Group theoretic particle swarm optimization for gray-level medical image enhancement.

As a principal category in the promising field of medical image processing, medical image enhancement has a powerful influence on the intermedia features and final results of the computer aided diagnosis (CAD) system by increasing the capacity to transfer the image information in the optimal form. The enhanced region of interest (ROI) would contribute to the early diagnosis and the survival rate of patients. Meanwhile, the enhancement schema can be treated as the optimization approach of image grayscale values, and metaheuristics are adopted popularly as the mainstream technologies for medical image enhancement. In this study, we propose an innovative metaheuristic algorithm named group theoretic particle swarm optimization (GT-PSO) to tackle the optimization problem of image enhancement. Based on the mathematical foundation of symmetric group theory, GT-PSO comprises particle encoding, solution landscape, neighborhood movement and swarm topology. The corresponding search paradigm takes place simultaneously under the guidance of hierarchical operations and random components, and it could optimize the hybrid fitness function of multiple measurements of medical images and improve the contrast of intensity distribution. The numerical results generated from the comparative experiments show that the proposed GT-PSO has outperformed most other methods on the real-world dataset. The implication also indicates that it would balance both global and local intensity transformations during the enhancement process.

Fabrication of Transparent and Flexible Digital Microfluidics Devices.

This study proposed a fabrication method for thin, film-based, transparent, and flexible digital microfluidic devices. A series of characterizations were also conducted with the fabricated digital microfluidic devices. For the device fabrication, the electrodes were patterned by laser ablation of 220 nm-thick indium tin oxide (ITO) layer on a 175 µm-thick polyethylene terephthalate (PET) substrate. The electrodes were insulated with a layer of 12 µm-thick polyethylene (PE) film as the dielectric layer, and finally, a surface treatment was conducted on PE film in order to enhance the hydrophobicity. The whole digital microfluidic device has a total thickness of less than 200 µm and is nearly transparent in the visible range. The droplet manipulation with the proposed digital microfluidic device was also achieved. In addition, a series of characterization studies were conducted as follows: the contact angles under different driving voltages, the leakage current density across the patterned electrodes, and the minimum driving voltage with different control algorithms and droplet volume were measured and discussed. The UV-VIS spectrum of the proposed digital microfluidic devices was also provided in order to verify the transparency of the fabricated device. Compared with conventional methods for the fabrication of digital microfluidic devices, which usually have opaque metal/carbon electrodes, the proposed transparent and flexible digital microfluidics could have significant advantages for the observation of the droplets on the digital microfluidic device, especially for colorimetric analysis using the digital microfluidic approach.

Improving the Mechanical Properties of Fly Ash-Based Geopolymer Composites with PVA Fiber and Powder.

In this work, polyvinyl alcohol (PVA) fiber and powder were added to geopolymer composites to toughen fly ash-based geopolymer, and their different toughening mechanisms were revealed. Firstly, different contents of active granulated blast furnace slag (GBFS) were added to the geopolymer to improve the reactivity of the GBFS/fly ash-based geopolymer, and the best ratio of GBFS and fly ash was determined through experiments testing the mechanical properties. Different contents of PVA powders and fibers were utilized to toughen the geopolymer composites. The effect of the addition forms and contents of PVA on the mechanical properties, freeze-thaw cycle resistance, and thermal decomposition properties of geopolymer composites were systematically studied. The results showed that the toughening effect of PVA fiber was better than that of PVA powder. The best compressive strength and flexural strength of geopolymer composites toughened by PVA fiber were 41.11 MPa and 8.43 MPa, respectively. In addition, the composition of geopolymer composites was explored through microstructure analysis, and the toughening mechanisms of different forms of PVA were explained. This study provided a new strategy for the toughening of geopolymer composites, which can promote the low-cost and efficient application of geopolymer composites in the field of building materials.

Effect of Drawing Parameters on the Properties of Polypropylene/Inorganic Particles Composites by Solid-State Die Drawing.

Die drawing is an effective method for improving the properties of polymer. In this work, polypropylene (PP)/inorganic particle composites were fabricated by a solid-state die drawing process to investigate the effects of drawing parameters, such as inorganic particles types, drawing temperature, and drawing speed, on the thermal properties, microstructure, and mechanical behavior of the drawn composites. The mechanical properties of the material were significantly improved through this processing method. For the drawn PP/inorganic particle composites with 45 wt% CaCO3, when the drawing speed was 2.0 m/min and the drawing temperature was 110 °C, the density of the drawn composites reached the lowest at 1.00 g/cm3. At this time, the tensile strength, flexural strength, and impact strength of the drawn composites were 128.32 MPa, 77.12 MPa, and 170.42 KJ/m2, respectively. This work provides a new strategy for the preparation of lightweight and high-strength PP-based composites, which have broad application prospects in the field of engineering and structural materials.

High-strength, transparent and superhydrophobic nanocellulose/nanochitin membranes fabricated via crosslinking of nanofibers and coating F-SiO2 suspensions.

In this study, nanocellulose/nanochitin membranes were prepared by suction filtrating 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized cellulose nanofiber (TOCNF)/partially deacetylated α-chitin nanofiber (α-DECHN) mixed suspensions. The result shows that, with a 1:1 ratio of nanocellulose to nanochitin, the tensile strength of the obtained composite membrane reaches 115.7 MPa and its light transmittance is 77.6 %. Heptadecafluoro-1,1,2,2-tetrahydrodecyl dimethylchlorosilane (HFTD) modified nano SiO2 (F-SiO2), was utilized to construct rough micro/nanostructures on the surfaces of the composite membranes by screen printing, forming high-strength, transparent and superhydrophobic nanocellulose/nanochitin membranes. Atomic force microscope (AFM) images reveal that nanocellulose and nanochitin, with the width between 5 nm and 20 nm and the length between 400 nm and 1.1 µm, are crosslinked with each other. The superhydrophobic nanocellulose/nanochitin composite membranes functionalized with a 2.0 wt% F-SiO2 suspension has a few clusters on its surface. The contact angle of this membrane is 150.1°, and its light transmittance is 70.4 %.

Conductive biomass-based composite wires with cross-linked anionic nanocellulose and cationic nanochitin as scaffolds.

In this study, a series of conductive composite wires were successfully prepared by combining dispersions of multi-wall carbon nanotubes (MWCNTs) and TEMPO-oxidized cellulose nanofibers (TOCNFs) with different MWCNTs contents into a dispersion of partially deacetylated α-chitin nanofibers (α-DECHNs) followed with a drying process. The TOCNFs/MWCNTs/α-DECHNs composite wires were prepared by extruding the negatively charged TOCNFs/MWCNTs dispersion into the positively charged α-DECHNs dispersion. The contact of the positively charged α-DECHNs and the negatively charged TOCNFs/MWCNTs triggers the electrostatic interaction (heterocoagulation) resulting in wire-shaped conductive composites. The SEM analysis indicates this conductive composite material has a wire-like shape with a rough but tight surface. The properties of samples were characterized by a zeta potential analyzer (Zetasizer Nano), a four-probe, an electrochemical workstation, a Fourier transform infrared spectroscopy (FTIR), an X-ray diffractometer (XRD), and a thermogravimetric analyzer (TG). Besides, the conductivity and the AC impedance of TOCNFs/MWCNTs/α-DECHNs composite wires with different MWCNTs contents were also analyzed. The conductivity of the composite wire increases from 9.98 × 10-6 S∙cm-1 to 1.56 × 10-3 S∙cm-1 as the MWCNTs content raises from 3.0 wt% to 14.0 wt%. When the MWCNTs content reaches 14.0 wt%, the prepared composite wire can light up LED at a voltage of 5 V, indicating the great potential of this biomass-based conductive composite in conductive material application.