Transmission Rate Research Articles

Transmission characterization of atmospheric laser communication based on an all-optical wavelength converter

We demonstrate a free-space optical (FSO) communication scheme based on an all-optical wavelength converter (AOWC). An all-optical wavelength converter is constructed based on the four-wave mixing (FWM) effect, and information replication is achieved by adjusting the pump power and wavelength spacing to convert the light. The feasibility and stability of each channel in a strong turbulent channel are verified through an eye diagram and bit error rate testing, with a total transmission rate of 30 Gb/s. It has been proven that improving conversion efficiency helps to reduce the bit error rate of transmitted signals. This article presents an experimental analysis of free-space information transmission based on AOWC for the first time, providing a reference for establishing high-speed multiplexing communication.

Performance evaluation of the congestion severity aware rate regulation (CSRR) algorithm in wireless body area networks

SummaryWireless body area network (WBAN) is a potential low‐cost technology for privacy‐sensitive telemedicine and e‐health monitoring and services. However, it faces limited protocol and physical resource support challenges, which can result in packet transfer difficulties. In particular, WBAN requires an emergency‐aware technology that ensures a promising quality of service (QoS). One significant issue affecting QoS and energy efficiency in WBAN is congestion. Effective congestion control techniques are essential for achieving proper load balancing. To address these challenges, we propose a congestion severity aware rate control (CSRR) algorithm that enhances packet transmission rate by reducing packet losses and retransmissions. The CSRR algorithm incorporates a fuzzy controller to predict congestion rates based on runtime metrics. To regulate congestion window growth in different algorithm phases, we introduce sequences such as the Fibonacci retracement sequence, knight's move sequence, and the binary logarithm of the primorial sequence to regulate congestion window growth in the different phases of the proposed algorithm. We mathematically analyze the proposed CSRR algorithm using a Markov model. The simulation results demonstrate the superiority of our algorithm compared to existing approaches. Specifically, our algorithm achieves significant optimizations in terms of throughput (52.92%), packet loss (38.11%), delay (37.23%), and remaining energy (36.86%) when compared to existing algorithms.

Enhancing the porosity of chitosan sponges with CBD by adding antimicrobial violacein

Given the growing interest in non-toxic materials with good anti-inflammatory and antimicrobial mechanical properties, this work focuses on preparing chitosan sponges with violacein and cannabis oil crosslinked with dialdehyde chitosan. The sponge was tested for its physicochemical and biological properties, presenting a high swelling rate, good thermal stability, and satisfactory mechanical properties. The obtained sponge's water vapor transmission rate was 2101 g/m2/day and is within the recommended values for ideal wound dressings. Notably, adding violacein favorably affected the material's porosity, which is essential for dressing materials. In addition, studies have shown that the designed material interacts with human serum albumin and exhibits good antioxidant and anti-inflammatory properties. The antibacterial properties of the prepared biomaterial were assessed using the Microtox test against A. fisherii (Gram-negative bacterium) and S. aureus (Gram-positive bacterium). The investigated material provides potential therapeutic benefits due to the synergistic action of chitosan, violacein, and cannabis oil so that it could be used as a dressing material. The natural origin of the substances could provide an attractive and sustainable alternative to traditional commercially available dressings.

Chemically reactive and mixed convective hybrid nanofluid flow between two parallel rotating disks with Joule heating: A thermal computational study

An electrically conducting and magnetically influenced three-dimensional flow of modified nanofluid between two rotating disks is investigated in this study. Nanometer-size particles of two distinct materials (Al2O3, Ag) suspended in water in the hybrid nanofluid are considered. The Joule heating effects, mixed convection, chemical factor, and exponential heating are considered in this study. The physical problem under these assumptions is transformed into a system of equations. To convert partial differential equations (PDEs) into systems of ordinary differential equations (ODEs), the suitable similarity variables are introduced. The reduced system is numerically solved using bvp4c, a well-known higher-order algorithm. The effects of significant variables on the profiles of velocity, temperature, and concentration are depicted graphically. We have chosen the pertinent parameters in the specific intervals; [Formula: see text][Formula: see text][Formula: see text][Formula: see text][Formula: see text], [Formula: see text][Formula: see text][Formula: see text] and [Formula: see text]. The interactions between a number of significant factors, including skin friction and Nusselt and Sherwood numbers at the higher and lower disks, are shown in tables. The results demonstrate that the local skin fraction decreases as the mixed convection factor is increased, which physically increases the heat transmission rate between the two discs. Furthermore, as the magnetic field and radiation number rise, the rate of heat transfer at the lower and top discs decreases. The numerical results in the form of a table are compared with the available literature, and our results beat the previously published work. The results described here are desirable choices for thermal uses such as automotive cooling systems, solar thermal systems, engineering, medical areas, heat sinks, or current energy storage since they have demonstrated higher thermal characteristics and stability than simple nanofluids (NFs). In Table 6, a comparative numerical study is presented for the various of state variables with the available literature, where the present study is validated.

Assessing Marginal Effects of Non-Pharmaceutical Interventions on the Transmission of SARS-CoV-2 across Africa: A Hybrid Modeling Study.

Since 2019, a new strain of coronavirus has challenged global health systems. Due its fragile healthcare systems, Africa was predicted to be the most affected continent. However, past experiences of African countries with epidemics and other factors, including actions taken by governments, have contributed to reducing the spread of SARS-CoV-2. This study aims to assess the marginal impact of non-pharmaceutical interventions in fifteen African countries during the pre-vaccination period. To describe the transmission dynamics and control of SARS-CoV-2 spread, an extended time-dependent SEIR model was used. The transmission rate of each infectious stage was obtained using a logistic model with NPI intensity as a covariate. The results revealed that the effects of NPIs varied between countries. Overall, restrictive measures related to assembly had, in most countries, the largest reducing effects on the pre-symptomatic and mild transmission, while the transmission by severe individuals is influenced by privacy measures (more than 10%). Countries should develop efficient alternatives to assembly restrictions to preserve the economic sector. This involves, e.g. training in digital tools and strengthening digital infrastructures.

Bio‐composite using polyhydroxyalkanoates and sustainable nanofillers derived from cellulose nanofibers and its application for an environmentally friendly packaging material

AbstractPolyhydroxyalkanoates (PHA) is a carbon neutral material that contributes to reducing greenhouse gas emissions due to manufactured from biomass and easily degraded by the enzymatic effects of microorganisms in the natural environment. However, PHA exhibits poorer mechanical properties and processability compared with petroleum‐based plastics. This study used cellulose nanofiber (CNF) to improve limit of PHA. Moreover, CNF was silylated to reduce polarity difference with PHA and enhance the dispersibility of nanocellulose at PHA. At a result, the silylation process was successfully performed by Si‐CH3 stretching peaks in Fourier transform infrared spectroscopy spectra and hydrophobicity of TEOS‐MTES‐CNF (TECNF) was confirmed by observed water contact angle (147°). In addition, nanostructure of TECNF was maintained during silylation and drying process through field emission scanning electron microscopy. Moreover, the PHA/TECNF composite showed enhanced processability, and tensile strength was increase almost 37% (0.52 MPa) compared with PHA. Oxygen transmission rates (300 cc/m2۰day) and single lap shear strength (225 kPa) were determined to be at least equivalent or superior to those of commercial packaging materials. Therefore, TECNF could be considered as a reinforcing agent, nucleating agent, and plasticizer in PHA. Also, this composite has possibilities to using as environmentally friendly packaging materials.

A Thermodynamic Study on Information Power in Communication Systems

Modern information theory pioneered by Shannon provides the mathematical foundation of information transmission and compression. However, the physical (and especially the energetic) nature of the information has been elusive. While the processing of information incurs inevitable energy dissipation, it is possible for communication systems to harness information to perform useful work. In this article, we prove that the thermodynamic cost (that is, the entropy production of the communication system) is at least equal to the information transmitted. Based on this result, a model of a communication heat engine is proposed, which can extract work from the heat bath by utilizing the transmission of information. The communication heat engine integrates the manipulation of both energy and information so that both information and power may be transmitted in parallel. The information transmission rate and the information power of the communication heat engine are derived from a pure thermodynamics argument. We find that the information power of the communication heat engine can be increased by increasing the number of communication channels, but the absolute energy efficiency of the heat engine first increases and then decreases after the number of channels of the system exceeds a threshold. The proposed model and definitions provide a new way to think of a classical communication system from a thermodynamic perspective.

Advancing LWIR FSO communication through high-speed multilevel signals and directly modulated quantum cascade lasers

This study investigates the potential of long-wave infrared (LWIR) free-space optical (FSO) transmission using multilevel signals to achieve high spectral efficiency. The FSO transmission system includes a directly modulated-quantum cascade laser (DM-QCL) operating at 9.1 µm and a mercury cadmium telluride (MCT) detector. The laser operated at the temperature settings of 15°C and 20°C. The experiment was conducted over a distance of 1 m and in a lab as a controlled environment. We conduct small-signal characterization of the system, including the DM-QCL chip and MCT detector, evaluating the end-to-end response of both components and all associated electrical elements. For large-signal characterization, we employ a range of modulation formats, including non-return-to-zero on-off keying (NRZ-OOK), 4-level pulse amplitude modulation (PAM4), and 6-level PAM (PAM6), with the objective of optimizing both the bit rate and spectral efficiency of the FSO transmission by applying pre- and post-processing equalization. At 15°C, the studied LWIR FSO system achieves net bitrates of 15 Gbps with an NRZ-OOK signal and 16.9 Gbps with PAM4, both below the 6.25% overhead hard decision-forward error correction (6.25%-OH HD-FEC) limit, and 10 Gbps NRZ-OOK below the 2.7% overhead Reed-Solomon RS(528,514) pre-FEC (KR-FEC limit). At 20°C, we obtained net bitrates of 14.1 Gbps with NRZ-OOK, 16.9 Gbps with PAM4, and 16.4 Gbps with PAM6. Furthermore, we evaluate the BER performance as a function of the decision feedback equalization (DFE) tap number to explore the role of equalization in enhancing signal fidelity and reducing errors in FSO transmission. Our findings accentuate the competitive potential of DM-QCL and MCT detector-based FSO transceivers with digital equalization for the next generation of FSO communication systems.

Water-resistant and barrier properties of poly(vinyl alcohol)/nanocellulose films enhanced by metal ion crosslinking

Polyvinyl alcohol (PVA) is a promising alternative to non-biodegradable flexible packaging materials, and nanocellulose is often used to enhance the properties of PVA films, but the composite films still have poor water resistance and barrier properties. To address this issue, iron ions (Fe3+) were introduced into PVA/cellulose nanofibrils (CNF) films, and Fe3+ formed coordination bonds with carboxyl and hydroxyl groups on the surface of CNF and PVA chains. Therefore, constructing a strong coordination crosslinking network within the film and improving the interfacial interaction between PVA and CNF. The water resistance, mechanical and barrier properties of the crosslinked films were significantly improved. Compared with the un-crosslinked film, the oxygen transmission rate (OTR) was decreased by up to 67 %, and the water swelling ratio was significantly reduced from 1085 % to 352 %. The tensile strength of the film with 1.5 wt% Fe3+ reached 41.93 MPa, which was 62 % higher than that of the un-crosslinked film. Furthermore, the composite film demonstrated good recyclability, almost recovering its original mechanical properties in two recycling tests. This simple and effective method for preparing water resistance and barrier films shows potential applications in flexible packaging areas.

Highly reliable DHR-based polar compilation code communication method

The advent of fifth-generation mobile communication technology, 5G, has raised the bar for data transmission rates, information security, and reliability. Polar codes, the channel coding scheme in the 5G communication standard, encounter issues of singularity, limitations, and passivity in the face of unknown attacks. Therefore, this study introduces a highly reliable DHR-based polar coding communication approach. Drawing parallels between cyber attacks and channel noise, the method incorporates reconfigurable executors, decoding decisions, strategy scheduling, and other mechanisms to enable active defense. The True Relatively Axiom (TRA) is employed to theoretically validate the method’s heterogeneity, redundancy, and dynamics. Comparative simulation experiments with traditional polar decoding algorithms, such as SCL, SC, BP, SCAN, and SSC decoding algorithms, demonstrate that the proposed method not only improves secure transmission efficiency but also guarantees secure and reliable transmission across various attack scenarios. Our code is available at https://github.com/yuluzi/my-code.git.

Novel Frame-Type Seismic Surface Wave Barrier with Ultra-Low-Frequency Bandgaps for Rayleigh Waves

Seismic surface waves carry significant energy that poses a major threat to structures and may trigger damage to buildings. To address this issue, the implementation of periodic barriers around structures has proven effective in attenuating seismic waves and minimizing structural dynamic response. This paper introduces a framework for seismic surface wave barriers designed to generate multiple ultra-low-frequency band gaps. The framework employs the finite-element method to compute the frequency band gap of the barrier, enabling a deeper understanding of the generation mechanism of the frequency band gap based on vibrational modes. Subsequently, the transmission rates of elastic waves through a ten-period barrier were evaluated through frequency–domain analysis. The attentional effects of the barriers were investigated by the time history analysis using site seismic waves. Moreover, the influence of the soil damping and material damping are separately discussed, further enhancing the assessment. The results demonstrate the present barrier can generate low-frequency band gaps and effectively attenuate seismic surface waves. These band gaps cover the primary frequencies of seismic surface waves, showing notable attenuation capabilities. In addition, the soil damping significantly contributes to the attenuation of seismic surface waves, resulting in an attenuation rate of 50%. There is promising potential for the application of this novel isolation technology in seismic engineering practice.

Modeling, analysis, and simulation of tuberculosis

Tuberculosis (TB) is a highly contagious disease caused by Mycobacterium tuberculosis, which has historically resulted in numerous fatalities. The analysis of TB is conducted through mathematical models featuring differential equations that describe the dynamics of epidemic spread, as well as its control and prevention. This paper presents the SEIR[Formula: see text][Formula: see text][Formula: see text]D model of TB. According to this model, the total population is divided into five compartments: susceptible, exposed, infected, recovered, and deceased. This paper evaluates the rates (such as transmission rate, incubation rate, etc.) at which individuals transition from one compartment to another under various scenarios.

Evaluating the Usefulness of Population-Wide COVID-19 Testing in the Omicron Era: Insights from a German Model.

The Omicron variant of SARS-CoV-2, which has become dominant worldwide since late 2021, presents a unique challenge due to its high rate of asymptomatic transmission. This study evaluates the efficacy and value of population-wide testing, including self-testing, in the context of COVID-19, particularly under the Omicron variant, using data from Germany. A decision-analytical model and secondary data was used for assessing the impact of systematic screening and testing for COVID-19. Various scenarios were taken into consideration including seasonal patterns of COVID-19 transmission and the potential for annual waves. The model assessed the clinical benefits of testing against the backdrop of vaccine effectiveness, transmission rates, and the potential to prevent severe clinical events, including death, ICU admission, and long COVID syndrome. The study found that the value of mass testing and self-testing for private use was highly contingent on the transmission rate and the scenario of COVID-19 waves (seasonal vs. continuous). For winter waves, a very high incidence rate was required to justify testing, while for continuous waves, testing could be valuable for those in contact with individuals in their last decade of life. The analysis highlighted the limitations of mass testing when community transmission rates were low and the potential value of testing in high-risk contacts or amidst new outbreaks. The findings suggest that the resumption of testing during winter waves is unlikely to provide significant clinical benefits given the current understanding of Omicron's transmission and immunity waning. This study underscores the need for a nuanced approach to COVID-19 testing policies, considering both the epidemiological context and the practical implications of testing strategies.

Joint optimization of communication and mission performance for multi-UAV collaboration network: A multi-agent reinforcement learning method

In emergency rescue, target search and other mission scenarios with Unmanned Aerial Vehicles (UAVs), the Relay UAVs (RUs) and Mission UAVs (MUs) can collaborate to accomplish tasks in unknown environments. In this paper, we investigate the problem of trajectory planning and power control for the MU and RU collaboration. Firstly, considering the characteristics of multi-hop data transmission between the MU and Ground Control Station, a multi-UAV collaborative coverage model is designed. Meanwhile, a UAV control algorithm named MUTTO is proposed based on multi-agent reinforcement learning. In order to solve the problem of the unknown information about the number and locations of targets, the geographic coverage rate is used to replace the target coverage rate for decision making. Then, the reward functions of two types of UAVs are designed separately for the purpose of better cooperation. By simultaneously planning the trajectory and transmission power of the RU and MU, the mission target coverage rate and network transmission rate are maximized while the energy consumption of the UAV is minimized. Finally, numerical simulations results show that MUTTO can solve the UAV network control problem in an efficient way and has better performance than the benchmark method.

Research on a soft saturation nonlinear SSVEP signal feature extraction algorithm

Brain–computer interfaces (BCIs) based on steady-state visual evoked potentials (SSVEP) have received widespread attention due to their high information transmission rate, high accuracy, and rich instruction set. However, the performance of its identification methods strongly depends on the amount of calibration data for within-subject classification. Some studies use deep learning (DL) algorithms for inter-subject classification, which can reduce the calculation process, but there is still much room for improvement in performance compared with intra-subject classification. To solve these problems, an efficient SSVEP signal recognition deep learning network model e-SSVEPNet based on the soft saturation nonlinear module is proposed in this paper. The soft saturation nonlinear module uses a similar exponential calculation method for output when it is less than zero, improving robustness to noise. Under the conditions of the SSVEP data set, two sliding time window lengths (1 s and 0.5 s), and three training data sizes, this paper evaluates the proposed network model and compares it with other traditional and deep learning model baseline methods. The experimental results of the nonlinear module were classified and compared. A large number of experimental results show that the proposed network has the highest average accuracy of intra-subject classification on the SSVEP data set, improves the performance of SSVEP signal classification and recognition, and has higher decoding accuracy under short signals, so it has huge potential ability to realize high-speed SSVEP-based for BCI.

Design of visual symbol-aided system based on wireless network sensor and embedded system

Abstract In order to solve the problem of the low transmission rate of wireless network sensors (WNSs), this article proposes a WNS visual assistance system based on embedded systems. The system uses WNSs instead of traditional wired sensors, which can achieve synchronous transmission of multi-node data, enabling nodes to work together better, thereby improving the real-time and reliability of the entire system. This article conducts in-depth research on feature extraction algorithms and tests the visual assistance system in the experimental section. The results show that the recognition rate and stability of the visual symbol assistance system implemented using WNSs are higher than those of ordinary systems. In the satisfaction survey, it was found that 87 people were very satisfied with the visual symbol assistance system, accounting for 87%, while only 57 people were very satisfied with the traditional visual symbol assistance system, accounting for 57%. The experimental results show that the system output stability of the design method is good, and the response time and reliability are better.

Reactively Processed Poly(butylene adipate terephthalate) Composite–Based Multilayered Films with Improved Properties for Sustainable Packaging Applications: Structural Characterization and Biodegradation Mechanism

AbstractIn this study, it is attempted to enhance the properties and biodegradability of poly(butylene adipate terephthalate) (PBAT) using nanocomposite technology to meet the demand for sustainable packaging applications. Two nanoclays containing PBAT composites are reactively processed and integrated into the multilayered films. Reactive processing facilitates the dispersion and distribution of nanoclay particles in the PBAT matrix. The multilayered films comprising reactively processed PBAT composites exhibited a 24.5%–31.5% reduction in the oxygen transmission rate and improved dimensional stability and tensile properties. Moreover, the degradability of the multilayered film comprising reactively processed PBAT composites reached 82% in 180 days. In contrast, a neat PBAT film of similar thickness attained only 53% degradation in the same period. The biodegradation mechanism is proposed based on the topology of the disintegrated films studied using scanning electron microscopy, chemical bond vibrations determined by Fourier‐transform infrared spectroscopy, and structural evolution by small‐ and wide‐angle X‐ray scattering (SWAXS). The SWAXS analysis is used to understand the changes in the degree of crystallinity, long‐range periodic order, and crystalline and amorphous layer thickness of the multilayered films before and after degradation. Such multilayered films can find applications where packaging or biomedical devices cannot be recycled.

Moisture barriers used in firefighters' protective clothing: Effect of accelerated hydrothermal aging on their mechanical and barrier performance

AbstractFirefighters' protective clothing rely on moisture barriers to safeguard against liquid ingress while enabling sweat evaporation for comfort and safety. However, these moisture barriers can degrade over time, jeopardizing firefighters' safety. Existing evaluation methods, primarily visual inspection, are inadequate for assessing moisture barrier integrity in service. This study examines the effect of accelerated hydrothermal aging on the tear force, water vapor transmission rate (WVTR), and apparent contact angle in three moisture barrier models used in firefighter protective clothing. The moisture barriers studied varied in composition, structure, and base fabric fiber content. Results revealed that moisture barriers' responses to aging are influenced by factors, such as fabric structure, adhesive configuration, finish, and the presence of additional coatings. The hardening of the adhesive layer between the ePTFE membrane and the base fabric was observed in two of the moisture barriers, leading to a slight tear force reduction. Two of the moisture barriers also experienced crack and pit formation on the membrane side, which affected the WVTR. The water‐repellent finish on the fabric side degraded in one moisture barrier. Understanding these complex behaviors is essential for predicting the long‐term moisture barrier performance and enhancing firefighter safety.

Ultra-short and highly efficient metamaterial Fresnel lens-assisted taper

This paper demonstrates the benefits of leveraging free-space optics concepts in the design of certain integrated photonic components, leading to a footprint reduction without compromising on performance. Specifically, we present ultra-short, highly efficient and fabrication-friendly mode-size converters based on metamaterial Fresnel lens-assisted tapers. This is achieved using a parameterized inverse-design approach, where the metamaterial phase shifters are realized using fabrication-friendly Manhattan geometries, by optimizing the width, length, and position of the phase shifters. This approach overcomes the limitations of the conventional method that uses local periodic approximation, which is not suitable for lenses with a short focal length and high numerical aperture. We also extend the free-space concept of compound lenses and demonstrate a doublet-based taper to further reduce the footprint. The devices are fabricated and experimentally characterized in terms of insertion loss and signal integrity at high data transmission rates, exhibiting high performance. For the singlet, it effectively achieves mode-size conversion from 15 μm to 0.5 μm within a 15 μm distance, leading to ×10 length reduction compared to a linear taper. The insertion loss is under 1 dB over the entire C-band. The doublet achieves the same mode-size reduction within a 10 μm distance, leading to ×15 length reduction compared to a linear taper. The insertion loss is near 1 dB over most of the C-band. In both cases, the signal integrity is maintained for up to 50 Gbit/s.

Facile Preparation of Chitosan/Carnauba Wax Emulsion‐Based Coatings for Hydrophobic and Oleophobic Cellulose‐Based Food Packaging

ABSTRACTStudies have shown that fluoridated reagents for oil and water resistance are harmful to the human bodies and the environment. Consequently, the developments of nontoxic, environmentally friendly, fluorine‐free and degradable materials have received increasing attentions. Here, we introduce a novel method for fabricating a hydrophobic and oleophobic paper‐based packaging material through the application of chitosan/carnauba wax emulsions. These emulsions were prepared via high‐shear homogenization, blending melted carnauba wax with chitosan in acetic acid aqueous solutions. The stable chitosan/carnauba wax emulsion with particle size of 430 nm was prepared at the chitosan concentration of 1.5 wt%, the carnauba wax concentration of 8 wt% and temperature of 85 °C. After 10 g/m2 of chitosan/carnauba wax emulsion was applied to the paper surface, the oil and water resistance of the paper was significantly improved. The experimental results of kit rating value, oil contact angle, Cobb60 value and water contact angle were 9.5 ± 0.6, 86.6 ± 2.1°, 8.90 ± 1.62 g/m2 and 123.5 ± 2.6°, respectively. The application of chitosan/carnauba wax emulsion coating on papers provided a significantly lower water vapour transmission rate (WVTR, 78.45 ± 18.92 g/m2·24 h) and oxygen transmission rate (OTR, 94.26 ± 20.21 g/m2·24 h) as compared to the original paper, which met the needs of strawberry packaging.