DFedADMM: Dual Constraints Controlled Model Inconsistency for Decentralized Federated Learning

To address the communication burden issues associated with federated learning (FL), decentralized federated learning (DFL) discards the central server and establishes a decentralized communication network, where each client communicates only with neighboring clients. However, existing DFL methods still suffer from two major challenges: local inconsistency and local heterogeneous overfitting, which have not been fundamentally addressed by existing DFL methods. To tackle these issues, we propose novel DFL algorithms, DFedADMM and its enhanced version DFedADMM-SAM, to enhance the performance of DFL. The DFedADMM algorithm employs primal-dual optimization (ADMM) by utilizing dual variables to control the model inconsistency raised from the decentralized heterogeneous data distributions. The DFedADMM-SAM algorithm further improves on DFedADMM by employing a Sharpness-Aware Minimization (SAM) optimizer, which uses gradient perturbations to generate locally flat models and searches for models with uniformly low loss values to mitigate local heterogeneous overfitting. Theoretically, we derive convergence rates of $\small \mathcal{O}\Big(\frac{1}{\sqrt{KT}}+\frac{1}{KT(1-\psi)^2}\Big)$ and $\small \mathcal{O}\Big(\frac{1}{\sqrt{KT}}+\frac{1}{KT(1-\psi)^2}+ \frac{1}{T^{3/2}K^{1/2}}\Big)$ in the non-convex setting for DFedADMM and DFedADMM-SAM, respectively, where $1 - \psi$ represents the spectral gap of the gossip matrix. Empirically, extensive experiments on MNIST, CIFAR10 and CIFAR100 datesets demonstrate that our algorithms exhibit superior performance in terms of both generalization and convergence speed compared to existing state-of-the-art (SOTA) optimizers in DFL.Comment: 24 page

Demand Management of Station-Based Car Sharing System Based on Deep Learning Forecasting

Metropolitan development has motivated car sharing into an attractive type of car leasing with the help of information technologies. In this paper, we propose a new approach based on deep learning techniques to assess the operation of a station-based car sharing system. First, we analyse the pick-up and drop-off operations of the station-based car sharing system, capturing the operational features of car sharing service and the behaviours of vehicle use from a temporal perspective. Then, we introduced an analytical system to detect the system operation concerning the spontaneous deviations derived from user demands from service provisions. We employed Long Short-Term Memory (LSTM) structure to forecast short-term future vehicle uses. An experimental case based on real-world data is reported to demonstrate the effectiveness of this approach. The results prove that the proposed structure generates high-quality predictions and the operation status derived from user demands

A New Quinoxalinyl-Substituted Nitronyl Nitroxide Radical and its Five-Spin Cu-II and Four-Spin Mn-II Complexes: Syntheses, Crystal Structures, and Magnetic Properties

National Natural Science Foundation of China [21101096, 90922032, 21071085, 20971072]; NSF of Tianjin [09JCYBJC05500]; Research Fund for the Doctoral Program of Higher Education [20100031120013]; Fundamental Research Funds for the Central UniversitiesA new radical of QNXL-2NIT (1) (QNXL-2NIT = 2-(2-quinoxalinyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) and its complexes [Cu(hfac)(2)](3)(QNXL-2NIT)(2)center dot 2CHCl(3) (2) and [Mn(hfac)(2)](2)(QNXL-2NIT)(2) (3) (hfac = 1,1,1,5,5,5-hexfluoroacetylacetone) were first reasonably designed and synthesised in this paper. The X-ray structure determination revealed that by introducing the quinoxalinyl ring group to the nitronyl nitroxide radical, QNXL-2NIT affords more coordination sites for metal ions. We successfully obtained its copper complex with linear tri-nuclear five-spin structure. However, when we substituted Mn-II as the central metal, complex 3 exhibits a rectangle-like four-spin framework containing two Mn-II ions and two radicals in one molecule. The magnetic study of the two complexes shows that there are strong antiferromagnetic interactions between the radical and the terminal Cu-II ions with g = 2.25, J = -291.67 cm(-1) and zJ(1) = -0.25 cm(-1) and the dominating interactions between the Mn-II ion and the radical in complex 3 are also antiferromagnetic with the parameters of g 1.99, J(1) = -77.00 cm(-1) and J(2) = 0.34 cm(-1)

Cross-linked polyphosphazene nanospheres boosting long-lived organic room-temperature phosphorescence

Long-lived organic room-temperature phosphorescence (RTP) has sparked intense explorations, owing to the outstanding optical performance and exceptional applications. Because triplet excitons in organic RTP experience multifarious relaxation processes resulting from their high sensitivity, spin multiplicity, inevitable nonradiative decay, and external quenchers, boosting RTP performance by the modulated triplet-exciton behavior is challenging. Herein, we report that cross-linked polyphosphazene nanospheres can effectively promote long-lived organic RTP. Through molecular engineering, multiple carbonyl groups (C═O), heteroatoms (N and P), and heavy atoms (Cl) are introduced into the polyphosphazene nanospheres, largely strengthening the spin-orbit coupling constant by recalibrating the electronic configurations between singlet (Sn) and triplet (Tn) excitons. In order to further suppress nonradiative decay and avoid quenching under ambient conditions, polyphosphazene nanospheres are encapsulated with poly(vinyl alcohol) matrix, thus synchronously prompting phosphorescence lifetime (173 ms longer), phosphorescence efficiency (∼12-fold higher), afterglow duration time (more than 20 s), and afterglow absolute luminance (∼19-fold higher) as compared with the 2,3,6,7,10,11-hexahydroxytriphenylene precursor. By measuring the emission intensity of the phosphorescence, an effective probe based on the nanospheres is developed for visible, quantitative, and expeditious detection of volatile organic compounds. More significantly, the obtained films show high selectivity and robustness for anisole detection (7.1 × 10-4 mol L-1). This work not only demonstrates a way toward boosting the efficiency of RTP materials but also provides a new avenue to apply RTP materials in feasible detection applications.Ministry of Education (MOE)This work was financially supported by the National Natural Science Foundation of China (21875025), the Innovation Research Group at Institutions of Higher Education in Chongqing (CXQT19027), the Chongqing Talent Program, the Science and Technology Project of Banan District, the Innovation Support Plan for the Returned Overseas of Chongqing (cx2020052), and the Open Fund of Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates (2021-kllma-03). The research was also supported by the Singapore Ministry of Education Academic Research Funds (RG3/21 and MOET2EP10120-0003)

A New Nitronyl Nitroxide Radical as Building Blocks for a Rare <i>S</i> = 13/2 High Spin Ground State 2p-3d Complex and a 2p-3d-4f Chain

A new nitronyl nitroxide radical L (L = 2-(4-(5-methyl-carbonyl-3-pyriyl)­benzoxo)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) containing N–O groups and the pyridyl nitrogen group was designed and synthesized as a multidentate ligand to obtain compounds with interesting structures and magnetic properties from 3d or 3d-4f precursors. The reaction of Cu­(hfac)₂ and/or Gd­(hfac)₃·2H₂O (hfac = hexafluoroacetylacetonate) with L resulted in a rare <i>S</i> = 13/2 high spin ground state Cu^II complex [(Cu­(hfac)₂)₇(L)₆] (<b>1</b>) and a Cu^II–Gd^III chain complex [Gd­(hfac)₃­Cu­(hfac)₂(L)₂]<i>_n</i>­·0.5CH₂Cl₂ (<b>2</b>). Single crystal X-ray diffraction studies indicate that the N–O groups of the L radicals are all axially bound to Cu^II ions in complex <b>1</b>, which result in the ferromagnetic exchange between Cu^II and radicals and an <i>S</i> = 13/2 high spin ground state. While adding Gd­(hfac)₃ units to the system of Cu­(hfac)₂ and L radical, a one dimension chain structure is obtained, and there are ferromagnetic Gd^III-radical interactions and antiferromagnetic radical–radical coupling in the chain