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As a promising technology of big data systems, storage and computing separated architecture has attracted increasing attention of famous companies, such as Tencent, IBM, Facebook, and Microsoft. Under this new architecture, conventional query engines like Hive and Presto choose all the original data from storage nodes and send them to computing nodes to be filtered, causing high data transmission overhead and great I/O bandwidth fluctuation. To address this problem, we design a novel data processing framework to prefilter data on storage side, and then propose a CPU-FPGA (field-programmable gate array) co-design to accelerate the queries with the purpose of reducing the communication overheads and the workloads of computing nodes. To obtain the optimal efficiency of CPU-FPGA co-processing, a workload-aware task scheduler is designed to allocate query tasks to CPU or FPGA according to the estimation of the filtering data size and processing time of query tasks. A data projection scheme is designed to support data in RCFile format which is widely used in modern systems, such as Tencent and Facebook applications. To make full use of the high parallelism of FPGA, we formulate the SQL conditions of combined predicates into Boolean parameters, and design two filtering schemes on FPGA (i.e., parallel sequential filter for fix-length data type and parallel pipeline filter for variable-length data type). Experiments on the TPC-H benchmark and Tencent data set demonstrate the efficiency of our approach, which can save up to 72.28% and 80.16% of time overheads compared with Presto and Hive, respectively. [ABSTRACT FROM AUTHOR]

In this letter, a dual-polarized 3-D frequency selective surface (3-D FSS) based on square metallic waveguides (SMWs) is proposed, which produces a flat passband with two transmission zeros in a relatively wide rejection. Because all resonances occur along propagation direction without complex resonators, a small unit cell size and simple geometry is achieved, resulting in good angular stability and easy implementation. By an equivalent circuit model, its operating principle is explained. At last, the measured results of an implemented FSS show that a stable response under the incident angles up to 60° for dual polarizations is realized. [ABSTRACT FROM AUTHOR]

A dual-band three-dimensional (3-D) frequency selective surface (FSS) is presented for dual-polarized applications in this letter. The proposed 3-D FSS is based on simple square coaxial waveguides and employs via holes, H-shaped slots, and centered gaps in a single unit cell for introducing more resonances and couplings, leading to multiple transmission zeros/poles. As a result, two passbands can be obtained, and each passband contains two transmission poles. Meanwhile, a sharp roll-off rejection of two passbands is achieved by the existence of multiple transmission zeros. The measurement results show a stable response under different incident angles up to 40° for both TE and TM polarizations, with a small unit cell size of 0.13λ0 × 0.13λ0 × 0.17λ0. [ABSTRACT FROM AUTHOR]

A reader antenna based on the segment-line oppositely directed currents is proposed in this letter for the ultrahigh frequency near-field (NF) radio frequency identification applications. The proposed antenna consists of two identical electrically large dipole elements without additional impedance matching network. To keep the surface currents along the dipole elements in-phase, the segmental and loaded method is adopted. Through the dispersion analysis, the maximum length of the dipole elements is one and a half guide wavelength with 12 segments and 0.7 pF lumped capacitors at 920 MHz. Subsequently, adjusting an appropriate distance between the dipole elements can form the oppositely directed currents, resulting in a strong, uniform, and large NF magnetic field distribution. The measured results show that the bandwidth is 53 MHz from 884.5 to 937.5 MHz covering the FCC standards. The interrogation zone is approximately equal to 480 mm × 250 mm under the observing height of 50 mm above the antenna surface. Thus, the proposed antenna is suitable to be used for the smart showcases and shelves. [ABSTRACT FROM AUTHOR]

A new dual-polarized 3-D frequency-selective surface (FSS) with quasi-elliptic bandpass response is proposed by virtue of the square coaxial waveguide (SCW). By utilizing the SCW as one propagation path in the unit cell, two resonators can be generated intrinsically without introducing any extra structures. In addition, the parallel-plate waveguide constructed by sandwiching the ABS frame between outer conductors of adjacent SCWs will provide a second propagation path and create another resonator. With the help of these resonators, a passband with two transmission poles can be obtained. Furthermore, there are two finite transmission zeros locating at both sides of the passband due to the fact that the signals passing through these two propagation paths are combined out of phase, leading to both-sided sharp roll-off skirt. The E-field analysis and equivalent circuit model presented offer a physical insight into the operating principle of the proposed 3-D FSS. For the purpose of validation, the FSS is fabricated through the 3-D printing technique. The measured results exhibit high frequency selectivity, dual polarizations, and stable bandpass response under a variation of the incidence angle. [ABSTRACT FROM PUBLISHER]