Modern Physics Letters B

At present, hydrogen-based compounds constitute one of the most promising classes of materials for applications as phonon-mediated high-temperature superconductors. Herein, the behavior of the superconducting phase in tellurium hydride (HTe) at high pressure (p = 300 GPa) is analyzed in detail, by using the isotropic Migdal–Eliashberg equations. The chosen pressure conditions are considered here as a case study which corresponds to the highest critical temperature value $(T_c)$ in the analyzed material, as determined within recent density functional theory simulations. It is found that the Migdal–Eliashberg formalism, which constitutes a strong-coupling generalization of the Bardeen–Cooper–Schrieffer (BCS) theory, predicts that the critical temperature value ($T_c=52.73$ K) is higher than previous estimates of the McMillan formula. Further investigations show that the characteristic dimensionless ratios for the thermodynamic critical field, the specific heat for the superconducting state, and the superconducting band gap exceed the limits of the BCS theory. In this context, also the effective electron mass is not equal to the bare electron mass as provided by the BCS theory. On the basis of these findings it is predicted that the strong-coupling and retardation effects play pivotal role in the superconducting phase of HTe at 300 GPa, in agreement with similar theoretical estimates for the sibling hydrogen and hydrogen-based compounds. Hence, it is suggested that the superconducting state in HTe cannot be properly described within the mean-field picture of the BCS theory.

As an essential dynamic evolving mechanism, triangle behavior can be observed ubiquitously in the real world. Combining transfer mechanism with weighted dynamic, in this paper, we propose a new community model and deduce the strength distribution. Consistent with the theoretical results, numerical simulations show decent right-skewed scale-free characters of strength distribution. Moreover, we calculate some important coefficients to analyze the correlations of nodes and demonstrate the disassortative property of this model. Finally, the process of epidemic spreading with different weighted transmission rate is introduced on the weighted community network, and the results indicate that the triangle behavior has a significant influence on the dynamic of the epidemic spreading. Composed with the models proposed already, our model is supposed to be closer to the realistic network and imitate the real system more accurately and exactly.

The tunable narrow band perfect metamaterial absorber (PMA) based on guided-mode resonance (GMR) for the visible spectral region is proposed. The PMA is composed of a one-dimensional grating layer, two waveguide layers and an Ag substrate. Tunable narrow band PMAs are designed using rigorous coupled-wave analysis by comparing the GMR effects for the filters and absorbers. Afterwards, two tunable PMA samples are fabricated through thin-film deposition and ultraviolet lithographic patterning. Finally, the reflection spectra of the fabricated PMA samples are measured. The absorption spectra obtained by subtracting the measured reflection spectra from 1 are consistent with the theory.

Damage caused by abrasive wear is a significant problem for hydraulic machinery in rivers with sediments. Traditional prediction methods of abrasive wear morphology with the fixed geometrical boundary are difficult to reflect the physical reality of wear because of the interaction of sediment wear, flow pattern and flow boundary. In this study, a gradual wear method based on the idea of differential-quadrature is established to investigate the asymptotic wear behavior of hydraulic machinery. The average wear rate and depth of voxels on the geometrical boundary can be obtained by the unsteady numerical simulation with RNG $k$-$𝜀$ turbulent model and DPM multiphase flow model. Segmented voxels of geometrical boundary of flow are reconstructed after a calculation period until the end of the total running time. So, the progressive wear morphologies of flow-passage walls can be revealed step by step. The prediction method is used to predict the wear of the clearance flow in the guide vane. The numerical results are in good agreement with the actual wear depth on the wear surfaces at the actual running time, which indicates that the specified prediction method in this paper is applicable and effective.

In this paper, a novel theoretical model has been developed to obtain focal points of temperatures in helium cooled ceramic breeder (HCCB) blanket system of China Fusion Engineering Test Reactor (CFETR). The main objective of the paper is to develop a theoretical-computational model for safety of blanket system, structure stress analysis and feasibility design. The theoretical-computational model was developed and verified by computational techniques using C++/MATLAB program and later with thermo-hydraulic system codes, i.e. RELAP5 and THEATRE. Mathematical model was developed for the thermal conductivity in HCCB blanket system and heat conduction model by using numerical technique. This model was then transferred to C++/MATLAB program and developed a program for calculating the thermal contact temperature of HCCB region. The calculated temperature values were then compared with RELAP5 and THEATRE codes for the accuracy of theoretical model. The preliminary thermal-hydraulic simulation results indicate that the maximum temperature on the first wall (FW) satisfies the design allowable limit and that the cooling channels were designed accurately. The results obtained from these analyses are very close to the experimentally defined values depicting the accuracy of theoretical and simulation results. The calculated results can be applicable to other tokamak devices like CFETR, ITER and JET as well.

In this paper, the (2+1)-dimensional CDGKS equation is studied and its diverse soliton solutions consisting of line soliton, periodic soliton and lump soliton with different parameters are derived based on the Hirota bilinear method and long-wave limit method. Based on exact solution formulae with different parameters, the interaction between line soliton and periodic soliton, the interaction between line soliton and lump soliton, as well as the interaction between periodic soliton and lump soliton are illustrated. According to the dynamical behaviors, it can be found that the effects of different parameters are on the propagation direction and shapes. Novel soliton interaction phenomena are also observed.

Four different sensor devices were fabricated using the deposition of gold and nickel on top of polyaniline and polyaniline/zinc oxide composite thin films on glass substrates. Prepared samples were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy and UV-Visible spectroscopy. FESEM images confirmed the formation of interwoven nanofibers for all samples with the mean diameter of about 90 nm for PANI. The responses of the prepared samples toward various concentrations of ammonia gas were investigated by conductometric measurements at room temperature. The responses of the fabricated sensors toward 100 ppm of NH₃ were obtained to be 112%, 3%, 177% and 148% for PANI/Au, PANI/Ni, PANI/ZnO/Au and PANI/ZnO/Ni samples, respectively. Results show both Ni and Au thin films as a metallic catalyst on top of PANI/ZnO nanocomposite can greatly improve the sensing characteristics toward NH₃ at room temperature. However, PANI/ZnO/Au has the highest response with the lowest response time (4 s). The mechanism for the sensitivity enhancement of the fabricated devices was discussed.

The rutile titanium dioxide (TiO₂) has attracted enormous interest in sensor field owing to its stability at high temperature. But less is known about electron transfer efficiency of rutile TiO₂, which is mainly influenced by the electron mobility. The aim of this study is to investigate the relationship between carrier mobility and bicrystalline grains boundary of rutile TiO₂ film. In this study, TiO₂ film was deposited by the direct current pulsed magnetron sputtering technology with sputtering power from 150 to 900 W. Then the TiO₂ films were annealed at $1000^{\circ }\mathrm{\text{C}}$ in air atmosphere. By this way, the rutile TiO₂ films were obtained. Special attention was paid to the carrier mobility of rutile TiO₂ films. The Hall measurement results showed that with the increase of sputtering power from 150 to 900 W, the carrier mobility of rutile TiO₂ films increased from 0.75 to $38.88{\mathrm{\text{cm}}}^2/\mathrm{\text{V}}\cdot \mathrm{\text{s}}$, gradually. Taking the TEM and SAED results together, our data indicated that the carrier mobility of rutile TiO₂ film was influenced by the bicrystalline grains boundary. The large angle bicrystalline grain boundary seriously deteriorates the carrier mobility of rutile TiO₂ film. On the contrary, the low angle bicrystalline grain boundary has little influence on the carrier mobility of rutile TiO₂ film.

Reverse horn as one of the Acoustic Black Hole (ABH) structures can be used to effectively reduce low frequency acoustic waves by focusing the sound energy. The sound waves in relatively low frequency range are focused on the tip of reverse horn, and most sound energy cannot flow out from the reverse horn’s tip. In this paper, we propose a quantitative analysis method by the bottleneck effect analogy to research the low frequency acoustic characteristics of reverse horn. Our theoretical results show that the low frequency sound wave can be focused on the tip of reverse horn, and the transmission coefficient of low frequency is proportional to the 3 power law of the reverse horn tip’s diameter. The experimental results verified our theoretical results. And the sound insulation property is studied by experiments. It is noteworthy that the insulation coefficient of two levels reverse horn whose second level tip’s diameter $d=12$ mm, is more than 0.92, and can increase further with the decrease of the second level horn tip’s diameter. It provides an effective and simple method for quantitatively analyzing the low frequency acoustic characteristics of the reverse horn. The proposed reverse horn has great potential applications for low frequency sound insulation control.

This paper reports the annealing effect on the DC sputter transparent conducting tin-doped indium oxide (ITO) films for the alkali vapor cell heater of the chip-scale atomic sensors. ITO films with a thickness of 140 nm were deposited on BF33 glass substrates at $20^{\circ }\mathrm{\text{C}}$, followed by an annealing process in N₂ atmosphere for 2 h at different temperatures between $250^{\circ }\mathrm{\text{C}}$ and $500^{\circ }\mathrm{\text{C}}$. The effect of annealing on the crystal structure, surface morphology, optical, and electrical properties of ITO films was characterized. The predominant orientation of crystal face of the as-deposited and annealed ITO thin films was (222) instead of (400). After annealing at $450^{\circ }\mathrm{\text{C}}$ the ITO film exhibits the highest transmittance ($\sim$90%) to the lights at the wavelength of 780 nm, 795 nm and 894 nm regarding the probe light in a chip scale atomic device. Besides, the lowest sheet resistance and resistivity were obtained as 27.8 $\mathrm{\Omega }/\square$ and $3.9\times 10^{-4}\mathrm{\Omega }\cdot \mathrm{\text{cm}}$ separately. The refractive index and extinction coefficients results verified the crystal orientation and the transmittance results. This thin ITO film was expected to be the best candidate for the transparent heater in the chip scale atomic devices.

Random walks on binary scale-free networks have been widely studied. However, many networks in real life are weighted and directed, the dynamic processes of which are less understood. In this paper, we firstly present a family of directed weighted hierarchical scale-free networks, which is obtained by introducing a weight parameter $𝜃$ into the binary (1, 3)-flowers. Besides, each pair of nodes is linked by two edges with opposite direction. Secondly, we deduce the mean first passage time (MFPT) with a given target as a measure of trapping efficiency. The exact expression of the MFPT shows that both its prefactor and its leading behavior are dependent on the weight parameter $𝜃$. In more detail, the MFPT can grow sublinearly, linearly and superlinearly with varied $𝜃$. Last but not least, we introduce a delay parameter p to modify the transition probability governing random walk. Under this new scenario, we also derive the exact solution of the MFPT with the given target, the result of which illustrates that the delay parameter p can only change the coefficient of the MFPT and leave the leading behavior of MFPT unchanged. Both the analytical solutions of MFPT in two distinct scenarios mentioned above agree well with the corresponding numerical solutions. The analytical results imply that we can get desired transport efficiency by tuning weight parameter $𝜃$ and delay parameter p. This work may help to advance the understanding of random walks in general directed weighted scale-free networks.

The main purpose of this work is to couple the transmission signal into the power line with a low insertion loss. The inductive coupler is simulated by using CST modeling. By means of the non-contact inductive coupler, the carrier signals on the wire with large diameter are coupled into the one with small diameter and then enter the power line carrier handling veneer, so as to realize the coupled transmission of the signals. The structure model of the inductive coupler is established, in which the key technologies are the selection of magnetic core materials and the design of the coupler structure.

A (2+1)-dimensional high-order nonlinear evolution (HNE) equation is considered in this paper. A Hirota bilinear form of the HNE equation is constructed by the dependent variable function. Solitary waves are derived by solving the Hirota bilinear form of the HNE equation. Lump waves of the HNE equation are obtained by introducing a positive quadratic function. By mixing an exponential function or two exponential functions with a quadratic function, interaction solutions between a lump and a one-soliton, and between a lump and a two-soliton are presented. For the interaction solution between a lump and a two-soliton, this kind of solution can be considered as a special rogue wave. The propagation phenomena of these explicit solutions are illustrated by some graphs.

In this research, nanocrystalline $\gamma$-${\mathrm{\text{Al}}}_2{\mathrm{\text{O}}}_3$ powders have been synthesized by a novel mechanochemical method, through thermal decomposition of the ammonium aluminum carbonate hydroxide (AACH) precursor. The route involved using low-cost ${\mathrm{\text{AlCl}}}_3\cdot 6{\mathrm{\text{H}}}_2\mathrm{\text{O}}$ and ${\mathrm{\text{NH}}}_4{\mathrm{\text{HCO}}}_3$ as raw materials and environmental-friendly soluble starch as an effective dispersant. The precursor and product were characterized by simultaneous thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that spherical $\gamma$-${\mathrm{\text{Al}}}_2{\mathrm{\text{O}}}_3$ nanoparticles without hard agglomeration and with particle size in the range of 20–30 nm can be obtained. The crystallite size of products measured from XRD, SEM and TEM were in good agreement. This novel mechanochemical method combined with the use of environmentally benign starch has the advantages of simple operation, low calcination temperature and environmental safety, and will have good prospects for commercial production.