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Effect of Mixing Ratio of Biodiesel on Breakup Characteristics of a Single Droplet
( Yop Kim Sa ),( Sung Wook Park ),( Kian Sung ),( Haeng Mook Cho ),( Chang Sik Lee ) 한국액체미립화학회 2005 한국액체미립화학회 학술강연회 논문집 Vol.2005 No.-
In this paper, the breakup characteristics of a single droplet were analyzed as a function of mixing ratio of bioidesel. In order to investigate the effects of high surface tension and viscosity of biodiesel on the breakup mechanism of single droplet, the experiments were performed at various mixing ratios of biodiesels. In addition, the physical properties such as density, kinematic viscosity and surface tension of the biodiesel blended fuels were measured to study the relations between the non-dimensional numbers such as Weber number and Reynolds number, and the breakup mechanism. The experimental apparatus consisted of a droplet generation system, an air flow nozzle, a light source, a long distance microscope and a CCD camera. In the first stage breakup region, the droplet deformation rate was measured in order to reveal out the effect of high surface tension and kinematic viscosity on the deformation of a single droplet. The results of this experiment showed that the higher surface tension and viscosity of biodiesel prevent the disintegration of liquid droplet. Also the breakup mechanism is transited at higher relative velocity as the mixing ratio is increased.
Control Methods of Inverter-Interfaced Distributed Generators in a Microgrid System
Il-Yop Chung,Wenxin Liu,Cartes, David A,Collins, Emmanuel G,Seung-Il Moon IEEE 2010 IEEE transactions on industry applications Vol.46 No.3
<P>Microgrids are a new concept for future energy distribution systems that enable renewable energy integration and improved energy management capability. Microgrids consist of multiple distributed generators (DGs) that are usually integrated via power electronic inverters. In order to enhance power quality and power distribution reliability, microgrids need to operate in both grid-connected and island modes. Consequently, microgrids can suffer performance degradation as the operating conditions vary due to abrupt mode changes and variations in bus voltages and system frequency. This paper presents controller design and optimization methods to stably coordinate multiple inverter-interfaced DGs and to robustly control individual interface inverters against voltage and frequency disturbances. Droop-control concepts are used as system-level multiple DG coordination controllers, and control theory is applied to device-level inverter controllers. Optimal control parameters are obtained by particle-swarm-optimization algorithms, and the control performance is verified via simulation studies.</P>
Fluorescence and Pattern Scanner for Biochips using a DVD Optical Pick-Up
Seung-Yop Lee(이승엽),Yit Yim(임빛),Sookyung Kim(김수경) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
A low-cost highly sensitive DNA microarray scanner for fluorescent detection is developed based on the pick-up head of a commercially available optical storage device, DVD. A laser beam of 650 ㎚, generated by a DVD laser diode, is used for dynamic auto-focusing as well as the excitation of Cy5 fluorescent dye. The fluorescence intensity emitted from Cy5 dye is measured by a photomultiplier tube (PMT). In contrast to other microarray scanners, the DVD-based scanner offers the auto-focusing function using the focus error signal (FES) and a voice coil motor (VCM), and this enables fast response, high accuracy and compact size. The fluorescence-detecting performance of the scanner is inspected by using a commercial BAC (Bacterial Artificial Chromosome) oligonucleotide chip and a scanner evaluation microarray (DS01). Experiments have shown that the DVD-based scanner meets the limit of detection, ensuring the feasibility of a low-cost, highly sensitive DNA microarray scanner. The scanner is also used to measure the surface profile of the microarray pattern having sub-micron resolution.
Il-Yop Chung,Seung-Il Moon 대한전기학회 2007 Journal of Electrical Engineering & Technology Vol.2 No.2
This paper proposes a new islanding detection method for inverter-interfaced distributed generators (DG). To detect islanding conditions, this paper calculates the phase angle variation of the system voltage by using the phase-locked loop (PLL) in the inverter controllers. Because almost all inverter systems are equipped with the PLL, the implementation of this method is fairly simple and economical for inverter-interfaced DGs. The detection time can also be shortened by reducing communication delay between the relays and the DGs. The proposed method is based on the fact that islanding conditions result in the frequency and voltage variation of the islanded area. The variation depends on the amount of power mismatch. To improve the accuracy of the detection algorithm, this paper injects small low-frequency reactive power mismatch to the output power of DG.
Flexural Test for a Monolithic Holed Web Prestressed Concrete (HWPC) Girder
Man-Yop Han,Kyung-Suk Jin,Sok-Hwan Choi 한국콘크리트학회 2010 International Journal of Concrete Structures and M Vol.4 No.2
Prestressed concrete (PSC) I-type girders have been used for span length around up to 40 m in domestic region. PSC girders are very cost effective girder type and extending their lengths more than 50 m will bring large benefit in cost. A new design method was proposed by combining two notable design concept in order to extend the applicable span length in this study. First of all, several numbers of openings was introduced in the girder web, and half of the anchorage devices were moved into the openings. In this way, large compressive stress developed at end zone was reduced, and the portion of design load coming from selfweight was reduced as well. Secondly, prestressing force was introduced in the girder not once at the initial stage, but through multiple loading stages. A full scale girder with the length of 50 m with the girder depth of 2 m was fabricated, and a flexural test was conducted in order to verify the performance of newly developed girder. Test results showed that the new holed web design concept can provide a way to design girders longer than 50 meters with the girder height of 2 m.