Efficient power conversion interface circuits for energy harvesting applications

Harvesting energy from the environment for powering micro-power devices have been increasing in popularity. These types of devices can be used in embedded applications or in sensor networks where battery replacement is impractical. In this dissertation, different methods of energy harvesting from the environment are explored as alternative sources of energy for devices. Some of the most popular energy extraction used in electronic devices today are radio frequency (RF) and thermal/vibrational energy extraction. This dissertation presents novel power techniques that enable some of the most efficient power conversion circuits published to date. New power conversion circuits to interface to a piezoelectric micro-power generator that produces electrical energy from temperature differences have been fabricated and tested. Circuit designs and measurement results are presented for a half-wave synchronous rectifier with voltage doubler, a full-wave synchronous rectifier and a passive full-wave rectifier circuit. The active rectifier based on synchronous rectification, fabricated in a 0.25-μm CMOS process, is 86% efficient with 22-μW peak output power when connected to the piezoelectric micro-power generator. This gives the highest efficiency to date for active rectification circuits at the micro-power level. The passive rectifier circuit is 66% efficient with 16-μW peak output power and requires no quiescent current to operate. RF-powered devices are typically inductively coupled and extract their energy from the near field while operating within a few inches of the radiating source. Longer operating distances, exceeding 10 meters, are desired for a broader set of applications including distributed sensor networks. This dissertation describes an efficient method for far field power extraction from RF energy to enable long distance passively powered sensor networks. Passive rectifier circuits are designed in the TSMC 0.25μm mixed-signal CMOS process and antennas for the system are printed on a 4-layer FR4 board. A high-Q resonator is used with a matching network to passively amplify the input voltage to the rectifier. At the circuit level, floating gate transistors are used as rectifying diodes to reduce the diode threshold loss in voltage rectification and therefore increase the rectifier efficiency. A 36-stage rectifier fabricated in a 0.25-μm CMOS process attains an efficiency of over 60% in the far field with a received power sensitivity of 5.5μW(-22.6 dBm), corresponding to an operating distance of 44 meters. The effective threshold voltage of the floating-gate diode is reduced to 36 mV. This is the highest performance for far-field RF energy conversion reported to date. In ultra-low energy system, such as sensor networks, it is essential that power management circuitry are designed to dissipate very low quiescent power. RF energy and power management circuits are designed in a 0.18μm CMOS process. Voltage regulators are designed to operate at high input voltage and low power in a standard CMOS process. The voltage regulators can withstand input voltages up to 12 volts and dissipates from 90 nW to 1.4 μW of power. A floating-gate programming circuit is designed with a self-wakeup timer that turns itself on about once a month. The floating-gate programming circuits dissipates about 30 nW in sleep mode and 8 μW in active mode

DCU and HCMUS at NTCIR-16 Lifelog-4

In this paper, we present our DCU and HCMUS team’s participation in the NTCIR16 Lifelog-4 task by using two different retrieval systems, namely LifeSeeker and Myscéal that were originally introduced in the Lifelog Search Challenge (LSC) and adapted for addressing the Lifelog Semantic Access Task (LSAT). To tackle the task in an automatic manner, both LifeSeeker and Myscéal employed pre-processing techniques as part of the retrieval process, while LifeSeeker further utilised a post-processing step to refine the retrieval results. Regarding the interactive manner, we evaluated the Myscéal system by conducting a user study on both expert and novice users in both ad-hoc and known-item-search settings

Nutrient budgets in the Saigon-Dongnai River basin: Past to future inputs from the developing Ho Chi Minh megacity (Vietnam)

International audienceHo Chi Minh City (HCMC, Vietnam) is one of the fastest growing megacities in the world. In this paper, we attempt to analyse the dynamics of nutrients, suspended sediments , and water discharges in its aquatic systems today and in the future. The work is based on nine sampling sites along the Saigon River and one on the Dongnai River to identify the reference water status upstream from the urban area and the increase in fluxes that occur within the city and its surroundings. For the first time, the calculated fluxes allow drawing up sediment and nutrient budgets at the basin scale and the quantification of total nutrient loading to the estuarine and coastal zones (2012-2016 period). Based on both national Vietnamese and supplementary monitoring programs, we estimated the water, total suspended sediment, and nutrients (Total N, Total P, and dissolved silica: DSi) fluxes at 137 m 3 year −1 , tonSS year −1 , 5,323 tonN year −1 , 450 tonP year −1 , and m 3 year −1 for the Saigon River and 1,693 year −1 , 3,292 2,734 1,175 × 10 3 tonSi × 10 3 tonSS year −1 , 31,030 tonN year −1 , 1,653 tonP year −1 , and 31,138 tonSi year −1 for the Dongnai River, respectively. Nutrient fluxes provide an indicator of coastal eutrophication potential (indicator of coastal eutrophication potential), using nutrient stoichiometry ratios. Despite an excess of nitrogen and phosphorus over silica, estuarine waters downstream of the megacity are not heavily impacted by HCMC. Finally, we analysed scenarios of future trends (2025-2050) for the nutrient inputs on the basis of expected population growth in H C M C and improvement of wastewater treatment capacity. We observed that without the construction of a large number of additional wastewater treatment plants, the eutrophication problem is likely to worsen. The results are discussed in the context of the wastewater management policy

SHREC\u2719 Track: Extended 2D Scene Image-Based 3D Scene Retrieval

In the months following our SHREC 2018-2D Scene Image-Based 3D Scene Retrieval (Scene IBR2018) track, we have extended the number of the scene categories fro the initial 10 classes in the Scene IBR2018 benchmark to 30 classes, resulting in a new benchmark Scene IBR2019 which has 30,000 scene images and 3,000 3D scene models. For that reason, we seek to further evaluate the performance of existing and 2D scene image-based 3D scene retrieval algorithms using this extended and more comprehensive new benchmark. Three groups from the Netherlands, the United States and Vietnam participated and collectively submitted eight runs. This report documents the evaluation of each method based on seven performances metrics, offers an in-depth discussion as well as analysis on the methods employed and discusses future directions that have the potential to address this task. Again, deep learning techniques have demonstrated notable performance in terms of both accuracy and scalability when applied to this exigent retrieval task. To further enrich the current state of 3D scene understanding and retrieval, our evaluation toolkit, all participating methods\u27 results and the comprehensive 2D/3D benchmark have all been make publicly available