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We report charge dynamics of a quantum spin-1/2 chain (SrCuO₂) over the complete Brillouin zone using the momentum tunability of inelastic X-ray scattering. Excitations at the insulating gap edge are found to be highly dispersive. Observed dispersions are consistent with charge fluctuations involving holons unique to 1-D spin-1/2 quantum systems.

We investigate momentum dependence of charge excitations across the effective Mott gap in a quasi-zero dimensional (q-ZD) model cuprate Li₂CuO₂, using high resolution inelastic X-ray scattering by working near a resonance. In comparison to quasi-one dimensional (q-1D) systems such as Sr₂CuO₃ or SrCuO₂, momentum dependence is much weaker in Li₂CuO₂. Particle-hole pair excitations at the gap edge in these low dimensional Mott systems are found to be strongly dependent on the effective dimensionality (or topology) of the lattice and the strength of electron–electron interaction.

We report momentum dependence of charge excitations across the effective Mott gap in quasi-low dimensional model cuprates with different effective dimensionalities (CuGeO₃ and SrCuO₂), using high resolution inelastic X-ray scattering by working near a resonance. Particle-hole pair excitations at the gap edge in these compounds are found to be strongly dependent on the effective dimensionality of the lattice and the strength of electron–electron Coulomb interaction.

In order to satisfy the requirements of precise components with tidiness, low power and high stability in the field of biological engineering, medical equipment and semiconductors etc. a pre-stress acoustic transport prototype without horn was proposed in this paper. The mechanism of levitation and transport which is driven by orthogonal waves was revealed by the analysis of waveform and squeeze film characteristics in high-frequency exciting condition; also, the electric, solid and acoustic coupled finite element method (FEM) was established to investigate the effect of pre-stress and acoustic pressure distribution in the near field. The levitation and driving capacity of near field acoustic levitation (NFAL) transport platform without horns can be proved in this experiment and further to achieve the goal of parameters optimization. The theoretical and experimental results indicate that the pre-stress has a significant effect on resonant frequency and levitating stability, the pre-stress are determined by the DC voltage offset which is related to the system working point so that we cannot increase the offset and exciting voltage unlimitedly to improve the stability. At the same time, the calculated pressure distribution of acoustic radiation can generally reflect the regional bearing capacity in near and far field for levitation. These achievements can partly solve the problem of accuracy design of prototype and thickness of gas film, supporting for accuracy close loop control of levitating height.

The main function of the on-load tap changing (OLTC) regulators consists of maintaining a constant voltage in order to feed critical loads despite the load changes or voltage changes in the ac mains. The traditional regulators are still used nowadays, but they present several disadvantages, like a slow response, which reaches from 100 ms to several seconds. These drawbacks can be overcome if the OLTC regulators would have shorter response time, commuting several times every cycle of the mains. There are two basic topologies for fast OLTC regulators. The first one consists of several taps and uses hard switching. The second one consists of two main switches commuting at high frequency, using soft-switching in order to reduce the power losses. The present topology is of the second type. This paper presents a mathematical model of the power stage of the proposed regulator. The model includes the parasitic resistances and the leakage inductances in order to obtain a better comprehension of the regulator operation. A parametric analysis has been done in order to observe the influence of the parasitic elements in the performance of the main parameters of the topology. The model is verified by experimental results obtained using a 500-W prototype.

Three different existing steady-state models with quantum correction for simulating the resonant tunnelling diode are summarized. Numerical methods and a theoretical argument for one of the models are briefly described. Results of simulation are focused on the capability of reproducing the negative differential resistivity.