Search

We report a comprehensive study on a layered-structure compound of NaZn4As3, which has been predicted to be an ideal topological semimetal (TSM) candidate. It is found that NaZn4As3 undergoes a structural transformation from high temperature rhombohedral to a low temperature monoclinic phase. The electric resistivity exhibits a metal-to-insulator-like transition at around 100 K, and then develops a plateau at low temperature, which might be related to the protected topologically conducting surface states. Our first-principles calculation confirms further that NaZn4As3 is a topological insulator (TI) for both different phases rather than a previously proposed TSM. The Hall resistivity reveals that the hole carriers dominate the transport properties for the whole temperature range investigated. Furthermore, an obvious kink possibly associated to the structure transition has been detected in thermopower around ~ 170 K. The large thermopower and moderate κ indicate that NaZn4As3 and /or its derivatives can provide a good platform for optimizing and studying the thermoelectric performance.

Due to the complicated film formation kinetics, morphology control remains a major challenge for the development of efficient and stable all-polymer solar cells (all-PSCs). To overcome this obstacle, the sequential deposition method is used to fabricate the photoactive layers of all-PSCs comprising a polymer donor PTzBI-oF and a polymer acceptor PS1. The film morphology can be manipulated by incorporating amounts of a dibenzyl ether additive into the PS1 layer. Detailed morphology investigations by grazing incidence wide-angle X-ray scattering and a transmission electron microscope reveal that the combination merits of sequential deposition and DBE additive can render favorable crystalline properties as well as phase separation for PTzBI-oF:PS1 blends. Consequently, the optimized all-PSCs delivered an enhanced power conversion efficiency (PCE) of 15.21% along with improved carrier extraction and suppressed charge recombination. More importantly, the optimized all-PSCs remain over 90% of their initial PCEs under continuous thermal stress at 65 °C for over 500 h. This work validates that control over microstructure morphology via a sequential deposition process is a promising strategy for fabricating highly efficient and stable all-PSCs.

The present commercial spinel LiMn2O4 delivers only 90 mAh/g–115 mAh/g, far lower than the theoretical specific capacity. It degrades fast caused by the Jahn–Teller effect, Mn dissolution and related side reactions that consume Li inventory. In this work, Zr doping is employed to improve the structural stability and electrochemical performance of spinel LiMn2O4. Li1.06Mn1.94–x Zr x O4 (x = 0, 0.01, 0.02, 0.04) have been successfully synthesized by a simple solid-state reaction method and evaluated as cathode for lithium ion batteries (LIB). Li1.06Mn1.92Zr0.02O4 is superior cathode material with a high capacity of 122 mAh/g at 1-C rate; long cycle stability, 98.39% retention after 100 cycles at 1-C rate, excellent high rate performance 107.1 mAh/g at 10-C rate, and high temperature performance 97.39% retention after 60 cycles. These are thought to be related to Zr doping effectively stabilizing the spinel LiMn2O4, by forming stronger Zr–O bonds in the octahedron, suppressing the Jahn–Teller effect, thus improving electrochemical performance.

The effect of vacuum preheating on the structure, electric, and optical properties of the thermally oxidized W-doped VO2 films was studied. The results show that the film crystalline orientation and the inhomogeneous distribution of W increase after preheating. It was found that preheating at 700 °C and 800 °C reduces the metal-insulator transition (MIT) hysteresis because of the preferable orientation of the film along the (011) direction. The film preheated at 900 °C exhibits an undoped-like MIT due to a great increase in the inhomogeneous distribution of W. Preheating can affect the apparent activation energy of the cool-state resistances and increase the cool-state IR transmittances. By means of the Lorentz–Drude model, the conductance electron density (n c) and energy band gaps (E g) were obtained and discussed. It was shown that preheating can decrease the cool-state n c and affect the E g, indicating that the electronic band structure is changed by W doping.

Since inverse spin Hall effect (ISHE) can transform microwave energy into direct current (DC) energy in ferromagnetic (FM)/nonmagnetic (NM) bilayer metal materials, the ISHE-based FM/NM microstrip arrays have clear potential to be used for microwave power transmission and harvesting. Driven by the need for the miniaturization of electronic devices, it is essential to study the dependence of the characteristics of FM/NM microstrip arrays on their geometries. In this work, we have experimentally demonstrated that the Py/Ta microstrip array’s ISHE signal increases linearly with an increase in the Py/Ta microstrip width and that the effective saturation magnetization of the Py film shows the same change tendency. Moreover, the anisotropy field of the Py film increases linearly as the width decreases. Our work provides a valuable reference for the future miniaturization of ISHE-based rectifier devices.

Low quantum efficiency and serious photogenerated carrier recombination have been urgent bottleneck problems for photocatalytic materials. Herein, we prepared Nb, Se-codoped ZnIn2S4/NbSe2 composites through a facile solvothermal method. The synergetic effect of codoping and cocatalyst was investigated on the photodegradation performance towards tetracycline under visible-light irradiation. By adjusting the final composition, the comprehensive characterization revealed that the optimum degradation efficiency of NS/ZIS-1.6 catalyst arrived at 75% in 70 min, which was 5.8 times higher than that of pure ZnIn2S4. Deep analysis indicated that the enhanced photocatalytic performance could be attributed to higher light absorption, more efficient electron/hole separation, faster charge transport, and lower carrier recombination. This work may offer novel viewpoint for design of high-performance catalysts towards the visible-light-driven photodegradation system.

Monoclinic VO2 films were prepared over quartz substrates through thermal oxidation of sputtered vanadium films under continuous O2 flow in a vacuum. It was found that an additional vacuum pre-heating before the thermal oxidation could have a great effect on film crystalline orientation and textual morphologies. The film exhibits a preferable growth along [011] direction and consists of uniform small inter-connected nanoparticles, while the untreated film shows (200) orientation and is composed of large irregular nanoparticles that connect via disorder boundaries. The (011) orientated film shows slightly higher full solar and IR light modulations. The electric resistance results also show that the metal–insulator transition (MIT) of the (011) orientated film presents a larger amplitude, higher sharpness, and narrower hysteresis as compared to the (200) orientated film. The difference in textual structures of the orientated films is the main physical reason that affects the MIT of m-VO2 films.

A gauge-invariant model is constructed for the reaction within a tree-level effective Lagrangian approach to understand the underlying production mechanisms and study the resonance contributions in this reaction. In addition to the t-channel K and exchanges, s-channel nucleon exchange, and interaction current, the s-channel nucleon resonance exchanges are included in constructing the reaction amplitudes to describe the data. It is found that the contributions from the s-channel exchange are required to describe the most recently measured total cross-section data for from the CLAS Collaboration. Further analysis indicates that the interaction current dominates the reaction near the threshold as a result of gauge invariance. The t-channel K exchange contributes significantly, while the contributions from the t-channel exchange and s-channel nucleon exchange are ultimately negligible. The contributions from the s-channel exchange are found to be responsible for the bump structure shown in the CLAS total cross-section data above the center-of-mass energy GeV. The predictions of the differential cross sections for are presented and discussed, which can provide theoretical guidance for future experiments.

In our previous work [Phys. Rev. C 101, 014003 (2020)], the photoproduction reaction was investigated within an effective Lagrangian approach. The reaction amplitudes were constructed by including the t-channel K, , and κ exchanges, u-channel Λ, Σ, and exchanges, s-channel N, , and exchanges, and interaction current. The data on the differential cross sections and spin density matrix elements were described simultaneously. In this study, we investigate the photoproduction reaction based on the same reaction mechanism as that of to obtain a unified description of the data for and within the same model. All hadronic coupling constants, form factor cutoffs, and the resonance masses and widths in the present calculations remain the same as in our previous work for . The available differential cross-section data for are well reproduced. Further analysis shows that the cross sections of are dominated by the contributions of the t-channel K exchange, while the s-channel and exchanges also provide considerable contributions.

In this work, graphene quantum dots (GQDs) were synthesized by femtosecond laser ablation in liquid using laser induced graphene as the carbon source. Nitrogen-doped graphene quantum dots (N-GQDs) were successfully synthesized by adding ammonia water to the graphene suspension. The GQDs/N-GQDs structure consist of a graphitic core with oxygen and nitrogen functionalities with particle size less than 10 nm, as demonstrated by x-ray photoelectron spectroscopy, Fourier infrared spectrometer spectroscopy, and transmission electron microscopy. The absorption peak, PL spectrum, and quantum yield of the N-GQDs were significantly enhanced compared with the undoped GQDs. Further, the possible mechanism of synthesis GQDs was discussed. Furthermore, the N-GQDs were used as a fluorescent probe for detection of Fe3+ ions. The N-GQDs may extend the application of graphene-based materials to bioimaging, sensor, and photoelectronic.

Recently, Nb3O7F (NOF) semiconductor has been intensively studied owing to its excellent ultraviolet activity, good thermal stability and low carrier recombination. In this work, we report a five-step technique to synthesize hollow carbon spheres (HCSs)/NOF hybrids. Activating the surface of HCSs by creating oxyfluorinated functionalization can easily trigger an interaction between oxyfluorinated HCSs and NOF intermediates, finally resulting in the formation of HCSs/NOF hybrids. By manipulating the contents of HCSs with unexceptionable electron mobility, the hybrids can simultaneously achieve narrower band gap, stronger light absorption and rapider charge transfer. As a consequence, HCSs/NOF hybrids exhibit enhanced photodegradation performance towards RhB solutions under simulated sunlight irradiation. Specially, HCSs/NOF-1.0 catalysts with 95.7% degradation efficiency within 40 min demonstrate approximately four times higher photocatalytic activity than that of pure NOF catalysts. The results may offer new inspirations for a design of novel catalysts with higher photoactivity.

This study investigated the effect of recrystallization before austenitizing transformation (i.e., pre-recrystallization) on the microstructure and properties of 22Mn2Cr cold-rolled automotive steel sheets based on continuous annealing at 700 °C for various holding times. Subsequently, the samples were heated to an austenitizing temperature of ∼850 °C, which led to the formation of a fine austenite grains via nucleation at the dislocations during reheating. The austenite grain size was more refined when samples were pre-recrystallized at 700 °C for several minutes compared to those directly heated to 850 °C, which was attributed to combined grain refinement from recrystallization and austenite phase transformation. This refined austenite grain size led to a finer bainite grain size in the cooled final product. The strength of the steel decreased slightly (∼1200 MPa), but the elongation (∼19%) and product of strength and elongation (∼23 GPa%) were significantly enhanced by the pre-recrystallization treatment.

The vision SLAM technology is the key technology of robot navigation and unmanned driving. In order to further study the accuracy of multi-view SLAM positioning and mapping applications, this paper combines omnidirectional imaging and SLAM technology, improves the existing technical model in the field of omnidirectional imaging, studies the pose map optimization and SLAM overall adjustment technology based on object constraints and global consistency, and carries out omnidirectional SLAM point cloud reconstruction and 3D mapping. Through the time synchronization experiment of Ladybug 5 Plus and Femtomes Mini2-D-INS, the two positioning results of the system and the GNSS measurement results are compared and analysed.

Taking a two-stage supply chain model of a single manufacturer and a single retailer as the research object, this paper initially proposes the random demand function of retailers’ effort to establish an integrated supply chain model based on dual factors of retailer effort and selling price. Then it discusses how to optimize the reward and punishment contracts to realize the win-win situation of supply chain members under decentralized decision-making by analyzing the coordination and optimization of supply chain under centralized and decentralized conditions. Finally, the conclusion is verified by numerical simulation experiment, effort and quantity will decrease along with the increase of the distribution coefficient and will increase with the increase of the buy-back price’s coefficient.

The application of a light municipal system will become an essential means to improve cities’ total carrying capacity and realize the sustainable development of green ecology in urban and rural areas. The green technology system adopted by a light municipal system’s regional development model can reduce traditional municipal facilities development’s initial cost. The saved investment cost of early facilities is enough to offset the increased late green technology application cost. While the region realizes green development, the overall economy can also be fully guaranteed. This paper analyses the light municipal system’s applicable conditions to popularize and apply this technical system in a broader range.

The photorefractive effect is an effective way of achieving control of a beam by inducing a space-charge field and controlling the distribution of the refractive index. Herein, the one-dimensional gradient distribution of a space-charge field is structured, and the deflection of the transmitted beam is achieved. The method of regulation and control of the space-charge field was studied by digital holographic microscopy based on a Mn-doped KTN single crystal. The realized deflector has a maximum deflection angle of 0.3° and maintains good frequency-response characteristics up to 50 kHz. This work provides guidance for optical functional devices based on engineering distribution of a space-charge field.

As a crucial factor affecting water flooding in tight sandstone reservoirs, dynamic capillary pressure (DCP) has significant impact on the production performance during oil-water flow. In this work, a novel numerical simulation method with DCP is developed to study oil displacement in tight sandstone reservoirs. Based on this new model, the impacts from DCP to water/oil displacement (or water flooding effects) are analysed. The results of this work show that the effects brought by dynamic capillary pressure cannot be neglected. The more significant dynamic effects of capillary pressure correspond to the sample with lower permeability. The effect of DCP is probably a major contributor to non-linear flow (non-Darcy flow) in tight sandstone reservoirs during water flooding process. Compared with the conventional flow theory (e.g., static capillary pressure theory), our derived model with DCP can help to reduce the uncertainty in water/oil flow in tight sandstone reservoirs.

A 5.8 GHz Fabry-Perot resonator antenna is proposed to improve the performance of the spin rectification effect and inverse spin Hall effect in the far field region. A planar inverse F-shaped antenna and a metamaterial superstrate are used to increase the magnitude of the electromagnetic field. The microwave electric field is enhanced by ~10-fold, while the magnetic field is enhanced by ~80-fold. Experimental results prove that the dc signal from the spin rectification effect and inverse spin Hall effect is significantly improved. This letter paves the way for the use of spintronic devices in wireless excitation applications.

Sulfur vacancy in MoS2 has been found to have an important influence on the performance of optoelectronic devices. Here, we study the effect of sulfur vacancy and O2 adsorption on the electronic and optical properties in the two-dimensional ferroelectric CuInP2S6. It is revealed that a defect state appears at the top of valence band with the presence of sulfur vacancy. However, when O2 is chemisorbed at sulfur vacancy, the defect state disappears. The variation of charge state and charge transfer are calculated and discussed. Although the ferroelectricity is greatly suppressed with the presence of sulfur vacancy, the ferroelectric state can be recovered when the O2 is adsorbed. Within the framework of GW + BSE method, the optical absorption edge of CuInP2S6 monolayer exhibits a red-shift for the presence of sulfur vacancy and further O2 adsorption gives rise to a blue-shift of the spectrum. Our findings have shown an effective way to improve the functionality of two-dimensional ferroelectrics via defect engineering.

Novel trivalent europium (Eu3+)-doped niobium oxyfluoride (Nb3O7F) nanomaterials with retarded carrier recombination and enhanced photocatalytic activity were successfully synthesized by a facile hydrothermal method. Through changing the doping ratio of Eu3+ ions, the phase, composition, morphology, absorption spectra and photocatalytic properties were investigated in detail. The results showed that Eu3+ ions were successfully incorporated into the interstitial sites of Nb3O7F crystal lattice. With the increase of Eu3+ amounts, the morphology gradually changed from nanowall to irregular nanoparticle. Meanwhile, incorporation of Eu3+ ions had a slight influence on the light absorption. However, Eu3+-doped samples exhibited excellent photodegradation activity towards Rhodamine B dyes. The improvement may be ascribed to higher specific surface area, and lower carrier recombination prohibited by forming Eu3+/Eu2+ self-redox centers. This work envisages that Eu3+-doped Nb3O7F nanomaterials may be a promising kind of photocatalysts.

A two-phase-coexistence technique offers intriguing variables to maneuver novel and enhanced functionality in a single-component material. Most importantly, new band alignment and perfect interfaces between two phases can strongly affect local photoelectronic properties. However, previous efforts to achieve two-phase coexistence were mainly restricted to specific systems and methods. Here we demonstrate a phase-transition route to acquire two-phase-coexistence niobium oxyfluoride (Nb3O7F) nanocrystals for the first time. Based on key distinguishing features of the experimental results and theoretical analysis, the phase transition of Nb3O7F involves an organic/inorganic hybrid, heat treating, Al-doping, lattice deformation and structural rearrangement. The band gap can be effectively tuned from 3.03 eV to 2.84 eV, and the VBM can be tuned from 1.49 eV to 1.69 eV according to the phase proportion. Benefiting from uniform nanocrystal size, tunable band alignment and an optimized interfacial structure, the two-phase coexistence markedly enhances visible-light harvesting and the photocatalytic performance of Nb3O7F nanocrystals. The results not only demonstrate an opportunity to explore two-phase coexistence of novel nanocrystals, but also illustrate the role of two-phase coexistence in achieving enhanced photoelectronic properties.

We propose a scheme to implement quantum state transfer between two distant quantum nodes via a hybrid solid–optomechanical interface. The quantum state is encoded on the native superconducting qubit, and transferred to the microwave photon, then the optical photon successively, which afterwards is transmitted to the remote node by cavity leaking, and finally the quantum state is transferred to the remote superconducting qubit. The high efficiency of the state transfer is achieved by controllable Gaussian pulses sequence and numerically demonstrated with theoretically feasible parameters. Our scheme has the potential to implement unified quantum computing–communication–computing, and high fidelity of the microwave–optics–microwave transfer process of the quantum state.

Heavy charged gauge bosons are proposed in some theories beyond the standard model. We explore the discovery potential for W' -> t (b) over bar with top quark semi-leptonic decay at the LHC. We concentrate on the new physics signal search with the deviation from the standard model prediction if the resonance peak of W' cannot be observed directly. Signal events with two jets plus one charged lepton and missing energy are simulated, together with the dominant standard model backgrounds. In this paper, it is found that suitable cuts on the kinematic observables can effectively suppress the standard model backgrounds, so that it is possible to search for a W' signal at the LHC if its mass is less than 6.6 TeV.

The energies of the low-lying isoscalar and isovector configurations with spin-parity JP = 0+, 1+ and 2+ are calculated in a non-relativistic constituent quark model by using the variational method. The contributions of various parts of the quark?quark interacting potentials including the s-channel interaction are investigated, and the effect of different forms of the confinement potential is examined. The model parameters are determined by the same method as in our previous work, and they still can satisfactorily describe the nucleon?nucleon scattering phase shifts and the hyperon?nucleon cross sections. The parameters of the s-channel interaction are fixed by the masses of K and K* mesons, for which the size parameter is taken to be two possible values. When it is chosen to be the same as baryons', the numerical results show that the masses of all the configurations are higher than the corresponding meson?meson thresholds. But when the size parameter for the K and K* mesons is adjusted to be smaller than that for the baryons, the configuration with I = 0 and JP = 1+ is found to lie lower than the K*K* threshold, furthermore, this state has a very small KK* component and the interaction matrix elements between this state and KK* is comparatively small, thus its coupling to the KK* channel will consequently be weak and it might be regarded as a possible tetraquark candidate.

Some special Backlund transformation (BT) theorems and a particular nonlinear superposition theorem are established to find exact solutions for a non-integrable model, the (N+1)-dimensional 4 scalar field. Some new types of exact solutions such as the conoid periodic–periodic interaction waves and the periodic–solitary wave interaction solutions are explicitly given. The interaction solutions possess abundant structures, thanks to the intrusion of some arbitrary functions in the expressions of the special solutions.

The recent studies of the newly observed dibaryon resonance d*(2380) in a constituent chiral quark model are briefly summarized. An overall analysis of the obtained pionic decay widths, comparing with the experimental data, shows that a compact hexaquark system might be a reasonable interpretation for this dibaryon resonance with I(JP ) = 0(3+).

Coping with increasing environmental issues, niobium oxyfluoride (Nb3O7F), as a novel semiconductor, is a promising photocatalyst due to its outstanding electronic and optoelectronic properties. However, the photocatalytic performance of Nb3O7F is restricted in practical application due to its weak optical absorption and low carrier separation. In this work, Nb3O7F/WS2 hybrids with superior optical absorption and photocatalytic activity have been successfully synthesized by a facile two-step sol-hydrothermal technique. UV-vis spectra show that WS2 not only exhibits enhanced optical absorption in the range of 420-1100 nm but extends the absorption edge, and tends to narrow the band gap of the Nb3O7F photocatalyst. Photocatalytic experiments indicate that introducing WS2 into Nb3O7F markedly enhances the photocatalytic activity in the degradation of methylene blue dyes under visible-light irradiation. Nb3O7F/WS2 photocatalysts exhibit the highest activity with 98.9% decoloration efficiency in 70 min, while pure Nb3O7F only achieves 67.9% in the same time and achieves its final decoloration ratio after 150 min. The excellent photocatalytic activity can be directly ascribed to more exposed active sites, higher carrier separation efficiency, and faster carrier transfer. The results may open up a new avenue for the design and preparation of novel and highly efficient photocatalysts.

The comparison of networks with different orders strongly depends on the stability analysis of graph features in evolving systems. In this paper, we rigorously investigate the stability of the weighted spectral distribution (i.e., a spectral graph feature) as the network order increases. First, we use deterministic scale-free networks generated by a pseudo tree-like model to derive the precise formula of the spectral feature, and then analyze the stability of the spectral feature based on the precise formula. Except for the scale-free feature, the pseudo tree-like model exhibits the hierarchical and small-world structures of complex networks. The stability analysis is useful for the classification of networks with different orders and the similarity analysis of networks that may belong to the same evolving system.

Significant performance enhancement was observed for the bulk-heterojunction polymer solar cell of ITO/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′ -benzodithiazole)]:[6,6]-phenyl C71 butyric acid methyl ester (PCDTBT:PC71BM)/Al when the as-cast active layer was rinsed with methanol before the deposition of the metal electrode. Comparison of independent anode interfacial layers of PEDOT:PSS and MoO3 indicated that the effects of methanol treatment on the improvement of device performance are more pronounced for PEDOT:PSS-based devices. No discernible changes can be observed in film thickness, surface topography and UV–vis absorption profiles of the photoactive layer, indicating the absence of film reconstruction and the improvement of device performance are hence attributed to the modification of the interface between the PEDOT:PSS and the fresh active layer. Further examination of the devices containing a cathode interlayer of poly[(9,9-bis(3′-(N,N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9–dioctylfluorene)] (PFN) also demonstrates the potential modification of the interface between the PEDOT:PSS and the active layer by methanol in addition to the widely observed PFN functionality.