• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.30 no.3
• /
• pp.451-458
• /
• 1997

The oxygen transfer coefficient was not significantly affected by either flow pattern, initial bubble size or the wastes present in the water studied. Surface active substances in the water did however influence the transition from bubble to slug flow. Airlift with length to diameter ratios less than 50 suffered from considerable losses in efficiency. When properly designed, airlift pumping efficiencies were comparable to those of conventional centrifugal pumps and the oxygen transfer efficiency were as high as or higher than those of diffused aeration systems.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.2110-2112
• /
• 2000

This paper describes the self healing characteristics of a metalized polypropylene film(MPPF) used for energy storage capacitors. In the experiment, a d.c. voltage was applied to the MPPF, and the partial discharge inception voltages(PDIVs), the applied voltages at self healing, the burn out area and the current in the grounding conductor were measured and recorded. As a result, it was found that no PDs were found till the first pre-self healing occurred, and the applied voltage at self healing was increased with PPF thickness. Self healing was much more dependant on the shape of the air void than its diameter and the burn out area and the current in the grounding conductor at self healing was also increased with the applied voltage at self healing.

• Journal of the Korean Society of Safety
• /
• v.17 no.4
• /
• pp.153-159
• /
• 2002

This experimental study is aimed to increasing the velocity in the sewerage and also development of easy removal method for a corrosion and sand in the flow pipe. And the result by the increasing the out flow per unit time, diameter of sewerage pipe is becoming small size, cut down the construction fee and the same time reducing the tubulent flow pattern in the flow pipe. As a result of detected experimental velocity signal from the probe in the test wall surface, reducing the pump power and increasing the out flow unit time. Apparent water velocity decreases as the value of void ratio increases depends on the varies center of pipe.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.9-12
• /
• 2000

Insulators for high-voltage and large-power should be endured mechanically the weight of mold bushing itself and the force of pushed from contact with circuit breaker and conductor. But dielectric breakdown could be occurred result from the external circumstances and internal factors such as chemical reaction, partial discharge, change of temperature and the relation of temperature-time in process of casting. Therefore, to get rid of external and internal factors of dielectric breakdown. Furthermore, to prevent the internal cracks, void, cavity which resulted from the contraction originated on the interface between copper and epoxy resin, formed semi-conductive layer with partially carbon painted on copper bar. The PD properties and the insulation qualities of epoxy molded insulators were improved by roles of cushions for the direction of diameter and natural sliding effects as like separated from conductor for the direction of length.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.6
• /
• pp.23-36
• /
• 2007

To overcome the limits of the static pile load test for large diameter drilled shafts, bi-directional low pressure pile load test (BDL PLT) has been used but this test method containes some problems that has not been solved basically. That is, BDL PLT has some problems: difficulty in jack (or cell) arrangement for large test capacity, void remain inside jack (or cell) due to the unrecovery of piston after test etc. In this study, bi-directional double-acting high pressure pile load test (BDH PLT W/DOJ) was developed and confirmed for a in-situ large diameter drilled shaft. At present, test specification of bi-directional pile load test (BDPLT) is being made, and severed main issues (such as, test kinds, test capacity, necessity of use of double-acting and attention of application to service pile) will be contained at the specification.

• Journal of Korea Water Resources Association
• /
• v.48 no.7
• /
• pp.535-543
• /
• 2015

Measurements of multiphase flows containing bubbles have been limited because most existing methods target one phase flows. Especially, multiphase flows with a high void ratio have been rarely successful in measurements due to the sudden change of density and thick interfaces between air and water. This study introduces two methods that are capable of measuring flow fields regardless of bubble void ratio, named bubble image velocimetry and bundle fiber optic flow meter. The calculation of the depth of field is suggested to reduce and estimate errors by perspective image velocimetry. The bundle fiber optic flow meter is designed to increase a measurement rate using many optical fibers with a thin diameter. The two methods measured bubble plumes to test reliability and the velocity measurements show good agreement. In addition a hydraulic jump, one of the multiple flows in rivers was measured to test applicability of the methods.

• Journal of the Korean institute of surface engineering
• /
• v.47 no.2
• /
• pp.68-74
• /
• 2014

The seed step-coverage enhancement process (SSEP) using Pd/Cu/PVP colloids was investigated for the filling of through silicon via (TSV) without void. TEM analysis showed that the Pd/Cu nano-particles were well dispersed in aqueous solution with the average diameter of 6.18 nm. This Pd/Cu nano-particles were uniformly deposited on the substrate of Si/$SiO_2$/Ti wafer using electrophoresis with the high frequency Alternating Current (AC). After electroless Cu deposition on the substrate treated with Pd/Cu/PVP colloids, the adhesive property between deposited Cu layer and substrate was evaluated. The Cu deposit obtained by SSEP with Pd/Cu/PVP colloids showed superior adhesion property to that on Pd ion catalyst-treated substrate. Finally, by implementing the SSEP using Pd/Cu/PVP colloids, we achieved 700% improvement of step coverage of Cu seed layer compared to PVD process, resulting in void-free filling in high aspect ratio TSV.

• Journal of the Korean Ceramic Society
• /
• v.44 no.7
• /
• pp.362-367
• /
• 2007

Stent is a tiny structure made with either ceramic coating and/or bare metal. Being approximately $1{\sim}2 mm$ in diameter, it consists of holes, slots, or void space and is designed to cover entire medical lesions. Stent implantation into patients' arteries has been practiced for a little more than a decade in order to widen the blocked artery. The adoption of the stent has significantly improved the efficacy when compared with the previous medical practice by balloon angioplasty alone. Yet better biomedical performance of the stent is being demanded in order to eliminate the still existing problem of artery restenosis, which means the artery becomes narrowed again. Recent literature survey shows researches on ceramic coatings onto the stent surface, or material design to improve the mechanical response of the stent. This study focuses more on the material design and mechanical analysis. The results showed that the void configuration within the stent affects the mechanical response significantly. The rectangular shape was found to yield expansion at a relatively lower pressure than the elliptical slot for a slotted tube stent. The present results, when combined with research on coating at the stent surface, may provide stents with improved bio-medical performance.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.12
• /
• pp.37-46
• /
• 2011

An application frequency of vertical drainage method is increasing as an effective consolidation acceleration method. PBD method is most frequently used as a consolidation acceleration method in vertical drainage methods. PBD is economical and easy to operate but has some problems those are an environmental pollution and a decrease of a discharge capacity caused by bending of drainage materials when it is used in great depth. SCP method was frequently used because it's discharge capacity was good but now it is rarely used because of an increase of the material price because of an order imbalance. As the way to solve these problems, GCP method has been to the fore. For analyzing the effect of GCP method on the discharge capacity, three types of composite discharge capacity tests are done by using GCP, SCP and PBD respectively with the circle case, ${\phi}38{\times}h70cm$. On the contrary to this, GCP shows the worst discharge capacity for a decrease of the void ratio and the clogging phenomenon caused by increasing load. Also to figure out the clogging range of GCP, the clogging of GCP is checked in each load stage with a large case($1.0m{\times}0.5m{\times}1.1m$) which has clear acrylic front face. The diameter of GCP was 35cm and a clogging phenomenon occurred in 10% approximately. The result shows that the discharge capacity of GCP was given the lowest value for a decrease of the void ratio and the clogging phenomenon causing by increasing load. And the clogging phenomenon mostly occurred within 10% of GCP's diameter range.

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.4
• /
• pp.99-104
• /
• 2015

The requirement for success of via filling is its ability to fill via holes completely without producing voids or seams. Defect free via filling was obtained by optimizing plating conditions such as current mode, current density and additives. However, byproducts stemming from the breakdown of these organic additives reduce the lifetime of the devices and plating solutions. In this study, the relationship between JGB and current density on the copper via filling was investigated without the addition of other additives to minimize the contamination of copper via. AR 4 with $15{\mu}m$ diameter via were used for this study. The pulse current was used for the electroplating of copper and the current densities were varied from 10 to $20mA/cm^2$ and the concentrations of JGB were varied from 0 to 25 ppm. The map for the JGB concentration and current density was developed. And the optimum conditions for the AR 4 via filling with $15{\mu}m$ diameter were obtained.