Resilience engineering has consistently argued that safety is more than the absence of failures. Since the first book was published in 2006, several book chapters and papers have demonstrated the ...advantage in going behind 'human error' and beyond the failure concept, just as a number of serious accidents have accentuated the need for it. But there has not yet been a comprehensive method for doing so; the Functional Resonance Analysis Method (FRAM) fulfils that need.
For the first time, the ionic polymer metal composite (IPMC) actuator is integrated with a radio frequency identification (RFID) tag antenna for achieving frequency reconfiguration in the ...ultrahigh-frequency (UHF) band. Here, the IPMC movable flap serves as an actuator that can effectively tune the tag resonant frequency. By applying a two-layer-crenelated structure and employing a surface patterned electrode for restraining back relaxation, the deflection of the IPMC actuator can be significantly improved. The IPMC actuator can move in two directions, enabling two-degree frequency tuning. Numerical and experimental data confirm that the tip displacement of the IPMC actuator can be enhanced up to 266% with the use of the two-layer-crenelated structure. The IPMC actuator allows the resonant frequency of the tag antenna to be tuned back by as much as 35 MHz, after deviating due to placing on an unintended object. UHF RFID application is also performed using a portable commercial RFID reader. Good frequency reconfiguration and broad tuning range, along with far read distances, have been achieved with our tunable UHF RFID tag antenna.
In this article, we consider an indoor simultaneous localization and mapping (SLAM) problem for a mobile robot measuring the phase of the signal backscattered by a set of passive radio ultra high ...frequency identification (ID) tags, deployed in unknown position on the ceiling of the environment. The solution approach is based on the introduction, for each radio frequency identification (RFID) tag observed, of a multihypothesis extended Kalman filter (MHEKF) which, based on the measured phases and on the wheel encoder readings, provides an estimate of the range and of the bearing of the observed tag with respect to the robot. This information is then used in an extended Kalman filter (EKF) solving the SLAM problem. Since an effective range and bearing estimate is available only after some steps, a resilient module is added to the algorithm to evaluate the reliability of the position estimate of each observed tag. As shown through numerical and experimental results, this makes the proposed approach robust with respect to several kinds of unmodeled disturbances, like multipath effects or even the unexpected change of the position of a tag.
In this letter, we report simulation results of streamer propagation and collision that produce electromagnetic radiation in the very high frequency (VHF) and ultra high frequency (UHF) bands. The ...streamers are initiated in overbreakdown field conditions, 1.5Ekand2Ek, respectively, which may be found during the corona flash stage of negative leader stepping processes. We find that while streamer propagation produces stronger VHF radiation, the head‐on collision of streamers dominates UHF, and even higher‐frequency radiation. Analysis of the energy spectral densities obtained from different simulation cases shows that the total length and radii of colliding streamers, as well as the ambient field, are important parameters for the UHF radiation produced by streamer collisions. The larger those parameters are, the stronger UHF radiation produced. Finally, by comparing with the measured spectral magnitude of lightning field in the VHF range, it is found that there are probably 105–107 streamers involved during the lightning corona flash stage.
Plain Language Summary
Despite being a familiar phenomenon, the physics of lightning initiation and propagation is not well understood. An effective approach to study lightning is to observe their radio frequency (RF) signals, which is especially critical for understanding the lightning activities inside thunderstorms, because clouds are opaque for other signals. The RF signals with frequencies above about 10 MHz are commonly used to map/image lightning development. They are believed to be produced by the physical process electrically breaking down virgin air. Previous work has shown that electrical breakdown processes known as streamers, which are the precursors of lightning, can produce RF radiation below hundreds of megahertz. Our study investigates a physical process that enables lightning to produce RF radiation above hundreds of megahertz. We find that collisions between streamers can generate rapid increases of electrical current to produce RF emissions extending to tens of gigahertz. The results will be helpful for understanding and interpreting RF observations/measurements of lightning and will generate impact in the field of atmospheric and space electricity.
Key Points
Colliding streamers can produce electromagnetic radiation in the UHF, SHF, and even higher‐frequency range
Propagating streamers produce insignificant electromagnetic radiation beyond the VHF range
Under otherwise the same conditions, longer and larger streamers in higher ambient field produce stronger VHF and UHF radiation
Microwave split ring resonators (SRRs) are limited in modern designs to give a fixed resonant response based on their dimensions and material makeup. By designing an adjustable liquid metal component ...integrated in a highly coupled modified SRR, a frequency-tunable resonator structure was developed. The liquid metal integrated resonators were simulated to show that by varying the amount of liquid metal introduced to the system, the resonant frequency was continuously adjusted from 3.4 to 2.3 GHz, with a consistent resonant amplitude and quality factor of −22 dB and 75, respectively. The frequency-configurable sensor was fabricated with simple 3-D printing methods and inexpensive materials to control the liquid metal, resulting in a compact device with frequency tunability from 3.4 to 2.35 GHz. The fabricated resonator sensor had a resonant amplitude and quality factor of −24 dB and 70, respectively - with less than 10% variation along the entire frequency tuning process. Experimental analysis of the sensor showed continuous variation as the volume of liquid metal was increased within the straight channel, with a consistent resonant frequency sensitivity to liquid metal of 375 MHz/cm. The device enables measurement of a microwave frequency spectrum with user-desired resolution.
We found offshore shallow low‐frequency tremor in the northern Japan Trench subduction zone, using records from the Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench. ...The tremor aligned with a narrow zone, which follows the 10‐ to 25‐km depth contours of the plate interface and occurred in two distinct areas, off Tokachi and Sanriku, separated by a gap. In the 1.75 years examined, two episodes lasting for a few weeks were identified off Tokachi. During these episodes, tremor occurred concurrently with swarms of very low frequency earthquakes and migrated laterally about 120 km along the trench strike. In contrast, tremor off Sanriku lasted shorter (half a day to 5 days) and repeated at shorter intervals (1–4 months). The variation in tremor behavior such as duration, recurrence, migration, and the association with very low frequency earthquakes suggests along‐strike heterogeneities in frictional properties at the shallow plate interface.
Plain Language Summary
Low‐frequency tremor has been widely recognized at many subduction zones yet has not been directly measured in the Japan Trench subduction zone in northeastern Japan. Using a newly installed seafloor seismic network, we report for the first time observations of tremor occurring at the shallow subduction plate interface in the northern Japan Trench subduction zone. The observed tremor, localized in the regions off Tokachi and Sanriku, were synchronized in space and time with very low frequency earthquakes and moved across the region during active periods. Tremor off the Tokachi and Sanriku regions had different characteristics, including duration and recurrence time. This difference is likely caused by different frictional properties at the plate interface near the trench.
Key Points
We identified offshore shallow low‐frequency tremor parallel to the trench strike in the northern Japan Trench subduction zone using S‐net
Tremor occurred in the two clusters separated by a gap and coincided with very low frequency earthquakes
Spatial differences in tremor behavior imply lateral heterogeneities in frictional properties at the shallow plate interface
A novel receiver structure for the reception of linearly frequency modulated (LFM) chirps carrying additional narrowband (phase) modulation is proposed. A linear relation between the time delay and ...the beat frequency shift of the target response in stretch processing is exploited to estimate the target range via correlation of the received signal with the replica in a Fractional Fourier Transform (FrFT) domain. According to numerical simulations, the proposed FrFT receiver demonstrates improved performance and computational efficiency over the state-of-the-art solutions for the moderate-to-large bandwidth of the information-carrying modulation. The receiver was integrated into the waveform-agile radar polarimetric agile radar in S band (PARSAX) and its performance has also been verified experimentally.
This book includes a survey of all RFID fundamentals and practices in the first part of the book while the second part focuses on UHF passive technology. This coverage of UHF technology and its ...components including tags, readers, and antennas is essential to commercial implementation in supply chain logistics and security. Readers of this book should have an electrical engineering background, but have not yet dealt with RFID. To this end, the author is very careful to illustrate all concepts and detail his explanations meticulously. In this way, he will bring the reader along organically showing him/her what to expect, develop, and use while implementing an RFID system.
In this article, a polarization-independent reflective cross-polarization converter with an in-band notch and high frequency selectivity is proposed in S-band using guided wave inspired metasurface. ...The equivalent circuit mode was also proposed to analysis and demonstrate the design. The metasurface unit cell is composed of three patterned metallic layers, and each layer of the structure is reflection-symmetrical to ensure polarization independence. A folded L-shaped microstrip line on the bottom layer is designed for third-order polarization conversion. Then, in order to eliminate the in-band interference, a U-shaped slot is added to the ground, which introduces an in-band notch and two polarization conversion zeros on each side of the cross-polarized band. The two zeros for polarization conversion out of the cross-polarized band are at 2.039 GHz and 3.853 GHz, respectively. The designed notch frequency is at 2.834 GHz, and the frequency selectivity is 205.93 dB/GHz and 166.96 dB/GHz at lower and upper side of the notch frequency, respectively. The PCR of the cross-polarized bands reaches 99.99% at 2.617 GHz at the lower side and 99.97% at 3.247 GHz at upper side of the notch frequency, respectively. The insertion loss in the cross-polarized band is about 1dB.
This paper presents an effective way to design an RFID tag antenna to operate at three different frequencies by incorporating a switching technique. PIN diode has been used to switch the RF frequency ...because of its good efficiency and simplicity. The conventional dipole-based RFID tag has been improvised with added co-planar ground and PIN diode. The layout of the antenna is designed with a size of 0.083 λ0 × 0.094 λ0 at UHF (80-960) MHz, where λ0 is the free-space wavelength corresponding to the mid-point of the targeted UHF range. The RFID microchip is connected to the modified ground and dipole structures. Bending and meandering techniques on the dipole length help to match the complex chip impedance with the dipole impedance. Additionally, it scales down the total structure of the antenna. Two PIN diodes are placed along the dipole length at appropriate distances with proper biasing. The ON-OFF switching states of the PIN diodes enable the RFID tag antenna to switch over the frequency ranges (840-845) MHz (India), 902-928 MHz (North America), and 950-955 MHz (Japan).
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