Dynamic Frequency Research Articles

High-Performance Flexible Electronics Fabricated Using a Surface Energy-Directed Assembly Process on Ultrathin Polyimide Substrates.

Solution-based processes are emerging in the fabrication of flexible electronics owing to their cost-effectiveness, low-temperature processing capabilities, and vacuum-free operations. Currently, printing techniques, as the most widely used solution-based processes, suffer from low resolution and poor pattern fidelity. Although surface energy-directed assembly (SEDA) process enables unparalleledresolution and fidelity, multilayer fabrication and applicationon flexible substrates are rarely attempted. Here, a SEDA process is used for fabricating metal oxide thin film transistors (TFTs) on ultrathin and flexible polyimide (PI) substrates with a thickness of ≈35µm. Comprehensive procedures to render PI substrates hydrophobic as well as to homogenize the hydrophobicity of the PI substrates and as-assembled layers are developed. All-solution-processed flexible TFTs are constructed by assembling indium oxide semiconducting channels, indium tin oxide source/drain electrodes, aluminum oxide gate dielectric layers, and indium tin oxide gate electrodes ordinally. The metal oxide TFTs exhibit excellent electrical properties with an average mobility of 22.01 cm2V-1 s-1 and stable operation under mechanical strain. Flexible inverters with a high voltage gain of 78 and a high dynamic operation frequency of up to 1kHz are also constructed, representing new opportunities of the SEDA process for the fabrication of next-generation flexible electronics.

Integrated adaptive communication in multi-agent systems: Dynamic topology, frequency, and content optimization for efficient collaboration

In multi-agent systems (MAS), effective communication is essential for coordination and achieving common goals, especially in complex environments. However, existing communication methods face significant challenges, such as high resource consumption and limited adaptability to dynamic environments. To address these, we propose the integrated adaptive communication network (IACN) built on multi-agent proximal policy optimization (MAPPO), which enhances communication efficiency and adaptability in MAS. IACN dynamically adjusts communication topology using a learnable graph and optimizes content based on task relevance. Additionally, it incorporates an adaptive frequency adjustment mechanism to balance communication demands based on task urgency and environmental changes. Experiments in multi-agent particle environments demonstrate that IACN significantly outperforms existing methods in terms of overall performance, coordination effectiveness, and adaptability.

An Improved PIN Diode Model Design for a Tunable Frequency Selective Absorber

An enhanced PIN diode model designed for a tunable frequency absorber is proposed, enabling continuous and adjustable absorption across the X-band frequency range. This new structure consists of four primary components: a frequency selective surface (FSS) layer, a dielectric substrate, an air spacer layer, and a metal substrate. Unlike previous designs, the PIN diode model introduced here offers significant advancements. It not only allows for the switching between absorption and reflection states but also enables precise tuning within the absorption state itself, providing a higher degree of control over the system’s performance. The unique arrangement of the PIN diodes in this design involves placing them between adjacent units of the structure. This strategic placement eliminates the need for complex and bulky bias networks, which are commonly used in conventional designs. As a result, it also minimizes the electromagnetic interference that often arises from bias lines, thereby improving the overall system efficiency and reliability. The proposed model, therefore, reduces the complexity of the absorbing system while enhancing its performance and tunability. Experimental results obtained through free-space measurements were conducted to validate the proposed design. The results show an excellent agreement with the simulation data, confirming that the improved structure can achieve continuous, tunable absorption with high precision. These findings suggest that the new PIN diode-based model could be a promising solution for a wide range of applications in dynamic frequency management and electromagnetic wave absorption systems.

An optimal workflow scheduling in IoT-fog-cloud system for minimizing time and energy

Today, with the increasing use of the Internet of Things (IoT) in the world, various workflows that need to be stored and processed on the computing platforms. But this issue, causes an increase in costs for computing resources providers, and as a result, system Energy Consumption (EC) is also reduced. Therefore, this paper examines the workflow scheduling problem of IoT devices in the fog-cloud environment, where reducing the EC of the computing system and reducing the MakeSpan Time (MST) of workflows as main objectives, under the constraints of priority, deadline and reliability. Therefore, in order to achieve these objectives, the combination of Aquila and Salp Swarm Algorithms (ASSA) is used to select the best Virtual Machines (VMs) for the execution of workflows. So, in each iteration of ASSA execution, a number of VMs are selected by the ASSA. Then by using the Reducing MakeSpan Time (RMST) technique, the MST of the workflow on selected VMs is reduced, while maintaining reliability and deadline. Then, using VM merging and Dynamic Voltage Frequency Scaling (DVFS) technique on the output from RMST, the static and dynamic EC is reduced, respectively. Experimental results show the effectiveness of the proposed method compared to previous methods.

Investigation on Dynamic and Static Modulus and Creep of Bio-Based Polyurethane-Modified Asphalt Mixture

The superior mechanical qualities of polyurethane have garnered increasing attention for its application in modifying asphalt mixtures. However, polyurethane needs to use polyols to cure, and polyols need to be produced by petroleum refining. As we all know, petroleum is a non-renewable energy source. In order to reduce oil consumption and conform to the trend of a green economy, lignin and chitin were used instead of polyols as curing agents. In this paper, a biological polyurethane-modified asphalt mixture (BPA-16) was designed and compared with a polyurethane-modified asphalt mixture (PA-16) and a matrix asphalt mixture (MA-16). The viscoelastic characteristics of the three asphalt mixtures were evaluated using dynamic modulus, static modulus, and creep tests. The interplay between dynamic and static modulus and frequency is examined, along with the variations in the correlation between dynamic and static modulus. The creep behavior of the mixture was ultimately examined by a uniaxial static load creep test. The findings indicate that the dynamic modulus of BPA-16 exceeds those of PA-16 and MA-16 by 8.7% and 30.4% at 25 Hz and −20 °C, respectively. At 25 Hz and 50 °C, the phase angle of BPA-16 decreases by 26.3% relative to that of MA-16. Lignin and chitin, when utilized as curing agents in place of polyol, can enhance the mechanical stability of asphalt mixtures at low temperatures and diminish their temperature sensitivity. A bio-based polyurethane-modified asphalt mixture can also maintain better elastic properties in a wider temperature range. At −20–20 °C, the dynamic and static moduli of BPA-16, PA-16 and MA-16 are linear, and they can be converted by formula at different frequencies. The failure stages of BPA-16, PA-16, and MA-16 are not observed during the 3600 s creep duration, with BPA-16 exhibiting the least creep strain, indicating that lignin and chitin enhance the resistance to permanent deformation in PU-modified asphalt mixes.

RAD-FS: Remote Timing and Power SCA Security in DVFS-augmented Ultra-Low-Power Embedded Systems

High-performance crypto-engines have become crucial components in modern System-On-Chip (SoC) architectures across platforms, from servers to edge-IoTs’. Alas, their secure operation faces a significant obstacle caused by information-leakage accessed through Side-Channel Analysis (SCA). Adversaries exploit statistical-analysis techniques on measured (e.g.,) power and timing signatures generated during (e.g.,) encryption, extracting secrets. Mathematical countermeasures against such attacks often impose substantial power-performance-area overheads. Dynamic Voltage and Frequency Scaling (DVFS) techniques provide power-efficiency by varying power consumption according to workload; these modulations are called power-states. Unintentionally, DVFS introduces new inherent weaknesses exploitable by malicious actors: power-states leak information in both power and timing side-channels, measurable in software and hardware. We introduce a method to increase side-channel resistance using integrated voltage regulators and DVFS: (1) Pushing known prior-art in the topic to Ultra Low Power (ULP) regime (2) For the first time introducing a mechanism to aid in counteracting the inherent weakness of DVFS in SCA (3) Providing measurements performed on 40nm process ULP PLS15 test-chip down at 580 mV power-supply (4) Offering improved and parameterized resistance to remote -timing vulnerabilities inherent to DVFS. We present various results and perform a detailed analysis while comparing performance and security to prior-art. Importantly, our solution is configurable in terms of security, maintaining degrees-of-freedom for power-optimization of DVFS.

Dynamic Voltage and Frequency Scaling for Intermittent Computing

We present hardware/software techniques to intelligently regulate supply voltage and clock frequency of intermittently-computing devices. These devices rely on ambient energy harvesting to power their operation and small capacitors as energy buffers. Statically setting their clock frequency fails to capture the unique relations these devices expose between capacitor voltage, energy efficiency at a given operating frequency, and the corresponding operating range. Existing dynamic voltage and frequency scaling techniques are also largely inapplicable due to extreme energy scarcity and peculiar hardware features. We introduce two hardware/software co-designs that accommodate the distinct hardware features and function within a constrained energy envelope, offering varied trade-offs and functionalities. Our experimental evaluation combines tests on custom-manufactured hardware and detailed emulation experiments. The data gathered indicate that our approaches result in up to 3.75 × reduced energy consumption and 12 × swifter execution times compared to the considered baselines, all while utilizing smaller capacitors to accomplish identical workloads.

Association of interictal epileptiform discharges and serum concentration of levetiracetam and lamotrigine

BackgroundInterictal epileptiform discharges (IEDs) are an electrographic biomarker of epilepsy. Despite their crucial role in diagnosing epilepsy, heterogeneous findings exist on the mechanisms underlying their occurrence and the effects of anti-seizure medications (ASMs) on IEDs.MethodsWe conducted a study to investigate the association between IED frequency and the serum concentration of two commonly used ASMs, levetiracetam (LEV) and lamotrigine (LTG). We included 56 patients undergoing a continuous video EEG monitoring in our center with tapering of ASM. IED frequency was analyzed using automated and semiautomated methods and serum samples were collected sequentially throughout the stay.ResultsThe cohort consisted of 41 patients (23 female, 18 male), between 19 and 64 years (mean 37.42 years), most of which were diagnosed with focal epilepsy (93%). IED frequency increased after ASM reduction revealing a negative correlation similarly with LEV and LTG serum concentrations (p = 0.0057 and p = 0.0426, respectively).DiscussionNotably, we observed a significant increase in IED frequency following dose reduction or discontinuation of both medications. This effect was reversed after ASM were re-dosed. This may indicate the suppressive properties of LEV and LTG against epileptic seizures. Furthermore, our study highlights the importance of ASM discontinuation, which may be required for capturing IEDs during diagnostic continuous EEG monitoring, and not be fully explained by circadian or ultradian rhythms alone.ConclusionOur findings contribute to the understanding of ASM effects on IED frequency dynamics and suggest seizure suppressive properties of LEV and LTG.

LEC-MiCs: Low-Energy Checkpointing in Mixed-Criticality Multicore Systems

With the advent of multicore platforms in designing Mixed-Criticality Systems (MCSs), simultaneous management of reliability and energy while guaranteeing an acceptable service level for low-criticality tasks is a crucial challenge. To ensure the reliability of the MCSs against transient faults, fault-tolerant techniques are employed which will increase energy consumption. To mitigate the energy overhead, the Dynamic Voltage and Frequency Scaling (DVFS) technique will be exploited. However, this technique might lead to violating the timing constraints of high-criticality tasks. Therefore, this article presents, for the first time, the low-energy checkpointing technique to guarantee the reliability of multiple preemptive periodic mixed-criticality tasks in a multicore platform. In contrast to the previous works in checkpointing technique which consider a specific number of faults that all the tasks in the system should tolerate, in this article, the number of tolerable faults for each execution section of a task and in each voltage and frequency level is determined through proposed formulas to meet the reliability target based on safety standards. Then, our proposed method determines the number of checkpoints and their non-uniform intervals for the normal and overrun sections of each task to reduce energy consumption, respectively. Moreover, the unified demand bound function (DBF) analysis is proposed for analyzing the schedulability of the task set, where each high-criticality task meets its timing and reliability constraints, and low-criticality tasks execute based on their derived guaranteed periods in each operational mode of the system. Experimental results show that our proposed scheme meets the timing and reliability constraints while at the same time, improving the Quality of Service (QoS) of low-criticality tasks and managing energy consumption with an average of 29.49% and 32.78%, respectively.

Numerical investigation of the effect of geometric defects on dynamic frequency responses in body-centered cubic lattice structures

Numerical investigation of the effect of geometric defects on dynamic frequency responses in body-centered cubic lattice structures

High-fidelity and adaptive forward-phase-based vibration sensing using a Wiener filter in DSCM systems under commercial ECLs.

In this Letter, we propose and experimentally validate a high-fidelity and adaptive forward-phase-based vibration sensing using a Wiener filter (WF). In commercial coherent digital subcarrier multiplexing (DSCM) systems under external cavity lasers (ECLs), frequency-domain pilot tones (FPTs) in subcarrier intervals are employed for dynamic frequency offset estimation (FOE), carrier phase estimation (CPE), and polarization demultiplexing. The phase estimated by the CPE module is processed with the WF to achieve high-fidelity extraction of the vibration-induced phase. Compared to traditional bandpass filter (BPF)-based phase extraction, the WF method effectively suppresses sensing background noise caused by laser phase noise, improving sensing signal-to-noise ratio (SSNR). Furthermore, without knowing vibration frequency and waveform information, the WF method can adaptively detect various vibration waveforms, including amplitude-modulated continuous wave (AMCW) and frequency-modulated continuous wave (FMCW). In experiments, for 10 kHz sinusoidal vibration detection, the WF method demonstrated an 8 dB SSNR improvement compared to the BPF method. The experiments further verified that both AMCW and FMCW vibrations can be detected adaptively with the WF method using the same filter parameters as for sinusoidal vibrations.

A single/dual band frequency switchable antenna based on SIW for UAV detection applications

ABSTRACT In this paper, we propose a substrate-integrated waveguide (SIW) antenna with frequency switching capabilities for unmanned aerial vehicle (UAV) detection applications. This antenna features a T-shaped slot on its top surface that excites the quarter-TE110 mode to extend its bandwidth. Based on this configuration, three PIN diodes connect the T-shaped patch to the top metal layer, enabling the antenna to switch frequencies dynamically by adjusting the states of these diodes. Experimental results demonstrate that when the three PIN diodes are in the OFF state, the antenna achieves bandwidths of 12.79% and 0.92% in the X-band and Ku-band, respectively. Conversely, when the diodes are turned ON, the antenna operates in the X-band with a bandwidth of 2.6%. Consequently, this antenna successfully facilitates dynamic frequency switching between the X-band and Ku-band. The maximum gains in these three operating bands are 6.6dBi, 3.5dBi, and 5.4dBi, respectively.

Facile Generation of Cyanoselenocysteine as a Vibrational Label for Measuring Protein Dynamics on Longer Time Scales by 2D IR Spectroscopy.

Two-dimensional infrared (2D IR) spectroscopy is a powerful technique for measuring molecular heterogeneity and dynamics with a high spatiotemporal resolution. The methods can be applied to characterize specific residues of proteins by incorporating frequency-resolved vibrational labels. However, the time scale of dynamics that 2D IR spectroscopy can measure is limited by the vibrational label's excited-state lifetime due to the decay of 2D IR absorption bands. To extend this time scale, vibrational labels with longer lifetimes are sought. An effective approach to inhibiting intramolecular energy relaxation is to isolate the vibration from the rest of the molecule by inserting a heavy atom bridge. Although this strategy has been demonstrated through the generation of functionalized amino acids, a straightforward route to their selective incorporation into proteins is often unclear. A facile approach for the attachment of a cyano group at cysteine to generate a thiocyanate has contributed to its adoption as a vibrational label of proteins. We demonstrate that an analogous route can be used for introducing cyanoselenocysteine to generate a selenocyanate vibrational label containing a heavier bridge atom. We confirm by infrared pump-probe and 2D IR spectroscopy longer vibrational lifetimes of 100-250 ps, depending on the solvent, which enable the collection of 2D IR spectra to measure frequency dynamics on longer time scales.

Adaptive Digital Notch Filter for Enhanced Stability in Grid-Connected Inverter Systems

Grid-connected inverters with LCL filters are crucial components in renewable energy systems, but they face stability challenges due to varying grid impedances and resonant frequencies. This paper presents a novel adaptive digital notch filter designed to enhance the stability of such systems across a wide range of operating conditions. The proposed filter employs a three-step adaptive mechanism: resonance detection, determination of resonant frequency change direction, and dynamic notch frequency adjustment. A comprehensive stability analysis in the z-plane reveals the behavior of the resonant pole under different scenarios, informing the filter's design. The adaptive filter's performance was evaluated through simulations. Results demonstrate significant improvements in system stability compared to conventional fixed-frequency notch filters. In scenarios where the resonant frequency was lower than the initial notch frequency, the adaptive filter prevented current divergence and reduced the line current harmonic magnitude at the resonant frequency by up to 75%. In scenarios where the resonant frequency was higher than the notch frequency, the proposed filter successfully suppressed current oscillations, maintaining stability where conventional filters failed. The adaptive mechanism responded to instability within 2 ms, adjusting the notch frequency to optimal levels within 10 ms. This research contributes to the advancement of grid-connected power electronics, offering a robust solution that can enhance the reliability and efficiency of renewable energy integration by up to 30% under varying grid conditions.

Optimal tuning of multi-stage PID controller for dynamic frequency control of microgrid system under climate change scenarios

Introduction. In recent years, the use of renewable energy has become essential to preserve the climate from pollution and global warming. To utilize renewable energy more effectively, the microgrid system has emerged, which is a combination of renewable energies such as wind and solar power. However, due to sudden and random climate fluctuations, energy deviation and instability problems have arisen. To address this, storage systems and diesel engines have been incorporated. Nevertheless, this approach has led to another issue: frequency deviation in the microgrid system. Therefore, most recent studies have focused on finding ways to reduce frequency deviation. The goal of this work is to study and compare various improvement methods in terms of frequency deviation. Methodology. We first simulated the microgrid system using the PID controller based on the following algorithms: krill herd algorithm (KHA) and cuckoo search algorithm (CSA). In the second phase, we replaced the PID controller with the multi-stage PID controller and optimized its parameters using the KHA and the CSA. In the final phase, we tested the response of the microgrid system to these methods under a range of influencing factors. Results. The results initially showed the superiority of the KHA over the other algorithms in improving the parameters of the PID controller. In the second phase, the results showed a significant advantage of the multi-stage PID controller in terms of speed and stabilization time, as well as in reducing the frequency deviation compared to the PID controller. Practical value. Based on the tests conducted on the microgrid system, we can conclude that the multi-stage PID controller based on the KHA can be relied upon to solve these types of problems within the microgrid system. References 36, tables 4, figures 10.

Statistical inference of collision frequencies from x-ray Thomson scattering spectra

Thomson scattering spectra measure the response of plasma particles to incident radiation. In warm dense matter, which is opaque to visible light, x-ray Thomson scattering (XRTS) enables a detailed probe of the electron distribution and has been used as a diagnostic for electron temperature, density, and plasma ionization. In this work, we examine the sensitivities of inelastic XRTS signatures to modeling details, including the dynamic collision frequency and the electronic density of states. Applying verified Monte Carlo inversion methods to dynamic structure factors obtained from time-dependent density functional theory, we assess the utility of XRTS signals as a way to inform the dynamic collision frequency, especially its direct-current limit, which is directly related to the electrical conductivity.

Low power design for Medipix readout systems

Photon-counting hybrid pixel detector chips, such as those based on the Medipix3RX technology, have been central to advancements in spectral and multi-dimensional imaging at synchrotron facilities. As these facilities continue to improve with ongoing upgrades, there is a growing demand for large-area cameras that not only handle increased X-ray flux performances but also integrate effectively into various scientific setups with minimal power consumption.This work focuses on optimizing the energy efficiency of Medipix3RX readout chips used in the context of large-area X-ray photon-counting detectors. We have introduced several power optimization techniques, including dynamic frequency and voltage scaling, and the incorporation of standby/sleep modes into sensor operation. These methods have significantly reduced power consumption, thereby allowing for simplified cooling systems and enhanced durability without compromising the robustness and reliability of the system.Experimental results demonstrate that applying dynamic voltage and frequency scaling can reduce power consumption by 5%, while the clock gating technique can reduce it by up to 23%. Furthermore, the implementation of a sleep mode during periods of inactivity reduces heat dissipation, improving sensor temperature stability, while also reducing overall energy requirements by up to 40% compared to continuous operation. A detailed characterization of the internal parameters of the Medipix3RX analog front-end has enabled us to identify optimal operating points that balance low power consumption with high performance, which is crucial for maintaining low noise levels and fast count rates in challenging experimental environments.

Passivity‐based event‐triggered frequency control in power system using dynamic pricing

AbstractThe integration of renewable energy resources in modern power systems promotes flexible demand response but poses challenges to power balance and frequency stability due to their intermittent generation. To address this problem, this study deals with the frequency control of power system in the presence of demand responses. The dynamic electricity pricing scheme enabling both demand response participants and suppliers to contribute to the frequency regulation via their own decision‐making process is proposed. The main concern in the controller design is the integration of physical and human systems on the same timescale, encompassing controllers based on frequency dynamics and dynamic pricing. Therefore, event‐triggered conditions are proposed to decrease the communication frequency while ensuring system stability, leveraging the passivity property of the system. Under the proposed event‐triggered conditions, the authors clearly demonstrate the asymptotic stability around the equilibrium point of the entire system. Furthermore, a numerical simulation using a four areas power network system is performed, confirming the effectiveness of the proposed control scheme and the stability of the system.

Wind Power Plant Dispatch for Power Grid Frequency Dynamics Improvement: A Surrogate Model-based Method

Wind Power Plant Dispatch for Power Grid Frequency Dynamics Improvement: A Surrogate Model-based Method

Performance of Ad Hoc Wireless Networks under Coexistence Scenario: A Case Study

Owing to the possibility of interference, signal contention, and performance degradation, coexisting IEEE 802.11 (WiFi) and IEEE 802.15.4 (Zigbee, 6LoWPAN) technologies in the 2.4 GHz ISM band presents considerable issues. More packet loss, delay, and decreased throughput for low-power networks can arise from IEEE 802.11's larger bandwidth, higher transmission power, and higher data rates overpowering IEEE 802.15.4's lower power and narrower bandwidth transmissions. This work explores the main facets of their coexistence, emphasising the effects of interference on performance measures including throughput, latency, and energy efficiency and frequency overlap. Dynamic frequency selection and channel allocation algorithms are only a few of the interference reduction techniques that are examined in the analysis. This research offers valuable insights into the more harmonious coexistence of these two wireless technologies in shared surroundings, enabling dependable operation for low-power IoT networks and high-speed Wi-Fi applications. These insights are gained through simulation and experimental validation.