• Journal of Institute of Control, Robotics and Systems
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• v.15 no.8
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• pp.792-797
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• 2009

This paper presents the evaluation of PID and fuzzy control logic for the lateral position control of a moving web in roll-to-roll (R2R) printed electronics. In addition, we report the implementation of computer simulation software that enables us to develop the control logic in a graphic user interface and to test the controller performance in 3D dynamic environment. A mathematical model of the web dynamics is described first to explain the lateral motion of a moving web. Based on the model, PID and fuzzy controllers are designed, and embedded in the simulation software. Under the simulation conditions for fabricating RFID antenna by R2R printing, the results indicate that the fuzzy controller shows a better performance and can be more suitable for R2R multi-layer printed electronics.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.9
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• pp.877-880
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• 2009

A curing process in post-printing section of R2R process is required for an electrical property of the printed pattern when devices such as RFID, Solar cell are printed. PEN as well as heat-stabilized PET which is used as a plastic substrate would be deformed at high temperature due to change of its elastic modulus. And crack in the printed pattern, which is on the plastic substrate is occurred due to the deformation of the substrate. The occurrence of crack causes electrical resistance to increase and the quality of the device to deteriorate. In case of RFID antenna, the range of reading distance is shortened as the electrical resistance of the antenna is increased. Therefore, the deformation of the plastic substrate, which causes the occurrence of crack, should be minimized by setting up low operating tension in R2R process. In low tension, slippage between a moving substrate and a roller would be generated when the operating speed is increased. And scratch would be occurred when slippage is generated due to an air entrainment, which is related to the thickness of the air film. The thickness of the air film is increased when operating speed is increased as shown by simulation based on mathematical model. The occurrence of scratch in conductive pattern printed by roll to roll process is a critical damage because it causes degradation or failure of electrical property of it.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.261-266
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• 1994

The objective of this study is to develop the expert system for R/C box culvert design. This program provided various functions to improve automatic design. The program is composed of five steps. The characteristics of each step are as follows; 1) Preprocessing Step, 2) Analysis Step, 3) View of Memberforce Step, 4) Postprocessing Step, 5) Printing of Design-Sheet Step. Finally, Expert System and Knowledge Database System is developed for the drawing of optimal R/C box-culvert design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.263-271
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• 2010

e-Printing is a new manufacturing technology for electronic products and is based on traditional printing technology. The electronic products require a large area to facilitate printing and to be economical. A gravure printing system that supports a roll to roll (R2R) manufacturing process can be used to reduce the cost and to achieve the required accuracy. Many factors such as drying method, drying temperature, tension,-printing velocity, ink viscosity, ink conductivity, pattern accuracy, and dot geometry influence the performance of printed electronics. These factors are closely interrelated. The optimum condition for printing must be determined to enhance the performance of the printed electronics. In this study, lines and areas are printed using a gravure printer with conductive ink under different conditions of the above mentioned factors. The results are analyzed to investigate the influence of various factors on the performance of the printed electronics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.465-466
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• 2011

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.107-108
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• 2000

We propose the method which is possible to fabricate the electrodes with the fine pattern and low resistance by photolithography and electroplating. The widths of pattern fabricated were 30, 50, 70 and 100um and the thickness could be up to $10{\mu}m$. The resistivity of the copper electrode electroplated was below $2.0{\mu}{\Omega}$ cm which is about half of photosensitive silver electrode. Dielectric layer was coated on the electrodes by screen printing and the pores harmful to the discharge were not formed after heat treatment. In the viewpoint of resistance and patterning, this method has much higher potential for large area display than other methods like screen printing, photosensitive conductive paste method and sputtering.

• Journal of Power Electronics
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• v.9 no.2
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• pp.215-223
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• 2009

A design methodology for transformers including integrated and center-tapped structures for LLC resonant converters is proposed. In the LLC resonant converter, the resonant inductor in the primary side can be merged in the transformer as a leakage inductance. And, the absence of the secondary filter inductor creates low voltage stress on the secondary rectifiers and is cost-effective. A center-tapped structure of the transformer secondary side is widely used in commercial applications because of its higher efficiency and lower cost than full-bridge structures in the rectifying stages. However, this transformer structure has problems of resonance imbalance and transformer inefficiency caused by leakage inductance imbalance in the secondary side and the position of the air-gap in the transformer, respectively. In this paper, gain curves and soft-switching conditions are derived by first harmonic approximation (FHA) and operating circuit simulation. In addition, the effects of the transformer including integrated and center-tapped structures are analyzed by new FHA models and simulations to obtain an optimal design. Finally, the effects of the air-gap position are analyzed by an electromagnetic field simulator. The proposed analysis and design are verified by experimental results with a 385W LLC resonant converter.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1865-1872
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• 2011

This study investigates the sensitivity of a gas sensor to volatile organic compounds (VOCs) at various operating temperatures and catalysts. Nano-sized powdered $WO_3$ prepared by sol-gel and chemical precipitation methods was mixed with various metal oxides. Next, transition metals (Pt, Ru, Pd, and In) were doped on the surface of the mixture. Metal-$WO_3$ thick films were prepared using the screen-printing method. The physical and chemical properties of the films were studied by SEM/EDS, XRD, and BET techniques. The measured sensitivity to VOCs is defined as the ratio ($R_a/R_g$) of resistance ($R_{air}$) of $WO_3$ film in the air to resistance ($R_{gas}$) of $WO_3$ film in a VOCs test gas. The sensitivity and selectivity of the films were tested with various VOCs such as acetaldehyde, formaldehyde, methyl alcohol, and BTEX. The thick $WO_3$ film containing 1 wt % of Ru and 5 wt % of $SnO_2$ showed the best sensitivity and selectivity to acetaldehyde gas at an operating temperature of 300 $^{\circ}C$.

• Journal of Drive and Control
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• v.21 no.2
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• pp.8-14
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• 2024

This paper investigates the jetting characteristics of an aerosol jet printing (AJP) process as a function of design and operating conditions. The governing equations of the AJP system are derived for experimentation and analysis. To understand the characteristics of the AJP system, this thesis analyzes the jetting characteristics as a function of the flow rate of the carrier gas and the sheath gas, and the variation of the linewidth with the nozzle exit size based on particle tracking. This thesis focuses on computational fluid dynamics (CFD), which is a computer simulation. The particle tracking results obtained by CFD were analyzed using MATLAB. CFD analytical models can be analyzed in environments with different conditions and consider more specific situations than mathematical computational models. The validity of the CFD analysis is shown by comparing the experimental results with the CFD analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.849-856
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• 2012

Chip on board type white light emitting diode on metal core printed circuit board with high thixotropy silicone is fabricated by vacuum printing encapsulation system. Encapsulant is chosen by taking into account experimental results from differential scanning calorimeter, shearing strength, and optical transmittance. We have observed that radiant flux and package efficacy are increased from 336 mW to 450 mW and from 11.9 lm/W to 36.2 lm/W as single dome diameter is varied from 2.2 mm to 2.8 mm, respectively. Double encapsulation structure with 2.8 mm of dome diameter shows further significant enhancement of radiant flux and package efficacy to 667 mW and 52.4 lm/W, which are 417 mW and 34.8 lm/W at single encapsulation structure, respectively.