Search Results (42)

P92 martensitic heat-resistant steel is widely used in ultra-supercritical (USC) thermal power units due to its excellent creep resistance and high-temperature strength. However, prolonged exposure to high temperatures induces significant microstructural degradation, compromising mechanical properties and operational safety. This study investigates the evolution of microstructure and mechanical properties in P92 steel extracted from main steam pipelines after service durations of 30,000 h, 47,000 h, 56,000 h, 70,000 h, and 93,000 h. Comparative analyses of impact toughness, tensile strength, and creep strength were conducted and advanced characterization of SEM and TEM was used to investigate the microstructural evolution. The results reveal a progressive decline in mechanical properties with increasing service time. Specifically, impact toughness decreased by approximately 66.8%, room-temperature tensile strength reduced by 9.62%, and high-temperature tensile strength at 610 °C declined by 31.6%. Notably, the 10⁵ hour creep rupture strength exhibited a 10.4% decrease compared to as-received material. This decline is attributed to microstructural changes including precipitate coarsening, martensite lath boundary degradation, dislocation reconfiguration, and severe grain coarsening. The coarsening of precipitates weakens their bonding with the matrix, while the widening of martensite laths reduces resistance to crack propagation and dislocation movement, jointly contributing to strength deterioration. Full article

Perfect absorbers operating in the terahertz (THz) band are key enablers for next-generation wireless systems. However, conventional metal–dielectric designs suffer from Ohmic losses and limited reconfigurability. Here, we propose an all-dielectric indium antimonide (InSb) cylindrical pillar metasurface that achieves near-unity absorption at $f_0=1.83$ THz with a high quality factor of $Q=72.3$. Critical coupling between coexisting electric and magnetic dipoles enables perfect impedance matching, while InSb’s low damping minimizes energy loss. The resonance is tunable via temperature and magnetic bias at sensitivities of $S_T\approx 2.8\mathrm{GHz}·{\mathrm{K}}^{-1}$, $S_B^{\mathrm{TE}}\approx -132.7\mathrm{GHz}·{\mathrm{T}}^{-1}$, and $S_B^{\mathrm{TM}}\approx -34.7\mathrm{GHz}·{\mathrm{T}}^{-1}$, respectively, without compromising absorption strength. At zero magnetic bias ($B=0$), the metasurface is polarization-independent under normal incidence; under magnetic bias ($B\ne 0$), it maintains near-unity absorbance for both TE and TM, while the resonance frequency becomes polarization-dependent. Additionally, the 90% absorptance bandwidth ($\Delta f_{A\ge 0.9}$) can be modulated from 8.3 GHz to 3.3 GHz with temperature, or broadened from 8.5 GHz to 14.8 GHz under magnetic bias. This allows gapless suppression of up to 14 consecutive 1 GHz-spaced channels. This standards-agnostic bandwidth metric illustrates dynamic spectral filtering for future THz links and beyond-5G/6G research. Owing to its sharp selectivity, dual-mode tunability, and metal-free construction, the proposed absorber offers a compact and reconfigurable platform for advanced THz filtering applications. Full article

This submission is focused on the implementation of a system that acquires data from various types of sensors and securely stores them after encryption on a chip with a reconfigurable architecture. The system has the unique capability of encrypting the input data with a single secret cryptographic key, which is stored only inside the hardware of the system itself, so the key remains unrecognizable upon completion of the system synthesis for any unauthorized user. Being stored as a part of the whole system architecture, the cryptographic key cannot be attained. It is not stored separately on the system RAM or any other supported memory, making the collected data fully protected. The reported work shows a data acquisition system which measures temperature with a high level of precision, transforms it to degrees Celsius, stores the collected data, and transfers them via serial interface when requested. Before storage, the data are encrypted with a 256-bit key, applying the AES algorithm. The data which are stored in the system memory and sent as UART packets towards the main computer do not include the cryptographic key in the data stream, so it is impossible for it to be retrieved from them. We show the flexibility of such kinds of data acquisition systems for sensing different types of signals, emphasizing secure storage and transferring, including data from meteorological sensors or highly confidential or biometrical data. Full article

This paper proposes a second-order low-pass Butterworth multiple-feedback (MFB) filter with a reconfigurable bandwidth and gain, implemented in a 28 nm CMOS. The filter supports independent tuning of the bandwidth from 10 MHz to 100 MHz and the gain from 0 dB to 19 dB, effectively addressing the challenge of a tightly coupled gain and quality factor in traditional MFB designs. Notably, compared to the widely adopted Tow–Thomas structure, the proposed filter achieves second-order filtering and the same degree of flexibility using only a single operational amplifier (OPA), significantly reducing both the power consumption and area. Additionally, an RC tuning circuit is employed to reduce fluctuations in the RC time constant under process, voltage, and temperature (PVT) variations. To meet the requirements for high linearity and low power consumption in broadband applications, a three-stage push–pull OPA with current re-use feedforward and an RC Miller compensation technique is proposed. With the current re-use feedforward, the OPA’s loop gain at 100 MHz is significantly enhanced from 22.34 dB to 28.75 dB, achieving a 2.14 GHz unity-gain bandwidth. Using this OPA, the filter achieves a 48.2 dBm in-band (IB) OIP3, a 53.4 dBm out-of-band (OOB) OIP3, and a figure of merit (FoM) of 185.5 dBJ⁻¹ at a100 MHz bandwidth while consuming only 3.6 mW from a 1.8 V supply. Full article

With the rapid evolution of 5G wireless communications, millimeter-wave (mmWave) technology has become a crucial enabler for high-speed, low-latency, and large-scale connectivity. As the critical interface for signal transmission, mmWave antennas directly affect system performance, reliability, and application scope. This paper reviews the current state of mmWave antenna technologies in 5G systems, focusing on antenna types, design considerations, and integration strategies. We discuss how the multiple-input multiple-output (MIMO) architectures and advanced beamforming techniques enhance system capacity and link robustness. State-of-the-art integration methods, such as antenna-in-package (AiP) and chip-level integration, are examined for their importance in achieving compact and high-performance mmWave systems. Material selection and fabrication technologies—including low-loss substrates like polytetrafluoroethylene (PTFE), hydrocarbon-based materials, liquid crystal polymer (LCP), and microwave dielectric ceramics, as well as emerging processes such as low-temperature co-fired ceramics (LTCC), 3D printing, and micro-electro-mechanical systems (MEMS)—are also analyzed. Key challenges include propagation path limitations, power consumption and thermal management in highly integrated systems, cost–performance trade-offs for mass production, and interoperability standardization across vendors. Finally, we outline future research directions, including intelligent beam management, reconfigurable antennas, AI-driven designs, and hybrid mmWave–sub-6 GHz systems, highlighting the vital role of mmWave antennas in shaping next-generation wireless networks. Full article

Climate change intensifies the challenge of elevated temperatures in dense urban areas, notably in Seoul, South Korea. This study investigates the effects of land use and urban form on summer air temperatures by leveraging Seoul’s city-wide Smart Seoul Data of Things sensor network. Using spatial regression models and temperature data collected during July and August 2021, the analysis identifies key environmental factors associated with urban heat dynamics. The results show that medium- and high-density residential areas, industrial zones, and roads consistently increase temperatures, while greenery, taller buildings, and greater urban porosity contribute to cooling effects. The findings highlight the need for urban planning strategies that expand green spaces, promote vertical development with attention to ventilation, and reconfigure built environments to enhance thermal comfort. This study provides robust empirical insights and offers evidence-based recommendations for climate-responsive urban planning and policies in Seoul and similar high-density cities worldwide. Full article

This paper presents a Virtualized Computational Radio Frequency Identification (VCRFID) solution that utilizes far-field UHF RF for sensing, computing, and self-powering at the edge. A standard UHF RFID system is asymmetric as it consists of a relatively large, complex “reader”, which acts as an RF transmitter and controller for a number of small simple battery-less “tags”, which work in passive mode as they communicate and harvest RF energy from the reader. Previously proposed Computational RFID (CRFID) solutions enhance the standard RFID tags with microcontrollers and sensors in order to gain enhanced functionality, but they end up requiring a relatively high level of power, and thus ultimately reduced range, which limits their use for many Internet-of-Things (IoT) application scenarios. Our VCRFID solution instead keeps the functionality of the tags minimalistic by only providing a sensor interface to be able to capture desired environmental data (temperature, humidity, vibration, etc.), and then transmit it to the RFID reader, which then performs all the computational load usually carried out by a microcontroller on the tag in prior work. This virtualization of functions enables the design of a circuit without a microcontroller, providing greater flexibility and allowing for wireless reconfiguration of tag functions over RF for a 97% reduction in energy consumption compared to prior energy-harvesting RFID tags with microcontrollers. The target application is Industry 4.0 where our VCRFID solution enables battery-less fine-grain monitoring of vibration and temperature data for pumps and motors for predictive maintenance scenarios. Full article

Vanadium dioxide (VO₂) is a well-known phase-change material that exhibits a thermally driven insulator-to-metal transition (IMT) near 68 °C, leading to significant changes in its electrical and optical properties. This transition is governed by structural modifications in the VO₂ crystal lattice, enabling dynamic control over absorption, reflection, and transmission. Despite its promising tunability, VO₂-based optical absorbers face challenges such as a narrow IMT temperature window, intrinsic optical losses, and fabrication complexities associated with multilayer designs. In this work, we propose and numerically investigate a single-layer VO₂-based optical absorber for the visible spectrum using full-wave electromagnetic simulations. The proposed absorber achieves nearly 95% absorption at 25 °C (insulating phase), which drops below 5% at 80 °C (metallic phase), demonstrating exceptional optical tunability. This behavior is attributed to VO₂’s high refractive index in the insulating state, which enhances resonant light trapping. Unlike conventional multilayer absorbers, our single-layer VO₂ design eliminates structural complexity, simplifying fabrication and reducing material costs. These findings highlight the potential of VO₂-based crystalline materials for tunable and energy-efficient optical absorption, making them suitable for adaptive optics, smart windows, and optical switching applications. The numerical results presented in this study contribute to the ongoing development of crystal-based phase-transition materials for next-generation reconfigurable photonic and optoelectronic devices. Full article

AlN-based bulk acoustic wave (BAW) filters have emerged as crucial components in 5G communication due to their high frequency, wide bandwidth, high power capacity, and compact size. This paper mainly reviews the basic principles and recent research advances of AlN-based BAW resonators, which are the backbone of BAW filters. We begin by summarizing the epitaxial growth of single-crystal, polycrystalline, and doped AlN films, with a focus on single-crystal AlN and ScAlN, which are currently the most popular. The discussion then extends to the structure and fabrication of BAW resonators, including the basic solidly mounted resonator (SMR) and the film bulk acoustic resonator (FBAR). The new Xtended Bulk Acoustic Wave (XBAW) technology is highlighted as an effective method to enhance filter bandwidth. Hybrid SAW/BAW resonators (HSBRs) combine the benefits of BAW and SAW resonators to significantly reduce temperature drift. The paper further explores the application of BAW resonators in ladder and lattice BAW filters, highlighting advancements in their design improvements. The frequency-reconfigurable BAW filter, which broadens the filter’s application range, has garnered substantial attention from researchers. Additionally, optimization algorithms for designing AlN-based BAW filters are outlined to reduce design time and improve efficiency. This work aims to serve as a reference for future research on AlN-based BAW filters and to provide insight for similar device studies. Full article

Lithium-ion batteries (LIBs) are widely used in electric vehicles (EVs) and energy storage systems (ESSs) because of their high energy density, low self-discharge rate, good cycling performance, and environmental friendliness. Nevertheless, with the extensive utilization of LIBs, incidents of fires and explosions resulting from thermal runaway (TR) have become increasingly prevalent. The resolution of safety concerns associated with LIBs and the reduction in operational risks have become pivotal to the operation and control of ESSs. This paper proposes a model for the TR process of LIBs. By simplifying the modeling of TR reactions, it is possible to calculate the starting temperature of the battery self-heating reaction. Subsequently, this paper puts forth an operational reliability evaluation algorithm for a reconfigurable battery energy storage system (BESS). Finally, this paper develops a control algorithm for reliability improvement, with the objective of ensuring safe and stable control of the ESS. Full article

The demand for reconfigurable devices for emerging RF and microwave applications has been growing in recent years, with additive manufacturing and photonic thermal treatment presenting new possibilities to supplement conventional fabrication processes to meet this demand. In this paper, we present the realization and analysis of barium–strontium–titanate-(Ba_0.5Sr_0.5TiO₃)-based ferroelectric variable capacitors (varactors), which are additively deposited on top of conventionally fabricated interdigitated capacitors and enhanced by photonic thermal processing. The ferroelectric solution with suspended BST nanoparticles is deposited on the device using an ambient spray pyrolysis method and is sintered at low temperatures using photonic thermal processing by leveraging the high surface-to-volume ratio of the BST nanoparticles. The deposited film is qualitatively characterized using SEM imaging and XRD measurements, while the varactor devices are quantitatively characterized by using high-frequency RF measurements from 300 MHz to 10 GHz under an applied DC bias voltage ranging from 0 V to 50 V. We observe a maximum tunability of 60.6% at 1 GHz under an applied electric field of 25 kV/mm (25 V/μm). These results show promise for the implementation of photonic thermal processing and additive manufacturing as a means to integrate reconfigurable ferroelectric varactors in flexible electronics or tightly packaged on-chip applications, where a limited thermal budget hinders the conventional thermal processing. Full article

Electrothermal actuators are highly advantageous for microelectromechanical systems (MEMS) due to their capability to generate significant force and large displacements. Despite these benefits, their application in reconfigurable conduction line switches is limited, particularly when employing commercial processes. In DC MEMS switches, electrothermal actuators require electrical insulation between the biasing voltage and the transmission line to prevent interference and maintain the integrity of the switch. This work presents a chevron-type electrothermal actuator utilizing a stack of $\mathrm{S}\mathrm{i}{\mathrm{O}}_2/$ Al thin films on a silicon (Si) structural layer beam to create a DC MEMS switch. The design leverages a thin film Al heater to drive the actuator while the $\mathrm{S}\mathrm{i}{\mathrm{O}}_2$ layer provides electrical insulation, suppressing crosstalk with the Si layer. The electrical contact resistance of a Si-to-Si interface was evaluated by applying a controlled current and measuring the resultant voltage. A low contact resistance of 150 Ω was achieved when an initial contact gap of 2.52 μm was closed using an actuator with an actuation voltage of 1.2 V and a current of 205 mA, with a switching speed of less than 5 ms. Factors such as the contact force, the temperature, and the residual device layer etching angle significantly impact the Si-to-Si contact resistance and the switch’s longevity. The switch withstands a breakdown voltage up to 350 V at its terminal contacts. Thus, it will be robust to self-actuation caused by unwanted voltage contributions, making it suitable for high-voltage and harsh environment applications. Full article

A single-domain nanomagnet, shaped like a thin elliptical disk with small eccentricity, has a double-well potential profile with two degenerate energy minima separated by a small barrier of a few $kT$ (k = Boltzmann constant and T = absolute temperature). The two minima correspond to the magnetization pointing along the two mutually anti-parallel directions along the major axis of the ellipse. At room temperature, the magnetization fluctuates randomly between the two minima, mimicking telegraph noise. This makes the nanomagnet act as a “binary” stochastic neuron (BSN) with the neuronal state encoded in the magnetization orientation. If the nanomagnet is magnetostrictive, then the barrier can be depressed further by applying (electrically generated) uniaxial stress along the ellipse’s major axis, thereby gradually eroding the double-well shape. When the barrier almost vanishes, the magnetization begins to randomly assume any arbitrary orientation (not just along the major axis), making the nanomagnet act as an “analog” stochastic neuron (ASN). The magnetization fluctuation then begins to increasingly resemble white noise. The full width at half maximum (FWHM) of the noise auto-correlation function decreases with increasing stress, as the fluctuation gradually transforms from telegraph noise to white noise. Consistent with this trend, the noise spectral density exhibits a 1/f^β spectrum (at high frequencies) with $\beta$ decreasing from 2.00 to 1.88 with increasing stress. Stress can thus not only reconfigure a BSN to an ASN, which has its own applications, but it can also perform “noise engineering”, i.e., tune the auto-correlation function and power spectral density, having applications in signal processing. Full article

High-temperature tensile tests were developed to explore the flow features of an Al-Zn-Mg-Cu alloy. The fracture characteristics and microstructural evolution mechanisms were thoroughly revealed. The results demonstrated that both intergranular fractures and ductile fractures occurred, which affected the hot tensile fracture mechanism. During high-temperature tensile, the second phase (Al₂CuMg) at the grain boundaries (GBs) promoted the formation and accumulation of dimples. With the continual progression of high-temperature tensile, the aggregation/coarsening of dimples along GBs appear, aggravating the intergranular fracture. The coalescence and coarsen of dimples are reinforced at higher tensile temperatures or lower strain rates. Considering the impact of microstructural evolution and dimple formation/coarsening on tensile stresses, a physical mechanism constitutive (PMC) equation is herein proposed. According to the validation and analysis, the predictive results were in preferable accordance with the testing data, showing the outstanding reconfiguration capability of the PMC model for high-temperature tensile features in Al–Zn–Mg–Cu alloys. Full article

Reconfigurable photonic filters represent cutting-edge technology that enhances the capabilities of space payloads. These advanced devices harness the unique properties of light to deliver superior performance in signal processing, filtering, and frequency selection. They offer broad filtering capabilities, allowing for the selection of specific frequency ranges while significantly reducing Size, Weight, and Power (SWaP). In scenarios where satellite communication channels are crowded with various signals sharing the same bandwidth, reconfigurable photonic filters enable efficient spectrum management and interference mitigation, ensuring reliable signal transmission. Furthermore, reconfigurable photonic filters demonstrate their ability to adapt to the dynamic space environment, withstanding extreme temperatures, radiation exposure, and mechanical stress while maintaining stable and reliable performance. Leveraging the inherent speed of light, these filters enable high-speed signal processing operations, paving the way to various space payload applications, such as agile frequency channelization. This capability allows for the simultaneous processing and analysis of different frequency bands. In this theoretical study, we introduce a fully reconfigurable filter comprising two decoupled ring resonators, each with the same radius. Each resonator can be independently thermally tuned to achieve reconfigurability in both central frequency and bandwidth. The precise reconfiguration of both central frequency and bandwidth is achieved by using the thermo-optic effect along the whole ring resonator path. A stopband rejection of 45 dB, with a reconfigurable bandwidth and central frequency of 20 MHz and 180 MHz, respectively, has been numerically achieved, with a maximum electrical power of 11.50 mW and a reconfiguration time of 9.20 µs, by using the scattering matrix approach, where the elements have been calculated through Finite Element Method-based and Beam Propagation Method-based simulations. This performance makes the proposed device suitable as key building block of RF optical filters, useful in the next-generation telecommunication payload domain. Full article