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Zhang Y.-M.,Shaanxi Normal University | Wu X.-J.,Shaanxi Normal University | Bai S.-L.,Xian Electronic Engineering Research Institute | Bai S.-L.,Northwestern Polytechnical University
Wuli Xuebao/Acta Physica Sinica

Time delay and optimal embedding dimension for the real measurement traffic flow series, which are used by mutual information method and false nearest-neighbor method, respectively, are determined for phase space reconstruction of the traffic flow series. The saturation correlation dimension and the largest Lyapunov exponent for traffic flow series are calculated to estimate its chaotic characteristics. Based on the least mean square (LMS) algorithm, a novel second-order Volterra model using Davidon-Fletcher-Powell method (DFPSOVF) is constructed, in which a variable convergence factor based on a posteriori error assumption, characteristic of real-time change with the input signal, is applied. DFPSOVF model can avoid some problems caused by improper selection of parameters when using LMS adaptive algorithm for coefficient adjustment in Volterra model. DFPSOVF model can also be applied to short-term traffic flow prediction with chaotic characteristics. Results show that when model memory length is consistent with embedding dimension of traffic flow series, it obtains higher prediction accuracy, which can meet the needs for traffic guidance and traffic control, and can also provide a new method, a new idea and engineering application reference for intelligent traffic control. © Chinese Physical Society. Source

Nie J.-X.,Beijing Institute of Technology | Han J.-J.,Beijing Institute of Nearspace Vehicles System Engineering | Jiao Q.-J.,Beijing Institute of Technology | Jin Z.-X.,Xian Electronic Engineering Research Institute | Zhang F.,Beijing Institute of Technology
Gaodianya Jishu/High Voltage Engineering

Inductance gradient is an important parameter to influence efficiency of rail-type electromagnetic launcher (EML), which is mainly controlled by geometrical parameters of launcher structure. Considering skin effect of current distribution on rails during launching, on the basis of Biot-Savat law, an analytic expression of inductance gradient was derived for rail-type EML with rectangular bore. The effects of structure geometrical parameters on inductance gradient were investigated by numerical simulations, and compared with other formulae of inductance gradient. The results show that inductance gradient decreases by about 20% when the ratio of rail thickness to rails interval changes from 1/3 to 1 for small-bore EML. Because of fully considering the influence of rails and armature dimensions, theoretical inductance gradient formula presented accords with the fact well. Source

Hu C.X.,Tsinghua University | Hu C.X.,Xian Electronic Engineering Research Institute | Liu Y.M.,Tsinghua University | Li G.,Tsinghua University | Wang X.Q.,Tsinghua University
Science China Information Sciences

The high resolution imaging of distributed targets in millimeter-wave radar system is studied in this paper. We use Gaussian Mrakov random field (GMRF) to represent the clustering property of the targets. Our novel method, called Clustering FOCUSS, incorporate an additional cluster constraint into the process of the focal underdetermined system solver (FOCUSS) algorithm. Simulation results indicate that the novel algorithm has a higher imaging accuracy than the methods of Capon beamforming, the l 1 norm algorithm and the FOCUSS algorithm. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg. Source

Ji Y.-X.,Xian Electronic Engineering Research Institute | Xu J.,Nanjing University of Science and Technology
Journal of Electromagnetic Waves and Applications

This paper presents a novel capacitively loaded λ/4 shorted meander line resonator (SMLR). The grounded microstrip lines inserted inside the spaces of SMLR can construct the grounded inter-digital capacitors, which leads to a lower fundamental resonance frequency of capacitively loaded λ/4 SMLR than the λ/4 SMLR. Based on the proposed resonator, two compact fourth order Chebychev response bandpass filters (BPFs) centered at 0.9/1.57 GHz with 3 dB fractional bandwidth (FBW) of 12.5%/15% is designed and fabricated firstly. Then, on the basis of these two BPFs, a BPF-based diplexer operating at 0.9/1.57 GHz with 3 dB FBW of 12.5%/15% is exploited. The designed diplexer employs a novel hybrid microstrip line and phase shifter common T-junction. The phase shifter is implemented by quasi-lumped elements. The designed diplexer exhibits a very high isolation up to 73/68 dB at two channels, respectively. The fabricated diplexer also has a compact size of 0.239λg × 0.06λg. Good agreement can be observed between the simulations and the measurements. © 2013 Taylor & Francis. Source

Yang J.,Xian Jiaotong University | Song T.-B.,Xian Jiaotong University | Zhao Z.-H.,Xian Medical College | Qiu S.-D.,Xian Jiaotong University | And 2 more authors.
Brain Research

Vasoactive intestinal peptide (VIP) exerts neuroprotective effects under various neurotoxic conditions in vitro. In the present study, we investigated the effects of VIP on transient ischemic brain damage. Focal cerebral ischemia was induced using middle cerebral artery occlusion (MCAO) for 120 min in the adult rat brain. Either a single intracerebroventricular injection of VIP or saline was given at the beginning of reperfusion. Forty-eight hours after MCAO, the rats were sacrificed for evaluation of the infarct volume and histological analysis. ELISA was performed to assay levels of serum S100B before being sacrificed. We also evaluated the blood-brain barrier (BBB) permeability using Evans blue dye injection method. In contrast to the cases treated with vehicle, the infarct volume was significantly (P < 0.05) reduced, and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining and immunoreactivity for S100B were also significantly (P < 0.05) decreased in the ischemic hemisphere with VIP treatment. In addition, the elevations of serum S100B were significantly (P < 0.01) attenuated in VIP-treated rats compared with those of control rats. Treatment with VIP did not result in a significant reduction of Evans blue leakage, although it tended to be lower than that in the control rats. Our data suggest that treatment with VIP reduces brain damage in ischemic rats, and this effect may be associated with the attenuation of apoptosis and S100B expression. © 2011 Elsevier B.V. All rights reserved. Source

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