Step-like Change Research Articles

Changes of Groundwater Level due to the 1999 Chi-Chi Earthquake in the Choshui River Alluvial Fan in Taiwan

Changes of groundwater levels induced by the M L 7.3 Chi-Chi earthquake on 21 September 1999 were recorded at 157 out of 179 monitoring wells in the Choshui River alluvial fan. Of those, 67 observed large groundwater-level changes, ranging from 1.0 to 11.1 m. These 157 wells are clustered at 64 stations located approximately 2 to 50 km west of the north-south-trending Chelungpu fault. Both oscillatory and steplike changes of water level were observed on the analog records at the time of earthquake, while only steplike changes were observed on the hourly digital records. Coseismic changes of groundwater level were recorded not only in the confined aquifers but also in the partially confined aquifers and the unconfined aquifers. The recovery of water-level changes took minutes to months, depending primarily on hydrogeologic conditions of the confining layers. The sign and magnitude of coseismic water-level change at a well varied with its distance from the fault. The distribution of coseismic water-level changes induced by the Chi-Chi earthquake indicates that water-level rise predominated in most of the footwall area, whereas water-level fall prevailed in a narrow zone adjacent to the fault trace. Manuscript received 31 October 2000.

Fault Detection and Identification in an IM270 Gas Turbine Using Measurements for Engine Control

A unique fault detection and identification algorithm using measurements for engine control use is presented. The algorithm detects an engine fault and identifies the associated component, using a gas path analysis technique with a detailed nonlinear engine model. The algorithm is intended to detect steplike changes in component performance rather than gradual change of all components. Component performance deviation (efficiency and flow rate) is represented by a magnitude and a phase. The phase is selected to minimize the error of evaluation matrices. Then the magnitude is computed. By utilizing operational data of the IM270 engine, the compressor and the turbine performance deviation was quantitatively identified.

Micromagnetic Study of Domain Wall-Pinning Characteristics With Step-Like Thickness Change in Thin Film

The pinning characteristics of a domain wall with a step-like thickness change along the wall is investigated in 0.15- to 0.5-/spl mu/m-thick films with an in-plane anisotropy using micromagnetic simulation based on the Landau-Lifshitz-Gilbert equation. The asymmetric Bloch wall having the structure in which the magnetostatic coupling develops between spins near the step when the wall is pinned shows the bi-directional pinning effect for magnetic fields applied along the magnetic domain. The wall energy of the pinned wall decreases with increasing step depth due to the largely decrease of the exchange energy component. The depinning field for the negative applied fields which drive the wall in the direction of the nongrooved region (thick film region) is considerably larger than that for the positive ones which drive the wall in the direction of the grooved region (thin film region). The depinning fields for both the positive and negative applied fields increase with decreasing film thickness.

Structures and electromagnetic properties of the A-site disordered Ba-based manganites; R0.5Ba0.5MnO3 (R = Y and rare earth elements)

The discovery of novel structural and physical properties in the A-site ordered manganite RBaMn2O6 (R = Y and rare earth elements) has demanded new comprehension about perovskite manganese oxides. In the present study, the A-site disordered form, R0.5Ba0.5MnO3, was successfully synthesized and investigated in the structure and electromagnetic properties. R0.5Ba0.5MnO3 has a primitive cubic perovskite cell. The magnetic glassy states are unexpectedly dominant as the ground state of R0.5Ba0.5MnO3 in contrast to the ordinary disordered manganite R0.5A0.5MnO3 (A = Sr and Ca). A peculiar behavior that is the steplike ultrasharp magnetization and resistivity change has been observed in Pr0.5Ba0.5MnO3.

Two-step photo-induced phase transitions in a two-sublattice model

As an effective model for the two-step spin transition, we study a two-sublattice spin model that takes into account intra-site antiferromagnetic and inter-site ferromagnetic couplings. Due to the competition between these couplings, the temperature dependence of the high spin fraction shows a two-step transition. We perform Monte Carlo (MC) simulations including a photoexcitation term. The MC dynamics of the high spin fraction shows non-linear characteristics such as step-like changes, threshold-like behavior, and phase separation.

Nondestructive evaluation of micrometric diamond films with an interferometric picosecond ultrasonics technique

Synthetic diamond thin or thick films are suitable materials for many applications because of their weak friction coefficient and their large hardness, Young modulus, and thermal conductivity. A series of diamond thin films of variable quality obtained by plasma-assisted chemical vapor deposition lying on titanium alloy substrates has been studied by picosecond ultrasonics. Femtosecond laser pulses allow the generation and detection of picosecond acoustic pulses that can be used to study the elastic properties of thin micrometric and submicrometric films. Acoustic fields generated in the substrate and propagating in the transparent diamond film are detected by an interferometric technique; they give rise to oscillations and abrupt step-like changes in the transient reflectivity variations. An analysis of these different features allows the determination of various characteristics of these films, such as longitudinal elastic constant, thickness, and roughness in terms of the diamond quality.

Changes in groundwater level associated with the 2003 Tokachi-oki earthquake

Groundwater level and flow rate at 44 wells are continuously observed by the Geological Survey of Japan and the Shizuoka and Gifu Prefectural Governments for monitoring seismic and volcanic activities. The 2003 Tokachi-oki earthquake (M8.0) occurred off the south coast of Hokkaido Island, Japan on September 26, 2003. The epicentral distance to the nearest observation well is about 250 km and that to the farthest is about 1200 km. At the 22 wells, we detected changes in groundwater level or flow rate in relation to the earthquake. Most of the changes are coseismic step-like changes and/or short-period oscillations. In the nearest two observation wells, long-period oscillations with the periods of 39 and 53 minutes were also observed for several days after the earthquake, which is likely due to tsunami. In comparison between distributions of changes in groundwater level and theoretical coseismic strain by the fault model, it is clear that step-like increases were found in the contraction area of the coseismic strain. The relationship between amounts of the observed step-like groundwater-level changes and theoretical ones, calculated by the fault model using strain sensitivities of groundwater level indicates that the groundwater levels in the several wells responded to the coseismic strain.

導電性セラミック材料 Ａサイト秩序型／無秩序型ペロブスカイトＭｎ酸化物ＲＢａＭｎ２Ｏ６／Ｒ０．５Ｂａ０．５ＭｎＯ３の構造と物性

The structures and electromagnetic properties of A-site ordered/disordered perovskite manganites, RBaMn2O6/R0.5Ba0.5MnO3(R=Y and rare earth elements), have been investigated. RBaMn2O6 exhibits remarkable features; (1) the charge/orbital order (CO) transition at relatively higher temperatures far above 300K, (2) a new stacking variation of the CE-type CO with a 4-fold periodicity along the c-axis, (3) the presence of structural transition possibly accompanied by dx2-y2 orbital order, (4) electronic phase separation. These novel structural and electromagnetic properties are discussed in terms of the structural characteristic that the MnO2 square sub-lattice is sandwiched by two types of rock-salt layers, RO and BaO with different lattice sizes, which introduces a strong frustration to the MnO2 sub-lattice. In R0.5Ba0.5MnO3 with a primitive cubic perovskite cell, on the other hand, the magnetic glassy states are dominant as the ground state. A peculiar behavior, the steplike ultrasharp magnetization and resistivity changes, has been observed in Pr0.5Ba0.5MnO3.

Abrupt changes and hysteretic behavior of90°domains in epitaxial ferroelectric thin films with misfit dislocations

The influence of misfit dislocations on the statics and dynamics of 90° domains (twins) in epitaxial thin films is studied theoretically. The misfit dislocations create additional potential barriers, which hinder the movements of domain walls along the film/substrate interface. For ferroelastic 90° walls, these barriers are considerable because an elastic interaction exists between 90° domains and misfit dislocations owing to the coupling of the dislocation stresses to the spontaneous strains generated at the proper or improper ferroelastic phase transition. The energy of elastic interaction is evaluated for a single 90° domain embedded into a tetragonal film containing a periodic array of edge misfit dislocations. On this basis. the equilibrium width of a single embedded 90° domain is calculated as a function of the misfit strain in the film/substrate systems. It is found that, at some threshold values of the misfit strain, the gradual variation of the domain width is interrupted by steplike changes. The evolution of the 90° domain pattern during the polarization switching in ferroelectric films with misfit dislocations is analyzed in detail. The calculations show that the electric-field-induced growth of an embedded 90° domain involves three different stages. Remarkably, at some critical value of the applied electric field, one of the 90° domain walls jumps over the neighboring misfit dislocation, which is accompanied by abrupt changes of the domain width and position in the film. The steplike movements of 90° domain walls over the misfit dislocations are proposed as a possible microscopic mechanism of the Barkhausen effect occurring in ferroelectric thin films during the polarization reversal. The hysteretic behavior of 90° domains at the cyclic variation of an applied electric field is also demonstrated.

Modeling Confined Fluids: An NhPT Molecular Dynamics Method

We present an NhPT MD method developed for systematic investigation of both the structural and dynamical properties of confined fluids without resorting to chemical potential or explicit reservoir. This method allows confined fluids to expand or contract transversely and the same number of fluid molecules to be simulated throughout all surface separations. Its first implementation using confined Lennard-Jones fluid yields step-like changes in surface density, layered configurations, in-plane ordering, and oscillatory perpendicular pressures and transverse diffusivities that are consistent with previous studies. Additionally, a pseudo-Poisson's ratio and transverse isothermal compressibility were calculated. Like other properties, they oscillate at smaller surface separations and approach constant values when the surface separation becomes sufficiently large. The limiting value of the pseudo-Poisson's ratio is interestingly equivalent to that of incompressible continua.

Discrete electron forces in a nanoparticle-tunnel junction system

According to the “orthodox” model for single electron tunneling, sudden changes in current–voltage characteristics of nanoparticle (NP)-tunnel junction (TJ) systems [“Coulomb blockade” (CB) and “Coulomb staircase” (CS) phenomena] arise fundamentally due to charge quantization. We have embedded NPs (∼2.5 nm in diameter) in the TJ of a hybrid scanning tunneling-atomic force microscope and have simultaneously measured current and forces generated in the system. We discuss an application to micromechanical switching actuated by single electrons. We also show that CB and CS phenomena are in fact associated with steplike changes in force, directly confirming the discrete charge nature of the phenomena.

Glass transition phenomena in the crystalline phase of hexa-substituted benzenes

Some hexa-substituted benzenes are known to exhibit molecular rotation in their crystalline phase, but this phenomenon is not very well understood. In this context, we have critically examined two materials, namely pentachloronitrobenzene and 2,3,4,5,6-pentabromotoluene over a wide range of temperatures, using dielectric spectroscopy and differential scanning calorimetry (DSC) to ascertain the nature of the above said relaxation. A relaxation process is found in the crystalline phase, which is slightly non-Arrhenius in its temperature dependence in the former and deviation from Debye behavior has been found in both the samples. This behavior is similar to that of the primary (or α-) relaxation found in glass forming materials. This phenomenon is found to correspond to a steplike (small) change in the specific heat in the DSC measurements indicating that it is a glass transition phenomenon. The sub-Tg relaxation data do not indicate any secondary (or β-) process (of measurable magnitude). However, the same materials when studied in small quantities in the liquid matrix of o-terphenyl (nonpolar) indicated a considerable magnitude for the β-process of molecules even below the liquid Tg of these mixtures. The results are discussed in the context of the glass transition phenomena of the above materials.

Local permeability studies of vortex states in Bi2Sr2CaCu2O8+y under tilted fields

AC local permeability is measured for a strongly anisotropic superconductor Bi2Sr2CaCu2O8+y under tilted fields. In addition to the peak in local permeability at the vortex-lattice melting transition, step-like change accompanied by hysteresis is observed under large and nearly constant in-plane field. This anomaly naturally extrapolates to the novel peak effect reported by Ooi et al. [Phys. Rev. B 63 (2001) 020501] at low temperatures under tilted fields. This observation indicates that the vortex solid phase in the crossing-lattices state changes into a new state with less shielding in the presence of dense Josephson vortices before melting into vortex liquid.

Magnetic and Mössbauer spectral study of ErFe11Ti and ErFe11TiH

X-ray diffraction, isothermal magnetization at 5 and 300 K, ac magnetic susceptibility measurements between 5 and 200 K, and iron-57 Mössbauer spectral measurements between 4.2 and 295 K have been carried out on ErFe11Ti and ErFe11TiH. Hydrogen uptake has been measured by gravimetric analysis and the insertion of hydrogen into ErFe11Ti increases its magnetization, magnetic hyperfine fields, and isomer shifts as a result of the associated lattice expansion. Peaks and steplike changes in both the real and imaginary components of the ac magnetic susceptibility are observed at ∼50 and 40 K for ErFe11Ti and ErFe11TiH, respectively, and are assigned to spin-reorientation transitions resulting from the temperature dependence of the sixth-order Stevens crystal-field term of erbium. The Mössbauer spectra have been analyzed with a model which considers both these spin reorientations and the distribution of titanium atoms in the near-neighbor environment of the three crystallographically distinct iron sites. The assignment and the temperature dependencies of the hyperfine fields and isomer shifts are in complete agreement with the Wigner–Seitz cell analysis of the three iron sites in ErFe11Ti and ErFe11TiH. The changes in the hyperfine field and isomer shift with the number of titanium near neighbors of the three iron sites are in agreement with the values observed for related titanium–iron intermetallic compounds.

Subionospheric VLF perturbations associated with lightning discharges

The use of very-low frequency (VLF) transmissions propagating inside the waveguide formed by the Earth and the lower ionosphere is a well developed technique for probing conditions within the waveguide. This paper seeks to review the current understanding of lightning discharge associated processes that lead to changes in the characteristics of the waveguide and thus variations in the received phase and/or amplitude of VLF transmissions. Particular emphasis is placed upon events which appear to be produced directly by lightning discharge processes. These include VLF sprites and early Trimpi for which significant research efforts have been made over the last 10 years. The properties and interpretation of these events are discussed in detail. QE-field produced early Trimpi are due to relatively large disturbed regions (horizontal extent ∼100 km ) in the lower ionosphere. VLF sprites are produced by red sprite discharges, leading to relatively small, dense, ionospheric modifications made up of fine-scale horizontal structures (∼300 m) that stretch over wide altitude ranges (⩽50– 80 km ). Differences in the ionospheric modifications electron temperatures and ionisation structure produces the differing delay times and scattering patterns in the experimentally observed VLF perturbations. Lightning-EMP produced Elves lead to large (∼500 km) , relatively smoothly varying ionospheric disturbance at high altitudes (∼85 km) . Such a modification should create sudden step-like changes in received VLF amplitude and phase that lack a clear relaxation signature and occur along narrow forward-scattered directions. The VLF techniques described in this article are part of the larger field of research into high-altitude processes connected with thunderstorms. Lightning EMP produces a large (∼500 km) , relatively smoothly varying ionospheric disturbance at high altitudes (∼85 km) .

Conformation of poly(l-glutamic acid) in bipolar amphiphiles with alkyl ammonium cations of different hydrophobicity

The conformation of the sodium salt of poly(l-glutamic acid) (P(Glu)) in solutions of the cationic bipolar amphiphile 1, 20-isosanediylbis(alkylammonium chloride) (C20(RA)2) with different alkyl head groups as a function of amphiphile concentration was investigated using circular dichroism (CD). RA included methylammonium (MA), ethylammonium (EA), propylammonium (PA), butylammonium (BA), and pentylammonium (PeA) cationic groups. The CD spectrum of each C20(RA)2 had a double minima corresponding to the α-helix of P(Glu), which was replaced by CD spectra with a single minimum at wavelengths larger than 222 nm as concentration increased. These changes in the CD spectrum were ascribed to the conformational change from random coil to α-helix and to aggregates of helices. In C20(EA)2 solutions, a step-like change in the CD intensity was observed at 222 nm as a function of the ratio of C20(RA)2 to P(Glu). At the step, the CD spectrum of the complete α-helix was observed. At 10–35 °C, an α-helix was induced in P(Glu) in the order: C20(EA)2>C20(MA)2>C20(PA)2>C20(BA)2>C20(PeA)2. This order was ascribed to the best fit of ethylammonium to the P(Glu) side chain.

Numerical Simulation of Torsional Shear Flow between Concentric Parallel Disks of Nematic Liquid Crystals

Numerical simulation of nematic liquid crystalline flow between rotating parallel disks has been performed using the Leslie-Ericksen continuum theory. It is assumed that the director lies in the shear plane and that the velocity profile is linear in the gap direction of the two disks. For a tumbling-type liquid crystal both the two-dimensional analysis and the Carlsson and Skarp model, in which molecular field elasticity in the radial direction is ignored, can predict step-like changes of the director orientation angles in the radial direction at high Ericksen numbers. The orientation angles are predicted to be discontinuous at tumbling regions for the Carlsson and Skarp model, whereas they are continuous for the two-dimensional analysis. A peculiar behavior observed in a light intensity experiment reported by Carlsson et al. That dark rings move from the disk periphery to its center is satisfactorily simulated by the two-dimensional analysis.

Nanostructured Oxide Films for High-Speed Humidity Sensors

ABSTRACTMiniaturized thin film humidity sensors were fabricated using nanostructured materials deposited by an advanced technique known as glancing angle deposition (GLAD). These sensors exhibited extremely fast desorption response times of less than 40 ms to steplike changes in humidity. Multiple response time measurements for various initial humidities have shown that the sensors maintain their rapid response at all levels of humidity.

Assembly of asphaltene molecular aggregates as studied by near-UV/visible spectroscopy: I. Structure of the absorbance spectrum

The aim of this paper is to provide new data on the properties of molecular aggregation in toluene solutions of crude oils and of solid asphaltenes. The shape of the optical absorption spectrum was found to be sensitive to the details of asphaltene aggregation processes. In dilute solutions, these processes are apparently determined by the net concentrations of asphaltenes; other oil constituents play a secondary role. Our experimental data indicate that molecular solutions of asphaltenes are possible only for concentrations below 1 mg/l. With increasing asphaltene content, more and more complex molecular aggregates are formed. In particular, asphaltene dimers evidently are the predominant species in the range of 5–15 mg/l, while stable “nanocrystallites” (dimer pairs) are predominant at concentrations ≈90 mg/l. Aggregates at higher concentrations may be viewed as assemblies of such “crystallites”. The observed gradual aggregation process is distinct from conventional micellisation phenomena with step-like changes at critical micelle concentrations (CMCs).

FISDW in quasi-one dimensional organic conductors with the dimerized gap due to anion ordering

Magnetoresistance and Hall resistance measurements have been carried out in the FISDW phase of deuterated (TMTSF)2C1O4 for various cooling rates through the anion ordering temperature. The Hall resistance in the intermediate cooled state, observed a very stable quantum Hall state above 9.0 T for slowly cooled, shows a step-like change from the phase between 10 and 17 T to the phase between 20 and 25 T with hysteresis between 14 and 21 T. This result suggests that there is a new phase transition around 15 T in deuterated (TMTSF)4ClO4. A possible ground state of the FISDW phase of (TMTSF)2C1O4 for various cooling rates is discussed from the viewpoint of the peculiar SDW nesting vector stabilized by the dimerized gap due to anion ordering.