critic architecture. In this paper, we propose a method of applying Self-Imitation Learning to Deep Q-Network which is a value-based deep reinforcement learning algorithm and train it in various game environments. We also show that Self-Imitation Learning can be applied to Deep Q-Network to improve the performance of Deep Q-Network by comparing the proposed algorithm and ordinary Deep Q-Network training results.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.218-219
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• 2002

Recently, RF lumped-element devices are demanded strongly in application of hand-held mobile communication equipments. Many workers have been reported RF integrated inductor as well as air cores. In order to achieve the high Q value, they removed backside of substrate by micro machining process [1] and also another MEMS-like approach such as levitated structure [2]. These approaches are capable of suppressing the parasitic effects, but low reproducibility and high cost problems remain. (omitted)

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.365-369
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• 2015

This paper investigates the dependency of the critical content for electrical conductivity of carbon powder-filled polymer matrix composites with different matrixes as a function of the carbon powder content (volume fraction) to find the break point of the relationships between the carbon powder content and the electrical conductivity. The electrical conductivity jumps by as much as ten orders of magnitude at the break point. The critical carbon powder content corresponding to the break point in electrical conductivity varies according to the matrix species and tends to increase with an increase in the surface tension of the matrix. In order to explain the dependency of the critical carbon content on the matrix species, a simple equation (${V_c}^*=[1+ 3({{\gamma}_c}^{1/2}-{{\gamma}_m}^{1/2})^2/({\Delta}q_cR]^{-1}$) was derived under some assumptions, the most important of which was that when the interfacial excess energy introduced by particles of carbon powder into the matrix reaches a universal value (${\Delta}q_c$), the particles of carbon powder begin to coagulate so as to avoid any further increase in the energy and to form networks that facilitate electrical conduction. The equation well explains the dependency through surface tension, surface tensions between the particles of carbon powder.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.21-25
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• 2009

By using Si CMOS process, small RFID tag antenna were fabricated on Si substrate and their electrical properties were evaluated. Firstly, tag antenna pattern and the electromagnetic properties were simulated with HFSS. The frequency was 13.56 MHz, the line-width and line-gap were modeled in the range of $50{\sim}200{\mu}m$. S parameters, SRF, and Q value were calculated from geometry. When the line-width and line-gap were $100{\mu}m$ and $100 {\mu}m$, respectively and the loop-turn was 10, the SRF was 80 MHZ and the Q value was ca. 9. When the microstrip antenna pattern of aluminum $2{\mu}m$ was fabricated by using DC sputtering, Vpp of ca. 4.3 V was obtained when the reader and tag were closely contacted.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.623-628
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• 2007

This paper presents the new power line coupler which is applicable to spread spectrum power line communications. The proposed coupler maintains the adequate value of a capacitor between the transmitter mode and the receiver mode using a switch. In the transmit mode, the relatively high value of the capacitor is chosen to minimize the attenuation of transmitted signals. In the receiver mode, the value of the capacitor is chosen to be small enough so that the coupler attenuates power line noises. This coupler reduced the magnitude distortion due to having a high Q value and the power consumption caused by the AC current flowing into the capacitor. The simulation and measurement results show the improved performance in the transmitter and receiver mode, respectively.