Non-local Attention Optimized Deep Image Compression

This paper proposes a novel Non-Local Attention Optimized Deep Image Compression (NLAIC) framework, which is built on top of the popular variational auto-encoder (VAE) structure. Our NLAIC framework embeds non-local operations in the encoders and decoders for both image and latent feature probability information (known as hyperprior) to capture both local and global correlations, and apply attention mechanism to generate masks that are used to weigh the features for the image and hyperprior, which implicitly adapt bit allocation for different features based on their importance. Furthermore, both hyperpriors and spatial-channel neighbors of the latent features are used to improve entropy coding. The proposed model outperforms the existing methods on Kodak dataset, including learned (e.g., Balle2019, Balle2018) and conventional (e.g., BPG, JPEG2000, JPEG) image compression methods, for both PSNR and MS-SSIM distortion metrics

Comprehensive control of proton exchange membrane fuel cell as backup power supply for UPS

To improve the performance of a proton exchange membrane fuel cell (PEMFC) stack, it is important to avoid the hydrogen and oxygen/air starvation of electrochemical reaction, prevent the dehydration and drying of the membrane, and track the output power. This paper conducts research in a comprehensive control strategy of the operation parameters of an uninterruptible power system (UPS) with backup PEMFC and battery power sources, such as the thermal management and control of operating temperature, pressures and mass flows of hydrogen and air for the PEMFC stack, switch of the power supply between PEMFC and battery for UPS, and the output power tracking of PEMFC. Based on the dynamic model of the anode and cathode flow system, the models of manifold and the performance curve, a detail model analysis is presented. A comprehensive control method is proposed and applied to the PEMFC system employed for the power source of UPS. The experimental results show that the comprehensive control method can effectively keep constant pressures of the inlet hydrogen and air, automatically switch the power supply between PEMFC and battery, reasonably improve the performance of the PEMFC through thermal management and control of operating temperature, and track the real-time changes of the output power and the distribution of the mass flows of hydrogen and oxygen/air

Development of a single-phase high frequency UPS with backup PEM fuel cell and battery

This paper presents a 300 W single-phase high frequency uninterrupted power supply (UPS) with backup proton exchange membrane fuel cell (PEMFC) and battery, DC/AC inverter, DC/DC converter, AC/DC rectifier, and AC/DC recharger. The principle and structure of the PEMFC/battery hybrid UPS system are introduced and discussed. Key practical techniques of the design are presented, including the design of the PEMFC generating system, the control technique of the AC/DC rectifier, AC/DC recharger, DC/AC inverter and DC/DC converter based on a microcomputer MC68HC11K4 and other integrated circuit chips. Experimental results show that during the switching process from battery to PEMFC, and vice versa, the UPS can provide an uninterrupted alternate voltage for the load, with low cost, low weight, small volume and size, great reliability and maintainability

Power converters and controllers for UPS applications with backup PEM fuel cell

This paper studies the practical cost-effective DC/DC converter, DC/AC inverter and AC/DC rectifier for an uninterruptible power supply (UPS) system with backup proton exchange membrane fuel cell (PEMFC). Furthermore, a comprehensive controller for the PEMFC is designed according to the change of the load, while the energy storage elements, such as battery and ultracapacitor, are chosen in order to compensate the slow dynamic response of PEMFC and to meet the sudden peak load energy demand. The designed power converters can supply high quality power with flexible conversion functions, leading to the establishment of reliable power management for UPS applications. Finally, a suitable control strategy and technique, capable of coping with the change of the load for PEMFC and realizing the energy managements of UPS hybrid system, is implemented. The performances of the proposed power converters and controllers are evaluated by experimental results, showing that the developed UPS system with backup PEMFC and battery power sources is suitable for industry applications. © 2008 IEEE

A PEMFC/battery hybrid ups system for backup and emergency power applications

This paper presents the development of a proton exchange membrane fuel cell (PEMFC) and battery hybrid uninterruptible power system (UPS) for backup and emergency power applications. A sixty-cell PEMFC stack is employed as the main power source at normal load and a 3-cell lead-acid battery is employed as the auxiliary power of the UPS at overload or during the PEMFC startup. The PEMFC consists of two valves for the hydrogen input and output respectively, a mass flow controller to adjust the hydrogen mass flow, and a pressure sensor to control the hydrogen pressure, and their control units for the management of the whole system. The design procedures of the UPS hybrid system are discussed. Experimental setups are presented and the experimental results verify the performances of the PEMFC/battery hybrid power source and the UPS system under the condition of computer load. The developed UPS system proves to be a cost-effective solution for backup and emergency power applications. © 2007 IEEE

Fault monitoring and control of PEM fuel cell as backup power for UPS applications

This paper presents the expert fault monitoring and intelligent comprehensive control of a proton exchange membrane (PEM) fuel cell (PEMFC) as backup power source for an uninterruptible power supply (UPS) system. The failure status can be shown on the screen of a micro-computer (or a PC) linked with the UPS through an RS-232 and on the control panel of the UPS through LED indicator lights. The proposed intelligent comprehensive monitors and controllers of PEMFC and UPS can supply high quality power with flexible conversion functions, leading to the establishment of reliable power management for UPS applications. Finally, a suitable strategy and technique of fault monitoring and control for a UPS hybrid system with backup PEMFC and battery is implemented. The performances of the monitors and controllers are evaluated by experimental results, showing that the developed UPS system with backup PEMFC and battery power sources is suitable for industry applications. © 2009 IEEE

Diffusion–reaction–induced stress in moving boundary cylindrical Li-ion battery electrodes

Lithium (Li) inserted into or extracted from the electrode in Li-ion battery causes stress which may cause fracture of the electrode. A moving boundary model in a cylindrical Li-ion battery electrode accounting for reversible electrochemical reaction is obtained. The volumetric change created by Li diffusion and formation of reversible reaction product would generate the diffusion–reaction-induced stress in the electrode. The constitutive relation among Li concentration, reaction product, and stress is derived, and the numerical solutions of the concentration, reaction product, and stress fields are obtained. The effects of phase transformation and reversible electrochemical reaction on Li diffusion and stress in a cylindrical Li-ion battery electrode are analyzed

Modeling and simulation of PMSM control system based on SVPWM

The paper introduces the basic principle of space vector pulse width modulation simply and expatiates a method for implementing space vector pulse width modulation in detail based on MATLAB/SIMULINK, designs modeling and simulation of AC servo system with PMSM (Permanent Magnet Synchronous Motor), the simulation results show that the model is effective, and the method provides a base for both software and hardware design of an actual PMSM