Enhanced ductility and tensile properties of hybrid montmorillonite/cellulose nanowhiskers reinforced polylactic acid nanocomposites

Montmorillonite (MMT)/cellulose nanowhiskers (CNW) reinforced polylactic acid (PLA) hybrid nanocomposites were prepared by solution casting. CNW were isolated from microcrystalline cellulose using a chemical swelling method. An initial study showed that the optimum MMT content, for mechanical properties, in a PLA/MMT nanocomposite is five parts per hundred parts of polymer (phr). Various amounts of CNW were added to the optimum formulation of PLA/MMT to produce PLA/MMT/CNW hybrid nanocomposites. FT-IR analysis indicated the formation of some polar interactions, resulting in enhanced tensile properties of the hybrid nanocomposites. The highest tensile strength for the hybrid nanocomposites was obtained for a 1 phr CNW content. Young’s modulus was also found to increase with an increasing CNW content. Interestingly, the strain to failure (or ductility) of the hybrid nanocomposites increased significantly from ~10 to ~90 % with the addition of 1 phr CNW. This increase in ductility was proposed to be due to the nucleation of crazes and the formation of shear bands in the PLA.     

Dual‐band aperture‐coupled rectenna for radio frequency energy harvesting

The article presents a dual‐band aperture‐coupled rectenna for radio frequency (RF) energy harvesting at 2.45 and 5 GHz application. The rectenna consists of a dual‐band π‐shaped slot‐etched aperture‐coupled antenna, designed at the lower substrate of two FR4 substrate layers and a dual‐band rectifier. The proposed antenna design also introduces the harmonic suppression of third‐ and higher order harmonics, ranging from 6 up to 10 GHz from the asymmetrical stubs design at the transmission feedline. The dual‐band rectifier is designed to operate at 2.45 and 5 GHz frequency, successfully achieving high conversion efficiency at 68.83% and 49.90% with the optimum load resistor of value 700 Ω and 1.1 kΩ. The minimum DC voltage of 0.167 and 0.236 V with 0 dBm RF input power can be increased when greater RF power is being applied to it, increasing its flexibility to cater various low‐power applications.     

Microfluidic biochemical sensor based on circular SIW‐DMS approach for dielectric characterization application

This work proposes an advancement of microwave planar resonator sensor with high sensitivity for microfluidic dielectric characterization. The physical design was employed based on circular substrate integrated waveguide (CSIW) with an integration of defected microstrip structure (DMS). This approach can be applied to accelerate the dielectric detection, structure miniaturization and material differentiation. The presented sensor operates based on variations in the dielectric properties of solvents in the vicinity of a planar open‐ended microstrip resonator device. Further analysis in volume and concentration were performed to validate the reliability of the sensor. Validation and functionality of the sensor were investigated by experimental and results comparison. A mathematical model was developed to determine the dielectric constant and the loss tangent of the microfluidic samples. The average error detection has a lower percentage value of 0.11% by comparison to the commercial and ideal dielectric properties of the aqueous samples. The maximum relative error detection, ±0.37% implied better accuracy compared to the existing resonator sensors with more than 400 of the Q‐factor. The proposed CSIW‐DMS sensor was found to give higher accuracy and detection response; besides easier to fabricate, and compatible for integration with other electronic components in an RF sensor for variety of applications.     

Agarose coated micro-bottle sensor for relative humidity detection

The whispering gallery mode (WGM) based micro-bottle resonator (MBR) sensor has been proposed and demonstrated for relative humidity measurement by using an agarose gel as a transducer. MBR was fabricated by using a soften-and-compress method to form a 190 μm bulge bottle. The micro-bottle was optically excited by a 3 μm tapered fiber and it exhibits a resonance with a Q factor in an order of 105. The agarose coated MBR produces a good sensing response towards humidity with the sensitivity of 0.107 dB/%RH and linearity of 99.614%. The agarose hydrophilic nature and its changing porosity and refractive index with increasing relative humidity made the coated MBR structure to be more sensitive than the uncoated structure. This humidity sensor has a simple fabrication and is showing good sensitivity, linearity, resolution, response time and operational in a wide humidity range.     

A survey of mmWave user association mechanisms and spectrum sharing approaches: an overview,open issues and challenges,future research trends

Fifth generation (5G) cellular networks promise to support multi-radio access technologies (multi-RATs) with low and high frequencies aiming at delivering good coverage, several gigabits data rate, and ultra-reliable services. In this context, user-association and resource allocation appear to be a huge challenge due to the variety of specifications and varied propagation environments. In this treatise, the focus is on the technical and administrative difficulties of the adoption of user association (UA) mechanism and spectrum sharing approach (SSA) in millimeter wave (mmWave) systems, for example, the technical design considerations and their underlying options, as well as their impact on users and network performance. In addition, details on the importance of the rules and regulations of SSA are presented. This study also identified a few possible design solutions and potential promising technologies in both UA and SSA. In the context of UA, several mechanisms are identified, such as backhaul-, caching-, and hybrid multi-criteria-aware UA to achieve seamless connectivity and to enhance the network utility. In the context of SSA, this study pinpoints varied subjects that need to be explored, such as joint efficient rules and regulations enactment, assessment of fairness and independence in multi-independent mobile network operators (multi-IMNOs) that support SSA, as well as the implementation of hybrid-SSA via Virtualized Cloud Radio Access Network. Finally, attention is drawn to several key conclusions to enable readers and interested researchers to learn about the most controversial points of mmWave 5G cellular networks.

     

A Spider‐Capture‐Silk‐Like Fiber with Extremely High‐Volume Directional Water Collection

A spider web collects water by its capture silk for recovering the daytime‐distorted shape during night through water‐sensitive shape memory effect. This unique smart function and geometrical structure of spider‐capture‐silk inspires the development of artificial fibers with periodic knots for directional water collection with vast potential applications in water scarce regions. Existing such fibers are mainly based on nylon filaments coated with petroleum‐originated synthetic polymer solutions. Distinct from using synthetic materials, an all silk‐protein fiber (ASPF) with periodic knots endows extremely high volume‐to‐mass water collection capability. This fiber has a main body consisting of B. mori degummed silk coated with recombinant engineered major ampullate spidroin 2 of spider dragline silk. It is 252 times lighter than synthetic polymer coated nylon fibers that once was reported to have the highest water collection performance. The ASPF collects a maximum water volume of 6.6 µL and has a 100 times higher water collection efficiency compared to existing best water collection artificial fibers in terms of volume‐to‐mass index at the shortest length (0.8 mm) of three‐phase contact line. Since silkworm silks are available abundantly, effective use of recombinant spidroins tandemly shows great potential for scalability.     

Transfer learning from synthetic labels for histopathological images classification

This study introduces a new strategy that combines unsupervised learning (clustering) and transfer learning. Clustering methods are employed to generate synthetic labels for the source dataset (ICAR-2018). The generated dataset is then used for transfer learning to other histopathological datasets (KimiaPath960, CRC, Biomaging??2015, Breakhis, and Lymphoma). The comparative study based on two clustering algorithms (K-means and multi-objective clustering stream) demonstrates the efficiency of MOC-Stream. The generated synthetic histopathological dataset by this clustering algorithm outperformed the original labeled dataset and the imageNet models in transfer learning.

     

Circular discontinuities detection in welded joints using Circular Hough Transform

Conventional radiography is one of the common non-destructive testing which employs manual image interpretation. The interpretation is very subjective and depends much on the inspector experience and working conditions. It is therefore useful to have pattern recognition system in order to assist human interpreter in evaluating the quality of the radiographed sample, especially radiographic image of welded joint. This paper describes a system to detect circular discontinuities that are present in the joints. The system utilizes together two different algorithms, which are separability filter to identify the best object candidate and Circular Hough Transform to detect the presence of circular shape. The result of the experiment shows a promising output in recognition of circular discontinuities in a radiographic image. This is based on 81.82–100% of radiography film with successful circular detection by using template movement of 10 pixels.