[en] A special design for the multi-jets electrospinning system is presented. In this work, a 6 (g/ml) % polyethylene oxide (PEO) water solution was electrified and pushed by air pressure through a spinneret. The spinnerets were built-up with needles with a regular hexagon distribution and each 3 needles have been designed as a regular triangle distribution. The outside needles modified the electrical field to uniform the electrical field strength on the inside nozzles and restrict the path of the inside jets. A coaxial iron ring was used in order to uniform the electrical field strength on the outside nozzles and restrict the collection area. In this paper, a 7 cm diameter ring was used in the 7 needles system, a 9 cm diameter ring was used in the 19 needles system and a 1lcm diameter iron ring was used in the 37 needles system test. The results demonstrated that the special design setup can produce uniform nanoscale fibres and the spinning process is insensitive with the atmosphere disturbance. The distribution of needles shows a possibility design for improving the production rate of nanofibres manufacturing.

[en] Electric-field grading by dielectric permittivity gradient devices is an effective way of enhancing the insulation performance. In situ electric-field-driven assembly is an advanced method for the fabrication of insulating devices with adaptive permittivity gradients; however, there is no theoretical guidance for its use in design. We develop an analytical model for the spatiotemporal permittivity of an uncured-composite device in an AC electric field and investigate the coupling effects between the in situ assisted electric field and rod-like filler self-assembly in three devices: a pin-flat insulator, a basin insulator, and a silicone-gel-insulated gate bipolar transistor. Our model is based on optical images and dielectric permittivity monitoring, thus avoiding complicated electrodynamic calculations. The electric-field uniformity follows a U-shaped curve with assisted-voltage application time. We also find a combination of experimental parameters that constitutes an optimal tradeoff between internal and surface electric-field uniformities. This work establishes a theoretical design framework to optimize the performance (e.g. flashover voltage and breakdown strength) of a composite device. (paper)

[en] In this paper, we review and extend recent research on averaging integrators for multiple time-scale simulation such as are needed for physical N-body problems including molecular dynamics, materials modelling and celestial mechanics. A number of methods have been proposed for direct numerical integration of multiscale problems with special structure, such as the mollified impulse method (Garcia-Archilla, Sanz-Serna and Skeel 1999 SIAM J. Sci. Comput. 20 930-63) and the reversible averaging method (Leimkuhler and Reich 2001 J. Comput. Phys. 171 95-114). Features of problems of interest, such as thermostatted coarse-grained molecular dynamics, require extension of the standard framework. At the same time, in some applications the computation of averages plays a crucial role, but the available methods have deficiencies in this regard. We demonstrate that a new approach based on the introduction of shadow variables, which mirror physical variables, has promised for broadening the usefulness of multiscale methods and enhancing accuracy of or simplifying computation of averages. The shadow variables must be computed from an auxiliary equation. While a geometric integrator in the extended space is possible, in practice we observe enhanced long-term energy behaviour only through use of a variant of the method which controls drift of the shadow variables using dissipation and sacrifices the formal geometric properties such as time-reversibility and volume preservation in the enlarged phase space, stabilizing the corresponding properties in the physical variables. The method is applied to a gravitational three-body problem as well as a partially thermostatted model problem for a dilute gas of diatomic molecules

[en] Silicone rubber composite materials have been widely used in high voltage transmission lines for anti-pollution flashover. The aging surface of silicone rubber materials decreases service properties, causing loss of the anti-pollution ability. In this paper, as an analysis method requiring no sample preparation that is able to be conducted on site and suitable for nearly all types of materials, laser-induced breakdown spectroscopy (LIBS) was used for the analysis of newly prepared and aging (out of service) silicone rubber composites. With scanning electron microscopy (SEM) and hydrophobicity test, LIBS was proven to be nearly non-destructive for silicone rubber. Under the same LIBS testing parameters, a linear relationship was observed between ablation depth and laser pulses number. With the emission spectra, all types of elements and their distribution in samples along the depth direction from the surface to the inner part were acquired and verified with EDS results. This research showed that LIBS was suitable to detect the aging layer depth and element distribution of the silicone rubber surface. (paper)

[en] Liver is one of the most important organ in the body. But there are many limitations about liver transplantation for liver failure. It is quite important to develop the xenogeneic biological liver for providing an alternation to transplantation or liver regeneration. In this paper, we proposed a method to construct a novel kind of agarose 3D-culture concave microwell array for spheroids formation of hepatic cells. Using the 3D printing method, the microwell array was fabricated with an overall size of 6.4 mm × 6.4 mm, containing 121 microwells with 400 μm width/400 μm thickness. By exploiting the Polydimethylsiloxane (PDMS) membranes as a bridge, we finally fabricated the agarose one. We co-cultured three types of liver cells with bionics design in the microwell arrays. Using the methods described above, the resulting co-formed hepatocyte spheroids maintained the high viability and stable liver-specific functions. This engineered agarose concave microwell array could be a potentially useful tool for forming the elements for biological liver support. After developing the complete system, we also would consider to scale up the application of this system. It will be not only applied to the therapy of human organ damage, but also to the development of disease models and drug screening models.