A Novel Swimming Microrobot Based on Artificial Cilia for Biomedical Applications

Swimming microrobots can exhibit high levels of performance to move freely in the human body fluids to fulfill risky biomedical operations by mimicking microorganisms. Many researchers have proposed micro swimming methods for viscous flows based on flagellar motion. Here, a novel swimming microrobot inspired by ciliated microorganisms based on artificial cilia is introduced. The hydrodynamic model is developed and performance parameters such as propulsive force, propulsive velocity and efficiency of the microrobot are computed. The velocity and efficiency dependence on design parameters of microrobot is evaluated. The proposed micro swimming concept offers appropriate efficiency, thrust, speed and maneuverability. It is shown that the introduced swimming microrobot can reach a maximum speed 4.5 mm/s and efficiency of 40%. The proposed microrobot has the potential to be utilized in both viscous and turbulent body flows.     

Channel adaptive video stream switching for broadband wireless links

This paper exploits an H.264/Advanced Video Coding codec’s smooth stream switching to achieve robust video delivery across an IEEE 802.16 (WiMAX) broadband wireless link. As the wireless channel conditions vary over time, dynamic selection of bitrate and corresponding video quality will reduce the risk of harmful packet loss. The paper investigates choice of stream-switching with Secondary SP-frames or SI-frames relative to the selection of quantization parameter (QP) values. To control the switching points at the WiMAX server, the proposed scheme applies a feedback mechanism that monitors packet loss. As an additional suggestion, the paper considers an adaptive ARQ scheme to protect switching frames against packet loss. In summary, the broadband wireless streaming system gives more protection to higher quality video, reduces delay and packet loss, and improves received video quality. In particular, for the QP values selected, results show that increased quality primary-switching frames together with SI frames bring a significant gain in video quality compared with other switching schemes with secondary SP-frames. The other schemes in turn show an improvement to using ‘no switching’ when streaming takes place over a typical WiMAX channel with burst errors. Link delay is also reduced.     

A thermo/pH/magnetic-responsive nanogel based on sodium alginate by modifying magnetic graphene oxide: Preparation,characterization, and drug delivery

A novel thermo/pH/magnetic-triple-responsive nanogel was synthesized by grafting N-isopropylacrylamide and acrylic acid onto sodium alginate to modify magnetic graphene oxide as a drug delivery system. The synthesized nanogel was characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), vibrating sample magnetometer (VSM), atomic force micrographs (AFM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The obtained nanogel displayed excellent reversible transmittance changes in response to pH, temperature, and magnetic field. The performance of the nanogels to load doxorubicin (DOX) drug and to sustain doxorubicin release was tested upon exposure to pH, temperature, and magnetic field variations. The mechanism of drug release was proposed in this paper by different kinetic models. In addition, the effects of nanogels and DOX-loaded nanogels on MCF-7 cells were examined and results were compared with free DOX drug. The in vitro results demonstrated that this triple-responsive nanogel can be an appropriate candidate for applications in cancer therapy.     

Phase Morphology,Thermal, Thermomechanical and Interfacial Properties of PP/SAN/SBS Blend Systems

The effect of styrene–butadiene–styrene content on morphology, melting, crystallinity, dynamic mechanical properties and relaxation processes of polypropylene/poly(styrene-co-acrylonitrile)/styrene–butadiene–styrene blends was investigated. Styrene–butadiene–styrene reduced the average size of dispersed particles and generated complex aggregates in the matrix. Morphology development examined by dynamic mechanical thermal analysis showed increased damping of poly(styrene-co-acrylonitrile) domains at high styrene–butadiene–styrene contents. All blends showed reduced crystallinity and melting point compared with neat polypropylene. Poorer nucleation effect of dispersed particles at high styrene–butadiene–styrene loadings was observed. Compatibilization accelerated the form relaxation of dispersed particles. Additional relaxation process probably due to styrene–butadiene–styrene chains was observed in blends containing 10% and higher styrene–butadiene–styrene content.     

Optimal Design of a 6-DOF Parallel Manipulator Using Particle Swarm Optimization

Performance indices of parallel manipulators (PMs) vary widely with the variation of geometric properties. Improvement of one parameter often leads to worsen the other parameters. Therefore, getting into an optimum design for the PMs has been subject of much recent research. In this paper, we optimize three performance parameters of a PM simultaneously including workspace, condition number, and stiffness. In addition, a new performance index is introduced for stiffness evaluation of the PMs. The index is invariant under similarities. Because of complexity of cost function and number of variables, choosing an optimization method that can converge to the optimum point is very important. We select particle swarm optimization (PSO) method and show that this algorithm is perfect for performance optimization of PMs. Furthermore, we propose a new subroutine added to PSO algorithm to improve its convergence.     

Low-delay video control in a personal area network for augmented reality

A personal area network (PAN) is a feature of an augmented reality system, transmitting modified video for real-time display. Low-delay communication of encoded video over a Bluetooth wireless PAN is achieved in favourable channel conditions by a combination of dynamic packetisation of video slices together with centralised and predictive rate control. The result is minimised packet delay (below 0.05 s) and high-quality 40 dB video, with packet loss limited to 4 from radio frequency noise. Where channel conditions result in error bursts, dynamic rate change is introduced to reduce the need for packet retransmission and improve power efficiency.     

Photocatalytic degradation of azo dye using nano-ZrO<Subscript>2</Subscript>/UV/Persulfate: Response surface modeling and optimization

Dyes have always been considered in the context of recalcitrant organic pollutants in water. The present research has focused on the decolorization of Direct Blue 71 (DB71) using photocatalysis process of nano-ZrO₂/UV/ Persulfate. Response surface method with central composite design was applied to determine the effects of four main factors (time, ZrO₂ dosage, persulfate dosage and pH) on decolorization of DB71. The results indicated that the obtained quadratic model had a high R-squared coefficient based on the analysis of variance (ANOVA). Time had the highest effect (45.5%) on decolorization of DB71. The optimum condition predicted for complete decolorization was pH=7, 0.4 g ZrO₂, 0.75 mM persulfate and 40 min reaction time. Verification experiments confirmed that there was good agreement between the experimental and predicted responses. The studied photocatalytic process could oxidize and destruct the structure of the DB71, and average oxidation state (AOS) significantly increased from ?1.5 to +1.33, indicating the presence of more oxidized by-products and, consequently, improvement of biodegradability. The quenching tests showed that sulfate radical was the major agent in DB71 decolorization. It can be concluded that nano-ZrO₂/ UV/Persulfate is a very effective process for decolorization of colored wastewater.     

High-quality liquid phase-pulsed laser ablation graphene synthesis by flexible graphite exfoliation

This work reports a one-pot procedure of laser ablation on a graphite target in a liquid medium, based on the variation of different parameters such as target type, laser wavelength, and ablation medium,to obtain high-quality graphene nanosheets. The morphology of derived products was characterized by the field emission scanning electron microscopy(FE-SEM). Then, the morphology and structure of the optimized sample were characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD), ultraviolet-visible-near infrared(UV–vis-NIR) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy(XPS). By controlling the laser ablation parameters, we were able to prepare micrometer-sized few-layer graphene nanosheets with mainly less than ten layers. Such synthesized graphene nanosheets were grown at the surface of a flexible graphite target, indicating many potential applications in fundamental research, electrochemical and as hydrophobic surfaces.     

SrFe<Subscript>12</Subscript>O<Subscript>19</Subscript> ferrites and hard magnetic PVA nanocomposite: investigation of magnetization,coecivity and remanence

In this work, various morphologies of SrFe₁₂O₁₉ (SrFe) nanostructures were synthesized via a simple sol–gel method. The effect of concentration, temperature and various surfactants on the morphology and particle size of the magnetic seeds was investigated. The prepared magnetic products were characterized by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy techniques. Alternating gradient force magnetometry reveals that the samples exhibit hard magnetic property with the coercivity up to 5300 Oe. Strontium ferrite was added to poly vinyl alcohol to prepare the magnetic polymeric matrix thin film nanocomposites. The saturation magnetization and coercivity decreased due to agglomeration of magnetic nanoparticles in polymer matrix.