Low‐Cost Chitosan‐Derived N‐Doped Carbons Boost Electrocatalytic Activity of Multiwall Carbon Nanotubes

An effective strategy is proposed to enhance the oxygen reduction reaction (ORR) performance of multiwall carbon nanotubes (MWCNTs) in both acid and alkaline electrolytes by coating them with a layer of biomass derivative N‐doped hydrothermal carbons. The N‐doped amorphous carbon coating plays triple roles: it (i) promotes the assembly of MWCNTs into a 3D network therefore improving the mass transfer and thus increasing the catalytic activity; (ii) protects the Fe‐containing active sites, present on the surface of the MWCNTs, from H₂O₂ poisoning; (iii) creates nitrogenated active sites and hence further enhances ORR activity and robustness.     

Development of Graphene Oxide/Polyaniline Inks for High Performance Flexible Microsupercapacitors via Extrusion Printing

Extrusion printing of interdigitated electrodes for flexible microsupercapacitors (fMSCs) offers an attractive route to the fabrication of flexible devices where cost, scalability, and processability of ink formulations are critical. In this work, highly concentrated, viscous, and water‐dispersible inks are developed based on graphene oxide (GO)/polyaniline (PANi) composite for extrusion printing. The optimized GO/PANi‐based all‐solid‐state symmetric fMSCs obtained by extrusion printing interdigitated microelectrodes can deliver outstanding areal capacitance of 153.6 mF cm^?2 and volumetric capacitance of 19.2 F cm^?3 at 5 mV s^?1. It is shown that by fabricating asymmetric fMSCs using the GO/PANi as positive electrode and a graphene‐based negative electrode, the voltage window can be widened from 0.8 to 1.2 V and improvements can be achieved in energy density (from 3.36 to 4.83 mWh cm^?3), power density (from 9.82 to 25.3 W cm^?3), and cycling stability (from 75% to 100% capacitance retention over 5000 cycles) compared with the symmetric counterpart. The simple ink preparation and facile device fabrication protocols reported here make the scalable fabrication of extrusion printed fMSCs a promising technology.     

Vision-based entrance detection in outdoor scenes

Doors are a significant object for the visually impaired and robots to enter and exit buildings. Although the accuracy of door detection is reported high in indoor scenes, it has become a difficult problem in outdoor scenes in computer vision. The reason may lie in the fact that such properties of a simple ordinary door such as handles, corners, and the gap between the door and the ground may not be visible due to the great variety of doors in outdoor environments. In this paper, we present a vision-based method for detecting building entrances in outdoor images. After extracting the lines and deleting the extra ones, regions between the vertical lines are specified and the features including height, width, location, color, texture and the number of lines inside the regions are obtained. Finally, some additional knowledge such as door existence at the bottom of the image, a reasonable height and width of a door, the difference between color and texture of the doors and those of the neighboring regions, and numerous lines on doors is used to decide on door detection. The method was tested on the eTRIMS dataset, door images from the ImageNet dataset, and our own dataset including doors of houses, apartments, and stores leading to acceptable results. The obtained results show that our approach outperforms comparable state-of-the-art approaches.     

Quantitative Comparison Between Dislocation Densities in Offcut 4H-SiC Wafers Measured Using Synchrotron X-ray Topography and Molten KOH Etching

Molten KOH etching and x-ray topography have been well established as two of the major characterization techniques used for observing as well as analyzing the various crystallographic defects in both substrates and homoepitaxial layers of silicon carbide. Regarding assessment of dislocation density in commercial wafers, though the two techniques show good consistency in threading dislocation density analysis, significant discrepancy is found in the case of basal plane dislocations (BPDs). In this paper we compare measurements of BPD densities in 4-inch 4H-SiC commercial wafers assessed using both etching and topography methods. The ratio of the BPD density calculated from topographic images to that from etch pits is estimated to be larger than 1/sinθ, where θ is the offcut angle of the wafer. Based on the orientations of the defects in the wafers, a theoretical model is put forward to explain this disparity and two main sources of errors in assessing the BPD density using chemical etching are discussed.     

A novel free format Persian/Arabic handwritten zip code recognition system

In Iran like many other countries, the categorization of postal envelopes is executed manually, mostly based on the handwritten addresses and zip codes. That process is still slow and prone to man-made errors. Therefore, having an automated, accurate and efficient system to recognize handwritten zip codes is of high necessity for a faster and easier arrangement of postal envelopes, and consequently, enhanced performance of the post office.     

Type I Interferon-Mediated Regulation of Antiviral Capabilities of Neutrophils

Interferons (IFNs) are induced by viruses and are the main regulators of the host antiviral response. They balance tissue tolerance and immune resistance against viral challenges. Like all cells in the human body, neutrophils possess the receptors for IFNs and contribute to antiviral host defense. To combat viruses, neutrophils utilize various mechanisms, such as viral sensing, neutrophil extracellular trap formation, and antigen presentation. These mechanisms have also been linked to tissue damage during viral infection and inflammation. In this review, we presented evidence that a complex cross-regulatory talk between IFNs and neutrophils initiates appropriate antiviral immune responses and regulates them to minimize tissue damage. We also explored recent exciting research elucidating the interactions between IFNs, neutrophils, and severe acute respiratory syndrome-coronavirus-2, as an example of neutrophil and IFN cross-regulatory talk. Dissecting the IFN-neutrophil paradigm is needed for well-balanced antiviral therapeutics and development of novel treatments against many major epidemic or pandemic viral infections, including the ongoing pandemic of the coronavirus disease that emerged in 2019.     

A critical evaluation of literature correlations for predicting bubble size and velocity in gas–solid fluidized beds

Twenty-five different correlations for bubble size and seven different correlations for bubble rise velocity have been evaluated by comparing their predictions with data available from the open literature. The performance of these correlations has been quantified by calculating the squared difference between the correlation predictions and the experimental data in seven categories for bubble size (Geldart A, B, and D particles, low (less than 10 U_mf) and high (greater than 10 U_mf) excess gas velocity, and perforated and porous plate distributers) and three categories for bubble rise velocity (Geldart A, B, and D particles). The results indicate that the correlations of Cai et al. [Powder Technol. 80 (1994) 99–109] and Werther [Ger. Chem. Eng. 1 (1978) 166–174] are the best choices for calculating the bubble size and bubble rise velocity, respectively.     

Performance evaluation of multihop ad hoc WLANs

Ongoing technological advances in portable devices, coupled with the need for continuous connectivity while mobile, have made ad hoc networks a compelling research and development topic, particularly in a challenging multimedia multihop scenario. The ability of IEEE 802.11's ad hoc mode of operation, as a dominating wireless local area network (WLAN) protocol, to serve multihop networks requires thorough investigation. In this article, through considering crucial real-life physical phenomena and avoiding as many confining assumptions as possible, system performance measures such as delay and packet failure rate are evaluated. As a result, the importance of adequate selection of the system parameters toward performance improvement is underscored. Moreover, the simulation results imply that by complementing through priority provisions, coordination, route reservation, clustering, and optimum channel coding considerations, the IEEE 802.11 medium access control (MAC) protocol can survive in a multihop scenario. The custom simulation environment developed features modularity, comprising traffic generator, mobility, wireless channel, and IEEE 802.11 protocol modules, and is capable of accommodating many more of the physical phenomena involved.     

On the code and interleaver design of broadband OFDM systems

In this letter, we study the performance of space-frequency-coded orthogonal frequency-division modulation systems over multiple-input multiple-output frequency-selective channels. The diversity and coding advantages are derived in terms of the minimum Hamming distance and the minimum squared product distance of the code as well as the relative frequency locations (tones) where a pair of codewords with the minimum Hamming distance differ. These relationships between performance and well-defined code parameters provide new insight to code construction and interleaving design. In addition, we propose a block interleaver that yields nearly optimal coding advantage for space-frequency trellis codes.