Feng X.,Xidian University |
Feng D.,Xidian University |
Li H.,Xian Electronic Engineering Research Institute
Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University | Year: 2017
In order to more effectively deal with scale changes of shapes, the scale shape descriptors (SSD) are designed by utilizing shape contexts (SC) or Gaussian shape contexts (GSC) with different scales as basis shape descriptors. Firstly, the scales of shape descriptors as intra-layer scales are determined based on the reference shape. Different inter-layer scales used to establish scale cubes of the test shape. Secondly, we calculate the mean distance between every layer of scale cubes and the test shape, and search the nearest scale of the master shape based on the mean distance. Thirdly, the spline interpolation is used to more accurately estimate the optimal scale. Then shape descriptors are built based on the optimal scale and the point to point correspondences are exactly determined on the basis of which the registration transform is calculated. Experimental results show that the SSC can well overcome the difficulties caused by scale changes in shape registration. © 2017, The Editorial Board of Journal of Xidian University. All right reserved.
Huimin L.,Xian Electronic Engineering Research Institute |
Jingya Z.,Xian Electronic Engineering Research Institute
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016
Phase coded modulation (PCM) waveform is highly Doppler sensitive. This paper studies a combined waveform called LF-PCM which adopts intra-pulse linear frequency modulation (LFM) to PCM to mitigate the impact of Doppler shift. LF-PCM is more Doppler robust than conventional PCM waveform, which makes it suitable for high speed target detection. Moreover, LF-PCM's two-dimensional Rang-Doppler resolution is finer than that of LFM waveform with equal bandwidth. © 2016 IEEE.
Ma K.,Xian Electronic Engineering Research Institute |
Yang X.,Xian Electronic Engineering Research Institute |
Gao J.,Xian Electronic Engineering Research Institute
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016
In order to meet the higher requirements of the future information warfare on the electronic RF system of tank armored platform, this paper presents that the integrated RF system should be applied to the new armored platform. The system is designed with the method of synthetic aperture; it can complete the functions such as airborne target search, precise tracking, threat assessment, electronic warfare, damage assessment. The system plays a very important role in the protection of armored platform. Firstly, the multifunction integrated RF system of armored platform is introduced. Secondly, the composition, function and characteristics of the system are analyzed in detail, and the application mode of the system is briefly described. Finally, the development suggestions are put forward for the further application of the integrated RF system in the new tank and armored platform. © 2016 IEEE.
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 | Year: 2013
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.
Man M.,Xidian University |
Lei Z.,Xidian University |
Xie Y.,Beihang University |
Wang Y.,Xian Electronic Engineering Research Institute
Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University | Year: 2012
In order to accelerate the solution procedure of scattering problems with the multilevel fast multipole algorithm, a pre-corrected method is presented. Using the Physical Optics method(PO), the PO currents could be obtained as pre-corrected currents. A rather sparse impedance matrix is generated to evaluate the PO surface current. Because the difference between unknown and PO currents is closer to the zero vectors than the unknown currents themselves, it does need less iteration steps using the difference as the unknown vector to get the solution. Numerical results demonstrate that the method could decrease the number of iterations and greatly reduce the time of solution with consistent precision.
Yang J.,Xi'an Jiaotong University |
Song T.-B.,Xi'an Jiaotong University |
Zhao Z.-H.,Xian Medical College |
Qiu S.-D.,Xi'an Jiaotong University |
And 2 more authors.
Brain Research | Year: 2011
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.
Bi H.-X.,Xi'an Jiaotong University |
Wei Z.-Q.,Xian Electronic Engineering Research Institute
International Journal of Remote Sensing | Year: 2016
Phase unwrapping is a key step in retrieving digital elevation models (DEMs) from across-track interferometric synthetic aperture radar (InSAR) data. The coherence of synthetic aperture radar (SAR) data set is an effective indicator for the quality of phase unwrapping. However, the coherence of different regions usually distributes unevenly in SAR images monitoring heterogeneous areas. Errors in low-coherence areas are prone to pollute the whole image. In order to mitigate propagation error, a new phase unwrapping algorithm based on region recognition and region expansion is proposed. In the region recognition step, optical images are incorporated to recognize low-coherence regions by virtue of supervised classification technique. Low-coherence regions and the ones that are not of interest for the application are then discarded. In the region expansion step, stable pixels of high coherence are selected as growing seeds, and then phase unwrapping grows from high-quality regions to low-quality ones guided by coherence information and weighted numbers of neighbouring unwrapped pixels. The ambiguity number of a wrapped pixel is estimated from its neighbouring pixels under the criteria of pixel distance and phase gradient. Iterative examination continues until the whole image is unwrapped. Experiments on PALSAR and ASAR data demonstrate its validity and advantages over other classical methods. © 2016 Informa UK Limited, trading as Taylor & Francis Group.
Ji Y.-X.,Xian Electronic Engineering Research Institute |
Xu J.,Nanjing University of Science and Technology
Journal of Electromagnetic Waves and Applications | Year: 2014
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.
Zhou H.-J.,Xian Electronic Engineering Research Institute |
Wu H.F.,Xian Electronic Engineering Research Institute
Progress in Electromagnetics Research Letters | Year: 2013
In this article, an S-band two-way inverted asymmetrical Doherty power amplifier (IADPA) using LDMOS FET is proposed. Due to the compact inverted load network with low inserted loss and the asymmetrical structure, the amplifier exhibits a high effciency when operating at an output power back-off beyond 6 dB. For experimental verification, an IADPA has been implemented and a modulated Long Term Evolution (LTE) signal with 20-MHz channel bandwidth is applied as excitation. According to the measured results, the proposed amplifier can achieve a drain effciency of 47.6% at the output power back-off of 7.7 dB from saturated power point and an adjacent channel power ratio (ACPR) less than -53 dBc with digital pre-distortion (DPD) when operating at 2.65 GHz.
Bin L.,Xian Electronic Engineering Research Institute |
Liang D.,Xian Electronic Engineering Research Institute |
Jiao-Cheng Z.,Xian Electronic Engineering Research Institute
2010 International Conference on Microwave and Millimeter Wave Technology, ICMMT 2010 | Year: 2010
A compact millimeter wave Vivaldi antenna array printed on thick substrate and fed by a substrate integrated waveguide (SIW) structure was proposed in this paper. It consists of a compact SIW binary divider, which has minimize significantly the feed structure insertion losses and achieve a broadband performance in millimeter wave range, and four-elements printed Vivaldi array. The whole antenna array was designed, fabricated, and thoroughly investigated. The whole antenna and feed net were designed, fabricated on single substrate, which takes the advantages of small size, low profile, low cost and high performance etc. The simulation results show that the design is effective and right. © 2010 IEEE.