Effect of carbon allotropes and thickness variation on the EMI shielding properties of PANI/NFO@CNTs and PANI/NFO@RGO ternary composite systems.

The innovative design of thin, multiphase flexible composite systems with good mechanical properties, low density and improved EMI shielding properties at low filler content has become a key area of research. In this work, we report the low temperature synthesis of three-dimensional ternary composites (PANI/NFO@CNTs and PANI/NFO@RGO) by oxidative chemical polymerization of aniline in the presence of two different binary composites, viz. NFO@CNTs and NFO@RGO. Enhanced impedance matching is achieved by varying the ratio of the carbon allotropes (CNTs and RGO) to the ferrite component. The synthesis of NFO, PANI/NFO@CNTs and PANI/NFO@RGO is validated by XRD and FTIR spectroscopy. Field emission scanning electron microscopy (FE-SEM) confirmed the synthesis of core-shell structures of PANI/NFO@CNTs and PANI/NFO@RGO, where the binary composites (NFO@CNTs and NFO@RGO) serve as a core onto which a tubular PANI layer was coated. Shielding effectiveness of 22.36 dB (99.41% attenuation) is exhibited by the ternary composite PANI/NFO@CNTs (8 : 1), while for PANI/NFO@RGO (20 : 1) a total shielding effectiveness of 31 dB equivalent to 99.92% attenuation was observed at a thickness of 2 mm. The ternary composite PANI/NFO@RGO (20 : 1) 4 mm showed a maximum SET of 43 dB corresponding to 99.996% attenuation of incident EM waves. The enhanced EMI shielding properties of the synthesized ternary composite systems are accredited to good impedance matching, effective dielectric and magnetic loss mechanisms and good conductivity, which facilitate multiple reflections and scattering of incident radiation.

Optimizing Wireless Connectivity: A Deep Neural Network-Based Handover Approach for Hybrid LiFi and WiFi Networks.

A Hybrid LiFi and WiFi network (HLWNet) integrates the rapid data transmission capabilities of Light Fidelity (LiFi) with the extensive connectivity provided by Wireless Fidelity (WiFi), resulting in significant benefits for wireless data transmissions in the designated area. However, the challenge of decision-making during the handover process in HLWNet is made more complex due to the specific characteristics of electromagnetic signals' line-of-sight transmission, resulting in a greater level of intricacy compared to previous heterogeneous networks. This research work addresses the problem of handover decisions in the Hybrid LiFi and WiFi networks and treats it as a binary classification problem. Consequently, it proposes a handover method based on a deep neural network (DNN). The comprehensive handover scheme incorporates two sets of neural networks (ANN and DNN) that utilize input factors such as channel quality and the mobility of users to enable informed decisions during handovers. Following training with labeled datasets, the neural-network-based handover approach achieves an accuracy rate exceeding 95%. A comparative analysis of the proposed scheme against the benchmark reveals that the proposed method considerably increases user throughput by approximately 18.58% to 38.5% while reducing the handover rate by approximately 55.21% to 67.15% compared to the benchmark artificial neural network (ANN); moreover, the proposed method demonstrates robustness in the face of variations in user mobility and channel conditions.

A Method for Cheating Indication in Unproctored On-Line Exams.

COVID-19 has disrupted every field of life and education is not immune to it. Student learning and examinations moved on-line on a few weeks notice, which has created a large workload for academics to grade the assessments and manually detect students' dishonesty. In this paper, we propose a method to automatically indicate cheating in unproctored on-line exams, when somebody else other than the legitimate student takes the exam. The method is based on the analysis of the student's on-line traces, which are logged by distance education systems. We work with customized IP geolocation and other data to derive the student's cheating risk score. We apply the method to approx. 3600 students in 22 courses, where the partial or final on-line exams were unproctored. The found cheating risk scores are presented along with examples of indicated cheatings. The method can be used to select students for knowledge re-validation, or to compare student cheating across courses, age groups, countries, and universities. We compared student cheating risk scores between four academic terms, including two terms of university closure due to COVID-19.

LPWAN Key Exchange: A Centralised Lightweight Approach.

The Internet of Things (IoT) is one of the fastest emerging technologies in the industry. It includes diverse applications with different requirements to provide services to users. Secure, low-powered, and long-range transmissions are some of the most vital requirements in developing IoT applications. IoT uses several communication technologies to fulfill transmission requirements. However, Low Powered Wide Area Networks (LPWAN) transmission standards have been gaining attention because of their exceptional low-powered and long-distance transmission capabilities. The features of LPWAN transmission standards make them a perfect candidate for IoT applications. However, the current LPWAN standards lack state-of-the-art security mechanism s because of the limitations of the IoT devices in energy and computational capacity. Most of the LPWAN standards, such as Sigfox, NB-IoT, and Weightless, use static keys for node authentication and encryption. LoRaWAN is the only LPWAN technology providing session key mechanisms for better security. However, the session key mechanism is vulnerable to replay attacks. In this paper, we propose a centralized lightweight session key mechanism for LPWAN standards using the Blom-Yang key agreement (BYka) mechanism. The security of the session key mechanism is tested using the security verification tool Scyther. In addition, an energy consumption model is implemented on the LoRaWAN protocol using the NS3 simulator to verify the energy depletion in a LoRaWAN node because of the proposed session key mechanisms. The proposed session key is also verified on the Mininet-WiFi emulator for its correctness. The analysis demonstrates that the proposed session key mechanism uses a fewer number of transmissions than the existing session key mechanisms in LPWAN and provides mechanisms against replay attacks that are possible in current LPWAN session key schemes.

Cyber-Security Threats and Side-Channel Attacks for Digital Agriculture.

The invention of smart low-power devices and ubiquitous Internet connectivity have facilitated the shift of many labour-intensive jobs into the digital domain. The shortage of skilled workforce and the growing food demand have led the agriculture sector to adapt to the digital transformation. Smart sensors and systems are used to monitor crops, plants, the environment, water, soil moisture, and diseases. The transformation to digital agriculture would improve the quality and quantity of food for the ever-increasing human population. This paper discusses the security threats and vulnerabilities to digital agriculture, which are overlooked in other published articles. It also provides a comprehensive review of the side-channel attacks (SCA) specific to digital agriculture, which have not been explored previously. The paper also discusses the open research challenges and future directions.

Insights into photocatalytic degradation of phthalate esters over MSnO3 perovskites (M = Mg, Ca): Experiments and density functional theory.

In this study, the physicochemical and photocatalytic properties of two kinds of stannate perovskite oxides (MgSnO3 and CaSnO3) were investigated under simulated sunlight, where dimethyl phthalate (DMP) and diethyl phthalate (DEP) were selected as the probe pollutants. The results of photochemical characterization showed that MgSnO3 perovskite exhibited better photocatalytic performance than CaSnO3 perovskite. MgSnO3 perovskite could effectively degrade 75% of DMP and 79% of DEP through pseudo-first-order reaction kinetics, which remained good in pH 3.0 to 9.0. Quenching experiments and electron paramagnetic resonance (EPR) characterization indicated that photogenerated holes (h+), superoxide (O2-), and hydroxyl radicals (OH) worked in the photo-degradation, while O2- played the most important role. Furthermore, intermediates identification and density functional theory (DFT) calculations were used to explore the degradation mechanism. For both DMP and DEP, the reactive oxygen species (ROS, including O2- and OH) were responsible for the hydroxylation of benzene ring and the breaking of the aliphatic chain, while h+ was prone to break the aliphatic chain. This work is expected to provide new insights on the photocatalytic mechanism of stannate perovskites for environmental remediation.

A Comprehensive Open-Source Simulation Framework for LiFi Communication.

Light Fidelity (LiFi) is a new candidate for wireless networking that utilizes the visible light spectrum and exploits the existing lighting infrastructure in the form of light-emitting diodes (LEDs). It provides point-to-point and point-to-multipoint communication on a bidirectional channel at very high data rates. However, the LiFi has small coverage, and its optical gain is closely related to the receiver's directionality vis-à-vis the transmitter, therefore it can experience frequent service outages. To provide reliable coverage, the LiFi is integrated with other networking technologies such as wireless fidelity (WiFi) thus forming a hybrid system. The hybrid LiFi/WiFi system faces many challenges including but not limited to seamless integration with the WiFi, support for mobility, handover management, resource sharing, and load balancing. The existing literature has addressed one or the other aspect of the issues facing LiFi systems. There are limited free source tools available to holistically address these challenges in a scalable manner. To this end, we have developed an open-source simulation framework based on the network simulator 3 (ns-3), which realizes critical aspects of the LiFi wireless network. Our developed ns-3 LiFi framework provides a fully functional AP equipped with the physical layer and medium access control (MAC), a mobility model for the user device, and integration between LiFi and WiFi with a handover facility. Simulation results are produced to demonstrate the mobility and handover capabilities, and the performance gains from the LiFi-WiFi hybrid system in terms of packet delay, throughput, packet drop ratio (PDR), and fairness between users. The source code of the framework is made available for the use of the research community.

A Novel Hybrid Approach Based on Deep CNN Features to Detect Knee Osteoarthritis.

In the recent era, various diseases have severely affected the lifestyle of individuals, especially adults. Among these, bone diseases, including Knee Osteoarthritis (KOA), have a great impact on quality of life. KOA is a knee joint problem mainly produced due to decreased Articular Cartilage between femur and tibia bones, producing severe joint pain, effusion, joint movement constraints and gait anomalies. To address these issues, this study presents a novel KOA detection at early stages using deep learning-based feature extraction and classification. Firstly, the input X-ray images are preprocessed, and then the Region of Interest (ROI) is extracted through segmentation. Secondly, features are extracted from preprocessed X-ray images containing knee joint space width using hybrid feature descriptors such as Convolutional Neural Network (CNN) through Local Binary Patterns (LBP) and CNN using Histogram of oriented gradient (HOG). Low-level features are computed by HOG, while texture features are computed employing the LBP descriptor. Lastly, multi-class classifiers, that is, Support Vector Machine (SVM), Random Forest (RF), and K-Nearest Neighbour (KNN), are used for the classification of KOA according to the Kellgren-Lawrence (KL) system. The Kellgren-Lawrence system consists of Grade I, Grade II, Grade III, and Grade IV. Experimental evaluation is performed on various combinations of the proposed framework. The experimental results show that the HOG features descriptor provides approximately 97% accuracy for the early detection and classification of KOA for all four grades of KL.

Adversarial Attack and Defence through Adversarial Training and Feature Fusion for Diabetic Retinopathy Recognition.

Due to the rapid growth in artificial intelligence (AI) and deep learning (DL) approaches, the security and robustness of the deployed algorithms need to be guaranteed. The security susceptibility of the DL algorithms to adversarial examples has been widely acknowledged. The artificially created examples will lead to different instances negatively identified by the DL models that are humanly considered benign. Practical application in actual physical scenarios with adversarial threats shows their features. Thus, adversarial attacks and defense, including machine learning and its reliability, have drawn growing interest and, in recent years, has been a hot topic of research. We introduce a framework that provides a defensive model against the adversarial speckle-noise attack, the adversarial training, and a feature fusion strategy, which preserves the classification with correct labelling. We evaluate and analyze the adversarial attacks and defenses on the retinal fundus images for the Diabetic Retinopathy recognition problem, which is considered a state-of-the-art endeavor. Results obtained on the retinal fundus images, which are prone to adversarial attacks, are 99% accurate and prove that the proposed defensive model is robust.

Batch interaction of emerging tetracycline contaminant with novel phosphoric acid activated corn straw porous carbon: Adsorption rate and nature of mechanism.

In this work, corn straw (CS) based porous carbon was prepared by one-step phosphoric acid (H3PO4) low temperature activation. The impregnation ratios (H3PO4/CS, g/g) played an important role in the pore development. ACS300-1 engineered at 300 °C and the impregnation ratio of 1.0 showed the maximal specific surface area of 463.89 m2/g with total pore volume of 0.387 cm3/g, attaining a high tetracycline (TC) uptake of 227.3 mg/g. The adsorption of TC onto ACS300-1 was found tolerant with wide pH (2.0-10.0) and high ionic strength (0 - 0.5 M). The adsorption data can be fitted well by the pseudo-second order kinetic model and Langmuir isotherm model. The endothermic and spontaneous properties of the adsorption system was implied by Thermodynamic study. The findings of the current work conclude that one-step H3PO4 activation is a green and promising method for corn straw based porous carbon that may be found with great potentials in antibiotic containing wastewater treatment.

Modelling of Chest Wall Motion for Cardiorespiratory Activity for Radar-Based NCVS Systems.

Chest wall motion can provide information on critical vital signs, including respiration and heartbeat. Mathematical modelling of chest wall motion can reduce an extensive requirement of human testing in the development of many biomedical applications. In this paper, we propose a mathematical model that simulates a chest wall motion due to cardiorespiratory activity. Chest wall motion due to respiration is simulated based on the optimal chemical-mechanical respiratory control-based mechanics. The theory of relaxation oscillation system is applied to model the motion due to cardiac activity. The proposed mathematical chest wall model can be utilized in designing and optimizing different design parameters for radar-based non-contact vital sign (NCVS) systems.

Visible Light Communication: A System Perspective-Overview and Challenges.

Visible light communication (VLC) is a new paradigm that could revolutionise the future of wireless communication. In VLC, information is transmitted through modulating the visible light spectrum (400⁻700 nm) that is used for illumination. Analytical and experimental work has shown the potential of VLC to provide high-speed data communication with the added advantage of improved energy efficiency and communication security/privacy. VLC is still in the early phase of research. There are fewer review articles published on this topic mostly addressing the physical layer research. Unlike other reviews, this article gives a system prespective of VLC along with the survey on existing literature and potential challenges toward the implementation and integration of VLC.

Dengue Fever-Induced Hypokalemic Paralysis in a Pregnant Patient: An Uncommon Presentation of a Common Disease.

Dengue fever is a globally prevalent, viral disease transmitted by Aedes mosquitoes, which is becoming increasingly common and can cause a range of symptoms, including fever, flu-like symptoms, and circulatory failure. Although it is classified as a non-neurotropic virus, research has suggested that dengue fever can also affect the nervous system and lead to conditions such as myositis, Guillain-Barré syndrome, or hypokalemic paralysis. We describe a case study of a young pregnant female with dengue-associated hypokalemic paralysis, who made a full recovery within 48 hours of receiving potassium supplementation. The case underscores the importance of recognizing and treating neurological complications of dengue fever promptly, particularly in areas where the disease is prevalent.

Single and binary adsorption of lead and cadmium ions in aqueous solutions and river water by butylamine functionalized vermiculite: performance and mechanism.

Lead and cadmium are toxic to human, animal, and plant health; they enhance oxidative stress indirectly while simultaneously acting through other toxicodynamic mechanisms. In this study, pristine vermiculite (VER) was functionalized with butylamine (BUT) and a novel organoclay (BUT-VER) adsorbent material was produced for simultaneous removal of Pb(II) and Cd(II) in aquatic medium. The adsorbents were characterized by spectroscopic, microscopic, spectrometric, and potentiometric techniques. The adsorption affecting parameters, including pH, time, initial concentration, temperature, and co-existing cations were investigated and optimized. The kinetic data results were in better agreement with pseudo-second-order (PSO) model (R2 > 0.992). Multiple isotherm models were used to study the adsorption system and results showed that adsorption was monolayer. The BUT-VER showed an improvement in adsorption capacity in a single system (Pb(II): from 134.2 to 160.6 mg g-1) and (Cd(II): from 51.1 to 58.9 mg g-1) while in binary system (Pb(II): from 107.3 to 114.5 mg g-1) and (Cd(II): from 33.7 to 39.7 mg g-1), respectively. Furthermore, BUT-VER was tested in real river water and removed efficiency of >99% was achieved in just 1 h. The dominant mechanisms were electrostatic attraction and complexation. BUT-VER was regenerated for five consecutive cycles and showed >90% removal efficiency. These findings suggest that the proposed inexpensive adsorbent has the potential for practical applications of toxic metals removal from water.

Improved photocatalytic decolorization of reactive black 5 dye through synthesis of graphene quantum dots-nitrogen-doped TiO2.

Graphene quantum dots (GQDs), a new solid-state electron transfer material was anchored to nitrogen-doped TiO2 via sol gel method. The introduction of GQDs effectively extended light absorption of TiO2 from UV to visible region. GQD-N-TiO2 demonstrated lower PL intensity at excitation wavelengths of 320 to 450 nm confirming enhanced exciton lifespan. GQD-N-TiO2-300 revealed higher surface area (191.91m2 g-1), pore diameter (1.94 nm), TEM particle size distribution (4.88 ± 1.26 nm) with lattice spacing of 0.45 nm and bandgap (2.91 eV). In addition, GQDs incorporation shifted XPS spectrum of Ti 2p to lower binding energy level (458.36 eV), while substitution of oxygen sites in TiO2 lattice by carbon were confirmed through deconvolution of C 1 s spectrum. Photocatalytic reaction followed the pseudo first order reaction and continuous reductions in apparent rate constant (Kapp) with incremental increase in RB5 concentration. Langmuir-Hinshelwood model showed surface reaction rate constants KC = 1.95 mg L-1 min-1 and KLH = 0.76 L mg-1. The active species trapping, and mechanism studies indicated the photocatalytic decolorization of RB5 through GQD-N-TiO2 was governed by type II heterojunction. Overall, the photodecolorization reactions were triggered by the formation of holes and reactive oxygen species. The presence of •OH, 1O2, and O2• during the photocatalytic process were confirmed through EPR analysis. The excellent photocatalytic decolorization of the synthesized nanocomposite against RB5 can be ascribed to the presence of GQDs in the TiO2 lattice that acted as excellent electron transporter and photosensitizer. This study provides a basis for using nonmetal, abundant, and benign materials like graphene quantum dots to enhance the TiO2 photocatalytic efficiency, opening new possibilities for environmental applications.

Bentonite binding with mercury(II) ion through promotion of reactive oxygen species derived from manure-based dissolved organic matter.

This study reports the mercury binding by bentonite clay influenced by cattle manure-derived dissolved organic matter (DOM). The DOM (as total organic carbon; TOC) was reacted with bentonite at 5.2 pH to monitor the subsequent uptake of Hg2+ for 5 days. The binding kinetics of Hg2+ to the resulting composite was studied (metal = 350 µM/L, pH 5.2). Bentonite-DOM bound much more Hg2+ than original bentonite and accredited to the establishment of further binding sites. On the other hand, the presence of DOM was found to decrease the Hg2+ binding on the clay surface, specifically, the percent decrease of metal with increasing DOM concentration. Post to binding of DOM with bentonite resulted in increased particle size diameter (~ 33.37- ~ 87.67 nm) by inducing the mineral modification of the pore size distribution, thus increasing the binding sites. The XPS and FTIR results confirm the pronounced physico-chemical features of bentonite-DOM more than that of bentonite. Hydroxyl and oxygen vacancies on the surface were found actively involved in Hg2+ uptake by bentonite-DOM composite. Furthermore, DOM increased the content of Hg2+ binding by ~ 10% (pseudo-second-order qe = 90.9-100.0) through boosting up Fe3+ reduction with the DOM. The quenching experiment revealed that more oxygen functionalities were generated in bentonite-DOM, where hydroxyl was found to be dominant specie for Hg2+ binding. The findings of this study can be used as theoretical reference for mineral metal interaction under inhibitory or facilitating role of DOM, risk assessment, management, and mobilization/immobilization of mercury in organic matter-containing environment.

Synergistic effect of perovskites and nitrogen-doped carbon hybrid materials for improving oxygen reduction reaction.

A fundamental understanding of the electrochemical behavior of hybrid perovskite and nitrogen-doped (N-doped) carbon is essential for the development of perovskite-based electrocatalysts in various sustainable energy device applications. In particular, the selection and modification of suitable carbon support are important for enhancing the oxygen reduction reaction (ORR) of non-platinum group metal electrocatalysts in fuel cells. Herein, we address hybrid materials composed of three representative N-doped carbon supports (BP-2000, Vulcan XC-72 and P-CNF) with valid surface areas and different series of single, double and triple perovskites: Ba0.5Sr0.5Co0.8Fe0.2O3-δ, (Pr0.5Ba0.5)CoO3-δ, and Nd1.5Ba1.5CoFeMnO9-δ (NBCFM), respectively. The combination of NBCFM and N-doped BP-2000 produces a half-wave potential of 0.74 V and a current density of 5.42 mA cm-2 at 0.5 V versus reversible hydrogen electrode, comparable to those of the commercial Pt/C electrocatalyst (0.76 V, 5.21 mA cm-2). Based on physicochemical and electrochemical analyses, we have confirmed a significant improvement in the catalytic performance of low-conductivity perovskite catalyst in the ORR when nitrogen-doped carbon with enhanced electrical conductivity is introduced. Furthermore, it has been observed that nitrogen dopants play active sites, contributing to additional performance enhancement when hybridized with perovskite.

Mutual Coupling Reduction through Defected Ground Structure in Circularly Polarized, Dielectric Resonator-Based MIMO Antennas for Sub-6 GHz 5G Applications.

This paper describes a singly-fed circularly polarized rectangular dielectric resonator antenna (RDRA) for MIMO and 5G Sub 6 GHz applications. Circular polarization was achieved for both ports using a novel-shaped conformal metal strip. To improve the isolation between the radiators, a "S" shaped defective ground plane structure (DGPS) was used. In order to authenticate the estimated findings, a prototype of the suggested radiator was built and tested experimentally. Over the desired band, i.e., 3.57-4.48 GHz, a fractional impedance bandwidth of roughly 36.63 percent (-10 dB as reference) was reached. Parallel axial ratio bandwidth of 28.33 percent is achieved, which is in conjunction with impedance matching bandwidth. Between the ports, isolation of -28 dB is achieved Gain and other far-field parameters are also calculated and found to be within their optimum limits.

Adsorption of lead and antimony in the presence and absence of EDTA by a new vermiculite product with potential recyclability.

A new two-step modification method has been proposed where 1.8% HCl and 3.1% HNO3 were applied to modify the interlayer of vermiculite (VMT). This product was given 90 °C of heat in 30% H2SO4 solution that was used for Pb (II) and Sb (III) adsorption. The EDTA presence on the individual adsorption was assessed. X-ray diffraction revealed that the VMT inter-stratified reflection through acid intercalation within the interlayer decreased the parallel gaps between the atoms, witnessing on the outer-sphere adsorption. The driving force was found electrostatic, which fits well with pseudo-second-order kinetics and Langmuir isotherm. The Pb (II) and Sb (III) uptake followed descending order adsorption with increasing concentration of chelating EDTA. Three consecutive desorption cycles revealed that the prepared adsorbent was suitable that may be regarded as a good candidate for complex wastewaters.

Kaolinite weakens the co-stress of ampicillin and tetracycline on Escherichia coli through multiple pathways.

Ampicillin and tetracycline are common antibiotics and can threaten humans by inducing antibiotic resistance in bacteria. Microorganisms are usually exposed to a mixed antibiotic system in the environment. However, there are few researches on the specific regulatory mechanisms of clay on microorganisms under the stress of complex antibiotics. In this study, tandem mass tag-based coupled with two-dimensional liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) was employed to recognize and quantify changes in protein expression of Escherichia coli (E. coli) after culture for 15 days, with or without kaolinite in the co-stress of ampicillin and tetracycline. The results indicated that kaolinite could activate metabolic pathways of E. coli such as the energy metabolism, the biosynthesis of other secondary metabolites, and the metabolism of cofactors and vitamins. Particularly, the fatty acid degradation pathway has also been promoted, indicating that in the same unfavorable environment, kaolinite might influence the composition of E. coli cell membranes. This might be due to the change in membrane composition that was a kind of adaptive strategy of bacterial evolution. Moreover, kaolinite could promote multidrug efflux system to export the bacterial intracellular toxic substances, making E. coli survive better in an adverse environment. Consequently, this study not only disclosed the regulation of kaolinite on E. coli in a complex antibiotic environment but also provided new insights into the environmental process of antibiotic resistance.