Transient tunneling effects of resonance doublets in triple barrier systems

Transient tunneling effects in triple barrier systems are investigated by considering a time-dependent solution to the Schr\"{o}dinger equation with a cutoff wave initial condition. We derive a two-level formula for incidence energies $E$ near the first resonance doublet of the system. Based on that expression we find that the probability density along the internal region of the potential, is governed by three oscillation frequencies: one of them refers to the well known Bohr frequency, given in terms of the first and second resonance energies of the doublet, and the two others, represent a coupling with the incidence energy $E$. This allows to manipulate the above frequencies to control the tunneling transient behavior of the probability density in the short-time regim

Three Recent Damaging Earthquakes in Mexico

Seismicity in Mexico is largely influenced by subduction earthquakes that originate along much of its Pacific Coast. These events have recurrently damaged Mexico City but other less frequent earthquakes produced by other sources and mechanisms also contribute to seismic hazard there and have damaged other important cities and towns. In this paper we review, from the point of view of geotechnical engineering, the effects of three of these less frequent events: the Manzanillo earthquake of Octobrer 9, 1995, the Tehuacán Earthquake of June 6, 1999 and the Tecomán Earthquake of January 21, 2003

A-branes, foliations and localization

This paper studies a notion of enumerative invariants for stable $A$-branes,and discusses its relation to invariants defined by spectral and exponentialnetworks. A natural definition of stable $A$-branes and their counts isprovided by the string theoretic origin of the topological $A$-model. This isthe Witten index of the supersymmetric quantum mechanics of a single $D3$ branesupported on a special Lagrangian in a Calabi-Yau threefold. Geometrically,this is closely related to the Euler characteristic of the $A$-brane modulispace. Using the natural torus action on this moduli space, we reduce thecomputation of its Euler characteristic to a count of fixed points viaequivariant localization. Studying the $A$-branes that correspond to fixedpoints, we make contact with definitions of spectral and exponential networks.We find agreement between the counts defined via the Witten index, and the BPSinvariants defined by networks. By extension, our definition also matches withDonaldson-Thomas invariants of $B$-branes related by homological mirrorsymmetry.<br

Liquefaction of the Enmedio Island Soil Deposits

The results of field testing and of simplified liquefaction analyses of the Enmedio Island soil deposits are presented and discussed in this paper. It is found that for this case history simple criteria for assessing liquefaction potential yield results in accord with field behavior

An Experimental Study to Assess the Shear Modulus Degradation by Fatigue of Mexico City Clay

In this research, the degradation by fatigue of Mexico City clay is studied using a triaxial equipment where the cyclic stress amplitude was maintained constant during the experiment. The variables considered in the study were the following: state of the soil, effective mean confining stress, magnitude of cyclic stress and number of loading cycles. Undisturbed samples, anisotropically and isotropically consolidated, were subjected to cyclic loading for this purpose. When analyzing the cyclic stress-strain response with the number of cycles a threshold of permanent deformation in function of the cyclic deviator stress and axial strain was found. When the cyclic strain exceeds this distinctive value the rate of permanent (plastic) deformations accumulate faster. For practical applications of computing permanent deformations in Mexico City a simplified method is proposed. This method considers the above threshold and a hyperbolic model to represent the cyclic response in Mexico City clays

Ground Movements in Mexico City During Recent Earthquakes

Acceleration records were obtained with a rather dense accelerographic array during three recent earthquakes in Mexico City. Following a purely observational approach, useful information about the nature and characteristics of seismic motions was derived from the analysis of these records. Broad regional studies indicate that the distribution of seismic motions in the city may be affected by directivity effects. From local site studies it is concluded that seismic movements at the base of the compressible clay deposits are fairly uniform and accelerograms recorded in vertical arrays suggest that soil strata in Mexico City respond to seismic movements according to established knowledge

Dynamic Behavior of Tailings

This article presents results of samples tested on a resonant column apparatus. The samples were formed of soil coming from mining residues (tailings), the testing program makes emphasis in the variables that influence the behavior. Finally, the interpretation of the results is made with a knowledge-based procedure and a Masing type model

Observed and Predicted Liquefaction of a Sand Stratum

Field observations and preliminary studies had led to the conclusion that the sand stratum liquefied only in a limited area during the March 14, 1979 earthquake. Further field studies revealed the presence of the sand layer throughout the Enmedio Island. This fact raised questions as to whether the sand liquefied or not in the whole area. To clarify this question, a research program which included cyclic triaxial testing and numerical analyses was undertaken. The results of this study show that the sand layer did liquefy through the Island; however, due to differences in stratigraphic characteristics, superficial signs of liquefaction were developed only in a restricted zone

Drift of particles in self-similar systems and its Liouvillian interpretation

We study the dynamics of classical particles in different classes of spatially extended self-similar systems, consisting of (i) a self-similar Lorentz billiard channel, (ii) a self-similar graph, and (iii) a master equation. In all three systems the particles typically drift at constant velocity and spread ballistically. These transport properties are analyzed in terms of the spectral properties of the operator evolving the probability densities. For systems (i) and (ii), we explain the drift from the properties of the Pollicott-Ruelle resonance spectrum and corresponding eigenvectorsComment: To appear in Phys. Rev.

Analysis of Some Downhole Acceleration Records from Central De Abasto Oficinas Site at Mexico City

The surface and downhole accelerations records of “Central de Abasto Oficinas (CAO)” array at Mexico City, have been analyzed to determine the soil stiffness as a function of shear strain amplitude. The 09/10/95 seismic event (NS component) has been used for this purpose. The shear stress-strain histories have been evaluated directly from the field downhole acceleration records, employing a technique of system identification, and used to obtain the variation of shear modulus with shear strain amplitude. A shear-beam model, calibrated by the identified properties, is found to represent the site dynamic response characteristics. The results have been compared with values obtained in previous investigations from field and laboratory tests