Analysis of coupling vibration characteristics of electrically driven pile hammer linkage system

In order to solve the problem that electromechanical coupling had influences on the control effect of multi-pile hammers linkage, the coupling influence rules were studied. With the complex system of hammer-pile-soil being simplified, the dynamic model was constructed for the two pile hammers vibration system. The mathematical equations of systemic electromechanical coupling were established. Based on the Hamilton principle, synchronous operation conditions and system stability were established. Simulation model was developed with MATLAB/Simulink for numerical simulation. The electromechanical coupling processes and the basic system rules were obtained under different electrical motors’ speeds, the initial phase differences, soil parameters and fixing parameters. It could be found that electromechanical coupling might result in self-synchronization under given conditions. Finally, the mathematical model’s validity, theoretical derivation and simulation results were proved by some experiments. The analytical conclusions of electromechanical coupling rules provide the theoretical evidence for making control strategy on electric control linkage mode, and the basis for related engineering applications and experiments

Electronic structures of [111]-oriented free-standing InAs and InP nanowires

We report on a theoretical study of the electronic structures of the [111]-oriented, free-standing, zincblende InAs and InP nanowires with hexagonal cross sections by means of an atomistic $sp^{3}s^{*}$, spin-orbit interaction included, nearest-neighbor, tight-binding method. The band structures and the band state wave functions of these nanowires are calculated and the symmetry properties of the bands and band states are analyzed based on the $C_{3v}$ double point group. It is shown that all bands of these nanowires are doubly degenerate at the $\Gamma$-point and some of these bands will split into non-degenerate bands when the wave vector $k$ moves away from the $\Gamma$-point as a manifestation of spin-splitting due to spin-orbit interaction. It is also shown that the lower conduction bands of these nanowires all show simple parabolic dispersion relations, while the top valence bands show complex dispersion relations and band crossings. The band state wave functions are presented by the spatial probability distributions and it is found that all the band states show $2\pi/3$-rotation symmetric probability distributions. The effects of quantum confinement on the band structures of the [111]-oriented InAs and InP nanowires are also examined and an empirical formula for the description of quantization energies of the lowest conduction band and the highest valence band is presented. The formula can simply be used to estimate the enhancement of the band gaps of the nanowires at different sizes as a result of quantum confinement.Comment: 9 pages, 8 figures. arXiv admin note: substantial text overlap with arXiv:1502.0756

Topological energy gaps in the [111]-oriented InAs/GaSb and GaSb/InAs core-shell nanowires

The [111]-oriented InAs/GaSb and GaSb/InAs core-shell nanowires have been studied by the $8\times 8$ Luttinger-Kohn $\vec{k}\cdot\vec{p}$ Hamiltonian to search for non-vanishing fundamental gaps between inverted electron and hole bands. We focus on the variations of the topologically nontrivial fundamental gap, the hybridization gap, and the effective gap with the core radius and shell thickness of the nanowires. The evolutions of all the energy gaps with the structural parameters are shown to be dominantly governed by quantum size effects. With a fixed core radius, a topologically nontrivial fundamental gap exists only at intermediate shell thicknesses. The maximum gap is $\sim 4.4$ meV for GaSb/InAs and $\sim 3.5$ meV for InAs/GaSb core-shell nanowires, and for the GaSb/InAs core-shell nanowires the gap persists over a wider range of geometrical parameters. The intrinsic reason for these differences between the two types of nanowires is that in the shell the electron-like states of InAs is more delocalized than the hole-like state of GaSb, while in the core the hole-like state of GaSb is more delocalized than the electron-like state of InAs, and both features favor stronger electron-hole hybridization. Since similar features of the electron- and hole-like states have been found in nanowires of other materials, it could serve as a common rule to put the hole-like state in the core while the electron-like state in the shell of a core-shell nanowire to achieve better topological properties.Comment: 10 pages, 10 figure

Electronic structures of [001]- and [111]-oriented InSb and GaSb free-standing nanowires

We report on a theoretical study of the electronic structures of InSb and GaSb nanowires oriented along the [001] and [111] crystallographic directions. The nanowires are described by atomistic, spin-orbit inteaction included, tight-binding models, and the band structures and the wave functions of the nanowires are calculated by means of a Lanczos iteration algorithm. For the [001]-oriented InSb and GaSb nanowires, the systems with both square and rectangular cross sections are considered. Here, it is found that all the energy bands are double degenerate. Furthermore, although the lowest conduction bands in these nanowires show good parabolic dispersions, the top valence bands show rich and complex structures. In particular, the topmost valence bands of these nanowires with a square cross section show a double maximum structure. In the nanowires with a rectangular cross section, this double maximum structure is suppressed and top valence bands gradually develop into parabolic bands as the aspect ratio of the cross section is increased. For the [111]-oriented InSb and GaSb nanowires, the systems with hexagonal cross sections are considered. It is found that all the bands at the \Gamma-point are again double degenerate. However, some of them will split into non-degenerate bands when the wave vector moves away from the \Gamma-point. Furthermore, although the lowest conduction bands again show good parabolic dispersions, the topmost valence bands do not show the double maximum structure but, instead, a single maximum structure with its maximum at a wave vector slightly away from the \Gamma-point. We also investigate the effects of quantum confinement on the band structures of the [001]- and [111]-oriented InSb and GaSb nanowires and present an empirical formula for the description of quantization energies of the band edge states in the nanowires.Comment: 17 pages, 19 figure

Drug dosing during pregnancy—opportunities for physiologically based pharmacokinetic models

Drugs can have harmful effects on the embryo or the fetus at any point during pregnancy. Not all the damaging effects of intrauterine exposure to drugs are obvious at birth, some may only manifest later in life. Thus, drugs should be prescribed in pregnancy only if the expected benefit to the mother is thought to be greater than the risk to the fetus. Dosing of drugs during pregnancy is often empirically determined and based upon evidence from studies of non-pregnant subjects, which may lead to suboptimal dosing, particularly during the third trimester. This review collates examples of drugs with known recommendations for dose adjustment during pregnancy, in addition to providing an example of the potential use of PBPK models in dose adjustment recommendation during pregnancy within the context of drug-drug interactions. For many drugs, such as antidepressants and antiretroviral drugs, dose adjustment has been recommended based on pharmacokinetic studies demonstrating a reduction in drug concentrations. However, there is relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Examples of using pregnancy PBPK models to predict feto-maternal drug exposures and their applications to facilitate and guide dose assessment throughout gestation are discussed

k.p theory of freestanding narrow band gap semiconductor nanowires

We report on a theoretical study of the electronic structures of freestanding nanowires made from narrow band gap semiconductors GaSb, InSb and InAs. The nanowires are described by the eight-band k.p Hamiltonians and the band structures are computed by means of the finite element method in a mixture basis consisting of linear triangular elements inside the nanowires and constrained Hermite triangular elements near the boundaries. The nanowires with two crystallographic orientations, namely the [001] and [111] orientations, and with different cross-sectional shapes are considered. For each orientation, the nanowires of the three narrow band gap semiconductors are found to show qualitatively similar characteristics in the band structures. However, the nanowires oriented along the two different crystallographic directions are found to show different characteristics in the valence bands. In particular, it is found that all the conduction bands show simple, good parabolic dispersions in both the [001]- and [111]-oriented nanowires, while the top valence bands show double-maximum structures in the [001]-oriented nanowires, but single-maximum structures in the [111]-oriented nanowires. The wave functions and spinor distributions of the band states in these nanowires are also calculated. It is found that significant mixtures of electron and hole states appear in the bands of these narrow band gap semiconductor nanowires. The wave functions exhibit very different distribution patterns in the nanowires oriented along the [001] direction and the nanowires oriented along the [111] direction. It is also shown that single-band effective mass theory could not reproduce all the band state wave functions presented in this work

Simulation of Light-Trapping Characteristics of Self-Assembled Nano-Ridges in Ternary Organic Film

The presence of self-assembled nano-ridged (SANR) structures in PTB7-Th:PC70BM:PC60BM ternary organic blend film with the specific component ratio was experimentally clarified, and the light-trapping effect of the SANR structures was demonstrated. On this basis, the light-trapping characteristics of the PTB7-Th:PC70BM:PC60BM ternary blend film with the SANR structures were investigated by using the finite-difference time-domain (FDTD) algorithm. The results showed that the SANR structures have a light-trapping effect, which can effectively reduce the transmittance and reflectance of the incident photons at the specific wavelengths and thus exhibit stronger photon absorption, especially for the photons in the wavelength range of 550–650 nm. The light-trapping effect of the SANR structures does not depend on the direction of photon incidence, and the active layer traps the photons incident from both its top and bottom. The dimensional variation of the SANR has a significant effect on the light-trapping characteristics of the active layer, and the effect caused by the height variation is overwhelmingly superior compared with that of the width variation. In addition, the higher the density of the SANR, the more significant the light-trapping effect of the active layer. This work provides a theoretical basis for the further experimental enhancement of the photon absorption capacity of the PTB7-Th:PC70BM:PC60BM active layer with SANR structures