• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.04a
• /
• pp.74-75
• /
• 2006

We have investigated dielectric properties depending on temperature in organic light-emitting diodes using 8-hydroxyquinoline aluminum ($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric properties of organic light-emitting diodes using characteristics of impedance. he Impedance characteristics was measured complex impedance Z and phase $\theta$ in the temperature range of 10 K to 300 K. We obtained complex electrical conductivity, dielectric constant and loss tangent ($tan{\delta}$) of the device at room temperature. From these analyses, we are able to interpret a conduction mechanism and dielectric properties contributed by an interfacial and orientational polarization.

• Journal of Hydrogen and New Energy
• /
• v.33 no.3
• /
• pp.226-231
• /
• 2022

Power converter are usually equipped for fuel cell power generation system to connect alternating current (AC) electric power grid. When converting direct current (DC) of fuel cell power source into AC, the power converter has a frequency ripple, which affects the fuel cell and the grid. Therefore, an equivalent circuit having dynamic characteristics of fuel cell power, for example, impedance, is useful for designing an inverter circuit. In this study, the current, voltage and impedance characteristics were calculated through fuel cell modeling and validated by comparing them with experiments. The equivalent circuit element values according to the current density were formulated into equations so that it could be applied to the circuit design. It is expected that the process of the equivalent circuit modeling will be applied to the actual inverter circuit design and simulated fuel cell power sources.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.6 no.5
• /
• pp.731-738
• /
• 2002

In this paper, we analyzed a medium voltage power line characteristics considering the skin effect for high speed data transmission. Medium power-line characteristics impedance was obtained by the S-parameter method which is used in high frequency band. Power line channel characteristics was measured using it designed coupler, it is a wide band coupler between medium powe-line and measurement system. Attenuation characteristics along the frequency was decreased linearly when skin effect was considered but attenuation characteristics along the frequency was decreased linearly when skin effect was not considered. Impedance was showed lower and lower in proportional to frequency, and variation was decreased in proportional to frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.3
• /
• pp.286-291
• /
• 2013

In this paper, a compact rectenna system is designed using a circular sector antenna with harmonic-rejecting characteristics and a direct impedance matching method. The system is designed with bandpass filtering performed by the harmonic-rejection of the circular sector antenna and without impedance matching circuit for the diodes by the direct impedance matching technique. Therefore, while the rectifying circuit of the proposed system can be implemented without a bandpass filter and a impedance matching circuit, it is integrated on the back side of the antenna using precise fabrication techniques for coaxial feedings without degrading the system performances corresponding to the feeding points. From the experimental results, the optimized rectenna system has presented excellent performances of a conversion efficiency of more than 52 % and a conversion voltages of more than 1.5 V at 2.5 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.4
• /
• pp.661-668
• /
• 2012

A coaxial-cable impedance transformer that can be used in high power and wideband frequency range is an arbitrary impedance transformation ratio by an additional coaxial cable. The coaxial-cable impedance transformer to be 50-${\Omega}$ to 25-${\Omega}$ impedance transformation ratio is easily operated an wideband power divider by connecting two 50-${\Omega}$ lines at 25-${\Omega}$ impedance point. This wideband power divider has a poor output matching characteristic and a poor isolation characteristic between two output ports. In this paper, it proposes a coaxial-cable power divider to be a good output matching and isolation characteristics as it uses the singly terminated filter design theory. The odd-mode operation characteristic of the suggested power divider to use singly terminated low pass filter coefficient due to matching order and ripple value is examined by ADS program. And, it fabricates and measures the operation characteristic of 2-way power divider with 2nd-order and 4th-order matching circuit.

• Journal of Korea Society of Industrial Information Systems
• /
• v.18 no.6
• /
• pp.9-16
• /
• 2013

Bio-impedance measurement system(BMS) is non-invasive and easy to implement a measurement method that allows determining the water content of a patient. The measurement conditions, the hardware specifications and the configurations of BMS devices must be well chosen in order to get correct and reproducible results. BMS was then conducted for the limbs and the thoracic using a lock-in amplifier and LabView control system with a frequency range of 1kHz-100kHz. From both the measurement data and the simulation results, we verified that the parameters in the proposed equivalent model and the trend of impedance variation according to the multi-frequency of applied current source are similar to those of human body. We believe that the real-time BMS developed in this study is highly reliable and applicable to the research on the clinical characteristics of the human being's impedance.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.466-469
• /
• 2004

In this paper, we improve the matching impedance of antennas by inserting parasitic slots on the ground plane of right-angle triangular slot antennas. The designed antennas characteristics are analyzed by using Finite Different Time Domain (FDTD) method, the specific design frequency is 10 GHz and match impedance is 50 ohms. Simulation results show that the efficient of return loss and radiation patterns are improved and enhance. In this case, the right-angle triangular slot antennas with parasitic slots have matching impedance better than antennas without parasitic slots.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.8 no.1
• /
• pp.38-43
• /
• 1988

Microstructure and mechanical properties of most steels change by heat treat treatment. Such variation of stucture and properties of steel cause an impedance change on electromagnetic induction coil. The objective of this study is, by searching the relationship between the mechanical property or microstructural changes and impedance value of induction coil, to examine the applicablity of a monitoring the heat treated condition of products nondestructively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.12 no.3
• /
• pp.89-98
• /
• 1998

Some analytic results for a solenoid eddy current coil to test nondestructive conducting materials are described in this paper. Normalized impedance of solenoid coil encircling cylindrical conducting tubes or tow-conductor rods is analyzed. Electrical and magnetic properties such as conductivity, permeability and exciting frequency as well as the geometric ones of fill factor or radius ratio of the conductor are also considered. Impedance characteristics of the models obtained by numerical analysis are examined. Validation of the model is carried out using several samples of non-ferromagnetic conducting tubes and 2-conductor rods.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.462-465
• /
• 1995

In this research a 2-dimensional motion producer based on two linear motors was developed. When the tester provides some motion through the level attached to the upper moving part of the motion producer, it provides the arbitrary intertia, damping and stiffness characteristics without actual change in physical structure of the motion producer. That is, the active impedance is implemented by controlling input currents supplied to the linear motors. A PID controller with feedforward loop was used to control the currents and pre-processing of input velocity and accleration singals from the encoder and the current singnal from the motor driver circuit are conducted to improve the performance.