Transmission Frequency Research Articles

An event‐triggered method to distributed filtering for nonlinear multi‐rate systems with random transmission delays

SummaryIn this article, an event‐triggered recursive filtering problem is studied for a class of nonlinear multi‐rate systems (MRSs) with random transmission delays (RTDs). The RTDs are described by utilizing random variables with a known probability distribution and the Kronecker function. To facilitate further study, the MRS is converted into a single‐rate one by adopting an iteration equation approach. To address the challenge of filter design caused by different measurement sampling periods, a modified prediction method of measurements is given. Moreover, an event‐triggered mechanism (ETM) is introduced to regulate the innovation transmission frequency. The objective of the addressed filtering problem is to design a recursive distributed filtering method for MRSs subject to ETM and RTDs, where a minimum upper bound on the filter error covariance is obtained. Moreover, the filter gain matrix is formulated by resorting to the solutions to matrix difference equations. Besides, the boundedness in the mean‐square sense of the filtering error is analyzed and a sufficient condition is provided. Finally, simulations with comparison experiments are presented to demonstrate the effectiveness of the newly proposed theoretical results.

Perspectives on phononic waveguides for on-chip classical and quantum transduction

Phononic waveguides (PnWGs) are devices with rationally designed periodic structures to manipulate mechanical oscillations and to engineer and control the propagation of acoustic waves, thus allowing for frequency and band selection of wave transmission and routing, promising for both classical and quantum transduction on chip-scale platforms with various constituent materials of interest. They can be incorporated into both electromechanical and optomechanical signal transduction schemes. Here, we present an overview of emerging micro/nanoscale PnWGs and offer perspectives for future. We evaluate the typical structural designs, frequency scaling, and phononic band structures of the PnWGs. Material choices, fabrication techniques, and characterization schemes are discussed based on different PnWG designs. For classical transduction schemes, an all-phononic integrated circuit perspective is proposed. Toward emerging quantum applications, the potential of utilizing PnWGs as universal interfaces and transduction channels has been examined. We envision PnWGs with extraordinary propagation properties, such as nonreciprocity and active tunability, can be realized with unconventional design strategies (e.g., inverse design) and advanced materials (e.g., van der Waals layered crystals), opening opportunities in both classical and quantum signal transduction schemes.

Electrically Reconfigurable Metasurfaces for Frequency Selective Transmission via IPMC Kirigami

AbstractMetasurface with programmable configurations has attracted tremendous attention due to their exotic abilities to manipulate electromagnetic waves. Herein, an electrically reconfigurable metasurface for frequency selective transmission is developed based on ionic polymer–metal composite (IPMC) kirigami. First, low‐voltage driven IPMC actuators with stable actuation performance are realized, and then a thermomechanical equivalent model and a numerical electromagnetic analysis model are proposed for evaluating the deformation of the IPMC actuators and predicting the electromagnetic tunable properties of the IPMC kirigami metasurfaces, respectively. Subsequently, large‐area IPMC kirigami metasurfaces are proposed and produced by using programmable nanosecond laser micro‐processing technique that endows the uniformity of the kirigami units. Finally, the electromagnetic functionalities of these IPMC kirigami metasurfaces are researched and validated by experiments and numerical simulations. Both theoretical and experimental results demonstrate that the electromagnetic transmission frequency of the fabricated IPMC kirigami metasurface with 10 × 10 units can be tuned from 19.3 to 20.8 GHz by the application of a low voltage of 3 V. Compared with the existing reconfigurable metasurfaces, the proposed IPMC kirigami metasurface demonstrates clear advantages in its compact structure, lower driving‐voltage, low‐acoustic noise, and wide working frequency range.

Terahertz Communications for Massive Connectivity and Security in 6G and Beyond Era

Terahertz (THz) communications (THzCom) has experienced a meteoric rise of interest, due to its benefits for ultra-high data rate transmission in the sixth generation (6G) and beyond era. Despite so, the research on exploring the potential of THzCom for other performance targets anticipated by 6G, including massive connectivity and security, is still in its infancy. In this article, we start with briefly describing the unique peculiarities of THz channels, and then discuss theoretical frameworks to facilitate the analysis and design of THz transmission for achieving massive connectivity and security. Then we discuss promising spectrum management strategies, including the exploration of multiple THz transmission windows and frequency reuse with multiplexing and signal processing, to substantially increase the number of supported users and identify to-be-tackled challenges. We further present important research directions based on the principles of physical layer security, such as new spectrum allocation policies and beamforming algorithms, to fight against eavesdropping in THzCom systems, ushering in secure THzCom systems.

Processing of VLF Amplitude Measurements: Deduction of a Quiet Time Seasonal Variation

AbstractThe amplitude of Very Low Frequency (VLF) transmissions propagating from transmitter to receiver between the Earth's surface and the ionospheric D‐region is a useful measurement to detect changes in the ionization within the D‐region ranging from 60 to 90 km. The VLF signal amplitude is disturbed by geomagnetic, solar, and atmospheric phenomena. To be able to identify perturbations in the VLF signal amplitude, we determine its averaged seasonal variation under quiet solar and geomagnetic conditions. Here it is challenging, that long time series of the VLF signal amplitude show significant jumps and outliers, which are caused artificially by technical adjustments/maintenance work. This paper presents a new approach for processing long VLF data time series over multiple years resulting in level 2 data. The new level 2 data enables the consideration of time series with artificial jumps since the jumps are leveled. Moreover, the outliers are removed by a robust and systematic 2‐step outlier filtering. The average seasonal and diurnal variation for different transmitter‐receiver combinations can be computed with the new level 2 data by applying a composite analysis. A subsequently applied polynomial fit obtains the quiet time lines for daytime and nighttime, representing the typical seasonal variation under undisturbed conditions of the VLF signal amplitude for each considered link. The developed quiet time lines may serve as a tool to determine perturbations of the VLF signal amplitude with solar and geomagnetic as well as atmospheric origin. Also, they allow comparison of the VLF signal amplitude variation for different transmitter‐receiver links.

A compact frequency-selective absorber with optical transparency

This article proposes a new method for designing an optical transparent frequency-selective surface absorber using indium tin oxide (ITO) conductive film with different sheet resistances. This novel optical transparent frequency-selective absorber exhibits excellent optical transparency, ensuring a visible light transmittance exceeding 76%. Simultaneously, it exhibits broadband absorption characteristics covering the entire X-Ku band, with an absorption rate exceeding 90%. Due to the simplicity of the design, the overall structure is easily processable, and the desired product can be rapidly fabricated using laser etching equipment without adding any lumped elements in the design. Simulation and experimental results indicate that the S11–10 dB frequency range of the frequency-selective absorber is 7.7–18.4 GHz, with a transmission frequency range below −3 dB between 26.7–29.4 GHz. The findings suggest that this structure holds potential applications in microwave stealth design requiring optical transparency and high-throughput satellite communication scenarios.

Study of the generation of two frequency 16-tupling millimeter wave and transmission over fiber by remodulation with Mach–Zehnder modulators

Study of the generation of two frequency 16-tupling millimeter wave and transmission over fiber by remodulation with Mach–Zehnder modulators

New Issues on Electromagnetic Biocompatibility

The paper presents some aspects on the concept of electromagnetic biocompatibility (EMBC), fully supported by epidemiological studies and in the same time by the latest document of the SCENIHR (an organism of the European Commission), regarding extremely low frequency magnetic fields. Modern life is full of artificially generated electric and magnetic fields. We are always exposed to those electromagnetic fields composed of various frequency components. One of these sources is represented by the frequency of 50Hz, the electric power frequency of commercial power transmission and distribution and of household electric appliances. It can be mentioned also high frequencies near 1GHz for cellular phones, and other intermediate frequencies for various appliances. The authors, adepts of the prudential avoidance policy, present several examples of possible harmful effects determined by extremely low frequency magnetic fields, dedicated to building services engineering in residences and in the industrial environment, along with several methods of mitigating them.

Investigation of chromosomal genetic characteristics and identification of structural variation in the offspring of hexaploid triticale×hexaploid wheat.

Hexaploid triticale is an important genetic resource for genetic improvement of common wheat, which can broaden the genetic basis of wheat. In order to lay a foundation for the subsequent research and utilization of triticale germplasm materials, the chromosomal genetic characteristics of cross and backcross offspring of hexaploid triticale×hexaploid wheat were investigated in the process of transferring rye chromatin from hexaploid triticale to hexaploid wheat. Hybrid and backcross combinations were prepared with hexaploid triticale 16yin171 as the maternal parent and hexaploid wheat Chuanmai62 as the paternal parent. The chromosomes in root tip cells of F1, BC1F1 and BC1F2 plants were traced and identified non-denaturing florescence in situ hybridization (ND-FISH). The results indicated that the backcross setting rate of hybrid F1 was 2.61%. The transmission frequency of 2R chromosome was the highest in BC1F1 plants while the transmissibility of rye chromosome in BC1F2 plant was 6R>4R>2R, and the 5B-7B wheat translocation in BC1F2 plants showed severe segregation. A total of 24 structural variant chromosomes were observed both in BC1F1 and BC1F2 plants, including chromosome fragments, isochromosomes, translocations, and dicentric chromosomes. In addition, the seed length and 1000-grain weight of some BC1F2 plants were better than that of the hexaploid wheat parent Chuanmai 62. Therefore, multiple backcrosses should be adopted as far as possible to make the rapid recovery of group D chromosomes, ensuring the recovery of fertility in offspring, when hexaploid tritriale is used as a bridge to introduce rye genetic material into common wheat. At the same time, the potential application value of chromosomal structural variation materials should be also concerned.

Factors associated with patient-to-healthcare personnel (HCP) and HCP-to-subsequent patient transmission of methicillin-resistant Staphylococcus aureus.

Transient acquisition of methicillin-resistant Staphylococcus aureus (MRSA) on healthcare personnel (HCP) gloves and gowns following patient care has been examined. However, the potential for transmission to the subsequent patient has not been studied. We explored the frequency of MRSA transmission from patient to HCP, and then in separate encounters from contaminated HCP gloves and gowns to a subsequent simulated patient as well as the factors associated with these 2 transmission pathways. We conducted a prospective cohort study with 2 parts. In objective 1, we studied MRSA transmission from random MRSA-positive patients to HCP gloves and gowns after specific routine patient care activities. In objective 2, we simulated subsequent transmission from random HCP gloves and gowns without hand hygiene to the next patient using a manikin proxy. For the first objective, among 98 MRSA-positive patients with 333 randomly selected individual patient-HCP interactions, HCP gloves or gowns were contaminated in 54 interactions (16.2%). In a multivariable analysis, performing endotracheal tube care had the greatest odds of glove or gown contamination (OR, 4.06; 95% CI, 1.3-12.6 relative to physical examination). For the second objective, after 147 simulated HCP-patient interactions, the subsequent transmission of MRSA to the manikin proxy occurred 15 times (10.2%). After caring for a patient with MRSA, contamination of HCP gloves and gown and transmission to subsequent patients following HCP-patient interactions occurs frequently if contact precautions are not used. Proper infection control practices, including the use of gloves and gown, can prevent this potential subsequent transmission.

Modulator Bias Control Based on Bi-PID Algorithm for Optical Time and Frequency Transmission

Modulator Bias Control Based on Bi-PID Algorithm for Optical Time and Frequency Transmission

Torque Converter Dynamic Characterization Using Torque Transmissibility Frequency Response Functions: Locked Clutch Operation

<div>A unique torque converter test setup was used to measure the torque transmissibility frequency response function of four torque converter clutch dampers using a stepped, multi-sine-tone, excitation technique. The four torque converter clutch dampers were modeled using a lumped parameter technique, and the damper parameters of stiffness, damping, and friction were estimated using a manual, iterative parameter estimation process. The final damper parameters were selected such that the natural frequency and damping ratio of the simulated torque transmissibility frequency response functions were within 10% and 20% error, respectively, of the experimental modal parameters. This target was achieved for all but one of the tested dampers. The damper models include stiffness nonlinearities, and a speed-dependent friction torque due to centrifugal loading of the damper springs. Recommendations include further testing to separate the coulomb friction mechanism from the viscous damping mechanism, testing with the torque converter operating in open mode, and tests on a series of customized dampers with centrifugal pendulum absorber hardware.</div>

Evaluation of indicators of railway-induced annoying vibration based on building measurements developed by TOD: a discussion

The main negative impact of the residential buildings located on the cover structure of a Transit Oriented Development (TOD) metro depot is that residents would suffer from the train-induced annoying vibrations. Arguments accordingly arose on the possibility of evaluating indicators controversy for this application that acceleration data was more captured in the past while velocity would be more related to structure born noise. Therefore, this paper provided a relative comparison based on a measurement campaign that both velocity and acceleration sensors were installed together at the same time. The collected vibration accelerations and velocities are analyzed and discussed using the methods of transmission loss, coherence, and time and frequency domain analysis. The results indicated that even there was no difference for identifying the resonance frequency of structure, but the transit mobility and human annoyance evaluation were obviously different by using velocity or acceleration. Attempts to establish a relationship between the two indicators using the calculus method failed because they showed the largest error at the peak frequency at the same vibration level, which would have affected the evaluation results and the judgment on the choice of mitigation measures.

Amplitude and oscillating frequency of chemically reactive flow along inclined gravity-driven surface in the presence of thermal conductivity

The main goal of current research is to elaborate wave oscillations and amplitude of heat mass transfer across gravity-driven surface. The heat and mass transfer through inclined gravity driven shapes is very useful in aeronautical technologies and airspace devices. In low gravitational pressure, the concentrated particles move faster with maximum heating rate. The novelty of present mechanism is to estimate the gravity and primitive modulation of chemically reactive flow of periodic and oscillatory heat and mass transfer across the inclined gravity-driven plate under viscosity and thermal conductivity effects. The viscosity, gravity and conductivity are assumed as temperature dependent. The non-dimensional model is converted into algebraic system using finite difference and primitive approach. The Gaussian elimination technique is used to explore velocity, temperature and concentration profiles for different governing variables. The amplitude of shear stress, oscillatory heat and oscillatory mass transfer is examined numerically and graphically. The oscillatory stokes conditions are used to evaluate oscillatory behavior of physical properties. It is found that the mass concentration increases as viscosity of fluid increases under low gravitational pressure. It is seen that the enhancement in velocity of fluid grows as viscosity of fluid reduces. The increasing amplitude and frequency of heat transmission is drafted at π/6 angle under maximum buoyancy forces. The oscillations in mass and shearing stress enhances as buoyancy force increases under minimum gravity.

Planar piezoelectric metamaterials: Sound transmission and applicable frequency range in oblique incidence

Frequency limit and applicable frequency range of planar piezoelectric metamaterials connected to external circuits have not been well defined in estimating the sound transmission loss. This article extends the classical transfer matrix method for use in evaluating the sound transmission of thin-plate piezoelectric metamaterials in oblique incidence. Using the Kirchhoff thin plate theory, a modified transfer matrix method that takes factors of external circuits into consideration is developed for attenuation and control of acoustic waves. Several vibro-acoustic analytical models are compared, including the Kirchhoff thin plate theory, the Reissner–Mindlin thick plate theory and the theory of wave propagation in elastic solids. These theories are used to determine the dispersion relation, coincidence and transition frequency of thin and thick plate theories in analysing piezoelectric acoustic metamaterials, alongside a validation using the finite element method. Then acoustic properties of piezoelectric plates connected to passive external circuits are studied parametrically with both dimensional and dimensionless variables based on an equivalent Kirchhoff plate approximation. The findings show that external electrical impedance alone can be used to adjust the resonance frequency over a broad range and thereby control sound transmission loss. This provides considerable flexibility in modifying the acoustic properties of the piezoelectric metamaterial in comparison to traditional, fixed-structure metamaterials. The study indicates a straightforward and powerful analytical approach for the optimization of acoustic insulation using thin-plate piezoelectric metamaterials.

Incident detection on urban roads - A case study using synthetic floating car data

Within the scope of this paper we examine incident detection on inner-city roads using floating car data (FCD) under different traffic conditions and data qualities. We used synthetic FCD to analyze incidents under variable conditions, such as different traffic volumes. They are generated from microscopic traffic flow simulations with the software tool PTV Vissim. Automated processing of the synthetic FCD gained from the microsimulation models also makes it possible to analyze different data qualities resulting from the choice of penetration rate and transmission frequency. We investigated the recognizability of the incidents using five laboratory examples, which depict different traffic incidents, and a real inner-city road in Karlsruhe, Germany. Graphical and quantitative evaluations are used for incident detection, whereby violin plots and the proposed incident indicator have the most reliable detection rate. Incident detection decreases significantly if several incidents overlap, the severity of the incidents or the traffic volume is reduced, the data quality decreases, or if there is no current speed information in the data. For additional insights, we recommend considering the different figures created in the graphical analysis alongside the incident indicator used in the quantitative analysis.

A mathematical model for simulating the spread of infectious disease using the Caputo-Fabrizio fractional-order operator

<p>We examined intraspecific infectious rivalry in a dynamic contagious disease model. A non-linear dynamic model that considers multiple individual categories was used to study the transmission of infectious diseases. The combined effect of parameter sensitivities on the model was simulated using system sensitivities. To investigate the dynamic behavior and complexity of the model, the Caputo-Fabrizio (C-F) fractional derivative was utilized. The behavior of the proposed model around the parameters was examined using sensitivity analysis, and fractional solutions included more information than the classical model. Fixed point theory was used to analyze the existence and uniqueness of the solution. The Ulam-Hyers (U-H) criterion was used to examine the stability of the system. A numerical approach based on the C-F fractional operator was utilized to improve comprehension and treatment of the infectious disease model. A more precise and valuable technique for solving the infectious disease model was used in MATLAB numerical simulations to demonstrate. Time series and phase diagrams with different orders and parameters were generated. We aimed to expedite patient recovery while reducing the frequency of disease transmission in the community.</p>

Frequency of Children Diagnosed with Perinatal Hepatitis C, United States, 2018-2020.

We describe hepatitis C testing of 47 (2%) of 2,266 children diagnosed with perinatal hepatitis C who were exposed during 2018-2020 in 7 jurisdictions in the United States. Expected frequency of perinatal transmission is 5.8%, indicating only one third of the cases in this cohort were reported to public health authorities.

Changes in the endemic-epidemic pattern of malaria in Colombia, 1978-2021.

Malaria is a major global public health issue with varying epidemiologies across countries. In Colombia, it is a priority endemic-epidemic event included in the national public health policy. However, evidence demonstrating nationwide variations in the disease behavior is limited. This study aimed to analyze changes in the levels and distribution of endemic-epidemic malaria transmission in the eco-epidemiological regions of Colombia from 1978 to 1999 and 2000 to 2021. We conducted a comprehensive time-series study using official secondary data on malaria-associated morbidity and mortality in Colombia from 1978 to 2021. Temporal-spatial and population variables were analyzed, and the absolute and relative frequency measures of general and regional morbidity and mortality were estimated. We observed an 18% reduction in malaria endemic cases between the two study periods. The frequency and severity of the epidemic transmission of malaria varied less and were comparable across both periods. A shift was observed in the frequency of parasitic infections, with a tendency to match and increase infections by Plasmodium falciparum. The risk of malaria transmission varied significantly among the eco-epidemiological regions during both study periods. This study demonstrated a sustained decrease of 78% in malarial mortality. Although the endemic components of malaria decreased slightly between the two study periods, the epidemic pattern persisted. There were significant variations in the risk of transmission across the different eco-epidemiological regions. These findings underscore the importance of targeted public health interventions in reducing malarial morbidity and mortality rates in Colombia.

Large-Signal Stability Analysis Using Takagi-Sugeno Fuzzy Model Theory for Fractional Frequency Transmission System Under Grid Faults

The rapid development of renewable energy requires transmission technology innovation. Fractional frequency transmission system (FFTS) is a promising solution for large-scale renewable energy transmission, and the stability analysis is essential for engineering application. Especially for the grid faults, these large-signal disturbances are inevitable during operation. Thus, the system-level Takagi-Sugeno fuzzy model of FFTS is proposed considering the system parameters, control strategy of modular multilevel matrix converter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M^{3}C$</tex-math></inline-formula> ) and phase locked loop in this study. Subsequently, the Lyapunov function and the large-signal stability domain of attraction (LS-DOA) are calculated expeditiously based on the proposed fuzzy model. Ultimately, the large-signal stability of FFTS is comprehensively analyzed combining with the different-frequency interaction features under grid fault conditions. Compared with the conventional method, the stability strength and affine angle indexes are proposed for quantitative analysis mathematically. The obtained influence law of the system parameters can guide the parameter optimization of FFTS effectively. The effectiveness of proposed methods is verified by the simulation-based study.