• Laser Solutions
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• v.13 no.1
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• pp.11-15
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• 2010

Indium tin oxide (ITO) provides high electrical conductivity and transparency in the visible and near IR (infrared) wavelengths. Thus, it is widely used as a transparent electrode for the fabrication of liquid crystal displays (LCDs) and organic light emitting diode displays (OLRDs), photovoltaic devices, and other optical applications. Lasers have been used for removing coating on polymer substrate for flexible display and electronic industry. In selective removal of ITO layer, laser wavelength, pulse energy, scan speed, and the repetition rate of pulses determine conditions, which are efficient for removal of ITO coating without affecting properties of the polymer substrate. ITO coating removal with a laser is more environmentally friendly than other conventional etching methods. In this paper, pattering of ITO film from polymer substrates is described. The Yb:KGW femtosecond laser processing system with a pulse duration of 250fs, a wavelength of 1030nm and a repetition rate of 100kHz was used for removing ITO coating in air. We can remove the ITO coating using a scanner system with various pulse energies and scan speeds. We observed that the amount of debris is minimal through an optical and a confocal microscope, and femtosecond laser pulses with 1030nm wavelength are effective to remove ITO coating without the polymer substrate ablation.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.1-7
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• 2014

A numerical study of transient conjugate heat transfer on micro heater in a micro-channel substrate under a sinusoidal heat load was conducted. It was found that the time constant is not affected by the maximum heating magnitude of the sinusoidal heat load. However, the time constant increases with low duration of the sinusoidal heating period and low Reynolds number. Moreover, there is a threshold where a heater temperature do not reach to time constant at low thermal diffusivity, low flow rate, and low pulse duration of the sinusoidal heating. The time constant should be considered for transient convective heat transfer under transient sinusoidal heat load in a micro heat sink.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.27-34
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• 2005

We analyze in detail axially symmetric theoretical study for the photothermal pulsed radiometry of a cylindrical model. The theoretical solutions describe the transient infrared radiation from the sample heated by short-duration pulsed heating. In the conventional transmission radiometry technique, the excitation source and the detector are on opposite sides of the sample, otherwise in the new single ended radiometry technique, the excitation source and the detector are on same sides of the sample. The analytical solution described for photothermal radiometry in this study would not need to cut or polish samples to measure the thermal diffusivity. Therefore the radial area and axial thickness of samples are not limited. The effects of excitation pulse duration and the area of heat source are discussed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1012-1013
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• 2006

A technology of hardening porous materials of titan powders has been elaborated. The technology is based on passing alternating current with duration of ${\sim}10^{-1}{\ldots}10^1$ s through porous ($35{\ldots}40%$) blanks made by method of Sintering by Electric Discharge (SED) by passing a pulse of current with duration of ${\sim}10^{-5}{\ldots}10^{-3}$ s. The influence of technological regimes of porous blanks treatment on their structure and properties is investigated. Geometry and dimension of contact necks between powder particles of obtained samples are evaluated. Variations of porosity and strengths as well as microstructure of porous samples materials before and after treatment are investigated. Optimum range of treatment technological regimes is determined within which porosity of $30{\ldots}35%$ with maximum strength values.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.4
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• pp.49-54
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• 2005

In this paper, micro structuring technique using localized electrochemical deposition (LECD) with ultra short pulses was investigated. Electric field in electrochemical cell was localized near the tool tip end region by applying pulses of a few hundreds of nano second duration, Pt-Ir tip was used as a counter electrode and copper was deposited on the copper substrate in mixed electrolyte of 0.5 M $CuSO_4$ and 0.5 M $H_2SO_4$, The effectiveness of this technique was verified by comparison with ECD using DC voltage. The deposition characteristics such as size, shape, surface, and structural density according to applied voltage and pulse duration were investigated. The proper condition was selected based on the results of the various experiments. Micro columns less than $10{\mu}m$ in diameter were fabricated using this technique. The real 3D micro structures such as micro spring and micro pattern were made by the presented method.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.683-692
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• 2023

This research assesses the mechanical properties of concrete, utilizing both normal and lightweight aggregates, through measurements of compressive strength and ultrasonic pulse velocity. The study observed that concrete with normal aggregates exhibited higher compressive strength in its initial stages, whereas concrete with lightweight aggregates showed increased strength over time, likely attributed to the higher water absorption rate of lightweight aggregates. Ultrasonic pulse velocity generally registered higher in normal aggregate concrete, barring a specific duration, presumably due to variations in the internal pore structure of the aggregates. The correlation coefficient(R²) for the strength prediction equation, derived from the relationship between compressive strength and ultrasonic pulse velocity, exceeds 0.95. This high correlation suggests that the predictive equation based on these experimental findings is a reliable method for estimating concrete strength.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.6
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• pp.626-629
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• 1991

The negative wire of an electrolytic ozone generator, proposed by authors, has been contaminated by attaching the impurity particulate in tap water, which is called BUILD-UP phenomenon. The higher applied voltage and the larger wire diameter have shown the higher build-up rate, which makes the current reducing largely and concurrently the ozone production smaller. It is found that the positive electrode of the ozone generator has a strong SELF-CLEANING effect by detaching the impurity particulate from its surface, which, however, is used us a novel means of solving the build-up problem. As a result, the build-up problem can be solved effectively by applying an alternate square wave pulse voltage to the electrodes so as to get the self-cleaning ability on the both electrodes during each of the half pulse duration time.

• Progress in Superconductivity and Cryogenics
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• v.6 no.3
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• pp.1-5
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• 2004

This paper presents a study on the stability of bare and cu-laminated YBCO-coated conductor. we investigate the characteristics of quench/recovery behavior of YBCO test samples. bare and copper-laminated, by subjecting each test sample. immersed in a bath of liquid nitrogen boiling at 77.3 K. to a transport current pulse superimposed to a baseline DC current of 90-95% the critical current. The current pulse has an amplitude up to ∼4.5 times the critical current and a duration of 300 ms. This paper presents both experimental and simulation results.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1314-1321
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• 2014

A new simplified topology for a dynamic voltage restorer (DVR) based on direct converter with a reduced number of switches is presented. The direct converter is fabricated using only three bi-directional controlled switches. The direct converter is connected between the grid and center-tapped series transformer. The center-tapped series transformer is used to inject the compensating voltage synthesized by the direct converter. The DVR can properly compensate for long-duration, balanced, and unbalanced voltage sag and swell by taking power from the grid. The switches are driven by ordinary pulse width modulation signals. Simulation and hardware results validate the idea that the proposed topology can mitigate sag of 50% and swell of unlimited quantity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1199-1202
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• 2003

In this research, microfabrication technique using localized electrochemical deposition is presented. Electric field is localized near the tip end region by applying ultra short pulses. Platinum tip is used as the counter electrode and copper is deposited on the copper substrate in 0.5 M CuSO$_4$ and 0.5 M H$_2$SO$_4$ electrolyte. The deposition characteristics such as size, shape, and structural density according to pulse duration and applied voltage are investigated. Micro-columns less than 10 $\mu\textrm{m}$ in diameter are fabricated using the presented technique. The process can be potentially used for three dimensional metal structure fabrications with micrometer feature size.