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We propose a scheme to generate stable vector spatiotemporal solitons through a Rydberg electromagnetically induced transparency (Rydberg-EIT) system. Three-dimensional vector monopole and vortex solitons have been found under three nonlocal degrees. The numerical calculation and analytical solutions indicate that these solitons are generated with low energy and can stably propagate along the axes. The behavior of vector spatiotemporal solitons can be manipulated by the local and nonlocal nonlinearities. The results show a memory feature as these solitons can be stored and retrieved effectively by tuning the control field.

This paper mainly studies the effect of Diatomite Content on the thermal insulation performance of straw fiber cement-based composites. The test shows that 30% sulphoaluminate cement is replaced by ordinary Portland cement. XRD test showed that the diffraction peaks of Ca (OH)2 and Ettringite were stronger than those of ordinary Portland cement, and the crystallization effect was better. The compressive strength and flexural strength increased by 7.6% and 20% respectively. With the increase of diatomite content, the dry density and thermal conductivity of the composite decreased. When diatomite content was 25% of the total cementitious material, the dry density of the composite was 1068.37 kg/m3, and the thermal conductivity could reach 0.1163 W/(m.K). The thermal insulation performance of the composite could be significantly improved by adding diatomite.

In this paper, NaOH solution was used to treat straw fiber modified alkali slag cement, which enhanced the interfacial bonding between straw fiber and cementitious materials. The results showed that the best modification effect of straw fibers was obtained by soaking 3% NaOH solution for 16 hours. The compressive strength and flexural strength of alkali slag cement specimens cured for 28 days are 81.5 MPa and 10.9 MPa respectively. The toughness of the composites increases with the increase of fiber content. The flexural strength of straw fiber composites treated with NaOH solution and without NaOH solution increased by 5.6% and 11.3% compared with those without NaOH solution, and the compressive strength of straw fiber composites treated with NaOH solution increased by 34.08% compared with those without NaOH solution when the content of straw fiber was 10%.

The raw materials of straw fibers were treated by different methods of nitrogen filling and carbonization at different temperatures. The cementitious materials consisted of ordinary Portland cement with strength grade 52.5 and sulphoaluminate cement with a ratio of 3:7. The surface morphology and material analysis of the fibers were carried out by means of SEM and EDS. The SiO2 content in the surface layer of carbonized straw fibers was 86.69% higher than that of common straw fibers, and the interfacial bonding of the composites was more compact because of the hydration reaction. The initial setting time of composites with carbonized straw fibers is shorter than that of ordinary straw fibers, the flexural strength is slightly reduced by 6.3%, and the compressive strength is significantly increased by 21.93%.

Single domain Y–Ba–Cu–O (YBCO) samples composed of a YBa2Cu3O7−δ (Y-123) matrix with Y2BaCuO5 (Y-211) inclusions were fabricated using the top-seed melt-textured growth (TSMTG) process. The influence of the Y-211 inclusions on the melt-textured growth mode has been studied for precursor pellets with a Y-123:Y-211 molar ratio of 1:0.2, 1:0.3 and 1:0.4. The surface morphologies obtained from these sintering pellets quenched from 1000 °C, 997 °C and 994 °C, respectively, have revealed that the initial peritectic recombination process near the seed crystal seems to take place earlier for the Y-123 matrix with low Y-211 inclusions than for that with a high level of Y-211 inclusions; however, the melt-textured growth rate of the single domain seems to be faster in the system with a high level of Y-211 inclusion than in that with a low level.

The different behaviors of the surface plasmons along the in-plane surface of silver sheet and along the side wall of bare aperture inside the same sheet are analyzed, and their respect roles to the final field enhancement are discussed as well. The short pitch surface plasmons resonance along the side wall of the aperture is regarded as the origin of the thickness dependence of the field enhancement at the exit side of the aperture. Several solutions such as corrugation incident plane, protrusion design at the exit side to realize maximized field enhancement at the exit side of aperture are proposed. Furthermore, the step and non-step nano-sized silver apertures surrounded with circular surface corrugation structures were compared in detail. It was proved that if the 40 nm sized step aperture with circular grating the near-field intensity can reach up to around 1000 times enhancement factor at the immediate exit and around 400 times enhancement even if at the plane of 10 nm away from exit of aperture.

Experiments reveal that there is a non-ohmic dissipation behaviour in the Ca-doped polycrystalline Y1−xCaxBa2Cu3O7−δ even at temperature T = 20 K. This non-ohmic dissipation seems to come from the vortex excitation along the grain boundaries and appears in anomalous I–V characteristics with a non-power-law behaviour at temperatures below 60 K, and then with a power-law behaviour as the temperature approaches Tc. This abnormal behaviour cannot be explained by the thermal flux creep model. We suppose that a giant flux motion along the grain boundaries might be responsible for this anomalous non-ohmic dissipation behaviour. A modified I–V relation was worked out based on Larkin's collective pinning model, and the analytical I–V curves were found to be coincident with the experimental curves quite well. This confirmed that the vortex excitation process along the grain boundaries in Ca-doped polycrystalline Y1−xCaxBa2Cu3O7−δ might be described with a modified collective pinning model.

A model 9 kVA (240 V/9.6 V) single-phase HTS transformer has been developed and tested with and without a cold iron core at 77 K. The primary and secondary windings were wound by transposed conductors, which are made from stainless steel-reinforced multifilamentary Bi2223/Ag tapes. The structures of the primary and secondary windings are helical and double-pancake, respectively. Primarily characteristics of the transformer are obtained through no-load tests, and short circuit tests. The iron cores are made of the common laminated Fe–Si steel plates and operate at nitrogen temperature 77 K. Based on the results of this transformer, we will develop a 630 kVA HTS transformer with the same rating currents in the near future.

High quality superconducting YBa2Cu3O7-delta (YBCO) thin films have been successfully deposited on silicon-on-insulator (SOI) substrates buffered by an yttria-stabilized zirconia (YSZ) layer using the in situ pulsed laser deposition (PLD) method. X-ray diffraction (XRD) theta-2theta-scan and phi-scan, and reflection high energy electron diffraction (RHEED), indicate that both the YSZ and YBCO thin films are of high crystallinity and good lattice orientation. Atomic force microscopy (AFM) shows that the root mean square roughness R-q of YSZ thin films is less than 0.9 nm in an area of I mum x I mum, and that of YBCO thin films is about 3 nm in an area of 2 /tm x 2 mum. The zero-resistance temperature T-C0 of the YBCO/YSZ/SOI multilayers is up to 88 K, measured by a four-probe method. However, scanning electron microscopy (SEM) demonstrates many clear cracks in YBCO thin films due to the lattice constant and thermal expansion coefficient mismatch between SOI and YBCO. The crack width changes with the thickness of YBCO thin films.

There is great variation in the critical current of HTS tapes with the direction of applied magnetic field with respect to the tape surface. Based on detailed experiments, a simple analytical empirical relation of critical current density is obtained. If the magnetic field dependence of critical current density in two orientations, i.e. field parallel and perpendicular to the tape surface, is known, we can calculate the magnetic field dependence of the critical current density at any orientation. The calculated results are in good agreement with the experimental data. This is very useful for the application of HTS magnets from a practical point of view.

The modified top-seeded melt-textured growth technique for fabricating single grain Y–Ba–Cu–O (YBCO) bulk superconductors with high field-trapping ability by using modified precursor pellets was reported. The modified precursor pellets are composed of different precursor powders YBa2Cu3O (Y123) + x mol% Y2BaCuO5 (Y211) + 1 wt% CeO2 without any further chemical doping. The modified YBCO bulks up to 25 and 34 mm in diameter were successfully fabricated from the modified precursor pellets. Microstructural observation results showed that the modified YBCO bulk exhibited a homogeneous distribution of Y211 phase particles, which was qualitatively explained by the solute diffusion growth model in combination with the trapping/pushing theory. As a result, it is notable that the peak trapped field values of 0.91 T (maximum 0.96 T) and 1.2 T (maximum 1.28 T) at 77 K were achieved for 25 and 34 mm modified YBCO bulks, respectively. In a word, the results from present work are very helpful to understand the melt growth mechanism and to further improve the properties of YBCO bulk superconductors for practical applications.

A fully superconducting magnetic suspension structure has been designed and constructed for the purpose of superconducting bearing applications in flywheel energy storage systems. A thrust type bearing and two journal type bearings, those that are composed of melt textured high-Tc superconductor YBCO bulks and Nd-Fe-B permanent magnets, are used in the bearing system. The rotor dynamical behaviors, including critical speeds and rotational loss, are studied. Driven by a variable-frequency three-phase induction motor, the rotor shaft attached with a 25 kg flywheel disc can be speeded up to 15 000 rpm without serious resonance occurring. Although the flywheel system runs stably in the supercritical speeds region, very obvious rotational loss is unavoidable. The loss mechanism has been discussed in terms of eddy current loss and hysteresis loss.

It is well known that a fine and homogeneous distribution of Y2BaCuO5 (Y211) phase particles in single-grain Y-Ba-Cu-O (YBCO) bulk superconductors is essential for improving field-trapping ability. However, the size and concentration of Y211 phase particles in the fully melt-processed superconducting bulk increase significantly with the distance from the seed, which results in the accumulation of Y211 phase particles and the degradation of superconducting properties. In this paper, we report a new method of fabricating single-grain YBCO using layered precursor pellets. Using the top-seeded melt-textured growth process, single-grain YBCO bulk superconductors of about 22 mm in diameter and 9 mm in thickness were fabricated from layered precursor pellets and standard precursor pellets, respectively. The layered precursor pellets consist of precursor powders with 40 mol% Y211 at the top, 30 mol% Y211 in the middle and 20 mol% Y211 at the bottom of the whole pellets, while standard precursor pellets are prepared from precursor powders with only 40 mol% Y211. The growth morphology, microstructure and magnetic flux properties of the layered samples and standard samples were comparatively studied. The results proved that the layered precursor pellets allow a sufficient growth in the c-growth sector and a more uniform distribution of the Y211 phase in the matrix. The distribution of Y211 phase particles is qualitatively explained by the prevalent trapping/pushing theory. The trapped field at 77 K reaches 0.8 T, nearly 29% higher than the standard sample. The present results are very valuable for further improving the properties of YBCO bulk superconductors.

Comprehensive first-principles calculations are performed to provide insight into the intriguing physical properties of the ternary cubic fluoride KCrF3. The electronic structures exhibit a prominent dependence on the effective local Coulomb interaction parameter Ueff. The ground state of the cubic phase is a ferromagnetic (FM) half-metal with Ueff equal to 0, 2, and 4 eV, whereas the insulating A-type antiferromagnetic (A-AFM) state with concomitant homogeneous orbital ordering is more robust than the FM state for Ueff exceeding 4 eV. We propose that the origin of the orbital ordering is purely electronic when the cooperative Jahn—Teller distortions are absent in cubic KCrF3.

LReBaCuO (LRe=Nd, Sm, Gd) single domains possess a superior superconducting performance and have exhibited potential applications in the fields of superconducting bearings and permanent magnets. Therefore, the requirement of a large size for LReBaCuO single domains with high values of TC and JC is desirable. However, it has been found that some unexpected spontaneous nucleation actions always take place, which interrupt the growing process of the single domains. In this paper, the behavior of spontaneous nucleation in SmBaCuO–Ag solution has been investigated systematically. Experimental results reveal that the spontaneous nucleation that frequently takes place during the growing process could be eliminated greatly by reducing the cooling rate to a proper level. Based on the framework of the constitutional super-cooling theory, combined with the results obtained in experiments, we discuss the possible explanations for the spontaneous nucleation behavior in SmBaCuO–Ag solution. An assumption that the distribution of solute concentration CL, as well as the solid–liquid phase transition temperature TL, in SmBaCuO–Ag solution might be of a time-dependent nature is put forward. A graph of temperature versus time has been worked out based on the assumption, which matches the growth process behavior satisfactorily with the experimental results.

Thermally activated flux motion in melt texture growth Gd-Ba-Cu-O bulk has been studied by ac susceptibility measurements. The irreversibility line Birr(T) and the intrinsic pinning energy U(T, B) of the bulk have been extrapolated from the measurements, which can be written as Birr(T) = BO(1-T/Tc)n where 80T < BO < 98T and 1.4 < n < 1.48, and U(T,B)=U0(1−t)1.5B−0.8 where t is the reduced temperature T/Tc and B is magnetic field, respectively. Also experiments reveal that peak temperature Tp of the out of phase component χ'' max(T) shifts towards low temperature region with the decreasing of the ac field. All these results suggest that the thermally activated flux motion process might be based on the Bean's critical state model, rather than thermally assisted flux-flow (TAFF) process.

Single domain GdBaCuO bulk superconductors have been fabricated by applying the melt-textured method with doping Gd211 particles of different initial sizes in air. The fine Gd211 phase was synthesized by Pechini method. Compared to Gd211 phase fabricated by solid state reaction, the distribution of the size and shape of the fine Gd211 particles is homogenous. The enhancement of critical current density has been observed for the sample with the employment of fine Gd211 starting powder, in which Jc has reached 5.3 ? 104 A/cm2 at 77 K and self-field. This can be ascribed to the refinement of Gd211 inclusions trapped in bulk superconductors

A new approach for growing large size single domains of Y–Ba–Cu–O by a top-seeded melt-textured growth (TSMTG) process is reported. Contrary to the commonly used TSMTG method using a small seed crystal that has been difficult to use to grow well-textured single domains with diameters above 50 mm, we adopt a large well-textured SmBCO bulk with a size of 14 × 14 mm2 as a seed to grow YBCO single domains. Experimental results show that this new approach can not only quicken the growth rate of the bulk, but also result in a better textured structure. By using this method, large YBCO single domains of up to 53 mm in diameter have been successfully produced and 75 mm diameter samples can also be grown. Microstructure analysis of these as-grown YBCO bulks shows a good c-axis orientation in crystallization, and magnetic levitation force measurements show that the bulks 53 mm in diameter have excellent magnetic levitation performance, with levitation force of up to 334 N (77 K, 0.5 T), corresponding to a force density of 15.2 N cm−2.