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With the purpose of investigating the effects of geometry parameters of CFJ (Coflow jet) device on the aerodynamic characteristics of the supercritical bacj airfoil used by a STOL transport, we have carried out a computational analysis of CFJ airfoil with different values of injection slot size and location under the low-speed condition. The results show that the lift coefficient decreases gradually with decreasing stall angle, when the injection slot size is increased. When α=8°, with increasing injection slot size, the velocity of blowing jet decreases with decreasing power consumption and increasing aerodynamic effectiveness. Further, with the injection slot shifted towards the downstream direction, the α value corresponding to the maximum effective lift-drag-ratio increases with increasing maximum lift coefficient.

In the context of Rastall gravity, the shadow and observation intensity casted by the new Kiselev-like black hole with dust field have been numerically investigated. In this system, the Rastall parameter and surrounding dust field structure parameter have considerable consequences on the geometric structure of spacetime. Considering the photon trajectories near the black hole, we investigate the variation of the radii of photon sphere, event horizon and black hole shadow under the different related parameters. Furthermore, taking into account two different spherically symmetric accretion models as the only background light source, we also studied the observed luminosity and intensity of black holes. For the both spherical accretions background, the results show that the decrease or increase of the observed luminosity depends on the value range of relevant parameters, and the promotion effect is far less obvious than the attenuation effect on the observed intensity. One can find that the inner shadow region and outer bright region of the black hole wrapped by infalling accretion are significantly darker than those of the static model, which is closely related to the Doppler effect. In addition, the size of the shadow and the position of the photon sphere are always the same in the two accretion models, which means that the black hole shadow depend only on the geometry of spacetime, while the observation luminosity is affected by the form of accretion material and the related spacetime structure.

In this paper, we study the shadows and observational appearance of the Ayón-Beato-García (ABG) black hole, which is surrounded by a thin disk accretion. For a four-dimensional ABG black hole, as the charge q increases, the event horizon r +, radius r p and impact parameter b p of the photon sphere decrease, while the maximum value of effective potential V eff increases. However, as the term γ associated with nonlinear electrodynamics increases, the related physical quantities r +, r p and b p increase, but the maximum value of V eff decreases. When the light ray reaches the vicinity of the ABG black hole, one can observe the trajectories of the light rays appearing as three types, i.e., direct emission, lens ring and photon ring. Furthermore, the shadows and the observational appearance of the ABG black hole are studied. The results show that the charge q and the term γ have a great influence on the shape and intensity of the black hole shadow. When the relevant state parameters change or the emission model changes, it can be argued that it is the direct emission that plays a decisive role in the total observed intensity of the ABG black hole, while the contribution of the lens ring to the total observed intensity is small and the photon ring makes almost no contribution.

Sagittarius A* (SgrA*) lying in the Galactic Centre $8$ kpc from Earth, hosts the closest supermassive black hole known to us. It is now inactive, but there is evidence indicating that about six million years ago it underwent a powerful outburst where the luminosity could have approached the Eddington limit. Motivated by the fact that in extragalaxies the supermassive black holes with similar masses and near-Eddington luminosities are usually strong X-ray emitters, we calculate here the X-ray luminosity of SgrA*. For that, we assume that the outburst was due to accretion of gas or the tidal disruption of a star. We show that these cases could precipitate on Earth a hard X-ray (i.e. $h\nu>2~{\rm keV}$) flux comparable to that from the current quiescent sun. The flux in harder energy band $20~{\rm keV}, Comment: Minor changes, accepted for publication

With the development of global aviation industry, a huge international airline network has been formed. In order to solve the problem that the connecting path search method takes long time in global airline network, the objective of this paper is to find out all the target connecting flights paths fast between an OD pair. According to the features of the connecting path search in the schedule-based network, the solving method is divided into three stages. In the first stage, we build a time-space graph. In the next stage, three-step cutting is used to reduce the scale of graph. After that, we apply an algorithm which is combined with depth-first and breadth-first search algorithm to enumerate the paths. It can be seen that our algorithm is suitable for multi-constraints, big data and searching all paths.

Transient electronics is an emerging technology that enables unique functional transformation or the physical disappearance of electronic devices, and is attracting increasing attention for potential applications in data secured hardware as an ultimate solution against data breaches. Developing smart triggered degradation modalities of silicon (Si) remain the key challenge to achieve advanced non-recoverable on-demand transient electronics. Here, we present a novel electrochemically triggered transience mechanism of Si by lithiation, allowing complete and controllable destruction of Si devices. The depth and microstructure of the lithiation-affected zone over time is investigated in detail and the results suggest a few hours of lithiation is sufficient to create microcracks and significantly promote lithium penetration. Finite element models are proposed to confirm the mechanism. Electrochemically triggered degradation of thin film Si ribbons and Si integrated circuit chips with metal-oxide-semiconductor field-effect transistors from a commercial 0.35 micrometer complementary metal-oxide-semiconductor technology node is performed to demonstrate the potential applications for commercial electronics. This work opens new opportunities for versatile triggered transience of Si-based devices for critical secured information systems and green consumer electronics.

ZnO nanowires deposited on Si substrates were prepared by thermal evaporation of a mixture of ZnO and carbon powder. Ag ions with an energy of 63 keV and a dose of 5 × 1015 ions/cm2 were implanted into the as-prepared ZnO nanowires. After ion implantation, the Ag-implanted ZnO nanowires were annealed in air at different temperatures from 600°C to 1000°C. Effects of ion implantation and thermal annealing on the structural and photoluminescent (PL) properties of the ZnO nanowires were investigated by transmission electron microscopy (TEM), selected area energy dispersive X-ray spectroscopy (SAEDX), X-ray diffraction (XRD), and fluorescence spectrophotometry. TEM, HR-TEM, and SAEDX analyses demonstrated that efficient doping of Ag was achieved by ion implantation and the subsequent annealing process. XRD patterns revealed that the hexagonal wurtzite structure of ZnO nanowires was maintained after ion implantation. Photoluminescent emissions of ZnO nanowires were decreased significantly by Ag implantation but could be recovered by thermal annealing. The mechanism of the influence of ion implantation and annealing on the PL intensity was assessed.

In order to study the effect of M substitution of transition elements on the structural properties of R2Co7?xMxB3 (R = Y, Gd; M = Ti, V, Cr) compounds, the phase stability and site preference are performed by using the pair potentials based on the lattice inversion technique. In R2Co7?xMxB3, M atoms substitute for Co with a strong preference for the 6i1 sites and the order of site preference is 6i1, 2c and 6i2. Calculated lattice parameters are in good agreement with the experimental data. Moreover, the total and partial phonon densities of states are first evaluated for the R2Co7B3 compounds with the hexagonal Ce2Co7B3-type structure.

This paper investigates the properties of dislocations in Pd/MgO(001) interfaces. By constructing ideal and virtual interface structures and applying the Chen–Mobius inversion method, we obtain interatomic potentials ΦPd–Mg and ΦPd–O directly from ab initio adhesive energies. Then, by applying the above potentials, as well as using the atomistic relaxation and molecular dynamics methods, stable interface structures are obtained. For simplicity, we use a two-dimensional model to provide some clear physical pictures of the dislocations. There are two kinds of mechanisms of dislocation formation: one is insertion of an extra slice of Pd atoms; the other is increasing the number of Pd layers, to produce dislocations via the increasing misfit stress. Finally, three-dimensional models are investigated, with dislocations perpendicularly intersecting in the interface. The calculated interfacial distances are in agreement with experiments.

A systemic study of the structural properties of Pr(Fe, M)12 and Pr(Fe, M)12Nx (M = Ti, V, Cr, Mo) compounds has been performed by a series of interatomic pair potentials obtained through the lattice inversion method. Adding a ternary element Ti, V, Cr or Mo makes the crystal cohesive energy of Pr(Fe, M)12 decrease markedly, which indicates that Ti, V, Cr or Mo helps stabilize the crystal structure. The calculated preferentially occupation site of the stabilizing element M is found to be the 8i site. The interstitial N atoms only occupy 2b interstitial sites in Pr(Fe, M)12. The calculated results correspond well to available experimental data. The method utilized in the present investigation provides an effective approach to predict different properties of Pr(Fe, M)12 and Pr(Fe, M)12Nx.

We have simulated the structural and vibrational properties of NdMn8T4 compounds (T = Fe, Co, Ni), using the inverted pair potentials ΦMn–Mn(r), ΦNd–Mn(r), ΦNd–R(r), ΦNd–T(r), ΦMn–T(r), and ΦT–T(r). The calculated site preference of the third element, T, is found to be the 8f site. The difference in the lattice parameters between the calculated and the experimental values is less than 3.0%. These results are in agreement with experiments. Moreover, the total and partial phonon densities of states are first evaluated for the NdMn8T4 compounds. A qualitative analysis is carried out with the relevant potentials for the vibrational modes, which makes it possible to predict some properties related to lattice vibration.

A concise and general formula is introduced to obtain ab initio pair potentials between atoms across a metal–ceramic interface by inversion of the adhesive energies of the interface. Derivation of interfacial potentials ΦAg−Mg and ΦAg−O from ab initio adhesive energies is performed by applying the formula to the Ag/MgO(001) interface. Transferability of these potentials at Ag/MgO(100), Ag/MgO(110) and Ag/MgO(111) interfaces is discussed.

The phase stability and site preference of the intermetallics R3(Fe,T)29 (R = Nd,Gd,Y; T = Ta,W) with Nd3(Fe,Ti)29 structure have been investigated by lattice inversion potentials. The calculated results indicate that each of the stabilizing elements Ta and W significantly decreases the cohesive energy of R3(Fe,T)29 and plays a role in stabilizing the 3:29 structure. Among the 11 different kinds of Fe sites in these compounds the preferential sites of Ta and W are 4i3, 4i4 and 4g sites. The calculated lattice parameters of R3(Fe,T)29 compounds are in good agreement with the experimental data. The structural stability of the R3(Fe,T)29 compounds is further tested at different temperatures. Based on the pair potential curves an intuitive explanation for the phase stability and solubility is made.

Based on the inverted quasi-ab initio pair potentials, the phase stability and site preference of R2Co17?xMnx (R = Nd, Sm, Gd) intermetallics with a rhombohedral Th2Zn17-type structure are studied. In the calculations, the crystal binding energy of R2Co17?xMnx decreases with increasing Mn concentration, proving that Mn atoms are beneficial to the phase stability of R2Co17?xMnx. The calculated preferential occupation site of the stabilizing element Mn is found to be the 6c site, which accords with the experiments. Qualitative analyses are carried out on the behaviour of the Curie temperature and magnetocrystalline anisotropy. All the results indicate that the pair potentials based on the lattice inversion method can effectively give a deeper insight into the structure and property of complex materials.

The compounds Nd2Co17−xVx and (Nd1−xErx)2Co15.5V1.5 with the rhombohedral Th2Zn17-type structure have been simulated by using a series of quasi-ab initio inter-atomic potentials. The computed lattice constants of Nd2Co17−xVx and (Nd1−xErx)2Co15.5V1.5 are in good agreement with experiment. The site preference of V atoms is also evaluated and the order is found to be 6c, 18f, 18h and 9d, and the decrease of the Curie temperature of Nd2Co17−xVx with increasing concentration of V is explained qualitatively. All the above results indicate that the inter-atomic potentials are valid for studying the structural properties of these kinds of anisotropic materials.

Based on the inversion pair potentials, the molecular dynamics simulations were performed to study the pressure-induced B1–B2 phase transition in NaCl crystal. Under a transition pressure close to the experimental value, it is found at the temperature of 600 K that there is a transformation from the six-fold coordinated B1 structure to the eight-fold coordinated B2 phase. But at the same temperature, the reversible transformation B2–B1 was presented under zero pressure by the same interionic potentials. These are in good agreement with the experimental observations. The atomistic mechanism of the phase transition was discussed in terms of the configurations under different pressures.

The thermal expansion coefficients of LaFe11.7Si1.3 from 85 to 413 K are studied. The volume expands significantly at the Curie temperature 188 K when it changes from the paramagnetic to the ferromagnetic state. The crystallographic structures at 85 and 298 K were determined, and no evidence of a structural transition was found. The thermal expansion coefficients are near constants when the temperature is about 40 K higher or lower than the Curie temperature. From 85 to 143 K, the thermal expansion coefficient is about 3.61(+/-0.26) x 10(-6) K-1, and from 233 to 413 K, it is about 1.17(+/-0.04) x 10(-5) K-1. From 153 to 213 K, the negative nonlinear expansion coefficients are related to the metallic magnetism.

By using the interatomic pair potential obtained with the lattice inversion method, the stability of RT13-xMx (R = La, Ce, Pr and Nd; T = Co and Fe; M = Si, Al, Cr, V and Ti) of the NaZn13 type and its derivative structure are studied. The structural transition of LaT13-xSix (T = Co and Fe) between the cubic one with the space group Fm3c and the tetragonal one with 14/mcm is imitated from the viewpoint of energy. As for the function of the third elements, Al and Si are beneficial to the phase stability of RT13-xMx, whereas Cr, Ti and V are unfavourable to the stability. In the calculation, the range of x, with which RT13-xMx could crystallize in the cubic or tetragonal structures, agrees with the experiments very well. The calculated crystallographic parameters coincide with the experimental observation. In the cubic structure, Si and Al prefer the 96i site, and in the tetragonal structure Si first occupy the 16l(2) site, then the 16k site. In addition, all the site positions of the compounds with either the cubic or tetragonal structure are really congruent with the experimental one.

Pair potentials based on ab initio calculation are used to simulate the structural properties of R2Fe17 (R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu). The calculated lattice constants of R2Fe17 (R=Ce, Pr, Nd, Sm) with Th2Zn17 structure and R2Fe17 (R=Y, Ho, Er, Tm, Lu) with Th2Ni17 structure are in good agreement with experiment. The site preference of N atoms in Nd2Fe17 and the structure of Nd2Fe17Nx are close to experimental results. Simultaneously, the increase of the Curie temperature of Nd2Fe17Nx with N is explained qualitatively by the exchange interaction model. All the above results indicate that simple pair potentials are valid for studying the structural properties of these kinds of anisotropy materials and some related nitrides.

Metamaterial-based absorbers play a significant role in applications ranging from energy harvesting and thermal emitters to sensors and imaging devices. The middle dielectric layer of conventional metamaterial absorbers has always been solid. Researchers could not detect the near field distribution in this layer or utilize it effectively. Here, we use anisotropic liquid crystal as the dielectric layer to realize electrically fast tunable terahertz metamaterial absorbers. We demonstrate strong, position-dependent terahertz near-field enhancement with sub-wavelength resolution inside the metamaterial absorber. We measure the terahertz far-field absorption as the driving voltage increases. By combining experimental results with liquid crystal simulations, we verify the near-field distribution in the middle layer indirectly and bridge the near-field and far-field observations. Our work opens new opportunities for creating high-performance, fast, tunable, terahertz metamaterial devices that can be applied in biological imaging and sensing.

Elastic constants have been calculated for the FCC metals Cu, Al and Ni using the Mobius transform and a short-range three-body potential correction. Unlike a previous calculation based only on pair potentials, the result is in good agreement with experiment since the restriction of the Cauchy relation has been removed. More importantly, it shows the potential application of the Mobius-inversion method for evaluating interatomic potentials from ab initio electronic structure calculations.

We herein review our studies on simulating the thermal unfolding Fourier transform infrared and two-dimensional infrared spectra of peptides. The peptide‐water configuration ensembles, required forspectrum modeling, aregenerated at a series of temperatures using the GB OBC implicit solvent model and the integrated tempering sampling technique. The fluctuating vibrational Hamiltonians of the amide I vibrational band are constructed using the Frenkel exciton model. The signals are calculated using nonlinear exciton propagation. The simulated spectral features such as the intensity and ellipticity are consistent with the experimental observations. Comparing the signals for two beta-hairpin polypeptides with similar structures suggests that this technique is sensitive to peptide folding landscapes.

The present work reports on a feasibility study commissioned by the Chinese Academy of Sciences of China to explore various possible mission options to detect gravitational waves in space alternative to that of the eLISA/LISA mission concept. Based on the relative merits assigned to science and technological viability, a few representative mission options descoped from the ALIA mission are considered. A semi-analytic Monte Carlo simulation is carried out to understand the cosmic black hole merger histories starting from intermediate mass black holes at high redshift as well as the possible scientific merits of the mission options considered in probing the light seed black holes and their coevolution with galaxies in early Universe. The study indicates that, by choosing the armlength of the interferometer to be three million kilometers and shifting the sensitivity floor to around one-hundredth Hz, together with a very moderate improvement on the position noise budget, there are certain mission options capable of exploring light seed, intermediate mass black hole binaries at high redshift that are not readily accessible to eLISA/LISA, and yet the technological requirements seem to within reach in the next few decades for China.

In this letter, a new recursive algorithm to implement phase retrieval from two intensities in the two-dimensional Fourier transform domain is presented. In terms of the cascading property and additivity of the order of the fractional Fourier transform, a set of convolution equations is exactly derived. Applying recursive algorithm, these equations can be easily solved. This approach simplifies significantly computational manipulations comparing with conventional iterative algorithms and does not need initial phase distribution.

The structure properties of the ternary hydrides Ni3AlHx are studied by use of the interatomic pair potentials obtained from the first principles electronic structure calculation and Chen-Mobius 3-dimensional lattice inversion method. The heat of formation and volume expansion of the hydrogenized systems are investigated.

By using the Hardy-Wright-M?bius inverse formula, we have improved the Carlsson-Gelatt-Ehrenreich scheme for the inverse problem of cohesive energy. The advantage of the new method is that the inverse formula are in a sense independent of the geometries of lattices.

The lattice-inversion embedded-atom-method interatomic potential developed previously by us is extended to alkaline metals including Li, Na, and K. It is found that considering interatomic interactions between neighboring atoms of an appropriate distance is a matter of great significance in constructing accurate embedded-atom-method interatomic potentials, especially for the prediction of surface energy. The lattice-inversion embedded-atom-method interatomic potentials for Li, Na, and K are successfully constructed by taking the fourth-neighbor atoms into consideration. These angular-independent potentials markedly promote the accuracy of predicted surface energies, which agree well with experimental results. In addition, the predicted structural stability, elastic constants, formation and migration energies of vacancy, and activation energy of vacancy diffusion are in good agreement with available experimental data and first-principles calculations, and the equilibrium condition is satisfied.

The differences in structural change between Au225 and Au369 clusters with their (111) facets supported on MgO(100) surfaces at 5 K are studied by using molecular-dynamics simulations with the atomic interchange potentials of the Au/MgO interface. The parameters are obtained from the ab initio energies using the Chen—Mobius inversion method. Analyses of the pair distribution functions show that the two Au clusters use different deformation processes to adjust the distances between the interface atoms, owing to the misfit between the atom distances among the clusters and the substrates. The local structural changes are identified by atomic density profiles.

The lattice-inversion embedded-atom-method (LI-EAM) interatomic potential we developed previously [J. Phys.: Condens. Matter 22 (2010) 375503] is extended to group-VA transition metals (V, Nb and Ta). It is found that considering interatomic interactions up to appropriate-distance-neighbor atoms is crucial to constructing accurate EAM potentials, especially for the prediction of surface energy. The LI-EAM interatomic potentials for group-VA transition metals are successfully built by considering interatomic interactions up to the fifth neighbor atoms. These angular-independent potentials drastically promote the accuracy of the predicted surface energies, which match the experimental results well.

The atomic and electronic structures of Pb bilayer/Pt(111) are investigated with two theoretical calculations. We find that the stable (2 × 2)/(3 × 3) Pb/Pt(111) structure is a promising candidate for being used as a template with self-organized ordered Pb semi-cluster array on the first Pb monolayer. This stable structure can realize the ordered Au single-atom array around the Pb semi-clusters that can cause selective adsorption of noble atoms. The size of Pb magic number semi-cluster plays a more important role in determining the periodicity of the template than the lattice constant misfit between the substrate and the overlayer. This leads to quite a different periodicity between the two stable templates, which are (2 × 2)/(3 × 3) Pb/Pt(111) and Pb/Cu(111). Therefore, by considering the size of the stable semi-clusters and carefully selecting different substrate materials, we can tune the density of Pb semi-clusters as the nucleation points and then tune the periodicity of the stable template.

Photoacoustic tomography has the potential to image the configuration or function of animal or human organs with simultaneous high contrast and high spatial resolution. This article provides an overview of photoacoustic tomography with an acoustic lens. And a new fast photoacoustic tomography technique is introduced. An acoustic lens is able to map the initial photoacoustic pressure distribution in an object in real time without the need of complicated computational reconstruction. Further more, this method produces no artifacts in reconstructed images. Finally, a new fast photoacoustic tomography system based on acoustic is discussed in detail in this paper.

An interface has some special features in a fracture because of its misfit dislocations. In this work, we use ab initio-based interatomic potentials to study this problem in a Pt/SiC(1 1 1) interface. The whole dynamic process is simulated in the atomistic scale. Micro-cracks and jump points are found in the fracture, which lead to some interesting results.

The interatomic potentials across metal/SiC(111) interfaces are derived from ab initio adhesive energies by an inversion method. We use these potentials to investigate the structures, energies and Burgers vectors of misfit dislocations in metal/SiC(111) interfaces. Two kinds of interfacial dislocations are found in M/SiC(111) (M = Au, Ag, Al, Pt) interfaces, where the M/SiC(111) (M = Au, Al) system has partial dislocations and the M/SiC(111) (M = Ag, Pt) system has perfect dislocations. The former has a coherent interface while the latter corresponds to a semi-coherent interface.

In order to study the effect of transition element M substitution on the structural properties of UCu3M2Al7 and UCu4MAl7 (M = Cr, Mn and Fe) compounds, the structural properties are investigated using the pair potentials based on the lattice inversion technique. The calculated lattice constants are found to be in good agreement with the experimental values. The properties related to lattice vibration, such as the phonon density of states, specific heat and vibrational entropy, are also evaluated. This is an attempt to predict the structural and thermodynamic properties for actinide materials with a complex structure.

Misfit dislocation is an important component of the semi-coherent interface. Usually, it forms a dislocation network as the strain concentration area on an interface and makes the other part coherent. This is the regular case, but there are also some exceptions. In this work, we show that the Ni/(Al2O3)Al interface has a reconstruction at the first monolayer of the metal side, which works as a transition layer between Ni and Al2O3 lattices. Under these conditions, the misfit dislocation cannot be confirmed by drawing a Burgers circuit because the interface is incoherent. However, due to the lattice misfit, there are areas of strain concentration and areas without strain distributed on the interface plane. So, for describing this strain distribution, we again use the concept of a dislocation network but redefine it as the separate line between these two parts. As a result, we find that the dislocation network appears when the metal part is thicker than 12.4 A, and it shrinks as the metal film grows, resulting in an ultimate structure with a mesh size of 28.1 A.

Wurtzite (B4) compounds commonly undergo a structural transition to the rocksalt (B1) phase under high pressure. The underlying transition mechanism, or the so-called transition path, has been extensively investigated in recent years. Two different transition paths have been proposed for the B4-B1 phase transition, that is the 'hexagonal' path and the 'tetragonal' path. In this work, taking zinc oxide (ZnO) as an example, we have made a comparative study of these two paths from first-principles. The calculated results lead to the conclusion that the tetragonal path is more favourable under lower pressure but the hexagonal path is more favourable under higher pressure, which indicates a competition between these two paths in the ZnO case. We have also investigated the evolution of structural and electronic properties along the two different paths; the axial ratio c/a is suggested as a good indicator in experiments to identify the transition path.