Accelerating federated learning via momentum gradient descent

Federated learning (FL) provides a communication-efficient approach to solve machine learning problems concerning distributed data, without sending raw data to a central server. However, existing works on FL only utilize first-order gradient descent (GD) and do not consider the preceding iterations to gradient update which can potentially accelerate convergence. In this article, we consider momentum term which relates to the last iteration. The proposed momentum federated learning (MFL) uses momentum gradient descent (MGD) in the local update step of FL system. We establish global convergence properties of MFL and derive an upper bound on MFL convergence rate. Comparing the upper bounds on MFL and FL convergence rates, we provide conditions in which MFL accelerates the convergence. For different machine learning models, the convergence performance of MFL is evaluated based on experiments with MNIST and CIFAR-10 datasets. Simulation results confirm that MFL is globally convergent and further reveal significant convergence improvement over FL

Rotationally Reconfigurable Single-Element Prism for Enhancing Scanning Flexibility of Risley Prism Antenna System

In this letter, we propose a rotationally reconfigurable single-element prism that is compatible with the typical Risley prism antenna system. It consists of a pair of rotating decentered phase plates operating at 30 GHz. The equivalent prism angle can be continuously changed between 0° and 14° by simply rotating these two phase plates. An all-dielectric low-cost prototype has been designed, fabricated, and measured, which demonstrates the peak realized gain of 21 dBi can be achieved with a gain variation less than 0.9 dB within the reconfigurable angle range of 0°–14°. Besides, the combination of phase distribution of two rotating phase plates can be used as a new mechanism avoiding using first-order paraxial approximation to realize two-dimensional beam scanning

Infinitely many solutions for the Schrödinger equations in RN with critical growth

AbstractWe consider the following nonlinear problem in RN(0.1){−Δu+V(|y|)u=uN+2N−2,u>0, in RN;u∈H1(RN), where V(r) is a bounded non-negative function, N⩾5. We show that if r2V(r) has a local maximum point, or local minimum point r0>0 with V(r0)>0, then (0.1) has infinitely many non-radial solutions, whose energy can be made arbitrarily large. As an application, we show that the solution set of the following problem−Δu=λu+uN+2N−2,u>0 on SN has unbounded energy, as long as λ<−N(N−2)4, N⩾5

A Multi-timescale and Chance-Constrained Energy Dispatching Strategy of Integrated Heat-Power Community with Shared Hybrid Energy Storage

The community in the future may develop into an integrated heat-power system, which includes a high proportion of renewable energy, power generator units, heat generator units, and shared hybrid energy storage. In the integrated heat-power system with coupling heat-power generators and demands, the key challenges lie in the interaction between heat and power, the inherent uncertainty of renewable energy and consumers' demands, and the multi-timescale scheduling of heat and power. In this paper, we propose a game theoretic model of the integrated heat-power system. For the welfare-maximizing community operator, its energy dispatch strategy is under chance constraints, where the day-ahead scheduling determines the scheduled energy dispatching strategies, and the real-time dispatch considers the adjustment of generators. For utility-maximizing consumers, their demands are sensitive to the preference parameters. Taking into account the uncertainty in both renewable energy and consumer demand, we prove the existence and uniqueness of the Stackelberg game equilibrium and develop a fixed point algorithm to find the market equilibrium between the community operator and community consumers. Numerical simulations on integrated heat-power system validate the effectiveness of the proposed multi-timescale integrated heat and power model

Abruptly Autofocusing Beams Based on Phase Modulated Zone Plate

2022 Asia-Pacific Microwave Conference (APMC), 29 November 2022 - 02 December 2022, Yokohama, JapanIn this paper, we introduce a phase modulated zone plate to generate the circular symmetric Airy beam (CSAB) with abruptly autofocusing characteristic at 30GHz. This phase modulated zone plate is a phase combination form of a radial phase plate and a lens, which would make the conventional generation system of CSAB more compact. Based on full wave simulation, the unique abruptly autofocusing is explored in the field of millimeter wave. Even if the metal plate is placed in front of the phase modulated zone plate, the focusing can still be well obtained, which provides a potential advantage in millimeter-wave sensing