4,101 research outputs found
Aeroelastic analysis of bearingless rotors using large deflection beam theory
No full textThe aeroelastic response and stability of bearingless rotors are investigated using large deflection beam theory. The bearingless rotor configuration consists of a single flexbeam with a wraparound-type torque tube and pitch links located at the leading edge and trailing edge of the torque tube. The outboard main blade, flexbeam, and torque tube are all assumed to be an elastic beam undergoing arbitrary large displacements and rotations, which are discretized into beam finite elements. The finite element equations of motion for beams are obtained from Hamilton's principle. Two-dimensional quasi-steady strip theory is used to evaluate aerodynamic forces in both hover and forward flight. For the analysis of hover flight, the nonlinear equations of motion are solved for an equilibrium position through an iterative procedure. The modal approach method based on coupled rotating natural modes is used for the stability analysis. For the analysis of forward flight, the nonlinear periodic blade steady response is obtained by integrating the full finite element equation in time through a coupled trim procedure with a vehicle trim. After the coupled trim response is computed, the aeroelastic response is calculated through a time-marching solution procedure under small perturbations assumption. A stability analysis is then performed using a moving block analysis. The results of the full finite element analysis using the large deflection beam theory are quite different from those of a previously published modal analysis using the moderate deflection-type beam theory.This research was supported by the Brain Korea 21 Project (BK21) in 2006
Gasification of glucose in Supercritical water
No full textGasification of 0.6 M glucose in supercritical water was investigated at a temperature range from 480 to 750 degreesC and 28 MPa with a reactor residence time of 10-50 s. The yield of hydrogen among gaseous products increased very sharply with increasing temperature above 660 degreesC. On the other hand, the yield of carbon monoxide decreased with temperature, most probably due to the role of a water-gas shift reaction. Carbon gasification efficiency reached 100% at 700 degreesC. A simplified model was proposed for the reaction pathways related to hydrogen production. The rates for glucose conversion and COD degradation were obtained by assuming pseudo-first-order kinetics
Modulation of Toll-like receptor activity by leukocyte Ig-like receptors and their effects during bacterial infection.
No full textToll-like receptors (TLRs) are a potent trigger for inflammatory immune responses. Without tight regulation their activation could lead to pathology, so it is imperative to extend our understanding of the regulatory mechanisms that govern TLR expression and function. One family of immunoregulatory proteins which can provide a balancing effect on TLR activity are the Leukocyte Ig-like receptors (LILRs), which act as innate immune receptors for self-proteins. Here we describe the LILR family, their inhibitory effect on TLR activity in cells of the monocytic lineage, their signalling pathway, and their antimicrobial effects during bacterial infection. Agents have already been identified which enhances or inhibits LILR activity raising the future possibility that modulation of LILR function could be used as a means to modulate TLR activity
The future of e-government: Collaboration across citizen, business, and government
No full textGovernments in many countries have been implementing egovernment for the purpose of better service delivery to citizen, better environments for businesses, and more efficient and transparent public administration. However, most implementations of e-government have provided temporary approaches rather than holistic view for citizen-oriented service level. In this paper, we intend to suggest three main directions that must be taken for better egovernment in the future
Throughput analysis of IEEE 802.11e wireless LANs and efficient Block Ack mechanism
No full textIn the recent draft of the 802.1 le MAC [2], the Hybrid Coordinator (HC) gives transmission opportunity (TXOP) for a station to transmit burst frames in TXOP for improving throughput efficiency. In this paper. we express the expected throughput for the Block Ack policy in Polled TXOP as a closed form function of the number of burst MSDUs, the number of fragmented MPDUs, the data payload length, the frame retry count. the wireless channel condition, and the selected PHY mode. Based on our simulation study and analysis, we show that the TXOP and proper Ack policy can enhance system performance, and that there are the Block Ack efficient block size and frame length to transmit the burst frames for each PHY mode. Moreover, we also show that when the Block Ack mechanism is combined with link adaptation. it has better throughput performance
Photon Collection from Wavelength-scale Photonic Crystal Light Emitters (Plenary speaker)(Invited)
No full textElectronic and magnetic properties in Fe-based Fe1-xNix, Fe1-xCox, and Fe1-xVx films on W(110)
No full textWe investigate the correlation between the change of magnetic properties and structural transition for Fe-based alloy (Fe1-xNix, Fe1-xCox, and Fe1-xVx) films, which were grown on W(110) substrate. To clarify the correlation clearly among the electronic structure, magnetic properties, and structural transition as a function of alloy composition, we performed the spin-summed and resolved photoemission spectra (SSRPES) and low energy electron diffraction (LEED). (c) 2006 Elsevier B.V. All rights reserved.KOSEF through the Center for Nanotubes and Nanostructured Composites, the Brain Korea 21 Project, the Advanced Backbone IT Technology Development Project, and the National R&D Project for Nano Science and Technology
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