Analysis of rectangular laminated composite plates via FSDT meshless method

A meshless approach based on the reproducing kernel particle method is developed for the flexural, free vibration and buckling analysis of laminated composite plates. In this approach, the first-order shear deformation theory (FSDT) is employed and the displacement shape functions are constructed using the reproducing kernel approximation satisfying the consistency conditions. The essential boundary conditions are enforced by a singular kernel method. Numerical examples involving various boundary conditions are solved to demonstrate the validity of the proposed method. Comparison of results with the exact and other known solutions in the literature suggests that the meshless approach yields an effective solution method for laminated composite plates.     

Dual Material Rapid Prototyping Techniques for the Development of Biomedical Devices. Part 2: Secondary Powder Deposition

Polymeric drug delivery devices play an important role in drug administration. However, the current polymeric drug delivery device fabrication methods lack precision. This impairs the quality of the devices, resulting in a decrease in the efficiency and effectiveness of drug delivery. The concept of building parts layer by layer out of powdered raw materials makes selective laser sintering (SLS) a suitable process for fabricating polymeric matrix drug delivery devices. The current SLS process is not capable of processing two or more materials separately. This work explores the possibilities of using SLS to perform a dual material operation by developing two process models. The two processes can then be integrated to form a dual or multimaterial fabrication technique and act as a foundation for future work in multimaterial applications such as polymeric drug delivery device fabrication. Accordingly, two papers are presented. In this paper, Part 2, the emphasis is on a secondary powder deposition method, which is an electrostatic technique based on electrography. Developed toner on the photoconductor is scraped off using mechanical shearing and is deposited using an electrostatic force by electroplating. Results have shown that by reducing the distance between the photoconductor and surface of deposition, the resolution of the printout can be refined. Other important factors include the efficiency of powder removal from the photoconductor, printing speed, and the traversing speed during deposition.     

Assigning channels by link directionality in a medium access control protocol for IEEE 802.11 ad hoc networks

This study attempts to exploit the potential of link directionality to increase the achievable capacities of ad hoc networks. When an IEEE 802.11 ad hoc network achieves capacity C by using a single channel, the targeted capacity by using two channels should be 2C. However, most of the dual-channel 802.11 protocols proposed in the literature appear only to be able to achieve less than 60% of the 2C targeted capacity. The authors thus propose a link-directionality-based dual-channel medium access control protocol in an attempt to double the capacities of networks using the single-channel IEEE 802.11 protocol. The main idea is to assign channels according to link directionality to allow a link to transmit simultaneously within the carrier-sensing region of another link provided that these transmissions do not interfere with each other. Simulations show that our proposed scheme can achieve more than 85% of our targeted capacities, 0.85 X 2C = 1.7C, in large-scale random topologies. In lattice and irregular topologies, the throughput is boosted up to 2.83C and 2.13C, respectively. An approach for capacity analysis is also introduced to determine the throughput improvements that can be achieved by our proposed protocol. We believe using link directionality for channel allocations is a key step that yields significant potential for multiplying the capacity of ad hoc networks.     

Catalytic Activity of Ruthenium Nanoparticles Supported on Carbon Nanotubes for Hydrogenation of Soybean Oil

Ruthenium catalysts supported on multiwalled carbon nanotubes (MCNTs) with different loadings (1% wt, 3% wt, 5% wt) were prepared by reduction with H₂ or NaBH₄ for selective hydrogenation of soybean oil at 338 K and initial pressure of 1.066 MPa. These catalysts were characterized using transmission electron microscopy (TEM), X-ray powder diffraction (XRD), N₂ adsorption–desorption, and H₂-temperature programmed desorption (TPD) techniques. Ru particles were dispersed more homogeneously on the surface of the nanotubes after being reduced with H₂ than with NaBH₄. The catalysts with 3% and 5% Ru loadings had higher hydrogenation activity. The NaBH₄-reduced catalyst had higher cis-isomer selectivity.     

Compressive mechanical properties of carbon nanotubes encapsulating helical copper nanowires

Molecular dynamics combined with continuum mechanics is utilized to predict the compressive mechanical properties of carbon nanotubes encapsulating helical copper nanowire (NW@CNTs). The helical structures of the copper nanowires are obtained using the “simulated annealing” method. The compressive behaviors of this kind of composites are studied. The strain energy curves are shown to predict the interaction between the atoms during the compressive course. This model can be used effectively to determine the mechanical properties such as the critical buckling load P_cr and the Young’s moduli of NW@CNTs with different diameters and lengths. We also find that not all the maximum strengths of the composites are larger than the corresponding carbon nanotube bases, and they are related with the diameter, length and the carbon nanotube’s chirality. According to the comparison with the pristine carbon nanotubes (CNTs), some excellent properties of NW@CNTs are revealed.     

Further enhancements in the symmetrical components based improved fault impedance estimation method Part II. Performance evaluation

An approach that can be used for further enhancing the symmetrical components based improved fault impedance estimation method has been proposed by the authors in Part-I of this companion paper. The PC based alternative transients program (ATP) was used to model a six bus system and generate fault data. The performance of the proposed method was assessed using the generated fault data. The results of performance assessment studies are presented and discussed in this paper. The proposed method was also applied for calculating an exact fault location. It is also shown in the paper that the proposed method provides highly accurate fault location estimates based on the distance relaying information.     

Additive Manufacturing of Ceramics Enabled by Flash Pyrolysis of Polymer Precursors with Nanoscale Layers

We show that a polymer‐based route to ceramics can be implemented into additive manufacturing by reducing the time for pyrolysis to about a second, which we call flash pyrolysis. Repetitive deposition of nanometer scale coatings of the ceramic, in this way, is employed to create defect‐free infiltrations of carbon fiber composites. The mechanical strength of the fibers is retained in the composite. Excellent wetting properties of the polymer precursor permits three‐dimensional, conformal coating through the three stages of infiltration: nanoscale coating of the single fibers, filling of interstitial spaces between the fibers, and a buildup of the coating over the entire composite. The flash pyrolysis method will enable a new genre of polymer‐derived ceramics made into net shape by this unusual method of additive manufacturing.     

An efficient microfluidic sorter: implementation of double meandering micro striplines for magnetic particles switching

The ability to trap, manipulate, and separate magnetic beads has become one of the key requirements in realizing an integrated magnetic lab-on-chip biosensing system. In this article, we present the design and fabrication of an integrated magneto-fluidic device for sorting magnetic particles with a sorting efficiency of up to 95%. The actuation and manipulation of magnetic beads are realized using microfabricated square meandering current-carrying micro striplines. The current is alternated between two neighboring micro striplines to switch the magnetic beads to either one of the two outlets. We performed a series of parametric study to investigate the effect of applied current, flow rate, and switching frequency on the sorting efficiency. Experimental results reveal that the sorting efficiency is proportional to the square of current applied to the stripline, and decreases with increasing buffer flow rate and switching frequency. Such phenomena agree well with our theoretical analysis and simulation result. The fastest switching rate, which is limited by the microchannel geometry and bead velocity, is 2 Hz.