ALBERT

Description: Scandium trifluoride (ScF 3 ), adopting a cubic ReO 3 -type structure at ambient pressure, undergoes a pronounced negative thermal expansion (NTE) over a wide range of temperatures (10 K–1100 K). Here, we report the size effects on the NTE properties of ScF 3 . The magnitude of NTE is reduced with diminishing the crystal size. As revealed by the specific heat measurement, the low-energy phonon vibrations which account for the NTE behavior are stiffened as the crystal size decreases. With decreasing the crystal size, the peaks in high-energy X-ray pair distribution function (PDF) become broad, which cannot be illuminated by local symmetry breaking. Instead, the broadened PDF peaks are strongly indicative of enhanced atomic displacements which are suggested to be responsible for the stiffening of NTE-related lattice vibrations. The present study suggests that the NTE properties of ReO 3 -type and other open-framework materials can be effectively adjusted by controlling the crystal size.

Description: Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic simulations are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global hybrid simulation model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x = − 30 R E ∼ − 15 R E around the equatorial plane ( z = 0 ). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R E , and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R E and does not extend across the entire section of the magnetotail, contrary to previous models and MHD simulation results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric ( x , y ) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the evolution of the flux ropes in the multiple X-line reconnection layer can also lead to the acceleration and heating of ions.

Description: The Yuan-Agrawal (YA) memory-free approach is employed to study fractional dynamical systems with freeplay nonlinearities subjected to a harmonic excitation, by combining it with the precise integration method (PIM). By the YA method, the original equations are transformed into a set of first-order piecewise-linear ordinary differential equations (ODEs). These ODEs are further separated as three linear inhomogeneous subsystems, which are solved by PIM together with a predictor-corrector process. Numerical examples show that the results by the presented method agree well with the solutions obtained by the Runge-Kutta method and a modified fractional predictor-corrector algorithm. More importantly, the presented method has higher computational efficiency.

Description: We have demonstrated a low temperature formation (300 °C) of higher- k HfO 2 using atomic layer deposition (ALD) on an in-situ thermal oxidation GeO x interfacial layer. It is found that the cubic phase is dominant in the HfO 2 film with an epitaxial-like growth behavior. The maximum permittivity of 42 is obtained for an ALD HfO 2 film on a 1-nm-thick GeO x form by the in-situ thermal oxidation. It is suggested from physical analyses that the crystallization of cubic phase HfO 2 can be induced by the formation of six-fold crystalline GeO x structures in the underlying GeO x interfacial layer.

Description: With increasing and more stringent requirements for advanced vehicle integration, including vehicle dynamics and control, traditional control and optimization strategies may not qualify for many applications. This is because, among other factors, they do not consider the nonlinear characteristics of practical systems. Moreover, the vehicle wheel model has some inadequacies regarding the sideslip angle, road adhesion coefficient, vertical load, and velocity. In this paper, an adaptive neural wheel network is introduced, and the interaction between the lateral and vertical dynamics of the vehicle is analyzed. By means of nonlinear analyses such as the use of a bifurcation diagram and the Lyapunov exponent, the vehicle is shown to exhibit complicated motions with increasing forward speed. Furthermore, electric power steering (EPS) and active suspension system (ASS), which are based on intelligent control, are used to reduce the nonlinear effect, and a negotiation algorithm is designed to manage the interdependences and conflicts among handling stability, driving smoothness, and safety. Further, a rapid control prototype was built using the hardware-in-the-loop simulation platform dSPACE and used to conduct a real vehicle test. The results of the test were consistent with those of the simulation, thereby validating the proposed control.

Description: The tetragonal-phase BaTiO 3 as the high dielectric (HK) layer and the magnetic FePt film as the metal gate (MG) are proposed to be the gate stack scheme on the Ge (100) substrate. The ∼75% dielectric constant ( κ -value) improvement, ∼100X gate leakage ( Jg) reduction, and the promising Jg -equivalent-oxide-thickness ( EOT ) gate stack characteristics are achieved in this work with the colossal magneto-capacitance effect. The perpendicular magnetic field from the magnetic FePt MG film couples and triggers the more dipoles in the BaTiO 3 HK layer and then results in the super gate capacitance ( C gate ) and κ -value. Super Jg-EOT gate stack characteristics with the magnetic gate stack design on the high mobility (Ge) substrate demonstrated in this work provides the useful solution for the future low power mobile device design.

Description: Development of robust instrumentation has shown evidence for a multi-μC expulsion of relativistic electrons from a sub-μm-thick foil, laser illuminated with 60–70 J on target at 2 × 10 20  W/cm 2 . From previous work and with electron spectroscopy, it is seen that an exponential electron energy distribution is accurate enough to calculate the emitted electron charge and energy content. The 5–10- μ C charge for the 〉100-TW Trident Laser represents the first active measurement of the 〉50% laser-light-to-electron conversion efficiency. By shorting out the TV/m electric field usually associated with accelerating multi-MeV ions from such targets, one finds that this charge is representative of a multi-MA current of relativistic electrons for diverse applications from electron fast ignition to advanced radiography concepts. Included with the details of the discoveries of this research, shortcomings of the diagnostics and means of improving their fidelity are discussed.

Description: In this work, the tetragonal-phase BaTiO 3 high dielectric (HK) layer and the magnetic FePt metal gate (MG) film are proposed to be the gate stack scheme on the Ge three dimensional (3D) n-type multi-gate-field-effect transistors (FETs). The ∼75% dielectric constant (κ-value) improvement, ∼100× gate leakage (J g ) reduction, and ∼70% on-state current (I on ) enhancement are achieved due to the colossal magneto-capacitance effect. The magnetic field from the magnetic FePt MG film couples and triggers more dipoles in the BaTiO 3 HK layer and then results in the super gate stack characteristics. The promising transistor's performance (∼200  μ A/ μ m on the device with the gate length L ch  = 60 nm) on the high mobility (Ge) material in the 3D n-type multi-gate-FETs device structure demonstrated in this work provides the useful solution for the future advanced logic device design.

Description: We demonstrate a three-axis atomic magnetometer with one intensity-modulated pump beam and one orthogonal probe beam. The main field component is measured using the resonance of the pumping light, while the transverse field components are measured simultaneously using the optical rotation of the probe beam modulated by the spin precession. It is an all-optical magnetometer without using any modulation field or radio frequency field. Magnetic field sensitivity of 0.8 pT/Hz 1∕2 is achieved under a bias field of 2  μ T.

Description: We propose an accurate approach, based on the precise integration method, to solve the aeroelastic system of an airfoil with a pitch hysteresis. A major procedure for achieving high precision is to design a predictor-corrector algorithm. This algorithm enables accurate determination of switching points resulting from the hysteresis. Numerical examples show that the results obtained by the presented method are in excellent agreement with exact solutions. In addition, the high accuracy can be maintained as the time step increases in a reasonable range. It is also found that the Runge-Kutta method may sometimes provide quite different and even fallacious results, though the step length is much less than that adopted in the presented method. With such high computational accuracy, the presented method could be applicable in dynamical systems with hysteresis nonlinearities.