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To deepen the understanding of CuI that emerges as a promising nextgeneration transparent display material, we investigate the temperature effect on the electronic structures of its room-temperature phase γ-CuI. Using density-functional-theory-based approaches, we investigate the bandgap renormalization, which is contributed by the electron-phonon (elph) interaction and lattice thermal expansion. Different from most semiconductors, the bandgap widens as temperature increases, although it only widens by 88.3 meV from 0 to 600 K. In addition, based on the temperature-dependent band structure and conventional Drude model, we investigate the influences of the effective masses and evaluate the hole mobilities limited by phonon scattering along different directions. The calculated mobilities agree well with existing experimental values. Our study not only provides a fundamental understanding of the temperature effect on the electronic structure of CuI, but also gives insights for further improvement of the electronic and thermoelectric devices based on CuI.

GeSe has recently emerged as a photovoltaic absorber material due to its attractive optical and electrical properties as well as earth abundancy and low toxicity. However, the efficiency of GeSe thin-film solar cells (TFSCs) is still low compared to the Shockley–Queisser limit. Point defects are believed to play important roles in the electrical and optical properties of GeSe thin films. Here, we perform first-principles calculations to study the defect characteristics of GeSe. Our results demonstrate that no matter under the Ge-rich or Se-rich condition, the Fermi level is always located near the valence band edge, leading to the p-type conductivity of undoped samples. Under Se-rich condition, the Ge vacancy (VGe) has the lowest formation energy, with a (0/2–) charge-state transition level at 0.22 eV above the valence band edge. The high density (above 1017 cm−3) and shallow level of VGe imply that it is the p-type origin of GeSe. Under Se-rich growth condition, Sei has a low formation energy in the neutral state, but it does not introduce any defect level in the band gap, suggesting that it neither contributes to electrical conductivity nor induces non-radiative recombination. In addition, Gei introduces a deep charge-state transition level, making it a possible recombination center. Therefore, we propose that the Se-rich condition should be adopted to fabricate high-efficiency GeSe solar cells.

The Large sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution spectral survey of Galactic Nebulae (MRS-N) has conducted for three years since Sep. 2018 and observed more than 190 thousands nebular spectra and 20 thousands stellar spectra. However, there is not yet a data processing pipeline for nebular data. To significantly improve the accuracy of nebulae classification and their physical parameters, we developed the MRS-N Pipeline. This article presented in detail each data processing step of the MRS-N Pipeline, such as removing cosmic rays, merging single exposure, fitting sky light emission lines, subtracting skylight, wavelength recalibration, measuring nebular parameters, creating catalogs and packing spectra. Finally, a description of the data products, including nebular spectra files and parameter catalogs, is provided., Accepted for publication in RAA. 17 pages, 9 figures, 1 table

The γ-phase cuprous iodide (CuI) emerges as a promising transparent p-type semiconductor for next-generation display technology because of its wide direct band gap, intrinsic p-type conductivity, and high carrier mobility. Two main peaks are observed in its photoluminescence (PL). One is short wavelength (410–430 nm) emission, which is well attributed to the electronic transitions at Cu vacancy, whereas the other long wavelength emission (680–720 nm) has not been fully understood. In this paper, through first-principles simulations, we investigate the formation energies and emission line shapes for various defects, and discover that the intrinsic point defect cluster V I + Cu i 2 + is the source of the long wavelength emission. Our finding is further supported by the prediction that the defect concentration decreases dramatically as the chemical condition changes from Cu-rich to I-rich, explaining the significant reduction in the red light emission if CuI is annealed in abundant I environment.

To gain fundamental understanding of the high-temperature optical gas-sensing and light-energy conversion materials, we comparatively investigate the temperature effects on the band gap and optical properties of rutile and anatase TiO2 experimentally and theoretically. Given that the electronic structures of rutile and anatase are fundamentally different, i.e. direct band gap in rutile and indirect gap in anatase, it is not clear whether these materials exhibit different electronic structure renormalizations with temperature. Using ab initio methods, we show that the electron-phonon interaction is the dominant factor for temperature band gap renormalization compared to the thermal expansion. As a result of different contributions from the acoustic and optical phonons, the band gap is found to widen with temperature up to 300 K, and to narrow at higher temperatures. Our calculations suggest that the band gap is narrowed by about 147 meV and 128 meV at 1000 K for rutile and anatase, respectively. Experimentally, for rutile and anatase TiO2 thin films we conducted UV-Vis transmission measurements at different temperatures, and analyzed band gaps from the Tauc plots. For both TiO2 phases, the band gap is found to decrease for temperature above 300 K quantitatively, agreeing with our theoretical results. The temperature effects on the dielectric functions, the refractive index, the extinction coefficient as well as the optical conductivity are also investigated. Rutile and anatase show generally similar optical properties, but differences exist in the long wavelength regime above 600 nm, where we found that the dielectric function of rutile decreases while that of anatase increases with temperature increase.

Studies of the deep energy levels and nonradiative carrier capture induced by sulfur doping in silicon were initiated 60 years ago; however, the defect configurations, their deep energy levels, and the carrier capture cross sections are still not well understood. In this study, we focus on SSi substitution, and perform a first-principles study of its defect configurations and the deep energy levels using hybrid exchange-correlation functional. We discover a new distortive configuration for SSi + besides the previously obtained structure with higher symmetry. For both SSi + configurations, the deep transition levels ε (0/+) and ε (+/2+) are determined as 0.35 eV and 0.68 eV below the conduction band minimum, respectively. As a benchmark calculation, the hole-capture cross sections for neutral and +1 charged states are obtained based on the distortive structure. The cross section for SSi + agrees with the experiment, demonstrating the multi-phonon process for SSi + capturing a hole, whereas the cross section of SSi 0 is significantly lower than the experimental data because hole capture by SSi 0 is an Auger-type process. Our calculations provide a benchmark for the evaluation of the cross section of carrier capture in semiconductors using multi-phonon nonradiative recombination theory.

The superfluid states of attractive Hubbard model in α–T 3 lattice are investigated. It is found that one usual needs three non-zero superfluid order parameters to describe the superfluid states due to three sublattices. When two hopping amplitudes are equal, the system has particle–hole symmetry. The flat band plays an important role in superfluid pairing near half filling. For example, when the filling factor falls into the flat band, the large density of states in the flat band favors superfluid pairing and the superfluid order parameters reach relatively large values. When the filling factor is in the gap between the flat band and upper band, the superfluid order parameters take small values due to the vanishing of density of states. The superfluid order parameters show nonmonotonic behaviors with the increase of filling factor. At last, we also investigate the edge states with open boundary conditions. It is shown that there exist some interesting edge states in the middle of quasi-particle bands.

The nanoflakes of SnS2/SnO2 heterostructure and SnS2 were synthesized by a one-step SnO2-templated chemical vapor deposition method. The metal oxide-assisted growth mechanism of SnS2/SnO2 heterostructure and SnS2 nanoflakes were realized through investigating serial microstructures of products with varied growth time. Furthermore, the photocatalytic activity for MB dyes degradation of varied growth time products was used to explore the effect of product microstructure under the visible light irradiation. The SnO2/SnS2 heterostructure and the oxide vacancies of nanoflakes demonstrated an improved visible light photocatalytic performance for MB degradation, which was around twice of the pure SnS2 nanoflakes and better than P25. The results of different scavengers on the degradation efficiency for MB indicate the·O2 −, and ·OH are the main active species in the photodegradation reaction. The one-step growth mechanism of SnS2/SnO2 could prove a facile process to grow metal oxide-metal sulfide heterostructure.

Since Sep. 2018, LAMOST started the medium-resolution (R $\sim 7500$) spectral survey (MRS). We proposed the spectral survey of Galactic nebulae, including \hii\ regions, HH objects, supernova remnants, planetary nebulae and the special stars with MRS (LAMOST MRS-N). LAMOST MRS-N covers about 1700 square degrees of the northern Galactic plane within $40^\circ < l < 215^\circ$ and $-5^\circ < b < 5^\circ$. In this 5-year survey, we plan to observe about 500 thousand nebulae spectra. According to the commissioning observations, the nebulae spectra can provide precise radial velocity with uncertainty less than 1 km s$^{-1}$. These high-precision spectral data are of great significance to our understanding of star formation and evolution., Submitted to RAA. 13 pages, 7 figures, 1 table

This paper details the fabrication of unitary and binary nanocolloid arrays using the spin coating technique. Polystyrene spheres of 900 and 100 nm in size were overlaid on the surface of a silicon substrate using a spin coater. To prepare the unitary nanosphere arrays, nanosphere latex spheres of 900 or 100 nm were first mixed with surfactant solution and then spin-coated onto the silicon substrate. For the binary spin coating, both 900 and 100 nm colloidal nanospheres were mixed with surfactant solutions and then concurrently spin-coated. Fabricated nanosphere arrays were evaluated via both scanning electron and atomic force microscopy. The influence of processing parameters, including type of surfactant, nanosphere to surfactant ratio, spin speed, and spin time on the ordering of colloidal array have been identified; after this step is complete, steps can be taken to optimize the process. These steps provide advantages in terms of improved nanosphere array quality.

In screw rotors manufacturing, milling machining can be conducted by using a disk-like form-milling cutter. Design method of a disk-like form-milling cutter with multiple inserts applied on screw rotors machining for twin-screw compressors were presented in this study. An analytical calculation procedure of insert arrangement on the cutter body profile was constructed. Subsequently, the screw rotor cutting simulation was performed by considering the actual cutting conditions based on a horizontal CNC milling machine’s established coordinate system. Finally, the simulated rotor profile could be obtained and the normal deviation was evaluated.

Experimental and theoretical studies are combined to investigate the phenomenon of macroscopic plastic deformation localization in metallic tensile specimens of AL6061, HSLA350 and Q235. The longitudinal strain and cross-section reduction of the specimens at different instant during testing are estimated through the measurement technique of three dimensional digital image correlation (3D-DIC). The Ling weighted-average method referred as WAM is used to compare the true stress-strain relation obtained from the experiment. A new mathematical model is suggested to estimate the localization zone length, which is a crucial parameter that can be used to anticipate the behaviour of metals past the peak load. The effect of material property on the necking zone length is examined. The experimental results show that the axial strain within the necking zone is non-uniform. It is also found that the WAM can precisely derive the true stress of steels Q235 and HSLA350 but not AL6061. The localization zone length of the round specimens Q235, HSLA350, and AL6061 equals six, five, and four times their initial diameter, respectively. Materials with a higher fracture strain ratio to the ultimate strain have a shorter necking zone length. This work provides insights into the physical mechanism of macroscopic plastic deformation localization.

AlAs is a semiconductor that can form heterostructure, superlattice, and ternary alloy with GaAs. We systematically investigate the formation energies, transition energy levels, as well as defect and carrier densities of intrinsic defects and extrinsic impurities in AlAs using first-principles simulations. Most of the intrinsic defects, including vacancies, antisites and interstitials, show similar features as those of GaAs. Intrinsic defects are found not to be the origin of the n-type or p-type conductivity due to their high formation energies. For extrinsic dopants (Si, C, Mg and Cu), Mg can be an effective p-type dopant under both As-rich and As-poor conditions. Si-doping can introduce either n-type or p-type, depending on the specific growth condition. C serves as a p-type dopant under As-poor and As-moderate conditions, and Cu-doping has little effect on the conductivity.

A finite element model was established and modal analysis was performed on a wind turbine main shaft. By adjusting the length of the expansion sleeve, the effect of the length of the expansion sleeve on the natural frequency of the wind turbine shaft was summarized. The results show that the greater the length of the expansion sleeve, the greater the natural frequency of the wind turbine shaft.

TiAl-based alloys have received extensive attention recently due to their excellent properties. However, the weak oxidation resistance at temperatures higher than 800 °C can limit their further high-temperature structural applications. To improve the oxidation resistance of a high-Nb-content γ-TiAl alloy (Ti-45Al-8.5Nb, in units of at.%), a chromium (Cr) coating is prepared by using the plasma surface alloying technique, separately, at 800 °C and 1000 °C. The x-ray diffraction (XRD) patterns reveal that an oxide surface layer consisting of Cr2O3, Al2O3, and TiO2 is produced on the Cr-coated Nb containing γ-TiAl substrates during the initial oxidation. However, the Cr2O3 is dominated in the oxide surface layer after being isothermally oxidized for 300 h. The oxidation kinetic curves are composed of a parabolic law stage (≤ 90 h) and a biquadratic law stage (≥ 90 h), fit by weight–gain curves. Due to diffusion in the fabrication process and oxidation process, the Cr-coated specimens have an adhesion force after being isothermally oxidized, specifically 69 N for a specimen after oxidation for 300 h. These results demonstrate that the Cr coating enhances the oxidation resistance and adhesion of a Ti-45Al-8.5Nb alloy, which may provide a new feasible scheme for designing oxidation protection layers.

With the vigorous development of wind power generation worldwide, the problem of stress concentration at the position of the main shaft shoulder of the wind turbine has become increasingly prominent. Therefore, a finite element model was established for the main shaft of a wind turbine, and the stress field of the main shaft of the wind turbine under the limit load condition was simulated and calculated, and the influence of the position of the shoulder on the flange side on the stress concentration under different radii of curvature was analyzed. It provides important guidance for the manufacture and inspection of the main shaft of the wind turbine.

Organosilicate (OSG) low dielectric constant films containing different concentrations of 1,3- and 1,3,5-benzene bridges between Si atoms are fabricated using 1,3,5-tribromobenzene via spin-on deposition and evaporation induced self-assembling. Chemical composition, pore structure, mechanical, dielectric and hydrophobic properties of as-prepared benzene bridged OSG thin films are studied using Nuclear magnetic resonance, Fourier-transform infrared spectroscopy, Ellipsometric porosimetry, Nanoindentation, CV measurements and water contact angle. The precursors were synthesized by using two methods with the goal of understanding the effect of 1,3,5-benzene concentration on the films properties. It is shown that the films have very small pore size that is not changing with porosity. No significant change in mechanical properties was observed at two different ratios of 1,3- and 1,3,5-benzene bridged films.

Reuse of concrete waste in novel construction is becoming very important topic nowadays. This study focuses to examine the post-cracking and mechanical performance, fracture behavior, and micro-structure of fiber strengthened recycled aggregate concrete (RAC). For this purpose, crack mouth opening diameter (CMOD) tests were conducted on twenty-seven notched beam specimens (550 × 150 × 150 mm) having three replacement levels (i.e., 0, 50 and 100%) of recycled concrete aggregates (RCA) and three synthetic fiber dosages (i.e., 0, 0.5 and 1%). Different mechanical properties of all mixes were also examined following ASTM standards. Drop in the mechanical performance of RAC was noticed at higher RCA replacement levels. However, synthetic fiber reinforced RAC showed better performance as compared to plain RAC. Results also depict positive influence of synthetic fiber addition on the residual flexural tensile strength of concrete. Approximately, 129% and 380% rise in toughness index and fracture energy was also observed for 1% fiber incorporation in RAC. Moreover, scanning electron microscopic analysis also confirmed the synthetic fiber-mortar bond. Therefore, synthetic fibers enhance the post-cracking and mechanical performance of fiber reinforced RAC resulting into more ductile and energy absorbing sustainable concrete.

This study mainly discussed the influence of different surface properties,namely an unmodified copper fin surface and a modified hydrophobic fin surface, on the heat transfer effect of heat exchangers with air velocity ranging from 0.5 m/s to 2.5 m/s and relative humidity of 60% and 90%. The researchers established the following conclusions based on the experiment results. The heat transfer and water removal rates of the two heat exchangers increased with an increase in wind velocity. When the inlet air velocity was increased from 0.5 to 2.5 m/s, the heat transfer and water removal rates of both heat exchangers were increased by approximately 90%.Under similar air velocity conditions, heat exchangers with hydrophobic surfaces constantly removed the condensed water droplets, thereby preventing the water droplets from causing surface thermal resistance. As a result, the condensation heat transfer effect of hydrophobic surfaces was greater than that of unmodified copper surfaces. Compared with heat exchangers with unmodified copper fin surfaces, heat exchangers with hydrophobic surfaces exhibited a 5.56% higher heat transfer efficiency.

We study the properties of breather interactions in nonlinear Kerr media with self-steepening and spacetime correction and with either self-focusing or self-defocusing nonlinearity, and present a new family of exact breather solutions via the Darboux transformation with a special-designed quadratic spectral parameter. In contrast to the previous results of the nonlinear Schrödinger equation (NLSE) hierarchy, we show that the relative phase of colliding breathers has a significant effect on the collision manifestation. In particular, only the out-of-phase interactions can generate small amplitude waves at the collision center, which are analogous to the NLSE super-regular breathers. Our results will deepen our understanding of the properties of breather interactions and they will offer the possibility of experimental observations of super-regular breather dynamics in systems with self-steepening and spacetime correction.

Costly and non-environment-friendly methods are used to improve the inferior behavior of recycled aggregate concrete (RAC). Conversely, the strength enrichment of concrete due to confinement provided by lateral reinforcement is ignored in the design of concrete compression members. The focus of this study is to investigate the role of pre-existing transverse reinforcement and different design strengths of concrete on the stress strain behavior of RAC. For this reason, stress-strain behavior of spiral steel confined concrete specimens having variable confinement pressure, recycled aggregates (RA) replacement percentage and design strength is investigated. The results show a drop in compressive strength of concrete with the increase in replacement percentage of RA. However, steel confinement has a positive role to counterbalance the adverse effect of RA replacement on concrete strength. Improved ductility and stress-strain behavior of RAC are observed with the increase in confinement pressure. Based on the results, the un-utilized pre-existing steel spiral reinforcement in the concrete compression members can offset the inferior performance of RAC resulting into sustainable and cost-effective construction.

This paper investigates the random dopant fluctuation of multi-gate metal–oxide–semiconductor field-effect transistors (MOSFETs) using analytical solutions of three-dimensional (3D) Poisson’s equation verified with device simulation. Especially, we analyze the impact of aspect ratio on the random dopant fluctuation in multi-gate devices. Our study indicates that with a given total width, lightly doped fin-type FET (FinFET) shows the smallest threshold voltage (Vth) dispersion because of its smaller Vth sensitivity to the channel doping. For heavily doped devices, quasi-planar shows smaller Vth dispersion because of its larger volume. The Vth dispersion caused by random dopant fluctuation may still be significant in the lightly doped channel, especially for tri-gate and quasi-planar devices. [DOI: 10.1143/JJAP.47.2097]

The interface microstructure in a simulated sandwich structure of Ni base-metal electrode and BaTiO3 dielectric has been studied by transmission electron microscopy. Some Ni grains have been oxidized to NiO; most of them although coarsened and poorly densified remained Ni metal. NiO formed during the reoxidation step at 1000 °C because the partial pressure of oxygen (pO2 ≈ 10−6 atm) in the controlled-sintering atmosphere was higher than the thermodynamic equilibrium value of pO2 = 4.68 × 10−11 atm. Crystallographic orientation relationships between NiO and BaTiO3 at the interface were determined. The BaTiO3–NiO interface was both twist and tilt boundaries that are characterized by dislocations of a mixed nature with Burgers vectors b = ½ 0 0 1 and ½ 1 1 0 and 1 1 1, described in the indices of pseudo-cubic BaTiO3. Dislocation loops were also found in BaTiO3 as well as along the NiO–BaTiO3 interface; the latter with was a vacancy loop formed by condensation of intrinsic Schottky defects. The Ni–BaTiO3 interface is built on and a configuration with opposite-charged ions stacked upon each other was energetically more favourable. The lattice mismatch was accommodated by misfit partials with b = ½ 1 1 0 that were dissociated from perfect dislocations with b = 1 1 0 probably by glide in on the metal–dielectric interface.

The effects of sintering conditions on the densification, microstructural evolution and microwave properties of Ba(Ti1-xMnx)O3 ceramics were investigated in this study. For x0.25, densification is achieved at a temperature as low as 1250 °C. For x> 0.25, a significant densification starts only at temperatures above 1350 °C, owing to the existence of a Ba2Ti5O12 phase. X-ray photoelectron spectroscopy results manifest a change in the chemical state of Mn from Mn2+ to Mn4+ when the Mn content in the Ba(Ti1-xMnx)O3 ceramics is increased. A ≈0.9 wt % weight gain is obtained when Ba(Ti0.85Mn0.15)O3 powder is heated to 1500 °C, presumably owing to the transformation of Ba(Ti0.85Mn0.15)O2.85 to Ba(Ti0.85Mn0.15)O3, associated with the conversion of Mn2+ to Mn4+ as temperature increases. The microstructural evolution and microwave dielectric properties of the Ba(Ti1-xMnx)O3 ceramics are also affected by sintering temperature and Mn content. For Ba(Ti0.85Mn0.15)O3 ceramics, as a typical example, er varies from 52 to 60 and Qfr changes from 2,000 to 12,000 as sintering temperature increases from 1200 to 1500 °C. However, τf ranges from 200 to 250 ppm/°C, which is independent of sintering temperature.

α-Al2O3 nanowires have been synthesized in bulk quantity by using simple physical evaporation of mixture of pure Al powders and nanometre-sized TiO2 powders at 1150 °C. Scanning electron microscopy and transmission electron microscopy observations show that α-Al2O3 nanowires have diameters ranging from 20 to 60 nm and lengths up to several tens of micrometres. The growth of α-Al2O3 nanowires is controlled by the vapour–liquid–solid (VLS) mechanism. Photoluminescence measurements revealed a blue luminescence band in the wavelength range of 400–500 nm with two peaks at 415 and 440 nm, which could be attributed to the F+ centres in the α-Al2O3 nanowires.

We obtain the necessary and sufficient conditions for linearizability (isochronicity) of three families of eight-parametric cubic systems. This completes the classification of the linearizable systems studied by Romanovski and Robnik (2001 J. Phys. A: Math. Gen. 34 10267–92).

The pygmy and giant dipole resonances in proton-rich nuclei 17,18Ne are investigated with a fully self-consistent approach. The properties of ground states are calculated in the Skyrme Hartree–Fock with the Bardeen–Cooper–Schrieffer approximation to take into account the pairing correlation. The quasiparticle random phase approximation (QRPA) method is used to explore the properties of excited dipole states. In the calculations the SLy5 Skyrme interaction is employed. In addition to the giant dipole resonances, pygmy dipole resonances (PDR) are found to be located in the energy region below 10 MeV in both 17,18 Ne. The strength and transition density show that the low-lying states are typical PDR states. However, analyzing the QRPA amplitudes of proton and neutron 2 quasiparticle (2qp) configurations for a given low-lying state in 17,18 Ne, we find that the PDR state is less collective, more like a single 2qp excitation.

Anatase TiO2 nanoparticles with different amounts of fluorine doping were synthesized by a hydrothermal method using hydrogen titanate nanotubes as a precursor and applied as mesoporous layer for preparing perovskite solar cell. The morphology and structures were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), meanwhile, the properties and performances were tested by photoluminescence spectrum (PL) and current density and voltage (J-V) curve. It was found that doping fluorine into TiO2 made the photoelectric conversion efficiency (PCE) of perovskite solar cell (PSC) to be improved. The best PCE of PSC based on a F-doped TiO2 was 13.06% and increased by 51% compared to an un-doped TiO2. The study provided a direction for the exploration of high performance electron transport layer of perovskite solar cell.

A numerical simulation used to compute the spatio-temporal dynamics of pulse formation of diode-pumped Q-switched Yb:YAG laser is carried out. The model takes the laser amplification and gain saturation, the properties of the laser cavity, and the diffractive effects of the laser disc into account. The numerical calculation is performed for a confocal positive-branch unstable resonator with a super Gaussian coupling mirror. The simulation results show that the laser pulse starts from a Gaussian intensity distribution and becomes rapidly non-Gaussian. The corresponding beam quality M2 factor is seen to vary approximately from 1.5 at the beginning of the formation of pulse to more than 10 in the tail of the pulse, with a value of 11.6 at the peak of the pulse.