Understanding the growth behaviour of an aluminosilicate sol during ageing is necessary for the design of the sol and the synthesis of NaY zeolite. Herein, aluminosilicate sols with three different SiO 2 /Al 2 O 3 ratios were prepared and aged for varying times at 293 K. The sol was then introduced as a structuredirecting agent in the feedstock gel to generate NaY zeolite. The structure evolution of the sol species during the ageing process was studied by in situ small-angle X-ray scattering (SAXS) using synchrotron radiation. SAXS data, in combination with transmission electron microscopy images, Raman spectra and X-ray diffraction patterns, present a detailed description of the sol species, revealing an interplay between the fractal structure and reactivity to generate NaY zeolite. The SiO 2 /Al 2 O 3 ratios in the sol play a critical role in the structure evolution of the aluminosilicate species during the ageing, particularly with respect to their size distributions and the fractal dimensions. The species with suitable size and compactness in the sol are found to be an active precursor for achieving a highly crystalline NaY zeolite. The sol with an SiO 2 /Al 2 O 3 ratio of 20 possesses active species with a mass fractal dimension D m of 2.0-2.6 after ageing, which leads to the formation of a well crystallized NaY zeolite. However, the high-silica sol-25, with an SiO 2 /Al 2 O 3 ratio of 25, and alumina rich sol-10, with a ratio of 10, experience growth at either slow or fast rates. In these cases the active species have smaller D m (1.1-1.9) or larger D m (2.6-2.8), respectively, displaying low/poor activity to generate NaY zeolite. The mechanisms regulating the growth behaviour of the sols during ageing are proposed.

Here three analytical models are presented through the layout of wine-rack mechanism in three dimensions (3D) where the conditions for these models to exhibit an extraordinary property, i.e. negative compressibility are specified. In particular, we show that these three models have adjustable compressibility that can be tailored for specific applications and can exhibit NLC, NAC, zero and negative Poisson's ratios in some cases. In this way, the potential of this 2D mechanism in designing 3D models with anomalous properties can be brought out.

This paper presents an AC loss study of horizontally parallel HTS tapes. We proposed to use three parallel HTS tapes as an example. The AC losses of the middle and end tape of three parallel tapes have been measured using the electrical method and compared to those of an individual tape. The effect of the interaction between tapes on AC losses has been analysed, and compared with finite-element method (FEM) simulations using the 2D H-formulation implemented in COMSOL Multiphysics. By using FEM simulations, the cases of increasing number of parallel tapes have been considered, and the normalised ratio between the total average AC losses per tape and the AC losses of an individual single tape has been calculated for different gap distances. We proposed a new parameter, N s , a turning point for number of tapes, to divide Stage 1 and Stage 2 for the AC loss study of horizontally parallel tapes. For Stage 1, N < N s , the total average losses per tape increased with the increasing number of tapes. For Stage 2, N > N s , the total average losses per tape started to decrease with the increasing number of tapes. The analysis demonstrates that horizontally parallel HTS tapes could be potentially used into superconducting devices like HTS transformer, which could retain or even reduce the total average AC losses per tape with large number of parallel tapes.

This paper presents the measurement and simulation of Alternating Current (AC) losses on the Stabilizer-free and Copper Stabilizer High Temperature Superconducting (HTS) Tapes: SuperPower SF12100 and SCS12050. The AC loss measurement utilised electrical method to obtain overall losses with AC transport currents. The 2D H-formulation by COMSOL Multiphysics has been used to simulate the real geometry and multi-layer HTS tapes. Ferromagnetic AC losses of substrate have been assumed to be ignored as the substrates of SF12100 and SCS12050 are non-magnetic. Hysteresis AC losses in the superconducting layer, and eddy-current AC losses in copper stabilizer, silver overlayer and substrate were concerned in this investigation. The measured AC losses were compared to the AC losses from simulation, with 3 cases of different AC frequency 10, 100, and 1000 Hz. The eddy-current AC losses of copper stabilizer at frequency 1000 Hz were determined from both experiment and simulation. The estimation of AC losses with frequency at 10000 Hz was also carried out using simulation method. Finally, the frequency dependence of AC losses from Stabilizer-free Tape and Copper Stabilizer Tape were compared and analysed.

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