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| 2. |
- Xu, Jiawei, et al.
(author)
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Modeling Cycle-to-Cycle Variation in Memristors for In-Situ Unsupervised Trace-STDP Learning
- 2024
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In: IEEE Transactions on Circuits and Systems - II - Express Briefs. - : Institute of Electrical and Electronics Engineers (IEEE). - 1549-7747 .- 1558-3791. ; 71:2, s. 627-631
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Journal article (peer-reviewed)abstract
- Evaluating the computational accuracy of Spiking Neural Network (SNN) implemented as in-situ learning on large-scale memristor crossbars remains a challenge due to the lack of a versatile model for the variations in non-ideal memristors. This brief proposes a novel behavioral variation model along with a four-stage pipeline for physical memristors. The proposed variation model combines both absolute and relative variations. Therefore, it can better characterize different memristor cycle-to-cycle (C2C) variations in practice. The proposed variation model has been used to simulate the behavior of two physical memristors. Adopting the non-ideal memristor model, the trace-based spiking-timing dependent plasticity (STDP) unsupervised in-memristor learning system is simulated. Although the synaptic-level weight simulation shows a performance degradation of 7.99% and 4.07% increase in the relative root mean square error (RRMSE), the network-level simulation results show no accuracy loss on the MNIST benchmark. Furthermore, the impacts of absolute and relative C2C variations on network performance are simulated and analyzed through two sets of univariate experiments.
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| 3. |
- Xu, Jiawei, et al.
(author)
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Optoelectronic memristor model for optical synaptic circuit of spiking neural networks
- 2023
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In: 21st IEEE Interregional NEWCAS Conference, NEWCAS 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
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Conference paper (peer-reviewed)abstract
- Optoelectronic memristors are suitable candidates for hardware implementation of optical synapses in spiking neural networks (SNNs), thanks to their electrical and optical characteristics. To study the feasibility of memristor-based optical synapses in SNNs, a behavior model for optoelectronic memristors is proposed in this paper, including electrical programming modeling and photocurrent read modeling. Based on the model, the behavior of a molecular ferroelectric (MF)/semiconductor interfacial memristor is simulated. This paper also proposes an optical synaptic circuit for trace-based spike-timing-dependent plasticity (STDP) learning rule. The electrical characteristics of the memristor are explored and exploited to emulate the trace in the pairwise nearest-neighbor STDP, while the optical characteristics are utilized for non-destructive readout and weight calculation. Synaptic-level simulation results show a 99.96% correlation coefficient (CC) and a 1.91% relative root mean square error (RRMSE) in the weight approximate computation. Extending the simulation to the network level, the optoelectronic memristor-based unsupervised STDP learning system can achieve a 92.07± 0.64% accuracy on the MNIST benchmark.
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| 4. |
- Zhu, Zikai, et al.
(author)
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Using a VAE-SOM architecture for anomaly detection of flexible sensors in limb prosthesis
- 2023
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In: Journal of Industrial Information Integration. - : Elsevier BV. - 2452-414X .- 2467-964X. ; 35
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Journal article (peer-reviewed)abstract
- Flexible wearable sensor electronics, combined with advanced software functions, pave the way toward increasingly intelligent healthcare devices. One important application area is limb prosthesis, where printed flexible sensor solutions enable efficient monitoring and assessing of the actual intra-socket dynamic operation conditions in clinical and other more natural environments. However, the data collected by such sensors suffer from variations and errors, leading to difficulty in perceiving the actual operational conditions. This paper proposes a novel method for detecting anomalies in the data that are collected for measuring the intra-socket dynamic operation conditions by printed flexible wearable sensors. A discrete generative model based on Variational AutoEncoder (VAE) is used first to encode the collected multi-variant time-series data in terms of latent states. After that, a clustering method based on the Self-Organizing Map (SOM) is used to acquire discrete and interpretable representations of the VAE encoded latent states. An adaptive Markov chain is utilized to detect anomalies by quantifying state transitions and revealing temporal dependencies. The contributions of the proposed architecture conclude as follows: (1) Using the VAE-SOM hybrid model to regularize the continues data as discrete states, supporting interpreting the operational data to analytic models. (2) Employing adaptive Markov chains to generalize the transitions of these states, allowing to model the complex operational conditions. Compared with benchmark methods, our architecture is validated via two public datasets and achieves the best F1 scores. Moreover, we measure the run-time performance of this lightweight architecture. The results indicate that the proposed method performs low computational complexity, facilitating the applications on real-life productions.
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| 5. |
- Zou, Zhuo, et al.
(author)
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An efficient passive RFID system for ubiquitous identification and sensing using impulse UWB radio
- 2007
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In: Elektrotechnik und Informationstechnik. - : Springer Science and Business Media LLC. - 0932-383X. ; 124:11, s. 397-403
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Journal article (peer-reviewed)abstract
- The next generation RFID system for ubiquitous identification and sensing requires both energy and system efficiency. This paper describes an efficient passive RFID system using impulse ultra-wideband radio (IR-UWB), at a 10 m operation range. Unlike conventional passive RFID systems which rely on backscatter and narrowband radio, IR-UWB is introduced as the uplink (communication from a tag to a reader). By utilizing a specialized communication protocol and a novel ALOHA-based anti-collision algorithm, such semi-UWB systems enable a high network throughput (2000 tag/sec) under the low power and low cost constraint. A low power tag design for proof of concept is finally presented.
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| 6. |
- Baghaei Nejad, Majid, et al.
(author)
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A novel passive tag with asymmetric wireless link for RFID and WSN applications
- 2007
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In: 2007 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS. - 9781424409204 ; , s. 1593-1596
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Conference paper (peer-reviewed)abstract
- In this paper, we present a radio-powered module with asymmetric wireless link utilizing ultra wideband radio system for RFID and wireless sensor applications. Our contribution includes using two different standards in uplink and downlink. Such as conventional RFIDs, incoming RF signal transmitted by reader is used to power the internal circuitry and receive the data. However, in upstream link, an IR-UWB transmitter is utilized. Unlike traditional RFID systems, due to great advantages of UWB communication, this tag is very robust to multi-path fading and collision problem and it is more secure against eavesdropping or jamming. The module consists of a power scavenging unit, a RF receiver, an IR-UWB transmitter, digital baseband controller, and an embedded UWB antenna are designed for integration on Liquid-Crystal Polymer (LCP) substrate, using 0.18um CMOS process technology.
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| 7. |
- Baghaei Nejad, Majid, et al.
(author)
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A remote-powered RFID tag with 10Mb/s UWB Uplink and -18.5dBm sensitivity UHF downlink in 0.18μm CMOS
- 2009
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In: Digest of technical papers / IEEE International Solid-State Circuits Conference. - 0193-6530. ; , s. 198-199,199a
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Journal article (peer-reviewed)abstract
- In this work, a 10 Mb/s impulse UWB RFID tag in 0.18 mum CMOS is presented. The tag is remotely powered by a UHF signal with a minimum input RF power as low as 14.1 muW. The primary innovation is to employ two different communication links (UWB and UHF) respectively in the uplink and downlink of the tag. This is because the amount of data or instructions from a reader to a tag is small and as a result a conventional UHF-RFID link at 900MHz can be used as the downlink. The UHF signal also provides remote power to the tag. The uplink requires higher data rates and precise positioning capability therefore an l-UWB transmitter is employed.
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| 8. |
- Baghaei Nejad, Majid, et al.
(author)
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Enabling Ubiquitous Wireless Sensing by a Novel RFID-Based UWB Module
- 2007
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In: The First International EURASIP Workshop on RFID Technology, RFID 2007, 24-25 September 2007, Vienna, Austria.
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Conference paper (other academic/artistic)abstract
- In this paper, we present a novel passive CMOS module which uses two different standards in uplink and downlink. It can be used in many applications such as Radio Frequency Identification (RFID), and ubiquitous wireless sensing. Such as conventional RFID systems, the module captures power supply from received RF signal transmitted by a reader and extracts data and clock by using an envelope detector and PIE encoder. However, in uplink instead of back scattering, an Impulse-UWB transmitter is used to improve the system performance and throughput. The UWB communication offers several advantages to the system. A new communication protocol is proposed for the system based on slotted-ALOHA anti-collision algorithm. The module consisting of a power management unit, an RF narrowband receiver, a clock management unit, an IR-UWB transmitter, and a digital baseband are designed in 0.18 CMOS process.
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| 9. |
- Bao, D., et al.
(author)
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A smart catheter system for minimally invasive brain monitoring
- 2015
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In: Proceedings of the International Conference on Biomedical Electronics and Devices. - : SciTePress. - 9789897580710 ; , s. 198-203
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Conference paper (peer-reviewed)abstract
- This paper demonstrates a smart catheter system with intracranial pressure (ICP) and temperature sensing capability which is designed for real-time monitoring in traumatic brain injury (TBI) therapy. It uses a single flexible catheter with a 1 mm (3 Fr) diameter that integrates electrodes and sophisticated silicon chip on flexible substrates, enabling multimodality monitoring of physiological signals. A micro-electromechanical-system (MEMS) catheter pressure sensor is mounted on the distal end. It can be used for detecting both pressure and temperature by different switch configurations, which minimizes the size of catheter and reduces the cost. The interconnects (signalling conductors) are printed on a bio-compatible flexible substrate, and the sensor is interfaced with an embedded electronic system at the far-end. The electronic system consists of analog front end with analog-to-digital converter (ADC), a microcontroller, and data interface to the hospital infrastructure with a graphical user interface (GUI). The overall smart catheter system achieves a pressure sensing root mean square error (RMSE) of ±1.5 mmHg measured from 20 mmHg to 300 mmHg above 1 atm and a temperature sensing RMSE of ±0.08°C measured from 32°C to 42°C. The sampling rate can be up to 10S/s. The in vivo performance is demonstrated in laboratory animals.
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| 10. |
- Bao, Dongxuan, et al.
(author)
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A Wirelessly Powered UWB RFID Sensor Tag With Time-Domain Analog-to-Information Interface
- 2018
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In: IEEE Journal of Solid-State Circuits. - : IEEE. - 0018-9200 .- 1558-173X. ; 53:8, s. 2227-2239
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Journal article (peer-reviewed)abstract
- This paper presents a wirelessly powered radio frequency identification sensor tag with an analog-to-information interface. A time-domain interface, incorporating an ultra-lowpower impulse radio ultra-wideband (IR-UWB) transmitter (TX), is employed. The analog signal from the sensor is compared with a triangular waveform, resulting in a pulse-position modulation signal to trigger UWB pulses. Thanks to the high time-resolution IR-UWB radio, time intervals of the impulses can be used to represent the original input value, which is measured remotely on the reader side by a time-of-arrival estimator. This approach not only eliminates the analog-to-digital converter (ADC) but also significantly reduces the number of bits to be transmitted for power saving. The proposed tag is fabricated in a 0.18-mu m CMOS process with an active area of 2.5 mm(2). The measurement results demonstrate that a 300-kS/s sampling rate with a 6.7-bit effective number of bits (ENOB) is obtained via a UWB receiver with a sensitivity of -93 dBm and an integration window of 10 ns. The ENOB is improved to 7.3 bits when the integration window is reduced to 2 ns. The tag can be powered up by a -18-dBm UHF input signal. The power consumption of the proposed tag is 41.5 mu W yielding a 1.3-pJ/conv.step figure of merit, offering 9x and 67x improvements compared with the state of the art based on an ADC and a backscattering TX, and the tag based on an ADC and a narrowband TX, respectively.
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