• Applied Chemistry for Engineering
• /
• v.9 no.4
• /
• pp.463-468
• /
• 1998

When sulfuric acid was added in HCl etching solution, corrosion of aluminum metal was inhibited by the chemical adsorption of sulfate ions. In the presence of $SO_4^{-2}$, cyclic voltammetry showed that the protective oxide film was formed on the inner surfaces of etch pits and, pit density was increased by nucleation on both the aluminum surface and the pits inside. Structure and distribution of etch pits found in AC etching of aluminum were strongly influenced by the concentration of $SO_4^{-2}$ and the amount of cathodic pulse charging. Below $0.8mC/cm^2$ of cathodic pulse charging, oxide films formed inside actively dissolving pits indicated the higher resistance to pit nucleation as the concentration of $SO_4^{-2}$ increases. However, the structural change of oxide films occurred above the $0.8mC/cm^2$ charging and the effect of $SO_4^{-2}$ was minimized, and it resulted in the rapid formation of etch pits.

• Progress in Superconductivity and Cryogenics
• /
• v.16 no.3
• /
• pp.21-25
• /
• 2014

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.303-310
• /
• 2002

Overbreak occurred inevitably in a tunnel excavation, Is the main factor for increasing cost and time in tunnel projects. Furthermore the damage to the remained rock mass related to the overbreak can give rise to a serious safety problem in tunnels. As a rule of thumb, causes for the overbreak are inaccuracy in drilling, the wrong design of blasting and selection of explosives, and heterogeneity in rock mass. Specially, the geological features of the rock mass around periphery of an excavation are very important factors, so a lot of researches have been conducted to describe these phenomena. But the quantitative geological classification of the rock mass for the overbreak and the method for decreasing the amount of the overbreak have not been established. Besides, the technical improvement of the charge method is requested as explosives for the smooth blasting have not functioned efficiently. In this study, the working face around periphery of an excavation has been continuously sectionalized to 5∼6 parts, and the new Blastability Index for the overbreak based on 6 factors of RMD(Rock Mass Description), UCS(Uniaxial Compressive Strength) JPS(Joint Plane Spacing), JPO(Joint Plane Orientation), JPA(Joint Plane Aperture) and FM(Filling Material) is proposed to classify sections of the working face. On the basis of this classification, the distance between contour holes and the charging density are determined to minimize the overbreak. For controlling the charging density and improving the function of explosives, the New Deck Charge(N.D.C) method utilizing the deck charge method and detonation transmission in hole has been developed.

• Plant Journal
• /
• v.16 no.4
• /
• pp.40-44
• /
• 2020

In this study, after supplying a pulse wave to the 2 V Industrial Lead-Acid Battery electrode plate and repeating the charging and discharging, the discharging time per voltage was analyzed. According to the result of experiment, while the lead-acid Battery that a pulse wave is not supplied decreased about 18 % of discharging capacity than the beginning, the lead-acid Battery that a pulse wave is supplied decreased a little amount much lower than 18 %, of discharging capacity and recorded the 0.56 % decrease, at a minimum, from discharging capacity at the 20 kHz frequency. This means that the sulfate on electrode plate is detached and the positive and negative charge transfer is highly activated at the 20 kHz frequency

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.5
• /
• pp.405-410
• /
• 2020

In this literature, we are introduce a basic design of multi energy hub based on natural gas governor station. Multi energy hub consists of turbo expender generator, phosphoric acid fuel cell, pressure swing adsorption, H₂ charging station, utilities and etc. We design a hybrid energy hub system that provides energy using these complex energies, and calculates the amount of electricity that can be produced and the amount of hydrogen charged through the process analysis. TEG and phosphoric acid fuel cell produce 2,290 to 2,380 kW and can supply electricity to 500 houses. In addition, By-product H₂ gas is refined to H₂ vehicle fuel. This will help maximize the balance of energy demand and supply and improve national energy efficiency by integrating unused decompression energy power generation technology and various power generation/heat source technologies.

• Journal of the Korean Institute of Gas
• /
• v.23 no.6
• /
• pp.67-73
• /
• 2019

Hydrogen is difficult to accurately measure the amount of charge due to sudden temperature changes and pressure rise when charging the vehicle. In order to construct a hydrogen infrastructure, it is important to precisely measure the amount of charge that can be a sensitive issue in commercial transactions. In this study, the accuracy of metering of domestic hydrogen stations was evaluated as a study for metering management of hydrogen dispenser. For the experiment, we constructed metering system using master meter method and measured the flow rate in the actual hydrogen vehicle charging environment. As a result of error occurred about 10% on average, and the hydrogen loss per one charge was found to be up to 60g.

• Smart Structures and Systems
• /
• v.15 no.6
• /
• pp.1625-1642
• /
• 2015

We propose an electrically self-reliant structural health monitoring (SHM) system that is able to wirelessly transmit sensing data using electrical power generated by vibration without the need for additional external power sources. The provision of reliable electricity to wireless SHM systems is a highly important issue that has often been ignored, and to expand the applicability of various wireless SHM innovations, it will be necessary to develop comprehensive wireless SHM devices including stable electricity sources. In light of this need, we propose a new, highly efficient vibration-powered generator based on a tuned-mass-damper (TMD) mechanism that is quite suitable for vibration-based SHM. The charging time of the TMD generator is shorter than that of conventional generators based on the impedance matching method, and the proposed TMD generator can harvest 16 times the amount of energy that a conventional generator can. The charging time of an SHM wireless transmitter is quantitatively formulated. We conduct wireless monitoring experiments to validate a wireless SHM system composed of a self-reliant SHM and a vibration-powered TMD generator.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.2
• /
• pp.153-160
• /
• 2013

This research paper describes the development of battery charger with a variable output voltage capacity for charging the batteries used in electrical vehicles. The voltage and current accordingly is control via the buck converter that receives three phase current at primary side and fed to bridge rectifier which is comprised of full bridge converter and HFTR(High Frequency Transformer) for isolation and a square wave AC output. The transformer primary side is in series to divide certain charging current and the secondary side is comprised of six fix transformers so that they can generate certain amount of power and various output voltage through relay connection using 6 DC outputs. Moreover, all parallel connected full bridge serial resonant converter communicate together with upper(main) controller. The constructed structure is verified by conducting the test on PSIM as well as experimentally.

• Transactions of the Korean hydrogen and new energy society
• /
• v.30 no.6
• /
• pp.479-484
• /
• 2019

Environmental problems were related to human life from second industrial revolution. Recently, peoples are interested in solving global warming problem and improving air quality. Therefore, we request for eco-friendly vehicles such as fuel cell electric vehicles using eco-friendly hydrogen energy. In order to reduce particulate matter in Korea, we have established a plan to promote the deployment of eco-friendly vehicles. In this paper, we analyzed the average monthly charging status and hydrogen consumption by introducing fuel cell bus.

• Journal of Biosystems Engineering
• /
• v.29 no.1
• /
• pp.21-28
• /
• 2004

Spraying is one of the most efficient methods for pesticide and insecticide control. Generally, orchard sprayers(aircarrier sprayer) are used for such applications. However, when an orchard sprayer is used, only 20% of total amount of spray deposits on the target. The rest of spray are not only wasted but are also potential sources of environmental pollution. The research far the development of electrostatic spraying system for orchard sprayer was conducted to develop the new pesticide application technology for the reduction of environmental pollution and f3r the production of safe agricultural products. The spray characteristics for nozzles with the different charging methods were tested and the effect of electrostatic charge was analyzed, in the laboratory experiments. The results of this study indicate that the capacitive type of electrostatic spraying nozzle exhibits a large current deposition of water sprays on the sample target. The covering area ratio by conventional spraying system was 10.2%, while that of electrostatic sprays with pulse induction charging method gave the increased covering area ratio by 4.3 times.