To check the validity of the theory of nonextensive statistical mechanics, we have investigated the nonextensive degree of the solar interior and have tried to find the experimental evidence by helioseismological measurements that q is different from unity. We are able to derive a parameter for providing a lower limit to the nonextensive degree inside the Sun that can be uniquely determined by the solar sound speeds measured by helioseismology. After calculating the parameter by using the solar sound speeds, we get the lower limit of (1 − q) ≥ 0.1902 for all solar radii between 0.15R and 0.95R and (1 − q) ≈ 0.4 for the out layers, 0.75R ≤ r ≤ 0.95R . Thus, the result that the nonextensive parameter q is significantly different from unity has received the support by the experiment measurements in helioseismology.
Abstract:We investigate the dispersion relation and Landau damping of ion acoustic waves in the collisionless magnetic-field-free plasma if it is described by the nonextensive -distributions of Tsallis statistics. We show that the increased numbers of superthermal particles and low velocity particles can explain the strengthened and weakened modes of Landau damping, respectively, with the -distribution. When the ion temperature is equal to the electron temperature, the weakly damped waves are found to be the distributions with small values of . . It is known that there are two models for the ion acoustic waves [4]: one is the continuum models, in which the plasma is treated as a fluid and so the fluid dynamics is used for its theoretical studies; the other one is based on the kinetic equations in statistical theory, where the distribution functions are used to describe the properties of the ion acoustic waves. As is well-known, Maxwellian distribution in Boltzmann-Gibbs (B-G) statistics is believed valid universally for the macroscopic ergodic equilibrium systems, but for the systems with the long-range interactions, such as plasma and gravitational systems, where the non-equilibrium stationary states exist, Maxwellian distribution might be inadequate for the description of the systems. For example, the experimentally measured phase velocity of the ion acoustic waves was 70% higher than the theoretical value derived under the presupposition that the plasma is described by Maxwellian distribution [5]. In the experiment for measuring the ion acoustic waves, the energy distribution of electrons may be actually not the Maxwellian one and hence we are hard to determine the valid electron temperature [6]. In fact, the non-Maxwellian velocity distributions for electrons in plasma were already measured in the experiment where the temperature 1
The instability of current-driven ion-acoustic waves in the collisionless magnetic-field-free space plasma is investigated by using a nonextensive approach. The ions and the electrons are thought of in the power-law distributions that can be described by the generalized q-Maxwellian velocity distribution and are considered with the different nonextensive q-parameters. The generalized q-wave frequency and the generalized instability q-growth rate for the ion-acoustic waves are derived. The numerical results show that the nonextensive effects on the ion-acoustic waves are not apparent when the electron temperature is much more than the ion temperature, but they are salient when the electron temperature is not much more than the ion temperature. As compared with the electrons, the ions play a dominant role in the nonextensive effects.
Perovskite-based light-emitting diodes
(PeLEDs) are promising candidates
for next-generation solid-state lighting and display technologies.
However, all current high-performance PeLEDs contain a toxic element
(lead) and suffer from relatively low stability. Herein, we report
a new type of lead-free LED using low-cost, eco-friendly, and robust
copper(I) iodide hybrid material as the emissive layer (EML). Specifically,
they are composed of copper iodide chains and organic ligands through
ionic and coordinate bonds. Their remarkable stability and solution
processability stem from this unique multifold bonding feature. High-quality
thin films of 1D-Cu4I6(bttmp)2 were fabricated by a simple, one-step spin-coating
process. They exhibit high photoluminescence quantum yield (91%) and
long-term air stability (>2000 h). An EQE of 5.02% was achieved
for
a prototype yellow LED using 1D-Cu4I6(bttmp)2 EML. Its half-lifetime of 35.5 h obtained
in open air outperforms that of most PeLEDs reported to date. This
work opens a new direction for making LEDs based on ecofriendly and
robust hybrid materials.
In this paper, we study the hybrid precoding structures over limited feedback channels for massive multiuser multiple-input multiple-output (MIMO) systems. We focus on the system performance of hybrid precoding under a more realistic hardware network model, particularly, with inevitable dissipation.The effect of quantized analog and digital precoding is characterized. We investigate the spectral efficiencies of two typical hybrid precoding structures, i.e., the sub-connected structure and the fullyconnected structure. It is revealed that increasing signal power can compensate the performance loss incurred by quantized analog precoding. In addition, by capturing the nature of the effective channels for hybrid processing, we employ a channel correlation-based codebook and demonstrate that the codebook shows a great advantage over the conventional random vector quantization (RVQ) codebook. It is also discovered that, if the channel correlation-based codebook is utilized, the sub-connected structure always outperforms the fully-connected structure in either massive MIMO or low signal-to-noise ratio (SNR) scenarios; otherwise, the fully-connected structrue achieves better performance. Simulation results under both Rayleigh fading channels and millimeter wave (mmWave) channels verify the conclusions above.J. Du is with the National
The instability of the dust-acoustic waves driven by drifting electrons and ions in a dusty plasma is investigated by the kinetic theory. All the plasma components (electrons, ions and dust particles) are assumed to be the Lorentzian κ (kappa)-distributions. The spectral indexes of the -distributions for the three plasma components are different from each other. The obtained instability growth rate depends on the physical quantities of the plasma not only, but on the spectral indexes. The numerical results for the κ κ κ -effect on the instability growth rate show that, if the normalized wave number is small, the index of electrons has a stabilized effect on the dust acoustic waves and the index of ions has an instability effect on the waves, but if the normalized wave number is large, they both nearly have no any effect on the waves. In reverse, the index of dust grains has nearly no any effect on the instability growth rate if the normalized wave number is small, but it has a stabilized effect on the dust waves if the normalized wave number is large.
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