• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.05a
• /
• pp.59.1-59.1
• /
• 2009

레독스 흐름 배터리 (Redox Flow Battery)는 외부의 탱크 등에 저장해 둔 활성물질(이온 가수가 변화는 금속) 의 용액을 펌프로 전해셀에 공급하여 충전 방전하는 배터리로 신재생 에너지인 풍력과 태양광 발전, 야간의 잉여 전력 저장 등 대용량 전력 저장 장치로 관심이 높아지고 있다. 대표적인 레독스 흐름 배터리로 알려진 바나듐 레독스 흐름 배터리는 이온 교환막 사용으로 인하여 전기전도도, 기계적 강도, 투과도 및 전해질 내의 화학적 안정성 등 여러 가지 문제점과 함께 비용 문제점을 야기한다. 하지만 새로운 용해 납 레독스 흐름 배터리는 이온 교환막을 사용하지 않아 바나듐 레독스 흐름 배터리의 문제점 및 시설비가 절약되는 장점이 있어 새로이 연구되지고 있다. 본 연구는 레독스 흐름 배터리에 주로 이용되는 카본 전극재료의 따라 형성되는 Pb, $PbO_2$ 박막의 미세 구조를 및 에너지 효율 특성을 분석하였다. 실험은 half-cell로 이루어졌으며 작업전극은 Carbon felt, Ordered Graphite, Disordered Graphite, Glassy Carbon 등을 여러 카본 재료를 사용하였고, 상대전극은 Pt, 기준전극으로 Ag/AgCl를 사용하여 Cyclic Voltammetry특성과 충방전 특성을 연구하였다. 전해질은 Lead Carbonate ($PbCO_3$)+Methanesulfonic acid ($CH_3SO_3H$) 들어간 수용성 전해질을 교반을 통해 이용하였다. 여러 carbon 전극재료와 생성된 Pb, $PbO_2$ 막의 표면구조, 미세구조, 상들의 변화는 XRD, SEM, EDX, Raman등을 통하여 분석하였으며, 전기화학 공정의 변수와 전극에 따른 에너지 효율특성에 대하여 고찰해 보았다.

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.10
• /
• pp.1041-1049
• /
• 2013

One of the causes of malfunction of commercial vehicle is corrosion or wear. In order to prevent corrosion and wear, lubricants have to be supplied periodically. However, the period of lubrication usually depends on operator's judgment. If the period is too short, excess lubricant will cause pollution and unnecessary expenses, where as long periodic supply of lubricant might cause wear, damage and eventual breakdown. Therefore, an automatic lubrication system with predetermined interval will reduce the excessive supply of lubricating oil and prevent wear and damage. This thesis presents an automatic lubrication system which consists of a lubricant pump and an embedded controller. An automatic lubrication operating algorithm is used to operate the lubricant pump and feedback the pressure status of the system using pressure sensors. The developed system shows an efficient periodic supply of lubricant.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.16 no.6
• /
• pp.677-682
• /
• 2006

Multi-domain design is difficult because such systems tend to be complex and include a mixtures of electrical, mechanical, hydraulic, and thermal components. To design an optimal system, unified and automated procedure with efficient search technique is required. This paper introduces design method for multi-domain system to obtain design solutions automatically, combining bond graph which is domain independent modeling tool and genetic programming which is well recognized as a powerful tool for open-ended search. The suggested design methodology has been applied for design of electric fitter, electric printer drive, and and pump system as a proof of concept for this approach.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2022.10a
• /
• pp.43-46
• /
• 2022

The optimal operation of the water purification plant can be carried out only when the required flow rate is supplied in a timely manner using the minimum electrical energy by accurately predicting the pattern and amount of tap water used in the consumer. In order to ensure the stability of tap water production and supply, a system that can be pre-verified before applying AI-based composite sensors to the water purification plant was established to derive complementary matters through the pre-verification model for each composite sensor and improve the quality and operation stability of the composite sensor data.

• Journal of Sensor Science and Technology
• /
• v.33 no.3
• /
• pp.158-164
• /
• 2024

We developed a self-operated paper pump that can maintain a nearly constant flow rate of an aqueous solution along a paper strip channel in paper-based analytical devices (PADs). The quasi-stationary flow rate was controlled by increasing the crosssectional channel area (capillary force) using a fan-shaped absorption pad coupled with a paper strip channel. The flow rate is regulated by varying the fan angle of the circular absorbing pad. Furthermore, the flow rate can be increased by furnishing a hollow cavity at the center of a conventional paper strip channel. The rate was regulated by varying the length of the hollow paper channel in the flow rate range of 5.1-26.4 mm/min. As a preliminary work, a paper-pump-coupled PAD was fabricated, and its CV detection capability was evaluated for the redox reaction of Fe(CN)₆^+4/+3. The combination of a paper pump with a PAD resulted in an ideal CV curve with a higher limiting current and faster response time. These results are interpreted well by the Levich equation, which suggests that the paper pump is a very useful component in paper-based sensors.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.51 no.9
• /
• pp.431-437
• /
• 2002

Low hemolysis is one of the key factors in the production of successful rotary blood pumps. It is, however, difficult to identify the areas where hemolysis occurs. Computational fluid dynamics(CFD) analysis enables the engineer to predict hemolysis on a computer Fluid dynamics in five different axial flow pumps was analyzed 3-dimensionally using CFD software. The impeller was rotated at a speed which supplied a flow of 5L/min at a pressure difference of 100mmHg. Changes in the turbulent kinetic energy along streamlines through the pumps were computed. Reynolds' shear stress( (equation omitted) ) was calculated using the turbulent kinetic energy. Hemolysis was evaluated based on Reynolds'shear stress and its exposure time(t) : dHb/Hb=3.62$\times$10$^{-5}$ $t^{0.785}$$\tau$$^{2.416}$ . Hemolysis of the pumps was measured in vitro using fresh bovine blood to which citrate phosphate dextrose was added to prevent clotting. A pump flow of 5L/min was maintained at a pressure difference of 100mmHg for 3h. The normalized index of hemolysis(NIH) as measured. Reynolds' shear stress was high behind the impellers. The measured NIH and the calculated hemolysis(dHb/Hb) shoed a good correlation; NIH=0.0003(dHb/Hb) (r=0.90, n=6) in the range of NIH between 0.003 and 1.1. CFD analysis can predict the in vitro results of hemolysis as well as the areas where hemolysis occurs.ysis occurs.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.8
• /
• pp.1083-1090
• /
• 2012

Copper alloys are widely used for casting materials including ship's propellers and pump impellers as they provide high corrosion resistance. In addition, the demand for these alloys is increasing with rapid growth of offshore structures and exploitation of various substitute energy sources. However, they require regular maintenance because of erosion and cavitation damages induced by exposure to marine environment at high speed flows for a long period of time. Water cavitation peening have received attention as one of surface modifications for durability improvement of the copper alloys. This is a environment friendly technology without influence of heat and easily applicable to casting materials. In this research, water cavitation peening was employed in distilled water for copper alloy castings as a function of time and evaluation of corrosion resistance was followed in seawater for the modified surface by using electrochemical methods. The result suggests that the water cavitation peening for 2 minutes was found to be the optimal peening parameter in terms of durability and corrosion resistance.

• Journal of IKEEE
• /
• v.22 no.2
• /
• pp.302-308
• /
• 2018

Multi-Layer Sputtering is aim to develop desired thickness thin film multi-layer with different materials. The multi-layer thin film deposition process occupies a relatively large portion in the process time, because the main reason is that it takes much time to move the substrate to be deposited and to make the chamber into a high vacuum state compared to the process time. Most of semiconductor and display industries sputter a single substance in one chamber and move boards through multi-continuous robots to another chamber to sputter other materials. This will inevitably require multiple chambers, vacuum pumps, and multi-contamination robots within the process facility. To solve these problems, this paper proposes a control system for multi-layer thin film sputtering devices that deposit different materials within a single vacuum chamber and is applied in TFT process. The manufacture and experiment of the control system proved its validity.

• Journal of IKEEE
• /
• v.10 no.1 s.18
• /
• pp.10-15
• /
• 2006

In this paper, a clock and data recovery (CDR) circuit for a serial link with a half rate 4x oversampling phase and frequency detector structure without a reference clock is described. The phase detector (PD) and frequency detector (FD)are designed by 4X oversampling method. The PD, which uses bang-bang method, finds the phase error by generating four up/down signal and the FD, which uses the rotational method, finds the frequency error by generating up/down signal made by the PD output. And the six signals of the PD and the FD control an amount of current that flows through the charge pump. The VCO composed of four differential buffer stages generates eight differential clocks. Proposed circuit is designed using the 0.18um CMOS technology and operating voltage is 1.8V. With a 4X oversampling PD and FD technique, tracking range of 24% at 3.125Gbps is achieved.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.3
• /
• pp.85-92
• /
• 2005

Due to the friction characteristic of pump, cylinder, and between passenger car and the rail, there exist dead zone in the hydraulic system actuated with inverter, which can not be controlled by a PID controller. In this paper, the friction characteristic of a cylinder is considered first, which may cause the uncontrolled speed in the zero-crossing speed region. And then, the zooming fuzzy logic controller is designed to overcome the drawback by the existing PID speed controller. Finally, The proposed hybrid fuzzy controller is applied to the PID controller in the normal speed region and to the fuzzy controller in the zero-crossing speed region. The reason is that the problem of the uncontrolled speed in the zero-crossing speed region caused by the friction characteristic of the cylinder in hydraulic elevator can be solved, and the effectiveness of the controlling system not only in the zero-crossing speed region but also the overall controlling region including steady-state can be simulated and performed.