[en] The endochronic theory of plasticity has been applied to study the axially symmetric motion of a finite circular cylindrical shell subjected to an arbitrary pressure transient applied to its inner surface. The constitutive equations for thin shells have been obtained. The governing equations are then solved by means of the characteristics method. It is found that there exist two characteristic waves: one corresponds to the longitudinal wave while the other represents the shear wave. Several numerical examples are presented for specific boundary conditions and a prescribed loading history along the axial direction. The radial displacement profiles in this analysis show the coupling effect of both longitudinal and shear waves. Furthermore, the resultant displacement history seems in good agreement qualitatively with the pressure input function. (Auth.)

[en] This work investigates the variations of the infrared transmission spectra of yttrium-hydride films YH_x during the hydrogen loading process for the frequency range 500 - 4000 cm-1. The results indicate that the transmittance slightly decreases in the dihydride phase, followed by a significant increase in the trihydride phase. In addition, the carrier concentration decreases, whereas the carrier relaxation time increases with hydrogen content. The hydrogen vibration modes at interstitial sites are completely screened in the dihydride phase. The screening effect decreases as the system goes through the metal - insulator transition. Moreover, the screening effect can be continuously tuned by simply varying the hydrogen content in the yttrium-hydride system. Analysis indicates that the absorption intensity of the vibration mode depends on the carrier concentration. This effect can be used as a diagnostic tool for estimating the carrier concentration and hydrogen content in rare-earth hydrides. [copyright] 2001 American Institute of Physics

[en] Models are developed for the dynamic plastic response of the shell structures within the heat transfert system and also the dynamic plastic response of the relief system rupture discs. These two problems require completely different mathematical formulations for efficient solution. A comparison between the two methods is included as well as their relationship to the comprehensive analysis system being developed for treating the entire sodium/water reaction event. For the shell problems, the method chosen is based on endochronic theory of viscoplasticity. The formulation treats essentially arbitrary material property descriptions, includes strainrate dependence, but not requires the definition of a yield surface. A method-of-characteristics solution of the governing equations was used. Determination of the dynamic response of rupture discs differs in that it is essentially a small strain, large displacement phenomena. This has been modeled through the use of a convected coordinate finite element method. Results obtained illustrate dynamic plastic wave propagation in a steam generator shell and final deformations resulting from typical pressure pulses generated by large sodium/water reactions. For similar pressure loadings, the early dynamic behavior of typical secondary system rupture discs is illustrated in a series of parametric studies. Since both methods are capable of treating certain special problems not involving large displacements, a sample problem of this type is included. The relationship of these predictions of structure response to the on-going development of the comprehensive sodium/water reaction code SWAAM-I are discussed

[en] The strain relaxation in In_0.25Ga_0.75As and In_0.4Ga_0.6As grown on GaAs substrates at low temperature has been studied before and after laterally oxidizing an underlying Al_0.98Ga_0.02As layer. The relaxation as a function of layer thickness has been measured by cross-sectional transmission electron microscopy and x-ray analysis. It is found that oxidation of the Al_0.98Ga_0.02As layer improves the relaxation of the strained In_xGa_1-xAs layer. Moreover, the interfacial misfit dislocations have been removed, and the threading dislocation density has decreased approximately by one order of magnitude after oxidation

[en] Amorphous and polycrystalline compounds of (Ga,As) and (Al,As) grown at very low temperatures by molecular-beam epitaxy are characterized. The ultimate microstructure and the amount of excess arsenic incorporated in the (Ga,As) or (Al,As) layers are found to depend on the arsenic overpressure during the low-temperature growth. With lower arsenic overpressure, a polycrystalline structure prevails and less excess arsenic is observed inside the layer. In contrast, a high incorporation of excess arsenic achieved by high-arsenic overpressures leads to the formation of amorphous films. Upon wet oxidation, the lateral oxidation rate of (Al,As) is found to depend on the crystallinity of the (Al,As) layer and the amount of excess arsenic. During the same process, recrystallization proceeds in the (Ga,As) layer

[en] In Taiwan, many groups engage in the development of TiNi SMAs. The two-stage martensitic transformations of B2<=>R-phase<=>B19' and B2<=>B19<=>B19' have been clarified for both TiNi binary and ternary alloys. The deformation behaviours have been investigated by cold-rolling, hot-rolling and wire drawing. Both shape memory effect and pseudoelasticity can be improved by some thermo-mechanical treatments. The damping characteristics of TiNi and TiNiX SMAs have also been systematically studied. Both B19'/B19 martensite (M) and R-phase (R) have high damping capacities due to stress induced movement of twin boundaries. Meanwhile, the addition of third elements, Fe and Cu, can largely increase the damping capacity. Recently, some high temperature shape memory alloys of TiNiPd and TiNiAu SMAs and thin films of TiNi and TiNiX alloys have also been intensively studied in Taiwan. All these potential investigations on the TiNi SMAs in Taiwan have attracted much attention and their important characteristics will be applied widely in the near future. (author)

[en] We present an approach to the analysis of entanglement in smooth bipartite continuous-variable states. One or both parties perform projective filterings via preliminary measurements to determine whether the system is located in some region of space; we study the entanglement remaining after filtering. For small regions, a two-mode system can be approximated by a pair of qubits and its entanglement fully characterized, even for mixed states. Our approach may be extended to any smooth bipartite pure state or two-mode mixed state, leading to natural definitions of concurrence and negativity densities. For Gaussian states both these quantities are constant throughout configuration space

[en] This paper investigates the electrical response of a series connection of piezoelectric energy harvesters (PEHs) attached to various interface electronics, including standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits. In contrast to the case of parallel connection of multiple oscillators, the system response is determined by the matrix formulation of charging on a capacitance. In addition, the adoption of an equivalent impedance approach shows that the capacitance matrix can be explicitly expressed in terms of the relevant load impedance. A model problem is proposed for performance evaluation of harvested power under different choices of interface circuits. The result demonstrates that the parallel-SSHI array system exhibits higher power output with moderate bandwidth improvement, while the series-SSHI system delivers a pronounced wideband at the cost of peak harvested power. The standard array system shows a mild ability in power harvesting between these two SSHI systems. Finally, comparisons between the series and parallel connection of oscillators are made, showing the striking contrast of these two cases. (paper)

[en] In this paper we address the question: where in configuration space is the entanglement between two particles located? We present a thought experiment, equally applicable to discrete or continuous-variable systems, in which one or both parties makes a preliminary measurement of the state with only enough resolution to determine whether or not the particle resides in a chosen region, before attempting to make use of the entanglement. We argue that this provides an operational answer to the question of how much entanglement was originally located within the chosen region. We illustrate the approach in a spin system, and also in a pair of coupled harmonic oscillators. Our approach is particularly simple to implement for pure states, since in this case the subensemble in which the system is definitely located in the restricted region after the measurement is also pure, and hence its entanglement can be simply characterized by the entropy of the reduced density operators. For our spin example we present results showing how the entanglement varies as a function of the parameters of the initial state; for the continuous case, we also find how it depends on the location and size of the chosen regions. Hence we show that the distribution of entanglement is very different from the distribution of the classical correlations

[en] Electrical analysis of interfaces of (100)Si, (100)InP, and (100)In_0.53Ga_0.47As with TaSiO_x (Ta/Si≈1) films atomic-layer deposited using SiCl₄, TaCl₅, and H₂O precursors suggests Ta silicate as a good insulating and surface passivating layer on all three semiconductors. However, when a positive voltage is applied to the top metal electrode in a metal/ TaSiO_x /semiconductor configuration, considerable hysteresis of the capacitance-voltage curves, both at 300 and 77 K, is universally observed indicating electron injection and trapping in the insulator. To shed some light on the origin of this charge instability, we analyzed interface band alignment of the studied interfaces using the spectroscopies of internal photoemission and photoconductivity measurements. The latter reveals that independently of the semiconductor substrate material, TaSiO_x layers exhibit a bandgap of only 4.5±0.1 eV, typical for a Ta₂O₅ network. The density of electron states associated with this narrow-gap network may account for the enhanced electron injection and trapping. Furthermore, while a sufficiently high energy barrier for electrons between Si and TaSiO_x (3.1±0.1 eV) is found, much lower IPE thresholds are encountered at the (100)InP/TaSiO_x and (100) In_0.53Ga_0.47As/TaSiO_x interfaces, i.e., 2.4 and 2.0 eV, respectively. The lower barrier may be related by the formation of narrow-gap In-rich interlayers between A_IIIB_V semiconductors and TaSiO_x.