Use of ergodic reasoning to reconstruct the historical range of variability and evolutionary trajectory of rivers   总被引：2，自引：0，他引：2  

Kirstie Fryirs  Gary J. Brierley  Wayne D. Erskine 《地球表面变化过程与地形》2012,37(7):763-773

Applications of ergodic reasoning (or location for time substitution) aid efforts at environmental reconstruction and prediction, providing a useful tool to analyse and communicate stages of landscape evolution. Analysis of the historical range of behaviour and change that a river system has experienced can be used to interpret thresholds that have been breached, and underlying controls and/or triggers for adjustment and change. This information can be used to forecast future trajectories of adjustment and provide target conditions for management activities. This paper uses a case study from upper Wollombi Brook, New South Wales, Australia to demonstrate how ergodic reasoning can be used to assess river behaviour, change and responses to natural and human‐disturbances. The ‘river evolution diagram’ developed by Brierley and Fryirs (Geomorphology and River Management: Applications of the River Styles Framework. Blackwell Publishing: Oxford, 2005) is presented as a means for depicting the range of behaviour and evolutionary variability of this river. These approaches can be readily applied in other systems. Implications for approaches to analysis of river evolution and management are outlined. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Advances in theory of plastic mechanism control: closed form solution for MR‐Frames          下载免费PDF全文

Rosario Montuori  Elide Nastri  Vincenzo Piluso 《地震工程与结构动力学》2015,44(7):1035-1054

In this paper new advances in the application of ‘Theory of Plastic Mechanism Control’ (TPMC) are presented. TPMC is aimed at the design of structures assuring a collapse mechanism of global type. The theory has been developed in the nineties with reference to moment‐resisting frames (MRFs) and progressively extended to all the main structural typologies commonly adopted as seismic‐resistant structural systems. In particular, the outcome of the theory is the sum of the plastic moments of the columns required, at each storey, to prevent undesired failure modes, i.e. partial mechanisms and soft‐storey mechanisms. The theory is used to provide the design conditions to be satisfied, in the form of a set of inequalities where the unknowns are constituted by the column plastic moments. This set of inequalities was originally solved by means of an algorithm requiring an iterative procedure. The advances presented in this paper are constituted by the identification of a ‘closed form solution’ and by the use of TPMC in a more systematic design approach. This result is very important, because the practical application of TPMC can now be carried out even with very simple hand calculations. The practical application of TPMC is herein presented with reference to the design of a multi‐storey frame whose pattern of yielding is validated by means of both push‐over analysis and incremental dynamic analyses. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Tests and model calibration of high‐strength steel tubular beam‐to‐column and column‐base composite joints for moment‐resisting structures          下载免费PDF全文

Raffaele Pucinotti  Nicola Tondini  Gabriele Zanon  Oreste S. Bursi 《地震工程与结构动力学》2015,44(9):1471-1493

Performance‐based engineering (PBE) methodologies allow for the design of more reliable earthquake‐resistant structures. Nonetheless, to implement PBE techniques, accurate finite element models of critical components are needed. With these objectives in mind, initially, we describe an experimental study on the seismic behaviour of both beam‐to‐column (BTC) and column‐base (CB) joints made of high‐strength steel S590 circular columns filled with concrete. These joints belonged to moment‐resisting frames (MRFs) that constituted the lateral‐force‐resisting system of an office building. BTC joints were conceived as rigid and of partial strength, whereas CB joints were designed as rigid and of full strength. Tests on a BTC joint composed of an S275 steel composite beam and high‐strength steel concrete‐filled tubes were carried out. Moreover, two seismic CB joints were tested with stiffeners welded to the base plate and anchor bolts embedded in the concrete foundation as well as where part of a column was embedded in the foundation with no stiffeners. A test programme was carried out with the aim of characterising these joints under monotonic, cyclic and random loads. Experimental results are presented by means of both force–interstory drift ratio and moment–rotation relationships. The outcomes demonstrated the adequacy of these joints to be used for MRFs of medium ductility class located in zones of moderate seismic hazard. Then, a numerical calibration of the whole joint subassemblies was successfully accomplished. Finally, non‐linear time‐history analyses performed on 2D MRFs provided useful information on the seismic behaviour of relevant MRFs. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Changes in animal activity prior to a major (M = 7) earthquake in the Peruvian Andes     

《Physics and Chemistry of the Earth》2015

During earthquake preparation geophysical processes occur over varying temporal and spatial scales, some leaving their mark on the surface environment, on various biota, and even affecting the ionosphere. Reports on pre-seismic changes in animal behaviour have been greeted with scepticism by the scientific community due to the necessarily anecdotal nature of much of the evidence and a lack of consensus over possible causal mechanisms. Here we present records of changes in the abundance of mammals and birds obtained over a 30 day period by motion-triggered cameras at the Yanachaga National Park, Peru, prior to the 2011 magnitude 7.0 Contamana earthquake. In addition we report on ionospheric perturbations derived from night-time very low frequency (VLF) phase data along a propagation paths passing over the epicentral region. Animal activity declined significantly over a 3-week period prior to the earthquake compared to periods of low seismic activity. Night-time ionospheric phase perturbations of the VLF signals above the epicentral area, fluctuating over the course of a few minutes, were observed, starting 2 weeks before the earthquake. The concurrent observation of two widely different and seemingly unconnected precursory phenomena is of interest because recently, it has been proposed that the multitude of reported pre-earthquake phenomena may arise from a single underlying physical process: the stress-activation of highly mobile electronic charge carriers in the Earth’s crust and their flow to the Earth’s surface. The flow of charge carriers through the rock column constitutes an electric current, which is expected to fluctuate and thereby emit electromagnetic radiation in the ultralow frequency (ULF) regime. The arrival of the charge carriers can lead to air ionization at the ground-to-air interface and the injection of massive amounts of positive airborne ions, known to be aversive to animals.  相似文献   

Littering dynamics in a coastal industrial setting: The influence of non-resident populations     

《Marine pollution bulletin》2014,81(1-2):179-185

We examined if there is truth to the preconceptions that non-resident workers (including FIFO/DIDO’s) detract from communities. We used marine debris to test this, specifically focussing on littering behaviour and evidence of awareness of local environmental programs that focus on marine debris. Littering was most common at recreational areas, then beaches and whilst boating. Twenty-five percent of respondents that admit to littering, reported no associated guilt with their actions. Younger respondents litter more frequently. Thus, non-resident workers litter at the same rate as permanent residents, visitors and tourists in this region, within this study. Few respondents are aware of the environmental programs that operate in their local region. Awareness was influenced by a respondent’s residency (non-residents are less aware), age, and level of education. To address this failure we recommend that industries, that use non-resident workers, should develop inductions that expose new workers to the environmental programs in their region.  相似文献   

Undrained behaviour of two silica sands and practical implications for modelling SSI in liquefiable soils     

《Soil Dynamics and Earthquake Engineering》2014

The aim of the present study is twofold. Firstly, the paper investigates the undrained cyclic and post-cyclic behaviour of two silica sands by means of multi-stage cyclic triaxial tests. Secondly, based on the post-cyclic response observed in the element test, the authors formulate a simplified stress–strain relationship that can be conveniently used for the construction of p–y curves for liquefiable soils. The multi-stage loading condition consists of an initial cyclic loading applied to cause liquefaction, followed by undrained monotonic loading that aimed to investigate the post-cyclic response of the liquefied sample. It was found that due to the tendency of the liquefied soil to dilate upon undrained shearing, the post-liquefaction strain–stress response was characterised by a distinct strain–hardening behaviour. The latter is idealized by means of a bi-linear stress–strain model, which can be conveniently formulated in terms of three parameters, i.e.: (i) take-off shear strain, γ_to, i.e. shear strain required to mobilize 1 kPa of shear strength; (b) initial secant shear modulus, G₁, defined as 1/γ_to; (c) post-liquefied shear modulus at large strain, G₂ (γ⪢γ_to). Based on the experimental results, it is concluded that these parameters are strongly influenced by the initial relative density of the sample, whereby γ_to decreases with increasing relative density. Differently both shear moduli (G₁ and G₂) increases with increasing relative density. Lastly, the construction of new p–y curves for liquefiable soils based on the idealized bi-linear model is described.  相似文献   

Trophic analysis of two species of Atopsyche (Trichoptera: Hydrobiosidae)     

María Celina Reynaga  Paola Rueda Martín 《Limnologica》2010,40(1):61-66

To compare the trophic niche of coexisting larvae of Atopsyche yunguensis and Atopsyche spinosa we analysed their gut contents and found little niche overlap: A. yunguensis fed primarily on Trichoptera and amorphous matter, whereas A. spinosa fed on Diptera. A. spinosa showed both a spatial range and a niche breadth larger than those of A. yunguensis. Behavioural observations on A. spinosa may emphasize the use of chelate anterior legs for securing preys. Both species have been included into the predator-clingers functional group.  相似文献   

Wal-Mart and Aldi: Two Retail Giants in Germany     

Ulrike?Gerhard  Barbara?HahnEmail author 《GeoJournal》2005,62(1-2):15-26

Wal-Mart entered the German market at the end of 1997 but is still running at a loss in its 92 stores. This article tests the hypothesis that there are two main reasons for Wal-Mart’s problems in Germany. First of all, Wal-Mart is competing against very strong and well established deep discounters, especially Aldi. Secondly, there is the difference between the so-called Wal-Mart culture and German customer values. So far, Wal-Mart has not managed to close this gap or create a positive image in Germany. The first part of the article describes the differences between the two retail companies Wal-Mart and Aldi, whereas the second part focuses on the consumer perspective. Four hundred people were interviewed on the phone about their shopping behaviour in the city of Würzburg (northern Bavaria, 140,000 inhabitants). This survey is part of an international study also undertaken in Canada, Great Britain and China.  相似文献   

A temperature-dependent single-crystal Raman spectroscopic study of fayalite: evidence for phonon-magnetic excitation coupling     

B. A. ?Kolesov  C. A. ?GeigerEmail author 《Physics and Chemistry of Minerals》2004,31(3):155-161

The polarized single-crystal Raman spectrum of synthetic fayalite, Fe₂SiO₄, was recorded between 5 and 773 K in order to investigate its lattice dynamic behavior. A broad absorption envelope is observed at wavenumbers between 800 and 960 cm^–1 and it contains two intense bands at 816 and 840 cm^–1 at 293 K in the (cc) spectrum. The integral area of the envelope decreases upon cooling from 293 K and reaches a minimum around 55 K. It then increases again with a further decrease in temperature down to 5 K. It is proposed that the envelope in the (cc) spectra consists of seven different modes, some of which are symmetry-forbidden, that arise from combination scattering of nonsymmetric internal SiO₄-stretching modes of B_ig symmetry (i = 1, 2, 3) and low-energy excitations. The individual modes can be observed under different polarizations and agree in number and wavenumber with those obtained by fitting the broad envelope with Lorentzians. An analysis of the Raman spectrum as a function of temperature, using the known magnetic properties of fayalite, allows the assignment of the low-energy excitations to short-range magnetic interactions. Modulation of the Fe²⁺(1)–Fe²⁺(2) exchange energy leads to phonon-magnetic excitation coupling and the main role in the Fe²⁺(1)–Fe²⁺(2) magnetic interaction occurs via superexchange through the oxygens. The magnetic excitations are not magnons in the usual sense, that is as quasiparticles having a long wavelength in an ordered system. The degree of observed broadening of the SiO₄-stretching modes is consonant with a Fe²⁺(1)–Fe²⁺(2) exchange energy of 4.7 cm^–1 presented by Schmidt et al. (1992). At temperatures above 300 K the line width of the mode at 840 cm^–1 decreases slightly, whereas those of low energy lattice modes increase. This suggests that a decrease in mode broadening due to weakened magnetic interactions compensates any thermally related broadening. Complete Fe²⁺ spin disorder may not be reached until at least 530 K. Results from this study show that estimates of third-law entropies for silicates using simple crystal-chemical considerations that do not account for magnetic properties cannot give accurate values for many transition-metal-containing phases.  相似文献   

Semi-empirical Gibbs free energy formulations for minerals and fluids for use in thermodynamic databases of petrological interest     

T. V.?GeryaEmail author  W. V.?Maresch  K. K.?Podlesskii  L. L.?Perchuk 《Physics and Chemistry of Minerals》2004,31(7):429-455

The P–T partition function in statistical thermodynamics can be used to derive semi-empirical formulations of the Gibbs free energy G for minerals and fluids. Parameterization of these equations includes simultaneous regression of experimental heat capacity and molar volume data, allowing fitting, appraisal and optimization of various data sources, as required in the construction of internally consistent petrological data bases. This approach can also be extended to minerals with -transitions and to fluids by considering the Gibbs free energy as a function of pressure P, temperature T and an ordering parameter X, so that accurate modelled representation and extrapolation of the thermodynamic properties of large numbers of petrologically significant minerals and coexisting fluids can be attained. The ordering parameter is chosen to denote the equilibrium mole fraction (thermodynamic probability) of ordered clusters (structural units) in a substance when G(T,P, X)=min. The procedure is tested on existing experimental data for the system MgO–SiO₂–H₂O. The proposed Gibbs free energy formulation permits thermodynamic properties of minerals, fluids and phase equilibria to be described and extrapolated over a wide range of pressure (0–800 kbar) and temperature (20–3000 K), thus allowing effective use in thermodynamic data bases of petrological interest.  相似文献