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Calcium stannate (CaSnO3) is an inorganic perovskite material with an ultrawide bandgap (4.2-4.4 eV) that is associated with its unique structural characteristics. Owing to its remarkable optical and electric properties and high physical and chemical stability, it has recently drawn significant interest for various applications such as photocatalysts for the degradation of organic compounds and hydrogen production under UV radiation, gas sensors, and thermally stable capacitors. In this study, we demonstrate a self-powered deep-UV (DUV) p-i-n photodetector consisting of CaSnO3 thin film as an efficient DUV absorber via a low-temperature solution process. The physical, optical, and electrical properties of the as-synthesized CaSnO3 are characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, space charge limited current, and four-point probe measurements. As a key component in a p-i-n DUV photodetector, the thickness of the CaSnO3 absorber layer and operating bias are optimized to enhance charge carrier transport, light absorption, and signal-to-noise ratio. As a result, the optimized device shows a high performance at zero bias under 254 nm UV illumination: with a specific detectivity of 1.56 × 1010 Jones, fast rise/fall time of 80/70 ms, and high 254:365 nm photocurrent rejection ratio of 5.5 along with a stable photoresponse during 100 continuous cycles initially as well as after 1 month of storage. Accordingly, this study suggests that a novel CaSnO3-based photodiode prepared via a solution process can be employed for many practical DUV-detection applications.

A highly electroactive Ni-based catalyst for urea oxidation is prepared by a sol-gel method with bubbling of gel mixture. It is observed that the conditions for the gel formation strongly affect the morphology and electrochemical properties of the catalyst materials. As synthesized Ni-catalysts are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The Ni-based catalyst prepared at optimum conditions in the scope of this study exhibits the urea oxidation activity of 570 mA mg-1 (at 0.54 V). In a single urea/hydrogen peroxide fuel cell test, the Ni-catalyst provides maximum power densities of 19.6 and 36.4 mW cm-2 at 30 and 70 °C, respectively. Additionally, the cell catalyst shows a stable voltage for 3 days. Thus, this work suggests that a novel Ni-based catalyst derived from a facile method can be used for urea oxidation and as an efficient anode material for urea fuel cells.

Ni-based catalysts are considered as an efficient anode material for urea fuel cells due to the low cost and high activity in alkaline media. Herein, we demonstrate that Ni-Co bimetallic hydroxide particles with highly porous nanostructures can be synthesized using mesoporous silica nanoparticles as templates. The replicated nanostructures of the Ni-Co hydroxide samples from the mesoporous silica templates are observed. The porous Ni0.8Co0.2(OH)2 particles exhibited considerably enhanced electro-catalytic activity for urea oxidation reaction by providing a high surface area and fast mass transport for urea oxidation reaction. It is also found that the Co-doping at 20% significantly reduce the overpotential and increase the peak current of urea oxidation reaction. A direct urea/H2O2 fuel cell with the porous Ni0.8Co0.2(OH)2 as anode material shows an excellent performance with maximum power densities of 11.2 and 25.6 mW cm−2 at 20 °C and 70 °C with 0.5 M urea in 5 M KOH, respectively. Thus, this work suggests that the highly porous Ni0.8Co0.2(OH)2-derived from the mesoporous silica templates can be used for urea oxidation and as an efficient anode material for urea-based fuel cells.

Calcium stannate (CaSnO

Recently, ZnO-based photodetectors have gained immense attention for ultraviolet detection applications owing to their abundance and cost-effective synthesis. However, low responsivity, slow speed, and complicated fabrication limit the applications of these detectors. Herein, we report a high-performance UV photodiode based on n-type graphene quantum dot-decorated ZnO (ZnO:GQD) and p-type poly(N,N’-bis-4-butylphenyl-N,N’-bisphenyl)benzidine (Poly-TPD) heterojunction. First, we demonstrate the incorporation of GQD in ZnO not only reduces the ZnO surface roughness and ZnO nanoparticle size but also promotes the transport of photogenerated carriers and increases the charge lifetime of ZnO. The effect of GQD content on the physical and chemical characteristics of the ZnO film is investigated using Raman spectroscopy, XRD, SEM, AFM, UV–vis spectroscopy, and PL. Second, under the appropriate GQD concentration condition, the performances of various ZnO:GQD-based devices are compared to understand the charge transport mechanism. As a result, the photodiode based on ZnO:GQD/Poly-TPD shows the most balanced energy structure, enhanced mobility, and alleviation in charge recombination relative to the other devices. The ZnO:GQD/Poly-TPD photodetector exhibits excellent performance under 365-nm UV illumination: a rise/decay time of 0.37/0.78 s and a specific d e t e c t i v i t y o f 2.1 × 10 11 Jones (at −3 V bias) with outstanding stability at least for 10 weeks without significant photocurrent degeneration.

In this paper, we introduce a hybrid fingerprint matcher which consists of two stages: local minutiae matching stage and consolidation stage. In the former stage, each minutia in the fingerprint is represented by a local feature vector which is built from the features of the neighboring minutiae within a fixed-radius circle around it. The features of each neighboring minutia are defined according to the spatial relationship with the central minutia and used for matching task. New calculation methods of the adaptive matching conditions for two neighboring minutiae and the local similarity score between two central minutiae are introduced. The latter stage performs multiple alignments based on the pairs of matching minutiae to produce the final matching score between two fingerprints. Extensive experiments over a public database used in Fingerprint Verification Competition 2002 (FVC2002) prove a considerable improvement in accuracy of our proposed algorithm against some well-known techniques and Top 5 participants of FVC2002.

This paper proposes a two-step synchronization algorithm for UWB receivers in accordance with IEEE 802.15.4a standard. A low data rate, low complexity receiver is developed using a typical energy detection UWB non-coherent analog front-end, which consists of a square-law device and an integrate-and-dump ADC with sub-Nyquist sampling rates. A coarse synchronization algorithm, often neglected in literature, is introduced by continuously correlating received samples' segments with a self-generated template until a simple threshold condition is satisfied. A proposed fine synchronization algorithm exploits the low sampling rates of the system and does not need to measure noise power, which helps reduce the receiver complexity (and power consumption). Finally, we assess, by simulation, the impact of different sampling rates and the synchronization lengths on bit-error-rate (BER) performance of the system.

This paper proposes a practical synchronization algorithm for Transmit-Reference UWB receiver which uses sliding window and supports flexible sampling rates. Additionally, a Simulink model and implementation of synchronization algorithm in receiver by hardware description language (HDL) is also developed using model-based design. Finally, we assess impact of signal-noise-rate (SNR), number of bits quantization and sampling rate on bit-error-rate (BER).