• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.165-168
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• 2000

Improvement on the switching characteristic of IGBT by means of the uniform and local lifetime control is studied numerically using two-dimensional simulator, MEDICI. In the case of uniform lifetime control, the on-state and switching characteristics are simulated as a function of lifetime, and compared with the experimental results reported, which allows a relationship between dose of electron irradiation and controlled lifetime. In the case of local lifetime control, simulations are carried out by varying the position, width, and lifetime of the locally controlled region, and the results are compared with the characteristics for the case of the uniform lifetime control. The turn-off time of the device with an optimized locally controlled region is found to decrease from about $4.5\mus$ to 0.11$mutextrm{s}$ while the forward voltage drop increases from 1.37V to 2.61V in comparison with that for the uniform lifetime control.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.3
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• pp.269-276
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• 2006

Increasing requirements for the high quality of industrial robot performance made the vibration control issue very important because the vibration makes it difficult to achieve quick response of robot motion and may bring mechanical damage to the robot. This paper presents the vibration mechanism of an industrial robot which has flexible joints. The joint flexibility of the robot is modeled as a two-mass system and its dynamic characteristics are analysed. And some characteristics of the two-mass system, especially for the joint of industrial robots, such as disturbance, non-linearity and time-varying characteristics are studied. And finally, some considerations on controller design for the flexible joint of industrial robots are discussed.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.237-243
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• 2011

Thermal characteristics, such as diffusivity and temperature induced change in the fiber mode index of rotation sensing fiber coil are critical factors which determine the time varying, thermo-optically induced bias drift of interferometric fiber-optic gyroscopes (IFOGs). In this study, temperature dependence of the transient effect is analyzed in terms of the thermal characteristics of the fiber coil at three different temperatures. By applying an analytic model to the measured bias in the experiments, comprehensive thermal factors of the fiber coil could be extracted effectively. The validity of the model was confirmed by the fact that the extracted values are reasonable results in comparison with well known properties of the materials of the fiber coil. Temperature induced changes in the critical factors were confirmed to be essential in compensating the transient effect over a wide temperature range.

• Progress in Superconductivity and Cryogenics
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• v.1 no.2
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• pp.30-36
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• 1999

Superconductors are dissipative when exposed to time-varying magnetic fields. To analyze the AC characteristics of a superconductor, one usually needs to know magnetization curves of it. Good magnetization curves can be obtained only in homogeneous magnetic filed. In This paper, we report the setup and test results of a magnetization measurement system, which consists mainly of frequency-variable power supply and homeogenous magnet with 7-cm long air gap. Special emphasis are foused on the design and fabrication of the magnet, which aims to give background magnetic fields, and on the overall characteristics of the system.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.37-40
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• 2001

The semiconductor's design rule becomes more stringent, hence the silicon-dioxide etching technique is important issue. In this work we compared the etching characteristics of different three types of Plasma source, Normal ICP, magnetized ICP and E-IC $P^{TM}$. The E-IC $P^{TM}$ source shows higher etch rate at lower pressure and this is advantageous for the fine pattern process. The etching characteristics were varied with external magnetic field frequency at I-lCP and this is examined with Nanospe $c^{TM}$ and SEM. We designed Langmuir probe system for time resolved diagnosis. ion density of E-ICP is varying periodically with the applied external magnetic field frequencyquency

• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.24-28
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• 2008

Eddy current are induced when a nonmagnetic, conductive material is moving as the result of being subjected to the magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and conductor. Using this concept, eddy current damping can be used as a form of viscous damping. This paper investigated analytically and experimentally the characteristics of an eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of the eddy current damping is developed from electromagnetics and is verified from Maxwell program and experiments. From these comparisons, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies. In order to improve the prediction of the characteristics of an eddy current damping, the induced magnetic flux densities have to be considered in following researches.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.232-238
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• 2004

The dynamic characteristics of the current collection process of the high-speed railway are investigated through signals acquired during a test run. The signals are obtained from accelerometers, load cells, and strain gauges attached to various positions of the pantograph, and they are processed in time-and frequency-domains to obtain the dynamic characteristics. The main natural frequency of the pantograph is found to be 8.5Hz. There also are components at low frequencies varying linearly with the train speed. The contact frequency components above 20Hz is attenuated as they pass through the secondary suspension. The main frequency component of the load cell signal is found to be related with the rolling motion of the panhead generated by the stagger in the catenary.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.63-66
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• 1994

This paper describes the developed sensor for measuring the time-varying magnetic fields and presents the characteristics of the magnetic fields and presents the characteristics of the magnetic field generated by lighting a fluorescent lamp. The frequency bandwidth of magnetic field measurement system is kknown as 40 Hz∼100 kHz by means of calibration experiment. The magnetic field waveform which originates from the various lighting systems was measured and the frequency components were analyzed by fast Fourier transformation technique. The magnetic field generated during the operation of the fluorescent lamp mainly includes the odd harmonics, and in the case\ulcorner of push button switch and high frequency starter types the fast transient component is occurred in an instant of lighting.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.3 s.246
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• pp.255-261
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• 2006

Flow characteristics of DI water in a microchannel with a stenosis were investigated using .a micro PIV system with varying flow rate. The width and depth of the PDMS micro-channel were $100{\mu}m\;and\;50{\mu}m$, respectively. To Investigate flow characteristics in the micro-stenosis, the same experiment was carried out in a straight microchannel under the same flow rate. The measured mean velocity fields were almost symmetric with respect to the channel centerline. The experimental results are well agreed with the theoretical Hagen-Poiseuille profile. In the contraction part of the micro-stenosis, the oncoming flow is accelerated rapidly and the maximum velocity occurs at the throat, almost 4.99 time faster than that without the stenosis.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.83-86
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• 2021

In this paper, electric fields in electromagnetic reverberation chambers, which are used as a substitute facility for EM-free anechoic chambers, are analyzed. This paper focused on the 4-5 GHz band, which is expected to adversely affect equipment. To analyze the field uniformity inside the electromagnetic reverberation chamber, electric field strengths are sampled and finite-difference time-domain method was used for numerical analysis. Moreover, Quadratic residue diffuser was used to improve the characteristics of the electromagnetic reverberation chamber and the uniformity of the internal field strength. Standard deviation, tolerance characteristics, and partiality characteristics were compared while varying the aiming point of transmission antenna.