• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.107-111
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• 2013

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region (dead band) due to the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference, and an angular increment is not detected. This problem can be overcome by mechanically dithering the gyroscope. This paper presents the design method of mechanical dither by the theoretical considerations and the verification of the theoretical equations through FEM applications. As a result, comparing to the past result, the maximum prediction error of resonant frequency was within 3 percent and peak dither rate was within 5 percent. It was found that the theoretical equations can be feasible for the mechanical performance of dither.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.1-9
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• 2010

An LED driving and control circuit has been developed. The LED driver has a new PWM circuit for current control of LED columns with dimming, current and thermal control, and communication functions. The PWM circuit is composed of two ring oscillator and one counter which can be constructed using basic digital logic components. In addition, it has the functions of remote control mode such as ON, OFF, emergency and power saving modes by the serial communication. The PWM generator and control circuit have been designed and fabricated 0.35[${\mu}m$] Magnachip/Hynix digital IC fabrication process. The LED driving and control board using the developed chip is fabricated and tested successfully.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.3
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• pp.379-388
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• 1998

In this paper we propose a DMR-II shared-medium access control protocol which was developed for the ATM access network users to support isochronous and non-isochronous traffics simultaneously under the bandwidth sharing environment, and describe its architecture and operation principles. The DMR-II protocol uses the slotted-ring topology, and gives the higher transmission priority to the isochronous traffic than the non-isochronous traffic. To support the isochronous traffic it uses the slot reservation mechanism, and maintains the delay variation of the isochronous traffic beyond the threshold value by using the blocking mechanism whenever the total user traffic overflows the network's bandwidth limitation. for the non-isochronous traffic the DMR-II protocol lets all the nodes to have fair transmission chances by using the reset mechanism based on the window counter scheme.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.48-54
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• 1995

A new propeller open water testing device is developed and tested in a tow tank. The devised dynamometer consists of a torque measuring part, a thrust measuring part and a driving motor with an RPM counter. Torque is designed to be measured directly from the torsion of the structure holding the motor by using strain gauges and, consequently, conventional slip ring is removed. Also, in order to make the device fit in relatively small model ships, the weight and the size of the whole integrated structure are reduced in various ways. The developed tester is proved to be easily utilized in small circulating water channel experiments and is believed to have provided us with essential information for future design of various types of conventional or object oriented force measuring device.

• Bulletin of the Korean Chemical Society
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• v.10 no.4
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• pp.349-352
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• 1989

Two Crystal structures of fully dehydrated partially magnesium exchanged zeolite A, stoichiometries of $Mg_{2.5}Na_7-A$ (a = 12.251 (1) ${\AA}$) and $Mg_{1.5}Na_9-A\; (a\;=\;12.214(1)\;{\AA})$ per unit cell, have been determined from the 3-dimensional X-ray diffraction data gathered by counter methods. All structures were solved and refined in the cubic space group Pm3m at 21(1)$^{\circ}C$. The structures of the dehydrated $Mg_{2.5}Na_7-A$ and $Mg_{1.5}Na_9-A$ were refined to yield the final error indices $R_1$ = 0.042 and $R_2$ = 0.049 with 318 reflections, and $R_1$ = 0.034 and $R_2$ = 0.032 with 252 reflections, respectively, for which I > $3{\sigma}(I)$. Both structures indicate that $Mg^{2+}$ ions are coordinated by three framework oxygens and the angle substended at $Mg^{2+}$ ions, O(3)-Mg(1)-O(3) is ca. $120^{\circ}$, close to the idealized trigonal planar value. $Mg^{2+}$ ions preferentially occupy 6-ring sites and $Na^+$ ions occupy 8-ring sites when total number of cations per unit cell is more than 8.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.6
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• pp.625-630
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• 2014

Asynchronous digital circuits working in military and space environments are often subject to the adverse effects of radiation faults. In this paper, we propose a new hardening technique against radiation faults. The considered digital system has the structure of DMR (Double Modular Redundancy), in which two sub-systems conduct the same work simultaneously. Based on the output feedback, the proposed scheme diagnoses occurrences of radiation faults and realizes immediate recovery to the normal behavior by overriding parts of memory bits of the faulty sub-system. As a case study, the proposed control scheme is applied to an asynchronous dual ring counter implemented in VHDL code.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.26-33
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• 2002

One characteristic of Fine-Blanking is that the size and the direction of stress and strain are very complex in the plastic flow according to the condition of blanking. Especially, they are affected by the clearance of punch and die, by the force of blanking holder and by the force of counter punch. The purpose of this research is to how the deformation behavior in shear zone more clearly, based on Green & Cauch's large deformation theory. The deformation behavior and cracks were investigated in each step of shear, according to punch penetration increase, the use of V-indenter ring and the hardness of materials. This research found that the transforming behavior was the same as pure discretion and the cracks could be prevented when hardness is low.

• Journal of Environmental Science International
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• v.9 no.5
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• pp.393-396
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• 2000

Packing tower has been used in the chemical industry and the protection of environment for a long time. In the view of environmental protection purification of exhaust gas can be performance effective by gas absorption in counter-current packing tower. In this study characteristics of hydraulic and mass transfer were investigated in D. $0.3m {\times} H. 1.4m$ packing tower with 50mn plastic Hiflow-ring. This study was carried out "Test systems were experimented in conditions of Air, $Air/H_2O. NH_3-Air/H_2O, NH_3-Air/H_2O-H_2SO_4$ and $SO_2-Air/H_2O-NaOH$ under steady state" The extent of test included dry and wetting pressure drop physical law separation efficiency and hold-up as function of gas and liquid load.quid load.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.100.3-100
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• 2001

This article deals with the development of a mathematical model for the finishing polycarbonate polymerization process using a horizontal rotating disk-ring reactor with counter-current gas sweeping and the performance analysis of the reactor system by using the model. Here we intend to propose a model describing the reactor system consisting of two phases, in which by-product phenol is removed from the polymer of high molecular weight compatible with the products of commercial grades. The vapor phase is represented by a tanks-ln-series model while the polymer melt phase is regarded as a plug flow reactor.

• Bulletin of the Korean Chemical Society
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• v.20 no.11
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• pp.1303-1308
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• 1999

Conducting poly(3,4-ethylenedioxythiophene) (PEDT) films with metalloporphyrins incorporated as the counter ions were prepared by electropolymerization of the monomer in the presence of metal-tetra(sulfonatophenyl) porphyrin anions. Cathodic reduction of oxygen on the resulting conducting polymer films was studied. The overpotential for O2 reduction on electrodes with cobalt-porphyrin complex was significantly smaller in acidic solutions than on gold. In basic solutions, the overpotential at low current densities was close to those on platinum and gold. Polymer electrode with Co-complex yielded higher limiting currents than with Fe-complex, although the Co-complex polymer electrode was a poorer electrocatalyst for O2 reduction in the activation range of potential than the Fe counterpart. From the rotating ring-disk electrode experiments, oxygen reduction was shown to proceed through either a 4-electron pathway or a 2-electron pathway. In contrast to the polypyr-role-based electrodes, the PEDT-based metalloporphyrin electrodes were stable with wider potential windows, including the oxygen reduction potential. Their electrocatalytic properties were maintained at temperatures up to 80℃ in KOH solutions.