Explicit integration of bounding surface model for the analysis of earthquake soil liquefaction

This paper presents a new plasticity model developed for the simulation of monotonic and cyclic loading of non‐cohesive soils and its implementation to the commercial finite‐difference code FLAC, using its User‐Defined‐Model (UDM) capability. The new model incorporates the framework of Critical State Soil Mechanics, while it relies upon bounding surface plasticity with a vanished elastic region to simulate the non‐linear soil response. Stress integration of constitutive relations is performed using a recently proposed explicit scheme with automatic error control and substepping, which so far has been employed in the literature only for constitutive models aiming at monotonic loading. The overall accuracy of this scheme is evaluated at element level by simulating cyclic loading along complex stress paths and by using iso‐error maps for paths involving change of the Lode angle. The performance of the new constitutive model and its stress integration scheme in complex boundary value problems involving earthquake‐induced liquefaction is evaluated, in terms of accuracy and computational cost, via a number of parametric analyses inspired by the successful simulation of the VELACS centrifuge Model Test No. 2 studying the lateral spreading response of a liquefied sand layer. Copyright © 2009 John Wiley & Sons, Ltd.     

Travel time controls the magnitude of nitrate discharge in groundwater bypassing the riparian zone to a stream on Virginia's coastal plain

Groundwater that bypasses the riparian zone by travelling along deep flow paths may deliver high concentrations of fertilizer‐derived NO₃^? to streams, or it may be impacted by the NO₃^? removal process of denitrification in streambed sediments. In a study of a small agricultural catchment on the Atlantic coastal plain of Virginia's eastern shore, we used seepage meters deployed in the streambed to measure specific discharge of groundwater and its solute concentrations for various locations and dates. We used values of Cl^? concentration to discriminate between bypass water recharged distal to the stream and that contained high NO₃^? but low Cl^? concentrations and riparian‐influenced water recharged proximal to the stream that contained low NO₃^? and high Cl^? concentrations. The travel time required for bypass water to transit the 30‐cm‐thick, microbially active denitrifying zone in the streambed determined the extent of NO₃^? removal, and hydraulic conductivity determined travel time through the streambed sediments. At all travel times greater than 2 days, NO₃^? removal was virtually complete. Comparison of the timescales for reaction and transport through the streambed sediments in this system confirmed that the predominant control on nitrate flux was travel time rather than denitrification rate coefficients. We conclude that extensive denitrification can occur in groundwater that bypasses the riparian zone, but a residence time in biologically active streambed sediments sufficient to remove a large fraction of the NO₃^? is only achieved in relatively low‐conductivity porous media. Instead of viewing them as separate, the streambed and riparian zone should be considered an integrated NO₃^? removal unit. Copyright © 2011 John Wiley & Sons, Ltd.     

单自由度二阶线性系弘在各种输入函数（或实际波形）作用下的响应

The response problem of second-order linear system with single freedom degree is solved by positive and inverse Fourier transform and dynamic waveform inversion method. Several expressions of tipicel waveforms and a measured practical waveform are calculated, and the results are satisfying.     

On-line estimation of nonlinear physical systems

Recursive algorithms for estimating states of nonlinear physical systems are presented. Orthogonality properties are rediscovered and the associated polynomials are used to linearize state and observation models of the underlying random processes. This requires some key hypotheses regarding the structure of these processes, which may then take account of a wide range of applications. The latter include streamflow forecasting, flood estimation, environmental protection, earthquake engineering, and mine planning. The proposed estimation algorithm may be compared favorably to Taylor series-type filters, nonlinear filters which approximate the probability density by Edgeworth or Gram-Charlier series, as well as to conventional statistical linearization-type estimators. Moreover, the method has several advantages over nonrecursive estimators like disjunctive kriging. To link theory with practice, some numerical results for a simulated system are presented, in which responses from the proposed and extended Kalman algorithms are compared.     

Fe2+-Ti4+ charge transfer in stoichiometric Fe2+,Ti4+-minerals

Optical absorption spectra are presented for taramellite, traskite and neptunite, all of which have both Fe²⁺ and Ti⁴⁺ as major elements. The spectra of each of these minerals are dominated by a single, intense absorption band in the 415 to 460 nm region with 7000 to 9000 cm^?1 halfwidth. These transitions, assigned to Fe²⁺-Ti⁴⁺ intervalence charge transfer, showed little difference in intensity at 80 and 300 K and have molar absorptivities which range from ～100 to ～1300 M^?1 cm^?1. The Fe²⁺-Ti⁴⁺ absorptions in these standards generally compare well to other mineral spectra in which Fe²⁺ — Ti⁴⁺ intervalence absorption has previously been proposed with the exception of the most cited example, blue corundum.     

Variational stabilization of the ionic charge densities in the electron-gas theory of crystals: Applications to MgO and CaO

The electron-gas theory of crystals is extended to include the effects of many-body forces that arise from both electrostatic and overlap interactions. These effects are incorporated through a self-consistent spherical relaxation of the ionic charge distributions such that the crystal binding energy is minimized. This variational model is used to compute the elastic constants and equations of state of MgO and CaO, and we compare its results to those derived from earlier electron-gas models. In the variational model, the anion charge distributions are markedly more sensitive to the local crystal environment than they are in the PIB or other electron-gas models. We find that for these oxides the variational model gives the best overall agreement with experiment for lattice constants, equations of state, dissociation energies, and elastic moduli.     

关于氡测量标定装置(氡室)和测量单位的统一

本文介绍了作者研制的8505—I型氡室,该氡室可用于准确和快速标定多种测氡装置。作者提出了相应的标定方法,并测定了野外常用的10种氡探测器的标定系数。根据法定计量单位选用了贝克(Bq)和贝克/升(Bq/L)。相应作为各种氡测量的[放射性]活度单位和氡浓度单位。     

Collapsibility and deformation characteristics of deep-seated loess in China

Lin, Z.G. and Wang, S.J., 1988. Collapsibility and deformation characteristics of deep-seated loess in China. Eng. Geol., 25: 271–282.

As part of a comprehensive research program, laboratory tests were conducted on samples of deep-seated loess from different locations of the loessial regions of northern China, including Shaanxi, Gansu, Shanxi and Honan Provinces. The information thus acquired on some aspects of the engineering properties of the samples, such as the unit collapse-pressure relationships, the initial collapse pressure versus the “preconsolidation pressure” and deformation–pressure characteristics, is interesting and may prove useful to geotechnical engineers who work on projects on water-poor plateaux or high river terraces in loessial regions throughout the world.     

Organic geochemical analysis of environments of Dongpu Basin

Six types of “molecular fossil” indicators are summarized, by which the sources of organic matter (OM) in the sedimentary rocks of the Lower Tertiary Shahejie Formation in the Dongpu Basin can be traced and the redox and paleosalinity conditions restored.     

Effects of Initial Stresses in Tailored Pulse Loading Method

Based on the mechanism study of new well stimulation method—tailored pulse loading method, the effects of initial stresses in this method is further studied. The effects of initial stresses on the propagation velocities and directions of the cracks around a hole, especially on the energy dissipation in crack extension, are obtained through theoretical analysis, dynamic photo elasticity tests, high speed photography. And large coal specimen tests. These results provide a theoretical foundation for the practical applications of the tailored pulse loading method.