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Abstract-The discrete fractional Fourier transform is a powerful signal processing tool with broad applications for nonstationary signals. In this paper, we propose a sparse discrete fractional Fourier transform (SDFrFT) algorithm to reduce the computational complexity when dealing with large data sets that are sparsely represented in the fractional Fourier domain. The proposed technique achieves multicomponent resolution in addition to its low computational complexity and robustness against noise. In addition, we apply the SDFrFT to the synchronization of high dynamic direct-sequence spread-spectrum signals. Furthermore, a sparse fractional cross ambiguity function (SFrCAF) is developed, and the application of SFrCAF to a passive coherent location system is presented. The experiment results confirm that the proposed approach can substantially reduce the computation complexity without degrading the precision.Index Terms-Cross ambiguity function, global positioning system, passive bistatic radar, sparse discrete fractional Fourier transform.

The ZiYuan‐3 surveying satellite (ZY‐3), launched on 9th January 2012, is China's first civilian high‐resolution stereo mapping satellite. To ensure the mapping accuracy of ZY‐3, considerable research has been conducted since its launch on the calibration and validation of its three‐line array charge‐coupled device (CCD) sensors (TLC sensors). Its dynamic exterior systematic errors (such as camera installation errors) and static interior distortion were eliminated using 1:2000 digital orthophotomaps and digital elevation models (DEMs) of the Dengfeng (Henan) and Tianjin areas of China as control data. Various CCD alignment calibration models were compared, on the basis of their geometric accuracy after calibration, to determine the optimal model. Finally, validation experiments were performed using ZY‐3 TLC images and ground control points (GCPs) collected over Anping in Hebei Province, Zhaodong in Heilongjiang Province and the Taihang Mountain area in China. The positioning accuracy attained its theoretical value over the Anping and Zhaodong areas. Using GCPs whose image coordinates were obtained manually, the plan and height accuracy were found to be better than 3 m and 2 m, respectively.

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The LJ1-01 satellite is the first dedicated nighttime light remote sensing satellite in the world and offers a higher spatial resolution than the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on the Suomi National Polar-orbiting Partnership (NPP) satellites of the United States. This study compared the LJ1-01 nighttime light data with NPP/VIIRS data in the context of modeling socio-economic parameters. In the eastern and central regions of China, 10 parameters from the four aspects of gross regional product (annual average population, electricity consumption, and area of land in use) were selected to build linear regression models. The results showed that the LJ1-01 nighttime light data offered better potential for modeling socio-economic parameters than the equivalent NPP/VIIRS data; the former can be an effective tool for establishing models for socio-economic parameters. There were significant positive correlations between the two types of nighttime light data and the 10 socio-economic parameters; that for the gross regional product was the highest.

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Vertical heterostructures based on graphene have emerged as a unique architecture for novel electronic devices with unusual characteristics. Here we report a new design of vertical ambipolar barristors based on metal-graphene-silicon-graphene sandwich structure, using the bottom graphene as a gate-tunable "active contact", the top graphene as an adaptable Ohmic contact, and the low doping thin silicon layer as the switchable channel. Importantly, with finite density of states and weak screening effect of graphene, we demonstrate, for the first time, that both the carrier concentration and majority carrier type in the sandwiched silicon can be readily modulated by gate potential penetrating through graphene. It can thus enable a new type of ambipolar barristors with an ON-OFF ratio exceeding 10. Significantly, these ambipolar barristors can be flexibly configured into either p-type or n-type transistors and used to create integrated circuits with reconfigurable logic functions. This unconventional device structure and ambipolar reconfigurable characteristics can open up exciting opportunities in future electronics based on graphene or two-dimensional van der Waals heterostructures.