Lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario: a spatial cross-correlation modelling approach

The application of spatial cross-correlation modelling was tested on continuous time series of electrical conductivity to estimate lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario. Overall, the model appeared more robust for the winter salting season than for the summer growing season. The winter results showed shorter travel times with higher velocity longitudinally (upstream to downstream) in an urban stream reach with more impervious surfaces than in a rural reach with more permeable surfaces. The lateral exchange rates (stream-hyporheic zone) were observed to be affected by both local and catchment-scale land use and soil profiles. Cross-correlation results and time series data also indicated that road-salt applications in the urban catchment may be leading to underground storage of chloride, contributing to the streams in summer and producing year-round peaks of chloride in the urban stream reach.

Lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario: a spatial cross-correlation modelling approach

The application of spatial cross-correlation modelling was tested on continuous time series of electrical conductivity to estimate lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario. Overall, the model appeared more robust for the winter salting season than for the summer growing season. The winter results showed shorter travel times with higher velocity longitudinally (upstream to downstream) in an urban stream reach with more impervious surfaces than in a rural reach with more permeable surfaces. The lateral exchange rates (stream-hyporheic zone) were observed to be affected by both local and catchment-scale land use and soil profiles. Cross-correlation results and time series data also indicated that road-salt applications in the urban catchment may be leading to underground storage of chloride, contributing to the streams in summer and producing year-round peaks of chloride in the urban stream reach.

A Sequential Convolution Network for Population Flow Prediction with Explicitly Correlation Modelling

Population flow prediction is one of the most fundamental components in many applications from urban management to transportation schedule. It is challenging due to the complicated spatial-temporal correlation.While many studies have been done in recent years, they fail to simultaneously and effectively model the spatial correlation and temporal variations among population flows. In this paper, we propose Convolution based Sequential and Cross Network (CSCNet) to solve them. On the one hand, we design a CNN based sequential structure with progressively merging the flow features from different time in different CNN layers to model the spatial-temporal information simultaneously. On the other hand, we make use of the transition flow as the proxy to efficiently and explicitly capture the dynamic correlation between different types of population flows. Extensive experiments on 4 datasets demonstrate that CSCNet outperforms the state-of-the-art baselines by reducing the prediction error around 7.7%∼10.4%.

Li-ion half-cells studied operando during cycling by small-angle neutron scattering

Small-angle neutron scattering (SANS) was recently applied to the in situ and operando study of the charge/discharge process in Li-ion battery full-cells based on a pouch cell design. Here, this work is continued in a half-cell with a graphite electrode cycled versus a metallic lithium counter electrode, in a study conducted on the SANS-1 instrument of the neutron source FRM II at the Heinz Maier-Leibnitz Zentrum in Garching, Germany. It is confirmed that the SANS integrated intensity signal varies as a function of graphite lithiation, and this variation can be explained by changes in the squared difference in scattering length density between graphite and the electrolyte. The scattering contrast change upon graphite lithiation/delithiation calculated from a multi-phase neutron scattering model is in good agreement with the experimentally measured values. Due to the finite coherence length, the observed SANS contrast, which mostly stems from scattering between the (lithiated) graphite and the electrolyte phase, contains local information on the mesoscopic scale, which allows the development of lithiated phases in the graphite to be followed. The shape of the SANS signal curve can be explained by a core–shell model with step-wise (de)lithiation from the surface. Here, for the first time, X-ray diffraction, SANS and theory are combined to give a full picture of graphite lithiation in a half-cell. The goal of this contribution is to confirm the correlation between the integrated SANS data obtained during operando measurements of an Li-ion half-cell and the electrochemical processes of lithiation/delithiation in micro-scaled graphite particles. For a deeper understanding of this correlation, modelling and experimental data for SANS and results from X-ray diffraction were taken into account.