The paradox of smooth and abrupt bends in two-dimensional in-plane shear-crack mechanics

It is pointed out, in the context of the boundary integral equation method (BIEM), that, in the mechanics of 2-D curved in-plane shear cracks, a smooth curve, along which the crack orientation changes continuously, and an abrupt kink, across which it changes discontinuously, are not equivalent to each other. The discrepancy is illustrated by numerical results, and a set of conceptual models is used to demonstrate analytically how the equations that govern the crack mechanics have inherently distinct forms depending on whether the crack orientation changes continuously or abruptly across a bend, as long as one abides by the principles of linear elasticity theory. This has serious implications for the numerical treatment of a curved crack, which can be modelled as a chain of finite elements that are connected either smoothly or at abrupt kinks, the two methods producing different numerical outcomes. No similar paradox arises in the cases of anti-plane shear or open in-plane cracks.     

Expansion of the Nishinomiya Built Environment Database

The Nishinomiya Built Environment Database, which can be used to analyze the disaster process of the 1995 Hanshin-Awaji Earthquake Disaster in Nishinomiya City, has been expanded with new data entries. The database contains the following very detailed datasets: (1) the urbanization area base map, (2) casualty data, (3) three sets of building damage data surveyed by the Nishinomiya City, the Architectural Institute of Japan and the City Planning Institute of Japan, and the Kobe University, (4) building property data based on the real estate tax roll, (5) photographs of the damaged buildings with the information on the place and orientation of the picture, and (6) the estimated distribution of the seismic ground motion. The seismic ground motion was simulated for the southern part of Nishinomiya City and two verification sites in Kobe City and Amagasaki City. In the simulation, the borehole data of public facilities were used to model the surface soils as one-dimensional layers, taking into consideration the fact that the spatial distribution of the sediment/basement interface forms a slope. The model of the fault rupture process simulated the characteristics of the seismic motion at basement level, and amplification effects of the surface layers were evaluated based on multiple reflection theory. The distribution of peak ground acceleration and peak ground velocity was estimated from acceleration response spectra at each borehole point. In addition, the relationship between simulated seismic ground motion and building damage was studied based on newly proposed band-passed spectrum intensity using the expanded database. This confirmed that detailed categorization is necessary in order to evaluate the fragility functions, especially for reinforced concrete structures. The database should provide fundamental information for identifying the relationship between the ground motions and the extent and pattern of building damage, or the pattern of the occurrence of casualties.Presently     

Fine structure in photoluminescence spectrum of S<Subscript>2</Subscript><Superscript>−</Superscript> center in sodalite

The photoluminescence and excitation spectra of sodalites from Greenland, Canada and Xinjiang (China) are observed at 300 and 10 K in detail. The features of the emission and excitation spectra of the orange-yellow fluorescence of these sodalites are independent of the locality. The emission spectra at 300 and 10 K consist of a broad band with a series of peaks and a maximum peak at 648 and 645.9 nm, respectively. The excitation spectra obtained by monitoring the orange-yellow fluorescence at 300 and 10 K consist of a main band with a peak at 392 nm. The luminescence efficiency of the heat-treated sodalite from Xinjiang is about seven times as high as that of untreated natural sodalite. The emission spectrum of the S₂ ⁻ center in sodalite at 10 K consists of a band with a clearly resolved structure with a series of maxima spaced about 560 cm⁻¹ (20–25 nm) apart. Each narrow band at 10 K shows a fine structure consisting of a small peak due to the stretching vibration of the isotopic species of ³²S³⁴S⁻, a main peak due to that of the isotopic species of ³²S₂ ⁻ and five peaks due to phonon sidebands of the main peak.     

Pore Creation due to Fault Slip in a Fluid-permeated Fault Zone and its Effect on Seismicity: Generation Mechanism of Earthquake Swarm

—Spatio-temporal variation of rupture activity is modeled assuming fluid migration in a narrow porous fault zone formed along a vertical strike-slip fault in a semi-infinite elastic medium. Pores are assumed to be created in the fault zone by fault slip. The effective stress principle coupled to the Coulomb failure criterion introduces mechanical coupling between fault slip and pore fluid. The fluid is assumed to flow out of a localized high-pressure fluid compartment in the fault with the onset of earthquake rupture. The duration of the earthquake sequence is assumed to be considerably shorter than the recurrence period of characteristic events on the fault. The rupture process is shown to be significantly dependent on the rate of pore creation. If the rate is large enough, a foreshock–mainshock sequence is never observed. When an inhomogeneity is introduced in the spatial distribution of permeability, high complexity is observed in the spatio-temporal variation of rupture activity. For example, frequency-magnitude statistics of intermediate-size events are shown to obey the Gutenberg–Richter relation. Rupture sequences with features of earthquake swarms can be simulated when the rate of pore creation is relatively large. Such sequences generally start and end gradually with no single event dominating in the sequence. In addition, the b values are shown to be unusually large. These are consistent with seismological observations on earthquake swarms.     

Coupled process-based cyclone surge simulation for the Bay of Bengal

We have developed a wind-wave-surge coupled process-based numerical model for simulating storm surge, consisting of a meso-scale atmospheric model (MM5), a third-generation spectral wave model (WW3) and a coastal ocean model (POM). We introduced an additional sea surface shear stress by wave dissipation into the model to consider the process of energy transfer from winds to currents through whitecap breaking. We demonstrate the importance of this energy transfer path through a hindcast simulation of a cyclone surge in April, 1991 in the Bay of Bengal: it helps generate mean current and has wave effects on wind-induced current fields in extremely shallow water areas.     

Electrical conduction and polarization of calcite single crystals

The electrical conductivity and polarization properties of calcite single crystals with three orientations, namely, a (00.1) plane perpendicular to the crystallographic c axis (10.0) plane parallel to the crystallographic c axis, and a (10.4) cleavage plane, were studied by both complex impedance and thermally stimulated depolarization current (TSDC) measurements. Conductivities for (00.1)-, (10.0)-, and (10.4)-oriented single calcite crystals at 400–600?°C were 1.16?×?10^?7?–?1.05?×?10^?5, 7.40?×?10^?8?–?4.27?×?10^?6, and 4.27?×?10^?7?–?2.86?×?10^?5 Ω^?1 m^?1, respectively, and the activation energies for conduction were 112, 103, and 101?kJ?mol^?1, respectively. The TSDC spectra verified the electrical polarizability of calcite crystals. The activation energy for depolarization, estimated from TSDC spectra, of the (00.1)-, (10.0)-, and (10.4)-oriented calcite substrates were 112, 119, and 114?kJ?mol^?1, respectively. Considering the correlation between the processes of conduction and electric polarization, we proposed the mechanisms of conduction and polarization in calcite on the assumption of oxide ion transport.     

Constraints on Vesta's elemental composition: Fast neutron measurements by Dawn's gamma ray and neutron detector

Surface composition information from Vesta is reported using fast neutron data collected by the gamma ray and neutron detector on the Dawn spacecraft. After correcting for variations due to hydrogen, fast neutrons show a compositional dynamic range and spatial variability that is consistent with variations in average atomic mass from howardite, eucrite, and diogenite (HED) meteorites. These data provide additional compositional evidence that Vesta is the parent body to HED meteorites. A subset of fast neutron data having lower statistical precision show spatial variations that are consistent with a 400 ppm variability in hydrogen concentrations across Vesta and supports the idea that Vesta's hydrogen is due to long‐term delivery of carbonaceous chondrite material.