4,481 research outputs found
Deep Room Recognition Using Inaudible Echos
Full text linkRecent years have seen the increasing need of location awareness by mobile
applications. This paper presents a room-level indoor localization approach
based on the measured room's echos in response to a two-millisecond single-tone
inaudible chirp emitted by a smartphone's loudspeaker. Different from other
acoustics-based room recognition systems that record full-spectrum audio for up
to ten seconds, our approach records audio in a narrow inaudible band for 0.1
seconds only to preserve the user's privacy. However, the short-time and
narrowband audio signal carries limited information about the room's
characteristics, presenting challenges to accurate room recognition. This paper
applies deep learning to effectively capture the subtle fingerprints in the
rooms' acoustic responses. Our extensive experiments show that a two-layer
convolutional neural network fed with the spectrogram of the inaudible echos
achieve the best performance, compared with alternative designs using other raw
data formats and deep models. Based on this result, we design a RoomRecognize
cloud service and its mobile client library that enable the mobile application
developers to readily implement the room recognition functionality without
resorting to any existing infrastructures and add-on hardware.
Extensive evaluation shows that RoomRecognize achieves 99.7%, 97.7%, 99%, and
89% accuracy in differentiating 22 and 50 residential/office rooms, 19 spots in
a quiet museum, and 15 spots in a crowded museum, respectively. Compared with
the state-of-the-art approaches based on support vector machine, RoomRecognize
significantly improves the Pareto frontier of recognition accuracy versus
robustness against interfering sounds (e.g., ambient music).Comment: 29 page
A cost-effective alkaline polysulfide-air redox flow battery enabled by a dual-membrane cell architecture
Get PDFWith the rapid development of renewable energy harvesting technologies, there is a significant demand for long-duration energy storage technologies that can be deployed at grid scale. In this regard, polysulfide-air redox flow batteries demonstrated great potential. However, the crossover of polysulfide is one significant challenge. Here, we report a stable and cost-effective alkaline-based hybrid polysulfide-air redox flow battery where a dual-membrane-structured flow cell design mitigates the sulfur crossover issue. Moreover, combining manganese/carbon catalysed air electrodes with sulfidised Ni foam polysulfide electrodes, the redox flow battery achieves a maximum power density of 5.8 mW cm−2 at 50% state of charge and 55 °C. An average round-trip energy efficiency of 40% is also achieved over 80 cycles at 1 mA cm−2. Based on the performance reported, techno-economic analyses suggested that energy and power costs of about 2.5 US/kW, respectively, has be achieved for this type of alkaline polysulfide-air redox flow battery, with significant scope for further reduction
Interfacial Engineering of Polymer Membranes with Intrinsic Microporosity for Dendrite‐Free Zinc Metal Batteries
Get PDFMetallic zinc has emerged as a promising anode material for high-energy battery systems due to its high theoretical capacity (820 mAh g−1), low redox potential for two-electron reactions, cost-effectiveness and inherent safety. However, current zinc metal batteries face challenges in low coulombic efficiency and limited longevity due to uncontrollable dendrite growth, the corrosive hydrogen evolution reaction (HER) and decomposition of the aqueous ZnSO4 electrolyte. Here, we report an interfacial-engineering approach to mitigate dendrite growth and reduce corrosive reactions through the design of ultrathin selective membranes coated on the zinc anodes. The submicron-thick membranes derived from polymers of intrinsic microporosity (PIMs), featuring pores with tunable interconnectivity, facilitate regulated transport of Zn2+-ions, thereby promoting a uniform plating/stripping process. Benefiting from the protection by PIM membranes, zinc symmetric cells deliver a stable cycling performance over 1500 h at 1 mA/cm2 with a capacity of 0.5 mAh while full cells with NaMnO2 cathode operate stably at 1 A g−1 over 300 cycles without capacity decay. Our work represents a new strategy of preparing multi-functional membranes that can advance the development of safe and stable zinc metal batteries
Active Image-based Modeling with a Toy Drone
Full text linkImage-based modeling techniques can now generate photo-realistic 3D models
from images. But it is up to users to provide high quality images with good
coverage and view overlap, which makes the data capturing process tedious and
time consuming. We seek to automate data capturing for image-based modeling.
The core of our system is an iterative linear method to solve the multi-view
stereo (MVS) problem quickly and plan the Next-Best-View (NBV) effectively. Our
fast MVS algorithm enables online model reconstruction and quality assessment
to determine the NBVs on the fly. We test our system with a toy unmanned aerial
vehicle (UAV) in simulated, indoor and outdoor experiments. Results show that
our system improves the efficiency of data acquisition and ensures the
completeness of the final model.Comment: To be published on International Conference on Robotics and
Automation 2018, Brisbane, Australia. Project Page:
https://huangrui815.github.io/active-image-based-modeling/ The author's
personal page: http://www.sfu.ca/~rha55
Carbon‐coated current collectors in lithium‐ion batteries and supercapacitors: Materials, manufacture and applications
Get PDFThe current collector is a crucial component in lithium-ion batteries and supercapacitor setups, responsible for gathering electrons from electrode materials and directing them into the external circuit. However, as battery systems evolve and the demand for higher energy density increases, the limitations of traditional current collectors, such as high contact resistance and low corrosion resistance, have become increasingly evident. This review investigates the functions and challenges associated with current collectors in modern battery and supercapacitor systems, with a particular focus on using carbon coating methods to enhance their performance. Surface coating, known for its simplicity and wide applicability, emerges as a promising solution to address these challenges. The review provides a comprehensive overview of carbon-coated current collectors across various types of metal and nonmetal substrates in lithium-ion batteries and supercapacitors, including a comparative analysis of coating materials and techniques. It also discusses methods for manufacturing carbon-coated current collectors and their practical implications for the industry. Furthermore, the review explores prospects and opportunities, highlighting the development of next-generation high-performance coatings and emphasizing the importance of advanced current collectors in optimizing energy device performance
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