Time filter

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Liu J.,China Shipbuilding Industry Corporation | Wu C.,Air Force Early Warning Academy
Lecture Notes in Electrical Engineering | Year: 2017

Due to the great success, deep learning gains much attentions in the research field of recommendation. In this paper, we review the deep learning based recommendation approaches and propose a classification framework, by which the deep learning based recommendation approaches are divided according to the input and output of the approaches. We also give the possible research directions in the future. © Springer Nature Singapore Pte Ltd. 2017.

Hu B.,Air Force Early Warning Academy | He N.,Wuhan University of Technology
Advanced Materials Research | Year: 2013

The paper puts forward an algorithm base on the strategy of sensor node's dynamic clustering which also combined the method of particle filter to track the target. The simulation shows that the algorithm efficiently reduces the amount of communication between the redundant nodes and sensor nodes, decreases the energy consumption of the entire network, extends the network life span and improves the tracking accuracy. © (2013) Trans Tech Publications, Switzerland.

Zhan L.-X.,The Academy of Management | Tang Z.-Y.,Air Force Early Warning Academy | Zhu Z.-B.,Air Force Early Warning Academy
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2013

The signal-to-noise ratio(SNR) of small radar cross section(RCS) targets can be improved by coherent integration. But the maneuvering of targets causes range cell migration and Doppler cell migration. The reasons of above problems are analyzed from the two-dimensional(2-D) frequency domain, and based on this, a novel method of long term coherent integration is proposed. In fast frequency-slow time domain the Keystone transform is taken and the range cell migration is corrected, then a quadratic phase compensation function is multiplied and the objective function is constructed to search the acceleration in the compensation function. The characteristic of the new method is that the maximum value of the objective function equals to the coherent integration value, and this reduces the operational quantity and improves the operation speed. The simulation results verify the effectiveness of the proposed method.

Luo H.,The Academy of Management | Chen J.-W.,Air Force Early Warning Academy | Bao Z.,Air Force Early Warning Academy
Dianzi Yu Xinxi Xuebao/Journal of Electronics and Information Technology | Year: 2013

Skywave Over-The-Horizon Radar (OTHR) can achieve long range detection via the ionosphere reflection. However, time-varying ionosphere and multipath effect will lead to serious clutter spectrum spread in long Coherent Integration Time (CIT). It increases difficulty degree of the detection of slow-speed targets. To deal with contaminated echo in the case of the two spreading Bragg peaks overlapping, an ionospheric contamination correction scheme based on Short Time MUSIC Transform (STMT) and improved Phase Gradient Autofocus (PGA) method is proposed. In the scheme, coarse estimation of ionospheric phase contamination can be obtained and compensated by using STMT transform, then an adaptive sliding window filter is utilized to extract the first order clutter (calibration signal). After that, the remanent ionospheric phase contamination can be estimated and compensated accurately by using improved PGA method. Theoretical analysis and simulation results show that the scheme has a good performance on correcting the situation of two spreading Bragg peaks overlapping.

Wang Q.-B.,Wuhan University | Zhou C.,Air Force Early Warning Academy | Chen L.,Wuhan University | Wang X.-C.,Wuhan University | He K.-H.,Wuhan University
Optics Communications | Year: 2014

To comprehend the optical properties of the recent-predicted NiAs phase ZnO under pressure, we used the generalized gradient approximation plus U (GGA+U) method to calculate the properties. The GGA+U method is more suited for the strong correlated NiAs phase. The direct band gap increases with increasing pressure. The calculated band gap shows that NiAs phase is an insulator, while the real part ε1(ω) shows the NiAs phase expresses metallic behavior around 18.6 (22.5 GPa) and 26.0 eV (215 GPa). The relation between the imaginary part ε2(ω) and PDOS was also discussed. The calculated optical constants show the NiAs phase is transparent and can be used in the vacuum ultraviolet region. We also compared the optical constants of NiAs with wurtzite and CsCl phases ZnO at according transition pressure. And the new-appeared peaks of optical constants can be used to identify the phase transition. The blue-shift optical constants of NiAs phase ZnO can be used to measure pressure after carefully calibrated. Our research provides a reference for identifying and using the NiAs phase ZnO under pressure. © 2013 Elsevier B.V.

Wang Q.-B.,Wuhan University | Zhou C.,Air Force Early Warning Academy | Wu J.,Wuhan University | Lu T.,Wuhan University
Optics Communications | Year: 2013

Using the GGA+U method, we have calculated the optical properties of vanadium (V) doped ZnO with and without single intrinsic (zinc or oxygen) vacancy. Vanadium introduces a new band in the band gap. The new band betters conduction and causes a red shift of the optical properties. Vanadium causes a weak absorption in the infrared region. Zinc vacancy suppresses the infrared absorption and shifts absorption to higher energy. Besides the infrared absorption, oxygen vacancy causes an intense absorption in the visible and near-ultraviolet region. Our study explains the different experiments and extends the use of V-doped ZnO. © 2013 Elsevier B.V.

Chen Y.,National University of Defense Technology | Huang Y.,National University of Defense Technology | Chen X.,National University of Defense Technology | Hu D.,Air Force Early Warning Academy
Journal of Computational Acoustics | Year: 2014

This paper deals with the axisymmetric acoustic wave propagating along the perfect gas in the presence of a uniform flow confined by a rigid-walled pipeline. Under the linear acoustic assumption, mathematical formulation of wave propagation is deduced from the conservations of mass, momentum and energy. Meanwhile a method based on the Fourier-Bessel theory is introduced to solve the problem. Comprehensive comparisons of the phase velocity and wave attenuation between the non-isentropic and isentropic acoustic waves are provided. Meanwhile the effects of flow profile, acoustic frequency, and pipeline radius are analyzed. © 2014 IMACS.

Zheng W.C.,Huazhong University of Science and Technology | Zhang L.,Huazhong University of Science and Technology | Li Q.X.,Huazhong University of Science and Technology | Leng Y.,Air Force Early Warning Academy
IEEE Transactions on Antennas and Propagation | Year: 2014

Smart antennas have received increasing interest for mitigating interference in the multiple-input-multiple-output (MIMO) wireless local area network (WLAN). In this paper, a dual-band dual-polarized compact bowtie dipole antenna array is proposed to support anti-interference MIMO WLAN applications. In the antenna array, there are 12 antennas, six for horizontal polarization and six for vertical polarization. In order to achieve dual linear polarizations and beam switching, six horizontal antennas are placed in a sequential, rotating arrangement on a horizontal substrate panel with an equal inclination angle of 60° to form a symmetrical structure, while the other six antennas for vertical polarization are inserted through slots made on the horizontal substrate panel. Furthermore, six pairs of meandered slits are introduced to reduce the mutual coupling between horizontal antennas in the lower band. A prototype of the array with a dimension of 150×150×60mm3 is manufactured and exhibits the characteristics of high isolation, good front-to-back ratio, and average gains of 4.5 and 5 dBi over the 2.4- and 5-GHz band, respectively. The MIMO performance of the array is analyzed and evaluated by mutual coupling, the total active reflection coefficient (TARC) and the envelope correlation coefficient. The anti-interference capability of the array is also investigated by the experiment. © 2013 IEEE.

Yao H.-Y.,Air Force Early Warning Academy | Sun W.-F.,Air Force Early Warning Academy | Ma X.-Y.,Air Force Early Warning Academy
Dianzi Yu Xinxi Xuebao/Journal of Electronics and Information Technology | Year: 2013

Feature parameters estimation for ballistic targets is the basis of target recognition. Because of the difficulty to estimate the precession and structure parameters of a cone-cylinder target jointly without prior knowledge of parameters, a new method for the cone-cylinder target's precession and structure parameters estimation is proposed based on High Range Resolution Profile sequences (HRRPs). The HRRPs of the rotary symmetrical cone-cylinder target are simulated and analyzed in four attitude angle regions respectively based on static electromagnetic scattering data. The trace of each scatter in the HRRPs is researched in the common radar viewing aspect, and the relationship between the extreme value of three scattering centers' relative positions in the HRRPs and the target's parameters is built, then the precession and structure parameters are estimated simultaneously. Finally, the estimation results of feature parameters show that the proposed method is effective and adaptive.

Li S.-D.,Air Force Early Warning Academy | Yang J.,Air Force Early Warning Academy | Ma X.-Y.,Air Force Early Warning Academy
Tongxin Xuebao/Journal on Communications | Year: 2013

According to the problem that conventional imaging algorithms have some unavoidable shortcomings such as low resolution of image and being fragile to the noise with short coherent processing interval (CPI), an improved ISAR imaging algorithm via CS method, namely, PH-SL0 algorithm, was proposed. In the proposed algorithm, as a kind of measure matrix, partial randomizer Hadamard matrix (PH) has many advantages such as high reconstruction precision and low dimension of measure matrix. Meanwhile, as a reconstruction algorithm, SL0 has many advantages such as demanding fewer measurements than existing methods, having higher reconstructed accuracy and better robust. Therefore, making use of the advantages of PH and SL0, and extending them to the field of radar, the azimuth imaging with short imaging data could be implemented. Finally, simulation results and experimental results of real data show that the algorithm has higher imaging resolution and better robust to noise.

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