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Donghua Xie

Publications and source records attributed to Donghua Xie.

4 recordsLinked to original sources

Towards Machine Learning-based Model Predictive Control for HVAC Control in Multi-Context Buildings at Scale via Ensemble Learning

The building thermodynamics model, which predicts real-time indoor temperature changes under potential HVAC (Heating, Ventilation, and Air Conditioning) control operations, is crucial for optimizing HVAC control in buildings. While pioneering studies have attempted to develop such models for various building environments, these models often require extensive data collection periods and rely heavily on expert knowledge, making the modeling process inefficient and limiting the reusability of the models. This paper explores a model ensemble perspective that utilizes existing developed models as base models to serve a target building environment, thereby providing accurate predictions while reducing the associated efforts. Given that building data streams are non-stationary and the number of base models may increase, we propose a Hierarchical Reinforcement Learning (HRL) approach to dynamically select and weight the base models. Our approach employs a two-tiered decision-making process: the high-level focuses on model selection, while the low-level determines the weights of the selected models. We thoroughly evaluate the proposed approach through offline experiments and an on-site case study, and the experimental results demonstrate the effectiveness of our method.

cs.AI↗

Enabling Time-series Foundation Model for Building Energy Forecasting via Contrastive Curriculum Learning

Advances in time-series forecasting are driving a shift from conventional machine learning models to foundation models (FMs) that are trained with generalized knowledge. However, existing FMs still perform poorly in the energy fields, such as building energy forecasting (BEF). This paper studies the adaptation of FM to BEF tasks. We demonstrate the shortcomings of fine-tuning FM straightforwardly from both the perspectives of FM and the data. To overcome these limitations, we propose a new \textit{contrastive curriculum learning}-based training method. Our method optimizes the ordering of training data in the context of TSFM adaptation. Experiments show that our method can improve the zero/few-shot performance by 14.6\% compared to the existing FMs. Our code and new TSFM will be available at .

cs.LG↗

Griffiths phase and symmetry breaking in the hidden-order phase of URu2Si2

The heavy-fermion compound URu2Si2 exhibits a hidden-order phase below the temperature, ~ 17.5 K. In spite of intense research for past three decades, no consensus on the order parameter exists and the nature has posed a long-standing mystery. Here we report the discovery of a Griffiths phase within the hidden-order phase, characterized by residual short-range correlations on the collapse of long-range orders due to the dilution effects. In the Griffiths phase scenario, strong evidence are provided for those cluster-like spins, such as the unique power-law behavior of magnetic susceptibility and specific heat as well as the frequency dispersion of AC susceptibility. In this way, the existence of an order parameter is excluded, and the hidden order has a significant kinship with the long-range large-moment antiferromagnetism which is accessible by tuning the hydrostatic pressure or the chemical pressure (i.e., isoelectronic Fe doping). Moreover, an unidirectional anisotropy of resistivity measurements in rotating magnetic fields is observed in the hidden-order phase. The anisotropic magnetoresistance and the associated broken symmetries directly reflect the freezing behavior of at least part of magnetic clusters. Thus, the demonstrations of the Griffiths phase as an alternative proposal for the hidden-order phase of URu2Si2 are very promising, challenging the understanding of exotic electronic states in correlated matter and quantum materials.

cond-mat.str-el↗

Three-dimensional bulk electronic structure of the Kondo lattice CeIn3 revealed by photoemission

We show the three-dimensional electronic structure of the Kondo lattice CeIn3 using soft x-ray angle resolved photoemission spectroscopy in the paramagnetic state. For the first time, we have directly observed the three-dimensional topology of the Fermi surface of CeIn3 by photoemission. The Fermi surface has a complicated hole pocket centred at the Γ-Z line and an elliptical electron pocket centred at the R point of the Brillouin zone. Polarization and photon-energy dependent photoemission results both indicate the nearly localized nature of the 4f electrons in CeIn3, consistent with the theoretical prediction by means of the combination of density functional theory and single-site dynamical meanfield theory. Those results illustrate that the f electrons of CeIn3, which is the parent material of CeMIn5 compounds, are closer to the localized description than the layered CeMIn5 compounds.

cond-mat.str-el↗