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Yang M.,Nanjing Southeast University | Yin X.,Nanjing Southeast University | Chen Z.N.,National University of Singapore | Rong Y.,Science and Technology on Near Surface Detection Laboratory | Qian H.,Science and Technology on Near Surface Detection Laboratory
IEEE Antennas and Wireless Propagation Letters | Year: 2016

A planar bow-tie antenna loaded with open stubs is proposed to realize image rejection and gain enhancement for superheterodyne applications. The loading open stubs are two open-circuit double-sided parallel-strip lines symmetrically connected to the feedline of a planar bow-tie antenna, which functions as a bandstop filter in frequency band lower than the operating frequency to reject image interference and simultaneously as a reflector across the operating frequency band to enhance the antenna gain. Simulated results show that the realized gain of the proposed antenna in the main radiation direction is suppressed by 25 dB at the image frequency and is enhanced by about 3 dB at the operating frequency compared to that of an unloaded antenna. Good agreements between the simulated and the measured results have been observed. © 2015 IEEE.


Zhu Y.,Science and Technology on Near surface Detection Laboratory | Zheng S.,Science and Technology on Near surface Detection Laboratory
Proceedings - 7th Asia-Pacific Conference on Environmental Electromagnetics, CEEM 2015 | Year: 2015

Rotating parabolic reflector antenna combined with parachute is designed to have a parachute-type high power EMP radiator. With EM array complementary radiation as the design idea, a four-feed-arm parachute-type reflector antenna structure with higher feeding efficiency is proposed, thus to strengthen the low-frequency radiating capacity, widen the bandwidth of antenna and improve the radiant efficiency of antenna; a balanced feeding structure is also adopted to strengthen the radiating capacity. The results showed that parachute-type radiator is superior to TEM horn antenna in both peak-to-peak value of field strength and effective bandwidth of radiation field, thus making effective radiation of high-power UWB-EMP come true. © 2015 IEEE.


Yang C.H.,Nanjing University of Information Science and Technology | Shen G.Z.,Nanjing University of Information Science and Technology | Ao Z.M.,Guangdong University of Technology | Xu Y.W.,Science and Technology on Near Surface Detection Laboratory
Materials Research Express | Year: 2016

Using the transfer matrix method, the carrier tunneling properties in graphene superlattice generated by the Thue-Morse sequence and Kolakoski sequence are investigated. The positions and strength of the transmission can be modulated by the barrier structures, the incident energy and angle, the height and width of the potential. These carriers tunneling characteristic can be understood from the energy band structures in the corresponding superlattice systems and the carrier's states in well/barriers. The transmission peaks above the critical incident angle rely on the carrier's resonance in the well regions. The structural diversity can modulate the electronic and transport properties, thus expanding its applications. © 2016 IOP Publishing Ltd.


Qi H.,Nanjing Southeast University | Yin X.,Nanjing Southeast University | Liu L.,Nanjing University of Posts and Telecommunications | Rong Y.,Science and Technology on Near Surface Detection Laboratory | Qian H.,Science and Technology on Near Surface Detection Laboratory
IEEE Antennas and Wireless Propagation Letters | Year: 2016

This letter introduces an effective solution for improving isolation between closely spaced patch antennas. A satisfactory isolation is realized by three interdigital lines that excite an orthogonal polarization mode on the adjacent patch. A two-patch array is simulated and fabricated to verify the decoupling effectiveness of the proposed structure. The investigations of the electric field and current distributions reveal the working mechanism of the proposed structure. The experimental results show that the achieved isolation is better than 20 dB, and the maximum isolation enhancement is 24.7 dB, with a compact edge-to-edge separation of just 0.07λ0. Moreover, the proposed structure can also be applied for the decoupling of a multielement patch array. © 2002-2011 IEEE.


Shen G.,Nanjing University of Information Science and Technology | Xu Y.,Science and Technology on Near Surface Detection Laboratory | Liu B.,Nanjing University of Information Science and Technology
Desalination and Water Treatment | Year: 2016

Carbon materials are effective for removal of both toxic inorganic and organic substances. In this study, a novel magnetic mesoporous carbon aerogel which combined high specific surface area, adsorption capacity and magnetic property of Fe3C was prepared by citrate sol-gel method. The as-prepared samples were characterized by powder X-ray diffraction, TEM, scanning electron microscope, and BET methods. Results show that the aerogel has the specific surface and average pore size of 290 m2/g and 2.7 nm, respectively. Magnetic Fe3C nanoparticles were dispersed uniformly in carbon matrix and exhibit excellent response to an external magnetic field. As a result, the adsorbent can be easily separated from solution using an external magnetic field. Batch experimental results on As(V) removal showed that the adsorption kinetics and isotherm data were fitted well by a pseudo-second-order model and a Freundlich model, respectively. The monolayer adsorption capacity (qm) of the adsorbent was calculated to be 56.2 mg/g at pH 7.0. The excellent uptake capability of the magnetic mesoporous materials make it be potentially attractive materials for removal of hazardous substances from water. © 2016 Balaban Desalination Publications. All rights reserved.


PubMed | Wuhan University and Science and Technology on Near Surface Detection Laboratory
Type: Journal Article | Journal: Sensors (Basel, Switzerland) | Year: 2016

Based on the dynamic nuclear polarization (DNP) effect, an alternative design of an Overhauser geomagnetic sensor is presented that enhances the proton polarization and increases the amplitude of the free induction decay (FID) signal. The short-pulse method is adopted to rotate the enhanced proton magnetization into the plane of precession to create an FID signal. To reduce the negative effect of the powerful electromagnetic interference, the design of the anti-interference of the pick-up coil is studied. Furthermore, the radio frequency polarization method based on the capacitive-loaded coaxial cavity is proposed to improve the quality factor of the resonant circuit. In addition, a special test instrument is designed that enables the simultaneous testing of the classical proton precession and the Overhauser sensor. Overall, comparison experiments with and without the free radical of the Overhauser sensors show that the DNP effect does effectively improve the amplitude and quality of the FID signal, and the magnetic sensitivity, resolution and range reach to 10 pT/Hz 1 / 2 @1 Hz, 0.0023 nT and 20-100 T, respectively.


Xu P.,Wuhan Naval University of Engineering | Xu P.,Science and Technology on Near Surface Detection Laboratory | Yan B.,Wuhan Naval University of Engineering | Hu S.,Science and Technology on Near Surface Detection Laboratory
Cluster Computing | Year: 2016

An algorithm to improve direction of arrival (DOA) estimation accuracy with an extended sensor array in the presence of multiple coherent signal sources is proposed. The algorithm uses virtual element theory to extend the sensor array, estimates virtual element information via linear prediction and expands the array aperture in practical sense; the sparsity of the target orientation in angle space is exploited to establish an over-complete dictionary and a reception model for the array signal in sparse space; the received array data is preprocessed using singular value decomposition (SVD) method and target DOA estimation is realized by calculating the best atoms. The algorithm improves DOA estimation accuracy by extended array and uses SVD to control computational complexity effectively, which ensures the accuracy and efficiency. Computer simulation shows that the proposed algorithm is able to accurately estimate the DOA for both single-target and closely spaced multi-target cases in low signal-to-noise ratio environments, and also has excellent DOA estimation performance in the presence of multiple coherent signal sources. © 2016 Springer Science+Business Media New York


Sun H.-T.,National University of Defense Technology | Chang W.-G.,National University of Defense Technology | Liu Z.-H.,Science and Technology on Near Surface Detection Laboratory
2015 IEEE International Conference on Communication Problem-Solving, ICCP 2015 | Year: 2015

Throwing-mine detection is a typical problem of low RCS (radar cross section) targets detection in heavy clutter, in which the high false alarm rate is a difficult problem. Classical CFAR (Constant False Alarm Rate) detection algorithm only utilizes the image contrast characteristics, in the case of low SNR (Signal to Noise Ratio), a large number of false alarms generates. In order to further reduce false alarm rate, CFAR-IHP (Constant False Alarm Rate-Internal Hermitian Product) detection algorithm is proposed in this paper. CFAR-IHP is based on CFAR and target azimuth coherence characteristic, therefore, we first get the sub-aperture image sequence to extract target azimuth information by the sub-aperture processing algorithm for SAR image. Lastly, based on Ku-band SAR data, we use CFAR-IHP (Constant False Alarm Rate-Internal Hermitian Product) algorithm to detect the targets, experimental results show that the method further eliminate the clutter and the azimuth coherence helpfully reduces the false alarms.


Gu C.,National University of Defense Technology | Chang W.,National University of Defense Technology | Li X.,National University of Defense Technology | Liu Z.,Science and Technology on Near Surface Detection Laboratory
Radioengineering | Year: 2015

This paper presents an efficient parallel processing architecture using multi-core Digital Signal Processor (DSP) to improve the capability of real-time imaging for Frequency Modulated Continuous Wave Synthetic Aperture Radar (FMCW SAR). With the application of the proposed processing architecture, the imaging algorithm is modularized, and each module is efficiently realized by the proposed processing architecture. In each module, the data processing of different cores is executed in parallel, also the data transmission and data processing of each core are synchronously carried out, so that the processing time for SAR imaging is reduced significantly. Specifically, the time of corner turning operation, which is very time-consuming, is ignored under computationally intensive case. The proposed parallel architecture is applied to a compact Ku-band FMCW SAR prototype to achieve real-time imageries with 34 cm × 51 cm (range × azimuth) resolution.


Jia G.,National University of Defense Technology | Chang W.,National University of Defense Technology | Zhang Q.,National University of Defense Technology | Luan X.,Science and Technology on Near Surface Detection Laboratory
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2016

Regarding the two-dimensional (2-D) imaging processing of circular synthetic aperture radar (CSAR), the motion compensation (MOCO) in the frequency domain is not fully developed. To perform the MOCO for CSAR data in the frequency domain, a novel three-step strategy is presented in this paper. The motion error model is established first, and it is found that a difficulty of MOCO for CSAR lies in the space variance of the motion errors. Specifically, according to the proposed MOCO strategy, this first step is space-invariant MOCO, the second step is space-variant MOCO in the range-compressed angular-wavenumber domain with respect to subaperture data, and the last step is the autofocus operation in the 2-D wavenumber domain after the polar format resampling. Eventually, the complete MOCO flowchart is obtained. Simulation and experimental tests verify that the proposed motion error model is valid and the three-step MOCO strategy can remove motion errors accurately and figure out well-focused CSAR images. © 2008-2012 IEEE.

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