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In the biological locomotion, the ambit pressure is of particular importance to use as a means of propulsion. The multiple vortex rings have been proved to generate additional thrust by interaction, but the mechanism of this thrust enhancement is still unknown. This study examines the effect of ambit pressure on formation enhancement in interacting dual vortex rings. The vortex rings, which have the same formation time, are successively generated in a piston-cylinder apparatus. The finite-time Lyapunov exponent (FTLE) visualizes the flow fields as an indication of Lagrangian coherent structures (LCSs), and the pressure field is calculated based on the digital particle image velocity (DPIV). We extract the back pressure of the rear vortex in dual vortices and the back pressure circulation Γ b, which is defined as a form of overpressure circulation Γ p. The Γ b has a positive linear relationship with Γ p. A critical interval distance d cr * in a range of 0.32–0.42 is found where Γ b and Γ p reach the maximum synchronously, leading to a full-interaction mode. Moreover, an over-interaction mode and an under-interaction mode are proposed when the dimensionless interval distance d* is smaller or larger than d cr * . To conclude, the high back pressure caused by vortex interaction can enhance the formation of vortex rings and lead to high thrust.

The [001] c -polarized (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN−PT) single crystals are widely used in ultrasonic detection transducers and underwater acoustic sensors. However, the relatively small coercive field (∼ 2 kV/cm) of such crystals restricts their application at high frequencies because the driving field will exceed the coercive field. The depolarization field can be considerably larger in an antiparallel direction than in a parallel direction with respect to polarization when the bipolar driving cycle starts. Thus, if the direction of the sine wave signal in the first half cycle is opposite to the polarization direction, then the depolarized domains can be repolarized in the second half of the sine cycle. However, if the direction of the sine wave signal in the first half of the cycle is along the polarization direction, then the change is negligible, and the domains switched in the second half of the sine cycle cannot be recovered. The design of electric driving method needs to allow the use of a large applied field to emit strong enough signals and produce good images. This phenomenon combined with the coercive field increases with the driving frequency, thereby making the PMN−PT single crystals usable for high-frequency applications. As such, the applied field can be considerably larger than the conventionally defined coercive field.

This paper calculates the elastic, thermodynamic and electronic properties of pyrite (Pa) RuO2 by the plane-wave pseudopotential density functional theory (DFT) method. The lattice parameters, normalized elastic constants, Cauchy pressure, brittle–ductile relations, heat capacity and Debye temperature are successfully obtained. The Murnaghan equation of state shows that pyrite RuO2 is a potential superhard material. Internal coordinate parameter increases with pressure, which disagrees with experimental data. An analysis based on electronic structure and the pseudogap reveals that the bonding nature in RuO2 is a combination of covalent, ionic and metallic bonding. A study of the elastic properties indicates that the pyrite phase is isotropic under usual conditions. The relationship between brittleness and ductility shows that pyrite RuO2 behaves in a ductile matter at zero pressure and the degree of ductility increases with pressure.

This paper constructs the interaction potential of the SH(X2∏) radical by using the coupled-cluster singles-doubles-approximate-triples theory combining the correlation-consistent quintuple basis set augmented with the diffuse functions, aug-cc-pV5Z, in the valence range. Employing the potential, it accurately determines the spectroscopic parameters. The present De, Re, ωe, ωeχe, αe and Be values are of 3.7767eV, 0.13424 nm, 2699.846 cm−1, 47.7055cm−1, 0.2639cm−1 and 9.4414cm−1, respectively, which are in excellent agreement with those obtained from the measurements. A total of 19 vibrational states has been found when J = 0 by solving the radial Schrodinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which are in good accord with the experimental results. The total and various partial-wave cross sections are computed for the elastic collisions of sulfur and hydrogen in their ground states at low temperatures when two atoms approach each other along the SH(X2∏) potential energy curve. Over the impact energy range from l.0 × 10−11 to 1.0 × 10−4 a.u., eight shape resonances have been found in the total elastic cross sections. For each shape resonance, the resonant energy is accurately calculated. Careful investigations have pointed out that these resonances result from the l = 0, 1, 2, 3, 4, 6, 7, 8 partial-wave contributions.

The anisotropic potential developed in our previous research and the close-coupling method are applied to the HBr-3 He (4 He, 5 He, 6 He, 7 He) system, and the partial cross sections (PCSs) at the incident energy of 60 meV are calculated. Based on the calculations, the influences of the isotope helium atom on PCSs are discussed in detail. The results show that the excitation PCSs converge faster than the elastic PCSs for the collision energy and the systems considered here. Also the excitation PCSs converge more rapidly for the high-excited states. The tail effect is present only in elastic scattering and low-excited states but not in high-excited states. With the increase of reduced mass of the collision system, the converging speed of the elastic and excitation PCSs slows down, and the tail effect goes up.

This paper reports that the interaction potential for the X3Σ− state of NH radical is constructed at the CCSD(T)/cc-PV6Z level of theory. Using this potential, this paper calculates the spectroscopic parameters (De, Re, ωe, ωeχe, αe and Be) and their values are of 3.578eV, 0.10368 nm, 3286.833cm−1, 78.433cm−1, 0.6469cm−1 and 16.6735cm−1, respectively, which are in excellent agreement with the experiments. Then the total of 14 vibrational states has been found when J = 0 by solving the radial Schrodinger equation of nuclear motion. For each vibrational state, the vibrational manifolds are reported for the first time. And last, the total cross sections, s-wave, p-wave and d-wave cross sections are computed for the elastic collisions between two ground-state atoms (hydrogen and nitrogen) at low temperatures. It finds that the total elastic cross sections are dominated by s-wave scattering when the collision energy is below 10−6 a.u. The pronounced shape resonance is found at energy of 6.1 × 10−6 a.u. Calculations have shown that the shape resonance comes from the p-wave contributions.

The splitting of potential energy levels for ground state X2∏g of Ox2 (x = +1, −1) under spin—orbit coupling (SOC) has been calculated by using the spin-orbit (SO) multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT). Their Murrell–Sorbie (M–S) potential functions are gained, and then the spectroscopic constants for electronic states 2∏1/2 and 2∏3/2 are derived from the M–S function. The vertical excitation energies for Ox2 (x = +1, −1) are v[O+12 (2∏3/2 → X2∏1/2)] = 195.652cm−1, and v[O−12(2∏1/2 → X2∏3/2)] = 182.568cm−1, respectively. All the spectroscopic data for electronic states 2∏1/2 and 2∏3/2 are given for the first time.

The total internal partition sums were calculated in the product approximation at temperatures up to 5000 K for the asymptotic asymmetric-top HO2 molecule. The calculations of the rotational partition function and the vibrational partition function were carried out with the rigid-top model and in the harmonic oscillator approximation, respectively. Our values of the total internal partition sums are consistent with the data of HITRAN database with -0.14% at 296 K. Using the calculated partition functions, we have calculated the line intensities of v2 band of HO2 at several high temperatures. The results showed that the calculated line intensities are in very good agreement with those of HITRAN database at temperatures up to 3000 K, which provides a strong support for the calculations of partition functions and line intensities at high temperatures. Then we have extended the calculation to higher temperatures. The simulated spectra of v2 band of the asymptotic asymmetric-top HO2 molecule at 4000 and 5000K are also obtained.

We investigate the conductivity characteristics in the surface accumulation layer of a junctionless nanowire transistor fabricated by the femtosecond laser lithography on a heavily n-doped silicon-on-insulator wafer. The conductivity of the accumulation region is totally suppressed when the gate voltage is more positive than the flatband voltage. The extracted low field electron mobility in the accumulation layer is estimated to be 1.25 cm2V−1s−1. A time-dependent drain current measured at 6 K predicts the existence of a complex trap state at the Si–SiO2 interface within the bandgap. The suppressed drain current and comparable low electron mobility of the accumulation layer can be well described by the large Coulomb scattering arising from the presence of a large density of interface charged traps. The effects of charge trapping and the scattering at interface states become the main reasons for mobility reduction for electrons in the accumulation region.

The energy term corresponding to the first order of the strain in Taylor series expansion of the energy with respect to strain is always ignored when high-pressure elastic constants are calculated. Whether the modus operandi would affect the results of the high-pressure elastic constants is still unsolved. To clarify this query, we calculate the high-pressure elastic constants of tantalum and rhenium when the energy term mentioned above is considered and neglected, respectively. Results show that the neglect of the energy term corresponding to the first order of the strain indeed would influence the veracity of the high-pressure elastic constants, and this influence becomes larger with pressure increasing. Therefore, the energy term corresponding to the first-order of the strain should be considered when the high-pressure elastic constants are calculated.

In this paper, we investigate the optical transmission properties of perfect and defective two-segment-connected triangular waveguide networks (2SCTWNs) and find that after introducing defects in networks, many groups of transparent extreme narrow photonic passbands (ENPPs) will be created in the middle of the transmission spectra, the number for each group and the group number of ENPPs can be adjusted by the matching ratios of waveguide length (MRWLs), the number of defects, and the number of unit cells of 2SCTWNs. The influences of MRWL, number of defects, and number of unit cells on the number, width, and position of these ENPPs are researched and a series of quantitative rules and properties are obtained. It may be useful for the designing of high-sensitive optical switches, wavelength division multiplexers, extreme-narrowband filters, and other correlative waveguide network devices.

In this paper, by means of the network equation and generalized dimensionless Floquet—Bloch theorem, we study the influences of the number of connected waveguide segments (NCWS) between adjacent nodes and the matching ratio of waveguide length (MRWL) on the photonic bands generated by quadrangular multiconnected networks (QMNs), and obtain a series of formulae. It is found that multicombining networks (MCNs) and repetitive combining networks (RCNs) are equivalent to each other and they can all be simplified into the simplest fundamental combining systems. It would be useful for adjusting the number, widths, and positions of photonic bands, and would possess potential applications for the designing of all-optical devices and photonic network devices.

By using the B3P86/aug-cc-pvtz method, the accurate equilibrium geometry of the AlSO (CS,X2A'') molecule has been calculated and compared with available theoretical values. The obtained results show that the AlSO molecule has a most stable structure with bond lengths of ROAl = 0.1864 nm, ROS = 0.1623 nm, RAlS = 0.2450 nm, together with a dissociation energy of 13.88 eV. The possible electronic states and their reasonable dissociation limits for the ground state of the AlSO molecule were determined based on the principle of atomic and molecular reaction statics. The analytic potential energy function of the AlSO molecule was derived by the many-body expansion theory and the contour lines were constructed for the first time, which show the internal information of the AlSO molecule, including the equilibrium structure and stable point. The analysis demonstrates that the obtained potential energy function of AlSO is reasonable and successful and the present investigations provide important insights for further study on molecular reaction dynamics.

By means of the network equation and generalized dimensionless Floquet–Bloch theorem, this paper investigates the properties of the band number and width for quadrangular multiconnected networks (QMNs) with a different number of connected waveguide segments (NCWSs) and various matching ratio of waveguide length (MRWL). It is found that all photonic bands are wide bands when the MRWL is integer. If the integer attribute of MRWL is broken, narrow bands will be created from the wide band near the centre of band structure. For two-segment-connected networks and three-segment-connected networks, it obtains a series of formulae of the band number and width. On the other hand, it proposes a so-called concept of two-segment-connected quantum subsystem and uses it to discuss the complexity of the band structures of QMNs. Based on these formulae, one can dominate the number, width and position of photonic bands within designed frequencies by adjusting the NCWS and MRWL. There would be potential applications for designing optical switches, optical narrow-band filters, dense wavelength-division-multiplexing devices and other correlative waveguide network devices.

The systematic trends of electrionic structure and optical properties of rutile (P42/mnm) RuO2 have been calculated by using the plane-wave norm-conserving pseudopotential density functional theory (DFT) method within the generalised gradient approximation (GGA) for the exchange–correlation potential. The obtained equilibrium structure parameters are in excellent agreement with the experimental data. The calculated bulk modulus and elastic constants are also in good agreement with the experimental data and available theoretical calculations. Analysis based on electronic structure and pseudogap reveals that the bonding nature in RuO2 is a combination of covalent, ionic and metallic bonds. Based on a Kramers–Kronig analysis of the reflectivity, we have obtained the spectral dependence of the real and imaginary parts of the complex dielectric constant (1 and 2, respectively) and the refractive index (n); and comparisons have shown that the theoretical results agree well with the experimental data as well. Meanwhile, we have also calculated the absorption coefficient, reflectivity index, electron energy loss function of RuO2 for radiation up to 30 eV. As a result, the predicted reflectivity index is in good agreement with the experimental data at low energies.