• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.129-132
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• 2004

This paper describes the design, fabrication and characteristics of a piezoelectric valve using MCA(Multilayer ceramic actuator). The MCA valve, which has the buckling effect, consists of three separate structures; MCA, a valve actuator die and an a seat die. The design of the actuator die was done by FEM modeling and displacement measurement, respectively. The valve seat die with 6 trenches was made, and the actuator die, which is driven to MCA under optimized conditions, was also fabricated. After Si-wafer direct bonding between the seat die and the actuator die, MCA was also anodic bonded to the seat/actuator die structure. PDMS sealing pad was fabricated to minimize a leak-rate. It was also bonded to seat die and SUS package. The MCA valve shows a flow rate of 9.13 sccm at a supplied voltage of 100 V with a 50 % duty cycle, maximum non-linearity was 2.24 % FS and leak rate was $3.03{\times}10^{-8}\;pa{\cdot}m^3/cm^2$. Therefore, the fabricated MCA valve is suitable for a variety of flow control equipment, a medical bio-system, automobile and air transportation industry.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.7
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• pp.782-787
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• 2004

Superconducting flux flow transistor (SFFT) is based on a control of the Abrikosov vortex flowing along a channel. The induced voltage by moving of the Abrikosov vortex in an SFFT is greatly affected by the thickness, the width, and the length of channel. In order to fabricate a reproducible channel in the SFFT, we studied the variation of the critical characteristics of ${YBa}_2{Cu}_3{O}_7-\delta(YBCO)$ thin films with the etching time using ICP (Inductively coupled plasma) system. From the simulation, it was certified that the vortex velocity was increased in a low pinning energy at channel width 0,5 mm. The surfaces of YBCO thin film were etched by ICP etching system. We observed the etched channel surfaces by AFM (Atomic Force Microscope) and measured the critical current density with etching time. As a measured results, the etching thickness of channel should be optimized to fabricated a flux flow transistor with specified characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.259-262
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• 2003

Superconducting flux flow transistor(SFFT) is based on a control of the Abrikosov vortex flowing along a channel. The induced voltage by moving of the Abrikosov vortex in SFFT is greatly affected by the thickness and width, of channel. In order to fabricate a reproducibility channel in SFFT, we have researched the variation of the critical characteristics of YBCO thin films with the etching time using ICP(Inductively coupled plasma) system. It was certified that the velocity of vortex decreased with increasing the width of channel and was saturated faster in low bias from a simulation. An etching mechanism of YBCO thin films by ICP system was also certified by AFM(Atomic Force Microscope) and by measuring the critical current density with etching time. As measurement result, we could analyze that we should optimize the etching thickness of channel part to construct a flux flow transistor with desired characteristics.

• Corrosion Science and Technology
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• v.18 no.4
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• pp.148-153
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• 2019

Pure nickel with a thickness of 1 mm was plated on type 304 stainless steels and low alloy steels (JIS G3131 SPHC) by electrolytic plating method in a circulating plating bath. Plating performance, mechanical properties, and surface characteristics were evaluated in terms of pretreatment process, anode material, pH, current density, and flow rate of the plating solution. Addition of hydrochloric acid during pre-treatment process improved the adhesion performance of plating. To improve plating efficiency, it is desirable to use S-nickel rather than electrolytic nickel. The use of S-nickel was also confirmed to be desirable for maintaining the pH and concentration of the plated solution. The defect of the plating using S-nickel anode produced pit on the surface. However, it is believed that proper control can be obtained by increasing the flow rate. Internal stress and hardness values of electrolytic nickel plating according to current density need to be carried out with further studies.

• IE interfaces
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• v.11 no.2
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• pp.1-11
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• 1998

In this paper, a case study is introduced on the development on a production planning system for the efficient control of work-in-process material flows. A special attention has been given to the prevention of the shortage of the automobile-components at the auto-assembly lines and the dynamic adaptation of the production plan to the continuously changing environment. The expertise of the production planner is analyzed and transformed into the logic of the software developed.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.165-170
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• 2004

The purpose of this work was to assess and quantify the beneficial effects of long-term gas exchange, at varying frequencies, for the development of a vibrating intravascular lung assistance device (VIVLAD), for patients suffering from acute respiratory distress syndrome (ARDS). The experimental design and procedure have been applied to the construction of a new device for assessing the effectiveness of membrane vibrations. An analytical solution has been developed for the hydrodynamics of flow through a bundle of sinusoidally vibrated hollow fibers, with the intention of gaining insight into how wall vibrations might enhance the performance of the VIVLAD. As a result, the maximum oxygen transfer rate was reached at the maximum amplitude and through the transfer of vibrations to the hollow fiber membranes. The device was excited by a frequency band of 7Hz at various water flow rates, as this frequency was the 2nd mode resonance frequency of the flexible beam. 675 hollow fiber membranes were also bundled, within the blood flow, into the device.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.147-152
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• 2006

This paper presents the dynamic characteristics of MR impact damper for vehicle collision system. Various types of mechanism have been proposed for reduce transmitted force to vehicle chassis and finally protect occupants from injury. In the case of frontal collision, the bumper make main role of isolation material for collision attenuation. In this study, proposed bumper system composed of MR impact damper and structures. The MR impact damper is to adopted MR fluid which has reversible properties with applied magnetic field. MR fluid operates under flow mode with Bingham flow and bellows is used for generation of fluid flow. Mathematical model of MR impact damper incorporated with MR fluid is established. Field dependent damping force is investigated with time and frequency domain. The MR impact damper is then incorporated with vehicle crash system. The governing equation of motion of vehicle model is formulated considering occupant model. Dynamic characteristics of vehicle collision system investigated with computer simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.10
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• pp.1006-1012
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• 2010

The hot rolling process ranks the highest position for production in steel making process. The hot strip manufacturing processes consist of the reheating furnace, roughing and finishing mill and coiler. The reheating furnace heats the slab. The roughing and finishing mill produce the hot strip from slab. The hot strip quality mainly depends on finishing mill, which consists of 4-high 7 stands. The looper is installed between stands and is used for controlling the strip tension by the looper angle for better material flow. It is difficult to control the strip tension with the coupled looper system from interaction between the looper angle and strip tension. Too much deviation of strip tension severely affects the poor width quality of the hot strip. It is important to control simultaneously both the looper angle and strip tension with each of their target values. This paper proposes the fuzzy tension control, which is developed to minimize the width deviation of the hot strip by maintaining the proper strip tension between stands and to achieve the stable operation of the coupled looper system. The fuzzy tension control performance is compared with the conventional PID control by experimental results.

• Particle and aerosol research
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• v.12 no.1
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• pp.21-26
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• 2016

In order to realize In-line and convenient measurement for solid-gas two phase flows, Light Transmission Fluctuation (LTF) based on the random variation of transmitted light intensity, light scattering theory and cross-correlation method was presented for online measurement of particle size, concentration and velocity. The statistical relationship among transmitted light intensity, particle size and particle number in measurement zone was described by Beer-Lambert Law. Accordingly, the particle size and concentration were determined from the fluctuation signal of transmitted light intensity. Simultaneously, the particle velocity was calculated by cross-correlation analysis of two neighboring light beams. By considering the influence of concentration variation in industrial applications, the improved algorithm based on spectral analysis of transmitted light intensity was proposed to improve measurement accuracy and stability. Therefore, the online measurement system based on LTF was developed and applied to measure pulverized coal in power station and raw material in cement plant. The particle size, concentration and velocity of powder were monitored in real-time. It can provide important references for optimal control, energy saving and emission reduction of energy-intensive industries.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.448-448
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• 2010

Magnetic random access memory (MRAM) has made a prominent progress in memory performance and has brought a bright prospect for the next generation nonvolatile memory technologies due to its excellent advantages. Dry etching process of magnetic thin films is one of the important issues for the magnetic devices such as magnetic tunneling junctions (MTJs) based MRAM. CoFeB is a well-known soft ferromagnetic material, of particular interest for magnetic tunnel junctions (MTJs) and other devices based on tunneling magneto-resistance (TMR), such as spin-transfer-torque MRAM. One particular example is the CoFeB - MgO - CoFeB system, which has already been integrated in MRAM. In all of these applications, knowledge of control over the etching properties of CoFeB is crucial. Recently, transferring the pattern by using milling is a commonly used, although the redeposition of back-sputtered etch products on the sidewalls and the low etch rate of this method are main disadvantages. So the other method which has reported about much higher etch rates of >$50{\AA}/s$ for magnetic multi-layer structures using $Cl_2$/Ar plasmas is proposed. However, the chlorinated etch residues on the sidewalls of the etched features tend to severely corrode the magnetic material. Besides avoiding corrosion, during etching facets format the sidewalls of the mask due to physical sputtering of the mask material. Therefore, in this work, magnetic material such as CoFeB was etched in an ICP etching system using the gases which can be expected to form volatile metallo-organic compounds. As the gases, carbon monoxide (CO) and ammonia ($NH_3$) were used as etching gases to form carbonyl volatiles, and the etched features of CoFeB thin films under by Ta masking material were observed with electron microscopy to confirm etched resolution. And the etch conditions such as bias power, gas combination flow, process pressure, and source power were varied to find out and control the properties of magnetic layer during the process.