The Evolution Characteristics of Different Deformation Modes of Shear Slip Surface Based on Acoustic Emission Measurements

To investigate the acoustic emission (AE) precursor detection of landslide failures, a model test aiming at reproducing the typical shear surface deformation of different landslide modes was designed. The evolution characteristics of the AE signals were analyzed in terms of AE count, cumulative AE count, AE correlation diagrams, and corresponding time-frequency properties. The test results show that for the progressive deformation mode, the AE count experiences a low-level period, an active period and a rapid increase period, and the distribution of correlation diagram hits concentrates in a relatively small scale and then gradually scatters. There is low frequency signals firstly and then high frequency signals, and the energy proportion of the high-frequency signals shows an increasing tendency. For the sudden deformation mode, the magnitude of AE count increases sharply, leading to the cumulative AE count curve rises steeply, and correlation diagram hits distribution turns into relatively scattering rapidly. Furthermore, the high frequency signals and high energy proportion appear much earlier than that of the progressive deformation mode. For steady deformation mode, however, the acoustic emission activity is quite active in the initial stage, the cumulative AE count curve rises sharply and then maintains relatively flat trend, and correlation diagram hits distribution scatters firstly, then the signal hits distribution begins to concentrate in a relatively small scale. There are intensive high-frequency hits and high energy proportion earlier, and later they tend to decay in response to smaller magnitudes of movement. Comprehensive use of multiple features can help identify landslide deformation patterns more accurately under complex natural conditions, which may provide a promising reference for the field warning monitoring of the diverse landslide failures.

Revisiting the von Neumann–Wigner noncrossing rule and validity of a dynamic correlation diagram method

The noncrossing rule for potential energy surfaces can be applied only, as originally postulated by von Neumann and Wigner, to slowly occurring changes; it has, however, over many years, been widely used to rationalize fast chemical reactions. Taking the conversion of Dewar benzene to benzene as an example, we demonstrate a reaction that has a timescale for which crossings are allowed. Since it is now established that elementary chemical reactions proceed over ca. 10–100[Formula: see text]fs, as revealed experimentally by Zewail, the noncrossing rule cannot any longer be said to be valid for most chemical reactions. We further demonstrate that the mechanism of the chemiluminescent conversion of Dewar benzene to benzene is explained by an electronic state diagram derived using a dynamic correlation diagram method which allows crossings, whereas the reaction is not explained by a conventional approach, applying the noncrossing rule using a static correlation diagram method.

Hydrological regionalisation based on available hydrological information for runoff prediction at catchment scale

Regionalisation provides a way of transferring hydrological information from gauged to ungauged catchments. The past few decades has seen several kinds of regionalisation approaches for catchment classification and runoff predictions. The underlying assumption is that catchments having similar catchment properties are hydrological similar. This requires the appropriate selection of catchment properties, particularly the inclusion of observed hydrological information, to explain the similarity of hydrological behaviour. We selected observable catchments properties and flow duration curves to reflect the hydrological behaviour, and to regionalize rainfall-runoff response for runoff prediction. As a case study, we investigated 15 catchments located in the Yangtze and Yellow River under multiple hydro-climatic conditions. A clustering scheme was developed to separate the catchments into 4 homogeneous regions by employing catchment properties including hydro-climatic attributes, topographic attributes and land cover etc. We utilized daily flow duration curves as the indicator of hydrological response and interpreted hydrological similarity by root mean square errors. The combined analysis of similarity in catchment properties and hydrological response suggested that catchments in the same homogenous region were hydrological similar. A further validation was conducted by establishing a rainfall-runoff coaxial correlation diagram for each catchment. A common coaxial correlation diagram was generated for each homogenous region. The performances of most coaxial correlation diagrams met the national standard. The coaxial correlation diagram can be transferred within the homogeneous region for runoff prediction in ungauged catchments at an hourly time scale.

Characterizing Seismic Resiliency Using an Energy Dissipation-Recentering Correlation Diagram

For a structural system, the potential to dissipate energy and recenter during an earthquake are two important characteristics that support seismic resiliency. This paper proposes two dimensionless parameters, namely, an energy dissipation ratio ( R ED) and a recentering ratio ( R RC), to quantify the potential of an inelastic mechanism to dissipate hysteretic energy and recover from inelastic deformations, respectively. For most mechanisms used in seismic design, these two parameters are not independent, but rather, they are inherently related. In this work, an R ED- R RC correlation diagram is established by placing each parameter within a two-dimensional plot. Importantly, four different zones with varying seismic response attributes are identified. Numerical studies considering various idealized inelastic systems coupled with experimental data are then utilized to demonstrate the utility of the R ED- R RC correlation diagram as a simple design tool for estimating the seismic resiliency of a system.