The 0.72Bi(Fe1−xAlx)O3–0.28BaTiO3 (x = 0, 0.01, 0.03, 0.05, and 0.07, abbreviated as BFAx–BT) lead‐free high‐temperature ceramics were prepared by the conventional ceramic processing. Systematic investigation on the microstructures, crystalline structures, dielectric and piezoelectric properties, and high‐temperature stability of piezoelectric properties was carried out. The crystalline structures of BFAx–BT ceramics evolve from rhombohedral structure with x < 0.01 to the coexistence of rhombohedral structure and pseudocubic phases with x ≈ 0.01, finally to pseudocubic phases when x > 0.03. Remarkably high‐temperature stability with near‐zero temperature coefficient of piezoelectric properties (TCkp), together with improved piezoelectric properties has been achieved for x = 0.01 BFAx–BT ceramics. The BFAx–BT(x = 0.01) ceramics simultaneously show the excellent piezoelectric properties of d33 = 151 pC/N, kp = 0.31 and super‐high‐temperature stability of Td = 420°C, TCkp = 1 × 10−4. It is considered that the observed strong piezoelectricity and remarkably high‐temperature stability should be ascribed to the phase coexistence of rhombohedral and pseudocubic phases. The rhombohedral phases have a positive TCkp value and the pseudocubic phases possess a negative TCkp value. Thus, the TCkp value of BFAx–BT ceramics can be tuned by composition of x.

1D fibers of Bombyx mori silk fibroin (SF) and poly(L-lactide) (SF-s-PLLA) with side-by-side parallel arrangement of the two components in a single fiber made by electrospinning are presented. The side-by-side arrangement in both randomly oriented and aligned two-in-one fibers was confirmed by scanning electron and confocal laser scanning microscope studies. The molecular orientation and secondary structure of SF and PLLA were dependent on the fiber alignment and annealing conditions. The two sides retained their individual secondary structure before and after annealing without affecting each other in a significant way. The two-in-one fibers after post treatment with methanol and heat at 80 8C showed tensile strength 16.5 AE 1.4 MPa, modulus 205 AE 20.6 MPa, and an elongation at break of 53 AE 8%.

Commutation failure, which is a very frequent dynamic event in HVDC inverters, can deteriorate the availability of HVDC links and thus affect the performance of the power system. Most commutation failures are caused by voltage reduction due to ac system faults. In this paper, efforts are made to lower the effect of commutation failure on the power system, and the remedy is implemented in a fuzzy controller. In order to achieve control flexibility, the output of the fuzzy controller is made appropriate by setting a self-adjusting proportional factor. The validity and effectiveness of the fuzzy controller is verified by simulation which shows that the fuzzy controller can decrease commutation failure frequency induced by ac system faults.

and morphologies, are highly promising materials for water collection, smart textiles for moisture management, dual drug release, actuation, etc.Electrospinning is a versatile method for the production of thin fibers with a high surface-to-volume-ratio from a multitude of materials in a simple and straightforward way. [4] Various fiber morphologies have been realized by either controlling the spinning parameters or by using special spinning nozzles, e.g., homogenous fibers, particles, or particles immobilized on fibers (also called beaded fibers) as well as fibers with bead-on-string or pearl-necklace morphology. [5] Beaded fibers, in which beads of different shapes (i.e., spherical, spindle shape) and the joints (fiber segment between the two beads) are made up of the same polymer, already gained an edge over conventional nanofibers in providing superhydrophobicity as well as encapsulation and release of microparticle drugs from the beads. [6] Complex fiber morphologies with precisely defined composition and properties are accessible employing special spinning nozzles, which combine two or more components in either s-b-s or core-shell (c-s) fashion. [7] This method also allows to combine bioinspired structures with appropriate material properties to achieve complex functional materials with unique properties. For example, wool-like crimps were generated by spinning polymers with different mechanical properties in an s-b-s fashion, both by melt and solution electrospinning. [7b,8] Bicomponent fibers with core-shell-type beads (coaxial beadon-string morphology) are another example. The formation of these fibers is not trivial and can be realized by using a polymer solution, which contains swollen crosslinked polymeric colloids. Applying a simple spinning nozzle produced beaded fibers, in which a row of colloidal particles is embedded in the matrix polymer. [9] Alternatively, bicomponent fibers with coaxial bead-on-string structure can be obtained by combining electrospraying with electrospinning in a coaxial electrospinning setup. [10] Similar fibers have also been produced employing a coating method. [11] In this approach, a polymer solution is coated onto a supporting fiber, which further on breaks up into droplets driven by Rayleigh instability. Fibers with coaxial beadon-string morphology are very promising materials for water harvesting applications, which demands for the development of efficient large-scale production methods. [12] Bioinspired Electrospun Bicomponent Fibers Nature is an intriguing inspiration for designing a myriad of functional materials. However, artificial mimicking of bioinspired structures usually requires different specialized procedures and setups. In this study, a new upscalable concept is presented that allows to produce two bioinspired, bicomponent fiber morphologies (side-by-side and coaxial bead-on-string) using the same electrospinning setup, just by changing the employed spinning solvent. The generated fiber morphologies are highly attractive for thermoresponsive actuat...

A tubular highly porous scaffold of polylactide (PLA) and poly-ε-caprolactone (PCL) is fabricated by self-rolling of a 2D fibrous bilayer of PLA and PCL in water without use of any classical thermo-/pH-responsive polymers. The self-rolling and diameter of the tube are dependent upon the bilayer thickness and temperature. A 75 µm thick 2D bilayer (PLA = 25 µm; PCL = 50 µm) rolls to a hollow tube of diameter around 0.41 mm with multilayered wall at 40 °C within 5 min. The tubes keep their form and size in water at all temperatures once they are formed. The interesting properties of the hollow tubes, that is, permeation of gases through the walls and flow of water without leakage under tested conditions in combination with good mechanical stability, use of only biodegradable polymers, and easy and reproducible fabrication method, allow them to be promising candidates for future studies as scaffolds for tissue engineering.