Step-like Change Research Articles

The effect of sulfide substitution in the mixed conductor Cu 7PSe 6

Cu 7PSe 6 is a mixed conductor exhibiting structural phase transitions above and below room temperature that are accompanied by step-like changes in electrical conductivity. The substitution of S 2− for Se 2− in Cu 7PSe 6 significantly enhances electrical conductivity at room temperature compared to that observed for the pure compound. In the case of Cu 7P(Se 0.80S 0.20) 6, a nearly temperature-independent electrical conductivity exceeds 1 S/cm with no evidence of any phase transitions throughout the temperature interval 200–400 K. However, the ionic contribution accounts for just 2% of the total electrical conductivity in this solid solution at room temperature.

Flowing damage in ion-implanted amorphous silicon

Using molecular-dynamics simulations, we have studied the creation and evolution of damage in crystalline and amorphous silicon following the implantation of energetic keV ions. A method is proposed to identify anomalous atoms based on a weighted combination of local, atomic-scale properties, which applies to both Si phases. For crystalline Si, the passage of the ions causes compact amorphous regions to form, while no evidence for melting is observed. The relaxation of the amorphouslike regions proceeds initially by the rapid recrystallization of smaller clusters and isolated atoms, followed by a long period of steplike changes in the number of defects due to spontaneous annealing of damage pockets at the crystalline-amorphous interface. In amorphous Si, the initial stage of damage annealing (which lasts a few picoseconds) resembles closely that observed in crystalline Si; on larger time scales, however, the damage is found to ``percolate,'' or flow, through the system, inducing damage away from the collision cascade, thus causing an overall ``derelaxation'' of the material.

A major step in the continental Moho and its geodynamic consequences: the Taranaki-Ruapehu line, New Zealand

Receiver function analysis reveals a 7 km step-like change in crustal thickness across the Taranaki–Ruapehu Line (TR-line) of North Island, New Zealand. The TR-line runs east–west between the active andesite volcanoes of Mt Taranaki and Ruapehu and marks the southern-most extent of subduction zone volcanism in New Zealand. North of the TR-line receiver functions show a strong and sharp P-to-S (Ps) conversion at 25 ± 1.5 km depth, which is interpreted as a shallow Moho. At the TR-line the Moho Ps conversion deepens across a step to ∼32 km depth and weakens. Further south the Moho deepens to >35 km. Most of the 7 km step-change in crustal thickness occurs over a lateral distance of ∼8 km, yet there is little surface or topographic manifestation of the line. Given Fresnel zone considerations, the dip of the Moho offset could vary between 90° and 45°. Gravity, seismic attenuation and electrical data all show that the TR-line is not only a step in crustal thickness but also a profound lithospheric boundary as mantle properties, such as attenuation (Qp−1), implied density, and electrical resistivity change abruptly across the line. An east–west oriented cluster of earthquakes with hypocentral depths of 20–40 km is centred on the Moho step. We propose that the Moho step, the earthquakes and the rapid change in mantle properties across the TR boundary are causally related. Processes that could be responsible for the phenomena described here include the rapid removal of mantle lithosphere and lower crust to the north of the TR-line.

Magnetic features of the magmatic intrusion that occurred in the 2007 eruption at Stromboli Island (Italy)

Significant changes in the local magnetic field marked the resumption of eruptive activity at Stromboli volcano on February 27, 2007. After differential magnetic fields were obtained by filtering out external noise using adaptive filters and seasonal thermal noise using temperature data, we identified step-like changes of 1–4 nT coincident with the opening of eruptive fissures in the upper part of the Sciara del Fuoco. The magnetic variations detected at two stations are closely related to the propagation of a shallow NE–SW magmatic intrusion extending beyond the summit craters area. These observations are consistent with those calculated using piezomagnetic models in which stress-induced changes in rock magnetization are produced by the magmatic intrusion. No significant magnetic changes were observed when the first fractures opened along the NE crater rim. Indeed, the stress-induced magnetization caused by this magmatic activity is expected to be too low because of the structural weakness and/or thermal state of the summit area. The continuous long-term decay characterizing the post-eruptive magnetic pattern can be related to a time-dependent relaxation process. A Maxwell rheology was assumed and the temporal evolution of the piezomagnetic field was evaluated. This allowed us to estimate the rheological properties of the medium; in particular, an average viscosity ranging between 1016 and 1017 Pa⋅s was a relaxation time τ of about 38 days.

Past trends and future scenarios for environmental conditions favoring the accumulation of paralytic shellfish toxins in Puget Sound shellfish

The risk of harmful algal blooms (HABs) of the dinoflagellate Alexandrium catenella in Puget Sound, Washington State, can be assessed by identifying and predicting climate and environmental conditions that are favorable for bloom development and the accumulation of paralytic shellfish toxins (PSTs) in shellfish. When these favorable conditions occur in combination, a harmful algal bloom window of opportunity (HAB-WOO) exists for A. catenella. The original HAB-WOO was identified by Moore et al. (2009) for the time period 1993–2007. In general, it showed that warm air and water temperatures, low streamflow, low winds, and small tidal variability precede PST events. Here, we use the HAB-WOO model to examine (i) changes in the annual HAB-WOO duration over the period from 1967 to 2006, and (ii) the potential effect of future climate change on HAB risk through the late 21st century. The annual HAB-WOO duration increased between 1978 and 2006, as did the frequency and geographic extent of PST events. Two step-like changes occurred in 1978 and 1992 with higher annual values attained by the HAB-WOO compared to previous years. The 1978 step change may be related to the 1977 reversal of the Pacific Decadal Oscillation from cool to warm phase. Climate change projections from global climate models and regionally downscaled climate models for the Pacific Northwest are used to evaluate scenarios for the future HAB-WOO. Under a moderate greenhouse gas emissions scenario (i.e., A1B), the annual HAB-WOO for A. catenella in Puget Sound is projected to increase by an average of 13 days by the end of the 21st century. Furthermore, the annual HAB-WOO may begin up to 2 months earlier in the year and persist for up to 1 month later in the year compared to the present day. This research provides managers, health authorities, and shellfish growers in Washington State with critical information for anticipating climate impacts on toxic HABs in the Pacific Northwest now and in a future warmer climate.

Transient phenomena of disk MHD generator due to change of load resistance

AbstractThe results of an experimental study on transient phenomena in a closed cycle disk MHD generator are described in this paper. The transient phenomena were caused by a steplike change of load resistance during testing of the shock‐tube driven disk MHD generator. The load resistance was varied by using an IGBT (insulated gate bipolar transistor) installed in the load circuit. When the load resistance was changed from 0.096 Ω to 2.5 Ω, overshoot of the Hall output voltage and of the Hall electric field was observed, and a large fluctuation of static pressure was also observed. At the same time, a spikelike increase of the cesium recombination continuum and line spectrum appeared just after the load change. The results of quasi‐one‐ dimensional numerical simulation indicate that the observed overshoot was caused by the following phenomena: (1) a steep reduction of the Hall current and a steep increase in both the Faraday current and the electrical conductivity and (2) a slow reduction of the gas velocity due to the enhanced retarding force. Furthermore, the measured spikelike increase of the radiation intensity was ascribed to an increase of electron temperature and electron number density due to a steep increase of Joule heating. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 34–42, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21004

Magnetic moment of phonons in graphene induced by a magnetic field

A magnetic field not only changes the electronic structure in graphene but also affects the phonon excitations via the electron–phonon interaction and even enables the phonons to generate magnetism. In this paper, we evaluate the magnetic moment of phonons in graphene using a generating-functional technique. The calculation results indicate that the phonon magnetic moment exists only in a weak magnetic field. The step-like change of the magnetic moment with the magnetic field reflects a macroscopic quantum effect.

Estimating errors in pins inertial sensor readings with l 1-approximation

We present a new method for estimating errors in inertial sensors of navigational systems. The method is based on l 1-approximation, especially efficient if the errors undergo steplike changes.

ULTRASONIC VELOCITY AND OXYGEN-RELATED ELASTIC ANOMALIES IN Zn2+-SUBSTITUTED (Dy,Ca)Ba2Cu3-yZnyO7-δ SUPERCONDUCTORS

Ultrasonic longitudinal velocity measurements between 80 K and 280 K and shear velocity measurements between 80 K and 230 K have been performed in polycrystalline superconducting DyBa 2 Cu 3-x Zn x O 7-δ (x = 0, 0.01 and 0.03) and Dy 0.9 Ca 0.1 Ba 2 Cu 3-y Zn y O 7-δ (y = 0.01) samples utilizing the pulsed-echo-overlap technique. A longitudinal anomaly characterized by a step-like slope change was observed at around 240 K for DyBa 2 Cu 3-x Zn x O 7-δ (x = 0) and at 230 K for x=0.01 and 0.03. Zn 2+ substitution suppressed critical temperature, Tc but did not suppress the step-like anomaly. On the other hand, substitution of Ca 2+ in Dy 0.9 Ca 0.1 Ba 2 Cu 3-y Zn y O 7-δ (y = 0.01) caused the step-like anomaly to disappear. The step-like anomaly was suggested due to the oxygen-ordering process in Cu – O chains during a phase transition process at low temperatures. Substitution of Zn 2+ ions in place of Cu was suggested to go into CuO 2 planes and did not interfere with oxygen-ordering in Cu – O chains. This is suggested as the reason why the step-like anomalies were not suppressed in DyBa 2 Cu 3-x Zn x O 7-δ (x = 0.01 and 0.03) samples. Disappearance of the step-like anomaly due to Ca 2+ substitution is probably related to reduction in oxygen content which depletes Cu – O chain sites.

Identification of Multimodal Pilot Models Using Ramp Target and Multisine Disturbance Signals

This paper investigates the extent to which target forcing functions consisting of multiple ramplike or steplike changes in target attitude can be used for identification of multimodal pilot models. The main question addressed is whether such signals provide enough excitation of the pilot-vehicle system to allow for reliable estimation of pilot model parameters from measured pilot control data. The compensatory control task from a previous human-in-the-loop experiment performed in a moving base flight simulator is used to define a typical multimodal pilot model identification problem. Using simulations of this control task, where different multisine and ramp target forcing function signals are used to excite the pilot-vehicle system (in addition to a multisine disturbance signal), the accuracy and consistency of pilot model estimation results are evaluated. It is found that both the bias and variance of the pilot model parameter estimates decrease with increasing ramp signal steepness. If the steepnesses of the ramps in the target signals are higher than 3 deg /s, estimation results are found to be more accurate than those obtained using a quasi-random target forcing function. This indicates that reliable pilot model identification results can be obtained using such ramp target forcing function signals.

HIGHLIGHTS FROM THE LITERATURE

HIGHLIGHTS FROM THE LITERATURE

Vortex Core Contribution to Textural Energy in 3He–B Below 0.4T c

Vortex lines affect the spatial order-parameter distribution in superfluid 3He-B owing to superflow circulating around vortex cores and due to the interaction of the order parameter in the core and in the bulk as a result of superfluid coherence over the whole volume. The step-like change of the latter contribution at 0.6Tc (at a pressure of 29bar) signifies the transition from axisymmetric cores at higher temperatures to broken-symmetry cores at lower temperatures. We extended earlier measurements of the core contribution to temperatures below 0.2Tc, in particular searching for a possible new core transition to lower symmetries. As a measuring tool we track the energy levels of magnon condensate states in a trap formed by the order-parameter texture.

Dielectric response of PTFE and ETFE wiring insulation to thermal exposure

The change in dielectric properties of wire insulation due to various degradation processes is significant for health management of air- and spacecraft. Polytetrafluoroethylene (PTFE) and ethylene-tetrafluoroethylene (ETFE) are two fluoropolymers which have been widely applied as wiring insulation materials. This paper investigates the dielectric response of PTFE and ETFE to thermal exposure for up to 96 hours at 340°C and 160°C, respectively. The initial dielectric properties of PTFE and ETFE were measured using a Novocontrol dielectric spectrometer over the frequency range 1 Hz to 1 MHz and as a function of temperature. The real permittivity of PTFE decreases with temperature from -150°C to 300°C, and reveals step-like changes near 19°C and 31°C due to crystal phase transitions. The dissipation factor of ETFE, measured from -150°C to 210°C, shows two peaks at -80°C and 92°C, which are associated with molecular relaxations. After thermally exposing the samples, permittivity measurements using an Agilent E4980A LCR meter over the frequency range 1 kHz to 2 MHz at room temperature (25°C) reveals a significant increase in the real permittivity of both PTFE and ETFE as function of thermal exposure time. These observations are explained in terms of an increase in crystallinity of PTFE after thermal exposure above the melting temperature followed by slow cooling, and polar group formation in ETFE following oxidant thermal exposure.

Collisional-inhomogeneity-induced generation of matter-wave dark solitons

We propose an experimentally relevant protocol for the controlled generation of matter-wave dark solitons in atomic Bose–Einstein condensates (BECs). In particular, using direct numerical simulations, we show that by switching-on a spatially inhomogeneous (step-like) change of the s-wave scattering length, it is possible to generate a controllable number of dark solitons in a quasi-one-dimensional BEC. A similar phenomenology is also found in the two-dimensional setting of “disk-shaped” BECs but, as the solitons are subject to the snaking instability, they decay into vortex structures. A detailed investigation of how the parameters involved affect the emergence and evolution of solitons and vortices is provided.

Analysis of Coseismic Water-Level Changes in the Wells in the Koyna-Warna Region, Western India

Abstract We test the hypothesis that coseismic water-level changes in wells are proportional to coseismic volumetric strain by analyzing available data from the Koyna–Warna region of western India. A total of 18 cases of water-level changes have been reported at ten wells corresponding to six earthquakes of M ≥4.3 that occurred in the region from 1997 to 2005. Out of these, clear unambiguous steplike coseismic water-level changes have been observed in ten cases at five confined wells. We used basic poroelastic theory to simulate volumetric strain and corresponding water-level changes and find that all cases show consistency in sign between reported coseismic water-level changes and simulated volumetric strain. All confined wells with high strain sensitivity that are located near earthquake epicenters show good agreement in magnitude between simulated and reported volumetric strain, thereby supporting this hypothesis.

Chemical diffusion in CdTe:Cl

High-temperature in situ galvanomagnetic measurements are reported in chlorine-doped CdTe, [Cl] ≈4 × 1018 cm−3 at temperatures T = 600–700 °C near Cd saturation. The chemical diffusion coefficient is determined by means of relaxation of electrical conductivity after a step-like change of ambient Cd pressure (PCd) and approximated well by a trial function . Both and equilibrium conductivity are calculated on the basis of a defect model in which donors ClTe are compensated by divalent acceptors Cd vacancies (VCd) and monovalent acceptor complexes (ClTeVCd). The properties of native point defects are consistent with undoped CdTe. It is shown that can be fit well assuming different diffusion coefficients for singly and doubly charged VCd.

62842 ON THE USE OF MULTIPLE CONTACT TABLES IN THE ANALYSIS OF VEHICLE/TURNOUT INTERACTIONS OF RAILROAD VEHICLES(Railroad System Dynamics)

It is the objective of this investigation to develop a systematic and automated procedure that can be used for modeling vehicle/turnout interactions. To this end, contact geometry analysis procedure is generalized for turnout simulations such that tongue rail profiles available from measurement and/or drawing can be automatically interpolated and used to produce multiple look-up contact tables. Having obtained multiple look-up contact tables, the wheelset trajectory coordinate is used to locate the nearest look-up contact tables to be interpolated for determining the location of contact point at every time-step in the dynamic analysis. The effects of the number of multiple contact tables on the accuracy of predicting the location of contact points are investigated. This leads to an important insight into the number of contact tables being generated. It is demonstrated with several numerical examples that a sufficient number of contact table needs to be employed for modeling a vehicle/turnout interaction around the region where the location of contact points is transferred to tongue rail. Furthermore, effects of using table-switching and table-interpolation approaches developed in this investigation on the accuracy of vehicle turnout simulation results are discussed. It is demonstrated that undesirable step-like changes in contact inevitable for the table-switching algorithm can be reduced using the table-interpolation algorithm.

015 低ひずみ速度域におけるSUS304ステンレス鋼の特異な変態誘起塑性(GS2-2 一般セッション)

Tensile tests of SUS3O4 austenitic stainless steels were done. We investigated strain rate dependency of fracture elongation, slope of strain hardening rate and environment temperature and characterized defonnation behavior of transfonnation induced plasticity. At low strain rate, a step-like change of fracture elongation was found on the SUS304 specimen at room temperature, 5×10^<-4>s^<-1>. Then correlation has been found between fracture elongation and slope of strain hardening rate.

Motion of the surface of the human tympanic membrane measured with stroboscopic holography

Sound-induced motion of the surface of the human tympanic membrane (TM) was studied by stroboscopic holographic interferometery, which measures the amplitude and phase of the displacement at each of about 40,000 points on the surface of the TM. Measurements were made with tonal stimuli of 0.5, 1, 4 and 8kHz. The magnitude and phase of the sinusoidal displacement of the TM at each driven frequency were derived from the fundamental Fourier component of the raw displacement data computed from stroboscopic holograms of the TM recorded at eight stimulus phases. The correlation between the Fourier estimates and measured motion data was generally above 0.9 over the entire TM surface. We used three data presentations: (i) plots of the phasic displacements along a single chord across the surface of the TM, (ii) phasic surface maps of the displacement of the entire TM surface, and (iii) plots of the Fourier derived amplitude and phase-angle of the surface displacement along four diameter lines that define and bisect each of the four quadrants of the TM. These displays led to some common conclusions: at 0.5 and 1kHz, the entire TM moved roughly in-phase with some small phase delay apparent between local areas of maximal displacement in the posterior half of the TM. At 4 and 8kHz, the motion of the TM became more complicated with multiple local displacement maxima arranged in rings around the manubrium. The displacements at most of these maxima were roughly in-phase, while some moved out-of-phase. Superposed on this in- and out-of-phase behavior were significant cyclic variations in-phase with location of less than 0.2 cycles or occasionally rapid half-cycle step-like changes in-phase. The high frequency displacement amplitude and phase maps discovered in this study can not be explained by any single wave motion, but are consistent with a combination of low and higher order modal motions plus some small traveling-wave-like components. The observations of the dynamics of TM surface motion from this study will help us better understand the sound-receiving function of the TM and how it couples sound to the ossicular chain and inner ear.

Magneto-optical observations of vortex penetration into Bi2Sr2CaCu2O8+y with periodic pinning potentials

The effect of artificially introduced periodic pinning centers fabricated by focused-ion beam milling is studied in highly anisotropic superconductor Bi2Sr2CaCu2O8+y. Step-like changes of local magnetic induction at integer multiples of the matching field are visualized by magneto-optical imaging. Temperature dependence of the matching phenomenon is understood by considering the saturation number of vortices in each pinning center.