Time filter

Source Type

Qi K.Y.,Science and Technology on Electromechanical Dynamic Control Laboratory | Xiang C.,Shanghai Electro Mechanical Engineering Institute | Bu X.Z.,Nanjing University of Science and Technology | Shao J.Y.,Shanghai Electro Mechanical Engineering Institute
Applied Mechanics and Materials | Year: 2014

At present, traditional navigation method could not provide long-time stability attitude information for the high spinning projectile because of drift errors of micro-inertial sensors. Meanwhile, the projectile attitude measuring method with respect to the earth's magnetic field is still auxiliary. The principle of characteristic ratio algorithm and compensation model of the background magnetic field for the spinning projectile are been introduced. To realize the high accuracy attitude measuring of the projectile, a new correcting method is proposed. The detail correcting steps are derived with the linear interpolation theory and iterative algorithm. On this basis, numerical simulation is conducted combining with projectile's flight rules. The results show that the corrected attitude angles errors are within ± 0.5°, and attitude update rate increased obviously. The calculating results could better describe the whole real roll motion. The proposed correcting method is significantly effective. © (2014) Trans Tech Publications, Switzerland. Source

Chen D.,Xian University of Technology | Ke X.,Xian University of Technology | Li T.,Science and Technology on Electromechanical Dynamic Control Laboratory
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2012

Multi-Input Multi-Output (MIMO) system can greatly improve the spectrum efficiency and system capacity. Based on the analysis of MIMO system, a research on vertical stratification space-time system (V-BLAST) detection algorithm of wireless optical communication was made in depth. Firstly, several typical detection algorithms were studied as ML, ZF, MMSE and OSIC. Based on OOK and 4PPM modulation, the system BER performance using different detection algorithms was simulated. Then a new system combining Turbo and BLAST technique was put forward which used SISO iterative detection method. The simulation results show that among all layered space-time detection algorithms, the optical performance of ML is best, followed by SISO-MAP and ZF algorithm, and Turbo-BLAST system could improve the anti-jamming performance of FSO. Source

Li T.,Xidian University | Zhai H.-Q.,Xidian University | Zhu C.,Xidian University | Li L.,Xidian University | And 2 more authors.
Journal of Electromagnetic Waves and Applications | Year: 2013

A compact printed ultrawideband (UWB) antenna with dual band-notched characteristics is proposed for UWB integration communication system. The presented design, having a total size of 30×25 mm, consists of a folded fork-shaped radiator fed by a microstrip line and a modified ground plane with trapezoid-shaped slots on its top edge, which can effectively increase the bandwidth of the proposed antenna. To avoid potential interferences, a straight, open-ended quarter-wavelength slot and a semicircular half-wavelength slot are etched in the radiating patch to generate dual notched bands in 3.3-3.6 GHz for WiMAX and 5.15-5.825 GHz for WLAN. Lumped-element equivalent circuit model is carried out to comprehend and predict the dual band-notched properties. Good agreement is achieved between the simulation and measurement, which shows that the proposed antenna provides an impedance bandwidth of more than 145% between 2.7 and 17 GHz, two independently controllable notched bands and good omnidirectional radiation patterns. © 2013 Taylor & Francis. Source

Yu Y.J.,Xian Jiaotong University | Tian X.-G.,Xian Jiaotong University | Liu X.-R.,Science and Technology on Electromechanical Dynamic Control Laboratory
European Journal of Mechanics, A/Solids | Year: 2015

Ultrafast lasers, even the novel laser burst technology, have been widely using in numerous applications, especially in micro-machining. The mechanism of ultrafast laser and matter interaction, such as: heat transfer, deformation of nanostructure, has caught numerous theoretical and experimental research interests. However, in such cases the classical models of thermo-elasticity may be challenged to give accurate responses: firstly, Fourier's law of heat conduction law may break down under the high heat flux and low temperature conditions; secondly, classical elasticity may fail as the external characteristic length (or time) approaches to the internal characteristic length (or time). In this work, to simulate transient thermo-elastic responses of the nanostructure subjected to a sudden thermal loading, classical thermo-elastic models are extended in two aspects: in mechanical sense, Eringen's nonlocal elasticity (differential constitutive relations) is employed to depict the size-dependence; while the memory dependence of heat conduction is considered using Caputo fractional derivative and memory dependent derivative (MDD). In a separated section, the concept of Nonlocal operator and Memory dependent operator are proposed by revisiting Eringen's integral-type nonlocal theory, and comparing fractional calculus, MDD, and a newly reported "Most nature fractional derivative and integral". In the numerical part, a thermo-elastic medium subjected to a sudden heating at one end is considered, and an analytical technique based on Laplace transform is adopted. While the inverse Laplace transform is numerically implemented by using an efficient and pragmatic algorithm 'NILT'. Numerical results, i.e., temperature vs. position, displacement vs. position and stress vs. position, are shown graphically, and the influences of nonlocal scale parameter on them are also evaluated. It is concluded that nonlocal scale parameter's effect on the deformation and stress are significant, which is excessively important is determining material's failure when subjected to ultrafast laser like heating, although its effect on the temperature is negligible. © 2014 Elsevier Masson SAS. All rights reserved. Source

Li T.,Xidian University | Zhai H.,Xidian University | Li L.,Xidian University | Liang C.,Xidian University | Han Y.,Science and Technology on Electromechanical Dynamic Control Laboratory
IEEE Antennas and Wireless Propagation Letters | Year: 2012

A compact ultrawideband (UWB) antenna with an electronically tunable notched band is proposed for UWB communication applications. The proposed antenna utilized a C-shaped ground to realize miniaturization and a pair of open-loop resonators (OLRs) to create notched band. The center frequency of the notched band can be electronically tuned by changing the effective electrical length of the OLRs, which is achieved by employing varactor diodes. A prototype with an overall size of 24× 28 mm2 was constructed, and good agreement has been obtained between simulation and measurement. The experimental results show that, for a varactor diode capacitance approximately ranging from 0.63-2.67 pF, a continuous tuning notched band range from 5.1 to 5.9 GHz is achieved. © 2002-2011 IEEE. Source

Discover hidden collaborations