In this paper, we propose a bottom-up visual saliency detection algorithm. Different from most previous methods that mainly concentrate on image object, we take both background and foreground into ...consideration. First, we collect background seeds from image border superpixels by boundary information and calculate a background-based saliency map. Second, we select foreground seeds by segmenting the first-stage saliency map via adaptive threshold and compute a foreground-based saliency map. Third, the two saliency maps are integrated by the proposed unified function. Finally, we refine the integrated result to obtain a more smooth and accurate saliency map. Moreover, the unified formula also proves to be effective in combining the proposed approach with other models. Experiments on publicly available data sets demonstrate that the proposed algorithm performs favorably against the state-of-the-art methods.
A novel dual-band frequency-reconfigurable stacked patch antenna is presented. The antenna comprises two stacked square patches. Each patch is divided into two rectangular portions by a gap, and a ...pair of varactor diodes is introduced to bridge the gap. By changing the reverse bias voltages across the two pairs of varactor diodes, the antenna can operate at dual frequency bands with independent frequency tuning. A fully functional prototype is fabricated and characterized. It exhibits a continuously dual frequency-tunable characteristic, from 1.68 to 1.93 GHz for the low band and from 2.11 to 2.51 GHz for the high band. Well-controlled unidirectional radiation patterns are achieved at all operating frequencies. To the best knowledge of the authors, this is the first dual-band reconfigurable patch antenna with an independent frequency tuning ability. The dual-band frequency selective feature makes the antenna potentially suitable for future wireless communication systems, such as cognitive radio.
A novel microstrip dual-band filtering power divider (FPD) is presented in this letter. By introducing a proper coupling topology between the quarter-wavelength (λ/4) shortended microstrip line and ...two multi-mode resonators, the dualband FPD is constructed. Meanwhile, good isolation of this FPD is attained by installing an isolation resistor between the resonators. Additionally, two 3λ/4 open-ended stubs are attached in the output coupled lines to improve its frequency selectivity and obtain a wide upper stopband. For validation, a prototype FPD operating at 1.57 and 2.89 GHz is designed, fabricated and measured. Both the simulated and measured results are in good agreement. Results indicate that the proposed FPD exhibits not only a sharp frequency selectivity and good harmonic suppression with the help of the six inherent transmission zeros, but also better than 21 dB isolation within the entire dual operation bands.
A comprehensive study on the mechanism of bandwidth enhancement for an equilateral triangular microstrip patch antenna (MPA) under differential excitation is presented in this paper. Attributing to ...the way of differential excitation, the radiation directivity of TM 11 mode in such a patch has been improved a lot, and field distributions for both TM 10 and TM 11 modes are found to be simultaneously excited for radiation. Next, two shorting posts are introduced to this MPA so as to generate an additional mode, i.e., zero mode, which resonates in a frequency between TM 10 and TM 11 modes. With the proper arrangement of these three modes in proximity to each other, a wide bandwidth for radiation can be satisfactorily achieved. To demonstrate the validity of the proposed concept, a prototype antenna is finally designed and fabricated. As theoretically expected, the impedance bandwidth of the final designed patch antenna has been increased to 50.46% and the gain is around 6.5 dBi. Both simulated and measured results exhibit wide bandwidth and good performance of radiation.
A novel cavity-backed slot antenna, with the ability of reconfiguring the frequency, polarization, and radiation pattern, is presented. The reconfigurability is realized by electronically controlling ...the state of switches between two crossed slots etched on the surfaces of a substrate integrated waveguide cavity. The antenna is capable of simultaneously changing the radiation patterns between forward and backward directions, switching the polarization among two orthogonal linearly polarized (LP) and two orthogonal circularly polarized (CP) states, tuning between three frequency bands for LP states and between two frequency bands for CP states. A fully functional prototype is developed and tested, demonstrating the antenna with measured gains of approximately 4 dBi and stable unidirectional radiation patterns for all 20 states. In addition, the proposed design possesses a low profile of 0.01 free-space wavelength.
A microstrip filtering power divider (FPD) with good isolation performance and harmonic suppression is presented. By replacing a simple resistor with a novel distributed stepped-impedance resonator ...network, better isolation and wider stopband are simultaneously attained. A transmission matrix-based analysis method is then extensively described to determine the circuit geometrical parameters at the synthesis level by facilitating the incorporation of design indexes and structure dimension. A prototype FPD is designed, fabricated and measured. The proposed FPD exhibits a center frequency of 2.2 GHz (f 0 ) with the isolation better than 17dB within the entire passband and a stopband extended to 12 GHz (5.45f 0 ).
A novel microstrip dual-mode filtering power divider (FPD) is presented in this letter. Stemming from the distinctive voltage distribution along an open-ended one-wavelength (λ) microstrip line, the ...dual-mode FPD is initially constructed by utilizing proper coupling topologies between the open-ended transmission line and two dual-mode resonators. Meanwhile, its good isolation performance is attained by introducing an isolation resistor between the two dual-mode resonators. Next, the explicit synthesis method is described to design the proposed FPD with prescribed performance. A prototype FPD at 2.4 GHz is in final implemented and measured. As theoretically expected, this proposed FPD exhibits better than 22-dB isolation within the entire operation band along with 17-dB harmonic suppression up to 7.5 GHz (3.1f 0 ).
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CoAl-layered double hydroxide nanosheets/reduced graphene oxide composite (CAN-LDH-NS/rGO) was fabricated by an exfoliation-restacking process, during which, the nitrate-intercalated ...CoAl-layered double hydroxide nanosheets (CAN-LDH-NS) were restacking on the surface of the reduced graphene oxide (rGO) flakes by means of electrostatic interactions. Electrochemical performances of the composite were enhanced due to the incorporation of CAN-LDH-NS and rGO flakes. The specific capacitance of the composite was found to be about 1296Fg−1 at a current density of 1Ag−1. Furthermore, the capacitance of the composite maintained 90.5% of the initial capacitance even at a high current density of 15Ag−1 after 1000 cycles. These results indicate that the CAN-LDH-NS/rGO composite is a promising material for supercapacitors. Our presented work not only provides a facile preparation approach to LDH/rGO hybrid materials, but also sheds a new light on electrode design for supercapacitors.
Abstract
A new design of single‐layered balanced filtering crossover with high selectivity based on square patch resonator is proposed. Originated from the degenerate modes, that is, TM
12
and TM
21
...on square patch resonators, the feasibility of intrinsic common‐mode (CM) suppression and channel isolation is conceived. For demonstration, a first‐order balanced crossover prototype is designed. Afterwards, to enhance selectivity, a square patch resonator is subtly divided into two identical parts and then introduced into the prototype. Hence, a balanced filtering crossover with a fifth‐order Chebyshev response is formed. Furthermore, stubs are deployed between adjacent patch resonators to introduce mixed couplings. Thus, two controllable transmission zeros are obtained, and better out‐of‐band suppression is achieved. Ultimately, the proposed crossover is fabricated and measured. High performance in terms of differential‐mode filtering response, in‐band CM suppression and channel isolation demonstrates the feasibility of the proposed method.
A comprehensive study of a new planar-type balun prototype is presented in this paper for application in the design of balun bandpass filters (BPFs) with widely used open-type resonators. The ...proposed balun is in general composed of two identical back-to-back quarter-wavelength (λ/4) coupled line sections. The design concept originates from the analysis of the standing wave pattern on a half-wavelength (λ/2) open-circuited transmission line. After an intuitive illustration is given, its working principle is presented to validate the feasibility of the proposed balun. Afterward, two types of the coupled line prototypes are analyzed to implement the proposed balun with filtering response, whereas a basic rule is given to realize the transmission zeros. To further demonstrate the validity of the proposed balun prototype, two practical balun BPFs with common dual-mode resonators are designed and fabricated. As expected, transmission zeros are generated near the desired passband of our presented balun filters, thereby improving their frequency selectivity. Both simulated and measured results exhibit good filtering and balun performance.
