Bridging the Gap Between Training and Inference for Spatio-Temporal Forecasting

Spatio-temporal sequence forecasting is one of the fundamental tasks in spatio-temporal data mining. It facilitates many real world applications such as precipitation nowcasting, citywide crowd flow prediction and air pollution forecasting. Recently, a few Seq2Seq based approaches have been proposed, but one of the drawbacks of Seq2Seq models is that, small errors can accumulate quickly along the generated sequence at the inference stage due to the different distributions of training and inference phase. That is because Seq2Seq models minimise single step errors only during training, however the entire sequence has to be generated during the inference phase which generates a discrepancy between training and inference. In this work, we propose a novel curriculum learning based strategy named Temporal Progressive Growing Sampling to effectively bridge the gap between training and inference for spatio-temporal sequence forecasting, by transforming the training process from a fully-supervised manner which utilises all available previous ground-truth values to a less-supervised manner which replaces some of the ground-truth context with generated predictions. To do that we sample the target sequence from midway outputs from intermediate models trained with bigger timescales through a carefully designed decaying strategy. Experimental results demonstrate that our proposed method better models long term dependencies and outperforms baseline approaches on two competitive datasets.Comment: ECAI 2020 Accepted, preprin

Synthetic considerations in the self-assembly of coordination polymers of pyridine-functionalised hybrid Mn-Anderson polyoxometalates

The incorporation of polyoxometalates (POMs) as structural units into ordered porous constructs such as metal-organic frameworks (MOFs) is desirable for a range of applications where intrinsic properties inherited from both the MOF and POM are utilised, including catalysis and magnetic data storage. The controlled self-assembly of targeted MOF topologies containing POM units is hampered by the wide range of oxo and hydroxo units on the peripheries of POMs that can act as coordinating groups towards linking metal cations leading to a diverse range of structures, but incorporation of organic donor units into hybrid POMs offers an alternative methodology to programmably synthesise POM/MOF conjugates. Herein, we report six coordination polymers obtained serendipitously wherein Zn2+ and Cu2+ link pyridine-appended Mn-Anderson clusters into two- and three-dimensional network solids with complex connectivities and topologies. Careful inspection of their solid-state structures has allowed us to identify common structure-directing features across these coordination polymers, including a square motif where two Zn2+ cations bridge two POMs. By correlating certain structural motifs with synthetic conditions we have formulated a series of design considerations for the self-assembly of coordination polymers of hybrid POMs, encompassing the selection of reaction conditions, co-ligands and linking metal cations. We anticipate that these synthetic guidelines will inform the future assembly of hybrid POMs into functional MOF materials

Modelling the Developing Mind: From Structure to Change

This paper presents a theory of cognitive change. The theory assumes that the fundamental causes of cognitive change reside in the architecture of mind. Thus, the architecture of mind as specified by the theory is described first. It is assumed that the mind is a three-level universe involving (1) a processing system that constrains processing potentials, (2) a set of specialized capacity systems that guide understanding of different reality and knowledge domains, and (3) a hypecognitive system that monitors and controls the functioning of all other systems. The paper then specifies the types of change that may occur in cognitive development (changes within the levels of mind, changes in the relations between structures across levels, changes in the efficiency of a structure) and a series of general (e.g., metarepresentation) and more specific mechanisms (e.g., bridging, interweaving, and fusion) that bring the changes about. It is argued that different types of change require different mechanisms. Finally, a general model of the nature of cognitive development is offered. The relations between the theory proposed in the paper and other theories and research in cognitive development and cognitive neuroscience is discussed throughout the paper