Kwangwoon University

About: Kwangwoon University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Thin film & Resonator. The organization has 4020 authors who have published 8217 publications receiving 104365 citations.

A Single-Chip CMOS Transceiver for UHF Mobile RFID Reader

Abstract: A UHF mobile RFID single-chip reader is implemented in a 0.18mum CMOS technology. The reader IC integrates an RF transceiver, a digital baseband modem, an MPU and host interfaces in 4.5 times 5.3mm2. The RF transceiver draws 61mA from a 1.8V supply and achieves an 8dBm P1dB, an 18.5dBm IIP3, and a 4dBm TX power.

Peak-Seeking Control for Drag Reduction in Formation Flight

Abstract: Formation flight is a known method of improving the overall aerodynamic efficiency of a pair of aircraft. In particular, one craft flying in the correct position in the vortex wake of another can realize substantial reductions in drag, with the amount of the reduction dependent on the relative positions of the two craft. This paper looks at such a pair, with one craft flying behind and to the side of the lead plane. The precise position of the second craft relative to the first to maximize the drag reduction is to be determined online, leading to a peak-seeking control problem. A new method of speak-seeking control, using a Kalman filter to estimate the characteristics of the drag reduction, is derived and discussed. A simple model of the two-plane formation using horseshoe vortices is defined, and the peakseeking controller is applied to this model. The method is demonstrated in simulation using this simplified model. S an airplane flies, it causes an upwash ahead of the wing and leaves a wake behind. This wake is characterized by the downwash behind the wing and by an accompanying upwash in the area on either side of the downwash region. By flying in the area of upwash, a second aircraft can gain a substantial efficiency boost because of the reduction in induced drag it will experience. This leads to the well-known fact that two aircraft flying in an appropriate formation can achieve overall efficiency much greater than were they flying separately. 1 This effect is analyzed using inviscid aerodynamic assumptions and lifting-line theory in Ref. 2, where it is noted that the effects were considered by Munk as early as 1919. The theory was put to test in actual aircraft by Hummel, 3 who established a fifteen per cent reduction on the second of a pair of civilian aircraft. Because of the gains in efficiency, formation flight has been investigated as a way of increasing the range and duration of autonomous aerial vehicles. In Refs. 4 and 5, formations of several aircraft are considered, with the object of creating a solar-powered formation that could cruise at high altitude for arbitrarily long times. In Ref. 4, decentralized controllers are derived for a formation of five highaspect-ratio craft and are shown to be capable of maintaining a prescribed formation despite the nonlinear, destabilizing moments induced on each plane by the aircraft ahead of it in the formation. The formation maintenance problem for a pair of F-16 class aircraft is considered in Ref. 6, though that paper relegates the rolling moments on the trailing craft to an inner-loop controller and considers only the lift and side force in designing an autopilot for the trailing plane. In this paper, only a pair of aircraft is considered. The two craft can be thought of as a leader and a follower. The leader flies straight

Effects of acetic and formic acid on ABE production by Clostridium acetobutylicum and Clostridium beijerinckii

Abstract: The effect of acetic acid and formic acid on acetone-butanol-ethanol (ABE) production by solventogenic Clostridia was investigated. The ABE concentration in Clostridium acetobutylicum was found to have increased slightly on addition of 3.7 ∼ 9.7 g/L acetic acid, but was found to have drastically reduced in the presence of 11.7 g/L acetic acid. However, the solvent production of C. beijerinckii was not affected by addition of acetic acid in the range of 3.7 ∼ 11.7 g/L. C. acetobutylicum was more vulnerable to formic acid than C. beijerinckii. In C. acetobutylicum, the total ABE production decreased to 77% on addition of 0.4 g/L formic acid and 25% with 1.0 g/L formic acid. The total ABE production by C. acetobutylicum was also noted to have decreased from 15.1 to 8.6 g/L when 8.7 g/L acetic acid and 0.4 g/L formic acid co-existed. The solvent production by C. beijerinckii was not affected at all under the tested concentration range of formic acid (0.0 ∼ 1.0 g/L) and co-presence of acetic acid and formic acid. Therefore, C. beijerinckii is more favorable than C. acetobutylicum when the ABE is produced using lignocellulosic hydrolysate containing acetic and formic acid.