• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.393-396
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• 1996

This paper studies electrostatically suspended induction motors (ESIM). The ESIM possesses the rotating ability of an ordinary electrostatic induction motor, in addition to providing contactless support by electrostatic suspension. To accomplish these two functions, a feedback control strategy and the operating principle of an ordinary electrostatic induction motor are used. The stator possesses electrodes which exert the electrostatic forces to the rotor and are divided into a part responsible for suspension and one for rotation. Two rotor types are utilized: a polished glass disk without any surface treatment, and a polished glass disk covered with a thin layer of conductive material (ITO layer) on only one side. In this paper, the principle of the ESIM is described, followed by stator electrode design, experimental apparatus, control strategy for stable suspension. Experimental results show that the glass disk has been rotated with a speed of approximately 70 rpm while being suspended stably at a gap length of 0.3 mm.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.267-270
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• 1996

This paper reports about the successful suspension of a glass plate by electrostatic forces. In order to implement a stable suspension, the electrostatic forces exerted on the glass plate are actively controlled on the basis of the gap lengths between the glass plate and the stator electrodes. In this paper, the dynamic model of the suspension system and the influence of the resistivity of glass on the system stability are described, followed by stator electrode design, the experimental apparatus and a stabilizing controller. Experimental results show that the glass plate can be suspended at a gap length of about 0.3 mm. The influence of air humidity on the suspension initiation time, and the lateral dynamic characteristic are also described.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.401-404
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• 1996

A new method for the electrostatic suspension of disk-shaped objects is proposed which is based on a switched-voltage control scheme. It operates according to a relay feedback control and deploys only a single high-voltage power supply capable of delivering a dc voltage of positive and/or negative polarity. In addition to the unique feature that no high-voltage amplifiers are needed, this method provides a remarkable system simplification relative to conventional methods. It is shown that despite the inherent limit cycle property of relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping. In this paper, the functional principle of the switched voltage control scheme, numerical analysis, stator electrode design, and a nonlinear dynamic model of the suspension system are described. Experimental results will be presented for a 4-inch silicon wafer that clearly reveal the capability of the proposed control structure to suspend the wafer stably at an airgap length of 50 .mu.m.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.336-336
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• 2016

We have investigated magneto-transport properties in a MoS2 lateral spin-valve structures for different ferromagnetic CoFe electrode shapes and MoS2 channel lengths. For these devices, high quality and large-scale MoS2 thin films were synthesized through sulfurization of epitaxial MoO3 films and these sulfurized-MoO3 thin films properties are in good agreements with measurements on exfoliated MoS2 film. Magneto-transport measurements show a clear rectangular magnetoresistance signal of 0.16% and a spin polarization of 0.00012%. By using the one-dimensional spin diffusion equation, we extracted the spin diffusion length and coefficient, finding them to be 12 nm and $1.44{\times}10-3cm2/s$, respectively. These small values of magnetoresistance and spin polarization could be enhanced by appeasement of conductivity mismatch between the ferromagnet and semiconductor interface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.565-568
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• 2002

Welding variables and conditions in gas metal arc welding (GMAW) effect on the weld quality and productivity, extensive research efforts have been made to analyze the welding variables and conditions. In this study dynamic behavior of GMAW system is investigated using the characteristic equations of the power supply, wire and welding arc. Characteristic equation of wire is modified to include the effect of droplets attached at the electrode tip. The dynamic characteristics of arc length, current, voltage with respect to the step, ramp inputs of CTWD was simulated, seam tracking procedure using arc sensor was simulated with variable V-Groove geometries and weaving frequencies. From results of simulation, some predictions about dynamic characteristics of GMAW and welding process are available. The proposed simulator and results appear to be utilized to determine the proper welding conditions, to be improved by considering power supply dynamic characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.123-130
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• 1995

This study presents model synthesis and performance investigation of a new brake system using electro-rheological(ER) fluids. Field-dependent Bingham properties characterized by non-zero yield stresses of the ER fluids are experimentally distilled. These properties are then incorporated with the governing equation of the proposed brake system which features design simplicity, fast response and salient controllability. After analyzing system performance with respect to design parameters such as electrode gap and length, an appropriate size of the brake is designed and fabricated. Both simulation and experimental works are undertaken in order to determine the feasibility and efficiency of the proposed brake system. The system performances are justified by evaluating field-dependent braking torques as well as braking times.

• Rapid Communication in Photoscience
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• v.3 no.4
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• pp.67-69
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• 2014

Bis(2-thienyl)-diketopyrrolopyrrole having two $Zn^{II}$-cylcens (DPPCy) was synthesized. DPP-aggregates were constructed by self-organization of DPPCy and $dT_n$-DNAs. In the presence of L-ascorbic acid as an electron sacrifice reagent, the DPP aggregates immobilized on a gold electrode exhibit good anodic photocurrent responses as well as cathodic photocurrent responses in the presence of methyl viologen. The anodic photocurrent responses depend on the DNA lengths because of the formation of uniform DPP-aggregates corresponding to the DNA lengths. The present results show that photocurrent responses of the DPP-aggregates can be controlled by DNA lengths and electron sacrifice reagents.

• Transactions on Electrical and Electronic Materials
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• v.6 no.4
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• pp.173-176
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• 2005

A new $MoO_3$ based microsensor with low power consumption was presented. Typical size of sensor was 5mm in width and 8mm in length. As a sensitive electrode, $MoO_3$ was successfully fabricated by IC technology on pyrex glass of $250{\mu}m$ in thickness. After annealing at $550^{\circ}C$ for 3hrs, the film was fully crystallized and demonstrated as pure $MoO_3$ structure. The grain size of $MoO_3$ was plat like and typical size was about $1{\mu}m$. Based on the results of sensitivity measurement, $MoO_3$ microsensor shows especially high selectivity to $H_2$ reducing gas atmosphere. The applied heater power was lower than 0.5 Watt.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.292-295
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• 2005

Variable optical attenuators (VOA) made of low-loss fluorinated polymers are demonstrated which shows a low operating power less than 30 mW due to the superior thermo-optic effect of polymer material and a low insertion loss less than 1.0 dB by incorporating highly fluorinated polymers to reduce the absorption loss at 1550 nm. An attenuator-integrated low-crosstalk polymeric digital optical switch (DOS) is also demonstrated. The switch and attenuator shares a single connected electrode which is controlled by a single current source. Due to the simple structure of the integrated attenuator, the device length is reduced to 1 cm so as to provide low insertion loss of 0.8 and 1.1 dB for 1300 and 1550 nm, respectively. The attenuator radiates remained optical signal on the switch-off branch in order to decrease the switching crosstalk to be less than -70 dB with an applied electrical power of 200 mW.

• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.10-18
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• 2006

This article is concerned with the overview of the activated carbon fibers. Firstly, this review provides a comprehensive survey of the overall processes for the synthesis of the activated carbon fibers from the carbonaceous materials. Subsequently, the physicochemical properties such as pore structures and surface oxygen functional groups of the activated carbon fibers were discussed in detail. Finally, as electrochemical applications of the activated carbon fibers to electrode materials for electric double-layer capacitor (EDLC), the electrochemical characteristics of the activated carbon fiber electrodes and the various methods to improve the capacitance and rate capability were introduced. In particular, the effect of pore length distribution (PLD) on kinetics of double-layer charging/discharging was discussed based upon the experimental and theoretical results in our work. And then we discussed in detail the applications of the activated carbon fibers to adsorbent materials for purification of liquid and gas.